title: Expression of major histocompatibility complex class II molecules in HeLa cells promotes the recruitment of AP-1 Golgi-specific assembly proteins on Golgi membranes.
abstract: The newly synthesized major histocompatibility complex (MHC) class II molecules, an alphabeta dimer associated with the Ii invariant chain, must be targeted to endosomal, lysosomal enzyme-rich compartments in order to bind and present immunogenic peptides. The precise route followed by this complex at the exit of the trans-Golgi network, the last sorting station of the biosynthetic pathway, is poorly understood. We show here that overexpression of alphabetaIi complexes in HeLa cells promotes the first step of clathrin-coat assembly in vitro, that is the ARF-dependent translocation of AP-1 Golgi-specific assembly proteins on membranes. In contrast, alphabeta dimers alone or associated with Ii lacking most of its cytoplasmic domain fail to recruit AP-1. This study strongly suggests that the invariant chain (Ii) is responsible for the AP-1-dependent sorting of the alphabeta dimers in the trans-Golgi network of HeLa cells and that the MHC class II molecules are, like the mannose 6-phosphate receptors, transported directly from this compartment to endosomes via clathrin-coated vesicles.
authors.affiliation: UMR 144 CNRS- Institut Curie, Laboratoire "Mecanismes Moléculaires du Transport Intracellulaire, 12 rue Lhomond, 75005 Paris, France.
authors.forename: J
authors.initials: J
authors.lastname: Salamero
authors.forename: R
authors.initials: R
authors.lastname: Le Borgne
authors.forename: C
authors.initials: C
authors.lastname: Saudrais
authors.forename: B
authors.initials: B
authors.lastname: Goud
authors.forename: B
authors.initials: B
authors.lastname: Hoflack
mesh_terms: D033965:Adaptor Protein Complex alpha Subunits; D033942:Adaptor Proteins, Vesicular Transport; D000595:Amino Acid Sequence; D000944:Antigens, Differentiation, B-Lymphocyte / Q000378:metabolism; D001692:Biological Transport; D002451:Cell Compartmentation; D006056:Golgi Apparatus / Q000378:metabolism*; D006681:HLA-D Antigens / Q000378:metabolism*; D006367:HeLa Cells; D000949:Histocompatibility Antigens Class II / Q000378:metabolism; D006801:Humans; D046911:Macromolecular Substances; D008565:Membrane Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism*; D011485:Protein Binding
chemical_list: D033965:Adaptor Protein Complex alpha Subunits; D033942:Adaptor Proteins, Vesicular Transport; D000944:Antigens, Differentiation, B-Lymphocyte; D006681:HLA-D Antigens; D000949:Histocompatibility Antigens Class II; D046911:Macromolecular Substances; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D010750:Phosphoproteins; C045084:invariant chain