Phosphorylation-dependent regulation of Kv2.1 Channel activity at tyrosine 124 by Src and by protein-tyrosine phosphatase epsilon.
Voltage-gated potassium (Kv) channels are a complex and heterogeneous family of proteins that play major roles in brain and cardiac excitability. Although Kv channels are activated by changes in cell membrane potential, tyrosine phosphorylation of channel subunits can modulate the extent of channel activation by depolarization. We have previously shown that dephosphorylation of Kv2.1 by the nonreceptor-type tyrosine phosphatase PTPepsilon (cyt-PTPepsilon) down-regulates channel activity and counters its phosphorylation and up-regulation by Src or Fyn. In the present study, we identify tyrosine 124 within the T1 cytosolic domain of Kv2.1 as a target site for the activities of Src and cyt-PTPepsilon. Tyr(124) is phosphorylated by Src in vitro; in whole cells, Y124F Kv2.1 is significantly less phosphorylated by Src and loses most of its ability to bind the D245A substrate-trapping mutant of cyt-PTPepsilon. Phosphorylation of Tyr(124) is critical for Src-mediated up-regulation of Kv2.1 channel activity, since Y124F Kv2.1-mediated K(+) currents are only marginally up-regulated by Src, in contrast with a 3-fold up-regulation of wild-type Kv2.1 channels by the kinase. Other properties of Kv2.1, such as expression levels, subcellular localization, and voltage dependence of channel activation, are unchanged in Y124F Kv2.1, indicating that the effects of the Y124F mutation are specific. Together, these results indicate that Tyr(124) is a significant site at which the mutually antagonistic activities of Src and cyt-PTPepsilon affect Kv2.1 phosphorylation and activity.
Tiran
Zohar
Z
Department of Molecular Genetics, The Weizmann Institute of Science, Rehovot 76100, Israel.
Peretz
Asher
A
Attali
Bernard
B
Elson
Ari
A
D000818:Animals; D002460:Cell Line; D051668:Delayed Rectifier Potassium Channels; D006801:Humans; D015640:Ion Channel Gating / Q000502:physiology*; D051379:Mice; D010766:Phosphorylation; D015221:Potassium Channels / Q000235:genetics / Q000378:metabolism*; D024642:Potassium Channels, Voltage-Gated; D017027:Protein Tyrosine Phosphatases / Q000502:physiology*; D051381:Rats; D054630:Receptor-Like Protein Tyrosine Phosphatases, Class 4; D051669:Shab Potassium Channels; D015398:Signal Transduction / Q000502:physiology; D014443:Tyrosine / Q000502:physiology; D015854:Up-Regulation; D019061:src-Family Kinases / Q000502:physiology*
D051668:Delayed Rectifier Potassium Channels; C496988:KCNB1 protein, human; C496990:Kcnb1 protein, mouse; C496991:Kcnb1 protein, rat; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D051669:Shab Potassium Channels; D014443:Tyrosine; D019061:src-Family Kinases; C490825:PTPRE protein, human; D017027:Protein Tyrosine Phosphatases; C098067:Ptpre protein, mouse; C490826:Ptpre protein, rat; D054630:Receptor-Like Protein Tyrosine Phosphatases, Class 4