Activation of phospholipase C-β1 via Gαq/11 during calcium mobilization by calcitonin gene-related peptide

Interaction of calcitonin gene-related peptide (CGRP) with its receptors leads to stimulation of adenylyl cyclase and/or phospholipase C (PLC), While regulation of adenylyl cyclase is thought to involve the G-protein G(s), it is not known whether activation of PLC results from coupling the receptor to G(q) family proteins or whether beta gamma subunits released from receptor-activated G(s) activate PLC. We used human bone cells OHS-4 bearing CORP receptors in which CORP activates only the PLC signaling pathway to determine how CORP acts. CORP increased the concentration of intracellular calcium ([Ca2+](i)) within 5 s via a Ca2+ influx through voltage-gated calcium channels and by mobilizing calcium from the endoplasmic reticulum. The activation of effecters, like PLC coupled to G-proteins, is the early event in the pathway leading to inositol 1,4,5-trisphosphate formation, which is responsible for Ca2+ mobilization. Western blotting demonstrated a range of PLC-beta isoforms (beta 1, beta 3, beta 4, but not beta 2) and G-proteins (G alpha(q/11) and G alpha(s)). Only phospholipase C-beta 1 is involved in the mobilization of Ca2+ from the endoplasmic reticulum of Fura-2-loaded confluent OHS-4 cells and the formation of inositol 1,4,5-trisphosphate by CORP; PLC-gamma have no effect. Activation of PLC-beta 1 by CORP involves the G alpha(q/11) subunit, which is insensitive to pertussis toxin, but not G beta gamma subunits. We therefore believe that CORP causes the activation of two separate G-proteins.