The host cell surface has a diverse repertoire of immune molecules to detect and attack foreign particles, including those introduced upon viral infections. Viruses, in turn, have developed an equally impressive arsenal of methods to evade host defenses, such as hijacking cellular membrane trafficking machinery to downregulate host innate and adaptive immune molecules. For example, HIV removes its primary receptor, CD4, from cellular membranes to avoid interference with viral release and infectivity; it prevents MHC-I from reaching the cell surface to evade immune surveillance by cytotoxic T cells; and it removes the innate host restriction factor BST2 (also known as tetherin) from the cell surface to allow for the efficient release of progeny virions. HIV Vpu, a transmembrane protein, and HIV Nef, a peripheral membrane protein, accomplish these tasks by linking targeted proteins to components of the host protein trafficking machinery, thereby inactivating host defense proteins through mislocalization and degradation. The focus of this proposal is to establish the mechanisms by which Nef and Vpu hijack host membrane trafficking pathways to down regulate the expression of immune molecules at the cell surface. Our approach includes structure determination by X-ray crystallography and single particle electron microscopy. It features novel fusion-protein strategies that allow the investigation of membrane-mediated interactions in aqueous solution. It features cell biologic and virologic validation of the complexes at both the molecular and structural levels. Our work will significantly advance our understanding of a diverse range of host-viral interactions at cellular membranes and identify new antiviral drug-targets. Inhibition of these targets would disable viral modulation of cellular membranes and potentially empower host immunity to more effectively control an HIV infection. Moreover, the experimental systems devised for our research project will provide valuable new tools for the studies of host-pathogen relationships and membrane protein interactions.

Public Health Relevance

The proposed research aims to establish the mechanisms by which the HIV proteins Nef and Vpu subvert the correct cellular localization and expression of host immune molecules. The results obtained should lead to the identification of new antiviral drug-targets that may be exploited to disable HIV's ability to modulate cellular membranes, potentially empowering host immunity to control the infection.

Agency
National Institute of Health (NIH)
Type
Research Project (R01)
Project #
5R01AI102778-05
Application #
9189672
Study Section
AIDS Molecular and Cellular Biology Study Section (AMCB)
Program Officer
Kuo, Lillian S
Project Start
Project End
Budget Start
Budget End
Support Year
5
Fiscal Year
2017
Total Cost
Indirect Cost
Name
Yale University
Department
Biochemistry
Type
Schools of Arts and Sciences
DUNS #
043207562
City
New Haven
State
CT
Country
United States
Zip Code
06520
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Mahiti, Macdonald; Toyoda, Mako; Jia, Xiaofei et al. (2016) Relative Resistance of HLA-B to Downregulation by Naturally Occurring HIV-1 Nef Sequences. MBio 7:e01516-15
Tang, Chenxiang; Ji, Xiaoyun; Wu, Li et al. (2015) Impaired dNTPase activity of SAMHD1 by phosphomimetic mutation of Thr-592. J Biol Chem 290:26352-9
Jia, Xiaofei; Zhao, Qi; Xiong, Yong (2015) HIV suppression by host restriction factors and viral immune evasion. Curr Opin Struct Biol 31:106-14
Jia, Xiaofei; Weber, Erin; Tokarev, Andrey et al. (2014) Structural basis of HIV-1 Vpu-mediated BST2 antagonism via hijacking of the clathrin adaptor protein complex 1. Elife 3:e02362