title: Kanadaptin is a protein that interacts with the kidney but not the erythroid form of band 3.
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 kAE1 in 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.
authors.affiliation: Department of Medicine and Physiology, College of Physicians and Surgeons of Columbia University, New York, New York 10032, USA.
authors.forename: J
authors.initials: J
authors.lastname: Chen
authors.forename: S
authors.initials: S
authors.lastname: Vijayakumar
authors.forename: X
authors.initials: X
authors.lastname: Li
authors.forename: Q
authors.initials: Q
authors.lastname: Al-Awqati
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001457:Anion Exchange Protein 1, Erythrocyte / Q000378:metabolism*; D017920:Antiporters; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005982:Glutathione Transferase / Q000235:genetics / Q000378:metabolism; D007150:Immunohistochemistry; D007668:Kidney / Q000378:metabolism*; D008969:Molecular Sequence Data; D011485:Protein Binding; D011817:Rabbits; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics
chemical_list: D001457:Anion Exchange Protein 1, Erythrocyte; D017920:Antiporters; D002352:Carrier Proteins; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; C110099:SLC4A1AP protein, human; C498437:Slc4a1ap protein, mouse; D005982:Glutathione Transferase