Rotavirus infection of cells in culture induces major changes in Ca(2+) homeostasis. These changes include increases in plasma membrane Ca(2+) permeability, cytosolic Ca(2+) concentration, and total cell Ca(2+) content and a reduction in the amount of Ca(2+) released from intracellular pools sensitive to agonists. Various lines of evidence suggest that the nonstructural glycoprotein NSP4 and po...

A Semliki Forest virus nonstructural polyprotein, P1234, expressed in the yeast Saccharomyces cerevisiae in the absence of a replicative RNA template appeared to be properly cleaved into nsP1 to nsP4. All nsPs were membrane associated, and nsP2 was also transported to the nucleus. The membrane fraction containing nsPs showed guanine-7-methyltransferase and guanylyltransferase-like activities, t...

Semliki Forest virus (SFV) is an arthropod-borne alphavirus that induces membrane invaginations (spherules) in host cells. These harbor the viral replication complexes (RC) that synthesize viral RNA. Alphaviruses have four replicase or nonstructural proteins (nsPs), nsP1-4, expressed as polyprotein P1234. An early RC, which synthesizes minus-strand RNA, is formed by the polyprotein P123 and the...

Coronaviruses are a family of positive-stranded RNA viruses that includes important pathogens of humans and other animals. The large coronavirus genome (26-31 kb) encodes 15-16 nonstructural proteins (nsps) that are derived from two replicase polyproteins by autoproteolytic processing. The nsps assemble into the viral replication-transcription complex and nsp3, nsp4 and nsp6 are believed to anc...

Rotavirus (RV)-infected piglets are presumed to be latent sources of heterologous RV infection in humans and other animals. In RVs, non-structural protein 4 (NSP4) is the major virulence factor with pleiotropic properties. In this study, we analyzed the nsp4 gene from porcine RVs isolated from diarrheic and non-diarrheic cases at different levels of protein folding to explore correlations to di...

The outer shell of the rotavirus triple-layered virion is lost during cell entry, yielding a double-layered particle (DLP) that directs synthesis of viral plus-strand RNAs. The plus-strand RNAs act as templates for synthesis of the segmented double-stranded RNA (dsRNA) genome in viral inclusion bodies (viroplasms). The viral endoplasmic reticulum (ER)-resident glycoprotein NSP4 recruits progeny...

The direct effect of a rotavirus nonstructural glycoprotein, NSP4, and certain related peptides on the sodium-coupled transport of D-glucose and of L-leucine was studied by using intestinal brush border membrane vesicles isolated from young rabbits. Kinetic analyses revealed that the NSP4(114-135) peptide, which causes diarrhea in young rodents, is a specific, fully noncompetitive inhibitor of ...

Nonstructural proteins of Sindbis virus, nsP1, nsP2, nsP3, and nsP4, as well as intermediate polyproteins, are produced from two precursor polyproteins, P123 and P1234, by a proteolytic enzyme encoded in the C-terminal half of nsP2. We studied the requirements for and the functions of the intermediate and mature processing products for Sindbis virus RNA synthesis by using site-directed mutants ...

Rotavirus is the major cause of dehydrating gastroenteritis in children and young animals. NSP4 (non-structural protein 4), a rotaviral non-structural glycoprotein and a peptide NSP4(114-135) (DKLTTREIEQVELLKRIYDKLT), corresponding to NSP4 amino acids 114-135, induce diarrhoeal disease in a neonatal mouse model and interact with model membranes that mimic caveolae. Correlation of the mechanisms...