The class II phosphatidylinositol 3 kinase C2β is required for the activation of the K+ channel KCa3.1 and CD4 T-cells

Shekhar Srivastava, Lie Di, Olga Zhdanova, Zhai Li, Santosha Vardhana, Qi Wan, Ying Yan, Rajat Varma, Jonathan Backer, Heike Wulff, Michael L. Dustin, Edward Y. Skolnik

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Abstract

The Ca2+-activated K+ channel KCa3.1 is required for Ca2+ influx and the subsequent activation of T-cells. We previously showed that nucleoside diphosphate kinase beta (NDPK-B), a mammalian histidine kinase, directly phosphorylates and activates KCa3.1 and is required for the activation of human CD4 T lymphocytes. We now show that the class II phosphatidylinositol 3 kinase C2β (PI3K-C2β) is activated by the T-cell receptor (TCR) and functions upstream of NDPK-B to activate KCa3.1 channel activity. Decreased expression of PI3K-C2β by siRNA in human CD4 T-cells resulted in inhibition of KCa3.1 channel activity. The inhibition was due to decreased phosphatidylinositol 3-phosphate [PI(3)P] because dialyzing PI3K-C2β siRNA-treated T-cells with PI(3)P rescued KCa3.1 channel activity. Moreover, overexpression of PI3K-C2β in KCa3.1-transfected Jurkat T-cells led to increased TCR-stimulated activation of KCa3.1 and Ca2+ influx, whereas silencing of PI3K-C2β inhibited both responses. Using total internal reflection fluorescence microscopy and planar lipid bilayers, we found that PI3K-C2β colocalized with Zap70 and the TCR in peripheral microclusters in the immunological synapse. This is the first demonstration that a class II PI3K plays a critical role in T-cell activation.

Original languageEnglish (US)
Pages (from-to)3783-3791
Number of pages9
JournalMolecular biology of the cell
Volume20
Issue number17
DOIs
Publication statusPublished - Sep 1 2009

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ASJC Scopus subject areas

  • Molecular Biology
  • Cell Biology

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