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Carbonic anhydrase II binds to and enhances activity of the na+/H+ exchanger
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- Author(s) / Creator(s)
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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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- Date created
- 2002-01-01
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- Type of Item
- Article (Published)
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- License
- Attribution 4.0 International