KECK SCIENCE DEPARTMENT SEMINAR

 

Understanding Nipah Virus, the Deadliest Virus You've Never Heard Of
By
Zeynep Akyol Ataman
Keck Science
 
From: 11:00 AM To: 12:00 PM
On
Thursday, Feb 13, 2014
At
Burns Lecture Hall, Keck Science Center
Nipah (NiV) is a deadly emerging zoonotic virus with a human mortality rate of 40% to ~70%. NiV is classified as a Category C priority pathogen due to its potential as an agent of bioterrorism. Enveloped viruses like NiV bud from the cellular membrane with attachment and fusion glycoproteins. Three types of Paramyxoviral attachment proteins have been identified according to their receptor of interest. NDV uses hemagglutinin-neuraminidase (HN)-protein to bind sialic acid moieties that are present on surface glycoproteins. MV utilizes H-protein to bind the signaling lymphocyte activation molecule (SLAM) as its cellular receptor and only retains the hemagglutinin activity. Finally NiV attachment protein (G) binds to ephrinB2 and ephrinB3 and lacks both HN functions. NiV-G goes through a conformational change upon receptor binding which in turn triggers NiV-F to bring the viral and cellular membranes together. It is important to study membrane proteins in the context of an actual lipid bilayer because protein insertion into the membrane is a requisite for their biochemical and structural integrity. To understand the precise mechanisms of attachment and fusion we need information on these proteins in their native environments. To this end we studied the distribution, stoichiometry and the structural characteristics of the paramyxovirus fusion (F) and attachment proteins (HN, H and G) using cryo- and negative-stain electron tomography to monitor these proteins on NiV-VLPs, MV and NDV particles. Because NiV is a Biosafety level 4 pathogen, we used NiV viral like particles (VLPs) consisting of M, F, and G. VLPs have been successfully used to study viruses like NDV, Mumps, Ebola, Sendai and PiV5. All analyzed particles were pleomorphic consistent with earlier studies. The particles ranged from bald to densely packed with spikes. By making use of MG- and MF-VLPs we were able to identify the attachment and fusion proteins on the particles. Pre-fusion F protein was in the form of parallel-head spikes that displayed triangular outward projections this was consistent with or observations with NDV and MV. Attachment protein was observed in a staggered-head conformation where there was a second layer of projections on the stalk domain below the head region. We did not observe this with NDV or MV. This novel finding, to our knowledge, is only seen with NiV-G and may suggest that the NiV-G stalk region is not a plain alpha-helical structure but has a complex fold to accommodate two head domains as dimers. Surprisingly both with NiV-VLPs and NDV we observed that the G and pre-fusion F-spikes were segregated. This may suggest that the virus membrane goes through a massive rearrangement to bring the F and G proteins together before or during the receptor attachment. We did not observe any G protein spikes on the VLPs with post-fusion F. This could indicate that the virus sheds the G protein during the fusion process to decrease the crowding of the membrane. Our studies will help shed light on Paramyxovirus attachment and fusion.
 
 
Seminar Registered by: Velda Yount

 

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