GSBS Student Publications
Title
The Ca2+ channel beta3 subunit differentially modulates G-protein sensitivity of alpha1A and alpha1B Ca2+ channels
UMMS Affiliation
Graduate School of Biomedical Sciences; Department of Pharmacology and Molecular Toxicology; Program in Neuroscience
Date
2-14-1998
Document Type
Article
Medical Subject Headings
Acetylcholine; Animals; Calcium Channels; Electric Conductivity; Electric Stimulation; Ethylmaleimide; GTP-Binding Proteins; Gene Expression; Ion Channel Gating; Oocytes; Patch-Clamp Techniques; Plasmids; Receptor, Muscarinic M2; Receptors, Muscarinic; Sulfhydryl Reagents; Virulence Factors, Bordetella; Xenopus
Disciplines
Life Sciences | Medicine and Health Sciences
Abstract
We have shown previously that the Ca2+ channel beta3 subunit is capable of modulating tonic G-protein inhibition of alpha1A and alpha1B Ca2+ channels expressed in oocytes. Here we determine the modulatory effect of the Ca2+ channel beta3 subunit on M2 muscarinic receptor-activated G-protein inhibition and whether the beta3 subunit modulates the G-protein sensitivity of alpha1A and alpha1B currents equivalently. To compare the relative inhibition by muscarinic activation, we have used successive ACh applications to remove the large tonic inhibition of these channels. We show that the resulting rebound potentiation results entirely from the loss of tonic G-protein inhibition; although the currents are temporarily relieved of tonic inhibition, they are still capable of undergoing inhibition through the muscarinic pathway. Using this rebound protocol, we demonstrate that the inhibition of peak current amplitude produced by M2 receptor activation is similar for alpha1A and alpha1B calcium currents. However, the contribution of the voltage-dependent component of inhibition, characterized by reduced inhibition at very depolarized voltage steps and the relief of inhibition by depolarizing prepulses, was slightly greater for the alpha1B current than for the alpha1A current. After co-expression of the beta3 subunit, the sensitivity to M2 receptor-induced G-protein inhibition was reduced for both alpha1A and alpha1B currents; however, the reduction was significantly greater for alpha1A currents. Additionally, the difference in the voltage dependence of inhibition of alpha1A and alpha1B currents was heightened after co-expression of the Ca2+ channel beta3 subunit. Such differential modulation of sensitivity to G-protein modulation may be important for fine tuning release in neurons that contain both of these Ca2+ channels.
Rights and Permissions
Citation: J Neurosci. 1998 Feb 1;18(3):878-86.
Related Resources
Journal Title
The Journal of neuroscience : the official journal of the Society for Neuroscience
PubMed ID
9437009
Repository Citation
Roche, John P. and Treistman, Steven N., "The Ca2+ channel beta3 subunit differentially modulates G-protein sensitivity of alpha1A and alpha1B Ca2+ channels" (1998). GSBS Student Publications. 1013.
https://escholarship.umassmed.edu/gsbs_sp/1013