A novel follicle-stimulating hormone-induced Gαh/phospholipase C-δ1 signaling pathway mediating rat Sertoli cell Ca²⁺-influx

FSH is known to activate Gs/cAMP signaling pathway in Sertoli cells (SCs) to support spermatogenesis. However, the molecular mechanism of FSHinduced Gs/cAMP-independent Ca²⁺-influx in SCs is not clear. In this study, FSH indeed induced an immediate and dose-dependent intracellular Ca ²⁺-elevation in rat SCs. In the presence of EDTA (2.5 mM) or in the absence of extracellular Ca²⁺, the FSH-induced intracellular Ca ²⁺-elevation was abolished. The confocal microscopic observation of Ca²⁺ image revealed that the SC cellular Ca²⁺ level was gradually increased after 50 sec of FSH treatment. Dantrolene, a blocker of intracellular Ca²⁺ release, did not affect this FSH-induced intracellular Ca²⁺ elevation. The pretreatment of rat SCs with phosphatidylinositol-phospholipase C (PLC)-specific inhibitor, U73122 (3 and 10 μM), inhibited the FSH-induced Ca²⁺-influx in a dose-dependent manner, but treatment with Gs-specific inhibitor, NF449 (0.1 and 0.3 μM), did not. On the other hand, the activation of Gαh was immediately induced by FSH in the rat SCs within 5 sec of treatment. The translocation of PLC-δ1 from cytosol to cell membrane and the formation of Gαh/PLC-δ1 complexes occurred within 5 and 10 sec, respectively, of FSH exposure. The intracellular inositol 1,4,5-triphosphate (IP₃) production was also detected after 30 sec of FSH treatment. The synthetic peptide of PLC-δ1 (TIPWNSLKQGYRHVHLL), not Gs inhibitor, predominantly inhibited the FSH-induced PLC-δ1 translocation, formation of Gαh /PLC-δ1 complex, intracellular IP₃ production, and Ca²⁺ influx. In contrast, the peptide did not interfere with FSH-induced intracellular cAMP accumulation. In conclusion, the FSH-induced immediate Ca²⁺ influx is unambiguously mediated by an alternative Gαh /PLC-δ1/IP₃ pathway that is distinct from the Gs/cAMP pathway in rat SCs.