Human chorionic gonadotropin (hCG) regulates the expression of Steroidogenic acute regulatory protein (StAR) via the ERK1/2 pathway

Abstract

It has previously been shown that Human Chorionic Gonadotropin (hCG) can stimulate steroidogenesis in Leydig cells. In the present study, the mechanisms of hCG stimulated steroidogenesis in Leydig cells of immaturated pigs were investigated. It was found that both hCG and 8-Br-cAMP could enhance the expression level of both the Steroidogenic acute regulatory protein (StAR) and mRNA, and increase the activity of extracellular signal-regulated kinase1/2 (ERK1/2) significantly depending on stimulating time. However, the effect of 8-Br-cAMP was more significant than that of hCG. While appending the inhibitor of Protein Kinase A (PKA) to Leydig cells in culture, the expression level of StAR protein, mRNA and the activity of ERK1/2 began to drop significantly, but the level of StAR mRNA could still be detectable. While appending the inhibitor of MAPK (PD98059), the expression level of StAR protein and mRNA declined significantly. These results infer that at the beginning of hCG stimulation, hCG increases the level of StAR protein by cAMP-PKA. With prolonged stimulating time, hCG increases the level of StAR protein through cAMP-PKA-ERK1/2.