Activation of phospholipase C-beta1 via Galphaq/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 Gs, it is not known whether activation of PLC results from coupling the receptor to Gq family proteins or whether beta gamma subunits released from receptor-activated Gs activate PLC. We used human bone cells OHS-4 bearing CGRP receptors in which CGRP activates only the PLC signaling pathway to determine how CGRP acts. CGRP 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 effectors, 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 (beta1, beta3, beta4, but not beta2) and G-proteins (Galphaq/11 and Galphas). Only phospholipase C-beta1 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 CGRP; PLC-gamma have no effect. Activation of PLC-beta1 by CGRP involves the Galphaq/11 subunit, which is insensitive to pertussis toxin, but not Gbeta gamma subunits. We therefore believe that CGRP causes the activation of two separate G-proteins.
Institut National de la Santé et de la Recherche Médicale, U 349, Hôpital Lariboisière, Paris, France.
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H
Drissi
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Lasmoles
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Le Mellay
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PJ
Marie
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Lieberherr
D037361:Adenylate Cyclase Toxin; D000906:Antibodies / Q000494:pharmacology; D001842:Bone and Bones / Q000502:physiology; D015740:Calcitonin Gene-Related Peptide / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D004789:Enzyme Activation / Q000502:physiology; D016257:Fura-2 / Q000031:analogs & derivatives / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000494:pharmacology; D006801:Humans; D007527:Isoenzymes / Q000737:chemistry / Q000378:metabolism*; D037342:Pertussis Toxin; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism; D054799:Phospholipase C beta; D015398:Signal Transduction / Q000502:physiology; D010738:Type C Phospholipases / Q000378:metabolism*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D037361:Adenylate Cyclase Toxin; D000906:Antibodies; D007527:Isoenzymes; D019269:Phosphatidylinositol 4,5-Diphosphate; D010566:Virulence Factors, Bordetella; C049925:fura-2-am; D006160:Guanosine Triphosphate; D037342:Pertussis Toxin; D010738:Type C Phospholipases; C518033:PLCB1 protein, human; C518036:PLCB2 protein, human; C518039:PLCB3 protein, human; C518042:PLCB4 protein, human; D054799:Phospholipase C beta; D019204:GTP-Binding Proteins; D015740:Calcitonin Gene-Related Peptide; D002118:Calcium; D016257:Fura-2