Vasopressin-dependent Myogenic Cell Differentiation Is Mediated by Both Ca²⁺/Calmodulin-dependent Kinase and Calcineurin Pathways

Abstract

Arg8-vasopressin (AVP) promotes the differentiation of myogenic cell lines and mouse primary satellite cells by mechanisms involving the transcriptional activation of myogenic bHLH regulatory factors and myocyte enhancer factor 2 (MEF2). We here report that AVP treatment of L6 cells results in the activation of calcineurin-dependent differentiation, increased expression of MEF2 and GATA2, and nuclear translocation of the calcineurin target NFATc1. Interaction of these three factors occurs at MEF2 sites of muscle specific genes. The different kinetics of AVP-dependent expression of early (myogenin) and late (MCK) muscle-specific genes correlate with different acetylation levels of histones at their MEF2 sites. The cooperative role of calcineurin and Ca2+/calmodulin-dependent kinase (CaMK) in AVP-dependent differentiation is demonstrated by the effect of inhibitors of the two pathways. We show here, for the first time, that AVP, a "novel" myogenesis promoting factor, activates both the calcineurin and the CaMK pathways, whose combined activation leads to the formation of multifactor complexes and is required for the full expression of the differentiated phenotype. Although MEF2-NFATc1 complexes appear to regulate the expression of an early muscle-specific gene product (myogenin), the activation of late muscle-specific gene expression (MCK) involves the formation of complexes including GATA2.

The Molecular Bases of Training Adaptation

“…Calcineurin appears to act as a co-regulator of muscle hypertrophy with insulin-like growth factor and may also contribute to myogenic proliferation and differentiation of satellite cells during skeletal muscle regeneration (Dunn et al 1999;Musaro et al 1999;Dunn et al 2000;Sakuma et al 2003;Scicchitano et al 2005). The use of calcium / calmodulin inhibitors has been shown to suppress growth of overloaded muscle fibres while calcineurin over expression reduces disuse atrophy (Dunn et al 1999;Dunn et al 2000).…”

Novel evidence that testosterone promotes cell proliferation and differentiation via G protein‐coupled receptors in the rat L6 skeletal muscle myoblast cell line

“…The gene expressions of myogenin, myosin heavy chain (MHC) and PCNA were assayed by semi quantitative RT-PCR. The primers specific for mouse myogenin and MHC (Table 1) were prepared as described previously (Scicchitano et al, 2005). The primers for PCNA and AR were designed by Primer Express 3.0 software and confirmed to amplify a single product of the expected size via dissociation analysis and gel electrophoresis.…”

CaMK activation during exercise is required for histone hyperacetylation and MEF2A binding at the MEF2 site on theGlut4gene

“…Scicchitano et al (32) have recently shown a strong association between acetylation of histone H4 at MEF2 binding sites on genes and increased transcriptional activity of these genes. When L6 myoblasts were treated with arginine vasopressin to induce differenciation, there was a progressive increase in acetylated histone H4 at MEF2 binding sites on myogenin and muscle creatine kinase (MCK) genes that correlated well with the kinetics of the induction of myogenin and MCK mRNA transcripts.…”