51
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Bentzinger CF, von Maltzahn J, Dumont NA, Stark DA, Wang YX, Nhan K, Frenette J, Cornelison DDW, Rudnicki MA. Wnt7a stimulates myogenic stem cell motility and engraftment resulting in improved muscle strength. J Cell Biol 2014; 205:97-111. [PMID: 24711502 PMCID: PMC3987134 DOI: 10.1083/jcb.201310035] [Citation(s) in RCA: 117] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2013] [Accepted: 03/05/2014] [Indexed: 12/19/2022] Open
Abstract
Wnt7a/Fzd7 signaling stimulates skeletal muscle growth and repair by inducing the symmetric expansion of satellite stem cells through the planar cell polarity pathway and by activating the Akt/mTOR growth pathway in muscle fibers. Here we describe a third level of activity where Wnt7a/Fzd7 increases the polarity and directional migration of mouse satellite cells and human myogenic progenitors through activation of Dvl2 and the small GTPase Rac1. Importantly, these effects can be exploited to potentiate the outcome of myogenic cell transplantation into dystrophic muscles. We observed that a short Wnt7a treatment markedly stimulated tissue dispersal and engraftment, leading to significantly improved muscle function. Moreover, myofibers at distal sites that fused with Wnt7a-treated cells were hypertrophic, suggesting that the transplanted cells deliver activated Wnt7a/Fzd7 signaling complexes to recipient myofibers. Taken together, we describe a viable and effective ex vivo cell modulation process that profoundly enhances the efficacy of stem cell therapy for skeletal muscle.
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MESH Headings
- Adaptor Proteins, Signal Transducing/metabolism
- Animals
- Cell Fusion
- Cell Line
- Cell Movement
- Cell Polarity
- Disease Models, Animal
- Dishevelled Proteins
- Endocytosis
- Frizzled Receptors/metabolism
- Genes, Reporter
- Green Fluorescent Proteins/genetics
- Green Fluorescent Proteins/metabolism
- Humans
- Hypertrophy
- Luminescent Proteins/genetics
- Luminescent Proteins/metabolism
- Mice
- Mice, Inbred mdx
- Mice, Knockout
- Mice, Transgenic
- Muscle Strength
- Muscle, Skeletal/metabolism
- Muscle, Skeletal/pathology
- Muscle, Skeletal/physiopathology
- Muscle, Skeletal/surgery
- Muscular Dystrophies/genetics
- Muscular Dystrophies/metabolism
- Muscular Dystrophies/pathology
- Muscular Dystrophies/physiopathology
- Muscular Dystrophies/surgery
- Myoblasts, Skeletal/metabolism
- Myoblasts, Skeletal/pathology
- Myoblasts, Skeletal/transplantation
- Neuropeptides/metabolism
- PAX7 Transcription Factor/genetics
- Phosphoproteins/metabolism
- Promoter Regions, Genetic
- Receptors, G-Protein-Coupled/deficiency
- Receptors, G-Protein-Coupled/genetics
- Recombinant Fusion Proteins/metabolism
- Signal Transduction
- Wnt Proteins/genetics
- Wnt Proteins/metabolism
- rac1 GTP-Binding Protein/metabolism
- Red Fluorescent Protein
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Affiliation(s)
- C. Florian Bentzinger
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, ON K1H 8L6, Canada
- Faculty of Medicine, Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON K1H 8M5, Canada
| | - Julia von Maltzahn
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, ON K1H 8L6, Canada
- Faculty of Medicine, Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON K1H 8M5, Canada
| | - Nicolas A. Dumont
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, ON K1H 8L6, Canada
- Faculty of Medicine, Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON K1H 8M5, Canada
| | - Danny A. Stark
- Division of Biological Sciences and Christopher S. Bond Life Sciences Center, University of Missouri, Columbia, MO 65211
| | - Yu Xin Wang
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, ON K1H 8L6, Canada
- Faculty of Medicine, Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON K1H 8M5, Canada
| | - Kevin Nhan
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, ON K1H 8L6, Canada
- Faculty of Medicine, Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON K1H 8M5, Canada
| | - Jérôme Frenette
- Faculty of Medicine, Department of Rehabilitation, Laval University, Quebec City, QC G1V 4G2, Canada
| | - DDW Cornelison
- Division of Biological Sciences and Christopher S. Bond Life Sciences Center, University of Missouri, Columbia, MO 65211
| | - Michael A. Rudnicki
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, ON K1H 8L6, Canada
- Faculty of Medicine, Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON K1H 8M5, Canada
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52
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Wang YX, Bentzinger CF, Rudnicki MA. Treating muscular dystrophy by stimulating intrinsic repair. Regen Med 2014; 8:237-40. [PMID: 23627818 DOI: 10.2217/rme.13.27] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Affiliation(s)
- Yu Xin Wang
- Sprott Centre for Stem Cell Research, Ottawa Hospital Research Institute, Ottawa, ON K1H 8L6, Canada
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53
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Bernet JD, Doles JD, Hall JK, Kelly Tanaka K, Carter TA, Olwin BB. p38 MAPK signaling underlies a cell-autonomous loss of stem cell self-renewal in skeletal muscle of aged mice. Nat Med 2014; 20:265-71. [PMID: 24531379 PMCID: PMC4070883 DOI: 10.1038/nm.3465] [Citation(s) in RCA: 402] [Impact Index Per Article: 40.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2013] [Accepted: 01/10/2014] [Indexed: 12/13/2022]
Abstract
Skeletal muscle aging results in a gradual loss of skeletal muscle mass, skeletal muscle function and decreased regenerative capacity, which can lead to sarcopenia and increased mortality. While the mechanisms underlying sarcopenia remain unclear, the skeletal muscle stem cell, or satellite cell, is required for muscle regeneration. Therefore, identification of signaling pathways affecting satellite cell function during aging may provide insights into therapeutic targets for combating sarcopenia. Here, we show that a cell-autonomous loss in self-renewal occurs via alterations in FGF Receptor 1 and p38αβ MAPK signaling in aged satellite cells. We further demonstrate that pharmacological manipulation of these pathways can ameliorate age-associated self-renewal defects. Thus, our data highlight an age-associated deregulation of a satellite cell homeostatic network and reveal potential therapeutic opportunities for the treatment of progressive muscle wasting.
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Affiliation(s)
- Jennifer D Bernet
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, Colorado, USA
| | - Jason D Doles
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, Colorado, USA
| | - John K Hall
- 1] Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, Colorado, USA. [2]
| | - Kathleen Kelly Tanaka
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, Colorado, USA
| | - Thomas A Carter
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, Colorado, USA
| | - Bradley B Olwin
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, Colorado, USA
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54
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MacDonald EM, Andres-Mateos E, Mejias R, Simmers JL, Mi R, Park JS, Ying S, Hoke A, Lee SJ, Cohn RD. Denervation atrophy is independent from Akt and mTOR activation and is not rescued by myostatin inhibition. Dis Model Mech 2014; 7:471-81. [PMID: 24504412 PMCID: PMC3974457 DOI: 10.1242/dmm.014126] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The purpose of our study was to compare two acquired muscle atrophies and the use of myostatin inhibition for their treatment. Myostatin naturally inhibits skeletal muscle growth by binding to ActRIIB, a receptor on the cell surface of myofibers. Because blocking myostatin in an adult wild-type mouse induces profound muscle hypertrophy, we applied a soluble ActRIIB receptor to models of disuse (limb immobilization) and denervation (sciatic nerve resection) atrophy. We found that treatment of immobilized mice with ActRIIB prevented the loss of muscle mass observed in placebo-treated mice. Our results suggest that this protection from disuse atrophy is regulated by serum and glucocorticoid-induced kinase (SGK) rather than by Akt. Denervation atrophy, however, was not protected by ActRIIB treatment, yet resulted in an upregulation of the pro-growth factors Akt, SGK and components of the mTOR pathway. We then treated the denervated mice with the mTOR inhibitor rapamycin and found that, despite a reduction in mTOR activation, there is no alteration of the atrophy phenotype. Additionally, rapamycin prevented the denervation-induced upregulation of the mTORC2 substrates Akt and SGK. Thus, our studies show that denervation atrophy is not only independent from Akt, SGK and mTOR activation but also has a different underlying pathophysiological mechanism than disuse atrophy.
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Affiliation(s)
- Elizabeth M MacDonald
- McKusick-Nathans Institute of Genetic Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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55
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Jespersen JG, Mikkelsen UR, Nedergaard A, Thorlund JB, Schjerling P, Suetta C, Christensen PA, Aagaard P. Alterations in molecular muscle mass regulators after 8 days immobilizing Special Forces mission. Scand J Med Sci Sports 2014; 25:175-83. [PMID: 24422600 DOI: 10.1111/sms.12170] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/03/2013] [Indexed: 01/01/2023]
Abstract
In military operations, declined physical capacity can endanger the life of soldiers. During special support and reconnaissance (SSR) missions, Special Forces soldiers sustain 1-2 weeks full-body horizontal immobilization, which impairs muscle strength and performance. Adequate muscle mass and strength are necessary in combat or evacuation situations, which prompt for improved understanding of muscle mass modulation during SSR missions. To explore the molecular regulation of myofiber size during a simulated SSR operation, nine male Special Forces soldiers were biopsied in m. vastus lateralis pre and post 8 days immobilizing restricted prone position. After immobilization, total mammalian target of rapamycin protein was reduced by 42% (P < 0.05), whereas total and phosphorylated protein levels of Akt, ribosomal protein S6k, 4E-BP1, and glycogen synthase kinase3β were unchanged. Messenger RNA (mRNA) levels of the atrogenes forkhead box O3 (FoxO3), atrogin1, and muscle ring finger protein1 (MuRF1) increased by 36%, 53%, and 71% (P < 0.01), MuRF1 protein by 51% (P = 0.05), whereas FoxO1 and peroxisome proliferator-activated receptor γ coactivator-1 β mRNAs decreased by 29% and 40% (P < 0.01). In conclusion, occupational immobilization in Special Forces soldiers led to modulations in molecular muscle mass regulators during 8 days prone SSR mission, which likely contribute to muscle loss observed in such operations. The present data expand our knowledge of human muscle mass regulation during short-term immobilization.
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Affiliation(s)
- J G Jespersen
- Institute of Sports Medicine, Department of Orthopedic Surgery M, Bispebjerg Hospital and Center for Healthy Aging, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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56
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Abstract
Preserving or restoring adequate nutritional status is a key factor to delay the onset of chronic diseases and to accelerate recovery from acute illnesses. In particular, consistent and robust data show the loss of muscle mass, that is, sarcopenia, is clinically relevant since it is closely related to increased morbidity and mortality in healthy individuals and patients. Sarcopenia is defined as the age-related loss of muscle mass and function. International study groups have recently proposed separate definitions and diagnostic criteria for sarcopenia. Unfortunately, the rate of agreement in assessing the prevalence of sarcopenia is just fair, which highlights the need for a common effort to harmonize definitions and diagnostic criteria. Sarcopenia should be distinct from myopenia, which is the disease-associated loss of muscle mass, although in clinical practice it may be impossible to separate them (i.e., in old cancer patients). The pathogenesis of sarcopenia is complex and multifactorial. Consequently, its treatment should target the different factors involved, including quantitatively and qualitatively inappropriate food intake and reduced physical activity.
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Affiliation(s)
| | - Chiara Gori
- Department of Clinical Medicine, Sapienza University, Rome, Italy
| | - Serena Rianda
- Department of Clinical Medicine, Sapienza University, Rome, Italy
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57
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Chen JL, Walton KL, Winbanks CE, Murphy KT, Thomson RE, Makanji Y, Qian H, Lynch GS, Harrison CA, Gregorevic P. Elevated expression of activins promotes muscle wasting and cachexia. FASEB J 2013; 28:1711-23. [PMID: 24378873 DOI: 10.1096/fj.13-245894] [Citation(s) in RCA: 142] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
In models of cancer cachexia, inhibiting type IIB activin receptors (ActRIIBs) reverse muscle wasting and prolongs survival, even with continued tumor growth. ActRIIB mediates signaling of numerous TGF-β proteins; of these, we demonstrate that activins are the most potent negative regulators of muscle mass. To determine whether activin signaling in the absence of tumor-derived factors induces cachexia, we used recombinant serotype 6 adeno-associated virus (rAAV6) vectors to increase circulating activin A levels in C57BL/6 mice. While mice injected with control vector gained ~10% of their starting body mass (3.8±0.4 g) over 10 wk, mice injected with increasing doses of rAAV6:activin A exhibited weight loss in a dose-dependent manner, to a maximum of -12.4% (-4.2±1.1 g). These reductions in body mass in rAAV6:activin-injected mice correlated inversely with elevated serum activin A levels (7- to 24-fold). Mechanistically, we show that activin A reduces muscle mass and function by stimulating the ActRIIB pathway, leading to deleterious consequences, including increased transcription of atrophy-related ubiquitin ligases, decreased Akt/mTOR-mediated protein synthesis, and a profibrotic response. Critically, we demonstrate that the muscle wasting and fibrosis that ensues in response to excessive activin levels is fully reversible. These findings highlight the therapeutic potential of targeting activins in cachexia.
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Affiliation(s)
- Justin L Chen
- 2Baker IDI Heart and Diabetes Institute, P.O. Box 6492, St. Kilda Rd. Central, Melbourne 8008, Australia.
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58
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Smuder AJ, Falk DJ, Sollanek KJ, Nelson WB, Powers SK. Delivery of recombinant adeno-associated virus vectors to rat diaphragm muscle via direct intramuscular injection. Hum Gene Ther Methods 2013; 24:364-71. [PMID: 24006956 PMCID: PMC3869534 DOI: 10.1089/hgtb.2013.055] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Accepted: 09/04/2013] [Indexed: 01/14/2023] Open
Abstract
The diaphragm is the most important inspiratory muscle in all mammals, and ventilatory insufficiency caused by diaphragm dysfunction is the leading cause of morbidity and mortality in many genetic and acquired diseases affecting skeletal muscle. Currently, pharmacological inhibitors, genetically modified animals, and invasive procedures are used to study disorders affecting the diaphragm. However, these methodologies can be problematic because of off-target drug effects and the possible nonphysiological consequences of lifelong genetic alterations. Therefore, alternative methods to study this important respiratory muscle are needed. To resolve this, we have developed a methodology to deliver recombinant adeno-associated virus (rAAV) vectors to the rat diaphragm via direct intramuscular injection. We hypothesized that by direct injection of rAAV into the muscle we can selectively target the diaphragm and establish a novel experimental method for studying signaling pathways and also provide a strategy for effectively using rAAV to protect the diaphragm against disease. This report describes the methods and evidence to support the use of rAAV as a therapeutic intervention to study rat diaphragm biology during conditions that promote diaphragm dysfunction.
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Affiliation(s)
- Ashley J. Smuder
- Department of Applied Physiology and Kinesiology, Center for Exercise Science, University of Florida, Gainesville, FL 32611
| | - Darin J. Falk
- Department of Pediatrics, Powell Gene Therapy Center, University of Florida, Gainesville, FL 32611
| | - Kurt J. Sollanek
- Department of Applied Physiology and Kinesiology, Center for Exercise Science, University of Florida, Gainesville, FL 32611
| | - W. Bradley Nelson
- Department of Applied Physiology and Kinesiology, Center for Exercise Science, University of Florida, Gainesville, FL 32611
| | - Scott K. Powers
- Department of Applied Physiology and Kinesiology, Center for Exercise Science, University of Florida, Gainesville, FL 32611
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59
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Abstract
The molecular mechanisms underlying skeletal muscle maintenance involve interplay between multiple signaling pathways. Under normal physiological conditions, a network of interconnected signals serves to control and coordinate hypertrophic and atrophic messages, culminating in a delicate balance between muscle protein synthesis and proteolysis. Loss of skeletal muscle mass, termed "atrophy", is a diagnostic feature of cachexia seen in settings of cancer, heart disease, chronic obstructive pulmonary disease, kidney disease, and burns. Cachexia increases the likelihood of death from these already serious diseases. Recent studies have further defined the pathways leading to gain and loss of skeletal muscle as well as the signaling events that induce differentiation and post-injury regeneration, which are also essential for the maintenance of skeletal muscle mass. In this review, we summarize and discuss the relevant recent literature demonstrating these previously undiscovered mediators governing anabolism and catabolism of skeletal muscle.
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Affiliation(s)
- Marc A Egerman
- Novartis Institutes for Biomedical Research , Cambridge, MA , USA
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60
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Rhoads RP, Flann KL, Cardinal TR, Rathbone CR, Liu X, Allen RE. Satellite cells isolated from aged or dystrophic muscle exhibit a reduced capacity to promote angiogenesis in vitro. Biochem Biophys Res Commun 2013; 440:399-404. [PMID: 24070607 DOI: 10.1016/j.bbrc.2013.09.085] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2013] [Accepted: 09/16/2013] [Indexed: 11/25/2022]
Abstract
Deficits in skeletal muscle function exist during aging and muscular dystrophy, and suboptimal function has been related to factors such as atrophy, excessive inflammation and fibrosis. Ineffective muscle regeneration underlies each condition and has been attributed to a deficit in myogenic potential of resident stem cells or satellite cells. In addition to reduced myogenic activity, satellite cells may also lose the ability to communicate with vascular cells for coordination of myogenesis and angiogenesis and restoration of proper muscle function. Objectives of the current study were to determine the angiogenic-promoting capacity of satellite cells from two states characterized by dysfunctional skeletal muscle repair, aging and Duchenne muscular dystrophy. An in vitro culture model composed of satellite cells or their conditioned media and rat adipose tissue microvascular fragments (MVF) was used to examine this relationship. Microvascular fragments cultured in the presence of rat satellite cells from adult muscle donors (9-12 month of age) exhibited greater indices of angiogenesis (endothelial cell sprouting, tubule formation and extensive branching) than MVF co-cultured with satellite cells from aged muscle donors (24 month of age). We sought to determine if the differential degree of angiogenesis we observed in the co-culture setting was due to soluble factors produced by each satellite cell age group. Similar to the co-culture experiment, conditioned media produced by adult satellite cells promoted greater angiogenesis than that of aged satellite cells. Next, we examined differences in angiogenesis-stimulating ability of satellite cells from 12 mo old MDX mice or age-matched wild-type mice. A reduction in angiogenesis activity of media conditioned by satellite cells from dystrophic muscle was observed as compared to healthy muscle. Finally, we found reduced gene expression of hypoxia-inducible factor 1α (HIF-1α) and vascular endothelial growth factor (VEGF) in both aged and dystrophic satellite cells compared to their adult and normal counterparts, respectively. These results indicate that functional deficits in satellite cell activities during aging and diseased muscle may extend to their ability to communicate with other cells in their environment, in this case cells involved in angiogenesis.
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Affiliation(s)
- R P Rhoads
- Muscle Biology Group, Department of Animal Sciences, University of Arizona, Tucson, AZ 85724, USA; Department of Animal and Poultry Sciences, Virginia Tech, Blacksburg, VA 24061, USA.
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61
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Silva MC, Amaral MD, Morimoto RI. Neuronal reprograming of protein homeostasis by calcium-dependent regulation of the heat shock response. PLoS Genet 2013; 9:e1003711. [PMID: 24009518 PMCID: PMC3757039 DOI: 10.1371/journal.pgen.1003711] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2013] [Accepted: 06/25/2013] [Indexed: 12/20/2022] Open
Abstract
Protein quality control requires constant surveillance to prevent misfolding, aggregation, and loss of cellular function. There is increasing evidence in metazoans that communication between cells has an important role to ensure organismal health and to prevent stressed cells and tissues from compromising lifespan. Here, we show in C. elegans that a moderate increase in physiological cholinergic signaling at the neuromuscular junction (NMJ) induces the calcium (Ca(2+))-dependent activation of HSF-1 in post-synaptic muscle cells, resulting in suppression of protein misfolding. This protective effect on muscle cell protein homeostasis was identified in an unbiased genome-wide screening for modifiers of protein aggregation, and is triggered by downregulation of gei-11, a Myb-family factor and proposed regulator of the L-type acetylcholine receptor (AChR). This, in-turn, activates the voltage-gated Ca(2+) channel, EGL-19, and the sarcoplasmic reticulum ryanodine receptor in response to acetylcholine signaling. The release of calcium into the cytoplasm of muscle cells activates Ca(2+)-dependent kinases and induces HSF-1-dependent expression of cytoplasmic chaperones, which suppress misfolding of metastable proteins and stabilize the folding environment of muscle cells. This demonstrates that the heat shock response (HSR) can be activated in muscle cells by neuronal signaling across the NMJ to protect proteome health.
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Affiliation(s)
- M. Catarina Silva
- Department of Molecular Biosciences, Rice Institute for Biomedical Research, Northwestern University, Evanston, Illinois, United States of America
- Faculty of Sciences, Centre for Biodiversity, Functional and Integrative Genomics (BioFIG), University of Lisboa, Lisboa, Portugal
| | - Margarida D. Amaral
- Faculty of Sciences, Centre for Biodiversity, Functional and Integrative Genomics (BioFIG), University of Lisboa, Lisboa, Portugal
- Centre of Human Genetics, National Institute of Health, Lisboa, Portugal
| | - Richard I. Morimoto
- Department of Molecular Biosciences, Rice Institute for Biomedical Research, Northwestern University, Evanston, Illinois, United States of America
- * E-mail:
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62
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Castets P, Lin S, Rion N, Di Fulvio S, Romanino K, Guridi M, Frank S, Tintignac LA, Sinnreich M, Rüegg MA. Sustained activation of mTORC1 in skeletal muscle inhibits constitutive and starvation-induced autophagy and causes a severe, late-onset myopathy. Cell Metab 2013; 17:731-44. [PMID: 23602450 DOI: 10.1016/j.cmet.2013.03.015] [Citation(s) in RCA: 186] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/31/2012] [Revised: 11/22/2012] [Accepted: 03/21/2013] [Indexed: 10/26/2022]
Abstract
Autophagy is a catabolic process that ensures homeostatic cell clearance and is deregulated in a growing number of myopathological conditions. Although FoxO3 was shown to promote the expression of autophagy-related genes in skeletal muscle, the mechanisms triggering autophagy are unclear. We show that TSC1-deficient mice (TSCmKO), characterized by sustained activation of mTORC1, develop a late-onset myopathy related to impaired autophagy. In young TSCmKO mice, constitutive and starvation-induced autophagy is blocked at the induction steps via mTORC1-mediated inhibition of Ulk1, despite FoxO3 activation. Rapamycin is sufficient to restore autophagy in TSCmKO mice and improves the muscle phenotype of old mutant mice. Inversely, abrogation of mTORC1 signaling by depletion of raptor induces autophagy regardless of FoxO inhibition. Thus, mTORC1 is the dominant regulator of autophagy induction in skeletal muscle and ensures a tight coordination of metabolic pathways. These findings may open interesting avenues for therapeutic strategies directed toward autophagy-related muscle diseases.
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63
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Bentzinger CF, Lin S, Romanino K, Castets P, Guridi M, Summermatter S, Handschin C, Tintignac LA, Hall MN, Rüegg MA. Differential response of skeletal muscles to mTORC1 signaling during atrophy and hypertrophy. Skelet Muscle 2013; 3:6. [PMID: 23497627 PMCID: PMC3622636 DOI: 10.1186/2044-5040-3-6] [Citation(s) in RCA: 106] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2012] [Accepted: 02/15/2013] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND Skeletal muscle mass is determined by the balance between protein synthesis and degradation. Mammalian target of rapamycin complex 1 (mTORC1) is a master regulator of protein translation and has been implicated in the control of muscle mass. Inactivation of mTORC1 by skeletal muscle-specific deletion of its obligatory component raptor results in smaller muscles and a lethal dystrophy. Moreover, raptor-deficient muscles are less oxidative through changes in the expression PGC-1α, a critical determinant of mitochondrial biogenesis. These results suggest that activation of mTORC1 might be beneficial to skeletal muscle by providing resistance to muscle atrophy and increasing oxidative function. Here, we tested this hypothesis by deletion of the mTORC1 inhibitor tuberous sclerosis complex (TSC) in muscle fibers. METHOD Skeletal muscles of mice with an acute or a permanent deletion of raptor or TSC1 were examined using histological, biochemical and molecular biological methods. Response of the muscles to changes in mechanical load and nerve input was investigated by ablation of synergistic muscles or by denervation . RESULTS Genetic deletion or knockdown of raptor, causing inactivation of mTORC1, was sufficient to prevent muscle growth and enhance muscle atrophy. Conversely, short-term activation of mTORC1 by knockdown of TSC induced muscle fiber hypertrophy and atrophy-resistance upon denervation, in both fast tibialis anterior (TA) and slow soleus muscles. Surprisingly, however, sustained activation of mTORC1 by genetic deletion of Tsc1 caused muscle atrophy in all but soleus muscles. In contrast, oxidative capacity was increased in all muscles examined. Consistently, TSC1-deficient soleus muscle was atrophy-resistant whereas TA underwent normal atrophy upon denervation. Moreover, upon overloading, plantaris muscle did not display enhanced hypertrophy compared to controls. Biochemical analysis indicated that the atrophy response of muscles was based on the suppressed phosphorylation of PKB/Akt via feedback inhibition by mTORC1 and subsequent increased expression of the E3 ubiquitin ligases MuRF1 and atrogin-1/MAFbx. In contrast, expression of both E3 ligases was not increased in soleus muscle suggesting the presence of compensatory mechanisms in this muscle. CONCLUSIONS Our study shows that the mTORC1- and the PKB/Akt-FoxO pathways are tightly interconnected and differentially regulated depending on the muscle type. These results indicate that long-term activation of the mTORC1 signaling axis is not a therapeutic option to promote muscle growth because of its strong feedback induction of the E3 ubiquitin ligases involved in protein degradation.
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Affiliation(s)
| | - Shuo Lin
- Biozentrum, University of Basel, Basel, CH-4056, Switzerland
| | - Klaas Romanino
- Biozentrum, University of Basel, Basel, CH-4056, Switzerland
| | - Perrine Castets
- Biozentrum, University of Basel, Basel, CH-4056, Switzerland.,Neuromuscular Research Center, Department of Biomedicine, University of Basel, Basel, CH-4056, Switzerland
| | - Maitea Guridi
- Biozentrum, University of Basel, Basel, CH-4056, Switzerland
| | | | | | - Lionel A Tintignac
- Biozentrum, University of Basel, Basel, CH-4056, Switzerland.,INRA, UMR866, Université Montpellier 1, Université Montpellier 2, Montpellier, France
| | - Michael N Hall
- Biozentrum, University of Basel, Basel, CH-4056, Switzerland
| | - Markus A Rüegg
- Biozentrum, University of Basel, Basel, CH-4056, Switzerland
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64
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Guillory B, Splenser A, Garcia J. The Role of Ghrelin in Anorexia–Cachexia Syndromes. ANOREXIA 2013; 92:61-106. [DOI: 10.1016/b978-0-12-410473-0.00003-9] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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65
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Abstract
Cirrhosis is the consequence of progression of many forms of necro-inflammatory disorders of the liver with hepatic fibrosis, hepatocellular dysfunction, and vascular remodeling. Reversing the primary hepatic disorder, liver transplantation, and controlling the complications are the major management goals. Since the former options are not available to the majority of cirrhotics, treating complications remains the mainstay of therapy. Sarcopenia and/or cachexia is the most common complication and adversely affects survival, quality of life, development of other complications of cirrhosis, and outcome after liver transplantation. With the increase in number of cirrhotic patients with hepatitis C and nonalcoholic fatty liver disease, the number of patients waiting for a liver transplantation is likely to continue to increase above the currently estimated 72.3/100,000 population. One of the critical clinical questions is to determine if we can treat sarcopenia of cirrhosis without transplantation. No effective therapies exist to treat sarcopenia because the mechanism(s) of sarcopenia in cirrhosis is as yet unknown. The reasons for this include the predominantly descriptive studies to date and the advances in our understanding of skeletal muscle biology and molecular regulation of atrophy and hypertrophy not being translated into the clinical practice of hepatology. Satellite cell biology, muscle autophagy and apoptosis, and molecular signaling abnormalities in the skeletal muscle of cirrhotics are also not known. Aging of the cirrhotic and transplanted population, use of mTOR inhibitors, and the lack of definitive outcome measures to define sarcopenia and cachexia in this population add to the difficulty in increasing our understanding of hepatic sarcopenia/cachexia and developing treatment options. Recent data on the role of myostatin, AMP kinase, impaired mTOR signaling resulting in anabolic resistance in animal models, and the rapidly developing field of nutriceuticals as signaling molecules need to be evaluated in human cirrhotics. Finally, the benefits of exercise reported in other disease states with sarcopenia may not be safe in cirrhotics due to the risk of gastrointestinal variceal bleeding due to an increase in portal pressure. This article focuses on the problems facing both muscle biologists and hepatologists in developing a comprehensive approach to sarcopenia in cirrhosis.
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Affiliation(s)
- Srinivasan Dasarathy
- Department of Gastroenterology, Hepatology and Pathobiology, Lerner Research Institute, Cleveland Clinic, NE4-208, 9500 Euclid Avenue, Cleveland, OH, 44195, USA,
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Li Z, Gilbert JA, Zhang Y, Zhang M, Qiu Q, Ramanujan K, Shavlakadze T, Eash JK, Scaramozza A, Goddeeris MM, Kirsch DG, Campbell KP, Brack AS, Glass DJ. An HMGA2-IGF2BP2 axis regulates myoblast proliferation and myogenesis. Dev Cell 2012. [PMID: 23177649 DOI: 10.1016/j.devcel.2012.10.019] [Citation(s) in RCA: 124] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
A group of genes that are highly and specifically expressed in proliferating skeletal myoblasts during myogenesis was identified. Expression of one of these genes, Hmga2, increases coincident with satellite cell activation, and later its expression significantly declines correlating with fusion of myoblasts into myotubes. Hmga2 knockout mice exhibit impaired muscle development and reduced myoblast proliferation, while overexpression of HMGA2 promotes myoblast growth. This perturbation in proliferation can be explained by the finding that HMGA2 directly regulates the RNA-binding protein IGF2BP2. Add-back of IGF2BP2 rescues the phenotype. IGF2BP2 in turn binds to and controls the translation of a set of mRNAs, including c-myc, Sp1, and Igf1r. These data demonstrate that the HMGA2-IGF2BP2 axis functions as a key regulator of satellite cell activation and therefore skeletal muscle development.
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Affiliation(s)
- Zhizhong Li
- Novartis Institutes for Biomedical Research, Cambridge, MA 02139, USA
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67
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Gardner S, Anguiano M, Rotwein P. Defining Akt actions in muscle differentiation. Am J Physiol Cell Physiol 2012; 303:C1292-300. [PMID: 23076793 DOI: 10.1152/ajpcell.00259.2012] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Muscle development in childhood and muscle regeneration in adults are highly regulated processes that are necessary for reaching and maintaining optimal muscle mass and strength throughout life. Muscle repair after injury relies on stem cells, termed satellite cells, whose activity is controlled by complex signals mediated by cell-cell contact, by growth factors, and by hormones, which interact with genetic programs controlled by myogenic transcription factors. Insulin-like growth factors (IGFs) play key roles in muscle development and help coordinate muscle repair after injury, primarily by stimulating the phosphatidylinositol 3-kinase-Akt signaling pathway, and both in vitro and in vivo studies have shown that Akt kinase activity is critical for optimal muscle growth and regeneration. Here we find that of the two Akts expressed in muscle, Akt1 is essential for initiation of differentiation in culture and is required for normal myoblast motility, while Akt2 is dispensable. Although Akt2 deficiency did lead to diminished myotube maturation, as assessed by a decline in myofiber area and in fusion index, either Akt1 or Akt2 could restore these processes toward normal. Thus levels of Akt expression rather than distinct actions of individual Akt species are critical for normal myofiber development during the later stages of muscle differentiation.
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Affiliation(s)
- Samantha Gardner
- Department of Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, OR 97239-3098, USA
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68
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Olguín HC, Pisconti A. Marking the tempo for myogenesis: Pax7 and the regulation of muscle stem cell fate decisions. J Cell Mol Med 2012; 16:1013-25. [PMID: 21615681 PMCID: PMC4365881 DOI: 10.1111/j.1582-4934.2011.01348.x] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Post-natal growth and regeneration of skeletal muscle is highly dependent on a population of resident myogenic precursors known as satellite cells. Transcription factors from the Pax gene family, Pax3 and Pax7, are critical for satellite cell biogenesis, survival and potentially self-renewal; however, the underlying molecular mechanisms remain unsolved. This is particularly true in the case of Pax7, which appears to regulate myogenesis at multiple levels. Accordingly, recent data have highlighted the importance of a functional relationship between Pax7 and the MyoD family of muscle regulatory transcription factors during normal muscle formation and disease. Here we will critically review key findings suggesting that Pax7 may play a dual role by promoting resident muscle progenitors to commit to the skeletal muscle lineage while preventing terminal differentiation, thus keeping muscle progenitors poised to differentiate upon environmental cues. In addition, potential regulatory mechanisms for the control of Pax7 activity will be proposed.
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Affiliation(s)
- Hugo C Olguín
- Departamento Biología Celular y Molecular, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile.
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69
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Meinen S, Lin S, Ruegg MA. Angiotensin II type 1 receptor antagonists alleviate muscle pathology in the mouse model for laminin-α2-deficient congenital muscular dystrophy (MDC1A). Skelet Muscle 2012; 2:18. [PMID: 22943509 PMCID: PMC3598380 DOI: 10.1186/2044-5040-2-18] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2012] [Accepted: 07/31/2012] [Indexed: 12/22/2022] Open
Abstract
Background Laminin-α2-deficient congenital muscular dystrophy (MDC1A) is a severe muscle-wasting disease for which no curative treatment is available. Antagonists of the angiotensin II receptor type 1 (AT1), including the anti-hypertensive drug losartan, have been shown to block also the profibrotic action of transforming growth factor (TGF)-β and thereby ameliorate disease progression in mouse models of Marfan syndrome. Because fibrosis and failure of muscle regeneration are the main reasons for the severe disease course of MDC1A, we tested whether L-158809, an analog derivative of losartan, could ameliorate the dystrophy in dyW/dyW mice, the best-characterized model of MDC1A. Methods L-158809 was given in food to dyW/dyW mice at the age of 3 weeks, and the mice were analyzed at the age of 6 to 7 weeks. We examined the effect of L-158809 on muscle histology and on muscle regeneration after injury as well as the locomotor activity and muscle strength of the mice. Results We found that TGF-β signaling in the muscles of the dyW/dyW mice was strongly increased, and that L-158809 treatment suppressed this signaling. Consequently, L-158809 reduced fibrosis and inflammation in skeletal muscle of dyW/dyW mice, and largely restored muscle regeneration after toxin-induced injury. Mice showed improvement in their locomotor activity and grip strength, and their body weight was significantly increased. Conclusion These data provide evidence that AT1 antagonists ameliorate several hallmarks of MDC1A in dyW/dyW mice, the best-characterized mouse model for this disease. Because AT1 antagonists are well tolerated in humans and widely used in clinical practice, these results suggest that losartan may offer a potential future treatment of patients with MDC1A.
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Affiliation(s)
- Sarina Meinen
- Biozentrum, University of Basel, Basel, Switzerland.
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Fanzani A, Conraads VM, Penna F, Martinet W. Molecular and cellular mechanisms of skeletal muscle atrophy: an update. J Cachexia Sarcopenia Muscle 2012; 3:163-79. [PMID: 22673968 PMCID: PMC3424188 DOI: 10.1007/s13539-012-0074-6] [Citation(s) in RCA: 234] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/09/2012] [Accepted: 05/13/2012] [Indexed: 02/06/2023] Open
Abstract
Skeletal muscle atrophy is defined as a decrease in muscle mass and it occurs when protein degradation exceeds protein synthesis. Potential triggers of muscle wasting are long-term immobilization, malnutrition, severe burns, aging as well as various serious and often chronic diseases, such as chronic heart failure, obstructive lung disease, renal failure, AIDS, sepsis, immune disorders, cancer, and dystrophies. Interestingly, a cooperation between several pathophysiological factors, including inappropriately adapted anabolic (e.g., growth hormone, insulin-like growth factor 1) and catabolic proteins (e.g., tumor necrosis factor alpha, myostatin), may tip the balance towards muscle-specific protein degradation through activation of the proteasomal and autophagic systems or the apoptotic pathway. Based on the current literature, we present an overview of the molecular and cellular mechanisms that contribute to muscle wasting. We also focus on the multifacetted therapeutic approach that is currently employed to prevent the development of muscle wasting and to counteract its progression. This approach includes adequate nutritional support, implementation of exercise training, and possible pharmacological compounds.
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Affiliation(s)
- Alessandro Fanzani
- Department of Biomedical Sciences and Biotechnologies and Interuniversitary Institute of Myology (IIM), University of Brescia, viale Europa 11, 25123, Brescia, Italy,
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71
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Bentzinger CF, Wang YX, von Maltzahn J, Rudnicki MA. The emerging biology of muscle stem cells: implications for cell-based therapies. Bioessays 2012; 35:231-41. [PMID: 22886714 PMCID: PMC3594813 DOI: 10.1002/bies.201200063] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Cell-based therapies for degenerative diseases of the musculature remain on the verge of feasibility. Myogenic cells are relatively abundant, accessible, and typically harbor significant proliferative potential ex vivo. However, their use for therapeutic intervention is limited due to several critical aspects of their complex biology. Recent insights based on mouse models have advanced our understanding of the molecular mechanisms controlling the function of myogenic progenitors significantly. Moreover, the discovery of atypical myogenic cell types with the ability to cross the blood-muscle barrier has opened exciting new therapeutic avenues. In this paper, we outline the major problems that are currently associated with the manipulation of myogenic cells and discuss promising strategies to overcome these obstacles.
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Affiliation(s)
- C Florian Bentzinger
- The Sprott Centre for Stem Cell Research, Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada
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72
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Holt LJ, Turner N, Mokbel N, Trefely S, Kanzleiter T, Kaplan W, Ormandy CJ, Daly RJ, Cooney GJ. Grb10 regulates the development of fiber number in skeletal muscle. FASEB J 2012; 26:3658-69. [DOI: 10.1096/fj.11-199349] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Lowenna J. Holt
- Diabetes and Obesity Research ProgramGarvan Institute of Medical ResearchSydneyNew South WalesAustralia
| | - Nigel Turner
- Diabetes and Obesity Research ProgramGarvan Institute of Medical ResearchSydneyNew South WalesAustralia
- St. Vincent's Hospital Clinical SchoolUniversity of New South WalesSydneyNew South WalesAustralia
| | - Nancy Mokbel
- Diabetes and Obesity Research ProgramGarvan Institute of Medical ResearchSydneyNew South WalesAustralia
| | - Sophie Trefely
- Diabetes and Obesity Research ProgramGarvan Institute of Medical ResearchSydneyNew South WalesAustralia
| | - Timo Kanzleiter
- Diabetes and Obesity Research ProgramGarvan Institute of Medical ResearchSydneyNew South WalesAustralia
| | - Warren Kaplan
- Peter Wills Bioinformatics CentreGarvan Institute of Medical ResearchSydneyNew South WalesAustralia
| | - Christopher J. Ormandy
- Cancer Research ProgramGarvan Institute of Medical ResearchSydneyNew South WalesAustralia
- St. Vincent's Hospital Clinical SchoolUniversity of New South WalesSydneyNew South WalesAustralia
| | - Roger J. Daly
- Cancer Research ProgramGarvan Institute of Medical ResearchSydneyNew South WalesAustralia
- St. Vincent's Hospital Clinical SchoolUniversity of New South WalesSydneyNew South WalesAustralia
| | - Gregory J. Cooney
- Diabetes and Obesity Research ProgramGarvan Institute of Medical ResearchSydneyNew South WalesAustralia
- St. Vincent's Hospital Clinical SchoolUniversity of New South WalesSydneyNew South WalesAustralia
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73
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Vadász I, Weiss CH, Sznajder JI. Ubiquitination and proteolysis in acute lung injury. Chest 2012; 141:763-771. [PMID: 22396561 DOI: 10.1378/chest.11-1660] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Ubiquitination is a posttranslational modification that regulates a variety of cellular functions depending on timing, subcellular localization, and type of tagging, as well as modulators of ubiquitin binding leading to proteasomal or lysosomal degradation or nonproteolytic modifications. Ubiquitination plays an important role in the pathogenesis of acute lung injury (ALI) and other lung diseases with pathologies secondary to inflammation, mechanical ventilation, and decreased physical mobility. Particularly, ubiquitination has been shown to affect alveolar epithelial barrier function and alveolar edema clearance by targeting the Na,K-ATPase and epithelial Na(+) channels upon lung injury. Notably, the proteasomal system also exhibits distinct functions in the extracellular space, which may contribute to the pathogenesis of ALI and other pulmonary diseases. Better understanding of these mechanisms may ultimately lead to novel therapeutic modalities by targeting elements of the ubiquitination pathway.
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Affiliation(s)
- István Vadász
- Department of Internal Medicine, University of Giessen Lung Center, Justus Liebig University, Giessen, Germany.
| | - Curtis H Weiss
- Division of Pulmonary and Critical Care Medicine, Northwestern University, Feinberg School of Medicine, Chicago, IL
| | - Jacob I Sznajder
- Division of Pulmonary and Critical Care Medicine, Northwestern University, Feinberg School of Medicine, Chicago, IL
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74
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Wu Y, Zhao J, Zhao W, Pan J, Bauman WA, Cardozo CP. Nandrolone normalizes determinants of muscle mass and fiber type after spinal cord injury. J Neurotrauma 2012; 29:1663-75. [PMID: 22208735 DOI: 10.1089/neu.2011.2203] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Spinal cord injury (SCI) results in atrophy of skeletal muscle and changes from slow oxidative to fast glycolytic fibers, which may reflect reduced levels of peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α), increased myostatin signaling, or both. In animals, testosterone reduces loss of muscle fiber cross-sectional area and activity of enzymes of energy metabolism. To identify the molecular mechanisms behind the benefits of androgens on paralyzed muscle, male rats were spinal cord transected and treated for 8 weeks with vehicle, testosterone at a physiological replacement dose, or testosterone plus nandrolone, an anabolic steroid. Treatments were initiated immediately after SCI and continued until the day animals were euthanized. In the SCI animals, gastrocnemius muscle mass was significantly increased by testosterone plus nandrolone, but not by testosterone alone. Both treatments significantly reduced nuclear content of Smad2/3 and mRNA levels of activin receptor IIB and follistatin-like 3. Testosterone alone or with nandrolone reversed SCI-induced declines in cellular and nuclear levels of PGC-1α protein and PGC-1α mRNA levels. For PGC-1α target genes, testosterone plus nandrolone partially reversed SCI-induced decreases in levels of proteins without corresponding increases in their mRNA levels. Thus, the findings demonstrate that following SCI, signaling through activin receptors and Smad2/3 is increased, and that androgens suppress activation of this signaling pathway. The findings also indicate that androgens upregulate PGC-1α in paralyzed muscle and promote its nuclear localization, but that these effects are insufficient to fully activate transcription of PGC-1α target genes. Furthermore, the transcription of these genes is not tightly coupled with their translation.
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Affiliation(s)
- Yong Wu
- Center of Excellence for the Medical Consequences of SCI, James J. Peters VA Medical Center, Bronx, NY, USA
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75
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Nedergaard A, Jespersen JG, Pingel J, Christensen B, Sroczynski N, Langberg H, Kjaer M, Schjerling P. Effects of 2 weeks lower limb immobilization and two separate rehabilitation regimens on gastrocnemius muscle protein turnover signaling and normalization genes. BMC Res Notes 2012; 5:166. [PMID: 22455386 PMCID: PMC3405443 DOI: 10.1186/1756-0500-5-166] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2011] [Accepted: 03/28/2012] [Indexed: 02/03/2023] Open
Abstract
BACKGROUND Limb immobilization causes a rapid loss of muscle mass and strength that requires appropriate rehabilitation to ensure restoration of normal function. Whereas the knowledge of muscle mass signaling with immobilization has increased in recent years, the molecular regulation in the rehabilitation of immobilization-induced muscle atrophy is only sparsely studied. To investigate the phosphorylation and expression of candidate key molecular muscle mass regulators after immobilization and subsequent rehabilitation we performed two separate studies. METHODS We immobilized the lower limb for 2 weeks followed by the in-house hospital standard physiotherapy rehabilitation (Study 1). Secondly, we conducted an intervention study using the same 2 weeks immobilization protocol during which protein/carbohydrate supplementation was given. This was followed by 6 weeks of rehabilitation in the form of resistance training and continued protein/carbohydrate supplementation (Study 2). We obtained muscle biopsies from the medial gastrocnemius prior to immobilization (PRE), post-immobilization (IMMO) and post-rehabilitation (REHAB) and measured protein expression and phosphorylation of Akt, mTOR, S6k, 4E-BP1, GSK3β, ubiquitin and MURF1 and mRNA expression of Atrogin-1, MURF1, FOXO1, 3 and 4 as well as appropriate housekeeping genes. RESULTS In both studies, no changes in protein expression or phosphorylation for any measured protein were observed. In Study 1, FOXO3 and FOXO4 mRNA expression decreased after IMMO and REHAB compared to PRE, whereas other mRNAs remained unchanged. Interestingly, we found significant changes in expression of the putative housekeeping genes GAPDH, HADHA and S26 with immobilization in both studies. CONCLUSIONS In neither study, the changes in muscle mass associated with immobilization and rehabilitation were accompanied by expected changes in expression of atrophy-related genes or phosphorylation along the Akt axis. Unexpectedly, we observed significant changes in several of the so-called housekeeping genes GAPDH, HADHA and S26 with immobilization in both studies, thereby questioning the usefulness of these genes for normalization of RNA data purposes in muscle immobilization studies.
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Affiliation(s)
- Anders Nedergaard
- Institute of Sports Medicine, Department of Orthopedic Surgery M, Bispebjerg Hospital, Copenhagen, Denmark.
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Punga AR, Ruegg MA. Signaling and aging at the neuromuscular synapse: lessons learnt from neuromuscular diseases. Curr Opin Pharmacol 2012; 12:340-6. [PMID: 22365504 DOI: 10.1016/j.coph.2012.02.002] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2011] [Revised: 01/26/2012] [Accepted: 02/02/2012] [Indexed: 12/30/2022]
Abstract
The neuromuscular junction (NMJ) is a specialized synapse between motor neurons and skeletal muscle with a complex signaling network that assures highly reliable neuromuscular transmission. Diseases of the NMJ cause skeletal muscle fatigue and include inherited and acquired disorders that affect presynaptic, intrasynaptic or postsynaptic components. Moreover, fragmentation of the NMJ contributes to sarcopenia, the loss of muscle mass during aging. Studies from recent years indicate that the formation and stabilization of NMJs differs between various muscles and that this difference affects their response under pathological conditions. This review summarizes the most important mechanisms involved in the development, maintenance and dysfunction of the NMJ and it discusses their significance in myasthenic disorders and aging and as targets for possible future treatment of NMJ dysfunction.
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Affiliation(s)
- Anna Rostedt Punga
- Institute of Neuroscience, Department of Clinical Neurophysiology, Uppsala University Hospital, Uppsala, Sweden
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77
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Periyalwar P, Dasarathy S. Malnutrition in cirrhosis: contribution and consequences of sarcopenia on metabolic and clinical responses. Clin Liver Dis 2012; 16:95-131. [PMID: 22321468 PMCID: PMC4383161 DOI: 10.1016/j.cld.2011.12.009] [Citation(s) in RCA: 175] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Malnutrition is the most common, reversible complication of cirrhosis that adversely affects survival, response to other complications, and quality of life. Sarcopenia, or loss of skeletal muscle mass, and loss of adipose tissue and altered substrate use as a source of energy are the 2 major components of malnutrition in cirrhosis. Current therapies include high protein supplementation especially as a late evening snack. Exercise protocols have the potential of aggravating hyperammonemia and portal hypertension. Recent advances in understanding the molecular regulation of muscle mass has helped identify potential novel therapeutic targets including myostatin antagonists, and mTOR resistance.
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Affiliation(s)
- Pranav Periyalwar
- Department of Gastroenterology, Metrohealth Medical Center, 2500 Metrohealth Drive, Cleveland, OH 44109, USA
- Department of Gastroenterology and Hepatology, Lerner Research Institute, Cleveland Clinic, 9500 Euclid Avenue, NE4-208, Cleveland, OH 44195, USA
| | - Srinivasan Dasarathy
- Department of Gastroenterology and Hepatology, Lerner Research Institute, Cleveland Clinic, 9500 Euclid Avenue, NE4-208, Cleveland, OH 44195, USA
- Department of Pathobiology, Lerner Research Institute, Cleveland Clinic, 9500 Euclid Avenue, NE4-208, Cleveland, OH 44195, USA
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Silva MC, Fox S, Beam M, Thakkar H, Amaral MD, Morimoto RI. A genetic screening strategy identifies novel regulators of the proteostasis network. PLoS Genet 2011; 7:e1002438. [PMID: 22242008 PMCID: PMC3248563 DOI: 10.1371/journal.pgen.1002438] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2011] [Accepted: 11/12/2011] [Indexed: 12/14/2022] Open
Abstract
A hallmark of diseases of protein conformation and aging is the appearance of protein aggregates associated with cellular toxicity. We posit that the functional properties of the proteostasis network (PN) protect the proteome from misfolding and combat the proteotoxic events leading to cellular pathology. In this study, we have identified new components of the proteostasis network that can suppress aggregation and proteotoxicity, by performing RNA interference (RNAi) genetic screens for multiple unrelated conformationally challenged cytoplasmic proteins expressed in Caenorhabditis elegans. We identified 88 suppressors of polyglutamine (polyQ) aggregation, of which 63 modifiers also suppressed aggregation of mutant SOD1G93A. Of these, only 23 gene-modifiers suppressed aggregation and restored animal motility, revealing that aggregation and toxicity can be genetically uncoupled. Nine of these modifiers were shown to be effective in restoring the folding and function of multiple endogenous temperature-sensitive (TS) mutant proteins, of which five improved folding in a HSF-1–dependent manner, by inducing cytoplasmic chaperones. This triage screening strategy also identified a novel set of PN regulatory components that, by altering metabolic and RNA processing functions, establish alternate cellular environments not generally dependent on stress response activation and that are broadly protective against misfolded and aggregation-prone proteins. A common characteristic of protein conformational diseases is the appearance of protein aggregates associated with late-onset symptoms. Here, we have taken an unbiased genetic approach to test the hypothesis that protein aggregation and toxicity are co-linked genetic traits that are regulated by a common proteostasis network. To address this, we took advantage of the tractable genetic model Caenorhabditis elegans expressing expanded polyglutamines (polyQ) and performed a genome-wide RNA interference (RNAi) screen to identify genes that altered the proteostasis environment and suppressed aggregation and toxicity. These modifiers were subsequently tested on animals expressing mutant SOD1 and on animals expressing endogenous proteins with temperature-sensitive mutations. This screening triage resulted in the identification of nine genes with effects on protein folding, corresponding to new proteostasis pathways involved in metabolism and RNA processing functions.
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Affiliation(s)
- M. Catarina Silva
- Department of Molecular Biosciences, Rice Institute for Biomedical Research, Northwestern University, Evanston, Illinois, United States of America
- Faculty of Sciences, Centre for Biodiversity, Functional and Integrative Genomics (BioFIG), University of Lisboa, Lisboa, Portugal
| | - Susan Fox
- Department of Molecular Biosciences, Rice Institute for Biomedical Research, Northwestern University, Evanston, Illinois, United States of America
| | - Monica Beam
- Department of Molecular Biosciences, Rice Institute for Biomedical Research, Northwestern University, Evanston, Illinois, United States of America
- Department of Biomedical Engineering, Northwestern University, Evanston, Illinois, United States of America
| | - Happy Thakkar
- Department of Molecular Biosciences, Rice Institute for Biomedical Research, Northwestern University, Evanston, Illinois, United States of America
| | - Margarida D. Amaral
- Faculty of Sciences, Centre for Biodiversity, Functional and Integrative Genomics (BioFIG), University of Lisboa, Lisboa, Portugal
- Centre of Human Genetics, National Institute of Health, Lisboa, Portugal
| | - Richard I. Morimoto
- Department of Molecular Biosciences, Rice Institute for Biomedical Research, Northwestern University, Evanston, Illinois, United States of America
- * E-mail:
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Dupont-Versteegden EE, Waters C. No muscle atrophy without GSK-3β. Focus on “Glycogen synthase kinase-3β is required for the induction of skeletal muscle atrophy”. Am J Physiol Cell Physiol 2011; 301:C980-1. [DOI: 10.1152/ajpcell.00310.2011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
| | - Christine Waters
- Department of Rehabilitation Sciences, College of Health Sciences, University of Kentucky, Lexington, Kentucky
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Mamchaoui K, Trollet C, Bigot A, Negroni E, Chaouch S, Wolff A, Kandalla PK, Marie S, Di Santo J, St Guily JL, Muntoni F, Kim J, Philippi S, Spuler S, Levy N, Blumen SC, Voit T, Wright WE, Aamiri A, Butler-Browne G, Mouly V. Immortalized pathological human myoblasts: towards a universal tool for the study of neuromuscular disorders. Skelet Muscle 2011; 1:34. [PMID: 22040608 PMCID: PMC3235972 DOI: 10.1186/2044-5040-1-34] [Citation(s) in RCA: 198] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2011] [Accepted: 11/01/2011] [Indexed: 11/29/2022] Open
Abstract
Background Investigations into both the pathophysiology and therapeutic targets in muscle dystrophies have been hampered by the limited proliferative capacity of human myoblasts. Isolation of reliable and stable immortalized cell lines from patient biopsies is a powerful tool for investigating pathological mechanisms, including those associated with muscle aging, and for developing innovative gene-based, cell-based or pharmacological biotherapies. Methods Using transduction with both telomerase-expressing and cyclin-dependent kinase 4-expressing vectors, we were able to generate a battery of immortalized human muscle stem-cell lines from patients with various neuromuscular disorders. Results The immortalized human cell lines from patients with Duchenne muscular dystrophy, facioscapulohumeral muscular dystrophy, oculopharyngeal muscular dystrophy, congenital muscular dystrophy, and limb-girdle muscular dystrophy type 2B had greatly increased proliferative capacity, and maintained their potential to differentiate both in vitro and in vivo after transplantation into regenerating muscle of immunodeficient mice. Conclusions Dystrophic cellular models are required as a supplement to animal models to assess cellular mechanisms, such as signaling defects, or to perform high-throughput screening for therapeutic molecules. These investigations have been conducted for many years on cells derived from animals, and would greatly benefit from having human cell models with prolonged proliferative capacity. Furthermore, the possibility to assess in vivo the regenerative capacity of these cells extends their potential use. The innovative cellular tools derived from several different neuromuscular diseases as described in this report will allow investigation of the pathophysiology of these disorders and assessment of new therapeutic strategies.
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Affiliation(s)
- Kamel Mamchaoui
- Thérapie des maladies du muscle strié, Institut de Myologie, UM76, UPMC Université Paris 6, Paris, France.,INSERM U974, Paris, France.,CNRS UMR 7215, Paris, France
| | - Capucine Trollet
- Thérapie des maladies du muscle strié, Institut de Myologie, UM76, UPMC Université Paris 6, Paris, France.,INSERM U974, Paris, France.,CNRS UMR 7215, Paris, France
| | - Anne Bigot
- Thérapie des maladies du muscle strié, Institut de Myologie, UM76, UPMC Université Paris 6, Paris, France.,INSERM U974, Paris, France.,CNRS UMR 7215, Paris, France
| | - Elisa Negroni
- Thérapie des maladies du muscle strié, Institut de Myologie, UM76, UPMC Université Paris 6, Paris, France.,INSERM U974, Paris, France.,CNRS UMR 7215, Paris, France
| | - Soraya Chaouch
- Thérapie des maladies du muscle strié, Institut de Myologie, UM76, UPMC Université Paris 6, Paris, France.,INSERM U974, Paris, France.,CNRS UMR 7215, Paris, France
| | - Annie Wolff
- Thérapie des maladies du muscle strié, Institut de Myologie, UM76, UPMC Université Paris 6, Paris, France.,INSERM U974, Paris, France.,CNRS UMR 7215, Paris, France
| | - Prashanth K Kandalla
- Thérapie des maladies du muscle strié, Institut de Myologie, UM76, UPMC Université Paris 6, Paris, France.,INSERM U974, Paris, France.,CNRS UMR 7215, Paris, France
| | - Solenne Marie
- Thérapie des maladies du muscle strié, Institut de Myologie, UM76, UPMC Université Paris 6, Paris, France.,INSERM U974, Paris, France.,CNRS UMR 7215, Paris, France
| | - James Di Santo
- Innate Immunity Unit, INSERM U 668, Institut Pasteur, Paris, France
| | - Jean Lacau St Guily
- Thérapie des maladies du muscle strié, Institut de Myologie, UM76, UPMC Université Paris 6, Paris, France.,INSERM U974, Paris, France.,CNRS UMR 7215, Paris, France.,Service d'Oto-Rhino-Laryngologie et de Chirurgie Cervico-Faciale, Faculté de Médecine St Antoine, Université Pierre et Marie Curie, Hôpital Tenon, Paris, France
| | - Francesco Muntoni
- The Dubowitz Neuromuscular Centre, Institute of Child Health, University College, London, UK
| | - Jihee Kim
- The Dubowitz Neuromuscular Centre, Institute of Child Health, University College, London, UK
| | - Susanne Philippi
- Thérapie des maladies du muscle strié, Institut de Myologie, UM76, UPMC Université Paris 6, Paris, France.,Muscle Research Unit, Experimental and Clinical Research Center, Charité University Hospital and Max Delbrück Center for Molecular Medicine, Berlin, Germany
| | - Simone Spuler
- Muscle Research Unit, Experimental and Clinical Research Center, Charité University Hospital and Max Delbrück Center for Molecular Medicine, Berlin, Germany
| | - Nicolas Levy
- Faculté de Médecine de Marseille, Université de la Méditerranée, Inserm UMRS 910 Génétique Médicale et Génomique Fonctionnelle, Marseille, France
| | - Sergiu C Blumen
- Department of Neurology, Hillel Yaffe Medical Center, PO Box 169, Hadera, 38100, Israel
| | - Thomas Voit
- Thérapie des maladies du muscle strié, Institut de Myologie, UM76, UPMC Université Paris 6, Paris, France.,INSERM U974, Paris, France.,CNRS UMR 7215, Paris, France
| | - Woodring E Wright
- UT Southwestern Medical Center, Department of Cell Biology, Dallas, TX 75390, USA
| | - Ahmed Aamiri
- Laboratoire LBCM, Departement de Biologie, Faculté des Sciences, Agadir, Maroc
| | - Gillian Butler-Browne
- Thérapie des maladies du muscle strié, Institut de Myologie, UM76, UPMC Université Paris 6, Paris, France.,INSERM U974, Paris, France.,CNRS UMR 7215, Paris, France
| | - Vincent Mouly
- Thérapie des maladies du muscle strié, Institut de Myologie, UM76, UPMC Université Paris 6, Paris, France.,INSERM U974, Paris, France.,CNRS UMR 7215, Paris, France
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Zhang T, Yang H, Wang R, Xu K, Xin Y, Ren G, Zhou G, Zhang C, Wang L, Zhang Z. Oral administration of myostatin-specific whole recombinant yeast Saccharomyces cerevisiae vaccine increases body weight and muscle composition in mice. Vaccine 2011; 29:8412-6. [DOI: 10.1016/j.vaccine.2011.08.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2011] [Revised: 07/31/2011] [Accepted: 08/01/2011] [Indexed: 10/17/2022]
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Shephard F, Adenle AA, Jacobson LA, Szewczyk NJ. Identification and functional clustering of genes regulating muscle protein degradation from amongst the known C. elegans muscle mutants. PLoS One 2011; 6:e24686. [PMID: 21980350 PMCID: PMC3181249 DOI: 10.1371/journal.pone.0024686] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2011] [Accepted: 08/15/2011] [Indexed: 01/08/2023] Open
Abstract
Loss of muscle mass via protein degradation is an important clinical problem but we know little of how muscle protein degradation is regulated genetically. To gain insight our labs developed C. elegans into a model for understanding the regulation of muscle protein degradation. Past studies uncovered novel functional roles for genes affecting muscle and/or involved in signalling in other cells or tissues. Here we examine most of the genes previously identified as the sites of mutations affecting muscle for novel roles in regulating degradation. We evaluate genomic (RNAi knockdown) approaches and combine them with our established genetic (mutant) and pharmacologic (drugs) approaches to examine these 159 genes. We find that RNAi usually recapitulates both organismal and sub-cellular mutant phenotypes but RNAi, unlike mutants, can frequently be used acutely to study gene function solely in differentiated muscle. In the majority of cases where RNAi does not produce organismal level phenotypes, sub-cellular defects can be detected; disrupted proteostasis is most commonly observed. We identify 48 genes in which mutation or RNAi knockdown causes excessive protein degradation; myofibrillar and/or mitochondrial morphologies are also disrupted in 19 of these 48 cases. These 48 genes appear to act via at least three sub-networks to control bulk degradation of protein in muscle cytosol. Attachment to the extracellular matrix regulates degradation via unidentified proteases and affects myofibrillar and mitochondrial morphology. Growth factor imbalance and calcium overload promote lysosome based degradation whereas calcium deficit promotes proteasome based degradation, in both cases myofibrillar and mitochondrial morphologies are largely unaffected. Our results provide a framework for effectively using RNAi to identify and functionally cluster novel regulators of degradation. This clustering allows prioritization of candidate genes/pathways for future mechanistic studies.
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Affiliation(s)
- Freya Shephard
- School of Graduate Entry Medicine and Health, University of Nottingham, Royal Derby Hospital, Derby, United Kingdom
| | - Ademola A. Adenle
- School of Graduate Entry Medicine and Health, University of Nottingham, Royal Derby Hospital, Derby, United Kingdom
| | - Lewis A. Jacobson
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Nathaniel J. Szewczyk
- School of Graduate Entry Medicine and Health, University of Nottingham, Royal Derby Hospital, Derby, United Kingdom
- * E-mail:
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83
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Fallon JR. Calcium channels put synapses in their place. Nat Neurosci 2011; 14:536-8. [PMID: 21522142 DOI: 10.1038/nn.2822] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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