Research

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

Jared R Patch^1,4 , Ziying Han^2,5 , Sarah E McCarthy^2,6 , Lianying Yan¹ , Lin-Fa Wang³ , Ronald N Harty² and Christopher C Broder¹

¹  Department of Microbiology and Immunology, Uniformed Services University, Bethesda, Maryland 20814, USA

²  Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, 3800 Spruce St, Philadelphia, PA 19104-6049, USA

³  CSIRO Livestock Industries, Australian Animal Health Laboratory, Geelong, Victoria 3220, Australia

⁴  Plum Island Animal Disease Center, Agricultural Research Service, USDA, Greenport, NY 11944, USA

⁵  Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111-2497, USA

⁶  United States Army Research Institute of Infectious Diseases, Virology Division, 1425 Porter Street, Fort Detrick, MD 21702, USA

author email corresponding author email

Virology Journal 2008, 5:137doi:10.1186/1743-422X-5-137

Published:	10 November 2008

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 (L-domains) 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.

Results

Using rationally targeted site-directed mutagenesis we show that a NiV M sequence YPLGVG is required for M budding and that mutation or deletion of the sequence abrogates budding ability. Replacement of the native and overlapping Ebola VP40 L-domains with the NiV sequence failed to rescue VP40 budding; however, it did induce the cellular morphology of extensive filamentous projection consistent with wild-type VP40-expressing cells. Cells expressing wild-type NiV M also displayed this morphology, which was dependent on the YPLGVG sequence, and deletion of the sequence also resulted in nuclear localization of M. Dominant-negative VPS4 proteins had no effect on NiV M budding, suggesting that unlike other viruses such as Ebola, NiV M accomplishes budding independent of MVB cellular proteins.

Conclusion

These data indicate that the YPLGVG motif within the NiV M protein plays an important role in M budding; however, involvement of any specific components of the cellular MVB sorting pathway in henipavirus budding remains to be demonstrated. Further investigation of henipavirus assembly and budding may yet reveal a novel mechanism(s) of viral assembly and release that could be applicable to other enveloped viruses or have therapeutic implications.