title: Intracellular trafficking of variant chicken kidney AE1 anion exchangers: role Of alternative NH(2) termini in polarized sorting and Golgi recycling.
abstract: The variant chicken kidney AE1 anion exchangers differ only at the NH(2) terminus of their cytoplasmic domains. Transfection studies have indicated that the variant chicken AE1-4 anion exchanger accumulates in the basolateral membrane of polarized MDCK kidney epithelial cells, while the AE1-3 variant, which lacks the NH(2)-terminal 63 amino acids of AE1-4, primarily accumulates in the apical membrane. Mutagenesis studies have shown that the basolateral accumulation of AE1-4 is dependent upon two tyrosine residues at amino acids 44 and 47 of the polypeptide. Interestingly, either of these tyrosines is sufficient to direct efficient basolateral sorting of AE1-4. However, in the absence of both tyrosine residues, AE1-4 accumulates in the apical membrane of MDCK cells. Pulse-chase studies have shown that after delivery to the cell surface, newly synthesized AE1-4 is recycled to the Golgi where it acquires additional N-linked sugar modifications. This Golgi recycling activity is dependent upon the same cytoplasmic tyrosine residues that are required for the basolateral sorting of this variant transporter. Furthermore, mutants of AE1-4 that are defective in Golgi recycling are unable to associate with the detergent insoluble actin cytoskeleton and are rapidly turned over. These studies, which represent the first description of tyrosine-dependent cytoplasmic sorting signal for a type III membrane protein, have suggested a critical role for the actin cytoskeleton in regulating AE1 anion exchanger localization and stability in this epithelial cell type.
authors.affiliation: Department of Microbiology and Immunology, University of Tennessee Health Science Center, 858 Madison Avenue, Memphis, Tennessee 38163, USA.
authors.forename: T L
authors.initials: TL
authors.lastname: Adair-Kirk
authors.forename: K H
authors.initials: KH
authors.lastname: Cox
authors.forename: J V
authors.initials: JV
authors.lastname: Cox
mesh_terms: D000199:Actins / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D017920:Antiporters / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D016764:Cell Polarity; D002642:Chick Embryo; D003599:Cytoskeleton / Q000737:chemistry / Q000378:metabolism; D003902:Detergents / Q000494:pharmacology; D004285:Dogs; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism; D014644:Genetic Variation / Q000235:genetics*; D006031:Glycosylation; D006056:Golgi Apparatus / Q000378:metabolism*; D007685:Kidney Tubules, Collecting / Q000166:cytology* / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009154:Mutation / Q000235:genetics; D012995:Solubility / Q000187:drug effects; D014443:Tyrosine / Q000235:genetics / Q000378:metabolism
chemical_list: D000199:Actins; D017920:Antiporters; D003902:Detergents; D008565:Membrane Proteins; D014443:Tyrosine