1,25(OH)2-VITAMIN D3 -DEPENDENT ACTIVATION OF AKT IN SKELETAL MUSCLE CELLS

ARANGO NADIA; BOLAND RICARDO; BUITRAGO CLAUDIA GRACIELA

Congreso; XLVI Reunión Anual de la Sociedad Argentina de Investigación Bioquímica y Biología Molecular (SAIB); 2010

We previously reported that 1,25-dihydroxi-vitamin D3 [1,25(OH)2D3] induces non-transcriptional rapid responses through activation of Src and MAPKs in the skeletal muscle cell line C2C12. However, there is no information on the regulation of the PI3K/Akt signaling pathway by the hormone in these cells. We report here that 1,25(OH)2D3 promotes Akt phosphorylation in Ser473 (activation) in a time-dependent manner (5-60 min). When proliferating C2C12 cells were pre-treated with methyl-beta-cyclodextrin or caveolin-1  expression was silenced with siRNA, 1,25(OH)2D3-induced activation of Akt was suppressed, indicating that the hormone exerts its effects in cell membrane calveolae. PI3K, ERK1/2, p38 MAPK and PKC were shown to participate in 1,25(OH)2D3–dependent activation of Akt. We also demonstrated c-Src involvement in Akt phosphorylation by 1,25(OH)2D3 using the inhibitor PP2 and antisense oligodeoxynucleotides. During the early stages of differentiation of C2C12 cells we observed that the hormone increases phosphorylation of Akt without affecting its expression. Src and PI3K, were involved in Akt activation and heavy chain myosin and myogenin expression induced by 1,25(OH)2D3. These results suggest that Src and Akt are required during myogenesis triggered by the hormone.