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Localization of cardiac L-type Ca(2+) channels to a caveolar macromolecular signaling complex is required for beta(2)-adrenergic regulation.

Abstract：

:L-type Ca(2+) channels play a critical role in regulating Ca(2+)-dependent signaling in cardiac myocytes, including excitation-contraction coupling; however, the subcellular localization of cardiac L-type Ca(2+) channels and their regulation are incompletely understood. Caveolae are specialized microdomains of the plasmalemma rich in signaling molecules and supported by the structural protein caveolin-3 in muscle. Here we demonstrate that a subpopulation of L-type Ca(2+) channels is localized to caveolae in ventricular myocytes as part of a macromolecular signaling complex necessary for beta(2)-adrenergic receptor (AR) regulation of I(Ca,L). Immunofluorescence studies of isolated ventricular myocytes using confocal microscopy detected extensive colocalization of caveolin-3 and the major pore-forming subunit of the L-type Ca channel (Ca(v)1.2). Immunogold electron microscopy revealed that these proteins colocalize in caveolae. Immunoprecipitation from ventricular myocytes using anti-Ca(v)1.2 or anti-caveolin-3 followed by Western blot analysis showed that caveolin-3, Ca(v)1.2, beta(2)-AR (not beta(1)-AR), G protein alpha(s), adenylyl cyclase, protein kinase A, and protein phosphatase 2a are closely associated. To determine the functional impact of the caveolar-localized beta(2)-AR/Ca(v)1.2 signaling complex, beta(2)-AR stimulation (salbutamol plus atenolol) of I(Ca,L) was examined in pertussis toxin-treated neonatal mouse ventricular myocytes. The stimulation of I(Ca,L) in response to beta(2)-AR activation was eliminated by disruption of caveolae with 10 mM methyl beta-cyclodextrin or by small interfering RNA directed against caveolin-3, whereas beta(1)-AR stimulation (norepinephrine plus prazosin) of I(Ca,L) was not altered. These findings demonstrate that subcellular localization of L-type Ca(2+) channels to caveolar macromolecular signaling complexes is essential for regulation of the channels by specific signaling pathways.

journal_name

Proc Natl Acad Sci U S A

journal_title

Proceedings of the National Academy of Sciences of the United States of America

authors

Balijepalli RC,Foell JD,Hall DD,Hell JW,Kamp TJ

doi

10.1073/pnas.0503465103

subject

Has Abstract

pub_date

2006-05-09 00:00:00

pages

7500-5

issue

eissn

0027-8424

issn

1091-6490

pii

0503465103

journal_volume

103

pub_type

杂志文章

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Localization of cardiac L-type Ca(2+) channels to a caveolar macromolecular signaling complex is required for beta(2)-adrenergic regulation.