2009 — 2013 |
Schmitt, Anthony P [⬀] |
U54Activity Code Description: To support any part of the full range of research and development from very basic to clinical; may involve ancillary supportive activities such as protracted patient care necessary to the primary research or R&D effort. The spectrum of activities comprises a multidisciplinary attack on a specific disease entity or biomedical problem area. These differ from program project in that they are usually developed in response to an announcement of the programmatic needs of an Institute or Division and subsequently receive continuous attention from its staff. Centers may also serve as regional or national resources for special research purposes, with funding component staff helping to identify appropriate priority needs. |
Characterization and Disruption of Host Protein Interations Required For Budding @ University of Maryland Baltimore
Enveloped viruses are formed by a budding process that often requires participation of host proteins. Retroviruses, rhabdoviruses, and filoviruses all use similar late domain sequences within the viral proteins to recruit host factors for budding. Although paramyxoviruses generally lack the same late domain sequences used by these viruses, we have obtained evidence that paramyxoviruses, similar to other enveloped viruses, likely recruit host factors for budding. The viral protein:host protein binding interfaces used during virus budding have the potential to be effective as targets for antiviral drug design. Hendra and Nipah viruses (Henipaviruses) are recently emerged, zoonotic paramyxoviruses that are deadly to humans. Although progress has been made in characterizing the entry mechanisms for these viruses, very little is known about mechanisms of Henipavirus budding. We propose to take advantage of our expertise in the field of paramyxovirus budding by conducting experiments with the following aims: 1. Define requirements for Henipavirus particle production. We have established virus-like particle (VLP) assembly systems for Hendra and Nipah virus. We will define which Henipavirus proteins are important for VLP production, and hence which proteins may play roles in the recruitment of host factors for budding. 2. Identify host factors involved in Henipavirus budding. Two independent strategies will be employed: co-affinity purification of host proteins from Henipavirus VLPs, and yeast two-hybrid screening. An siRNAbased secondary screen will determine which candidate binding proteins are actually important for budding. 3. Define host and viral targets for antiviral drug development. Binding interfaces between viral and host proteins will be mapped. Minimal binding fragments of host proteins will be tested for the ability to block virus budding, similar to the effect analogous fragments have on retrovirus and parainfluenza virus 5 (PIV5) budding.
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0.902 |
2014 — 2015 |
Dutch, Rebecca E. [⬀] Schmitt, Anthony P (co-PI) [⬀] |
R21Activity Code Description: To encourage the development of new research activities in categorical program areas. (Support generally is restricted in level of support and in time.) |
Hendra Virus Trafficking and Assembly
DESCRIPTION (provided by applicant): Hendra virus (HeV) and Nipah virus, members of the Henipavirus genus of the paramyxovirus family, are zoonotic viruses with high mortality rates in humans. Henipavirus particle assembly is coordinated by the viral matrix (M) proteins, which link together the viral glycoproteins and the viral ribonucleoproteins. The Dutch lab recently defined a novel mechanism for proteolytic cleavage of the Henipavirus fusion (F) proteins. In contrast to other paramyxovirus F proteins, Henipavirus F proteins reach the cell surface in the inactive, uncleaved form, are endocytosed from the plasma membrane (PM), and encounter cathepsin proteases within early endosomes (EEs). Following cathepsin cleavage, F is routed through Rab11-containing recycling endosomes (REs) before returning to the PM for incorporation into budding virus particles. The Schmitt lab recently identified interactions between Henipavirus matrix (M) proteins and the beta subunit of AP-3 adapter complexes which are involved in endosomal trafficking. M protein localized in Rab11 compartments, and this localization was disrupted upon expression of M- binding AP3B1-derived inhibitory polypeptides. To explore the significance of M and F protein convergence in Rab11-positive REs, the Dutch and Schmitt labs have now combined their efforts and discovered that an F mutant defective in endocytic trafficking fails to participate in VLP assembly, and that introduction of a dominant negative Rab11 protein dramatically inhibits Hendra VLP production. We therefore hypothesize that Rab-11 containing endosomal compartments serve as a critical assembly site for key viral proteins prior to viral budding. In Aim 1, we will examine the role of HeV virus F protein trafficking in vius assembly, through use of a comprehensive set of trafficking-altered F protein mutants, and will analyze F- M interactions in Rab11 REs using a sensitive proximity ligation assay. Our second aim will build on the exciting preliminary data defining an interaction between HeV M protein and the beta subunit of the AP-3 adapter complex, examining the role of this interaction in M trafficking, delineating the trafficking pathway, and examining the role of this interaction in apial targeting of the HeV M protein. Finally, in Aim 3 we will address the role of HeV G protein interactions with M or F on G assembly, testing the hypothesis that G protein assembly into VLPs is mediated by redundant interactions with M and F proteins. These experiments will provide critical new information on HeV assembly, and test the novel hypothesis that Rab11 REs may serve as viral assembly sites. If this hypothesis is correct, Rab11 RE components involved in membrane bending may serve as novel host factors for non-ESCRT mediated budding.
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0.919 |