title: Myostatin promotes the wasting of human myoblast cultures through promoting ubiquitin-proteasome pathway-mediated loss of sarcomeric proteins.
abstract: Myostatin is a negative regulator of skeletal muscle growth and in fact acts as a potent inducer of "cachectic-like" muscle wasting in mice. The mechanism of action of myostatin in promoting muscle wasting has been predominantly studied in murine models. Despite numerous reports linking elevated levels of myostatin to human skeletal muscle wasting conditions, little is currently known about the signaling mechanism(s) through which myostatin promotes human skeletal muscle wasting. Therefore, in this present study we describe in further detail the mechanisms behind myostatin regulation of human skeletal muscle wasting using an in vitro human primary myotube atrophy model. Treatment of human myotube populations with myostatin promoted dramatic myotubular atrophy. Mechanistically, myostatin-induced myotube atrophy resulted in reduced p-AKT concomitant with the accumulation of active dephosphorylated Forkhead Box-O (FOXO1) and FOXO3. We further show that addition of myostatin results in enhanced activation of atrogin-1 and muscle-specific RING finger protein 1 (MURF1) and reduced expression of both myosin light chain (MYL) and myosin heavy chain (MYH). In addition, we found that myostatin-induced loss of MYL and MYH proteins is dependent on the activity of the proteasome and mediated via SMAD3-dependent regulation of FOXO1 and atrogin-1. Therefore, these data suggest that the mechanism through which myostatin promotes muscle wasting is very well conserved between species, and that myostatin-induced human myotube atrophy is mediated through inhibition of insulin-like growth factor (IGF)/phosphoinositide 3-kinase (PI3-K)/AKT signaling and enhanced activation of the ubiquitin-proteasome pathway and elevated protein degradation.
authors: Growth, Development and Metabolism Program, Singapore Institute for Clinical Sciences, Brenner Centre for Molecular Medicine, 30 Medical Drive, Singapore.
authors: Sudarsanareddy
authors: S
authors: Lokireddy
authors: Vincent
authors: V
authors: Mouly
authors: Gillian
authors: G
authors: Butler-Browne
authors: Peter D
authors: PD
authors: Gluckman
authors: Mridula
authors: M
authors: Sharma
authors: Ravi
authors: R
authors: Kambadur
authors: Craig
authors: C
authors: McFarlane
mesh_terms: D015153:Blotting, Western; D002478:Cells, Cultured; D006801:Humans; D047468:Immunoprecipitation; D009124:Muscle Proteins / Q000378:metabolism*; D009133:Muscular Atrophy / Q000378:metabolism / Q000473:pathology; D032446:Myoblasts / Q000378:metabolism* / Q000473:pathology; D055435:Myostatin / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D011863:Radioimmunoassay; D012518:Sarcomeres / Q000378:metabolism / Q000473:pathology; D015398:Signal Transduction / Q000502:physiology*; D025801:Ubiquitin / Q000378:metabolism; D019282:Wasting Syndrome / Q000378:metabolism* / Q000473:pathology
chemical_list: D009124:Muscle Proteins; D055435:Myostatin; D034741:RNA, Small Interfering; D025801:Ubiquitin; D046988:Proteasome Endopeptidase Complex