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First published online 10 July 2007
doi: 10.1242/jcs.002493

Journal of Cell Science 120, 2544-2554 (2007)
Published by The Company of Biologists 2007
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Research Article

A novel role for a YXX{Phi} motif in directing the caveolin-dependent sorting of membrane-spanning proteins

Frank C. Dorsey*, Thangavel Muthusamy, Michael A. Whitt and John V. Cox{ddagger}

Department of Molecular Sciences, University of Tennessee Health Science Center, 858 Madison Avenue, Memphis, TN 38163, USA

{ddagger} Author for correspondence (e-mail: jcox{at}utmem.edu)

Accepted 21 May 2007

Previous studies showed that the sequence between amino acids 38 and 63 of the chicken AE1-4 anion exchanger is sufficient to direct basolateral sorting and recycling to the Golgi when fused to a cytoplasmic tailless FcRII B2 receptor. Further characterization of the recycling pathway has indicated that the chimera Fc38-63 colocalizes with caveolin 1 in the basolateral membrane of MDCK cells, and in early endosomes following its internalization from the cell surface. Studies using small interfering RNA (siRNA) and dominant-negative mutants revealed that Fc38-63 endocytosis is primarily caveolin-dependent and clathrin-independent. The endocytosis of the chimera is also dependent upon cholesterol and dynamin. Co-precipitation studies indicated that caveolin 1 associates with Fc38-63. Mutation of the tyrosine or leucine residues in the cytoplasmic sequence Y47VEL of Fc38-63 disrupts this interaction and inhibits the endocytosis of the chimera. Additional analyses revealed that AE1-4 also associates with caveolin 1. Mutation of the leucine in the Y47VEL sequence of AE1-4 disrupts this interaction, and blocks the recycling of this transporter from the basolateral membrane to the Golgi. The Y47VEL tetrapeptide matches the sequence of a YXX{Phi} motif, and our results indicate a novel role for this motif in directing caveolin-dependent sorting.

Key words: Caveolin, Sorting signal, Endosomes, AE1 anion exchanger






© The Company of Biologists Ltd 2007