title: Role of adaptor complex AP-3 in targeting wild-type and mutated CD63 to lysosomes.
abstract: CD63 is a lysosomal membrane protein that belongs to the tetraspanin family. Its carboxyterminal cytoplasmic tail sequence contains the lysosomal targeting motif GYEVM. Strong, tyrosine-dependent interaction of the wild-type carboxyterminal tail of CD63 with the AP-3 adaptor subunit mu 3 was observed using a yeast two-hybrid system. The strength of interaction of mutated tail sequences with mu 3 correlated with the degree of lysosomal localization of similarly mutated human CD63 molecules in stably transfected normal rat kidney cells. Mutated CD63 containing the cytosolic tail sequence GYEVI, which interacted strongly with mu 3 but not at all with mu 2 in the yeast two-hybrid system, localized to lysosomes in transfected normal rat kidney and NIH-3T3 cells. In contrast, it localized to the cell surface in transfected cells of pearl and mocha mice, which have genetic defects in genes encoding subunits of AP-3, but to lysosomes in functionally rescued mocha cells expressing the delta subunit of AP-3. Thus, AP-3 is absolutely required for the delivery of this mutated CD63 to lysosomes. Using this AP-3-dependent mutant of CD63, we have shown that AP-3 functions in membrane traffic from the trans-Golgi network to lysosomes via an intracellular route that appears to bypass early endosomes.
authors.affiliation: University of Cambridge, Department of Clinical Biochemistry, Cambridge Institute for Medical Research, Cambridge, CB2 2XY, United Kingdom.
authors.forename: Brian A
authors.initials: BA
authors.lastname: Rous
authors.forename: Barbara J
authors.initials: BJ
authors.lastname: Reaves
authors.forename: Gudrun
authors.initials: G
authors.lastname: Ihrke
authors.forename: John A G
authors.initials: JA
authors.lastname: Briggs
authors.forename: Sally R
authors.initials: SR
authors.lastname: Gray
authors.forename: David J
authors.initials: DJ
authors.lastname: Stephens
authors.forename: George
authors.initials: G
authors.lastname: Banting
authors.forename: J Paul
authors.initials: JP
authors.lastname: Luzio
mesh_terms: D033963:Adaptor Protein Complex 3 / Q000378:metabolism*; D000818:Animals; D015703:Antigens, CD / Q000235:genetics / Q000378:metabolism*; D000962:Antimalarials / Q000378:metabolism; D016827:CD8 Antigens / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D002469:Cell Separation; D002738:Chloroquine / Q000378:metabolism; D005434:Flow Cytometry; D006801:Humans; D051907:Lysosomal Membrane Proteins; D008247:Lysosomes / Q000378:metabolism*; D010980:Platelet Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D021382:Protein Sorting Signals; D021122:Protein Subunits; D021381:Protein Transport / Q000502:physiology*; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D060149:Tetraspanin 30; D020798:Two-Hybrid System Techniques
chemical_list: D033963:Adaptor Protein Complex 3; D015703:Antigens, CD; D000962:Antimalarials; C554586:CD63 protein, human; D016827:CD8 Antigens; C554587:Cd63 protein, mouse; C554588:Cd63 protein, rat; D051907:Lysosomal Membrane Proteins; D010980:Platelet Membrane Glycoproteins; D021382:Protein Sorting Signals; D021122:Protein Subunits; D011993:Recombinant Fusion Proteins; D060149:Tetraspanin 30; D002738:Chloroquine