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Malik SO, Wierenga A, Gao C, Akaaboune M. Plasticity and structural alterations of mitochondria and sarcoplasmic organelles in muscles of mice deficient in α-dystrobrevin, a component of the dystrophin-glycoprotein complex. Hum Mol Genet 2024; 33:1107-1119. [PMID: 38507070 DOI: 10.1093/hmg/ddae039] [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: 10/20/2023] [Revised: 02/03/2024] [Accepted: 03/01/2024] [Indexed: 03/22/2024] Open
Abstract
The dystrophin-glycoprotein complex (DGC) plays a crucial role in maintaining the structural integrity of the plasma membrane and the neuromuscular junction. In this study, we investigated the impact of the deficiency of α-dystrobrevin (αdbn), a component of the DGC, on the homeostasis of intracellular organelles, specifically mitochondria and the sarcoplasmic reticulum (SR). In αdbn deficient muscles, we observed a significant increase in the membrane-bound ATP synthase complex levels, a marker for mitochondria in oxidative muscle fiber types compared to wild-type. Furthermore, examination of muscle fibers deficient in αdbn using electron microscopy revealed profound alterations in the organization of mitochondria and the SR within certain myofibrils of muscle fibers. This included the formation of hyper-branched intermyofibrillar mitochondria with extended connections, an extensive network spanning several myofibrils, and a substantial increase in the number/density of subsarcolemmal mitochondria. Concurrently, in some cases, we observed significant structural alterations in mitochondria, such as cristae loss, fragmentation, swelling, and the formation of vacuoles and inclusions within the mitochondrial matrix cristae. Muscles deficient in αdbn also displayed notable alterations in the morphology of the SR, along with the formation of distinct anomalous concentric SR structures known as whorls. These whorls were prevalent in αdbn-deficient mice but were absent in wild-type muscles. These results suggest a crucial role of the DGC αdbn in regulating intracellular organelles, particularly mitochondria and the SR, within muscle cells. The remodeling of the SR and the formation of whorls may represent a novel mechanism of the unfolded protein response (UPR) in muscle cells.
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Affiliation(s)
- Saad O Malik
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, 4164 Biological Sciences Building, 1105 N. University Avenue, Ann Arbor, MI 48109, United States
| | - Alissa Wierenga
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, 4164 Biological Sciences Building, 1105 N. University Avenue, Ann Arbor, MI 48109, United States
| | - Chenlang Gao
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, 4164 Biological Sciences Building, 1105 N. University Avenue, Ann Arbor, MI 48109, United States
| | - Mohammed Akaaboune
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, 4164 Biological Sciences Building, 1105 N. University Avenue, Ann Arbor, MI 48109, United States
- Michigan Neuroscience Institute, University of Michigan, 205 Zina Pitcher Pl, Ann Arbor, MI 48109, United States
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2
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Ruparelia AA, Montandon M, Merriner J, Huang C, Wong SFL, Sonntag C, Hardee JP, Lynch GS, Miles LB, Siegel A, Hall TE, Schittenhelm RB, Currie PD. Atrogin-1 promotes muscle homeostasis by regulating levels of endoplasmic reticulum chaperone BiP. JCI Insight 2024; 9:e167578. [PMID: 38530354 PMCID: PMC11141880 DOI: 10.1172/jci.insight.167578] [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: 11/30/2022] [Accepted: 03/14/2024] [Indexed: 03/27/2024] Open
Abstract
Skeletal muscle wasting results from numerous pathological conditions affecting both the musculoskeletal and nervous systems. A unifying feature of these pathologies is the upregulation of members of the E3 ubiquitin ligase family, resulting in increased proteolytic degradation of target proteins. Despite the critical role of E3 ubiquitin ligases in regulating muscle mass, the specific proteins they target for degradation and the mechanisms by which they regulate skeletal muscle homeostasis remain ill-defined. Here, using zebrafish loss-of-function models combined with in vivo cell biology and proteomic approaches, we reveal a role of atrogin-1 in regulating the levels of the endoplasmic reticulum chaperone BiP. Loss of atrogin-1 resulted in an accumulation of BiP, leading to impaired mitochondrial dynamics and a subsequent loss in muscle fiber integrity. We further implicated a disruption in atrogin-1-mediated BiP regulation in the pathogenesis of Duchenne muscular dystrophy. We revealed that BiP was not only upregulated in Duchenne muscular dystrophy, but its inhibition using pharmacological strategies, or by upregulating atrogin-1, significantly ameliorated pathology in a zebrafish model of Duchenne muscular dystrophy. Collectively, our data implicate atrogin-1 and BiP in the pathogenesis of Duchenne muscular dystrophy and highlight atrogin-1's essential role in maintaining muscle homeostasis.
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Affiliation(s)
- Avnika A. Ruparelia
- Australian Regenerative Medicine Institute, Monash University, Clayton, Victoria, Australia
- Department of Anatomy and Physiology, School of Biomedical Sciences, Faculty of Medicine Dentistry and Health Sciences, and
- Centre for Muscle Research, Department of Anatomy and Physiology, University of Melbourne, Melbourne, Victoria, Australia
| | - Margo Montandon
- Australian Regenerative Medicine Institute, Monash University, Clayton, Victoria, Australia
| | - Jo Merriner
- Australian Regenerative Medicine Institute, Monash University, Clayton, Victoria, Australia
| | - Cheng Huang
- Monash Proteomics and Metabolomics Facility, Monash Biomedicine Discovery Institute, Monash University, Clayton, Victoria, Australia
| | - Siew Fen Lisa Wong
- Australian Regenerative Medicine Institute, Monash University, Clayton, Victoria, Australia
| | - Carmen Sonntag
- Australian Regenerative Medicine Institute, Monash University, Clayton, Victoria, Australia
| | - Justin P. Hardee
- Centre for Muscle Research, Department of Anatomy and Physiology, University of Melbourne, Melbourne, Victoria, Australia
| | - Gordon S. Lynch
- Centre for Muscle Research, Department of Anatomy and Physiology, University of Melbourne, Melbourne, Victoria, Australia
| | - Lee B. Miles
- Australian Regenerative Medicine Institute, Monash University, Clayton, Victoria, Australia
| | - Ashley Siegel
- Australian Regenerative Medicine Institute, Monash University, Clayton, Victoria, Australia
| | - Thomas E. Hall
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Queensland, Australia
| | - Ralf B. Schittenhelm
- Monash Proteomics and Metabolomics Facility, Monash Biomedicine Discovery Institute, Monash University, Clayton, Victoria, Australia
| | - Peter D. Currie
- Australian Regenerative Medicine Institute, Monash University, Clayton, Victoria, Australia
- EMBL Australia, Victorian Node, Monash University, Clayton, Victoria, Australia
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3
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Guglielmi V, Cheli M, Tonin P, Vattemi G. Sporadic Inclusion Body Myositis at the Crossroads between Muscle Degeneration, Inflammation, and Aging. Int J Mol Sci 2024; 25:2742. [PMID: 38473988 DOI: 10.3390/ijms25052742] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2023] [Revised: 02/19/2024] [Accepted: 02/22/2024] [Indexed: 03/14/2024] Open
Abstract
Sporadic inclusion body myositis (sIBM) is the most common muscle disease of older people and is clinically characterized by slowly progressive asymmetrical muscle weakness, predominantly affecting the quadriceps, deep finger flexors, and foot extensors. At present, there are no enduring treatments for this relentless disease that eventually leads to severe disability and wheelchair dependency. Although sIBM is considered a rare muscle disorder, its prevalence is certainly higher as the disease is often undiagnosed or misdiagnosed. The histopathological phenotype of sIBM muscle biopsy includes muscle fiber degeneration and endomysial lymphocytic infiltrates that mainly consist of cytotoxic CD8+ T cells surrounding nonnecrotic muscle fibers expressing MHCI. Muscle fiber degeneration is characterized by vacuolization and the accumulation of congophilic misfolded multi-protein aggregates, mainly in their non-vacuolated cytoplasm. Many players have been identified in sIBM pathogenesis, including environmental factors, autoimmunity, abnormalities of protein transcription and processing, the accumulation of several toxic proteins, the impairment of autophagy and the ubiquitin-proteasome system, oxidative and nitrative stress, endoplasmic reticulum stress, myonuclear degeneration, and mitochondrial dysfunction. Aging has also been proposed as a contributor to the disease. However, the interplay between these processes and the primary event that leads to the coexistence of autoimmune and degenerative changes is still under debate. Here, we outline our current understanding of disease pathogenesis, focusing on degenerative mechanisms, and discuss the possible involvement of aging.
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Affiliation(s)
- Valeria Guglielmi
- Cellular and Molecular Biology of Cancer Program, NCI-Designated Cancer Center, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037, USA
- Immunity and Pathogenesis Program, Infectious and Inflammatory Disease Center, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037, USA
| | - Marta Cheli
- Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, 37134 Verona, Italy
| | - Paola Tonin
- Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, 37134 Verona, Italy
| | - Gaetano Vattemi
- Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, 37134 Verona, Italy
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4
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Cantó-Santos J, Valls-Roca L, Tobías E, García-García FJ, Guitart-Mampel M, Esteve-Codina A, Martín-Mur B, Casado M, Artuch R, Solsona-Vilarrasa E, Fernandez-Checa JC, García-Ruiz C, Rentero C, Enrich C, Moreno-Lozano PJ, Milisenda JC, Cardellach F, Grau-Junyent JM, Garrabou G. Unravelling inclusion body myositis using a patient-derived fibroblast model. J Cachexia Sarcopenia Muscle 2023; 14:964-977. [PMID: 36860172 PMCID: PMC10067507 DOI: 10.1002/jcsm.13178] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Revised: 11/24/2022] [Accepted: 01/02/2023] [Indexed: 03/03/2023] Open
Abstract
BACKGROUND Inclusion body myositis (IBM) is an inflammatory myopathy clinically characterized by proximal and distal muscle weakness, with inflammatory infiltrates, rimmed vacuoles and mitochondrial changes in muscle histopathology. There is scarce knowledge on IBM aetiology, and non-established biomarkers or effective treatments are available, partly due to the lack of validated disease models. METHODS We have performed transcriptomics and functional validation of IBM muscle pathological hallmarks in fibroblasts from IBM patients (n = 14) and healthy controls (n = 12), paired by age and sex. The results comprise an mRNA-seq, together with functional inflammatory, autophagy, mitochondrial and metabolic changes between patients and controls. RESULTS Gene expression profile of IBM vs control fibroblasts revealed 778 differentially expressed genes (P-value adj < 0.05) related to inflammation, mitochondria, cell cycle regulation and metabolism. Functionally, an increased inflammatory profile was observed in IBM fibroblasts with higher supernatant cytokine secretion (three-fold increase). Autophagy was reduced considering basal protein mediators (18.4% reduced), time-course autophagosome formation (LC3BII 39% reduced, P-value < 0.05), and autophagosome microscopic evaluation. Mitochondria displayed reduced genetic content (by 33.9%, P-value < 0.05) and function (30.2%-decrease in respiration, 45.6%-decline in enzymatic activity (P-value < 0.001), 14.3%-higher oxidative stress, 135.2%-increased antioxidant defence (P-value < 0.05), 11.6%-reduced mitochondrial membrane potential (P-value < 0.05) and 42.8%-reduced mitochondrial elongation (P-value < 0.05)). In accordance, at the metabolite level, organic acid showed a 1.8-fold change increase, with conserved amino acid profile. Correlating to disease evolution, oxidative stress and inflammation emerge as potential markers of prognosis. CONCLUSIONS These findings confirm the presence of molecular disturbances in peripheral tissues from IBM patients and prompt patients' derived fibroblasts as a promising disease model, which may eventually be exported to other neuromuscular disorders. We additionally identify new molecular players in IBM associated with disease progression, setting the path to deepen in disease aetiology, in the identification of novel biomarkers or in the standardization of biomimetic platforms to assay new therapeutic strategies for preclinical studies.
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Affiliation(s)
- Judith Cantó-Santos
- Muscle Research and Mitochondrial Function Lab, Centre de Recerca Biomèdica CELLEX - Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS) and Faculty of Medicine and Health Sciences, University of Barcelona, Barcelona, Spain.,Department of Internal Medicine, Hospital Clinic of Barcelona, Barcelona, Spain.,CIBERER-Spanish Biomedical Research Centre in Rare Diseases, Madrid, Spain
| | - Laura Valls-Roca
- Muscle Research and Mitochondrial Function Lab, Centre de Recerca Biomèdica CELLEX - Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS) and Faculty of Medicine and Health Sciences, University of Barcelona, Barcelona, Spain.,Department of Internal Medicine, Hospital Clinic of Barcelona, Barcelona, Spain.,CIBERER-Spanish Biomedical Research Centre in Rare Diseases, Madrid, Spain
| | - Ester Tobías
- Muscle Research and Mitochondrial Function Lab, Centre de Recerca Biomèdica CELLEX - Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS) and Faculty of Medicine and Health Sciences, University of Barcelona, Barcelona, Spain.,Department of Internal Medicine, Hospital Clinic of Barcelona, Barcelona, Spain.,CIBERER-Spanish Biomedical Research Centre in Rare Diseases, Madrid, Spain
| | - Francesc Josep García-García
- Muscle Research and Mitochondrial Function Lab, Centre de Recerca Biomèdica CELLEX - Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS) and Faculty of Medicine and Health Sciences, University of Barcelona, Barcelona, Spain.,Department of Internal Medicine, Hospital Clinic of Barcelona, Barcelona, Spain.,CIBERER-Spanish Biomedical Research Centre in Rare Diseases, Madrid, Spain
| | - Mariona Guitart-Mampel
- Muscle Research and Mitochondrial Function Lab, Centre de Recerca Biomèdica CELLEX - Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS) and Faculty of Medicine and Health Sciences, University of Barcelona, Barcelona, Spain.,Department of Internal Medicine, Hospital Clinic of Barcelona, Barcelona, Spain.,CIBERER-Spanish Biomedical Research Centre in Rare Diseases, Madrid, Spain
| | - Anna Esteve-Codina
- CNAG-CRG, Centre for Genomic Regulation, Barcelona Institute of Science and Technology, Barcelona, Spain.,Universitat Pompeu Fabra (UPF), Barcelona, Spain
| | - Beatriz Martín-Mur
- CNAG-CRG, Centre for Genomic Regulation, Barcelona Institute of Science and Technology, Barcelona, Spain
| | - Mercedes Casado
- CIBERER-Spanish Biomedical Research Centre in Rare Diseases, Madrid, Spain.,Department of Clinical Biochemistry, Institut de Recerca Sant Joan de Déu; Esplugues de Llobregat, Barcelona, Spain
| | - Rafael Artuch
- CIBERER-Spanish Biomedical Research Centre in Rare Diseases, Madrid, Spain.,Department of Clinical Biochemistry, Institut de Recerca Sant Joan de Déu; Esplugues de Llobregat, Barcelona, Spain
| | - Estel Solsona-Vilarrasa
- Department of Cell Death and Proliferation, Institute of Biomedical Research of Barcelona (IIBB-CSIC), Liver Unit-HCB-IDIBAPS, Barcelona, Spain.,CIBEREHD-Spanish Biomedical Research Centre in Hepatic and Digestive Diseases, Madrid, Spain
| | - José Carlos Fernandez-Checa
- Department of Cell Death and Proliferation, Institute of Biomedical Research of Barcelona (IIBB-CSIC), Liver Unit-HCB-IDIBAPS, Barcelona, Spain.,CIBEREHD-Spanish Biomedical Research Centre in Hepatic and Digestive Diseases, Madrid, Spain
| | - Carmen García-Ruiz
- Department of Cell Death and Proliferation, Institute of Biomedical Research of Barcelona (IIBB-CSIC), Liver Unit-HCB-IDIBAPS, Barcelona, Spain.,CIBEREHD-Spanish Biomedical Research Centre in Hepatic and Digestive Diseases, Madrid, Spain
| | - Carles Rentero
- Department of Biomedicine, Cell Biology Unit, CELLEX-IDIBAPS, Faculty of Medicine and Health Sciences, University of Barcelona, Barcelona, Spain
| | - Carlos Enrich
- Department of Biomedicine, Cell Biology Unit, CELLEX-IDIBAPS, Faculty of Medicine and Health Sciences, University of Barcelona, Barcelona, Spain
| | - Pedro J Moreno-Lozano
- Muscle Research and Mitochondrial Function Lab, Centre de Recerca Biomèdica CELLEX - Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS) and Faculty of Medicine and Health Sciences, University of Barcelona, Barcelona, Spain.,Department of Internal Medicine, Hospital Clinic of Barcelona, Barcelona, Spain.,CIBERER-Spanish Biomedical Research Centre in Rare Diseases, Madrid, Spain
| | - José César Milisenda
- Muscle Research and Mitochondrial Function Lab, Centre de Recerca Biomèdica CELLEX - Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS) and Faculty of Medicine and Health Sciences, University of Barcelona, Barcelona, Spain.,Department of Internal Medicine, Hospital Clinic of Barcelona, Barcelona, Spain.,CIBERER-Spanish Biomedical Research Centre in Rare Diseases, Madrid, Spain
| | - Francesc Cardellach
- Muscle Research and Mitochondrial Function Lab, Centre de Recerca Biomèdica CELLEX - Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS) and Faculty of Medicine and Health Sciences, University of Barcelona, Barcelona, Spain.,Department of Internal Medicine, Hospital Clinic of Barcelona, Barcelona, Spain.,CIBERER-Spanish Biomedical Research Centre in Rare Diseases, Madrid, Spain
| | - Josep M Grau-Junyent
- Muscle Research and Mitochondrial Function Lab, Centre de Recerca Biomèdica CELLEX - Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS) and Faculty of Medicine and Health Sciences, University of Barcelona, Barcelona, Spain.,Department of Internal Medicine, Hospital Clinic of Barcelona, Barcelona, Spain.,CIBERER-Spanish Biomedical Research Centre in Rare Diseases, Madrid, Spain
| | - Glòria Garrabou
- Muscle Research and Mitochondrial Function Lab, Centre de Recerca Biomèdica CELLEX - Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS) and Faculty of Medicine and Health Sciences, University of Barcelona, Barcelona, Spain.,Department of Internal Medicine, Hospital Clinic of Barcelona, Barcelona, Spain.,CIBERER-Spanish Biomedical Research Centre in Rare Diseases, Madrid, Spain
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5
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Yadav R, Devi SS, Oswalia J, Ramalingam S, Arya R. Role of HSP70 chaperone in protein aggregate phenomenon of GNE mutant cells: Therapeutic lead for GNE Myopathy. Int J Biochem Cell Biol 2022; 149:106258. [PMID: 35777599 DOI: 10.1016/j.biocel.2022.106258] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Revised: 06/04/2022] [Accepted: 06/25/2022] [Indexed: 10/17/2022]
Abstract
Limited treatment options and research in understanding the pathomechanisms of rare diseases has raised concerns about their therapeutic development. One such poorly understood ultra-rare neuromuscular disorder is GNE Myopathy (GNEM) which is caused due to mutation in key sialic acid biosynthetic enzyme, GNE. Treatment with sialic acid or its derivatives/precursors slows the disease progression, but curative strategies need to be explored further. Pathologically, muscle biopsy samples of GNEM patients reveal rimmed vacuole formation due to aggregation of β-amyloid, Tau, presenilin proteins with unknown mechanism. The present study aims to understand the mechanism of protein aggregate formation in GNE mutant cells to decipher role of chaperones in disease phenotype. The pathologically relevant GNE mutations expressed as recombinant proteins in HEK cells was used as a model system for GNEM to estimate extent of protein aggregation. We identified HSP70, a chaperone, as binding partner of GNE. Downregulation of HSP70 with altered BAG3, JNK, BAX expression levels was observed in GNE mutant cells. The cell apoptosis was observed in GNE mutation specific manner. An activator of HSP70 chaperone, BGP-15, rescued the phenotypic defects due to GNE mutation, thereby, reducing protein aggregation significantly. The results were further validated in rat skeletal muscle cell lines carrying single Gne allele. Our study suggests that HSP70 activators can be a promising therapeutic target in the treatment of ultra-rare GNE Myopathy disease.
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Affiliation(s)
- Rashmi Yadav
- School of Biotechnology, Jawaharlal Nehru University, New Delhi 110067, India.
| | | | - Jyoti Oswalia
- School of Biotechnology, Jawaharlal Nehru University, New Delhi 110067, India.
| | | | - Ranjana Arya
- School of Biotechnology, Jawaharlal Nehru University, New Delhi 110067, India; Special Center for Systems Medicine, Jawaharlal Nehru University, New Delhi 110067, India.
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6
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The role of amyloid β in the pathological mechanism of GNE myopathy. Neurol Sci 2022; 43:6309-6321. [PMID: 35904705 PMCID: PMC9616754 DOI: 10.1007/s10072-022-06301-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Accepted: 07/21/2022] [Indexed: 11/18/2022]
Abstract
GNE myopathy is a hereditary muscle disorder characterized by muscle atrophy and weakness initially involving the lower distal extremities. The treatment of GNE myopathy mainly focuses on a sialic acid deficiency caused by a mutation in the GNE gene, but it has not achieved the expected effect. The main pathological features of GNE myopathy are myofiber atrophy and rimmed vacuoles, including accumulation of amyloid β, which is mainly found in atrophic muscle fibers. Although the role of amyloid β and other misfolded proteins on the nervous system has been widely recognized, the cause and process of the formation of amyloid β in the pathological process of GNE myopathy are unclear. In addition, amyloid β has been reported to be linked to quality control mechanisms of proteins, such as molecular chaperones, the ubiquitin–proteasome system, and the autophagy-lysosome system. Herein, we summarize the possible reasons for amyloid β deposition and illustrate amyloid β-mediated events in the cells and their role in muscle atrophy in GNE myopathy. This review represents an overview of amyloid β and GNE myopathy that could help identify a potential mechanism and thereby a plausible therapeutic for the disease.
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7
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Gallot YS, Bohnert KR. Confounding Roles of ER Stress and the Unfolded Protein Response in Skeletal Muscle Atrophy. Int J Mol Sci 2021; 22:2567. [PMID: 33806433 PMCID: PMC7961896 DOI: 10.3390/ijms22052567] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Revised: 02/26/2021] [Accepted: 03/03/2021] [Indexed: 12/12/2022] Open
Abstract
Skeletal muscle is an essential organ, responsible for many physiological functions such as breathing, locomotion, postural maintenance, thermoregulation, and metabolism. Interestingly, skeletal muscle is a highly plastic tissue, capable of adapting to anabolic and catabolic stimuli. Skeletal muscle contains a specialized smooth endoplasmic reticulum (ER), known as the sarcoplasmic reticulum, composed of an extensive network of tubules. In addition to the role of folding and trafficking proteins within the cell, this specialized organelle is responsible for the regulated release of calcium ions (Ca2+) into the cytoplasm to trigger a muscle contraction. Under various stimuli, such as exercise, hypoxia, imbalances in calcium levels, ER homeostasis is disturbed and the amount of misfolded and/or unfolded proteins accumulates in the ER. This accumulation of misfolded/unfolded protein causes ER stress and leads to the activation of the unfolded protein response (UPR). Interestingly, the role of the UPR in skeletal muscle has only just begun to be elucidated. Accumulating evidence suggests that ER stress and UPR markers are drastically induced in various catabolic stimuli including cachexia, denervation, nutrient deprivation, aging, and disease. Evidence indicates some of these molecules appear to be aiding the skeletal muscle in regaining homeostasis whereas others demonstrate the ability to drive the atrophy. Continued investigations into the individual molecules of this complex pathway are necessary to fully understand the mechanisms.
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Affiliation(s)
- Yann S. Gallot
- LBEPS, Univ Evry, IRBA, Université Paris Saclay, 91025 Evry, France
| | - Kyle R. Bohnert
- Kinesiology Department, St. Ambrose University, Davenport, IA 52803, USA
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8
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Abstract
Autophagy is an evolutionarily conserved catabolic process that targets different types of cytoplasmic cargo (such as bulk cytoplasm, damaged cellular organelles, and misfolded protein aggregates) for lysosomal degradation. Autophagy is activated in response to biological stress and also plays a critical role in the maintenance of normal cellular homeostasis; the latter function is particularly important for the integrity of postmitotic, metabolically active tissues, such as skeletal muscle. Through impairment of muscle homeostasis, autophagy dysfunction contributes to the pathogenesis of many different skeletal myopathies; the observed autophagy defects differ from disease to disease but have been shown to involve all steps of the autophagic cascade (from induction to lysosomal cargo degradation) and to impair both bulk and selective autophagy. To highlight the molecular and cellular mechanisms that are shared among different myopathies with deficient autophagy, these disorders are discussed based on the nature of the underlying autophagic defect rather than etiology or clinical presentation.
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Affiliation(s)
- Marta Margeta
- Department of Pathology, University of California, San Francisco, California 94143, USA;
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9
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Fischer N, Preuße C, Radke J, Pehl D, Allenbach Y, Schneider U, Feist E, von Casteleyn V, Hahn K, Ruck T, Meuth SG, Goebel HH, Graf R, Mammen A, Benveniste O, Stenzel W. Sequestosome-1 (p62) expression reveals chaperone-assisted selective autophagy in immune-mediated necrotizing myopathies. Brain Pathol 2019; 30:261-271. [PMID: 31376301 PMCID: PMC8018061 DOI: 10.1111/bpa.12772] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2019] [Accepted: 07/26/2019] [Indexed: 12/21/2022] Open
Abstract
Diffuse myofiber necrosis in the context of inflammatory myopathy is the hallmark of immune‐mediated necrotizing myopathy (IMNM). We have previously shown that skeletal muscle fibers of IMNM patients may display nonrimmed vacuoles and sarcoplasmic irregularities. The dysfunctional chaperone activity has been linked to the defective assembly of skeletal muscle proteins and their degradation via lysosomes, autophagy and the proteasomal machinery. This study was undertaken to highlight a chaperone‐assisted selective autophagy (CASA) pathway, functionally involved in protein homeostasis, cell stress and the immune response in skeletal muscle of IMNM patients. Skeletal muscle biopsies from 54 IMNM patients were analyzed by immunostaining, as well as by qPCR. Eight biopsies of sIBM patients served as pathological controls, and eight biopsies of nondisease control subjects were included. Alteration of autophagy was detectable in all IMNM biopsy samples highlighted via a diffuse sarcoplasmic staining pattern by p62 and LC3 independent of vacuoles. This pattern was at variance with the coarse focal staining pattern mostly confined to rimmed vacuoles in sIBM. Colocalization of p62 with the chaperone proteins HSP70 and αB‐crystalline points to the specific targeting of misfolded proteins to the CASA machinery. Bcl2‐associated athanogene 3 (BAG3) positivity of these fibers emphasizes the selectivity of autophagy processes and these fibers also express MHC class I sarcolemma. Expression of genes involved in autophagy and endoplasmic reticulum (ER) stress pathways studied here is significantly upregulated in IMNM. We highlight that vacuoles without sarcolemmal features may arise in IMNM muscle biopsies, and they must not be confounded with sIBM‐specific vacuoles. Further, we show the activation of selective autophagy and emphasize the role of chaperones in this context. CASA occurs in IMNM muscle, and specific molecular pathways of autophagy differ from the ones in sIBM, with p62 as a unique identifier of this process.
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Affiliation(s)
- Norina Fischer
- Department of Neuropathology, Charité - Universitätsmedizin, Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health (BIH), Berlin, Germany
| | - Corinna Preuße
- Department of Neuropathology, Charité - Universitätsmedizin, Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health (BIH), Berlin, Germany
| | - Josefine Radke
- Department of Neuropathology, Charité - Universitätsmedizin, Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health (BIH), Berlin, Germany
| | - Debora Pehl
- Oxford University Hospitals Foundation Trust, Neuropathology & Ocular Pathology Department, John Radcliffe Hospital, Oxford, OX3 9DU, UK
| | - Yves Allenbach
- Assistance Public-Hôpitaux de Paris, Sorbonne-Université, INSERM, UMR974, Department of Internal Medicine and Clinical Immunology, Pitié-Salpêtrière University Hospital, Paris, France
| | - Udo Schneider
- Department of Rheumatology, Charité - Universitätsmedizin, Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health (BIH), Berlin, Germany
| | - Eugen Feist
- Department of Rheumatology, Charité - Universitätsmedizin, Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health (BIH), Berlin, Germany
| | - Vincent von Casteleyn
- Department of Rheumatology, Charité - Universitätsmedizin, Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health (BIH), Berlin, Germany
| | - Katrin Hahn
- Department of Neurology, Charité - Universitätsmedizin, Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health (BIH), Berlin, Germany
| | - Tobias Ruck
- Department of Neurology with Institute for Translational Neurology, University Hospital Münster, Münster, Germany
| | - Sven G Meuth
- Department of Neurology with Institute for Translational Neurology, University Hospital Münster, Münster, Germany
| | - Hans-Hilmar Goebel
- Department of Neuropathology, Charité - Universitätsmedizin, Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health (BIH), Berlin, Germany
| | - Rose Graf
- National Institutes of Health, 9000 Rockville Pike, Building 50, Room 1505, Bethesda, MD, 20892, USA
| | - Andrew Mammen
- National Institutes of Health, 9000 Rockville Pike, Building 50, Room 1505, Bethesda, MD, 20892, USA
| | - Olivier Benveniste
- Assistance Public-Hôpitaux de Paris, Sorbonne-Université, INSERM, UMR974, Department of Internal Medicine and Clinical Immunology, Pitié-Salpêtrière University Hospital, Paris, France
| | - Werner Stenzel
- Department of Neuropathology, Charité - Universitätsmedizin, Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health (BIH), Berlin, Germany.,Leibniz ScienceCampus Chronic Inflammation, Berlin, Germany
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10
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Afroze D, Kumar A. ER stress in skeletal muscle remodeling and myopathies. FEBS J 2019; 286:379-398. [PMID: 29239106 PMCID: PMC6002870 DOI: 10.1111/febs.14358] [Citation(s) in RCA: 70] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Revised: 11/24/2017] [Accepted: 12/07/2017] [Indexed: 12/18/2022]
Abstract
Skeletal muscle is a highly plastic tissue in the human body that undergoes extensive adaptation in response to environmental cues, such as physical activity, metabolic perturbation, and disease conditions. The endoplasmic reticulum (ER) plays a pivotal role in protein folding and calcium homeostasis in many mammalian cell types, including skeletal muscle. However, overload of misfolded or unfolded proteins in the ER lumen cause stress, which results in the activation of a signaling network called the unfolded protein response (UPR). The UPR is initiated by three ER transmembrane sensors: protein kinase R-like endoplasmic reticulum kinase, inositol-requiring protein 1α, and activating transcription factor 6. The UPR restores ER homeostasis through modulating the rate of protein synthesis and augmenting the gene expression of many ER chaperones and regulatory proteins. However, chronic heightened ER stress can also lead to many pathological consequences including cell death. Accumulating evidence suggests that ER stress-induced UPR pathways play pivotal roles in the regulation of skeletal muscle mass and metabolic function in multiple conditions. They have also been found to be activated in skeletal muscle under catabolic states, degenerative muscle disorders, and various types of myopathies. In this article, we have discussed the recent advancements toward understanding the role and mechanisms through which ER stress and individual arms of the UPR regulate skeletal muscle physiology and pathology.
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Affiliation(s)
- Dil Afroze
- Department of Anatomical Sciences and Neurobiology, University of Louisville School of Medicine, Louisville, KY 40202, USA
- Department of Immunology and Molecular Medicine, Sher-I-Kashmir Institute of Medical Sciences, Soura, Srinagar, Kashmir, INDIA
| | - Ashok Kumar
- Department of Anatomical Sciences and Neurobiology, University of Louisville School of Medicine, Louisville, KY 40202, USA
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11
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Devi S, Yadav R, Chanana P, Arya R. Fighting the Cause of Alzheimer's and GNE Myopathy. Front Neurosci 2018; 12:669. [PMID: 30374284 PMCID: PMC6196280 DOI: 10.3389/fnins.2018.00669] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Accepted: 09/06/2018] [Indexed: 12/12/2022] Open
Abstract
Age is the common risk factor for both neurodegenerative and neuromuscular diseases. Alzheimer disease (AD), a neurodegenerative disorder, causes dementia with age progression while GNE myopathy (GNEM), a neuromuscular disorder, causes muscle degeneration and loss of muscle motor movement with age. Individuals with mutations in presenilin or amyloid precursor protein (APP) gene develop AD while mutations in GNE (UDP N-acetylglucosamine 2 epimerase/N-acetyl Mannosamine kinase), key sialic acid biosynthesis enzyme, cause GNEM. Although GNEM is characterized with degeneration of muscle cells, it is shown to have similar disease hallmarks like aggregation of Aβ and accumulation of phosphorylated tau and other misfolded proteins in muscle cell similar to AD. Similar impairment in cellular functions have been reported in both disorders such as disruption of cytoskeletal network, changes in glycosylation pattern, mitochondrial dysfunction, oxidative stress, upregulation of chaperones, unfolded protein response in ER, autophagic vacuoles, cell death, and apoptosis. Interestingly, AD and GNEM are the two diseases with similar phenotypic condition affecting neuron and muscle, respectively, resulting in entirely different pathology. This review represents a comparative outlook of AD and GNEM that could lead to target common mechanism to find a plausible therapeutic for both the diseases.
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Affiliation(s)
| | - Rashmi Yadav
- School of Biotechnology, Jawaharlal Nehru University, New Delhi, India
| | - Pratibha Chanana
- School of Biotechnology, Jawaharlal Nehru University, New Delhi, India
| | - Ranjana Arya
- School of Biotechnology, Jawaharlal Nehru University, New Delhi, India
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12
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Naddaf E, Barohn RJ, Dimachkie MM. Inclusion Body Myositis: Update on Pathogenesis and Treatment. Neurotherapeutics 2018; 15:995-1005. [PMID: 30136253 PMCID: PMC6277289 DOI: 10.1007/s13311-018-0658-8] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Inclusion body myositis is the most common acquired myopathy after the age of 50. It is characterized by progressive asymmetric weakness predominantly affecting the quadriceps and/or finger flexors. Loss of ambulation and dysphagia are major complications of the disease. Inclusion body myositis can be associated with cytosolic 5'-nucleotidase 1A antibodies. Muscle biopsy usually shows inflammatory cells surrounding and invading non-necrotic muscle fibers, rimmed vacuoles, congophilic inclusions, and protein aggregates. Disease pathogenesis remains poorly understood and consists of an interplay between inflammatory and degenerative pathways. Antigen-driven, clonally restricted, cytotoxic T cells represent a main feature of the inflammatory component, whereas abnormal protein homeostasis with protein misfolding, aggregation, and dysfunctional protein disposal is the hallmark of the degenerative component. Inclusion body myositis remains refractory to treatment. Better understanding of the disease pathogenesis led to the identification of novel therapeutic targets, addressing both the inflammatory and degenerative pathways.
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Affiliation(s)
- Elie Naddaf
- Neuromuscular Medicine Division, Department of Neurology, Mayo Clinic, Rochester, Minnesota, 55905, USA
| | - Richard J Barohn
- Neuromuscular Medicine Division, Department of Neurology, University of Kansas Medical Center, Kansas City, Kansas, 66103, USA
| | - Mazen M Dimachkie
- Neuromuscular Medicine Division, Department of Neurology, University of Kansas Medical Center, Kansas City, Kansas, 66103, USA.
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13
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Pogoryelova O, González Coraspe JA, Nikolenko N, Lochmüller H, Roos A. GNE myopathy: from clinics and genetics to pathology and research strategies. Orphanet J Rare Dis 2018; 13:70. [PMID: 29720219 PMCID: PMC5930817 DOI: 10.1186/s13023-018-0802-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2017] [Accepted: 04/09/2018] [Indexed: 01/07/2023] Open
Abstract
GNE myopathy is an ultra-rare autosomal recessive disease, which starts as a distal muscle weakness and ultimately leads to a wheelchair bound state. Molecular research and animal modelling significantly moved forward understanding of GNE myopathy mechanisms and suggested therapeutic interventions to alleviate the symptoms. Multiple therapeutic attempts are being made to supplement sialic acid depleted in GNE myopathy muscle cells. Translational research field provided valuable knowledge through natural history studies, patient registries and clinical trial, which significantly contributed to bringing forward an era of GNE myopathy treatment. In this review, we are summarising current GNE myopathy, scientific trends and open questions, which would be of significant interest for a wide neuromuscular diseases community.
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Affiliation(s)
- Oksana Pogoryelova
- Institute of Genetic Medicine, International Centre for Life, Central Parkway, Newcastle upon Tyne, UK
| | | | - Nikoletta Nikolenko
- Institute of Genetic Medicine, International Centre for Life, Central Parkway, Newcastle upon Tyne, UK
| | - Hanns Lochmüller
- Institute of Genetic Medicine, International Centre for Life, Central Parkway, Newcastle upon Tyne, UK.,Present Address: Department of Neuropediatrics and Muscle Disorders, Faculty of Medicine, Medical Center - University of Freiburg, Freiburg, Germany.,Centro Nacional de Análisis Genómico, Center for Genomic Regulation (CNAG-CRG), Barcelona Institute of Science and Technology (BIST), Barcelona, Catalonia, Spain
| | - Andreas Roos
- Leibniz-Institut für Analytische Wissenschaften - ISAS - e.V, Biomedical Research Department, Otto-Hahn-Str. 6b, 44227, Dortmund, Germany.
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14
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Endoplasmic Reticulum Stress Induces Myostatin High Molecular Weight Aggregates and Impairs Mature Myostatin Secretion. Mol Neurobiol 2018; 55:8355-8373. [PMID: 29546591 PMCID: PMC6153721 DOI: 10.1007/s12035-018-0997-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2017] [Accepted: 03/07/2018] [Indexed: 01/08/2023]
Abstract
Sporadic inclusion body myositis (sIBM) is the most prevalent acquired muscle disorder in the elderly with no defined etiology or effective therapy. Endoplasmic reticulum stress and deposition of myostatin, a secreted negative regulator of muscle growth, have been implicated in disease pathology. The myostatin signaling pathway has emerged as a major target for symptomatic treatment of muscle atrophy. Here, we systematically analyzed the maturation and secretion of myostatin precursor MstnPP and its metabolites in a human muscle cell line. We find that increased MsntPP protein levels induce ER stress. MstnPP metabolites were predominantly retained within the endoplasmic reticulum (ER), also evident in sIBM histology. MstnPP cleavage products formed insoluble high molecular weight aggregates, a process that was aggravated by experimental ER stress. Importantly, ER stress also impaired secretion of mature myostatin. Reduced secretion and aggregation of MstnPP metabolites were not simply caused by overexpression, as both events were also observed in wildtype cells under ER stress. It is tempting to speculate that reduced circulating myostatin growth factor could be one explanation for the poor clinical efficacy of drugs targeting the myostatin pathway in sIBM.
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15
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Bohnert KR, McMillan JD, Kumar A. Emerging roles of ER stress and unfolded protein response pathways in skeletal muscle health and disease. J Cell Physiol 2017; 233:67-78. [PMID: 28177127 DOI: 10.1002/jcp.25852] [Citation(s) in RCA: 124] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Accepted: 02/07/2017] [Indexed: 12/17/2022]
Abstract
Skeletal muscle is the most abundant tissue in the human body and can adapt its mass as a consequence of physical activity, metabolism, growth factors, and disease conditions. Skeletal muscle contains an extensive network of endoplasmic reticulum (ER), called sarcoplasmic reticulum, which plays an important role in the regulation of proteostasis and calcium homeostasis. In many cell types, environmental and genetic factors that disrupt ER function cause an accumulation of misfolded and unfolded proteins in the ER lumen that ultimately leads to ER stress. To alleviate the stress and restore homeostasis, the ER activates a signaling network called the unfolded protein response (UPR). The UPR has three arms, which regulate protein synthesis and expression of many ER chaperone and regulatory proteins. However, the role of individual UPR pathways in skeletal muscle has just begun to be investigated. Recent studies suggest that UPR pathways play pivotal roles in muscle stem cell homeostasis, myogenic differentiation, and regeneration of injured skeletal muscle. Moreover, markers of ER stress and the UPR are activated in skeletal muscle in diverse conditions such as exercise, denervation, starvation, high fat diet, cancer cachexia, and aging. Accumulating evidence also suggests that ER stress may have important roles in the pathogenesis of inflammatory myopathies and genetic muscle disorders. The purpose of this review article is to discuss the role and potential mechanisms by which ER stress and the individual arms of the UPR regulate skeletal muscle formation, plasticity, and function in various physiological and pathophysiological conditions.
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Affiliation(s)
- Kyle R Bohnert
- Department of Anatomical Sciences Neurobiology, University of Louisville School of Medicine, Louisville, Kentucky
| | - Joseph D McMillan
- Department of Anatomical Sciences Neurobiology, University of Louisville School of Medicine, Louisville, Kentucky
| | - Ashok Kumar
- Department of Anatomical Sciences Neurobiology, University of Louisville School of Medicine, Louisville, Kentucky
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16
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Needham M, Mastaglia F. Advances in inclusion body myositis: genetics, pathogenesis and clinical aspects. Expert Opin Orphan Drugs 2017. [DOI: 10.1080/21678707.2017.1318056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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17
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Amici DR, Pinal-Fernandez I, Mázala DAG, Lloyd TE, Corse AM, Christopher-Stine L, Mammen AL, Chin ER. Calcium dysregulation, functional calpainopathy, and endoplasmic reticulum stress in sporadic inclusion body myositis. Acta Neuropathol Commun 2017; 5:24. [PMID: 28330496 PMCID: PMC5363023 DOI: 10.1186/s40478-017-0427-7] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Accepted: 03/12/2017] [Indexed: 01/08/2023] Open
Abstract
Sporadic inclusion body myositis (IBM) is the most common primary myopathy in the elderly, but its pathoetiology is still unclear. Perturbed myocellular calcium (Ca2+) homeostasis can exacerbate many of the factors proposed to mediate muscle degeneration in IBM, such as mitochondrial dysfunction, protein aggregation, and endoplasmic reticulum stress. Ca2+ dysregulation may plausibly be initiated in IBM by immune-mediated membrane damage and/or abnormally accumulating proteins, but no studies to date have investigated Ca2+ regulation in IBM patients. We first investigated protein expression via immunoblot in muscle biopsies from IBM, dermatomyositis, and non-myositis control patients, identifying several differentially expressed Ca2+-regulatory proteins in IBM. Next, we investigated the Ca2+-signaling transcriptome by RNA-seq, finding 54 of 183 (29.5%) genes from an unbiased list differentially expressed in IBM vs. controls. Using an established statistical approach to relate genes with causal transcription networks, Ca2+ abundance was considered a significant upstream regulator of observed whole-transcriptome changes. Post-hoc analyses of Ca2+-regulatory mRNA and protein data indicated a lower protein to transcript ratio in IBM vs. controls, which we hypothesized may relate to increased Ca2+-dependent proteolysis and decreased protein translation. Supporting this hypothesis, we observed robust (4-fold) elevation in the autolytic activation of a Ca2+-activated protease, calpain-1, as well as increased signaling for translational attenuation (eIF2α phosphorylation) downstream of the unfolded protein response. Finally, in IBM samples we observed mRNA and protein under-expression of calpain-3, the skeletal muscle-specific calpain, which broadly supports proper Ca2+ homeostasis. Together, these data provide novel insight into mechanisms by which intracellular Ca2+ regulation is perturbed in IBM and offer evidence of pathological downstream effects.
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18
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Mitochondrial DNA disturbances and deregulated expression of oxidative phosphorylation and mitochondrial fusion proteins in sporadic inclusion body myositis. Clin Sci (Lond) 2016; 130:1741-51. [PMID: 27413019 DOI: 10.1042/cs20160080] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Accepted: 07/13/2016] [Indexed: 12/11/2022]
Abstract
Sporadic inclusion body myositis (sIBM) is one of the most common myopathies in elderly people. Mitochondrial abnormalities at the histological level are present in these patients. We hypothesize that mitochondrial dysfunction may play a role in disease aetiology. We took the following measurements of muscle and peripheral blood mononuclear cells (PBMCs) from 30 sIBM patients and 38 age- and gender-paired controls: mitochondrial DNA (mtDNA) deletions, amount of mtDNA and mtRNA, mitochondrial protein synthesis, mitochondrial respiratory chain (MRC) complex I and IV enzymatic activity, mitochondrial mass, oxidative stress and mitochondrial dynamics (mitofusin 2 and optic atrophy 1 levels). Depletion of mtDNA was present in muscle from sIBM patients and PBMCs showed deregulated expression of mitochondrial proteins in oxidative phosphorylation. MRC complex IV/citrate synthase activity was significantly decreased in both tissues and mitochondrial dynamics were affected in muscle. Depletion of mtDNA was significantly more severe in patients with mtDNA deletions, which also presented deregulation of mitochondrial fusion proteins. Imbalance in mitochondrial dynamics in muscle was associated with increased mitochondrial genetic disturbances (both depletion and deletions), demonstrating that proper mitochondrial turnover is essential for mitochondrial homoeostasis and muscle function in these patients.
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