Membrane fusion, mediated by viral spike glycoproteins, is a key process in the infection cycle of all enveloped human and animal viruses. The overall goal of the proposed research is to understand the structural biology of viral membrane fusion. Although numerous crystal structures of the ectodomains of several enveloped virus spike glycoproteins have been determined over the years, we are only beginning to understand the structural transformations that take place when these proteins interact with membranes and how they drive membranes to fuse. In the previous grant period we have made substantial progress towards elucidating the structures of the fusion domains of influenza virus, human immunodeficiency virus, and Ebola virus in membrane environments. We have further been able to determine structural changes in these fusion domains that are conducive to membrane fusion. Most notably, membrane-bound influenza and Ebola virus fusion domains undergo large conformational changes in response to pH, i.e. there fusion trigger in the endosome. We also found that the conformation of the HIV fusion domain responds critically to cholesterol in the target membrane and that numerous critical mutants in these viral fusion domains affect their fusion function in a fashion that can be predicted by their altered structures. Based on these achievements, we now propose to test (1) the hypothesis that a deeper insertion of the Ebola virus fusion loop through a "clenching of a fist" motion is responsible for Ebola GP2-mediated membrane fusion, (2) the hypothesis that cholesterol and possibly cholesterol-rich lipid domains plays a key role in human immunodeficiency and other virus entry, and (3) the hypothesis that a common membrane perturbation mechanism involving lipid order and bilayer curvature changes underlies membrane fusion promoted by influenza, HIV and Ebola viruses.
Viral infections cause many difficult to cure diseases. One approach to combat viral infections is to find better viral entry inhibitors. This basic science project aims at a better fundamental understanding of how viruses such as influenza, HIV, and Ebola enter cells by membrane fusion. Knowledge gained from this research will help to eventually design new strategies to interrupt the infection cycle of these viruses at the stage of cell entry by membrane fusion. !
|Moissoglu, Konstadinos; Kiessling, Volker; Wan, Chen et al. (2014) Regulation of Rac1 translocation and activation by membrane domains and their boundaries. J Cell Sci 127:2565-76|
|Gregory, Sonia M; Larsson, Per; Nelson, Elizabeth A et al. (2014) Ebolavirus entry requires a compact hydrophobic fist at the tip of the fusion loop. J Virol 88:6636-49|
|Tamm, Lukas K; Lee, Jinwoo; Liang, Binyong (2014) Capturing glimpses of an elusive HIV gp41 prehairpin fusion intermediate. Structure 22:1225-6|
|Tamm, Lukas K (2013) Lateral membrane diffusion corralled. Biophys J 104:1399-400|
|Tamm, Lukas K; Lai, Alex L; Li, Yinling (2007) Combined NMR and EPR spectroscopy to determine structures of viral fusion domains in membranes. Biochim Biophys Acta 1768:3052-60|
|Li, Yinling; Han, Xing; Lai, Alex L et al. (2005) Membrane structures of the hemifusion-inducing fusion peptide mutant G1S and the fusion-blocking mutant G1V of influenza virus hemagglutinin suggest a mechanism for pore opening in membrane fusion. J Virol 79:12065-76|
|Crane, Jonathan M; Tamm, Lukas K (2004) Role of cholesterol in the formation and nature of lipid rafts in planar and spherical model membranes. Biophys J 86:2965-79|
|Li, Yinling; Han, Xing; Tamm, Lukas K (2003) Thermodynamics of fusion peptide-membrane interactions. Biochemistry 42:7245-51|
|Tamm, Lukas K; Abildgaard, Frits; Arora, Ashish et al. (2003) Structure, dynamics and function of the outer membrane protein A (OmpA) and influenza hemagglutinin fusion domain in detergent micelles by solution NMR. FEBS Lett 555:139-43|
|Tamm, Lukas K; Crane, Jonathan; Kiessling, Volker (2003) Membrane fusion: a structural perspective on the interplay of lipids and proteins. Curr Opin Struct Biol 13:453-66|
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