Structural analysis of protein-protein interactions involved in pathogenesis and viral replication of Lyssaviruses and Henipaviruses

Protein-protein interactions between viral components and host cell factors play a pivotal
role in the infection, reproduction, pathogenicity, and success of obligate intracellular
parasites. This research delves into two significant viral genera - Lyssavirus and Henipaviruses - with a focus on their molecular mechanisms of pathogenesis and immune evasion.
Rabies, a neurotropic zoonotic disease caused by a virus within the genus Lyssavirus, leads to
devastating neurological disorders with an inevitable fatality. Despite its long-recorded
history, much remains unknown about the protein-protein interactions driving its
pathogenicity and immune evasion. The present study utilizes recombinant protein
technology and macromolecular X-ray crystallography to gain further understanding of
lyssavirus assembly and cellular processes.
One pivotal protein in the pathogenesis of rabies is the rabies virus (RABV) phosphoprotein 3
(P3), which localizes to the host cell nucleus and plays a critical role in innate immune
antagonism. This thesis establishes the structural mechanism of P3 interaction with nuclear
import receptor importin alpha for regulated nucleocytoplasmic transport. Elucidation of the
binding interface of P3 nuclear localization signals (NLSs) with importin alpha revealed rabies
P3 possesses an unusual non-classical NLS and binds to importin alpha with a bipartite NLS in
trans.
Additionally, my research investigates the interaction between the RABV phosphoprotein 1
(P) and the viral nucleoprotein (N) during viral assembly. The study explores the binding
interface of N0P from various RABV strains, uncovering a novel role for phosphorylation in this interaction. The findings also shed light on the N0P interface for Australian bat lyssavirus
(ABLV), providing the first-ever ABLV protein structure. Utilizing the N0P models, structureguided design of synthetic peptides for inhibiting RABV assembly showcases the potential of structural biology in developing novel therapeutics against RABV and other lyssaviruses. Furthermore, my thesis delves into the nucleocytoplasmic trafficking of henipavirus M proteins, critical for viral assembly and type I interferon antagonism. By identifying putative nuclear localization signals (NLSs) in henipavirus M and elucidating their interactions with Impα, my research sheds light on crucial mechanisms of henipavirus M nucleocytoplasmic transport, offering insights into viral pathogenesis and potential therapeutic targets.
In conclusion, the atomic structures of lyssavirus and henipavirus proteins provide essential
insights into viral replication, assembly, and host interactions. This knowledge contributes to
the development of targeted therapies against deadly viral diseases, surpassing current postexposure prophylaxis and palliative care approaches in rabies management. Moreover, this research enhances our understanding of how viruses hijack cellular pathways for survival and pathogenesis, ultimately guiding the development of more effective antiviral strategies.