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Modulation of N-Type Calcium Channel Activity by G-Proteins and Protein Kinase C
N-type voltage-gated calcium channel activity in rat superior cervical ganglion neurons is modulated by a variety of pathways. Activation of heterotrimeric G-proteins reduces whole-cell current amplitude, whereas phosphorylation by protein kinase C leads to an increase in current amplitude. It has b...
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Formato: | Texto |
Lenguaje: | English |
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The Rockefeller University Press
2000
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2217210/ https://www.ncbi.nlm.nih.gov/pubmed/10694257 |
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author | Barrett, Curtis F. Rittenhouse, Ann R. |
author_facet | Barrett, Curtis F. Rittenhouse, Ann R. |
author_sort | Barrett, Curtis F. |
collection | PubMed |
description | N-type voltage-gated calcium channel activity in rat superior cervical ganglion neurons is modulated by a variety of pathways. Activation of heterotrimeric G-proteins reduces whole-cell current amplitude, whereas phosphorylation by protein kinase C leads to an increase in current amplitude. It has been proposed that these two distinct pathways converge on the channel's pore-forming α(1B) subunit, such that the actions of one pathway can preclude those of the other. In this study, we have characterized further the actions of PKC on whole-cell barium currents in neonatal rat superior cervical ganglion neurons. We first examined whether the effects of G-protein–mediated inhibition and phosphorylation by PKC are mutually exclusive. G-proteins were activated by including 0.4 mM GTP or 0.1 mM GTP-γ-S in the pipette, and PKC was activated by bath application of 500 nM phorbol 12-myristate 13-acetate (PMA). We found that activated PKC was unable to reverse GTP-γ-S–induced inhibition unless prepulses were applied, indicating that reversal of inhibition by phosphorylation appears to occur only after dissociation of the G-protein from the channel. Once inhibition was relieved, activation of PKC was sufficient to prevent reinhibition of current by G-proteins, indicating that under phosphorylating conditions, channels are resistant to G-protein–mediated modulation. We then examined what effect, if any, phosphorylation by PKC has on N-type barium currents beyond antagonizing G-protein–mediated inhibition. We found that, although G-protein activation significantly affected peak current amplitude, fast inactivation, holding-potential–dependent inactivation, and voltage-dependent activation, when G-protein activation was minimized by dialysis of the cytoplasm with 0.1 mM GDP-β-S, these parameters were not affected by bath application of PMA. These results indicate that, under our recording conditions, phosphorylation by PKC has no effect on whole-cell N-type currents, other than preventing inhibition by G-proteins. |
format | Text |
id | pubmed-2217210 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2000 |
publisher | The Rockefeller University Press |
record_format | MEDLINE/PubMed |
spelling | pubmed-22172102008-04-22 Modulation of N-Type Calcium Channel Activity by G-Proteins and Protein Kinase C Barrett, Curtis F. Rittenhouse, Ann R. J Gen Physiol Original Article N-type voltage-gated calcium channel activity in rat superior cervical ganglion neurons is modulated by a variety of pathways. Activation of heterotrimeric G-proteins reduces whole-cell current amplitude, whereas phosphorylation by protein kinase C leads to an increase in current amplitude. It has been proposed that these two distinct pathways converge on the channel's pore-forming α(1B) subunit, such that the actions of one pathway can preclude those of the other. In this study, we have characterized further the actions of PKC on whole-cell barium currents in neonatal rat superior cervical ganglion neurons. We first examined whether the effects of G-protein–mediated inhibition and phosphorylation by PKC are mutually exclusive. G-proteins were activated by including 0.4 mM GTP or 0.1 mM GTP-γ-S in the pipette, and PKC was activated by bath application of 500 nM phorbol 12-myristate 13-acetate (PMA). We found that activated PKC was unable to reverse GTP-γ-S–induced inhibition unless prepulses were applied, indicating that reversal of inhibition by phosphorylation appears to occur only after dissociation of the G-protein from the channel. Once inhibition was relieved, activation of PKC was sufficient to prevent reinhibition of current by G-proteins, indicating that under phosphorylating conditions, channels are resistant to G-protein–mediated modulation. We then examined what effect, if any, phosphorylation by PKC has on N-type barium currents beyond antagonizing G-protein–mediated inhibition. We found that, although G-protein activation significantly affected peak current amplitude, fast inactivation, holding-potential–dependent inactivation, and voltage-dependent activation, when G-protein activation was minimized by dialysis of the cytoplasm with 0.1 mM GDP-β-S, these parameters were not affected by bath application of PMA. These results indicate that, under our recording conditions, phosphorylation by PKC has no effect on whole-cell N-type currents, other than preventing inhibition by G-proteins. The Rockefeller University Press 2000-03-01 /pmc/articles/PMC2217210/ /pubmed/10694257 Text en © 2000 The Rockefeller University Press This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.rupress.org/terms). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 4.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/4.0/). |
spellingShingle | Original Article Barrett, Curtis F. Rittenhouse, Ann R. Modulation of N-Type Calcium Channel Activity by G-Proteins and Protein Kinase C |
title | Modulation of N-Type Calcium Channel Activity by G-Proteins and Protein Kinase C |
title_full | Modulation of N-Type Calcium Channel Activity by G-Proteins and Protein Kinase C |
title_fullStr | Modulation of N-Type Calcium Channel Activity by G-Proteins and Protein Kinase C |
title_full_unstemmed | Modulation of N-Type Calcium Channel Activity by G-Proteins and Protein Kinase C |
title_short | Modulation of N-Type Calcium Channel Activity by G-Proteins and Protein Kinase C |
title_sort | modulation of n-type calcium channel activity by g-proteins and protein kinase c |
topic | Original Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2217210/ https://www.ncbi.nlm.nih.gov/pubmed/10694257 |
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