Stable expression and coupling of cardiac L-type Ca2+ channels with beta 1-adrenoceptors.
A number of neurotransmitters modulate cardiac dihydropyridine-sensitive L-type Ca2+ channels through several homologous G protein-coupled receptors. Previous studies that have examined receptor-Ca2+ channel interactions have suffered because of the coexpression of various receptor subtypes in native cells. To study the functional coupling of a particular receptor subtype to these channels, rabbit cardiac Ca2+ channel alpha 1 and skeletal beta and alpha 2/delta subunits were stably expressed in baby hamster kidney cells. In this stable cell line, Ca2+ channels remained at high levels (> 1000 fmol/mg protein, or 2700 channels per cell) over extended times. The expressed recombinant Ca2+ channels displayed the voltage dependence of activation and inactivation, unitary conductance, and pharmacology characteristic of native cardiac L-type Ca2+ channels. Subsequent coexpression of the beta 1-adrenoceptors (150 to 300 fmol/mg protein) with the Ca2+ channels resulted in cell responsiveness to the extracellular application of isoproterenol. These results indicate that heterogeneous expression in mammalian cells provides a useful system for studying both biophysical analysis of Ca2+ channel properties and receptor-coupled regulatory processes.
Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, OH 45267-0575.
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A
Yatani
M
M
Wakamori
T
T
Niidome
S
S
Yamamoto
I
I
Tanaka
Y
Y
Mori
K
K
Katayama
S
S
Green
D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D015220:Calcium Channels / Q000502:physiology*; D002478:Cells, Cultured; D006224:Cricetinae; D007545:Isoproterenol / Q000494:pharmacology; D017275:Isradipine / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism*; D011817:Rabbits; D018342:Receptors, Adrenergic, beta-1 / Q000502:physiology*
D015220:Calcium Channels; D018342:Receptors, Adrenergic, beta-1; D003994:Bucladesine; D007545:Isoproterenol; D017275:Isradipine