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IGF‐1 induces IP 3 ‐dependent calcium signal involved in the regulation of myostatin gene expression mediated by NFAT during myoblast differentiation
Author(s) -
Valdés Juan A.,
Flores Sylvia,
Fuentes Eduardo N.,
OsorioFuentealba Cesar,
Jaimovich Enrique,
Molina Alfredo
Publication year - 2013
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.24298
Subject(s) - nfat , microbiology and biotechnology , myogenesis , biology , ryanodine receptor , myocyte , transcription factor , signal transduction , intracellular , biochemistry , gene
Skeletal muscle differentiation is a complex and highly regulated process characterized by cell cycle arrest, which is associated with morphological changes including myoblast alignment, elongation, and fusion into multinucleated myotubes. This is a balanced process dynamically coordinated by positive and negative signals such as the insulin‐like growth factor I (IGF‐1) and myostatin (MSTN), respectively. In this study, we report that the stimulation of skeletal myoblasts during differentiation with IGF‐1 induces a rapid and transient calcium increase from intracellular stores, which are principally mediated through the phospholipase C gamma (PLC γ)/inositol 1,4,5‐triphosphate (IP 3 )‐dependent signaling pathways. This response was completely blocked when myoblasts were incubated with LY294002 or transfected with the dominant‐negative p110 gamma, suggesting a fundamental role of phosphatidylinositol 3‐kinase (PI3K) in PLCγ activation. Additionally, we show that calcium released via IP 3 and induced by IGF‐1 stimulates NFAT‐dependent gene transcription and nuclear translocation of the GFP‐labeled NFATc3 isoform. This activation was independent of extracellular calcium influx and calcium release mediated by ryanodine receptor (RyR). Finally, we examined mstn mRNA levels and mstn promoter activity in myoblasts stimulated with IGF‐1. We found a significant increase in mRNA contents and in reporter activity, which was inhibited by cyclosporin A, 11R‐VIVIT, and by inhibitors of the PI3Kγ, PLCγ, and IP 3 receptor. Our results strongly suggest that IGF‐1 regulates myostatin transcription through the activation of the NFAT transcription factor in an IP 3 /calcium‐dependent manner. This is the first study to demonstrate a role of calcium‐dependent signaling pathways in the mRNA expression of myostatin. J. Cell. Physiol. 228: 1452–1463, 2013. © 2012 Wiley Periodicals, Inc.