Cordyceps sinensis mycelium activates PKA and PKC signal pathways to stimulate steroidogenesis in MA-10 mouse Leydig tumor cells

Cordyceps sinensis (CS) mycelium stimulates steroidogenesis in MA-10 mouse Leydig tumor cells, but the mechanisms remain unclear. In this study, MA-10 cells were treated with different reagents in the presence or absence of CS (10 mg/ml) for 3 h to determine the mechanisms. Results illustrated that CS activated the Gsα protein subunit, but not Giα, to induce cell steroidogenesis. Moreover, PKA inhibitors inhibited 37% of CS-stimulated steroidogenesis, which demonstrated that CS might enhance the cAMP-PKA pathway to affect MA-10 cell steroidogenesis. Because of incomplete inhibition by PKA inhibitors, we also examined the PKC pathway. PKC inhibitor, phospholipase C inhibitor, and calmodulin antagonist blocked 35-52% of CS-stimulated steroidogenesis in MA-10 cells, strongly suggesting that CS had activated the PKC pathway. Co-treatment with PKA and PKC inhibitors abolished 61% of CS-stimulated steroid production, indicating that CS simultaneously activated PKA and PKC pathways. Moreover, CS induced the expression of steroidogenic acute regulatory (StAR) protein in dose- and time-dependent relationships, and PKA inhibitor, PKC inhibitor, or co-treatment with both inhibitors suppressed it. These data support that CS activates both PKA and PKC signal transduction pathways to stimulate MA-10 cell steroidogenesis.