The tyrosine-based lysosomal targeting signal in lamp-1 mediates sorting into Golgi-derived clathrin-coated vesicles.
Diversion of membrane proteins from the trans-Golgi network (TGN) or the plasma membrane into the endosomal system occurs via clathrin-coated vesicles (CCVs). These sorting events may require the interaction of cytosolic domain signals with clathrin adaptor proteins (APs) at the TGN (AP-1) or the plasma membrane (AP-2). While tyrosine- and di-leucine-based signals in several proteins mediate endocytosis via cell surface CCVs, segregation into Golgi-derived CCVs has so far only been documented for the mannose 6-phosphate receptors, where it is thought to require a casein kinase II phosphorylation site adjacent to a di-leucine motif. Although recently tyrosine-based signals have also been shown to interact with the mu chain of AP-1 in vitro, it is not clear if these signals also bind intact AP-1 adaptors, nor if they can mediate sorting of proteins into AP-1 CCVs. Here we show that the cytosolic domain of the lysosomal membrane glycoprotein lamp-1 binds AP-1 and AP-2. Furthermore, lamp-1 is present in AP-1-positive vesicles and tubules in the trans-region on the Golgi complex. AP-1 binding as well as localization to AP-1 CCVs require the presence of the functional tyrosine-based lysosomal targeting signal of lamp-1. These results indicate that lamp-1 can exit the TGN in CCVs and that tyrosine signals can mediate these sorting events.
Institute of Biochemistry, University of Lausanne, Epalinges, Switzerland.
S
S
Höning
J
J
Griffith
H J
HJ
Geuze
W
W
Hunziker
D033965:Adaptor Protein Complex alpha Subunits; D033942:Adaptor Proteins, Vesicular Transport; D000818:Animals; D015703:Antigens, CD / Q000032:analysis / Q000378:metabolism*; D001692:Biological Transport; D001923:Brain Chemistry; D002460:Cell Line; D018699:Coated Vesicles / Q000737:chemistry / Q000378:metabolism*; D003600:Cytosol; D004285:Dogs; D011992:Endosomes / Q000378:metabolism; D006056:Golgi Apparatus / Q000378:metabolism*; D007425:Intracellular Membranes / Q000737:chemistry; D051907:Lysosomal Membrane Proteins; D008247:Lysosomes / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000032:analysis / Q000378:metabolism*; D008565:Membrane Proteins / Q000032:analysis / Q000378:metabolism*; D009154:Mutation; D010455:Peptides / Q000138:chemical synthesis / Q000378:metabolism; D011485:Protein Binding; D013552:Swine; D014443:Tyrosine / Q000502:physiology
D033965:Adaptor Protein Complex alpha Subunits; D033942:Adaptor Proteins, Vesicular Transport; D015703:Antigens, CD; D051907:Lysosomal Membrane Proteins; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D010455:Peptides; D014443:Tyrosine