Extracellular Signal-Regulated Kinase (ERK) Activation and Mitogen-Activated Protein Kinase Phosphatase 1 Induction by Pulsatile Gonadotropin-Releasing Hormone in Pituitary Gonadotrophs

Figure 1

Schematic summary of intracellular signaling by GnRH. The initial phase of GnRH action involves Gq-protein-mediated stimulation of phospholipase Cβ (PLCβ), leading to the formation of 1,4,5-triphosphate (IP3) and diacylglycerol (DG). IP3 induces the release of intracellular calcium from endoplasmic reticulum, and DG activates protein kinase C (PKC), which ultimately activates extracellular signal-regulated kinase (ERK). P38 MAPK, c-Jun N-terminal kinase (JNK), and calcium-calmodulin kinase II (CaMK II) are also activated by GnRH. Not predominant, but GnRH also couples to Gs protein which are linked with adenylate cyclase and induces rapid cAMP production, which ultimately activates protein kinase A (PKA). MAP kinase phosphatase 1/2 (MKP1/2) inactivates ERK by dephosphorylation.