1alpha,25(OH)2-vitamin D3-modulation of cyclin dependent kinases 4 and 6 in skeletal muscle cells

A. PAULA IRAZOQUI; HEIM NADIA; BOLAND R; BUITRAGO C

Rosario

Congreso; Reunión Anual de la Sociedad Argentina de Investigaciones Bioquímicas y de Biología Molecular (SAIB); 2014

We reported the VDR and p38 MAPK participation in cell proliferation and differentiation triggered by 1,25(OH)2-vitamin D3 [1,25D] in C2C12 muscle cells. Moreover, 1,25D induced the expression of cyclin D3 and cyclin dependent kinases (CDKs) inhibitors in a VDR- and p38 MAPK-dependent manner. We here show that CDKs 4 and 6 also play a role in 1,25D stimulation of myogenesis. C2C12 myoblasts were infected with pLKO.1 plasmid encoding a shRNA against mouse VDR, which was knocked down 80%. P38 MAPK and ERK1/2 were inhibited using SB203580 and UO126 compounds, respectively. Investigation of changes in cellular cycle proteins by immunoblotting and immunocytochemistry showed that the VDR is involved in the 1,25D ?induced increase of CDK4 and CDK6 levels during the S-phase peak. Up-regulation of CDKs 4 and 6 by 1,25D (12 h) was abolished in C2C12 cells pretreated with the ERK1/2 inhibitor UO126. However, CDKs 4 and 6 expression induced by the hormone was not dependent on p38 MAPK activation. Confocal images showed that there is no co-localization between VDR and CDKs. Silencing of cyclin D3 only diminished the levels of CDK 4. The results indicate that the VDR and ERK1/2, but not p38 MAPK, are involved in the control of the muscle cellular cycle by 1,25D through CDKs 4 and 6 as part of the mechanism of hormone modulation of myogenesis.