GSBS Student Publications

Title

Thiol/disulfide exchange is required for membrane fusion directed by the Newcastle disease virus fusion protein

GSBS Program

Biochemistry & Molecular Pharmacology

UMMS Affiliation

Graduate School of Biomedical Sciences; Department of Molecular Genetics and Microbiology

Date

12-8-2006

Document Type

Article

Medical Subject Headings

Animals; Bacitracin; COS Cells; Cercopithecus aethiops; Disulfides; Dithionitrobenzoic Acid; Enzyme Inhibitors; HN Protein; Membrane Fusion; Models, Biological; Newcastle disease virus; Protein Disulfide-Isomerase; Recombinant Proteins; Sulfhydryl Compounds; Viral Fusion Proteins; Virus Attachment

Disciplines

Life Sciences | Medicine and Health Sciences

Abstract

Newcastle disease virus (NDV), an avian paramyxovirus, initiates infection with attachment of the viral hemagglutinin-neuraminidase (HN) protein to sialic acid-containing receptors, followed by fusion of viral and cell membranes, which is mediated by the fusion (F) protein. Like all class 1 viral fusion proteins, the paramyxovirus F protein is thought to undergo dramatic conformational changes upon activation. How the F protein accomplishes extensive conformational rearrangements is unclear. Since several viral fusion proteins undergo disulfide bond rearrangement during entry, we asked if similar rearrangements occur in NDV proteins during entry. We found that inhibitors of cell surface thiol/disulfide isomerase activity--5'5-dithio-bis(2-nitrobenzoic acid) (DTNB), bacitracin, and anti-protein disulfide isomerase antibody--inhibited cell-cell fusion and virus entry but had no effect on cell viability, glycoprotein surface expression, or HN protein attachment or neuraminidase activities. These inhibitors altered the conformation of surface-expressed F protein, as detected by conformation-sensitive antibodies. Using biotin maleimide (MPB), a reagent that binds to free thiols, free thiols were detected on surface-expressed F protein, but not HN protein. The inhibitors DTNB and bacitracin blocked the detection of these free thiols. Furthermore, MPB binding inhibited cell-cell fusion. Taken together, our results suggest that one or several disulfide bonds in cell surface F protein are reduced by the protein disulfide isomerase family of isomerases and that F protein exists as a mixture of oxidized and reduced forms. In the presence of HN protein, only the reduced form may proceed to refold into additional intermediates, leading to the fusion of membranes.

Rights and Permissions

Citation: J Virol. 2007 Mar;81(5):2328-39. Epub 2006 Dec 6. Link to article on publisher's site

Related Resources

Link to article in PubMed

Journal Title

Journal of virology

PubMed ID

17151113