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Basal dephosphorylation controls slow gating of L-type Ca2+ channels in human vascular smooth muscle

K Groschner1, K Schuhmann, W Baumgartner

  • 1Institut für Pharmakologie und Toxikologie, Karl-Franzens-Universität Graz, Austria.

FEBS Letters
|October 2, 1995
PubMed

Insights

Cellular phosphatase activity regulates vascular smooth muscle L-type Ca2+ channels. Tautomycin, a phosphatase inhibitor, reduced channel activity by altering gating states, suggesting a phosphorylation-dependent mechanism.

Area of Science:

  • Physiology
  • Pharmacology
  • Molecular Biology

Background:

  • Smooth muscle L-type Ca2+ channels are crucial for vascular tone.
  • Cellular phosphatases play a role in regulating ion channel function.
  • Phosphorylation is a key mechanism for modulating channel activity.

Purpose of the Study:

  • To investigate the role of cellular phosphatase activity in regulating smooth muscle L-type Ca2+ channels.
  • To determine the effect of tautomycin, a specific phosphatase inhibitor, on Ca2+ channel activity.
  • To elucidate the mechanism by which phosphatase activity influences Ca2+ channel gating.

Main Methods:

  • Isolation of smooth muscle cells from human umbilical vein.
  • Application of tautomycin (1-100 nM) to assess its effect on Ca2+ channel activity.
  • Use of protein kinase inhibitor H-7 (10 microM) to investigate the role of phosphorylation.
  • Analysis of channel gating kinetics, specifically the lifetime of unavailable states.

Main Results:

  • Tautomycin significantly inhibited Ca2+ channel activity in a dose-dependent manner.
  • The inhibition was primarily due to a reduction in channel availability, caused by prolonged unavailable states.
  • Pretreatment with protein kinase inhibitor H-7 blocked the inhibitory effect of tautomycin.
  • These findings indicate that phosphatase activity influences channel gating.

Conclusions:

  • Cellular phosphatase activity, specifically of serin/threonin phosphatases type 1 and 2A, down-regulates vascular smooth muscle L-type Ca2+ channels.
  • Modulation of slow gating between available and unavailable states is a key mechanism.
  • This represents a phosphorylation-dependent regulation of Ca2+ channels in vascular smooth muscle.

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