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Review
. 2017 Sep 29;9(10):279.
doi: 10.3390/v9100279.

Venezuelan Equine Encephalitis Virus Capsid-The Clever Caper

Lindsay Lundberg  1 , Brian Carey  2 , Kylene Kehn-Hall  3
Affiliations
Review

Venezuelan Equine Encephalitis Virus Capsid-The Clever Caper

Lindsay Lundberg et al. Viruses. .

Abstract

Venezuelan equine encephalitis virus (VEEV) is a New World alphavirus that is vectored by mosquitos and cycled in rodents. It can cause disease in equines and humans characterized by a febrile illness that may progress into encephalitis. Like the capsid protein of other viruses, VEEV capsid is an abundant structural protein that binds to the viral RNA and interacts with the membrane-bound glycoproteins. It also has protease activity, allowing cleavage of itself from the growing structural polypeptide during translation. However, VEEV capsid protein has additional nonstructural roles within the host cell functioning as the primary virulence factor for VEEV. VEEV capsid inhibits host transcription and blocks nuclear import in mammalian cells, at least partially due to its complexing with the host CRM1 and importin α/β1 nuclear transport proteins. VEEV capsid also shuttles between the nucleus and cytoplasm and is susceptible to inhibitors of nuclear trafficking, making it a promising antiviral target. Herein, the role of VEEV capsid in viral replication and pathogenesis will be discussed including a comparison to proteins of other alphaviruses.

Keywords: CRM1; VEEV; capsid; eastern equine encephalitis virus; importin; western equine encephalitis virus.

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Conflict of interest statement

The authors declare no conflict of interest. The founding sponsors had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, and in the decision to publish the results.

Figures

Figure 1
Figure 1
Alphavirus replication cycle. Viral entry is initiated via E2 binding to the cellular receptor (1); followed by receptor mediated endocytosis (2); the low pH within the endosome results in a conformation change in E1 and fusion of the viral and endosomal membranes (3); the nucleocapsid is released into the cytoplasm (4) followed by nucleocapsid disassembly releasing the viral genomic RNA (5); genomic RNA is translated to form the replication complex (nsP1–4) (6); which produces minus strand RNA (7); minus strand RNA serves as a template for additional genomic RNA production (8); subgenomic RNA is produced via a promoter within the minus strand RNA (9); the subgenomic RNA encodes for the structural proteins (capsid, pE2, 6K, E1); capsid is translated first (10) followed by autocleavage and translation of the remaining structural proteins on the rough ER (11); the glycoproteins are processed through the secretory pathway (12) and transported to the plasma membrane (13); capsid interacts with genomic RNA to form the nucleocapsid (14) and this complex interacts with E2 protein (15); followed by viral budding (16); capsid is also transported to the nucleus, binds importin α/β and CRM1, and blocks nuclear export (17).
Figure 2
Figure 2
VEEV capsid protein structural layout. The VEEV capsid protein is roughly divided into two terminals, amino (N) and carboxy (C). From there, the N terminal can be further subdivided into four arbitrary subdomains (SD) based on physical structure and function. The C terminal contains the chymotrypsin-life fold, which is responsible for cleaving capsid from the growing structural polyprotein, and a binding pocket that interacts with the viral glycoproteins, contributing to the structure of the virion. The first 126 amino acids are also displayed at the bottom of the figure.
See this image and copyright information in PMC

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