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An amino acid mutation in a potassium channel that prevents inhibition by protein kinase C

A E Busch1, M D Varnum, R A North

  • 1Vollum Institute, Oregon Health Sciences University, Portland 97201.

Science (New York, N.Y.)
|March 27, 1992
PubMed

Insights

Protein kinase C activators inhibit a rat kidney potassium channel current. This inhibition occurs via direct phosphorylation of the channel protein at Ser103, as shown by experiments with mutated channels.

Area of Science:

  • Molecular Biology
  • Neuroscience
  • Biochemistry

Background:

  • Voltage-dependent potassium channels are crucial for neuronal excitability.
  • Protein kinase C (PKC) is involved in regulating ion channel function.
  • Understanding the specific mechanisms of potassium channel modulation is vital for neuroscience research.

Purpose of the Study:

  • To investigate the effect of protein kinase C activators on a cloned rat kidney potassium channel.
  • To determine the specific site and mechanism of potassium channel inhibition by PKC.

Main Methods:

  • Expression of a rat kidney potassium channel protein in Xenopus oocytes.
  • Application of PKC activators (1-oleoyl-2-acetyl-rac-glycerol and phorbol 12,13-didecanoate) and a kinase inhibitor (staurosporine).
  • Site-directed mutagenesis of the channel protein (Ser103 to Ala) to assess the role of specific phosphorylation sites.

Main Results:

  • PKC activators significantly inhibited the potassium channel current.
  • Staurosporine blocked the inhibitory effect of PKC activators, suggesting a kinase-dependent mechanism.
  • Mutation of Ser103 to Alanine abolished the inhibition, while other channel properties remained unaffected.

Conclusions:

  • The inhibition of the rat kidney potassium channel current by PKC activators is mediated by direct phosphorylation of the channel subunit protein.
  • Serine 103 is identified as the critical site for this phosphorylation-dependent regulation.

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