Two elements target SIV Nef to the AP-2 clathrin adaptor complex, but only one is required for the induction of CD4 endocytosis.
The simian immunodeficiency virus (SIV) and human immunodeficiency virus type 1 (HIV-1) Nef proteins induce the endocytosis of CD4 and class I MHC molecules. Here we show that SIV Nef interacts with the AP-2 adaptor complex via two elements located in the N-terminal region of the Nef molecule, but only the N-distal element is required to induce CD4 endocytosis. This N-distal AP-2 targeting element contains no canonical endocytic signals and probably contacts the AP-2 complex via a novel interaction surface. The data support a model where SIV Nef induces CD4 endocytosis by promoting the normal interactions between the di-leucine sorting signal in the CD4 cytoplasmic domain and AP-2, but does not substitute for the CD4-AP-2 adaptor interaction. Neither element is important for the induction of class I MHC endocytosis, thus indicating that different mechanisms underlie the induction of class I MHC and CD4 endocytosis by Nef. In contrast to SIV Nef, HIV-1 Nef interacts with AP-2 via a surface containing a di-leucine endocytosis signal in the C-terminal disordered loop of Nef. The fact that genetic selection maintains similar molecular interactions via different surfaces in SIV and HIV-1 Nef proteins indicates that these interactions have critical roles for the viral life cycle in vivo.
D033942:Adaptor Proteins, Vesicular Transport; D000595:Amino Acid Sequence; D001483:Base Sequence; D015704:CD4 Antigens / Q000378:metabolism; D002966:Clathrin / Q000378:metabolism; D015536:Down-Regulation; D004705:Endocytosis; D005347:Fibroblasts; D015693:Gene Products, nef / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D049452:Green Fluorescent Proteins; D015497:HIV-1 / Q000378:metabolism; D015395:Histocompatibility Antigens Class I / Q000276:immunology / Q000378:metabolism; D006801:Humans; D019169:Jurkat Cells; D008164:Luminescent Proteins; D008969:Molecular Sequence Data; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism*; D011485:Protein Binding; D011993:Recombinant Fusion Proteins / Q000235:genetics; D015302:Simian Immunodeficiency Virus / Q000378:metabolism*; D014443:Tyrosine / Q000235:genetics; D054311:nef Gene Products, Human Immunodeficiency Virus