EHD4 and its role on HIV-1 infection

PROJECT SUMMARY/ABSTRACT Antiretroviral therapies for those infected with human immunodeficiency virus-1 (HIV-1) have been effective in controlling infection however they must be taken for life and have many short-term and long-term side effects. Understanding host-pathogen interactions between cellular and HIV-1 proteins may reveal cellular factors that are involved in viral replication that can serve as targets for the development of novel antiretroviral therapeutics. During virion production, HIV-1 envelope glycoproteins are internalized into early endosomes and recycled to sites of viral assembly at the plasma membrane. Eps15 Homology Domain Protein 4 (EHD4), a cellular protein, known to be involved in endocytic recycling of membrane proteins/receptors, directs internalized proteins at early endosomes to late endosomes for subsequent degradation in lysosomes. However, recent data suggest a novel role for EHD4 as an HIV-1 restriction factor. Preliminary data demonstrate EHD4 decreases HIV-1 particle infectivity and reduces envelope glycoprotein levels (gp41 and gp120) in nascent virions. Furthermore, EHD4 does not affect the surface levels of CD4, CXCR4 and CCR5, thus its effect on HIV-1 infection is not indirect. Finally, we show that gp41 forms a complex with EHD4. While EHD4 is an interferon stimulated gene, nothing is known about its antiviral functions. The objective of this proposal is to determine the mechanism by which EHD4 decreases HIV-1 particle infectivity. The experiments proposed in this research plan will further characterize the antiviral role of EHD4 during HIV-1 infection by 1) determining the mechanism by which EHD4 blocks the incorporation of envelope glycoproteins, gp41 and gp120, in nascent virions, 2) investigating the role of EHD4 found in virions, and 3) elucidating the role of the gp41 cytoplasmic tail on EHD4-mediated restriction of HIV-1. Additionally, experiments performed to characterize the role of EHD4 will include both primary CD4+ T cells and monocyte derived macrophages (MDMs) infected with HIV-1 to reflect infection under physiological conditions. The proposed research will provide essential insight into the role of EHD4 during HIV-1 infection and may identify novel drug targets that lead to improved antiretroviral therapies. Finally, our findings with HIV-1 have the potential of being applicable to other enveloped viruses.