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Electrostatic Interactions between Hendra Virus Matrix Proteins Are Required for Efficient Virus-Like-Particle Assembly.

ABSTRACT: Hendra virus (HeV) is a zoonotic paramyxovirus belonging to the genus Henipavirus HeV is highly pathogenic, and it can cause severe neurological and respiratory illnesses in both humans and animals, with an extremely high mortality rate of up to 70%. Among the genes that HeV encodes, the matrix (M) protein forms an integral part of the virion structure and plays critical roles in coordinating viral assembly and budding. Nevertheless, the molecular mechanism of this process is not fully elucidated. Here, we determined the crystal structure of HeV M to 2.5-Å resolution. The dimeric structural configuration of HeV M is similar to that of Newcastle disease virus (NDV) M and is fundamental to protein stability and effective virus-like-particle (VLP) formation. Analysis of the crystal packing revealed a notable interface between the ?1 and ?2 helices of neighboring HeV M dimers, with key residues sharing degrees of sequence conservation among henipavirus M proteins. Structurally, a network of electrostatic interactions dominates the ?1-?2 interactions, involving residues Arg57 from the ?1 helix and Asp105 and Glu108 from the ?2 helix. The disruption of the ?1-?2 interactions using engineered charge reversal substitutions (R57E, R57D, and E108R) resulted in significant reduction or abrogation of VLP production. This phenotype was reversible with an R57E E108R mutant that was designed to partly restore salt bridge contacts. Collectively, our results define and validate previously underappreciated regions of henipavirus M proteins that are crucial for productive VLP assembly.IMPORTANCE Hendra virus is a henipavirus associated with lethal infections in humans. It is classified as a biosafety level 4 (BSL4) agent, and there are currently no preventive or therapeutic treatments available against HeV. Vital to henipavirus pathogenesis, the structural protein M has been implicated in viral assembly and budding, as well as host-virus interactions. However, there is no structural information available for henipavirus M, and the basis of M-driven viral assembly is not fully elucidated. We demonstrate the first three-dimensional structure of a henipavirus M protein. We show the dimeric organization of HeV M as a basic unit for higher-order oligomerization. Additionally, we define key regions/residues of HeV M that are required for productive virus-like-particle formation. These findings provide the first insight into the mechanism of M-driven assembly in henipavirus.

SUBMITTER: Liu YC

PROVIDER: S-EPMC6002731 | biostudies-literature | 2018 Jul

REPOSITORIES: biostudies-literature

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Electrostatic Interactions between Hendra Virus Matrix Proteins Are Required for Efficient Virus-Like-Particle Assembly.

Liu Yu Chih YC Grusovin Julian J Adams Timothy E TE

Journal of virology 20180613 13

<i>Hendra virus</i> (HeV) is a zoonotic paramyxovirus belonging to the genus <i>Henipavirus</i> HeV is highly pathogenic, and it can cause severe neurological and respiratory illnesses in both humans and animals, with an extremely high mortality rate of up to 70%. Among the genes that HeV encodes, the matrix (M) protein forms an integral part of the virion structure and plays critical roles in coordinating viral assembly and budding. Nevertheless, the molecular mechanism of this process is not f ...[more]

PMID: 29695428

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Project description:Late in the HIV-1 replication cycle, the viral structural protein Gag is targeted to virus assembly sites at the plasma membrane of infected cells. The capsid (CA) domain of Gag plays a critical role in the formation of the hexameric Gag lattice in the immature virion, and, during particle release, CA is cleaved from the Gag precursor by the viral protease and forms the conical core of the mature virion. A highly conserved Pro-Pro-Ile-Pro (PPIP) motif (CA residues 122 to 125) [PPIP(122-125)] in a loop connecting CA helices 6 and 7 resides at a 3-fold axis formed by neighboring hexamers in the immature Gag lattice. In this study, we characterized the role of this PPIP(122-125) loop in HIV-1 assembly and maturation. While mutations P123A and P125A were relatively well tolerated, mutation of P122 and I124 significantly impaired virus release, caused Gag processing defects, and abolished infectivity. X-ray crystallography indicated that the P122A and I124A mutations induce subtle changes in the structure of the mature CA lattice which were permissive for in vitro assembly of CA tubes. Transmission electron microscopy and cryo-electron tomography demonstrated that the P122A and I124A mutations induce severe structural defects in the immature Gag lattice and abrogate conical core formation. Propagation of the P122A and I124A mutants in T-cell lines led to the selection of compensatory mutations within CA. Our findings demonstrate that the CA PPIP(122-125) loop comprises a structural element critical for the formation of the immature Gag lattice.IMPORTANCE Capsid (CA) plays multiple roles in the HIV-1 replication cycle. CA-CA domain interactions are responsible for multimerization of the Gag polyprotein at virus assembly sites, and in the mature virion, CA monomers assemble into a conical core that encapsidates the viral RNA genome. Multiple CA regions that contribute to the assembly and release of HIV-1 particles have been mapped and investigated. Here, we identified and characterized a Pro-rich loop in CA that is important for the formation of the immature Gag lattice. Changes in this region disrupt viral production and abrogate the formation of infectious, mature virions. Propagation of the mutants in culture led to the selection of second-site compensatory mutations within CA. These results expand our knowledge of the assembly and maturation steps in the viral replication cycle and may be relevant for development of antiviral drugs targeting CA.

Dataset Information

Electrostatic Interactions between Hendra Virus Matrix Proteins Are Required for Efficient Virus-Like-Particle Assembly.

Publications

Electrostatic Interactions between Hendra Virus Matrix Proteins Are Required for Efficient Virus-Like-Particle Assembly.

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