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Karliner J, Liu Y, Merry DE. Mutant androgen receptor induces neurite loss and senescence independently of ARE binding in a neuronal model of SBMA. Proc Natl Acad Sci U S A 2024; 121:e2321408121. [PMID: 38976730 PMCID: PMC11260106 DOI: 10.1073/pnas.2321408121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2023] [Accepted: 06/11/2024] [Indexed: 07/10/2024] Open
Abstract
Spinal and bulbar muscular atrophy (SBMA) is a slowly progressing neuromuscular disease caused by a polyglutamine (polyQ)-encoding CAG trinucleotide repeat expansion in the androgen receptor (AR) gene, leading to AR aggregation, lower motor neuron death, and muscle atrophy. AR is a ligand-activated transcription factor that regulates neuronal architecture and promotes axon regeneration; however, whether AR transcriptional functions contribute to disease pathogenesis is not fully understood. Using a differentiated PC12 cell model of SBMA, we identified dysfunction of polyQ-expanded AR in its regulation of neurite growth and maintenance. Specifically, we found that in the presence of androgens, polyQ-expanded AR inhibited neurite outgrowth, induced neurite retraction, and inhibited neurite regrowth. This dysfunction was independent of polyQ-expanded AR transcriptional activity at androgen response elements (ARE). We further showed that the formation of polyQ-expanded AR intranuclear inclusions promoted neurite retraction, which coincided with reduced expression of the neuronal differentiation marker β-III-Tubulin. Finally, we revealed that cell death is not the primary outcome for cells undergoing neurite retraction; rather, these cells become senescent. Our findings reveal that mechanisms independent of AR canonical transcriptional activity underly neurite defects in a cell model of SBMA and identify senescence as a pathway implicated in this pathology. These findings suggest that in the absence of a role for AR canonical transcriptional activity in the SBMA pathologies described here, the development of SBMA therapeutics that preserve this activity may be desirable. This approach may be broadly applicable to other polyglutamine diseases such as Huntington's disease and spinocerebellar ataxias.
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Affiliation(s)
- Jordyn Karliner
- Department of Biochemistry and Molecular Biology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA19107
| | - Yuhong Liu
- Department of Biochemistry and Molecular Biology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA19107
| | - Diane E. Merry
- Department of Biochemistry and Molecular Biology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA19107
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Johnson SL, Tsou WL, Prifti MV, Harris AL, Todi SV. A survey of protein interactions and posttranslational modifications that influence the polyglutamine diseases. Front Mol Neurosci 2022; 15:974167. [PMID: 36187346 PMCID: PMC9515312 DOI: 10.3389/fnmol.2022.974167] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2022] [Accepted: 07/27/2022] [Indexed: 01/20/2023] Open
Abstract
The presence and aggregation of misfolded proteins has deleterious effects in the nervous system. Among the various diseases caused by misfolded proteins is the family of the polyglutamine (polyQ) disorders. This family comprises nine members, all stemming from the same mutation—the abnormal elongation of a polyQ repeat in nine different proteins—which causes protein misfolding and aggregation, cellular dysfunction and disease. While it is the same type of mutation that causes them, each disease is distinct: it is influenced by regions and domains that surround the polyQ repeat; by proteins with which they interact; and by posttranslational modifications they receive. Here, we overview the role of non-polyQ regions that control the pathogenicity of the expanded polyQ repeat. We begin by introducing each polyQ disease, the genes affected, and the symptoms experienced by patients. Subsequently, we provide a survey of protein-protein interactions and posttranslational modifications that regulate polyQ toxicity. We conclude by discussing shared processes and pathways that bring some of the polyQ diseases together and may serve as common therapeutic entry points for this family of incurable disorders.
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Affiliation(s)
- Sean L. Johnson
- Department of Pharmacology, Wayne State University, Detroit, MI, United States
| | - Wei-Ling Tsou
- Department of Pharmacology, Wayne State University, Detroit, MI, United States
| | - Matthew V. Prifti
- Department of Pharmacology, Wayne State University, Detroit, MI, United States
| | - Autumn L. Harris
- Department of Pharmacology, Wayne State University, Detroit, MI, United States
- Maximizing Access to Research Careers (MARC) Program, Wayne State University, Detroit, MI, United States
| | - Sokol V. Todi
- Department of Pharmacology, Wayne State University, Detroit, MI, United States
- Maximizing Access to Research Careers (MARC) Program, Wayne State University, Detroit, MI, United States
- Department of Neurology, Wayne State University, Detroit, MI, United States
- *Correspondence: Sokol V. Todi,
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Dantuma NP, Herzog LK. Machado-Joseph Disease: A Stress Combating Deubiquitylating Enzyme Changing Sides. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1233:237-260. [PMID: 32274760 DOI: 10.1007/978-3-030-38266-7_10] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Machado-Joseph disease (MJD), also known as Spinocerebellar ataxia type 3 (SCA3), is an autosomal dominant inheritable neurodegenerative disorder. After a long pre-symptomatic period, this late-onset disease progressively disables patients and typically leads to premature death. Neuronal loss in specific regions of the cerebellum, brainstem and basal ganglia as well as the spinal cord explains the spectra of debilitating neurological symptoms, most strikingly progressive limb, and gait ataxia. The genetic cause of MJD is a polyglutamine (polyQ) repeat expansion in the gene that encodes ataxin-3. This polyQ-containing protein displays a well-defined catalytic activity as ataxin-3 is a deubiquitylating enzyme that removes and disassembles ubiquitin chains from specific substrates. While mutant ataxin-3 with an expanded polyQ repeat induces cellular stress due to its propensity to aggregate, the native functions of wild-type ataxin-3 are linked to the cellular countermeasures against the very same stress conditions inflicted by polyQ-containing and other aggregation-prone proteins. Hence, a mixture of gain-of-function and loss-of-function mechanisms are likely to contribute to the neuronal demise observed in MJD. In this review, we discuss the intimate link between ataxin-3 and cellular stress and its relevance for therapeutic intervention in MJD.
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Affiliation(s)
- Nico P Dantuma
- Department of Cell and Molecular Biology (CMB), Karolinska Institutet, Stockholm, Sweden.
| | - Laura K Herzog
- Department of Cell and Molecular Biology (CMB), Karolinska Institutet, Stockholm, Sweden
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Pennuto M, Rinaldi C. From gene to therapy in spinal and bulbar muscular atrophy: Are we there yet? Mol Cell Endocrinol 2018; 465:113-121. [PMID: 28688959 DOI: 10.1016/j.mce.2017.07.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/07/2017] [Revised: 06/30/2017] [Accepted: 07/03/2017] [Indexed: 01/12/2023]
Abstract
Abnormal polyglutamine expansions in the androgen receptor (AR) cause a muscular condition, known as Kennedy's disease or spinal and bulbar muscular atrophy (SBMA). The disease is transmitted in an X-linked fashion and is clinically characterized by weakness, atrophy and fasciculations of the limb and bulbar muscles as a result of a toxic gain-of-function of the mutant protein. Notably, affected males also show signs of androgen insensitivity, such as gynaecomastia and reduced fertility. The characterization of the natural history of the disease, the increasing understanding of the mechanism of pathogenesis and the elucidation of the functions of normal and mutant AR have offered a momentum for developing a rational therapeutic strategy for this disease. In this special issue on androgens and AR functions, we will review the molecular, biochemical, and cellular mechanisms underlying the pathogenesis of SBMA. We will discuss recent advances on therapeutic approaches and opportunities for this yet incurable disease, ranging from androgen deprivation, to gene silencing, to an expanding repertoire of peripheral targets, including muscle. With the advancement of these strategies into the clinic, it can be reasonably anticipated that the landscape of treatment options for SBMA and other neuromuscular conditions will change rapidly in the near future.
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Affiliation(s)
- Maria Pennuto
- Dulbecco Telethon Institute, Centre for Integrative Biology, University of Trento, 38123 Trento, Italy; Department of Biomedical Sciences, University of Padova, 35121 Padova, Italy.
| | - Carlo Rinaldi
- Department of Physiology, Anatomy and Genetics, University of Oxford, OX1 3QX Oxford, UK.
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Swift-Gallant A, Monks DA. Androgenic mechanisms of sexual differentiation of the nervous system and behavior. Front Neuroendocrinol 2017; 46:32-45. [PMID: 28455096 DOI: 10.1016/j.yfrne.2017.04.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/22/2017] [Revised: 04/21/2017] [Accepted: 04/24/2017] [Indexed: 01/23/2023]
Abstract
Testicular androgens are the major endocrine factor promoting masculine phenotypes in vertebrates, but androgen signaling is complex and operates via multiple signaling pathways and sites of action. Recently, selective androgen receptor mutants have been engineered to study androgenic mechanisms of sexual differentiation of the nervous system and behavior. The focus of these studies has been to evaluate androgenic mechanisms within the nervous system by manipulating androgen receptor conditionally in neural tissues. Here we review both the effects of neural loss of AR function as well as the effects of neural overexpression of AR in relation to global AR mutants. Although some studies have conformed to our expectations, others have proved challenging to assumptions underlying the dominant hypotheses. Notably, these studies have called into question both the primacy of direct, neural mechanisms and also the linearity of the relationship between androgenic dose and sexual differentiation of brain and behavior.
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Affiliation(s)
- A Swift-Gallant
- Department of Psychology, University of Toronto, 100 St. George Street, Toronto, ON M5S 3G3, Canada; Department of Psychology, University of Toronto Mississauga, 3359 Mississauga Rd. N., Mississauga, ON L5L 1C6, Canada
| | - D A Monks
- Department of Psychology, University of Toronto, 100 St. George Street, Toronto, ON M5S 3G3, Canada; Department of Cells and Systems Biology, University of Toronto, 100 St. George Street, Toronto, ON M5S 3G3, Canada; Department of Psychology, University of Toronto Mississauga, 3359 Mississauga Rd. N., Mississauga, ON L5L 1C6, Canada.
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