Carbonic anhydrase II binds to and enhances activity of the na+/H+ exchanger

• Author(s) / Creator(s)

  • Li, Xiuju J.
  • Alvarez, Bernando
  • Casey, Joseph R.
  • Reithmeier, Reinhart A. F.
  • Fliegel, Larry

• We examined the ability of carbonic anhydrase II to bind to and affect the transport efficiency of the NHE1 isoform of the mammalian Na+/H+ exchanger. The C-terminal region of NHE1 was expressed in Escherichia coli fused with an N-terminal glutathionineS-transferase or with a C-terminal polyhistidine tag. Using a microtiter plate binding assay we showed that the C-terminal region of NHE1 binds carbonic anhydrase II (CAII) and binding was stimulated by low pH and blocked by antibodies against the C-terminal of NHE1. The binding to NHE1 was confirmed by demonstrating protein-protein interaction using affinity blotting with CAII and immobilized NHE1 fusion proteins. CAII co-immunoprecipitated with NHE1 from CHO cells suggesting the proteins form a complex in vivo. In cells expressing CAII and NHE1, the H+ transport rate was almost 2-fold greater than in cells expressing NHE1 alone. The CAII inhibitor acetazolamide significantly decreased the H+ transport rate of NHE1 and transfection with a dominant negative CAII inhibited NHE1 activity. Phosphorylation of the C-terminal of NHE1 greatly increased the binding of CAII. Our study suggests that NHE1 transport efficiency is influenced by CAII, likely through a direct interaction at the C-terminal region. Regulation of NHE1 activity by phosphorylation could involve modulation of CAII binding.

• Date created

  2002-01-01

• Subjects / Keywords

  • Residues
  • Activated Protein-Kinase
  • Functional-Role
  • Myocardium
  • Anion-Exchanger
  • Site
  • Terminal Region
  • Localization
  • Intracellular PH
  • Identification

• Type of Item

  Article (Published)

• DOI

  https://doi.org/10.7939/r3-39rf-zy22

• License

  Attribution 4.0 International