Activation of fusion by the SER virus F protein: a low-pH-dependent paramyxovirus entry process.
SER virus, a paramyxovirus closely related to simian virus 5, induces no syncytium formation. The SER virus F protein has a long cytoplasmic tail (CT), and truncation or mutations of the CT result in enhanced syncytium formation (S. Seth, A. Vincent, and R. W. Compans, J. Virol. 77:167-178, 2003; S. Tong, M. Li, A. Vincent, R. W. Compans, E. Fritsch, R. Beier, C. Klenk, M. Ohuchi, and H.-D. Klenk, Virology 301:322-333, 2002). We hypothesized that the presence of the long CT serves to stabilize the metastable conformation of the F protein. We observed that the hemifusion, cytoplasmic content mixing, and syncytium formation ability of the wild-type SER virus F coexpressed with the SER virus hemagglutinin-neuraminidase (HN) protein was enhanced, both qualitatively and quantitatively, at elevated temperatures. We also observed enhanced hemifusion, content mixing, and syncytium formation in SER virus F- and HN-expressing cells at reduced pH conditions ranging between 4.8 and 6.2. We have obtained evidence that in contrast to other paramyxoviruses, entry of SER virus into cells occurs by a low-pH-dependent process, indicating that the conversion to the fusion-active state for SER virus F is triggered by exposure to reduced pH.
Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
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D000818:Animals; D002460:Cell Line; D006224:Cricetinae; D015967:Gene Expression Regulation, Viral; D015726:Giant Cells / Q000502:physiology; D006168:Guinea Pigs; D006863:Hydrogen-Ion Concentration; D008561:Membrane Fusion; D018108:Respirovirus / Q000235:genetics / Q000472:pathogenicity* / Q000502:physiology; D013696:Temperature; D014760:Viral Fusion Proteins / Q000235:genetics / Q000378:metabolism*
D014760:Viral Fusion Proteins