The YPLGVG sequence of the Nipah virus matrix protein is required for budding

Abstract

Background: Nipah virus (NiV) is a recently emerged paramyxovirus capable of causing fatal disease in a broad range of mammalian hosts, including humans. Together with Hendra virus (HeV), they comprise the genus Henipavirus in the family Paramyxoviridae. Recombinant expression systems have played a crucial role in studying the cell biology of these Biosafety Level-4 restricted viruses. Henipavirus assembly and budding occurs at the plasma membrane, although the details of this process remain poorly understood. Multivesicular body (MVB) proteins have been found to play a role in the budding of several enveloped viruses, including some paramyxoviruses, and the recruitment of MVB proteins by viral proteins possessing late budding domains (Ldomains) has become an important concept in the viral budding process. Previously we developed a system for producing NiV virus-like particles (VLPs) and demonstrated that the matrix (M) protein possessed an intrinsic budding ability and played a major role in assembly. Here, we have used this system to further explore the budding process by analyzing elements within the M protein that are critical for particle release.

Nipah Virus Entry and Egress from Polarized Epithelial Cells

“…A previous study revealed that NiV M crosses the nucleus, where it becomes monoubiquitinated before it is exported to the cytoplasm and reaches the plasma membrane (14). Surface transport was proposed to depend on ubiquitination and two potential late (L) domain motifs in the M protein, although the exact transport route is not yet known (12)(13)(14). Our finding that M accumulated at apical membranes suggests that the NiV M protein is targeted apically via a robust transport machinery that is not affected by virus-mediated cytopathic effects.…”

“…M organizes the assembly of cytoplasmic nucleocapsids and surface glycoproteins at the plasma membrane and is thus needed for efficient release of progeny virus. Conclusive evidence has been provided that late-domain-like motifs and ubiquitin-regulated nuclear-cytoplasmic trafficking are required for NiV M-mediated budding processes (12)(13)(14).…”

Nipah Virus Matrix Protein Influences Fusogenicity and Is Essential for Particle Infectivity and Stability

“…Trafficking of NiV M is a complex process involving transit through the nucleus (15)(16)(17)(18), despite replication occurring exclusively in the cytoplasm. When NiV M protein nuclear localization or export signals are interrupted, or if the endosomal sorting complexes required for transport (ESCRT) pathway-interacting late domains are disrupted, NiV M proteins lose their ability to accumulate at the plasma membrane and no longer generate virus-like particles (12,17,19). Aside from the M protein, the NiV glycoproteins appear to also possess intrinsic budding capabilities (13), but their roles in viral egress remain unresolved.…”

The Conserved YAGL Motif in Human Metapneumovirus Is Required for Higher-Order Cellular Assemblies of the Matrix Protein and for Virion Production

“…For example, the purified M protein of SeV is able to selfassemble in vitro into tubes and sheets (30). Similarly, expression of the M protein of NiV with no additional viral proteins results in the formation of cellular filaments, while specific mutations in this M protein disrupt these filamentous structures (52). Once assembled, the virion has to bud through the plasma membrane to exit the infected cell, and M proteins play a role in this step as well.…”

“…This was demonstrated for M proteins derived from several paramyxoviruses, including human parainfluenza virus type 1 (hPIV1) (13), Sendai virus (SeV) (78), Nipah virus (NiV) (10,52), Newcastle disease virus (NDV) (49), and measles virus (56,67). Yet for other paramyxoviruses, expression of the M protein is necessary but insufficient for VLP production, and the presence of additional viral proteins is required.…”