Vimentin phosphorylation as a target of cell signaling mechanisms induced by 1α,25-dihydroxyvitamin D 3 in immature rat testes

Abstract

The effects of 1α,25-dihydroxyvitamin D 3 [1,25(OH) 2D 3] 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) 2D 3 on vimentin phosphorylation in 15-day-old rat testes. Results showed that 1,25(OH) 2D 3 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 Ca 2+ mediating the effects of 1,25(OH) 2D 3 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) 2D 3. However, the phosphoERK1/2 levels significantly increased at 1 and 5 min 1,25(OH) 2D 3 treatment. Furthermore, phosphoJNK1 levels were decreased at 10 and 15 min 1,25(OH) 2D 3 exposure, while phosphoJNK 2 levels were diminished at 5, 10 and 15 min treatment with the hormone. These findings demonstrate that 1,25(OH) 2D 3 may modulate vimentin phosphorylation through nongenomic Ca 2+-dependent mechanisms in testis cells.