Kanadaptin Is a Protein That Interacts with the Kidney but Not the Erythroid Form of Band 3*
- From the ‡Department of Medicine and Physiology and§Department of Biochemistry, College of Physicians and Surgeons of Columbia University, New York, New York 10032
Abstract
Although epithelial membrane proteins are separately targeted to apical or basolateral domains, some are apically located in one cell type but are basolateral in others. More dramatically, the anion exchanger of a clonal cell line of intercalated cells derived from the kidney can be retargeted from the apical to basolateral domain. This Cl:HCO3 exchanger, kAE1, is an alternately spliced form of the erythroid anion exchanger (AE1, band 3), but unlike band 3 it does not bind ankyrin. Here we identify a new protein (kanadaptin) that binds to the cytoplasmic domain of kAE1in vitro and in vivo but not to the erythroid AE1 or to ankyrin. No significant homologous proteins have been reported so far. Kanadaptin is widely expressed in epithelial (kidney, lung, and liver) and non-epithelial cells (brain and skeletal and cardiac muscle). In kidney, we found by immunocytochemistry that kanadaptin was only expressed in the collecting tubule. In the intercalated cells of this segment, it colocalized with kAE1 in cytoplasmic vesicles but not when the exchanger was in the basolateral membrane. These results raised the possibility that this protein is involved in the targeting of kAE1 vesicles to their final destination.
Footnotes
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↵* This work was supported by a grant from the American Heart Association (New York City Affiliate) (to J. C.) and by National Institutes of Health Grants DK20999 and DK39532 (to Q. A.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
The nucleotide sequence(s) reported in this paper has been submitted to the GenBank™/EMBL Data Bank with accession number(s) AF035526.
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↵¶ To whom correspondence should be addressed: Dept. of Medicine and Physiology, College of Physicians and Surgeons of Columbia University, 630 W. 168th St., New York, NY 10032. Tel.: 212-305-3512; Fax: 212-305-3475; E-mail: qa1{at}columbia.edu.
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↵1 The abbreviations used are: AE1, erythroid anion exchanger or band 3; kAE1, the kidney form of AE1; SH3, Src homology domain 3; GST, glutathione S-transferase; PAGE, polyacrylamide gel electrophoresis; RACE, rapid amplification of cDNA ends; ECM, extracellular matrix.
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- Received October 24, 1997.
- The American Society for Biochemistry and Molecular Biology, Inc.
