Inhibition of cAMP-Dependent PKA Activates beta2-Adrenergic Receptor Stimulation of Cytosolic Phospholipase A2 via Raf-1/MEK/ERK and IP3-Dependent Ca2+ Signaling in Atrial Myocytes Journal Article

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Authors: Pabbidi, M. R.; Ji, X.; Maxwell, J. T.; Mignery, G. A.; Samarel, A. M.; Lipsius, S. L.
Article Title: Inhibition of cAMP-Dependent PKA Activates beta2-Adrenergic Receptor Stimulation of Cytosolic Phospholipase A2 via Raf-1/MEK/ERK and IP3-Dependent Ca2+ Signaling in Atrial Myocytes
Abstract: We previously reported in atrial myocytes that inhibition of cAMP-dependent protein kinase (PKA) by laminin (LMN)-integrin signaling activates beta2-adrenergic receptor (beta2-AR) stimulation of cytosolic phospholipase A2 (cPLA2). The present study sought to determine the signaling mechanisms by which inhibition of PKA activates beta2-AR stimulation of cPLA2. We therefore determined the effects of zinterol (0.1 muM; zint-beta2-AR) to stimulate ICa,L in atrial myocytes in the absence (+PKA) and presence (-PKA) of the PKA inhibitor (1 muM) KT5720 and compared these results with atrial myocytes attached to laminin (+LMN). Inhibition of Raf-1 (10 muM GW5074), phospholipase C (PLC; 0.5 muM edelfosine), PKC (4 muM chelerythrine) or IP3 receptor (IP3R) signaling (2 muM 2-APB) significantly inhibited zint-beta2-AR stimulation of ICa,L in-PKA but not +PKA myocytes. Western blots showed that zint-beta2-AR stimulation increased ERK1/2 phosphorylation in-PKA compared to +PKA myocytes. Adenoviral (Adv) expression of dominant negative (dn) -PKCalpha, dn-Raf-1 or an IP3 affinity trap, each inhibited zint-beta2-AR stimulation of ICa,L in + LMN myocytes compared to control +LMN myocytes infected with Adv-betagal. In +LMN myocytes, zint-beta2-AR stimulation of ICa,L was enhanced by adenoviral overexpression of wild-type cPLA2 and inhibited by double dn-cPLA2S505A/S515A mutant compared to control +LMN myocytes infected with Adv-betagal. In-PKA myocytes depletion of intracellular Ca2+ stores by 5 muM thapsigargin failed to inhibit zint-beta2-AR stimulation of ICa,L via cPLA2. However, disruption of caveolae formation by 10 mM methyl-beta-cyclodextrin inhibited zint-beta2-AR stimulation of ICa,L in-PKA myocytes significantly more than in +PKA myocytes. We conclude that inhibition of PKA removes inhibition of Raf-1 and thereby allows beta2-AR stimulation to act via PKCalpha/Raf-1/MEK/ERK1/2 and IP3-mediated Ca2+ signaling to stimulate cPLA2 signaling within caveolae. These findings may be relevant to the remodeling of beta-AR signaling in failing and/or aging heart, both of which exhibit decreases in adenylate cyclase activity.
Journal Title: PloS one
Volume: 11
Issue: 12
ISSN: 1932-6203; 1932-6203
Publisher: Unknown  
Journal Place: United States
Date Published: 2016
Start Page: e0168505
Language: eng
DOI/URL:

10.1371/journal.pone.0168505
Notes: LR: 20170224; JID: 101285081; 2016/07/19 [received]; 2016/12/01 [accepted]; epublish