Type II integral membrane protein, TM of J paramyxovirus promotes cell-to-cell fusion

• Published in: Proceedings of the National Academy of Sciences - PNAS 2015-10, Vol.112 (40), p.12504-12509
• Main Authors: Li, Zhuo, Hung, Cher, Paterson, Reay G., Michel, Frank, Fuentes, Sandra, Place, Ryan, Lin, Yuan, Hogan, Robert J., Lamb, Robert A., He, Biao
• Format: Article
• Language: English
• Subjects: Amino acids; Animals; Bioassays; Biochemical analysis; Biological Sciences; Cell Fusion; Cell Line; Chlorocebus aethiops; Electrophoresis, Polyacrylamide Gel; Flow Cytometry; Fluorescent Antibody Technique; Gene expression; Giant Cells - metabolism; Glycoproteins - genetics; Glycoproteins - metabolism; HEK293 Cells; Humans; Membrane Proteins - genetics; Membrane Proteins - metabolism; Mutation; Paramyxovirinae - genetics; Paramyxovirinae - growth & development; Paramyxovirinae - metabolism; Paramyxovirus; Pathogens; Protein Binding; Proteins; Vero Cells; Viral Fusion Proteins - genetics; Viral Fusion Proteins - metabolism; Viral Plaque Assay; Viral Proteins - genetics; Viral Proteins - metabolism
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1509476112

Paramyxoviruses include many important animal and human pathogens. Most paramyxoviruses have two integral membrane proteins: fusion protein (F) and attachment proteins hemagglutinin, hemagglutinin–neuraminidase, or glycoprotein (G), which are critical for viral entry into cells. J paramyxovirus (JPV) encodes four integral membrane proteins: F, G, SH, and transmembrane (TM). The function of TM is not known. In this work, we have generated a viable JPV lacking TM (JPVΔTM). JPVΔTM formed opaque plaques compared with JPV. Quantitative syncytia assays showed that JPVΔTM was defective in promoting cell-to-cell fusion (i.e., syncytia formation) compared with JPV. Furthermore, cells separately expressing F, G, TM, or F plus G did not form syncytia whereas cells expressing F plus TM formed some syncytia. However, syncytia formation was much greater with coexpression of F, G, and TM. Biochemical analysis indicates that F, G, and TM interact with each other. A small hydrophobic region in the TM ectodomain from amino acid residues 118 to 132, the hydrophobic loop (HL), was important for syncytial promotion, suggesting that the TM HL region plays a critical role in cell-to-cell fusion.