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© The Rockefeller University Press, 0021-9525/1999//1237 $5.00
The Journal of Cell Biology, Volume 147, Number 6, , 1999 1237-1248

Original Article

Intracellular Trafficking of Variant Chicken Kidney Ae1 Anion Exchangers

: Role of Alternative Nh2 Termini in Polarized Sorting and Golgi Recycling



Tracy L. Adair-Kirka, Kathleen H. Coxa, and John V. Coxa

a Department of Microbiology and Immunology, University of Tennessee Health Science Center, 858 Madison Avenue, Memphis, Tennessee 38163
Department of Microbiology and Immunology, University of Tennessee, 858 Madison Avenue, Memphis, TN 38163.(901) 448-8462(901) 448-7080

jcox{at}utmem1.utmem.edu

The variant chicken kidney AE1 anion exchangers differ only at the NH2 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 NH2-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.

Key Words: epithelial • band 3 protein • Golgi • polarity • actin

© 1999 The Rockefeller University Press

Abbreviations used in this paper: BFA, brefeldin A; endo H, endoglycosidase H.


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