Mission

The Center's primary mission is to understand the early cellular events of HIV infection, those that occur after engagement of cell surface receptors and membrane fusion and prior to genome integration (intracellular trafficking, uncoating, restriction, reverse transcription, nuclear import, etc), by determining the high-resolution structures of HIV-host cell protein complexes and through bioinformatics approaches, cellular imaging, RNA knockdown strategies, and stage-specific HIV replication assays. We have established an interdisciplinary Center with several cores dedicated to this mission.

Overview of Center

The HIV cellular infection cycle comprises several distinct steps, and can be divided into early and late events. The early events begin with the virus attaching to the target cell, proceed through entry, and continue until the viral genome integrates into the host chromosome. Late events take place after integration and lead to the release of newly formed virus particles from the infected cell. Research conducted at the PCHPI is focused on a subset of the early events in the HIV infection cycle, those that occur after the virus has fused with the cellular membrane and before the viral genome integrates with the genome of the cell. The path of HIV components and the cytosolic events that occur after membrane fusion, prior to nuclear import, remain a poorly understood area of HIV biology. At the same time, it presents an enormous opportunity for major discoveries.

The HIV genome encodes two envelope proteins, gp41 and gp120; three structural proteins, Matrix (MA), Capsid (CA), and Nucleocapsid (NC), all of which are proteolytically cleaved out of the Gag polyprotein upon virus maturation; three enzymes, Reverse Transcriptase (RT), Integrase (IN), and Protease (PR) that are autocatalytically produced from the Gag-Pol precursor; six accessory/regulatory proteins, Nef (Negative factor), Vpu (Viral protein u), Vif (Viral infectivity factor), Vpr (Viral propagation factor), Tat (Trans-activator of transcription), and Rev (Regulator of viral protein expression); and a few other proteins. The primary aim of the PCHPI is to understand how these HIV proteins interact with the host cell. Elucidating these interactions is crucial for understanding viral replication and pathogenesis. Knowledge of the spatial and temporal details of the intricately interwoven choreography between pathogen and host components will provide an essential foundation for developing focused and effective preventative and therapeutic strategies in the fight against AIDS.

Host-virus interactions are attractive for exploring and developing alternative anti-HIV-1 strategies given that virtually every step of viral replication involves an intricate interplay between the virus and the host machinery. Cellular components have been shown to play pivotal roles in viral replication during entry, reverse transcription, nuclear import, integration, transcription, nuclear export, translation, assembly, and budding. The virus utilizes the host machinery both to promote its replication and, at the same time, to subvert and evade the antiviral responses of the cell. A large numbers of interactions between HIV proteins and host-cell components have been reported in the scientific literature, however structural confirmation of these interactions and/or reliable assessments of their functional importance have been difficult to ascertain. The interdisciplinary Pittsburgh Center for HIV Protein Interactions is dedicated to validating the functional importance of reported interactions and to determining high-resolution structures of HIV proteins and their interacting partners from the human host. Complexes will be structurally characterized using a combination of X-ray crystallography, NMR spectroscopy, and electron microscopy (EM). The PCHPI brings together expertise in each of these three major methodological areas. Furthermore, models and assays to predict and validate the biological significance of putative HIV - host protein interactions are being developed. Results will provide insights into detailed aspects of HIV immediate post-entry biology and it is anticipated that they can be effectively leveraged for developing novel therapeutic strategies.

Please contact the Center Coordinator, Teresa Brosenitsch, with any questions concerning the center.