Participación de caveolina-1 en la regulación de c-Src, cascadas MAPKS y localización del VDR por 1,25(OH)2-vitamina D3 en células musculares esqueléticas?.

BUITRAGO C; BOLAND R

Buenos Aires

Congreso; XXVI Reunion Annual Asociación Argentina de Osteología y Metabolismo Mineral (AAOMM); 2009

Previously, we demonstrated that 1,25-dihydroxi-vitamin D3 [1,25(OH)2D3] induces non-transcriptional rapid responses through activation of MAPKs in the skeletal muscle cell line C2C12. However, there is no information on the molecular mechanism underlying the initiation of 1,25(OH)2D3 signaling through these pathways. Lipid raft components have been involved in steroid non-genomic effects. In this work we investigated the role of caveolae and caveolin-1 (cav-1) in phosphorylation of MAPKs and c-Src activation by 1,25(OH)2D3. When proliferating C2C12 cells were pre-treated with methyl-beta-cyclodextrin (MCD), a caveolae disrupting agent, under conditions in which cell morphology is not affected and no signs of apoptosis are observed, 1,25(OH)2D3-dependent activation of ERK 1/2, p38 MAPK and c-Src was suppressed. Similar results were obtained by siRNA technology where silencing of cav-1 expression abolished phosphorylation of MAPKs and c-Src induced by 1,25(OH)2D3. Confocal immunocytochemistry and co-immunoprecipitation assays showed that cav-1 colocalizes with c-Src in the periplasma membrane zone at basal conditions. Hormone treatment redistributed these proteins into cytoplasm and nucleus and disrupted their colocalization. Confocal microscopy also revealed that 1,25(OH)2D3 induces translocation of the VDR to the plasma membrane in C2C12 cells, and this effect is abolished by MCD. Preliminary studies suggested a 1a,25(OH)2D3-dependent VDR-c-Src association. Altogether, these data indicate that intact caveolae participate in an early upstream step in 1,25(OH)2D3 signal transduction via c-Src-MAPKs and that the VDR and cav-1 are involved in the rapid events triggered by the hormone in skeletal muscle cells.