Galphaq expression activates EGFR and induces Akt mediated cardiomyocyte survival: dissociation from Galphaq mediated hypertrophy.
Our laboratory has previously shown that adenoviral-mediated overexpression of Galphaq in neonatal rat ventricular cardiomyocytes increases the phosphorylation of Akt, a well-established anti-apoptotic effector. As demonstrated here, Galphaq expression protects cardiomyocytes against apoptosis induced by treatment with 2-deoxyglucose (2DOG) and this protection is lost when Akt activation is prevented by treatment with LY294002 (an inhibitor of PI3K). Galphaq-induced Akt phosphorylation is not caused by increased Gbetagamma signaling and does not appear to involve PKC activation. Rather studies using the EGF receptor inhibitor AG1478 and the Src inhibitor PP2 implicate these tyrosine kinases in the pathway inducing Akt phosphorylation. EGFR phosphorylation is increased in cells expressing Galphaq and this effect is inhibited by PP2, placing Src upstream of EGFR phosphorylation. EGFR activation appears to be required for Galphaq-mediated protection since inhibition of Src or EGFR rendered cells susceptible to 2DOG-induced apoptosis. In contrast to the requirement for EGFR mediated Akt activation in cardioprotection, neither EGFR nor Akt activation are necessary for the hypertrophic increases in cell size or ANF content elicited by Galphaq overexpression. These data demonstrate that increased Galphaq activity can provide anti-apoptotic signals by eliciting EGFR phosphorylation and subsequent Akt activation, independent of the well-known ability of Galphaq signaling to elicit hypertrophy.
Howes
Amy L
AL
Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093-0636, USA.
Miyamoto
Shigeki
S
Adams
John W
JW
Woodcock
Elizabeth A
EA
Brown
Joan Heller
JH
D000818:Animals; D017209:Apoptosis; D002470:Cell Survival; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066246:ErbB Receptors / Q000378:metabolism*; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000096:biosynthesis* / Q000378:metabolism*; D006352:Heart Ventricles / Q000473:pathology; D006984:Hypertrophy; D009206:Myocardium / Q000473:pathology; D032383:Myocytes, Cardiac / Q000378:metabolism*; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D011799:Quinazolines; D051381:Rats; D015533:Transcriptional Activation; D020032:Tyrphostins / Q000494:pharmacology
D004791:Enzyme Inhibitors; D011799:Quinazolines; D020032:Tyrphostins; C101044:RTKI cpd; D066246:ErbB Receptors; D051057:Proto-Oncogene Proteins c-akt; D043802:GTP-Binding Protein alpha Subunits, Gq-G11