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A calcineurin homologous protein inhibits GTPase-stimulated Na-H exchange.

Activation of the ubiquitously expressed Na-H exchanger, NHE1, results in an increased efflux of intracellular H+. The increase in intracellular pH associated with this H+ efflux may contribute to regulating cell proliferation, differentiation, and neoplastic transformation. Although NHE1 activity is stimulated by growth factors and hormones acting through multiple GTPase-mediated pathways, little is known about how the exchanger is directly regulated. Using expression library screening, we identified a novel protein that specifically binds to NHE1 at a site that is critical for growth factor stimulation of exchange activity. This protein is homologous to calcineurin B and calmodulin and is designated CHP for calcineurin B homologous protein. Like NHE1, CHP is widely expressed in human tissues. Transient overexpression of CHP inhibits serum- and GTP-ase-stimulated NHE1 activity. CHP is a phosphoprotein and expression of constitutively activated GTPases decreases CHP phosphorylation. The phosphorylation state of CHP may therefore be an important signal controlling mitogenic regulation of NHE1.

Pubmed ID: 8901634


  • Lin X
  • Barber DL


Proceedings of the National Academy of Sciences of the United States of America

Publication Data

October 29, 1996

Associated Grants

  • Agency: NIDDK NIH HHS, Id: DK 40259
  • Agency: NIGMS NIH HHS, Id: GM 47413

Mesh Terms

  • Amino Acid Sequence
  • Arabidopsis Proteins
  • Base Sequence
  • Calcium-Binding Proteins
  • GTP Phosphohydrolases
  • Humans
  • Molecular Sequence Data
  • Phosphorylation
  • Sequence Alignment
  • Sodium-Hydrogen Antiporter