Mutations in the putative dimer-dimer interfaces of the measles virus hemagglutinin head domain affect membrane fusion triggering.
Measles virus (MV), an enveloped RNA virus belonging to the Paramyxoviridae family, enters the cell through membrane fusion mediated by two viral envelope proteins, an attachment protein hemagglutinin (H) and a fusion (F) protein. The crystal structure of the receptor-binding head domain of MV-H bound to its cellular receptor revealed that the MV-H head domain forms a tetrameric assembly (dimer of dimers), which occurs in two forms (forms I and II). In this study, we show that mutations in the putative dimer-dimer interface of the head domain in either form inhibit the ability of MV-H to support membrane fusion, without greatly affecting its cell surface expression, receptor binding, and interaction with the F protein. Notably, some anti-MV-H neutralizing monoclonal antibodies are directed to the region around the dimer-dimer interface in form I rather than receptor-binding sites. These observations suggest that the dimer-dimer interactions of the MV-H head domain, especially that in form I, contribute to triggering membrane fusion, and that conformational shift of head domain tetramers plays a role in the process. Furthermore, our results indicate that although the stalk and transmembrane regions may be mainly responsible for the tetramer formation of MV-H, the head domain alone can form tetramers, albeit at a low efficiency.
Department of Virology, Faculty of Medicine, Kyushu University, Fukuoka 812-8582, Japan; Howard Hughes Medical Institute, Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309.
Mai
M
Nakashima
Department of Virology, Faculty of Medicine, Kyushu University, Fukuoka 812-8582, Japan. Electronic address: yuuta@virology.med.kyushu-u.ac.jp.
Yuta
Y
Shirogane
Department of Immunology and Microbial Science, Scripps Research Institute, La Jolla, California 92037.
Takao
T
Hashiguchi
Department of Virology, Faculty of Medicine, Kyushu University, Fukuoka 812-8582, Japan. Electronic address: yyanagi@virology.med.kyushu-u.ac.jp.
Yusuke
Y
Yanagi
D000818:Animals; D015703:Antigens, CD / Q000378:metabolism; D016466:CHO Cells; D006224:Cricetinae; D057809:HEK293 Cells; D006389:Hemagglutinins, Viral / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D008459:Measles virus / Q000235:genetics* / Q000502:physiology; D051916:Membrane Cofactor Protein / Q000378:metabolism; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D020125:Mutation, Missense; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs / Q000235:genetics; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D011956:Receptors, Cell Surface / Q000378:metabolism; D000071177:Signaling Lymphocytic Activation Molecule Family Member 1; D014760:Viral Fusion Proteins / Q000378:metabolism; D053586:Virus Internalization
D015703:Antigens, CD; C497857:CD46 protein, human; D006389:Hemagglutinins, Viral; D051916:Membrane Cofactor Protein; D011956:Receptors, Cell Surface; D014760:Viral Fusion Proteins; D000071177:Signaling Lymphocytic Activation Molecule Family Member 1