1,25(OH)2-vitamin D3 actions on cellular cycle depend on VDR and p38 MAPK in skeletal muscle cells.

IRAZOQUI AP; BOLAND R; BUITRAGO C

JOURNAL OF MOLECULAR ENDOCRINOLOGY

BIOSCIENTIFICA LTD

Año: 2014 vol. 53 p. 1 - 14

0952-5041

We previously reported that 1,25(OH)2-vitamin D3 (1,25D) activates p38 MAPK (p38) in a VDR-dependent manner in proliferative C2C12 myoblast cells. It was also demonstrated that 1,25D promotes muscle cell proliferation and differentiation. However, we did not study in depth these hormone actions. In the present work it was investigated whether the VDR and p38 participate in the signalling mechanism triggered by 1,25D. In C2C12 cells, the VDR was knocked down by a shRNA and p38 was specifically inhibited using SB-203580. Cell cycle studies showed that hormone stimulation prompts a peak of S-phase followed by an arrest in the G0/G1-phase, events which were dependent on VDR and p38. Moreover, 1,25D increases the expression of cyclin D3, and CDK inhibitors, p21Waf1/Cip1 and p27Kip1, while cyclin D1 protein levels did not change during G0/G1 arrest. In all these events p38 and VDR were required. At the same time, a 1,25D?dependent acute increase in myogenin expression was observed, indicating that the G0/G1 arrest of cells is a pro-differentiative event. Immunocytochemical assays reveal co-localization of VDR and cyclin D3 promoted by 1,25D in a p38 dependent manner. When cyclin D3 expression was silenced, VDR and myogenin levels were down-regulated, showing that cyclin D3 was required for 1,25D-induced VDR expression and the concomitant entrance into the differentiation process. In conclusion, the VDR and p38 are involved in control of cellular cycle by 1,25D in skeletal muscle cells, providing key information on the mechanism underlying hormone regulation of myogenesis.