title: A novel role for a YXXPhi motif in directing the caveolin-dependent sorting of membrane-spanning proteins.
abstract: 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 F(c)RII B2 receptor. Further characterization of the recycling pathway has indicated that the chimera F(c)38-63 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 F(c)38-63 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 F(c)38-63. Mutation of the tyrosine or leucine residues in the cytoplasmic sequence Y(47)VEL of F(c)38-63 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 Y(47)VEL sequence of AE1-4 disrupts this interaction, and blocks the recycling of this transporter from the basolateral membrane to the Golgi. The Y(47)VEL tetrapeptide matches the sequence of a YXXPhi motif, and our results indicate a novel role for this motif in directing caveolin-dependent sorting.
authors.affiliation: Department of Molecular Sciences, University of Tennessee Health Science Center, 858 Madison Avenue, Memphis, TN 38163, USA.
authors.forename: Frank C
authors.initials: FC
authors.lastname: Dorsey
authors.forename: Thangavel
authors.initials: T
authors.lastname: Muthusamy
authors.forename: Michael A
authors.initials: MA
authors.lastname: Whitt
authors.forename: John V
authors.initials: JV
authors.lastname: Cox
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D001457:Anion Exchange Protein 1, Erythrocyte / Q000737:chemistry / Q000378:metabolism*; D015703:Antigens, CD / Q000737:chemistry / Q000378:metabolism; D022461:Caveolins / Q000302:isolation & purification / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D002784:Cholesterol / Q000378:metabolism; D002966:Clathrin / Q000378:metabolism; D004285:Dogs; D034281:Dynamins / Q000378:metabolism; D004705:Endocytosis / Q000502:physiology; D011992:Endosomes / Q000378:metabolism; D006056:Golgi Apparatus / Q000378:metabolism; D021381:Protein Transport; D017452:Receptors, IgG / Q000737:chemistry / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism
chemical_list: D001457:Anion Exchange Protein 1, Erythrocyte; D015703:Antigens, CD; D022461:Caveolins; D002966:Clathrin; C080571:Fc gamma receptor IIB; D017452:Receptors, IgG; D011993:Recombinant Fusion Proteins; D002784:Cholesterol; D034281:Dynamins