Enhanced fusion pore expansion mediated by the trans-acting Endodomain of the reovirus FAST proteins

• Published in: PLoS pathogens Vol. 5; no. 3; p. e1000331
• Main Authors: Top, Deniz, Barry, Chris, Racine, Trina, Ellis, Chelsey Louise, Duncan, Roy
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 01.03.2009; Public Library of Science (PLoS)
• Subjects: Animals; Biochemistry/Cell Signaling and Trafficking Structures; Biochemistry/Membrane Proteins and Energy Transduction; Biochemistry/Protein Chemistry; Cell Biology/Cell Signaling; Cell Biology/Membranes and Sorting; Cell Line; Cellular biology; Cercopithecus aethiops; Cytoskeleton - metabolism; Flow Cytometry; Genetic aspects; Giant Cells - metabolism; Host-virus relationships; Immunohistochemistry; Medical research; Membrane fusion; Membrane proteins; Membranes; Molecular Biology/Post-Translational Regulation of Gene Expression; Orthoreovirus, Mammalian - genetics; Orthoreovirus, Mammalian - metabolism; Peptide Fragments - genetics; Peptide Fragments - metabolism; Physiological aspects; Protein Structure, Tertiary - genetics; Protein Structure, Tertiary - physiology; Proteins; Reovirus; Signal Transduction; Vero Cells; Viral Fusion Proteins - genetics; Viral Fusion Proteins - metabolism; Virology; Virology/Effects of Virus Infection on Host Gene Expression; Canada
• ISSN: 1553-7374; 1553-7366; 1553-7374
• DOI: 10.1371/journal.ppat.1000331

The reovirus fusion-associated small transmembrane (FAST) proteins are virus-encoded membrane fusion proteins that function as dedicated cell-cell fusogens. The topology of these small, single-pass membrane proteins orients the majority of the protein on the distal side of the membrane (i.e., inside the cell). We now show that ectopic expression of the endodomains of the p10, p14, and p15 FAST proteins enhances syncytiogenesis induced by the full-length FAST proteins, both homotypically and heterotypically. Results further indicate that the 68-residue cytoplasmic endodomain of the p14 FAST protein (1) is endogenously generated from full-length p14 protein expressed in virus-infected or transfected cells; (2) enhances syncytiogenesis subsequent to stable pore formation; (3) increases the syncytiogenic activity of heterologous fusion proteins, including the differentiation-dependent fusion of murine myoblasts; (4) exerts its enhancing activity from the cytosol, independent of direct interactions with either the fusogen or the membranes being fused; and (5) contains several regions with protein-protein interaction motifs that influence enhancing activity. We propose that the unique evolution of the FAST proteins as virus-encoded cellular fusogens has allowed them to generate a trans-acting, soluble endodomain peptide to harness a cellular pathway or process involved in the poorly understood process that facilitates the transition from microfusion pores to macrofusion and syncytiogenesis.