title: Defective HIV-1 particle assembly in AP-3-deficient cells derived from patients with Hermansky-Pudlak syndrome type 2.
abstract: Adaptor protein complex 3 (AP-3) is a heterotetramer that is involved in signal-mediated protein sorting to endosomal-lysosomal organelles. AP-3 deficiency in humans, induced by mutations in the AP3B1 gene, which encodes the β3A subunit of the AP-3 complex, results in Hermansky-Pudlak syndrome 2 (HPS2), which is a rare genetic disorder with defective lysosome-related organelles. In a previous study, we identified the AP-3 complex as an important contributor to HIV-1 assembly and release. We hypothesized that cells from patients affected by HPS2 should demonstrate abnormalities of HIV-1 assembly. Here we report that HIV-1 particle assembly and release are indeed diminished in HPS2 fibroblast cultures. Transient or stable expression of the full-length wild-type β3A subunit in HPS2 fibroblasts restored the impaired virus assembly and release. In contrast, virus-like particle release mediated by MA-deficient Gag mutants lacking the AP-3 binding site was not altered in HPS2 cells, indicating that the MA domain serves as the major viral determinant required for the recruitment of the AP-3 complex. AP-3 deficiency decreased HIV-1 Gag localization at the plasma membrane and late endosomes and increased the accumulation of HIV-1 Gag at an intermediate step between early and late endosomes. Blockage of the clathrin-mediated endocytic pathway in HPS2 cells did not reverse the inhibited virus assembly and release imposed by the AP-3 deficiency. These results demonstrate that the intact and stable AP-3 complex is required for HIV-1 assembly and release, and the involvement of the AP-3 complex in late stages of the HIV-1 replication cycle is independent of clathrin-mediated endocytosis.
authors.affiliation: Department of Microbiology and Immunology and Center for AIDS Health Disparities Research, Meharry Medical College, Nashville, Tennessee, USA.
authors.forename: Ling
authors.initials: L
authors.lastname: Liu
authors.forename: Jessica
authors.initials: J
authors.lastname: Sutton
authors.forename: Elvin
authors.initials: E
authors.lastname: Woodruff
authors.forename: Fernando
authors.initials: F
authors.lastname: Villalta
authors.forename: Paul
authors.initials: P
authors.lastname: Spearman
authors.forename: Xinhong
authors.initials: X
authors.lastname: Dong
mesh_terms: D033963:Adaptor Protein Complex 3 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D033981:Adaptor Protein Complex delta Subunits / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism / Q000821:virology; D002478:Cells, Cultured; D002966:Clathrin / Q000037:antagonists & inhibitors; D004705:Endocytosis; D005347:Fibroblasts / Q000821:virology; D015497:HIV-1 / Q000378:metabolism / Q000502:physiology*; D022861:Hermanski-Pudlak Syndrome / Q000235:genetics / Q000378:metabolism / Q000821:virology; D006801:Humans; D009154:Mutation; D015398:Signal Transduction; D012867:Skin / Q000821:virology; D019065:Virus Assembly; D057074:Virus Release / Q000235:genetics; D054301:gag Gene Products, Human Immunodeficiency Virus / Q000235:genetics / Q000378:metabolism*
chemical_list: C491904:AP3D1 protein, human; D033963:Adaptor Protein Complex 3; D033981:Adaptor Protein Complex delta Subunits; D002966:Clathrin; D054301:gag Gene Products, Human Immunodeficiency Virus