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Kirby TJ, Zahr HC, Fong EHH, Lammerding J. Eliminating elevated p53 signaling fails to rescue skeletal muscle defects or extend survival in lamin A/C-deficient mice. Cell Death Discov 2024; 10:245. [PMID: 38778055 PMCID: PMC11111808 DOI: 10.1038/s41420-024-01998-1] [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: 03/03/2024] [Revised: 04/25/2024] [Accepted: 04/29/2024] [Indexed: 05/25/2024] Open
Abstract
Lamins A and C, encoded by the LMNA gene, are nuclear intermediate filaments that provide structural support to the nucleus and contribute to chromatin organization and transcriptional regulation. LMNA mutations cause muscular dystrophies, dilated cardiomyopathy, and other diseases. The mechanisms by which many LMNA mutations result in muscle-specific diseases have remained elusive, presenting a major hurdle in the development of effective treatments. Previous studies using striated muscle laminopathy mouse models found that cytoskeletal forces acting on mechanically fragile Lmna-mutant nuclei led to transient nuclear envelope rupture, extensive DNA damage, and activation of DNA damage response (DDR) pathways in skeletal muscle cells in vitro and in vivo. Furthermore, hearts of Lmna mutant mice have elevated activation of the tumor suppressor protein p53, a central regulator of DDR signaling. We hypothesized that elevated p53 activation could present a pathogenic mechanism in striated muscle laminopathies, and that eliminating p53 activation could improve muscle function and survival in laminopathy mouse models. Supporting a pathogenic function of p53 activation in muscle, stabilization of p53 was sufficient to reduce contractility and viability in wild-type muscle cells in vitro. Using three laminopathy models, we found that increased p53 activity in Lmna-mutant muscle cells primarily resulted from mechanically induced damage to the myonuclei, and not from altered transcriptional regulation due to loss of lamin A/C expression. However, global deletion of p53 in a severe muscle laminopathy model did not reduce the disease phenotype or increase survival, indicating that additional drivers of disease must contribute to the disease pathogenesis.
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Affiliation(s)
- Tyler J Kirby
- Department of Physiology, Amsterdam Cardiovascular Sciences, Amsterdam Movement Sciences, Amsterdam UMC location Vrije Universiteit Amsterdam, Amsterdam, Netherlands.
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY, USA.
| | - Hind C Zahr
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY, USA
- Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY, USA
| | - Ern Hwei Hannah Fong
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY, USA
- Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY, USA
| | - Jan Lammerding
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY, USA.
- Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY, USA.
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2
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Crombie EM, Kim S, Adamson S, Dong H, Lu TC, Wu Y, Wu Y, Levy Y, Stimple N, Lam WMR, Hey HWD, Withers DJ, Hsu AL, Bay BH, Ochala J, Tsai SY. Activation of eIF4E-binding-protein-1 rescues mTORC1-induced sarcopenia by expanding lysosomal degradation capacity. J Cachexia Sarcopenia Muscle 2023; 14:198-213. [PMID: 36398408 PMCID: PMC9891956 DOI: 10.1002/jcsm.13121] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Revised: 09/01/2022] [Accepted: 10/10/2022] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Chronic mTORC1 activation in skeletal muscle is linked with age-associated loss of muscle mass and strength, known as sarcopenia. Genetic activation of mTORC1 by conditionally ablating mTORC1 upstream inhibitor TSC1 in skeletal muscle accelerates sarcopenia development in adult mice. Conversely, genetic suppression of mTORC1 downstream effectors of protein synthesis delays sarcopenia in natural aging mice. mTORC1 promotes protein synthesis by activating ribosomal protein S6 kinases (S6Ks) and inhibiting eIF4E-binding proteins (4EBPs). Whole-body knockout of S6K1 or muscle-specific over-expression of a 4EBP1 mutant transgene (4EBP1mt), which is resistant to mTORC1-mediated inhibition, ameliorates muscle loss with age and preserves muscle function by enhancing mitochondria activities, despite both transgenic mice showing retarded muscle growth at a young age. Why repression of mTORC1-mediated protein synthesis can mitigate progressive muscle atrophy and dysfunction with age remains unclear. METHODS Mice with myofiber-specific knockout of TSC1 (TSC1mKO), in which mTORC1 is hyperactivated in fully differentiated myofibers, were used as a mouse model of sarcopenia. To elucidate the role of mTORC1-mediated protein synthesis in regulating muscle mass and physiology, we bred the 4EBP1mt transgene or S6k1 floxed mice into the TSC1mKO mouse background to generate 4EBP1mt-TSC1mKO or S6K1-TSC1mKO mice, respectively. Functional and molecular analyses were performed to assess their role in sarcopenia development. RESULTS Here, we show that 4EBP1mt-TSC1mKO, but not S6K1-TSC1mKO, preserved muscle mass (36.7% increase compared with TSC1mKO, P < 0.001) and strength (36.8% increase compared with TSC1mKO, P < 0.01) at the level of control mice. Mechanistically, 4EBP1 activation suppressed aberrant protein synthesis (two-fold reduction compared with TSC1mKO, P < 0.05) and restored autophagy flux without relieving mTORC1-mediated inhibition of ULK1, an upstream activator of autophagosome initiation. We discovered a previously unidentified phenotype of lysosomal failure in TSC1mKO mouse muscle, in which the lysosomal defect was also conserved in the naturally aged mouse muscle, whereas 4EBP1 activation enhanced lysosomal protease activities to compensate for impaired autophagy induced by mTORC1 hyperactivity. Consequently, 4EBP1 activation relieved oxidative stress to prevent toxic aggregate accumulation (0.5-fold reduction compared with TSC1mKO, P < 0.05) in muscle and restored mitochondrial homeostasis and function. CONCLUSIONS We identify 4EBP1 as a communication hub coordinating protein synthesis and degradation to protect proteostasis, revealing therapeutic potential for activating lysosomal degradation to mitigate sarcopenia.
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Affiliation(s)
- Elisa M Crombie
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Seonyoung Kim
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Stuart Adamson
- Buck Institute for Research on Aging, Novato, California, USA
| | - Han Dong
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Tzu-Chiao Lu
- Research Center for Healthy Aging, China Medical University, Taichung, Taiwan
| | - Yiju Wu
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Yajun Wu
- Department of Anatomy, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Yotam Levy
- Centre of Human and Applied Physiological Sciences, School of Basic and Medical Biosciences, Faculty of Life Sciences & Medicine, King's College, London, UK
| | - Nolan Stimple
- Buck Institute for Research on Aging, Novato, California, USA
| | - Wing Moon R Lam
- Department of Orthopedic Surgery, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Hwee Weng D Hey
- Department of Orthopedic Surgery, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Dominic J Withers
- Metabolic Signalling Group, Medical Research Council London Institute of Medical Sciences (LMS), London, UK.,Institute of Clinical Sciences (ICS), Faculty of Medicine, Imperial College London, London, UK
| | - Ao-Lin Hsu
- Research Center for Healthy Aging, China Medical University, Taichung, Taiwan.,Institute of Biochemistry and Molecular Biology, National Yang Ming Chiao Tung University, Taipei, Taiwan
| | - Boon Huat Bay
- Department of Anatomy, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Julien Ochala
- Centre of Human and Applied Physiological Sciences, School of Basic and Medical Biosciences, Faculty of Life Sciences & Medicine, King's College, London, UK.,Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Shih-Yin Tsai
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.,Healthy Longevity Translational Research Programme, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
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3
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Muscle 4EBP1 activation modifies the structure and function of the neuromuscular junction in mice. Nat Commun 2022; 13:7792. [PMID: 36526657 PMCID: PMC9758177 DOI: 10.1038/s41467-022-35547-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2022] [Accepted: 12/09/2022] [Indexed: 12/23/2022] Open
Abstract
Dysregulation of mTOR complex 1 (mTORC1) activity drives neuromuscular junction (NMJ) structural instability during aging; however, downstream targets mediating this effect have not been elucidated. Here, we investigate the roles of two mTORC1 phosphorylation targets for mRNA translation, ribosome protein S6 kinase 1 (S6K1) and eukaryotic translation initiation factor 4E-binding protein 1 (4EBP1), in regulating NMJ structural instability induced by aging and sustained mTORC1 activation. While myofiber-specific deletion of S6k1 has no effect on NMJ structural integrity, 4EBP1 activation in murine muscle induces drastic morphological remodeling of the NMJ with enhancement of synaptic transmission. Mechanistically, structural modification of the NMJ is attributed to increased satellite cell activation and enhanced post-synaptic acetylcholine receptor (AChR) turnover upon 4EBP1 activation. Considering that loss of post-synaptic myonuclei and reduced NMJ turnover are features of aging, targeting 4EBP1 activation could induce NMJ renewal by expanding the pool of post-synaptic myonuclei as an alternative intervention to mitigate sarcopenia.
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4
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Preclinical Advances of Therapies for Laminopathies. J Clin Med 2021; 10:jcm10214834. [PMID: 34768351 PMCID: PMC8584472 DOI: 10.3390/jcm10214834] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Revised: 10/19/2021] [Accepted: 10/19/2021] [Indexed: 11/29/2022] Open
Abstract
Laminopathies are a group of rare disorders due to mutation in LMNA gene. Depending on the mutation, they may affect striated muscles, adipose tissues, nerves or are multisystemic with various accelerated ageing syndromes. Although the diverse pathomechanisms responsible for laminopathies are not fully understood, several therapeutic approaches have been evaluated in patient cells or animal models, ranging from gene therapies to cell and drug therapies. This review is focused on these therapies with a strong focus on striated muscle laminopathies and premature ageing syndromes.
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Cabral WA, Tavarez UL, Beeram I, Yeritsyan D, Boku YD, Eckhaus MA, Nazarian A, Erdos MR, Collins FS. Genetic reduction of mTOR extends lifespan in a mouse model of Hutchinson-Gilford Progeria syndrome. Aging Cell 2021; 20:e13457. [PMID: 34453483 PMCID: PMC8441492 DOI: 10.1111/acel.13457] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Hutchinson-Gilford progeria syndrome (HGPS) is a rare accelerated aging disorder most notably characterized by cardiovascular disease and premature death from myocardial infarction or stroke. The majority of cases are caused by a de novo single nucleotide mutation in the LMNA gene that activates a cryptic splice donor site, resulting in production of a toxic form of lamin A with a 50 amino acid internal deletion, termed progerin. We previously reported the generation of a transgenic murine model of progeria carrying a human BAC harboring the common mutation, G608G, which in the single-copy state develops features of HGPS that are limited to the vascular system. Here, we report the phenotype of mice bred to carry two copies of the BAC, which more completely recapitulate the phenotypic features of HGPS in skin, adipose, skeletal, and vascular tissues. We further show that genetic reduction of the mechanistic target of rapamycin (mTOR) significantly extends lifespan in these mice, providing a rationale for pharmacologic inhibition of the mTOR pathway in the treatment of HGPS.
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Affiliation(s)
- Wayne A. Cabral
- Molecular Genetics Section Center for Precision Health Research National Human Genome Research Institute National Institutes of Health Bethesda MD USA
| | - Urraca L. Tavarez
- Molecular Genetics Section Center for Precision Health Research National Human Genome Research Institute National Institutes of Health Bethesda MD USA
| | - Indeevar Beeram
- Translational Musculoskeletal Innovation Initiative Carl J. Shapiro Department of Orthopedic Surgery Beth Israel Deaconess Medical Center Harvard Medical School Boston MA USA
| | - Diana Yeritsyan
- Translational Musculoskeletal Innovation Initiative Carl J. Shapiro Department of Orthopedic Surgery Beth Israel Deaconess Medical Center Harvard Medical School Boston MA USA
| | - Yoseph D. Boku
- Molecular Genetics Section Center for Precision Health Research National Human Genome Research Institute National Institutes of Health Bethesda MD USA
| | - Michael A. Eckhaus
- Diagnostic and Research Services Branch Division of Veterinary Resources Office of the Director National Institutes of Health Bethesda MD USA
| | - Ara Nazarian
- Translational Musculoskeletal Innovation Initiative Carl J. Shapiro Department of Orthopedic Surgery Beth Israel Deaconess Medical Center Harvard Medical School Boston MA USA
| | - Michael R. Erdos
- Molecular Genetics Section Center for Precision Health Research National Human Genome Research Institute National Institutes of Health Bethesda MD USA
| | - Francis S. Collins
- Molecular Genetics Section Center for Precision Health Research National Human Genome Research Institute National Institutes of Health Bethesda MD USA
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6
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Skeletal and Cardiac Muscle Disorders Caused by Mutations in Genes Encoding Intermediate Filament Proteins. Int J Mol Sci 2021; 22:ijms22084256. [PMID: 33923914 PMCID: PMC8073371 DOI: 10.3390/ijms22084256] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Revised: 04/12/2021] [Accepted: 04/15/2021] [Indexed: 02/08/2023] Open
Abstract
Intermediate filaments are major components of the cytoskeleton. Desmin and synemin, cytoplasmic intermediate filament proteins and A-type lamins, nuclear intermediate filament proteins, play key roles in skeletal and cardiac muscle. Desmin, encoded by the DES gene (OMIM *125660) and A-type lamins by the LMNA gene (OMIM *150330), have been involved in striated muscle disorders. Diseases include desmin-related myopathy and cardiomyopathy (desminopathy), which can be manifested with dilated, restrictive, hypertrophic, arrhythmogenic, or even left ventricular non-compaction cardiomyopathy, Emery–Dreifuss Muscular Dystrophy (EDMD2 and EDMD3, due to LMNA mutations), LMNA-related congenital Muscular Dystrophy (L-CMD) and LMNA-linked dilated cardiomyopathy with conduction system defects (CMD1A). Recently, mutations in synemin (SYNM gene, OMIM *606087) have been linked to cardiomyopathy. This review will summarize clinical and molecular aspects of desmin-, lamin- and synemin-related striated muscle disorders with focus on LMNA and DES-associated clinical entities and will suggest pathogenetic hypotheses based on the interplay of desmin and lamin A/C. In healthy muscle, such interplay is responsible for the involvement of this network in mechanosignaling, nuclear positioning and mitochondrial homeostasis, while in disease it is disturbed, leading to myocyte death and activation of inflammation and the associated secretome alterations.
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7
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Wang AP, Yang F, Tian Y, Su JH, Gu Q, Chen W, Gong SX, Ma XF, Qin XP, Jiang ZS. Pulmonary Artery Smooth Muscle Cell Senescence Promotes the Proliferation of PASMCs by Paracrine IL-6 in Hypoxia-Induced Pulmonary Hypertension. Front Physiol 2021; 12:656139. [PMID: 33897463 PMCID: PMC8058366 DOI: 10.3389/fphys.2021.656139] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Accepted: 02/23/2021] [Indexed: 01/14/2023] Open
Abstract
Pulmonary hypertension (PH) is a critical and dangerous disease in cardiovascular system. Pulmonary vascular remodeling is an important pathophysiological mechanism for the development of pulmonary arterial hypertension. Pulmonary artery smooth muscle cell (PASMC) proliferation, hypertrophy, and enhancing secretory activity are the main causes of pulmonary vascular remodeling. Previous studies have proven that various active substances and inflammatory factors, such as interleukin 6 (IL-6), IL-8, chemotactic factor for monocyte 1, etc., are involved in pulmonary vascular remodeling in PH. However, the underlying mechanisms of these active substances to promote the PASMC proliferation remain to be elucidated. In our study, we demonstrated that PASMC senescence, as a physiopathologic mechanism, played an essential role in hypoxia-induced PASMC proliferation. In the progression of PH, senescence PASMCs could contribute to PASMC proliferation via increasing the expression of paracrine IL-6 (senescence-associated secretory phenotype). In addition, we found that activated mTOR/S6K1 pathway can promote PASMC senescence and elevate hypoxia-induced PASMC proliferation. Further study revealed that the activation of mTOR/S6K1 pathway was responsible for senescence PASMCs inducing PASMC proliferation via paracrine IL-6. Targeted inhibition of PASMC senescence could effectively suppress PASMC proliferation and relieve pulmonary vascular remodeling in PH, indicating a potential for the exploration of novel anti-PH strategies.
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Affiliation(s)
- Ai-Ping Wang
- Institute of Cardiovascular Disease, Key Lab for Arteriosclerology of Hunan Province, University of South China, Hengyang, China.,Department of Physiology, Institute of Neuroscience, Hengyang Key Laboratory of Neurodegeneration and Cognitive Impairment, Hengyang Medical College, University of South China, Hengyang, China.,Institute of Clinical Research, Affiliated Nanhua Hospital, University of South China, Hengyang, China
| | - Fang Yang
- Laboratory of Vascular Biology, Institute of Pharmacy and Pharmacology, University of South China, Hengyang, China
| | - Ying Tian
- Institute of Clinical Research, Affiliated Nanhua Hospital, University of South China, Hengyang, China
| | - Jian-Hui Su
- Institute of Clinical Research, Affiliated Nanhua Hospital, University of South China, Hengyang, China
| | - Qing Gu
- State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Wei Chen
- Department of Physiology, Institute of Neuroscience, Hengyang Key Laboratory of Neurodegeneration and Cognitive Impairment, Hengyang Medical College, University of South China, Hengyang, China
| | - Shao-Xin Gong
- Department of Pathology, The First Affiliated Hospital, University of South China, Hengyang, China
| | - Xiao-Feng Ma
- Institute of Clinical Research, Affiliated Nanhua Hospital, University of South China, Hengyang, China
| | - Xu-Ping Qin
- Laboratory of Vascular Biology, Institute of Pharmacy and Pharmacology, University of South China, Hengyang, China
| | - Zhi-Sheng Jiang
- Institute of Cardiovascular Disease, Key Lab for Arteriosclerology of Hunan Province, University of South China, Hengyang, China
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8
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Lee JY, Kennedy BK, Liao CY. Mechanistic target of rapamycin signaling in mouse models of accelerated aging. J Gerontol A Biol Sci Med Sci 2020; 75:64-72. [PMID: 30900725 DOI: 10.1093/gerona/glz059] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2018] [Accepted: 02/23/2019] [Indexed: 01/06/2023] Open
Abstract
The mechanistic target of rapamycin (mTOR) is an essential nutrient-sensing kinase that integrates and regulates a number of fundamental cellular processes required for cell growth, cell motility, translation, metabolism, and autophagy. mTOR signaling has been implicated in the progression of many human diseases, and its dysregulation has been reported in several pathological processes, especially in age-related human diseases and mouse models of accelerated aging. In addition, many studies have demonstrated that the regulation of mTOR activity has a beneficial effect on longevity in several mouse models of aging. However, not all mouse models of accelerated aging show positive effects on aging-associated phenotypes in response to targeting mTOR signaling. Here, we review the effects of interventions that modulate mTOR signaling on aging-related phenotypes in different mouse models of accelerated aging and discuss their implications with respect to aging and aging-related disorders.
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Affiliation(s)
- Jin Young Lee
- Buck Institute for Research on Aging, Novato, California
| | - Brian K Kennedy
- Buck Institute for Research on Aging, Novato, California
- Department of Biochemistry and Physiology, National University of Singapore, Singapore
- Centre for Healthy Ageing, National University Health System, Singapore
- Singapore Institute for Clinical Sciences, A*STAR, Singapore
| | - Chen-Yu Liao
- Buck Institute for Research on Aging, Novato, California
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9
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Tan KT, Ang STJ, Tsai SY. Sarcopenia: Tilting the Balance of Protein Homeostasis. Proteomics 2019; 20:e1800411. [PMID: 31722440 DOI: 10.1002/pmic.201800411] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Revised: 11/04/2019] [Indexed: 12/14/2022]
Abstract
Sarcopenia, defined as age-associated decline of muscle mass and function, is a risk factor for mortality and disability, and comorbid with several chronic diseases such as type II diabetes and cardiovascular diseases. Clinical trials showed that nutritional supplements had positive effects on muscle mass, but not on muscle function and strength, demonstrating our limited understanding of the molecular events involved in the ageing muscle. Protein homeostasis, the equilibrium between protein synthesis and degradation, is proposed as the major mechanism underlying the development of sarcopenia. As the key central regulator of protein homeostasis, the mammalian target of rapamycin (mTOR) is proposed to be essential for muscle hypertrophy. Paradoxically, sustained activation of mTOR complex 1 (mTORC1) is associated with a loss of sensitivity to extracellular signaling in the elderly. It is not understood why sustained mTORC1 activity, which should induce muscle hypertrophy, instead results in muscle atrophy. Here, recent findings on the implications of disrupting protein homeostasis on muscle physiology and sarcopenia development in the context of mTOR/protein kinase B (AKT) signaling are reviewed. Understanding the role of these molecular mechanisms during the ageing process will contribute towards the development of targeted therapies that will improve protein metabolism and reduce sarcopenia.
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Affiliation(s)
- Kuan Ting Tan
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, 2 Medical Drive, MD9 Admin Office, Singapore, 117597, Singapore
| | - Seok-Ting Jamie Ang
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, 2 Medical Drive, MD9 Admin Office, Singapore, 117597, Singapore
| | - Shih-Yin Tsai
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, 2 Medical Drive, MD9 Admin Office, Singapore, 117597, Singapore
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10
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Genetic deletion of S6k1 does not rescue the phenotypic deficits observed in the R6/2 mouse model of Huntington's disease. Sci Rep 2019; 9:16133. [PMID: 31695068 PMCID: PMC6834565 DOI: 10.1038/s41598-019-52391-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Accepted: 10/11/2019] [Indexed: 01/14/2023] Open
Abstract
Huntington’s disease (HD) is a fatal inherited autosomal dominant neurodegenerative disorder caused by an expansion in the number of CAG trinucleotide repeats in the huntingtin gene. The disease is characterized by motor, behavioural and cognitive symptoms for which at present there are no disease altering treatments. It has been shown that manipulating the mTOR (mammalian target of rapamycin) pathway using rapamycin or its analogue CCI-779 can improve the cellular and behavioural phenotypes of HD models. Ribosomal protein S6 kinase 1 (S6K1) is a major downstream signalling molecule of mTOR, and its activity is reduced by rapamycin suggesting that deregulation of S6K1 activity may be beneficial in HD. Furthermore, S6k1 knockout mice have increased lifespan and improvement in age-related phenotypes. To evalute the potential benefit of S6k1 loss on HD-related phenotypes, we crossed the R6/2 HD model with the long-lived S6k1 knockout mouse line. We found that S6k1 knockout does not ameliorate behavioural or physiological phenotypes in the R6/2 mouse model. Additionally, no improvements were seen in brain mass reduction or mutant huntingtin protein aggregate levels. Therefore, these results suggest that while a reduction in S6K1 signalling has beneficial effects on ageing it is unlikely to be a therapeutic strategy for HD patients.
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11
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Pellegrini C, Columbaro M, Schena E, Prencipe S, Andrenacci D, Iozzo P, Angela Guzzardi M, Capanni C, Mattioli E, Loi M, Araujo-Vilar D, Squarzoni S, Cinti S, Morselli P, Giorgetti A, Zanotti L, Gambineri A, Lattanzi G. Altered adipocyte differentiation and unbalanced autophagy in type 2 Familial Partial Lipodystrophy: an in vitro and in vivo study of adipose tissue browning. Exp Mol Med 2019; 51:1-17. [PMID: 31375660 PMCID: PMC6802660 DOI: 10.1038/s12276-019-0289-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2018] [Revised: 04/04/2019] [Accepted: 04/16/2019] [Indexed: 01/29/2023] Open
Abstract
Type-2 Familial Partial Lipodystrophy is caused by LMNA mutations. Patients gradually lose subcutaneous fat from the limbs, while they accumulate adipose tissue in the face and neck. Several studies have demonstrated that autophagy is involved in the regulation of adipocyte differentiation and the maintenance of the balance between white and brown adipose tissue. We identified deregulation of autophagy in laminopathic preadipocytes before induction of differentiation. Moreover, in differentiating white adipocyte precursors, we observed impairment of large lipid droplet formation, altered regulation of adipose tissue genes, and expression of the brown adipose tissue marker UCP1. Conversely, in lipodystrophic brown adipocyte precursors induced to differentiate, we noticed activation of autophagy, formation of enlarged lipid droplets typical of white adipocytes, and dysregulation of brown adipose tissue genes. In agreement with these in vitro results indicating conversion of FPLD2 brown preadipocytes toward the white lineage, adipose tissue from FPLD2 patient neck, an area of brown adipogenesis, showed a white phenotype reminiscent of its brown origin. Moreover, in vivo morpho-functional evaluation of fat depots in the neck area of three FPLD2 patients by PET/CT analysis with cold stimulation showed the absence of brown adipose tissue activity. These findings highlight a new pathogenetic mechanism leading to improper fat distribution in lamin A-linked lipodystrophies and show that both impaired white adipocyte turnover and failure of adipose tissue browning contribute to disease. An abnormal distribution of fatty tissues associated with certain tissue disorders is driven by disrupted fat cell differentiation. Type 2 familial partial lipodystrophy (FPLD2) is a genetic condition that results in fat being lost from the limbs and accumulating in the face and neck. Giovanna Lattanzi at the National Research Council of Italy in Bologna and co-workers found that fat cell (adipocyte) precursors did not clearly differentiate into either of the two main fatty tissue types, brown or white, in FPLD2 patients. White adipocyte precursors exhibited impaired lipid formation and abnormal levels of brown tissue markers. Conversely, brown adipocyte precursors showed high lipid levels and increased autophagy, a natural process involving degradation and recycling of cellular components. The neck is normally where brown fat accumulates, but FPLD2 patients had adipocytes there displaying white fat characteristics.
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Affiliation(s)
- Camilla Pellegrini
- CNR - National Research Council of Italy, Institute of Molecular Genetics "Luigi Luca Cavalli-Sforza", Unit of Bologna, Bologna, Italy
| | | | - Elisa Schena
- CNR - National Research Council of Italy, Institute of Molecular Genetics "Luigi Luca Cavalli-Sforza", Unit of Bologna, Bologna, Italy.,IRCCS, Istituto Ortopedico Rizzoli, Bologna, Italy
| | - Sabino Prencipe
- CNR - National Research Council of Italy, Institute of Molecular Genetics "Luigi Luca Cavalli-Sforza", Unit of Bologna, Bologna, Italy
| | - Davide Andrenacci
- CNR - National Research Council of Italy, Institute of Molecular Genetics "Luigi Luca Cavalli-Sforza", Unit of Bologna, Bologna, Italy.,IRCCS, Istituto Ortopedico Rizzoli, Bologna, Italy
| | - Patricia Iozzo
- CNR - National Research Council of Italy, Institute of Clinical Physiology, Pisa, Italy
| | - Maria Angela Guzzardi
- CNR - National Research Council of Italy, Institute of Clinical Physiology, Pisa, Italy
| | - Cristina Capanni
- CNR - National Research Council of Italy, Institute of Molecular Genetics "Luigi Luca Cavalli-Sforza", Unit of Bologna, Bologna, Italy.,IRCCS, Istituto Ortopedico Rizzoli, Bologna, Italy
| | - Elisabetta Mattioli
- CNR - National Research Council of Italy, Institute of Molecular Genetics "Luigi Luca Cavalli-Sforza", Unit of Bologna, Bologna, Italy.,IRCCS, Istituto Ortopedico Rizzoli, Bologna, Italy
| | - Manuela Loi
- CNR - National Research Council of Italy, Institute of Molecular Genetics "Luigi Luca Cavalli-Sforza", Unit of Bologna, Bologna, Italy
| | - David Araujo-Vilar
- Department of Medicine, CIMUS Biomedical Research Institute, University of Santiago de Compostela, Santiago de Compostela, Spain
| | - Stefano Squarzoni
- CNR - National Research Council of Italy, Institute of Molecular Genetics "Luigi Luca Cavalli-Sforza", Unit of Bologna, Bologna, Italy.,IRCCS, Istituto Ortopedico Rizzoli, Bologna, Italy
| | - Saverio Cinti
- Department of Experimental and Clinical Medicine, University of Ancona (UniversitàPolitecnicadelle Marche), Ancona, Italy.,Center of Obesity of University of Ancona, Ancona, Italy
| | - Paolo Morselli
- Plastic Surgery Unit, Department of Specialised, Experimental, and Diagnostic Medicine, Alma Mater Studiorum University of Bologna, S Orsola-Malpighi Hospital, Bologna, Italy
| | | | - Laura Zanotti
- Endocrinology Unit, Department of Medical and Surgical Sciences, Alma Mater Studiorum University of Bologna, S Orsola-Malpighi Hospital, Bologna, Italy
| | - Alessandra Gambineri
- Endocrinology Unit, Department of Medical and Surgical Sciences, Alma Mater Studiorum University of Bologna, S Orsola-Malpighi Hospital, Bologna, Italy
| | - Giovanna Lattanzi
- CNR - National Research Council of Italy, Institute of Molecular Genetics "Luigi Luca Cavalli-Sforza", Unit of Bologna, Bologna, Italy. .,IRCCS, Istituto Ortopedico Rizzoli, Bologna, Italy.
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Kirby TJ. Mechanosensitive pathways controlling translation regulatory processes in skeletal muscle and implications for adaptation. J Appl Physiol (1985) 2019; 127:608-618. [PMID: 31295035 DOI: 10.1152/japplphysiol.01031.2018] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The ability of myofibers to sense and respond appropriately to mechanical signals is one of the primary determinants of the skeletal muscle phenotype. In response to a change in mechanical load, muscle cells alter their protein metabolism, primarily through the regulation of protein synthesis rate. Protein synthesis rates are determined by both translation efficiency and translational capacity within the muscle. Translational capacity is strongly determined by the ribosome content of the muscle; thus the regulation of ribosomal biogenesis by mechanical inputs has been an area of recent interest. Despite the clear association between mechanical signals and changes in protein metabolism, the molecular pathways that link these events are still not fully elucidated. This review focuses on recent studies looking at how mechanosignaling impacts translational events. The role of impaired mechanotransduction in aging is discussed, as is the connection between age-dependent signaling defects and compromised ribosomal biogenesis during mechanical overload. Finally, emerging evidence suggests that the nucleus can act as a mechanosensitive element and that this mode of mechanotransduction may have an important role in skeletal muscle physiology and adaptation.
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Affiliation(s)
- Tyler J Kirby
- Nancy E. and Peter C. Meinig School of Biomedical Engineering, Cornell University, Ithaca, New York.,Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, New York
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13
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The Cutting Edge: The Role of mTOR Signaling in Laminopathies. Int J Mol Sci 2019; 20:ijms20040847. [PMID: 30781376 PMCID: PMC6412338 DOI: 10.3390/ijms20040847] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Revised: 02/11/2019] [Accepted: 02/12/2019] [Indexed: 12/29/2022] Open
Abstract
The mechanistic target of rapamycin (mTOR) is a ubiquitous serine/threonine kinase that regulates anabolic and catabolic processes, in response to environmental inputs. The existence of mTOR in numerous cell compartments explains its specific ability to sense stress, execute growth signals, and regulate autophagy. mTOR signaling deregulation is closely related to aging and age-related disorders, among which progeroid laminopathies represent genetically characterized clinical entities with well-defined phenotypes. These diseases are caused by LMNA mutations and feature altered bone turnover, metabolic dysregulation, and mild to severe segmental progeria. Different LMNA mutations cause muscular, adipose tissue and nerve pathologies in the absence of major systemic involvement. This review explores recent advances on mTOR involvement in progeroid and tissue-specific laminopathies. Indeed, hyper-activation of protein kinase B (AKT)/mTOR signaling has been demonstrated in muscular laminopathies, and rescue of mTOR-regulated pathways increases lifespan in animal models of Emery-Dreifuss muscular dystrophy. Further, rapamycin, the best known mTOR inhibitor, has been used to elicit autophagy and degradation of mutated lamin A or progerin in progeroid cells. This review focuses on mTOR-dependent pathogenetic events identified in Emery-Dreifuss muscular dystrophy, LMNA-related cardiomyopathies, Hutchinson-Gilford Progeria, mandibuloacral dysplasia, and type 2 familial partial lipodystrophy. Pharmacological application of mTOR inhibitors in view of therapeutic strategies is also discussed.
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14
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Chandran S, Suggs JA, Wang BJ, Han A, Bhide S, Cryderman DE, Moore SA, Bernstein SI, Wallrath LL, Melkani GC. Suppression of myopathic lamin mutations by muscle-specific activation of AMPK and modulation of downstream signaling. Hum Mol Genet 2019; 28:351-371. [PMID: 30239736 PMCID: PMC6337691 DOI: 10.1093/hmg/ddy332] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Revised: 09/11/2018] [Accepted: 09/13/2018] [Indexed: 12/14/2022] Open
Abstract
Laminopathies are diseases caused by dominant mutations in the human LMNA gene encoding A-type lamins. Lamins are intermediate filaments that line the inner nuclear membrane, provide structural support for the nucleus and regulate gene expression. Drosophila melanogaster models of skeletal muscle laminopathies were developed to investigate the pathological defects caused by mutant lamins and identify potential therapeutic targets. Human disease-causing LMNA mutations were modeled in Drosophila Lamin C (LamC) and expressed in indirect flight muscle (IFM). IFM-specific expression of mutant, but not wild-type LamC, caused held-up wings indicative of myofibrillar defects. Analyses of the muscles revealed cytoplasmic aggregates of nuclear envelope (NE) proteins, nuclear and mitochondrial dysmorphology, myofibrillar disorganization and up-regulation of the autophagy cargo receptor p62. We hypothesized that the cytoplasmic aggregates of NE proteins trigger signaling pathways that alter cellular homeostasis, causing muscle dysfunction. In support of this hypothesis, transcriptomics data from human muscle biopsy tissue revealed misregulation of the AMP-activated protein kinase (AMPK)/4E-binding protein 1 (4E-BP1)/autophagy/proteostatic pathways. Ribosomal protein S6K (S6K) messenger RNA (mRNA) levels were increased and AMPKα and mRNAs encoding downstream targets were decreased in muscles expressing mutant LMNA relative controls. The Drosophila laminopathy models were used to determine if altering the levels of these factors modulated muscle pathology. Muscle-specific over-expression of AMPKα and down-stream targets 4E-BP, Forkhead box transcription factors O (Foxo) and Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α), as well as inhibition of S6K, suppressed the held-up wing phenotype, myofibrillar defects and LamC aggregation. These findings provide novel insights on mutant LMNA-based disease mechanisms and identify potential targets for drug therapy.
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Affiliation(s)
- Sahaana Chandran
- Department of Biology, Molecular Biology and Heart Institutes, San Diego State University, San Diego, CA, USA
| | - Jennifer A Suggs
- Department of Biology, Molecular Biology and Heart Institutes, San Diego State University, San Diego, CA, USA
| | - Bingyan J Wang
- Department of Biology, Molecular Biology and Heart Institutes, San Diego State University, San Diego, CA, USA
| | - Andrew Han
- Department of Biology, Molecular Biology and Heart Institutes, San Diego State University, San Diego, CA, USA
| | - Shruti Bhide
- Department of Biology, Molecular Biology and Heart Institutes, San Diego State University, San Diego, CA, USA
| | - Diane E Cryderman
- Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, IA, USA
| | - Steven A Moore
- Department of Pathology, Carver College of Medicine, University of Iowa, Iowa City, IA, USA
| | - Sanford I Bernstein
- Department of Biology, Molecular Biology and Heart Institutes, San Diego State University, San Diego, CA, USA
| | - Lori L Wallrath
- Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, IA, USA
| | - Girish C Melkani
- Department of Biology, Molecular Biology and Heart Institutes, San Diego State University, San Diego, CA, USA
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