title: Identification of amino acids within the second alpha helical domain of the human immunodeficiency virus type 1 Vpu that are critical for preventing CD4 cell surface expression.
abstract: Human immunodeficiency virus type 1 (HIV-1) encodes for a Vpu protein, which interacts with CD4 resulting in its degradation. In this study, we examined the role of the 10 amino acids within the predicted second alpha-helical domain of the subtype B Vpu cytoplasmic tail in CD4 down-modulation using a VpuEGFP reporter system. Our findings indicate that the invariant leucine at position 63 and, to a lesser extent, the valine at position 68 were required for CD4 down-modulation. Mutation of analogous L63 in Vpu proteins subtypes A2, B(YU-2), C, D, and H also abolished CD4 down-modulation from the cell surface. Co-immunoprecipitation analysis revealed that L63A and V68A mutants were capable of binding CD4 and still retained the ability to interact with h-beta-TrCP1. Taken together, these results indicate that amino acid substitutions in the second alpha-helical domain that retain the predicted structure and binding to h-beta-TrCP1 can influence Vpu-mediated CD4 degradation.
authors: Department of Microbiology, Molecular Genetics and Immunology, University of Kansas Medical Center, Kansas City, Kansas 66160, USA.
authors: M Sarah
authors: MS
authors: Hill
authors: Autumn
authors: A
authors: Ruiz
authors: Kimberly
authors: K
authors: Schmitt
authors: Edward B
authors: EB
authors: Stephens
mesh_terms: D000596:Amino Acids / Q000235:genetics*; D019677:Artificial Gene Fusion; D015496:CD4-Positive T-Lymphocytes / Q000821:virology*; D002460:Cell Line; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D015497:HIV-1 / Q000235:genetics / Q000276:immunology*; D054298:Human Immunodeficiency Virus Proteins / Q000235:genetics / Q000276:immunology*; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000276:immunology*; D016297:Mutagenesis, Site-Directed; D017434:Protein Structure, Tertiary; D054334:Viral Regulatory and Accessory Proteins / Q000235:genetics / Q000276:immunology*; D000086082:Viroporin Proteins
chemical_list: D000596:Amino Acids; D049452:Green Fluorescent Proteins; D054298:Human Immunodeficiency Virus Proteins; D008565:Membrane Proteins; D054334:Viral Regulatory and Accessory Proteins; C485184:enhanced green fluorescent protein; C514859:vpu protein, Human immunodeficiency virus 1; D000086082:Viroporin Proteins