Abstract
The HIV-1 Nef accessory protein is essential for viral pathogenicity and AIDS progression. Nef forms complexes with multiple host cell factors to facilitate viral replication and promote immune escape of HIV-infected cells. Previous X-ray crystal structures demonstrate that Nef forms homodimers, the orientation of which are influenced by host cell binding partners. In cell-based fluorescence complementation assays, Nef forms homodimers at the plasma membrane. However, recombinant Nef proteins often exist as monomers in solution, suggesting that membrane interaction may also trigger monomer to dimer transitions. In this study, we show that monomeric Nef core proteins can be induced to form dimers in the presence of low concentrations of the non-ionic surfactant, β-octyl glucoside (βOG). X-ray crystallography revealed that a single βOG molecule is present in the Nef dimer, with the 8-carbon acyl chain of the ligand binding to a hydrophobic pocket formed by the dimer interface. This Nef-βOG dimer interface involves helix αB, as observed in previous dimer structures, as well as a helix formed by N-terminal residues 54–66. Nef dimer formation is stabilized in solution by the addition of βOG, providing biochemical validation for the crystal structure. These observations together suggest that the interaction with host cell lipid mediators or other hydrophobic ligands may play a role in Nef dimerization, which has been previously linked to multiple Nef functions including host cell protein kinase activation, CD4 downregulation, and enhancement of HIV-1 replication.
Highlights
The nef genes of human and simian immunodeficiency viruses (HIV-1, HIV-2, and SIV) encode accessory proteins of 27–35 kDa critical for viral pathogenesis [1,2]
Structural analyses of Nef and Nef-effector complexes by both NMR spectroscopy and Xray crystallography have identified features critical for its function [20,21,22,23,24,25,26]. These features include an N-terminal flexible region, an acidic cluster (EEEE) and PXXP motif (62–77), a well-ordered core domain (79–206), and a central loop within the core domain (148–180)
The Nef protein used in this study is derived from the HIV-1 B-clade isolate SF2, and consists of residues 51–205
Summary
The nef genes of human and simian immunodeficiency viruses (HIV-1, HIV-2, and SIV) encode accessory proteins of 27–35 kDa critical for viral pathogenesis [1,2]. Targeted expression of Nef alone to the CD4+ cellular compartment is sufficient to induce an AIDS-like syndrome in transgenic mice [6]. Consistent with these observations, some individuals infected with Nef-defective HIV-1 remain asymptomatic for many years in the absence of antiretroviral therapy [7,8]. These studies demonstrate the importance of Nef to HIV-1 pathogenesis in vivo, and support the development of drugs targeting this virulence factor as a new approach to HIV-1 therapy [9]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
