The Clathrin Adaptor Complex AP-1 Binds HIV-1 and MLV Gag and Facilitates Their Budding

Abstract

Retroviral assembly is driven by Gag, and nascent viral particles escape cells by recruiting the machinery that forms intralumenal vesicles of multivesicular bodies. In this study, we show that the clathrin adaptor complex AP-1 is involved in retroviral release. The absence of AP-1mu obtained by genetic knock-out or by RNA interference reduces budding of murine leukemia virus (MLV) and HIV-1, leading to a delay of viral propagation in cell culture. In contrast, overexpression of AP-1mu enhances release of HIV-1 Gag. We show that the AP-1 complex facilitates retroviral budding through a direct interaction between the matrix and AP-1mu. Less MLV Gag is found associated with late endosomes in cells lacking AP-1, and our results suggest that AP-1 and AP-3 could function on the same pathway that leads to Gag release. In addition, we find that AP-1 interacts with Tsg101 and Nedd4.1, two cellular proteins known to be involved in HIV-1 and MLV budding. We propose that AP-1 promotes Gag release by transporting it to intracellular sites of active budding, and/or by facilitating its interactions with other cellular partners.

Endosomal Trafficking of HIV-1 Gag and Genomic RNAs Regulates Viral Egress

“…This conformational change can be induced by the binding of phosphatidylinositol 4,5-bisphosphate, which is mainly localized at the plasma membrane, but also by the multimerization of Gag on the RNA (66,68,69). Furthermore, several endosomal proteins like TIP47 and AP-1 bind MA (70,71) and could thus potentially induce the myristoyl switch in proximity to endosomal membranes.…”

Solution Structure of Calmodulin Bound to the Binding Domain of the HIV-1 Matrix Protein

“…NMR Spectroscopy-Isotopically unlabeled and uniformly 13 ) 2 ) 0.5 , where ⌬␦ X is a chemical shift change of nucleus X. 1 H, 13 C, and 15 N chemical shifts were referenced to 2,2-dimethyl-2-silapentanesulfonic acid (69).…”

“…1 H, 13 C, and 15 N chemical shifts were referenced to 2,2-dimethyl-2-silapentanesulfonic acid (69).…”

“…Several cellular proteins have been implicated in Gag intracellular trafficking, virus assembly, and Gagenvelope co-localization. These include the human adaptor protein complexes 1, 2, and 3 (13)(14)(15), tail interacting protein (16), Golgi-localized ␥-ear containing Arf-binding protein (17,18), ADP-ribosylation factor (17), the suppressor of cytokine signaling 1 (19,20), Lck (a lymphoid specific Src kinase) (21), N-ethylmaleimide-sensitive factor attachment protein receptor (22), Filamin A (23), vacuolar protein sorting-associated protein 18 (24), Mon2 (24), and Lyric (25). The majority of these proteins have been shown to play roles in Gag intracellular trafficking and/or assembly.…”

Properties and functions of the nucleocapsid protein in virus assembly

“…Gag trafficking is dependent upon host cell factors interacting mainly with the MA domain. Briefly, Gag can interact with the adaptor proteins AP1, AP2, AP3 or GGA and Arf proteins [103][104][105][106] and the inhibition or overexpression of these factors impair viral assembly by disrupting the endosomal sorting pathway. NC does not appear to have a definite role in Gag trafficking to the plasma membrane as total deletion of the NC domain of Gag does not prevent some Gag molecules from reaching the plasma membrane but they are deficient in Gag-Gag multimerization and viral assembly.…”