AKAP-Mediated Targeting of Protein Kinase A Regulates Contractility in Cardiac Myocytes
作者:
Mary Fink,
Daniel Zakhary,
Julie Mackey,
Russell Desnoyer,
Carolyn Apperson-Hansen,
Derek Damron,
Meredith Bond,
期刊:
Circulation Research: Journal of the American Heart Association
(OVID Available online 2001)
卷期:
Volume 88,
issue 3
页码: 291-297
ISSN:0009-7330
年代: 2001
出版商: OVID
关键词: A-kinase anchoring proteins;protein kinase A;cardiac myocyte;&bgr;-adrenergic receptor;contractility
数据来源: OVID
摘要:
Abstract—Compartmentalization of cAMP-dependent protein kinase A (PKA) by A-kinase anchoring proteins (AKAPs) targets PKA to distinct subcellular locations in many cell types. However, the question of whether AKAP-mediated PKA anchoring in the heart regulates cardiac contractile function has not been addressed. We disrupted AKAP-mediated PKA anchoring in cardiac myocytes by introducing, via adenovirus-mediated gene transfer, Ht31, a peptide that binds the PKA regulatory subunit type II (RII) with high affinity. This peptide competes with endogenous AKAPs for RII binding. Ht31P (a proline-substituted derivative), which does not bind RII, was used as a negative control. We then investigated the effects of Ht31 expression on RII distribution, Ca2+cycling, cell shortening, and PKA-dependent substrate phosphorylation. By confocal microscopy, we showed redistribution of RII from the perinuclear region and from periodic transverse striations in Ht31P-expressing cells to a diffuse cytosolic localization in Ht31-expressing cells. In the presence of 10 nmol/L isoproterenol, Ht31-expressing myocytes displayed an increased rate and amplitude of cell shortening and relaxation compared with control cells (uninfected and Ht31P-expressing myocytes); with isoproterenol stimulation we observed decreased time to 90% decline in Ca2+but no significant difference between Ht31-expressing and control cells in the rate of Ca2+cycling or amplitude of the Ca2+transient. The increase in PKA-dependent phosphorylation of troponin I and myosin binding protein C on isoproterenol stimulation was significantly reduced in Ht31-expressing cells compared with controls. Our results demonstrate that, in response to &bgr;-adrenergic stimulation, cardiomyocyte function and substrate phosphorylation by PKA is regulated by targeting of PKA by AKAPs.
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