Nef-induced CD4 downregulation: a diacidic sequence in human immunodeficiency virus type 1 Nef does not function as a protein sorting motif through direct binding to beta-COP.
The Nef protein from the human immunodeficiency virus (HIV) induces CD4 cell surface downregulation by interfering with the endocytic machinery. It has been recently proposed that binding of HIV type 1 Nef to the beta subunit of COPI coatomers participated in the Nef-induced CD4 downregulation through recognition of a novel diacidic motif found in the C-terminal disordered loop of Nef (V. Piguet, F. Gu, M. Foti, N. Demaurex, J. Gruenberg, J. L. Carpentier, and D. Trono, Cell 97:63-73, 1999). We have mutated the glutamate residues which formed this motif in order to document this observation. Surprisingly, mutation of the diacidic sequence of Nef did not significantly affect its ability (i) to interact with beta-COP, (ii) to downregulate CD4 cell surface expression, and (iii) to address an integral resident membrane protein containing Nef as the cytoplasmic domain to the endocytic pathway. Our results indicate that these acidic residues are not involved in the connection of Nef with the endocytic machinery through binding to beta-COP. Additional studies are thus required to characterize the residues of Nef involved in the binding to beta-COP and to evaluate the contribution of this interaction to the Nef-induced perturbations of membrane trafficking.
Janvier
K
K
Institut Cochin de Génétique Moléculaire, INSERM U529, Université Paris V, Paris, France.
Craig
H
H
Le Gall
S
S
Benarous
R
R
Guatelli
J
J
Schwartz
O
O
Benichou
S
S
D033982:Adaptor Protein Complex gamma Subunits; D020816:Amino Acid Motifs; D019943:Amino Acid Substitution; D001692:Biological Transport; D015704:CD4 Antigens / Q000235:genetics / Q000378:metabolism*; D016827:CD8 Antigens / Q000235:genetics / Q000378:metabolism; D020756:Coatomer Protein / Q000378:metabolism*; D015536:Down-Regulation; D004705:Endocytosis; D015693:Gene Products, nef / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D018698:Glutamic Acid / Q000235:genetics / Q000378:metabolism*; D015497:HIV-1 / Q000235:genetics; D006367:HeLa Cells; D006801:Humans; D046911:Macromolecular Substances; D008565:Membrane Proteins / Q000378:metabolism; D009154:Mutation; D011485:Protein Binding; D011993:Recombinant Fusion Proteins; D015203:Reproducibility of Results; D020798:Two-Hybrid System Techniques; D054311:nef Gene Products, Human Immunodeficiency Virus
D033982:Adaptor Protein Complex gamma Subunits; D015704:CD4 Antigens; D016827:CD8 Antigens; D020756:Coatomer Protein; D015693:Gene Products, nef; D046911:Macromolecular Substances; D008565:Membrane Proteins; D011993:Recombinant Fusion Proteins; D054311:nef Gene Products, Human Immunodeficiency Virus; D018698:Glutamic Acid