title: CD4 downregulation by the HIV-1 protein Nef reveals distinct roles for the γ1 and γ2 subunits of the AP-1 complex in protein trafficking.
abstract: The HIV accessory protein Nef is a major determinant of viral pathogenesis that facilitates viral particle release, prevents viral antigen presentation and increases infectivity of new virus particles. These functions of Nef involve its ability to remove specific host proteins from the surface of infected cells, including the CD4 receptor. Nef binds to the adaptor protein 2 (AP-2) and CD4 in clathrin-coated pits, forcing CD4 internalization and its subsequent targeting to lysosomes. Herein, we report that this lysosomal targeting requires a variant of AP-1 containing isoform 2 of γ-adaptin (AP1G2, hereafter γ2). Depletion of the γ2 or μ1A (AP1M1) subunits of AP-1, but not of γ1 (AP1G1), precludes Nef-mediated lysosomal degradation of CD4. In γ2-depleted cells, CD4 internalized by Nef accumulates in early endosomes and this alleviates CD4 removal from the cell surface. Depletion of γ2 also hinders EGFR-EGF-complex targeting to lysosomes, an effect that is not observed upon γ1 depletion. Taken together, our data provide evidence that the presence of γ1 or γ2 subunits delineates two distinct variants of AP-1 complexes, with different functions in protein sorting.
authors.affiliation: Department of Cell and Molecular Biology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, São Paulo 14049-900, Brazil.
authors.forename: Lucas A
authors.initials: LA
authors.lastname: Tavares
authors.affiliation: Department of Cell and Molecular Biology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, São Paulo 14049-900, Brazil.
authors.forename: Eulália M L
authors.initials: EM
authors.lastname: da Silva
authors.affiliation: Department of Cell and Molecular Biology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, São Paulo 14049-900, Brazil.
authors.forename: Mara E
authors.initials: ME
authors.lastname: da Silva-Januário
authors.affiliation: Department of Cell and Molecular Biology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, São Paulo 14049-900, Brazil.
authors.forename: Yunan C
authors.initials: YC
authors.lastname: Januário
authors.affiliation: Department of Cell and Molecular Biology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, São Paulo 14049-900, Brazil.
authors.forename: Julianne V
authors.initials: JV
authors.lastname: de Cavalho
authors.affiliation: Department of Cell and Molecular Biology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, São Paulo 14049-900, Brazil.
authors.forename: Érika S
authors.initials: ÉS
authors.lastname: Czernisz
authors.affiliation: Department of Physiology, School of Medicine, and Center for Interdisciplinary Studies of the Nervous System (CISNe), Universidad Austral de Chile, Valdivia 5110566, Chile.
authors.forename: Gonzalo A
authors.initials: GA
authors.lastname: Mardones
authors.affiliation: Department of Cell and Molecular Biology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, São Paulo 14049-900, Brazil lldasilva@fmrp.usp.br.
authors.forename: Luis L P
authors.identifier: 0000-0003-3558-0087
authors.initials: LL
authors.lastname: daSilva
mesh_terms: D033982:Adaptor Protein Complex gamma Subunits / Q000378:metabolism*; D015704:CD4 Antigens / Q000378:metabolism*; D015536:Down-Regulation; D004705:Endocytosis; D056827:Endosomal Sorting Complexes Required for Transport / Q000378:metabolism; D011992:Endosomes / Q000378:metabolism; D004815:Epidermal Growth Factor / Q000378:metabolism; D066246:ErbB Receptors / Q000378:metabolism; D055785:Gene Knockdown Techniques; D049452:Green Fluorescent Proteins / Q000378:metabolism; D015497:HIV-1 / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D008247:Lysosomes / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D011485:Protein Binding; D021381:Protein Transport; D059748:Proteolysis; D020798:Two-Hybrid System Techniques; D054311:nef Gene Products, Human Immunodeficiency Virus / Q000378:metabolism*
chemical_list: D033982:Adaptor Protein Complex gamma Subunits; D015704:CD4 Antigens; D056827:Endosomal Sorting Complexes Required for Transport; D010750:Phosphoproteins; C096164:hepatocyte growth factor-regulated tyrosine kinase substrate; D054311:nef Gene Products, Human Immunodeficiency Virus; C514837:nef protein, Human immunodeficiency virus 1; D049452:Green Fluorescent Proteins; D004815:Epidermal Growth Factor; D066246:ErbB Receptors
keywords: AP1G1; AP1G2; HIV-1; MVB; Nef; Receptor downregulation; γ2-adaptin