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Phosphorylation-dependent regulation of Kv2.1 Channel activity at tyrosine 124 by Src and by protein-tyrosine

Zohar Tiran1, Asher Peretz, Bernard Attali

  • 1Department of Molecular Genetics, The Weizmann Institute of Science, Rehovot 76100, Israel.

The Journal of Biological Chemistry
|March 5, 2003
PubMed

Insights

Tyrosine 124 on Kv2.1 channels is a key site for phosphorylation by Src and dephosphorylation by PTPepsilon, regulating channel activity in the brain and heart.

Area of Science:

  • Molecular and Cellular Neuroscience
  • Ion Channel Physiology
  • Signal Transduction

Background:

  • Voltage-gated potassium (Kv) channels are crucial for neuronal and cardiac excitability.
  • Tyrosine phosphorylation dynamically regulates Kv channel function.
  • PTPepsilon (cyt-PTPepsilon) dephosphorylates and down-regulates Kv2.1, opposing Src/Fyn kinase activity.

Purpose of the Study:

  • To identify the specific tyrosine residue on Kv2.1 targeted by Src and cyt-PTPepsilon.
  • To elucidate the functional consequences of phosphorylating this site on Kv2.1 channel activity.

Main Methods:

  • In vitro kinase assays using purified Src and Kv2.1.
  • Whole-cell patch-clamp electrophysiology in cells expressing wild-type and mutant Kv2.1.
  • Co-immunoprecipitation studies with substrate-trapping mutants of cyt-PTPepsilon.

Main Results:

  • Tyrosine 124 (Tyr124) in the Kv2.1 T1 domain was identified as the critical phosphorylation site.
  • Src directly phosphorylates Tyr124 in vitro and in cells.
  • Mutation of Tyr124 to phenylalanine (Y124F) abolished Src-mediated channel potentiation and reduced cyt-PTPepsilon binding.
  • Y124F Kv2.1 channels showed significantly less Src-induced current potentiation compared to wild-type.

Conclusions:

  • Tyr124 is a key regulatory site for Kv2.1 channel activity modulation by Src and cyt-PTPepsilon.
  • Phosphorylation of Tyr124 by Src is essential for channel up-regulation.
  • This study reveals a specific molecular mechanism for antagonistic regulation of Kv2.1 by tyrosine kinases and phosphatases.

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