Vimentin phosphorylation as a target of cell signaling mechanisms induced by 1α,25-dihydroxyvitamin D3 in immature rat testes

The effects of 1α,25-dihydroxyvitamin D3 [1,25(OH)2D3] are mainly mediated by nuclear receptors modulating gene expression. However, there are increasing evidences of nongenomic mechanisms of this hormone associated with kinase- and calcium-activated signaling pathways. In this context, the aim of the present work was to investigate the signaling pathways involved in the mechanism of action of 1,25(OH)2D3 on vimentin phosphorylation in 15-day-old rat testes. Results showed that 1,25(OH)2D3 at concentrations ranging from 1 nM to 1 μM increased vimentin phosphorylation independent of protein synthesis. We also demonstrated that the mechanisms underlying the hormone action involve protein kinase C activation in a phospholipase C-independent manner. Moreover, we showed that the participation of protein kinase A, extracellular regulated protein kinase (ERK), and intra- and extracellular Ca2+ mediating the effects of 1,25(OH)2D3 on the cytoskeleton. In addition, we investigated the effect of different times of exposure to the hormone on total and phosphoERK1/2 or c-Jun N-terminal kinases 1/2 (JNK1/2) in immature rat testis. Results showed that the total levels of ERK1/2 and JNK1/2 were unaltered from 1 to 15 min exposure to 1,25(OH)2D3. However, the phosphoERK1/2 levels significantly increased at 1 and 5 min 1,25(OH)2D3 treatment. Furthermore, phosphoJNK1 levels were decreased at 10 and 15 min 1,25(OH)2D3 exposure, while phosphoJNK 2 levels were diminished at 5, 10 and 15 min treatment with the hormone. These findings demonstrate that 1,25(OH)2D3 may modulate vimentin phosphorylation through nongenomic Ca2+-dependent mechanisms in testis cells.