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

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  • 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.

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    Article (Published)
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    Attribution 4.0 International
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    • Li, Xiuju J., Alvarez, Bernando, Casey, Joseph R., Reithmeier, Reinhart A. F., & Fliegel, Larry. (2002). Carbonic anhydrase II binds to and enhances activity of the na+/H+ exchanger. Journal of Biological Chemistry, 277(39), 36085-36091.
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