The patch-clamp technique was employed to investigate phosphorylation/dephosphorylation-dependent modulation of L-type Ca2+ channels in smooth-muscle cells isolated from human umbilical vein. Okadaic acid, an inhibitor of phosphoprotein phosphatases type 1 (PP1) and 2A (PP2A), increased the probability of channels being in the open state (Po) in intact cells. This increase in Po was due mainly to promotion of long-lasting channel openings, i.e. promotion of ‘mode 2’ gating behaviour. Exposure of the cytoplasmic side of excised patches of membrane to the purified catalytic subunit of PP2A (PP2Ac) resulted in the opposite modulation of channel function. PP2Ac (0.2 unit/ml) reduced the Po of Ca2+ channels mainly via suppression of ‘mode 2’ gating. This effect of PP2Ac was completely prevented by 1 µM okadaic acid. The catalytic subunit of PP1 (0.2 unit/ml), however, barely affected channel activity. Our results provide evidence for a PP2A-sensitive regulatory site that controls modal gating of L-type Ca2+ channels in smooth muscle.
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September 1996
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Research Article|
September 01 1996
A type 2A phosphatase-sensitive phosphorylation site controls modal gating of L-type Ca2+ channels in human vascular smooth-muscle cells
Klaus GROSCHNER;
Klaus GROSCHNER
§
*Institut für Pharmakologie und Toxikologie, Karl-Franzens-Universität Graz, Universitätsplatz 2, A-8010 Graz, Austria
§To whom correspondence should be addressed.
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Klaus SCHUHMANN;
Klaus SCHUHMANN
*Institut für Pharmakologie und Toxikologie, Karl-Franzens-Universität Graz, Universitätsplatz 2, A-8010 Graz, Austria
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Gottfried MIESKES;
Gottfried MIESKES
†Abteilung für Klinische Biochemie, Universität Göttingen, D-37075 Göttingen, Federal Republic of Germany
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Werner BAUMGARTNER;
Werner BAUMGARTNER
‡Institut für Biophysik, Universität Linz, A-4040 Linz, Austria
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Christoph ROMANIN
Christoph ROMANIN
‡Institut für Biophysik, Universität Linz, A-4040 Linz, Austria
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Publisher: Portland Press Ltd
Received:
February 23 1996
Revision Received:
May 10 1996
Accepted:
May 14 1996
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London © 1996
1996
Biochem J (1996) 318 (2): 513–517.
Article history
Received:
February 23 1996
Revision Received:
May 10 1996
Accepted:
May 14 1996
Citation
Klaus GROSCHNER, Klaus SCHUHMANN, Gottfried MIESKES, Werner BAUMGARTNER, Christoph ROMANIN; A type 2A phosphatase-sensitive phosphorylation site controls modal gating of L-type Ca2+ channels in human vascular smooth-muscle cells. Biochem J 1 September 1996; 318 (2): 513–517. doi: https://doi.org/10.1042/bj3180513
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