Beta (2) -adrenergic receptor agonists increase intracellular free Ca (2+) concentration cycling in ventricular cardiomyocytes through p38 and p42/44 MAPK-mediated cytosolic phospholipase A (2) activation

Magne, S.; Couchie, D.; Pecker, F.; Pavoine, C.

Journal of Biological Chemistry 276(43): 39539-39548


ISSN/ISBN: 0021-9258
PMID: 11507087
DOI: 10.1074/jbc.m100954200
Accession: 011663676

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We have recently reported that arachidonic acid mediates beta(2)-adrenergic receptor (AR) stimulation of [Ca(2+)](i) cycling and cell contraction in embryonic chick ventricular cardiomyocytes (Pavoine, C., Magne, S., Sauvadet, A., and Pecker, F. (1999) J. Biol. Chem. 274, 628-637). In the present work, we demonstrate that beta(2)-AR agonists trigger arachidonic acid release via translocation and activation of cytosolic phospholipase A(2) (cPLA(2)) and increase caffeine-releasable Ca(2+) pools from Fura-2-loaded cells. We also show that beta(2)-AR agonists trigger a rapid and dose-dependent phosphorylation of both p38 and p42/44 MAPKs. Translocation and activation of cPLA(2), as well as Ca(2+) accumulation in sarcoplasmic reticulum stores sensitive to caffeine and amplification of [Ca(2+)](i) cycling in response to beta(2)-AR agonists, were blocked by inhibitors of the p38 or p42/44 MAPK pathway (SB203580 and PD98059, respectively), suggesting a role of both MAPK subtypes in beta(2)-AR stimulation. In contrast, beta(1)-AR stimulation of [Ca(2+)](i) cycling was rather limited by the MAPKs, clearly proving the divergence between beta(2)-AR and beta(1)-AR signaling systems. This study presents the first evidence for the coupling of beta(2)-AR to cardiac cPLA(2) and points out the key role of the MAPK pathway in the intracellular signaling elicited by positive inotropic beta(2)-AR agonists in heart.