Autophagic and Proteasomal Mediated Removal of Mutant Androgen Receptor in Muscle Models of SBMA

This is way over my head. I need someone to simplify it. Follow the link below to the entire - very long - article in Frontiers in Endocrinology.

Autophagic and Proteasomal Mediated Removal of Mutant Androgen Receptor in Muscle Models of Spinal and Bulbar Muscular Atrophy

Spinal and bulbar muscular atrophy (SBMA) is an X-linked motoneuron disease (MND) caused by a mutant androgen receptor (AR) containing an elongated polyglutamine (polyQ) tract. ARpolyQ toxicity is triggered by androgenic AR ligands, which induce aberrant conformations (misfolding) of the ARpolyQ protein that aggregates. Misfolded proteins perturb the protein quality control (PQC) system leading to cell dysfunction and death. Spinal cord motoneurons, dorsal root ganglia neurons and skeletal muscle cells are affected by ARpolyQ toxicity. Here, we found that, in stabilized skeletal myoblasts (s-myoblasts), ARpolyQ formed testosterone-inducible aggregates resistant to NP-40 solubilization; these aggregates did not affect s-myoblasts survival or viability. Both wild type AR and ARpolyQ were processed via proteasome, but ARpolyQ triggered (and it was also cleared via) autophagy. ARpolyQ reduced two pro-autophagic proteins expression (BAG3 and VCP), leading to decreased autophagic response in ARpolyQ s-myoblasts. Overexpression of two components of the chaperone assisted selective autophagy (CASA) complex (BAG3 and HSPB8), enhanced ARpolyQ clearance, while the treatment with the mTOR independent autophagy activator trehalose induced complete ARpolyQ degradation. Thus, trehalose has beneficial effects in SBMA skeletal muscle models even when autophagy is impaired, possibly by stimulating CASA to assist the removal of ARpolyQ misfolded species/aggregates.

Researchers identify a possible therapeutic target for Kennedy's disease and prostate cancer

https://www.eurekalert.org/pub_releases/2019-08/ifri-ria080819.php

NEWS RELEASE 8-AUG-2019

Researchers identify a possible therapeutic target for Kennedy's disease and prostate cancer

INSTITUTE FOR RESEARCH IN BIOMEDICINE (IRB BARCELONA)

A study led by scientists at the Institute for Research in Biomedicine (IRB Barcelona) and published in Nature Communicationsproposes chaperone protein Hps70 as an attractive therapeutic target for the treatment of Kennedy's disease--a rare neuromuscular condition--and of castration-resistant prostate cancer.

Kennedy´s disease is caused by a mutation in the androgen receptor. This receptor serves as a sensor of testosterone, detecting the levels of this hormone and activating the genes responsible for male traits. But in patients with this disease, the mutated receptor shows an altered structure, as demonstrated by this lab in a previous study recently published in the same journal, and it forms aggregates that damage muscle cells and causes muscular atrophy or wasting.

Chaperone proteins are one of the mechanisms through which the formation of toxic protein aggregates is prevented. These chaperones bind to other proteins in order to facilitate their correct folding, assembly and transport, as well as regulating their degradation. "But we didn't know the role of these chaperones in the regulation of the activity, cell concentration and solubility of the androgen receptor," says ICREA researcher Xavier Salvatella, head of the Laboratory of Molecular Biophysics at IRB Barcelona.

Using a sophisticated biophysics approach, nuclear magnetic resonance (NMR), and experiments with human cell cultures, the scientists discovered that the chaperones Hsp40 and Hsp70 bind strongly to a region of the androgen receptor that is susceptible to forming toxic aggregates. This interaction between the chaperones and the receptor prevents the formation of these deposits and facilitates their clearance.

To confirm whether the increase in the activity of these chaperones decreases the formation of toxic aggregates and whether these proteins are therefore useful for the treatment of Kennedy`s disease, the scientists performed experiments in mouse models. These experiments were done in collaboration with the labs of Professors Jason E. Gestwicki and Andrew P. Lieberman from the University of California San Francisco and the University of Michigan, respectively.

"The results obtain in mice confirm that compounds that activate Hsp70 lead to a decrease in the formation of the aggregates," says Salvatella. "Therefore the chaperone Hsp70 emerges as a possible therapeutic target for Kennedy's disease," he goes on to say.

The results may also be useful in the search for a treatment for castration-resistant prostate cancer, the most advanced stage of this kind of cancer, which causes 30,000 deaths a year in Europe. In cells resistant to current treatments, the binding site of Hsp40 and Hsp70 in the androgen receptor is not altered, and therefore these chaperones may also serve as a therapeutic target in this disease.

Treatment of Prostate Cancers and Kennedy’s Disease

This is way above my understanding level, but might be of interest to some of you.

Treatment of Prostate Cancers and Kennedy’s Disease by PROTAC-Androgen Receptor Degradation

Summary

Prostate cancer (PCa) is the most common malignancy diagnosed among men in Western countries and the second leading cause of cancer-related deaths, with over three million men in the United States living with the disease. Positive predictor of prostate cancer risk and tumor stage involves the prostate-specific antigen (PSA)-related serine protease kallikrein-related peptidase 4 (KLK4), which is overexpressed in prostate cancer relative to benign tissue. In vitro, KLK4 has been found to promote prostate cancer cell migration, proliferation, and epithelial-to-mesenchymal transition. Despite improvements in external radiotherapy, brachytherapy, and radical prostatectomy treatment, up to 35% of patients with localized or locally advanced PCa may experience disease relapse.

Androgen deprivation therapies (ADTs) such as enzalutamide (an androgen receptor inhibitor) and abiraterone acetate (an inhibitor of androgen biogenesis) are considered to be frontline treatments and have shown benefit to patients with advanced PCa. However, castration-resistant prostate cancer (CRPC) invariably develops, leading to the lethal form known as metastatic castration-resistant PCa (mCRPC), which gives rise to high mortality rate, and no cure is currently available. Treatment targeting androgen receptor (AR) signaling becomes ineffective in advanced prostate cancer with AR gene mutation, amplification, and alternate splicing. Nonetheless, most patients who progress on enzalutamide and abiraterone have rising prostate-specific antigen (PSA) levels, which strongly suggests that these tumors are still dependent on the AR signaling.

Understanding the molecular mechanisms that drive the prostate cancer progression is essential to develop therapies that will attenuate the metastatic growth. As such, several mechanisms have been proposed to account for continued AR signaling such as point mutations in the AR ligand-binding domain (LBD) and expression of AR splice variants (ARVs) that have been shown to mediate resistance to abiraterone and enzalutamide. The ARVs are active even in the absence of ligands and are truncated AR isoforms that lack LBD but retain the DNA-binding domain (DBD) and N terminal domain (NTD). Several signaling pathways activate AR signaling in the absence of ligands in prostate cancer models like IL-6 and HER2. Interestingly, the majority of these pathways are thought to activate AR through its NTD, either by post-translational modifications or by direct interactions. Regardless of the mechanism at play, the continued expression of AR target genes is a major driver in the resistance found in PCa treatment, and new therapies are necessary to treat these cancers.

In the absence of androgens, AR is bound by Heat Shock Protein 90 (Hsp90) in the cytosol, which leads to conformational changes and the release of AR from Hsp90 that exposes the nuclear localization signal (NLS). Hsp90 is the most abundant intracellular protein in mammalian cells and is essential for a wide range of protein assembly, folding, trafficking, and degradation processes. Furthermore, Hsp90 is composed of an N-terminal adenosine triphosphate/adenosine diphosphate (ATP/ADP) binding domain, a middle domain involved in client protein binding, and a C-terminal dimerization domain. The N- and C-termini contain distinct binding sites for ATP and are associated with a specific functional activity. The binding of ATP at the N-terminus provides energy to modulate protein trafficking and folding, whereas nucleotide binding at the C-terminus is linked to allosteric regulation of ATP binding to the N-terminal site. Hsp90 inhibitors exhibit anticancer properties as proteins associated with malignant growth, including growth factors, kinases, and hormone receptors, which are dependent upon the Hsp90 protein folding machinery for their activation and maturation. Consequently, inhibitors of Hsp90 can disrupt multiple signaling cascades simultaneously, which may result in a combinatorial attack on numerous signaling pathways.

Thus, alternate therapeutic strategy, such as proteolysis targeting chimera (PROTAC) has gained momentum with its promise in the discovery and development of completely new types of small-molecule that induces targeted protein degradation. A PROTAC molecule is a heterobifunctional small molecule containing one ligand, which binds to the target protein of interest, and a second ligand for an E3 ligase system that is tethered together by a chemical linker. From the above discussion, AR protein plays a crucial role in CRPC, and AR degraders designed based upon the PROTAC concept could be potentially very effective for the treatment of CRPC. Compounds of this Patent Highlight comprise bifunctional small molecules that recruit endogenous proteins to an E3 ubiquitin ligase such as Von Hippel-Lindau (VHL) E3 ubiquitin ligase, for ubiquitination and subsequent degradation. Thus, these compounds (where ABM is an AR binding moiety, ULM is an E3 ligase binding moiety like VHL E3 ligase binding moiety (VLM), and L is a linker moiety) are modulators of targeted ubiquitination, degraders of androgen receptor (AR), and provide effective treatment or amelioration of a disease condition such as prostate cancer and Kennedy’s Disease. The first targeted protein degrader (Arv-110, an orally bioavailable small molecule AR PROTAC) has been cleared by the FDA for phase I clinical trial for the treatment of advanced prostate cancer (https://prostatecancernewstoday.com/2019/01/30/fda-clears-phase-1-trial-arv-110-advanced-prostate-cancer/).

The structural consequences of the mutation in Kennedy's Disease

The following was published in IRB Barcelona yesterday. It is further research on research performed a few years ago.  https://www.irbbarcelona.org/en/tags/kennedys-disease-0

Researchers at IRB Barcelona discover the structural consequences of the mutation that causes Kennedy disease

The androgen receptor helix of polyglutamine becomes increasingly stable as the number (n) of glutamine amino acid residues increases.

12 JUN 2019

Kennedy’s disease is an untreatable neuromuscular disorder considered a rare disease

A study led by Xavier Salvatella may pave the way for new lines of treatment for Kennedy’s disease

Kennedy’s disease is a rare neuromuscular disease caused by a mutation in the androgen receptor protein. The Laboratory of Molecular Biophysics led by Xavier Salvatella at the Institute for Research in Biomedicine (IRB Barcelona) has recently discovered new key structural features of the androgen receptor induced by the mutation. This finding has been published in the journal Nature Communications and could open up new therapeutic avenues for a family of incurable rare conditions called polyglutamine (polyQ) expansion diseases.

Spinal and bulbar muscular atrophy (SBMA), also known as Kennedy’s disease, is an untreatable neuromuscular disorder that causes a dramatic decrease in patients’ quality of life. It is classified as a rare disease, meaning that it affects less than 5 in 10,000 people. The mutation in the androgen receptor protein causing the disease is an expansion of a repetitive amino acid sequence containing only glutamine residues, called a polyQ tract. Interestingly, the length of this tract determines whether a person develops Kennedy’s disease.

A similar mutation can also be found in other polyQ expansion diseases, the most known of which is Huntington’s disease. Why an expansion of the polyQ tract leads to the development of polyQ expansion diseases in not understood. In the case of Kennedy’s disease, researchers believe that androgen receptor proteins containing a very long polyQ tend to oligomerize. These oligomers then generate toxic protein aggregates inside the cell, thereby impeding its proper functioning.

For a protein to function properly, it must fold into an ordered three-dimensional structure. Up to now, the part of the androgen receptor protein holding the polyQ expansion was thought to be disordered and therefore unable to fold into such a structure. In 2016, Salvatella’s group found that the polyQ tract of the androgen receptor could adopt a helical structure. “This was a very interesting result, as so far these tracts were thought not to adopt any specific structure,” explains Salvatella.

In the current study, the team went one step further and visualized the polyQ tract protein helix via advanced biophysical and computational methods. They now report that this specific region can form well-ordered helices and, crucially, that the polyQ expansion greatly increases the degree of order and stability of these helices. This information furthers our understanding of androgen receptor function.

Study identifies potential drug for treatment of SBMA

In March of last year I mentioned this article:

Study identifies potential drug for treatment of debilitating inherited neurological disease

An excerpt of the article can be found below Dr. Taylor's update.

I wrote Dr. Taylor today and asked for an update on the research. Below is his reply.

We have been working with the group in Vancouver at the University of British Columbia who developed the MEPB compound and have identified analogs that have even better potency and drug properties. UBC owns the rights. My understanding is that UBC is discussing a licensing agreement with a drug company to further develop this – meaning they will run independent preclinical trials in a mouse model using the newer compound, and pending those results will initiate human clinical trials. This typically takes ~ 2years.

The following is an excerpt from the original Medical Press article. To read the entire article follow this link: Potential Drug Treatment. The St. Jude's website also has the article:  Study Identifies PDT

As always, I appreciate Dr. Taylor and his team's support for finding a treatment for Kennedy's Disease.

March 15, 2018

Dr. Paul Taylor of St. Jude Children's Research Hospital ...

"... and his colleagues were led to seek drugs to treat SBMA because of findings from a previous study in his laboratory. The study pinpointed a molecular niche in the mutant androgen receptor protein that appeared to be a key to driving SBMA symptoms. However, that niche did not seem to be essential to the normal function of the androgen receptor. The study started with fruit flies genetically engineered to have the human androgen receptor, giving the scientists a living "test tube" to explore the effects of mutating the receptor.

"This identification of a small patch of this protein that appeared to be functionally important for driving the disease, but is not essential for most androgen receptor functions, gave us a potential drug target," Taylor said.

Pharmaceutical companies have been developing drugs to target this small patch, called the "activator function-2" or "AF2" domain. The companies were testing the drugs as possible treatments for prostate cancer, which also involves the androgen receptor. Taylor obtained a collection of the test drugs to evaluate for use with SBMA.

Using the genetically engineered flies, the researchers identified two drugs—whose long chemical names are abbreviated TA and MEPB—that alleviated SBMA symptoms. Then, using mice, the scientists determined that MEPB more effectively reached target tissues in the brain and spinal cord.

For their trials of TA and MEPB as potential SBMA treatments, the researchers developed a new genetically engineered mouse model to more accurately mimic the mutation found in men with SBMA. The transgenic mice showed many of the symptoms of humans with the disease.

Researchers found that MEPB effectively alleviated symptoms of SBMA in the mice. "Treating the mice with MEPB forestalled muscle atrophy and prevented loss of their motor neurons, with recovery of their testicles to normal size," Taylor said. "The treatment also protected their ability to walk and their muscle strength and endurance." ..."

Impaired Nuclear Export of Polyglutamine-Expanded Androgen Receptor in SBMA

The link below is to a very detailed report on a recent Kennedy's Disease (SBMA) research study. It is too detailed for me to summarize.

Impaired Nuclear Export of Polyglutamine-Expanded Androgen Receptor in Spinal and Bulbar Muscular Atrophy

 

... It has been widely reported that the ligand-dependent nuclear accumulation of mutant AR is required for SBMA pathogenesis17,18,46. This mechanistic insight into the toxicity of polyQ-expanded AR ultimately led to clinical studies that tested the effect of the androgen suppressors leuprorelin acetate and dutasteride on disease progression in SBMA patients81,82,83. Despite recent evidence that long-term treatment with leuprorelin acetate modestly slows disease progression84, overall the protective effects of androgen suppressors observed in SBMA animal models have not had a substantial impact on disease progression in symptomatic patients. The lack of an effective treatment for SBMA underscores the need for a better mechanistic understanding of aspects of mutant AR metabolism that can be targeted to ameliorate its toxic effects. To this end, the goal of this study was to determine if nuclear export, a poorly understood step in the metabolism of AR, plays a role in SBMA pathogenesis and whether reducing nuclear AR by enhancing its export can reduce its aggregation and toxicity.

The results of our study demonstrate (1) that the nuclear export of polyQ-expanded AR is impaired, (2) that enhancing the nuclear export of polyQ-expanded AR with an exogenous NES decreases its aggregation and toxicity by promoting its proteasomal degradation, (3) that polyQ-expanded AR exhibits reduced phosphorylation at S650 and that blocking S650 phosphorylation further exacerbates its nuclear export deficiency, and (4) that global disruption of nucleo/cytoplasmic transport is not a common feature of SBMA models.  ...

...  This study offers the first evidence that the nuclear export of polyQ-expanded AR is impaired, highlighting a novel aspect of AR metabolism that may contribute to the pathogenesis of SBMA. Furthermore, our data support a model in which the mutant AR is rapidly degraded by the proteasome once exported from the nucleus, thereby decreasing its stability, aggregation, and toxicity. Although additional work will be required to fully elucidate the mechanism underlying deficient nuclear export of polyQ-expanded AR, our results provide a new direction for investigations into therapeutic manipulation of the mutant, polyQ-expanded AR in SBMA.

Beyond motor neurons

This is a pretty good recap of what we know and what else might be of importance in finding a treatment or cure for Kennedy's Disease.

The entire post can be found here: 

Beyond motor neurons: expanding the clinical spectrum in Kennedy’s disease

The conclusions are shown below:

Conclusions

In SBMA, as in other genetic conditions caused by mutations in ubiquitously expressed genes, the clinical picture is the result of a complex interplay between differentially affected tissues, which struggle to cooperate to maintain homeostasis.

Extra-motor neuron features in SBMA, such as primary muscle atrophy or hormonal abnormalities, are emerging as clinically highly impactful in patients’ quality of life and disease progression. Their thorough investigations are proving critical for a number of reasons. First, they may provide important insights into common mechanisms of pathogenesis. Second, the peripheral abnormalities may offer the opportunity for direct functional assessments and repetitive samplings, therefore representing potentially exploitable biomarkers to track disease progression and/or response to therapy. Lastly, disentangling the underlying molecular mechanisms of this highly integrated inter-tissues cross-talk may offer unparalleled opportunities for therapeutic interventions in the near future.

MDA Grant for Research on SBMA

The following article appears in NewsWise. Click on the link below to read the entire article.

Dr. Carlo Rinaldi Receives Co-Funded AANEM Foundation/MDA Grant for Research on Spinal and Bulbar Muscular Atrophy

 Carlo Rinaldi, MD, PhD, has been selected as the recipient of a development grant co-funded by the AANEM Foundation and the Muscular Dystrophy Association (MDA). Dr. Rinaldi, who works as an Associate Professor in the Department of Physiology, Anatomy and Genetics in the Division of Medical Sciences at the University of Oxford in the United Kingdom, will be using this funding to increase understanding of the pathophysiology of spinal and bulbar muscular atrophy (SBMA). SBMA is a neuromuscular disorder characterized by the degeneration of lower motor neurons and primary muscle atrophy. Dr. Rinaldi’s ultimate goal is to develop effective therapeutic treatments for this yet incurable condition.

Dr. Rinaldi’s research objective is to characterize the role of the androgen receptor (AR) isoform 2 on AR biology and its impact on SBMA toxicity. His central hypothesis is that AR45 is a key regulator of AR activity and represents a promising therapeutic target for SBMA.

“There is currently no treatment available for SBMA,” explained Dr. Rinaldi. “This research work has the potential to shed new light on the role of the AR isoforms in both health and disease, advance understanding of the mechanisms of pathogenesis in SBMA, and provide a new therapeutic target in close relationship with the disease-causing mutation.” 

“Dr. Rinaldi has the strong support of the Neuroscience community in Oxford to pursue his research into the mechanisms of motor neuron degeneration in SBMA,” noted Kevin Talbot, MB, PhD, FRCP, Head of the Division of Clinical Neurology and Professor of Motor Neuron Biology and Consultant Neurologist at John Radcliffe Hospital in Oxford. “This is a neglected area and he is in an excellent position to be a leader in this field, both within Europe and worldwide.” …

New Funding for SBMA Research

The MDA announced the funding of $9.9 million dollars in research grants. The grant below is for the study of Kennedy's Disease.

Carlo Rinaldi, Ph.D., associate professor and clinician scientist at the University of Oxford in England, was awarded an MDA Development Grant to study how variants in the gene of the androgen receptor (AR) protein cause spinal-bulbar muscular atrophy (SBMA) and investigate whether a novel antisense oligonucleotide therapy approach can target these toxic variants. The results of the study will provide a better understanding of SBMA disease mechanisms, as well as develop a new therapy potentially capable of treating the disease.

This work has potential implications for other diseases of the motor unit as well, including spinal muscular atrophy (SMA) and ALS. This grant is co-funded by the American Association of Neuromuscular and Electrodiagnostic Medicine (AANEM).

Additional information was provided on another page:

“Better understanding of the underlying disease mechanisms, coupled with improvement of gene vector design, therapeutic gene selection, and methods of delivery, have made gene therapy a realistic option for neuromuscular conditions — and neurological diseases in general — for which no treatment option was available until few years ago. Many challenges still lie ahead, but we have good reasons to be very optimistic for the future.”

Carlo Rinaldi, associate professor and clinician scientist at the University of Oxford in England, was awarded an MDA Development Grant totaling $120,000 over 3 years to study the role of androgen receptor isoforms in SBMA pathogenesis and the potential as therapeutic targets. This grant is co-funded by the American Association of Neuromuscular and Electrodiagnostic Medicine (AANEM).

Mutations in the gene encoding the androgen receptor (AR) protein cause spinal and bulbar muscular atrophy (SBMA). SBMA is an adult-onset neuromuscular condition affecting males with unmet clinical need. It is not undestood how mutations in AR lead to primary degeneration of motor neurons and muscle in patients. The activity of AR and other hormone receptors can be modulated in human cells by isoforms and/or splice variants, which may block or enhance their functions.

Dr. Rinaldi and colleagues plan to investigate the role of AR alternative isoforms in mediating SBMA toxicity. By revealing how these isoforms regulate AR activity in health and disease, researchers expect to better understand the mechanisms of disease in SBMA and provide a novel rational therapeutic target. If successful, the work could pinpoint tissue-specific targets for therapy development, with implications not only for SBMA but for other diseases of the motor unit as well, including spinal muscular atrophy and amyotrophoic lateral sclerosis.

Study identifies potential drug for treatment of debilitating inherited neurological disease

The following is an excerpt from a Medical Press article. To read the entire article follow this link: Potential Drug Treatment

March 15, 2018

Dr. Paul Taylor of St. Jude Children's Research Hospital ...

"... and his colleagues were led to seek drugs to treat SBMA because of findings from a previous study in his laboratory. The study pinpointed a molecular niche in the mutant androgen receptor protein that appeared to be a key to driving SBMA symptoms. However, that niche did not seem to be essential to the normal function of the androgen receptor. The study started with fruit flies genetically engineered to have the human androgen receptor, giving the scientists a living "test tube" to explore the effects of mutating the receptor.

"This identification of a small patch of this protein that appeared to be functionally important for driving the disease, but is not essential for most androgen receptor functions, gave us a potential drug target," Taylor said.

Pharmaceutical companies have been developing drugs to target this small patch, called the "activator function-2" or "AF2" domain. The companies were testing the drugs as possible treatments for prostate cancer, which also involves the androgen receptor. Taylor obtained a collection of the test drugs to evaluate for use with SBMA.

Using the genetically engineered flies, the researchers identified two drugs—whose long chemical names are abbreviated TA and MEPB—that alleviated SBMA symptoms. Then, using mice, the scientists determined that MEPB more effectively reached target tissues in the brain and spinal cord.

For their trials of TA and MEPB as potential SBMA treatments, the researchers developed a new genetically engineered mouse model to more accurately mimic the mutation found in men with SBMA. The transgenic mice showed many of the symptoms of humans with the disease.

Researchers found that MEPB effectively alleviated symptoms of SBMA in the mice. "Treating the mice with MEPB forestalled muscle atrophy and prevented loss of their motor neurons, with recovery of their testicles to normal size," Taylor said. "The treatment also protected their ability to walk and their muscle strength and endurance." ..."

Impaired Protein Homeostasis in Neurodegenerative Diseases

Impaired Protein Homeostasis in Neurodegenerative Diseases

The below excerpt is from an article appearing in Select Science. Click on the title above to read the entire article. For a good explanation on autophagy, click on the link below the drawing to watch a video.

https://www.youtube.com/watch?v=PvnqzhtwGZU

“Learn how selective antibodies help decipher an impaired autophagy pathway in spino-bulbar muscular atrophy

Dr. Constanza Cortes, Assistant Professor in the Department of Neurology at Duke University School of Medicine, studies impaired protein homeostasis in polyglutamine diseases such as spino-bulbar muscular atrophy.

SS: What are polyglutamine diseases?

CC: Polyglutamine diseases are a family of inherited neurodegenerative disorders, all caused by expansion of a triplet-nucleotide, CAG, in the coding region of the affected genes. The most notable is Huntington’s Disease, caused by a CAG expansion in the huntingtin gene. Another polyglutamine disease is spino-bulbar muscular atrophy (SBMA), caused by a CAG expansion in the androgen receptor (AR) gene. As the CAG codon encodes for the amino acid glutamine, the resulting proteins all carry extended polyglutamine tracts, giving the name to this family of diseases.

I study SBMA, a neuromuscular condition that targets the skeletal muscle and motor neurons in the lower spinal cord. These express high levels of the mutant AR, that result in protein inclusions, accumulating in the nuclei of affected tissues. This suggests that impaired protein quality control may form the basis of the neurodegenerative phenotypes observed in SBMA.

SS: What is the focus of your research in spino-bulbar muscular atrophy (SBMA)?

CC: I focus on protein quality control mechanisms and investigate the role they may play in the pathogenesis of SBMA. Protein homeostasis (also known as proteostasis), is fundamental for the survival of neurons, and proteostasis dysfunction is a feature of many neurodegenerative diseases, including Alzheimer’s and Parkinson’s disease. Understanding the mechanisms underlying proteostasis dysfunction and uncovering novel targets for rescuing these defects may yield important therapeutic targets for diseases associated with proteostasis failure.

SS: How does impaired protein homeostasis contribute to neurodegeneration in SBMA?

CC: I have uncovered a previously unreported periphery-to-CNS signaling network originating in skeletal muscle. Using a transgenic mouse model for a gene that’s a master regulator of cellular clearance and metabolism, conditionally expressed in the skeletal muscle, I have shown improved proteostasis in the CNS during normal aging. This suggests that maintaining skeletal muscle proteostasis during aging may yield important neuroprotective benefits in the aging brain.

In agreement with this, these muscle-specific proteostasis-activated mice perform significantly better in neurocognitive testing at 18 months of age compared to their age-matched control littermates. This suggests the existence of secreted signals originating in skeletal muscle and targeting the CNS, resulting in improved proteostasis control in the brain. My current work focuses on identifying those signals and testing their ability to rescue neurodegenerative ‘proteinopathies’, including Alzheimer’s disease….” For more, click on the heading at the top of this page.

What is the Defect in our DNA?

[Updated 2009 Post] 

A few years ago, I asked one of the doctors on the KDA's Scientific Review Board to describe the defect in our DNA and what it means to those of us living with Kenndy's Disease. His explanation follows:

"The androgen receptor is important for our body's response to male hormones, such as testosterone and dihyodrotesteoserone. The receptor is like a baseball glove, and normally catches ("binds") androgens and then moves them to the nucleus, which is the main control center for the cell. There it helps control the things that make us men (like the genes for watching TV while lounging in our favorite chairs). In Kennedy disease, it is as if the lacing has come out of our baseball glove, and the androgen receptor is not working right. The glove does not have the right shape (it is misfolded), and that makes it hard to catch the baseball well. The androgen receptor can still move to the nucleus, but because it is misfolded, this causes problems. The cell does not work right and eventually might die. And, since this androgen receptor is made by both motor nerve cells and muscle cells, this causes us big problems with moving our arms and legs, and swallowing."

Now for a more scientific explanation, a college professor on the board provided the following:

"In Kennedy's Disease, the defective gene is in the "X" chromosome. The symptoms of Kennedy's Disease are due to a mutation in the gene that produces the androgen receptor (AR) protein. The AR protein acts to mediate all the effects of androgens (testosterone and dihydrotestosterone - male hormones) in cells and in our bodies. Those individuals with Kennedy's Disease produce an altered form of the AR protein, a form that, while it still works well enough mediating the effects of androgens (and so males are still male), produces an additional effect of causing certain spinal cord and brain cells to die. The affected nerve cells are primarily those that control the activation of muscle cells. When the nerve cells die, the muscle fibers that they control shrink and become inactive causing the muscle weakness characteristic of Kennedy's Disease."

Research suggests that the altered form of the AR has problems being recycled (cleaned of all garbage) in the presence of androgens and instead of being completely removed; mutant proteins (the garbage) are only partially digested in the affected cells. This partial digestion of the AR results in the production of AR fragments that, through an unknown mechanism, are toxic to cells. Since this effect is dependent on relatively high levels of androgens, severe muscle weakening is generally not seen in women who carry the mutant form of the AR gene.



Okay, now that I have read both explanations, I feel a little more comfortable. However, I still do not believe I have accomplished what I set out to do today and that was to simplify the explanation. So, I asked "Joe, the Plumber" and he explained the defect like this. “The thingamajig is broken and that causes the whatchamacallits not to work properly.” Now that helps. 😛

KDA Awards Five Research Grants

Five research grants were awarded totaling $199,000. Award recipients and summaries are listed below.

Award $50,000
Targeting AR toxicity in SBMA by modulation of USP7 activity.
Anna Pluciennik, Ph.D.
Department of Biochemistry and Molecular Biology
Thomas Jefferson University

Summary: PolyQ-expanded androgen receptor-dependent cellular toxicity in the neuromuscular system is a characteristic feature of SBMA pathogenesis, although the molecular mechanisms for these effects are poorly understood. However, because cellular toxicity in SBMA is likely to arise, at least in part, from the polyQ-expanded-dependent dysregulation of protein-protein interactions that sustain normal cellular function, we reasoned that identification of such dysregulated interactions might help reveal potential therapeutic targets for disease modification. Therefore, as part of a KDA-funded project (2014), we used a quantitative proteomics approach and identified a deubiquitinating enzyme, USP7, that preferentially interacts with polyQ-expanded AR and contributes to toxicity. In fact, we have demonstrated that not only does partial knockdown of USP7 protein expression decrease mutant AR-dependent aggregation and dihydrotestosterone-dependent cytotoxicity, but also that overexpression of the protein aggravates these cellular effects. These results establish the need for further investigation into the role of the deubiquitinating function of USP7 in SBMA pathogenesis. The objective of this -research is to investigate the functional consequence of pharmacological inhibition of USP7 deubiquitinase activity in cellular and mouse models of SBMA. These studies will extend our previous KDA-funded proteomics work and, if successful, will establish the validity of inhibition of USP7 activity as a therapeutic approach for the treatment of SBMA.

Award $50,000
Identification of New Polyglutamine-Specific Mutant AR-Interacting Proteins in SBMA Motor Neurons
Xia Feng
Postdoctoral Fellow, Neurogenetics Branch
National Institute of Neurological Disorders and Stroke, National Institute of Health

Summary: Spinal and bulbar muscular atrophy (SBMA) is a slowly progressive neuromuscular disease. As the disease proceeds, nerve cells in the spinal cord (called motor neurons) start to die and muscle cells will waste away. The causative mutation of SBMA is the mutant androgen receptor (AR) with an abnormal expansion in the certain region. Such aberrant expansion in the mutant protein (called a polyglutamine tract) damages the normal function of the protein as well as obtains toxicity. Thus, it is important to understand how the mutant AR is regulated via other proteins in the disease. Here, I propose to use a human induced pluripotent stem cell model to generate disease-relevant motor neuron-like cells, and use these cells to identify specific interacting proteins of the mutant androgen receptor. I am hoping that my research will help provide a motor neuron-specific basis for designing and developing novel therapeutics for the treatment of SBMA.

Award $33,000
Transcellular regulation of the proteostasis network in Kennedy’s disease
Laura Bott, Ph.D.
Postdoctoral Fellow
Molecular Biosciences, Northwestern University

Summary: Misfolding and abnormal accumulation of the mutant androgen receptor in Kennedy’s disease indicates that the cellular machinery controlling protein abundance, folding, and transport (proteostasis) may be defective in the disease. We are planning to study molecular mechanisms of Kennedy’s disease in the worm Caenorhabditis elegans. For this, we will genetically engineer worms to express the mutant androgen receptor in the neuromuscular system and assess effects of the polyglutamine expansion on proteostasis regulation in this model organism. Insights into cell type-specific effects and regulation across tissues may lead to new therapeutic approaches for this disease.

Award $33,000
One gene, many proteins: investigating the role of AR isoform 2 as a therapeutic target for SBMA
Carlo Rinaldi, MD, PhD
Department of Physiology, Anatomy and Genetics
University of Oxford

Summary: The activity of steroid hormone receptors, such as progesterone and oestrogen receptors, is modulated by a number of isoforms and splice variants in a tissue-specific manner, in both health and disease. Androgen receptor may be no exception. AR isoform 2, or AR45 by the molecular weight of its encoded widely-expressed protein, is the only naturally occurring AR isoform, arising from use of an alternative transcriptional start site in intron 1 of the AR gene and containing a short, unique seven amino-acid-long N-terminal stretch instead of the long N-terminal domain found in the full length AR. Overarching aim of this proposal is to unravel the contribution of AR isoform 2 to SBMA pathogenesis and provide a novel therapeutic target for this disease, suitable for oligonucleotide antisense targeting without running the risks associated with silencing of the only available copy of the AR gene in males.

Award $33,000
The use of induced stem cells and microfluidics for developing new assays to identify new therapies for Kennedy’s disease
Thomas M Durcan, Ph.D., Assistant Professor,
Montreal Neurological Institute, McGill University

Summary: It is important to explore new avenues in the search for treatments for Kennedy’s disease (KD). Our overall goal is to develop disease-relevant assays that use human motor neurons made from stem cells of both men with Kennedy’s disease and healthy individuals. Using special silicone microfluidic devices to grow motor neurons, we will measure the function of neurons upon exposure to different compounds. First, we will develop assays to measure the survival and growth of the motor neurons. Next, we will look at the how well mitochondria work and move within the neurons. Finally, we aim to set up an assay to test the ability of the normal and KD motor neurons to form synapses (junctions). Taken together, these innovative assays will provide a foundation to build a KD drug discovery platform to screen for promising compounds and targets to treat KD.

Is ASO a potential treatment for Kennedy’s Disease?

This is a follow up to my November 15, 2017, article, “MDAAnnounces SBMA Research Grant.” The research paper was a little over my head (nothing new for me), so I asked the KDA’s resident biology professor, Ed Meyertholen, to explain what Dr. Lieberman’s research was about. Below is Ed’s summary of the grant. For a short primer, I have included the link to a video on DNA-RNA.

"The grant the Andy Lieberman received was to continue the research on the use of Anti-Sense Oligonucleotides (ASO) as a treatment for Kennedy’s Disease (KD). To best understand how it works, it is important to remember the following:

1. KD is believed to be the result of a misfolded protein, specifically, the protein known as the Androgen Receptor (AR).

2. Proteins are built of specific sequences of amino acids, thus to make a protein, one must have amino acids and the sequence of the amino acids of the protein of interest.

3. The sequence of amino acids for any protein are hard coded into our genes - our DNA.  Thus to make a particular protein, the cell must find the gene that codes for the sequence for that protein and read the code to get the sequence.  The structure of the cell that makes the protein is the ribosome.

4. In KD, the misfolded protein is known as the Androgen Receptor (AR) and it misfolds because our DNA has an error in the sequence.  So, when our cells want to synthesize the AR, our instructions are faulty and when we make the resulting protein, it somehow causes cells to die albeit, slowly.

5. Protein synthesis requires two major steps, the first is the synthesis of an RNA copy (RNA is like DNA) of the gene (DNA) which codes for the protein of interest (this occurs in the nucleus).  The RNA synthesis is known as transcription.

6. The RNA copy (which contains the code for the protein) leaves the nucleus and goes to the ribosome.  Here the code is read and the protein is synthesized.  This actual making of the protein is known as translation.

7.  An ASO is a specially designed fragment of RNA that binds only to a specific RNA.  An ASO can be designed to bind specifically to any given RNA.  In this case, the ASO binds only to the RNA that is used to make the AR.  When the ASO binds to the RNA, the cell responds by destroying the RNA (that is what it does) - thus the RNA to make the AR is destroyed before the protein is made and thus no AR is synthesized and thus, it is hoped, no KD.

8.  Andy's grant is, as I understand it, will try to test this procedure on mice models of KD and involve investigating the best ways to deliver the ASO.  Let me also add, there have been several published studies that have shown that ASO's are effective in preventing KD in mice.  Other ASO's have been developed to treat other diseases and just recently, one was approved for use in a disease called Spinal Muscular Atrophy (this is not KD)."  

Autophagy - akin to a garbage disposal system

I thought I published an article on this study, but cannot find it. So, here it is.

Target Identified For Rare Inherited Neurological Disease

Scientists show bad androgen receptor impairs body’s ability to dispose of damaged cells

Researchers at University of California, San Diego School of Medicine have identified the mechanism by which a rare, inherited neurodegenerative disease causes often crippling muscle weakness in men, in addition to reduced fertility.

The study, published August 10 in the journal Nature Neuroscience, shows that a gene mutation long recognized as a key to the development of Kennedy’s disease impairs the body’s ability to degrade, remove and recycle clumps of “trash” proteins that may otherwise build up on neurons, progressively impairing their ability to control muscle contraction. This mechanism, called autophagy, is akin to a garbage disposal system and is the only way for the body to purge itself of non-working, misshapen trash proteins.

“We’ve known since the mid-1990s that Alzheimer's disease, Parkinson's disease and Huntington's disease are caused by the accumulation of misfolded proteins that should have been degraded, but cannot be turned over,” said senior author Albert La Spada, MD, PhD and professor of pediatrics, cellular and molecular medicine, and neurosciences. “The value of this study is that it identifies a target for halting the progression of protein build-up, not just in this rare disease, but in many other diseases that are associated with impaired autophagy pathway function.” ...

... “Our study tells us that if we can find a way to keep TFEB working, we likely can prevent this disease and others like it from progressing,” La Spada said. “We now have a target for new therapies to treat not only Kennedy's disease, but also many more common neurological disorders.”

Follow this link to read the entire article: UC San Diego News

New Research Paper Published on Kennedy's Disease

The World Journal of Biological Chemistry published another interesting Kennedy’s Disease study this week. Below is a portion of the abstract. The entire paper can be read by following the link below. This is preliminary research and more study is required to determine the potential benefits and possible side effects.

Background - The AR gene contains CAG repeats which affect receptor function, where fewer repeats leads to increased receptor sensitivity to circulating androgens and more repeats leads to decreased receptor sensitivity.

Identification of neuron selective androgen receptor inhibitors

World J Biol Chem. May 26, 2017; 8(2): 138-150

AIM

To identify neuron-selective androgen receptor (AR) signaling inhibitors, which could be useful in the treatment of spinal and bulbar muscular atrophy (SBMA), or Kennedy’s disease, a neuromuscular disorder in which deterioration of motor neurons leads to progressive muscle weakness.

METHODS

Cell lines representing prostate, kidney, neuron, adipose, and muscle tissue were developed that stably expressed the CFP-AR-YFP FRET reporter. We used these cells to screen a library of small molecules for cell type-selective AR inhibitors. Secondary screening in luciferase assays was used to identify the best cell-type specific AR inhibitors. The mechanism of action of a neuron-selective AR inhibitor was examined in vitro using luciferase reporter assays, immunofluorescence microscopy, and immunoprecipitations. Rats were treated with the most potent compound and tissue-selective AR inhibition was examined using RT-qPCR of AR-regulated genes and immunohistochemistry.

RESULTS

We identified the thiazole class of antibiotics as compounds able to inhibit AR signaling in a neuronal cell line but not a muscle cell line. One of these antibiotics, thiostrepton is able to inhibit the activity of both wild type and polyglutamine expanded AR in neuronal GT1-7 cells with nanomolar potency. The thiazole antibiotics are known to inhibit FOXM1 activity and accordingly, a novel FOXM1 inhibitor FDI-6 also inhibited AR activity in a neuron-selective fashion. The selective inhibition of AR is likely indirect as the varied structures of these compounds would not suggest that they are competitive antagonists. Indeed, we found that FOXM1 expression correlates with cell-type selectivity, FOXM1 co-localizes with AR in the nucleus, and that shRNA-mediated knock down of FOXM1 reduces AR activity and thiostrepton sensitivity in a neuronal cell line. Thiostrepton treatment reduces FOXM1 levels and the nuclear localization of beta-catenin, a known co-activator of both FOXM1 and AR, and reduces the association between beta-catenin and AR. Treatment of rats with thiostrepton demonstrated AR signaling inhibition in neurons, but not muscles.

CONCLUSION

Our results suggest that thiazole antibiotics, or other inhibitors of the AR-FOXM1 axis, can inhibit AR signaling selectively in motor neurons and may be useful in the treatment or prevention of SBMA symptoms.

Drawing and Background of CAG-AR - Wikipedia

What is Kennedy's Disease?

Back to the Basics

The Androgen Receptor Gene

The AR gene provides instructions for making a protein called an androgen receptor. Androgens are hormones (such as testosterone) that are important for normal male sexual development before birth and during puberty. Androgen receptors allow the body to respond appropriately to these hormones. Androgens and androgen receptors also have other important functions in both males and females, such as regulating hair growth and sex drive.

The receptors are present in many of the body's tissues, where they attach (bind) to androgens. The resulting androgen-receptor complex then binds to DNA and regulates the activity of androgen-responsive genes. By turning the genes on or off as necessary, the androgen receptor helps direct the development of male sexual characteristics. Androgens and androgen receptors also have other important functions in both males and females, such as regulating hair growth and sex drive.

In one region of the AR gene, a DNA segment known as CAG is repeated multiple times. This CAG segment is called a triplet or trinucleotide repeat. In most people, the number of CAG repeats in the AR gene ranges from fewer than 10 to about 37.

The AR Gene and Spinal Bulbar Muscular Atrophy

Kennedy’s Disease, aka, Spinal Bulbar Muscular Atrophy, results from a particular type of mutation, an expansion of the CAG trinucleotide repeat, in the AR gene. This receptor attaches (binds) to a class of hormones called androgens.

With Kennedy’s Disease, the CAG is abnormally repeated from 38 to more than 60 times causing a disorder of the specialized nerve cells that control muscle movement. Researchers believe that a fragment of the androgen receptor protein containing the CAG repeats accumulates within these cells and interferes with normal cell functions. This buildup leads to the gradual loss of motor neurons, which results in muscle weakness and wasting (atrophy).

People with a higher number of CAG repeats tend to develop signs and symptoms of Kennedy’s Disease at an earlier age. [ FrequentlyAsked Questions about KD ]

Characteristics of Spinal Bulbar Muscular Atrophy

Spinal Bulbar Muscular Atrophy mainly affects males and is characterized by muscle weakness and wasting (atrophy) that usually begins in adulthood and worsens slowly over time. Muscle wasting in the arms and legs results in cramping; leg muscle weakness can also lead to difficulty walking and a tendency to fall.

Certain muscles in the face and throat (bulbar muscles) are also affected, which causes progressive problems with swallowing and speech. Additionally, muscle twitches (fasciculations) are common. Some males with the disorder experience unusual breast development (gynecomastia) and may be unable to father a child (infertile).  [ CommonSymptoms ]

Inheritance Pattern

This condition is inherited in an X-linked pattern. A condition is considered X-linked if the mutated gene that causes the disorder is located on the X chromosome, one of the two sex chromosomes. In males (who have only one X chromosome), a mutation in the only copy of the gene in each cell causes the disorder. In most cases, males experience more severe symptoms of the disorder than females (who have two X chromosomes). [ GeneticChart ]

DNA Test

Fortunately, today there is a DNA test to determine if a person has Kennedy’s Disease. Your doctor can draw some blood and send it to a DNA lab for testing. Test results are normally returned within three-to-six weeks. [ TestDetails ]

Note: Most information provided by the Genetics Home Reference

An Ode to the Androgen Receptor

I found this inspiring piece on the KDUK website this morning. Helen Devine found a way to help explain Kennedy’s Disease and the current research associated with this rare disorder.

When Research Meets Poetry

We have seen at first hand now passionate and driven the research team at UCL is. What we didn’t  Helen is at the front line in the fight against Kennedy's Disease, and to further raise awareness, she entered this poem in a Medical Research Council competition that sought creative writing from researchers that told readers '"Why does my research matter?' We at Kennedy's Disease UK were delighted that Helen was one of the 14 shortlisted finalists this year. Sadly, she didn’t win, but we feel she's a winner with this great explanation of Kennedy's Disease and the vital research she and the team are carrying out at University College London (UCL).

The Max Perutz Science Writing Award aims to encourage and recognize outstanding written communication among MRC PhD students. The annual competition challenges entrants to write an 800-word article for the general public answering tine question: 'Why does my research matter? This is Helen's fantastic entry.

An Ode to the Androgen Receptor

Neurodegenerative diseases

Occur when nerve cells die

We certainly know that it happens

But we aren't quite sure how or why

Parkinson's Disease would be easy

And Alzheimer’s or Huntington’s too

They're probably near the top of your list

If I asked you to name me a few.

But Spinal Bulbar Muscular Atrophy?

Not heard of it before?

There's something special about it,

Let me tell you a little bit more.

Weakness in the arms and legs

Make it tricky for patients to walk

Weakness in the face and tongue

Make it hard to swallow and to talk.

The faults in the Androgen Receptor

A particular genetic mutation

Male patients have the disease

Women pass it to the next generation.

When the receptor binds testosterone

The troubles really start

Patients get weakness, infertility

And problems in the heart_

The disease is slowly progressive

With no treatment and no cure

I'm hoping that might change

If I can understand it a little bit more.

So I'm going on a journey

To find out why these cells die

I am searching for the pathways

using microscopes and dyes.

The very first step is to find a way

To make a good human model

Studies from other cells and mice

May not snow the real disease problem.

Induced pluripotent stem cells

Are an exciting new innovation

Stem cells from patient skin cells

Have the androgen receptor mutation.

Motor nerves from stem cells

I grow them up in a dish

And once they are fully grown

I can study them with relish_

Stress, transport, mitochondria

Possible avenues to pursue

In the course of the research

I may find something new.

Stress is hard to deal with

In research and in a cell

I can go for a little jog

But a cell can't in a well.

So they have a special mechanism

The neat shock response its name

If this isn't working correctly

Then it may be to blame.

Axons carry the messages

One end of the cell to the other

A traffic jam in this transport

Can lead to a spot of bother,

Motor nerves are very long

So they are at great risk

If blockages and hold ups

Mean transport isn't brisk.

Mitochondria provide the energy

A cell needs to survive

If the fuel supply isn't good enough

Then the cell can start to die.

So if their shape is faulty

And they aren't working right

Tine cells start to malfunction

Pack up and say goodnight

If cell death is like a puncture

Discovering it is not enough

The next job is to fix it

And that can prove quite tough.

Motor neurons on a plate

Will be a way to screen

For a drug to reverse cell death;

That would De the dream.

SBMA is a rare disease

But patients still need a cure

I hope I can identify a good one

That's what my research is for.

The findings that I find

May also hold the key

To overall common pathways

In neurodegenerative disease.

My research is for patients with SBMA

For whom taking journeys is hard

And for whom it is a challenge
To read this poem out loud. 

Diane Merry - SBMA Researher

The MDA published the following article on a Kennedy's Disease researcher many of us know.

Five Questions with SBMA Researcher Diane Merry

Diane Merry, associate professor at Thomas Jefferson University in Philadelphia, is working to identify therapeutic opportunities to promote normal androgen receptor function while preventing the toxic effects of polyglutamine expansion in spinal-bulbar muscular atrophy (SBMA). With GlaxoSmithKline, Merry will test small molecule compounds that activate an enzyme called SIRT1 in cell and mouse models of SBMA to determine their therapeutic potential.

Please describe your current research in SBMA.
Many neurodegenerative diseases result from protein misfolding and accumulation due to genetic or environmental causes. SBMA is one such disease; it is an inherited, adult-onset, neuromuscular disease that is caused by the expansion of a polyglutamine tract within the androgen receptor (AR) and is related mechanistically to other neurodegenerative diseases caused by polyglutamine expansion.

An important feature of SBMA is that its onset and progression are dependent on the binding of androgenic hormones to the mutant receptor. Our studies of mouse and cell models of SBMA that reproduce the androgen- and polyglutamine-dependent nuclear AR aggregation seen in patients, as well as its toxicity, revealed that the mutant AR must be modified by the addition of acetyl groups for its aggregation and toxicity. Moreover, the deacetylase SIRT1 is strongly neuroprotective in cell models of SBMA and this neuroprotection largely depends upon its ability to remove acetyl groups from the mutant AR.

We are investigating the therapeutic potential of activating this acetyl group-removing enzyme, SIRT1, with small molecule activators. We will test these compounds in cell models, and ultimately in mouse models, of SBMA.  We anticipate that these studies will reveal new and powerful opportunities for therapeutic development in SBMA.

Is this your first MDA grant?
No, I was funded previously (as a post-doctoral fellow and then when I started my lab) by MDA.  It means a tremendous amount to me to be funded once again by this organization that is so committed to finding a cure for neuromuscular diseases.

What inspired you to study SBMA?
I come from a strong background of training in molecular genetics and molecular pathophysiology. I began to study the molecular basis of this disease in 1993, just a short time after the genetic cause of the disease was identified.  I have been studying SBMA ever since that time — for the past 22 years.

What is your focus within the SBMA field, and why is it important?
My focus is on the mutant androgen receptor protein itself and the effect of the polyglutamine expansion on androgen receptor metabolism (structure, trafficking, protein interactions, turnover), in order to identify therapeutic opportunities to promote normal androgen receptor function while preventing the toxic effects of the polyglutamine expansion. The work funded by this grant is designed to do just that.

There is currently no effective therapy or cure for SBMA and thus an effective therapy is a primary goal of our work. The work funded here is likely to bring us closer to that goal.

What do you feel people impacted by SBMA can have the most hope about with respect to research right now?
We know so much more about the disease process at this point in time, and we and others have identified disease targets for therapeutic development. I do think that a therapy or therapies are within sight for SBMA in the foreseeable future.

Does your work have any potential implications for other disease fields?
Our work has implications for other diseases in which the enzyme SIRT1 is neuroprotective.  Although the SIRT1 target proteins may be distinct, the identification of small molecule activators of SIRT1 is likely to open up possibilities for using these activators to treat other diseases.

A question concerning CAG repeats

I recently received the following question this week:

“Do you know of any understandable explanation of CAG Count and its importance and implications to SBMA sufferers? Everything I have found is pretty unintelligible to me (and I thought I was a pretty intelligent kind of a person!!). From what I can gather the count length - whatever that is (& I have no idea of mine) is important to diagnosing the condition but is of no particular relevance in assessing the outcome. Is that correct?”


So I consulted our biology professor and asked for help. Ed provided the following explanation of the DNA mutation and Kennedy’s Disease. I definitely learned something from his explanation. Thanks, Ed.

______________________________________

Kennedy’s Disease (aka SBMA) is a genetic disease.  Aside from the fact that this means one inherits the disease from one's parents, this fact has other implications.   The fact that it is genetic also means that there is a change in a gene - a gene being an inheritable factor that influences some trait.  Genes are made of a type of biomolecule called DNA.  DNA, in turn, is composed of long chains of small subunit molecules called nucleotides.  Different genes are linked together to form larger DNA structures called chromosomes.  Humans have 23 pairs of chromosomes (for a total number of 46) and each chromosome can have over a thousand different genes.  Nonetheless, each chromosome in every person should contain the same genes in the same order.  Now since genes are made up of DNA, and genes make up chromosomes, chromosomes contain DNA.  So essentially, the genetic material has a hierarchical structure:  Chromosomes:Genes:Nucleotides.  A simple, similar analogy might be Building:Walls:Bricks.

Now one might wonder what makes each gene different.  As was stated, each gene is made of DNA which is in turn made of nucleotides.  DNA employs 4 different nucleotides: adenine, guanine, cytosine and thymine.  Scientists, being efficient (or maybe lazy) abbreviate these with single letters - A, G, C and T.   Each gene has a specific, unique sequence of nucleotides much like words have a specific, unique sequence of letters.  The primary difference is that each gene's sequence is very long, often in excess of a thousand nucleotides.   The sequence of nucleotides in a gene tells the cell how to make a specific protein, thus each gene codes for the production of a specific protein.  If the nucleotide sequence of a gene is altered (this alteration is known as a mutation), the resulting protein is altered and it may not work normally (and often does not work at all).  The result of such a change may results in changes in the way the cells work and if this occurs, we would say that this would be a genetic disease.  Thus Kennedy’s Disease is due to a mutation in a specific gene that alters the function and structure of a specific protein.

The gene mutated in Kennedy’s Disease is the gene that codes for the protein known as the androgen receptor (AR).  The type of change in the nucleotide sequence in the gene for AR that causes KD is quite unusual.  Usually, mutations are due to nucleotide substitutions or deletions or insertions - but this is not true for Kennedy’s Disease.

Kennedy’s Disease is due to the repeat of a three nucleotide sequence - a repeat of the sequence that is cytosine-adenine-guanine or CAG in the scientific shorthand.   This CAG (pronounces see-a-gee, NOT pronounced so it rhymes with hag) repeat actually occurs in the AR gene in all humans where its repeat number is quite variable.  The repeat only causes Kennedy’s Disease when the repeat number exceeds 40 (CAG repeated 40 times).  Individuals with repeat numbers less than 40 do not have Kennedy’s Disease.  At this time, it is not clear why this causes Kennedy’s Disease (scientists are trying to find out) but it does!