Lack of muscarinic regulation of Ca(2+) channels in G(i2)alpha gene knockout mouse hearts.
The purpose of the present study was to examine the role of G(i2)alpha in Ca(2+) channel regulation using G(i2)alpha gene knockout mouse ventricular myocytes. The whole cell voltage-clamp technique was used to study the effects of the muscarinic agonist carbachol (CCh) and the beta-adrenergic agonist isoproterenol (Iso) on cardiac L-type Ca(2+) currents in both 129Sv wild-type (WT) and G(i2)alpha gene knockout (G(i2)alpha-/-) mice. Perfusion with CCh significantly inhibited the Ca(2+) current in WT cells, and this effect was reversed by adding atropine to the CCh-containing solution. In contrast, CCh did not affect Ca(2+) currents in G(i2)alpha-/- ventricular myocytes. Addition of CCh to Iso-containing solutions attenuated the Iso-stimulated Ca(2+) current in WT cardiomyocytes but not in G(i2)alpha-/- cells. These findings demonstrate that, whereas the Iso-G(s)alpha signal pathway is intact in G(i2)alpha gene knockout mouse hearts, these cells lack the inhibitory regulation of Ca(2+) channels by CCh. Therefore, G(i2)alpha is necessary for the muscarinic regulation of Ca(2+) channels in the mouse heart. Further studies are needed to delineate the possible interaction of G(i) and other cell signaling proteins and to clarify the level of interaction of G protein-coupled regulation of L-type Ca(2+) current in the heart.
Chen
F
F
Department of Pediatrics, University of California School of Medicine, Los Angeles, California 90095, USA. fchen@mednet.ucla.edu
Spicher
K
K
Jiang
M
M
Birnbaumer
L
L
Wetzel
G T
GT
D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D020746:Calcium Channels, L-Type / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology; D018679:Cholinergic Agonists / Q000494:pharmacology; D051960:GTP-Binding Protein alpha Subunit, Gi2; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000235:genetics* / Q000378:metabolism*; D007545:Isoproterenol / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D051379:Mice; D008815:Mice, Inbred Strains; D018345:Mice, Knockout; D018727:Muscarinic Antagonists / Q000494:pharmacology; D018485:Muscle Fibers, Skeletal / Q000378:metabolism; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000378:metabolism*; D011869:Radioligand Assay; D011976:Receptors, Muscarinic / Q000378:metabolism*; D012601:Scopolamine / Q000494:pharmacology; D015398:Signal Transduction / Q000502:physiology; D014316:Tritium
D000318:Adrenergic beta-Agonists; D020746:Calcium Channels, L-Type; D018679:Cholinergic Agonists; D018727:Muscarinic Antagonists; D011518:Proto-Oncogene Proteins; D011976:Receptors, Muscarinic; D014316:Tritium; D001285:Atropine; D002217:Carbachol; D012601:Scopolamine; D051960:GTP-Binding Protein alpha Subunit, Gi2; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; C498016:Gnai2 protein, mouse; D007545:Isoproterenol; D002118:Calcium