The Ca2+-sensing Receptor Activates Cytosolic Phospholipase A2 via a Gqα-dependent ERK-independent Pathway

Mary E. Handlogten, Chunfa Huang, Naoki Shiraishi, Hisataka Awata, R. Tyler Miller

Research output: Contribution to journalArticle

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Abstract

The Ca2+-sensing receptor (CaR) stimulates a number of phospholipase activities, but the specific phospholipases and the mechanisms by which the CaR activates them are not defined. We investigated regulation of phospholipase A2 (PLA2) by the Ca2+-sensing receptor (CaR) in human embryonic kidney 293 cells that express either the wild-type receptor or a nonfunctional mutant (R796W) CaR. The PLA2 activity was attributable to cytosolic PLA2 (cPLA2) based on its inhibition by arachidonyl trifluoromethyl ketone, lack of inhibition by bromoenol lactone, and enhancement of the CaR-stimulated phospholipase activity by coexpression of a cDNA encoding the 85-kDa human cPLA2. No CaR-stimulated cPLA2 activity was found in the cells that expressed the mutant CaR. Pertussis toxin treatment had a minimal effect on CaR-stimulated arachidonic acid release and the CaR-stimulated rise in intracellular Ca2+ (Ca2+i), whereas inhibition of phospholipase C (PLC) with U73122 completely inhibited CaR-stimulated PLC and cPLA2 activities. CaR-stimulated PLC activity was inhibited by expression of RGS4, an RGS (Regulator of G protein Signaling) protein that inhibits Gαq activity. CaR-stimulated cPLA2 activity was inhibited 80% by chelation of extracellular Ca2+ and depletion of intracellular Ca2+ with EGTA and inhibited 90% by treatment with W7, a calmodulin inhibitor, or with KN-93, an inhibitor of Ca2+, calmodulin-dependent protein kinases. Chemical inhibitors of the ERK activator, MEK, and a dominant negative MEK, MEKK97R, had no effect on CaR-stimulated cPLA2 activity but inhibited CaR-stimulated ERK activity. These results demonstrate that the CaR activates cPLA2 via a Gαq, PLC, Ca2+-CaM, and calmodulin-dependent protein kinase-dependent pathway that is independent the ERK pathway.

Original languageEnglish (US)
Pages (from-to)13941-13948
Number of pages8
JournalJournal of Biological Chemistry
Volume276
Issue number17
DOIs
StatePublished - Apr 27 2001

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ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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