Protein histidine phosphatase 1 negatively regulates CD4 T cells by inhibiting the K+ channel KCa3.1

Shekhar Srivastava, Olga Zhdanova, Lie Di, Zhai Li, Mamdouh Albaqumi, Heike Wulff, Edward Y. Skolnik

Research output: Contribution to journalArticlepeer-review

84 Scopus citations


The calcium activated K+ channel KCa3.1 plays an important role in T lymphocyte Ca2+ signaling by helping to maintain a negative membrane potential, which provides an electrochemical gradient to drive Ca 2+ influx. We previously showed that nucleoside diphosphate kinase beta (NDPK-B), a mammalian histidine kinase, is required for KCa3.1 channel activation in human CD4 T lymphocytes. We now show that the mammalian protein histidine phosphatase (PHPT-1) directly binds and inhibits KCa3.1 by dephosphorylating histidine 358 on KCa3.1. Overexpression of wild-type, but not a phosphatase dead, PHPT-1 inhibited KCa3.1 channel activity. Decreased expression of PHPT-1 by siRNA in human CD4 T cells resulted in an increase in KCa3.1 channel activity and increased Ca2+ influx and proliferation after T cell receptor (TCR) activation, indicating that endogenous PHPT-1 functions to negatively regulate CD4 T cells. Our findings provide a previously unrecognized example of a mammalian histidine phosphatase negatively regulating TCR signaling and are one of the few examples of histidine phosphorylation/ dephosphorylation influencing a biological process in mammals.

Original languageEnglish (US)
Pages (from-to)14442-14446
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number38
StatePublished - Sep 23 2008


  • CRAC channel
  • Histidine kinase
  • NM23-H2
  • Nucleoside diphosphate kinase
  • PHPT-1

ASJC Scopus subject areas

  • General


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