G-protein beta-subunit specificity in the fast membrane-delimited inhibition of Ca2+ channels.
We investigated which subtypes of G-protein beta subunits participate in voltage-dependent modulation of N-type calcium channels. Calcium currents were recorded from cultured rat superior cervical ganglion neurons injected intranuclearly with DNA encoding five different G-protein beta subunits. Gbeta1 and Gbeta2 strongly mimicked the fast voltage-dependent inhibition of calcium channels produced by many G-protein-coupled receptors. The Gbeta5 subunit produced much weaker effects than Gbeta1 and Gbeta2, whereas Gbeta3 and Gbeta4 were nearly inactive in these electrophysiological studies. The specificity implied by these results was confirmed and extended using the yeast two-hybrid system to test for protein-protein interactions. Here, Gbeta1 or Gbeta2 coupled to the GAL4-activation domain interacted strongly with a channel sequence corresponding to the intracellular loop connecting domains I and II of a alpha1 subunit of the class B calcium channel fused to the GAL4 DNA-binding domain. In this assay, the Gbeta5 subunit interacted weakly, and Gbeta3 and Gbeta4 failed to interact. Together, these results suggest that Gbeta1 and/or Gbeta2 subunits account for most of the voltage-dependent inhibition of N-type calcium channels and that the linker between domains I and II of the calcium channel alpha1 subunit is a principal receptor for this inhibition.
García
D E
DE
Department of Physiology and Biophysics, University of Washington, Seattle, Washington 98195, USA.
Li
B
B
García-Ferreiro
R E
RE
Hernández-Ochoa
E O
EO
Yan
K
K
Gautam
N
N
Catterall
W A
WA
Mackie
K
K
Hille
B
B
D000320:Adrenergic Fibers / Q000737:chemistry / Q000187:drug effects / Q000502:physiology; D000818:Animals; D001665:Binding Sites / Q000502:physiology; D015220:Calcium Channels / Q000737:chemistry / Q000502:physiology*; D004271:DNA, Fungal / Q000494:pharmacology; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D044387:GTP-Binding Protein beta Subunits; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression / Q000502:physiology; D020962:Heterotrimeric GTP-Binding Proteins; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D029702:Schizosaccharomyces pombe Proteins; D017783:Superior Cervical Ganglion / Q000166:cytology; D013566:Sympathomimetics / Q000494:pharmacology; D015003:Yeasts / Q000737:chemistry / Q000502:physiology
D015220:Calcium Channels; D004271:DNA, Fungal; D005656:Fungal Proteins; D044387:GTP-Binding Protein beta Subunits; C491082:Gnb1 protein, mouse; C490610:Gnb5 protein, rat; D012333:RNA, Messenger; D029702:Schizosaccharomyces pombe Proteins; D013566:Sympathomimetics; C101525:git5 protein, S pombe; D019204:GTP-Binding Proteins; D020962:Heterotrimeric GTP-Binding Proteins; D009638:Norepinephrine