Akt2 is implicated in skeletal muscle differentiation and specifically binds Prohibitin2/REA

Abstract

Akt1 and Akt2 are the major isoforms of Akt expressed in muscle cells and muscle tissue. We have performed siRNA silencing of Akt1 and Akt2 in C2 myoblasts to characterize their specific implication in muscle differentiation. Whereas silencing Akt2, and not Akt1, inhibited cell cycle exit and myoblast differentiation, Akt2 overexpression led to an increased proportion of differentiated myoblasts. In addition, we demonstrate that Akt2 is required for myogenic conversion induced by MyoD overexpression in fibroblasts. We show Akt2, but not Akt1, binds Prohibitin2/Repressor of Estrogen Activator, PHB2/REA, a protein recently implicated in transcriptionnal repression of myogenesis. Co-immunoprecipitation experiments on endogenous proteins showed the Akt2-REA complex does not contain Prohibitin1. We have analyzed expression and localization of PHB2/REA during proliferation and differentiation of mouse and human myoblasts. PHB2/REA shows punctated nuclear staining which partially co-localizes with Akt2 in differentiated myotubes and PHB2 levels decrease at the onset of myogenic differentiation concomitant with an increase in Akt2. There appears to be an inverse correlation between Akt2 and PHB2 protein levels where cells silenced for Akt2 expression show increased level of PHB2/REA and overexpression of Akt2 resulted in decreased Prohibitin2/REA. Taken together, these results, along with our previous observations, clearly show that Akt2 and not Akt1 plays a major and early role in cell cycle exit and myogenic differentiation and this function involves its specific interaction with PHB2/REA.

Protein Phosphatase 2A Isoforms Utilizing Aβ Scaffolds Regulate Differentiation through Control of Akt Protein

“…Akt Activity Controls Differentiation of C2C12 and 3T3-L1 Cells-Akt activity has been implicated in differentiation of preadipocytes and myoblasts (25)(26)(27)(28)(29)(30)(31). As expected, Akt was activated during differentiation as seen by increased phosphorylation at Ser-473 (Fig.…”

“…Both Akt1 and Akt2 play a role in myoblast differentiation (28,30,31), and knockdown of either blocks myoblast differentiation (30,31). Conversely, Akt2 expression is increased during the differentiation process (28).…”

Synergistic effects of TGFβ2, WNT9a, and FGFR4 signals attenuate satellite cell differentiation during skeletal muscle development

“…MYLPF is a marker of fast skeletal muscle, and RYR1 functions as a calcium release channel in muscle contraction (Eltit et al., 2010; Wang et al., 2007). AKT2 could enhance myogenic differentiation, and MKNK2 could promote cell proliferation (Heron‐Milhavet, Mamaeva, Rochat, Lamb & Fernandez, 2008; Maimon et al., 2014; Teo et al., 2015). All these effector genes were downregulated during development, implying that the genes and signals identified through WGCNA were important for the differentiation of satellite cells.…”

Prohibitin-2 Binding Modulates Insulin-like Growth Factor-binding Protein-6 (IGFBP-6)-induced Rhabdomyosarcoma Cell Migration

“…In the nucleus, PHB2 physically interacts with the estrogen receptor (43) and brefeldin A-inhibited guanine nucleotide-exchange protein 3 (BIG3) (44), resulting in suppression of gene transcription and contributing to tumor growth inhibition (10). In the cytosol, PHB2 but not PHB1 binds Akt2 and reciprocally regulates Akt2 levels and muscle differentiation (12,45). PHB2 also interacts with ␣-actinin and annexin A2 (46).…”

“…In the nucleus, PHBs serve as transcriptional regulators, thereby repressing cell proliferation (10). Cytoplasmic PHB1 plays an important role in Ras-mediated epithelial cell migration (11), whereas cytoplasmic PHB2 has been linked to phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) signaling, thereby modulating skeletal muscle differentiation (12). Cell surface PHB1⅐PHB2 complexes interact with the C-terminal cytoplasmic domain of the HIV-1 glycoprotein (13) and the Vi polysaccharide of Salmonella typhi in intestinal epithelial cells (14), with the latter interaction resulting in suppression of early inflammatory responses.…”