TY - JOUR
T1 - Localization of cardiac sodium channels in caveolin-rich membrane domains
T2 - Regulation of sodium current amplitude
AU - Yarbrough, Tracy L.
AU - Lu, Tong
AU - Lee, Hon Chi
AU - Shibata, Erwin F.
PY - 2002/3/8
Y1 - 2002/3/8
N2 - This study demonstrates that caveolae, omega-shaped membrane invaginations, are involved in cardiac sodium channel regulation by a mechanism involving the α subunit of the stimulatory heterotrimeric G-protein, Gαs, via stimulation of the cell surface β-adrenergic receptor. Stimulation of β-adrenergic receptors with 10 μmol/L isoproterenol in the presence of a protein kinase A inhibitor increased the whole-cell sodium current by a "direct" cAMP-independent G-protein mechanism. The addition of antibodies against caveolin-3 to the cell's cytoplasm via the pipette solution abrogated this direct G protein-induced increase in sodium current, whereas antibodies to caveolin-1 or caveolin-2 did not. Voltage-gated sodium channel proteins were found to associate with caveolin-rich membranes obtained by detergent-free buoyant density separation. The purity of the caveolar membrane fraction was verified by Western blot analyses, which indicated that endoplasmic/sarcoplasmic reticulum, endosomal compartments, Golgi apparatus, clathrin-coated vesicles, and sarcolemmal membranes were excluded from the caveolin-rich membrane fraction. Additionally, the sodium channel was found to colocalize with caveolar membranes by immunoprecipitation, indirect immunofluorescence, and immunogold transmission electron microscopy. These results suggest that stimulation of β-adrenergic receptors, and thereby Gαs, promotes the presentation of cardiac sodium channels associated with caveolar membranes to the sarcolemma.
AB - This study demonstrates that caveolae, omega-shaped membrane invaginations, are involved in cardiac sodium channel regulation by a mechanism involving the α subunit of the stimulatory heterotrimeric G-protein, Gαs, via stimulation of the cell surface β-adrenergic receptor. Stimulation of β-adrenergic receptors with 10 μmol/L isoproterenol in the presence of a protein kinase A inhibitor increased the whole-cell sodium current by a "direct" cAMP-independent G-protein mechanism. The addition of antibodies against caveolin-3 to the cell's cytoplasm via the pipette solution abrogated this direct G protein-induced increase in sodium current, whereas antibodies to caveolin-1 or caveolin-2 did not. Voltage-gated sodium channel proteins were found to associate with caveolin-rich membranes obtained by detergent-free buoyant density separation. The purity of the caveolar membrane fraction was verified by Western blot analyses, which indicated that endoplasmic/sarcoplasmic reticulum, endosomal compartments, Golgi apparatus, clathrin-coated vesicles, and sarcolemmal membranes were excluded from the caveolin-rich membrane fraction. Additionally, the sodium channel was found to colocalize with caveolar membranes by immunoprecipitation, indirect immunofluorescence, and immunogold transmission electron microscopy. These results suggest that stimulation of β-adrenergic receptors, and thereby Gαs, promotes the presentation of cardiac sodium channels associated with caveolar membranes to the sarcolemma.
KW - Adrenergic
KW - Cardiac
KW - Caveolae
KW - Ion channel
KW - Signal transduction
UR - http://www.scopus.com/inward/record.url?scp=0037040840&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0037040840&partnerID=8YFLogxK
U2 - 10.1161/hh0402.105177
DO - 10.1161/hh0402.105177
M3 - Article
C2 - 11884374
AN - SCOPUS:0037040840
SN - 0009-7330
VL - 90
SP - 443
EP - 449
JO - Circulation research
JF - Circulation research
IS - 4
ER -