title: Identification of mouse MD-2 residues important for forming the cell surface TLR4-MD-2 complex recognized by anti-TLR4-MD-2 antibodies, and for conferring LPS and taxol responsiveness on mouse TLR4 by alanine-scanning mutagenesis.
abstract: The expression of MD-2, which associates with Toll-like receptor (TLR) 4 on the cell surface, confers LPS and LPS-mimetic Taxol responsiveness on TLR4. Alanine-scanning mutagenesis was performed to identify the mouse MD-2 residues important for conferring LPS and Taxol responsiveness on mouse TLR4, and for forming the cell surface TLR4-MD-2 complex recognized by anti-TLR4-MD-2 Ab MTS510. Single alanine mutations were introduced into mouse MD-2 (residues 17-160), and the mutants were expressed in a human cell line expressing mouse TLR4. Mouse MD-2 mutants, in which a single alanine mutation was introduced at Cys37, Leu71, Leu78, Cys95, Tyr102, Cys105, Glu111, Val113, Ile117, Pro118, Phe119, Glu136, Ile138, Leu146, Cys148, or Thr152, showed dramatically reduced ability to form the cell surface mouse TLR4-mouse MD-2 complex recognized by MTS510, and the mutants also showed reduced ability to confer LPS and Taxol responsiveness. In contrast, mouse MD-2 mutants, in which a single alanine mutation was introduced at Tyr34, Tyr36, Gly59, Val82, Ile85, Phe126, Pro127, Gly129, Ile153, Ile154, and His155 showed normal ability to form the cell surface mouse TLR4-mouse MD-2 complex recognized by MTS510, but their ability to confer LPS and Taxol responsiveness was apparently reduced. These results suggest that the ability of MD-2 to form the cell surface mouse TLR4-mouse MD-2 complex recognized by MTS510 is essential for conferring LPS and Taxol responsiveness on TLR4, but not sufficient. In addition, the required residues at codon numbers 34, 85, 101, 122, and 153 for the ability of mouse MD-2 to confer LPS responsiveness are partly different from those for Taxol responsiveness.
authors.affiliation: Department of Biochemistry and Cell Biology, National Institute of Infectious Diseases, Tokyo, Japan.
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Kawasaki
authors.forename: Hisashi
authors.initials: H
authors.lastname: Nogawa
authors.forename: Masahiro
authors.initials: M
authors.lastname: Nishijima
mesh_terms: D000409:Alanine / Q000235:genetics; D019943:Amino Acid Substitution / Q000235:genetics; D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism*; D000950:Antigens, Ly / Q000235:genetics / Q000276:immunology* / Q000378:metabolism* / Q000502:physiology; D001224:Aspartic Acid / Q000235:genetics; D002460:Cell Line; D002462:Cell Membrane / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D029721:Drosophila Proteins; D018698:Glutamic Acid / Q000235:genetics; D006801:Humans; D008024:Ligands; D018950:Lipopolysaccharide Receptors / Q000235:genetics / Q000276:immunology / Q000378:metabolism / Q000502:physiology; D008070:Lipopolysaccharides / Q000378:metabolism / Q000494:pharmacology*; D051218:Lymphocyte Antigen 96; D008562:Membrane Glycoproteins / Q000235:genetics / Q000276:immunology* / Q000378:metabolism* / Q000502:physiology; D051379:Mice; D016297:Mutagenesis, Site-Directed; D017239:Paclitaxel / Q000378:metabolism / Q000494:pharmacology*; D011956:Receptors, Cell Surface / Q000235:genetics / Q000276:immunology* / Q000378:metabolism* / Q000502:physiology; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D014162:Transfection
chemical_list: D000911:Antibodies, Monoclonal; D000950:Antigens, Ly; D029721:Drosophila Proteins; D008024:Ligands; D018950:Lipopolysaccharide Receptors; D008070:Lipopolysaccharides; C411728:Ly96 protein, mouse; D051218:Lymphocyte Antigen 96; D008562:Membrane Glycoproteins; D011956:Receptors, Cell Surface; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D001224:Aspartic Acid; D018698:Glutamic Acid; D000409:Alanine; D017239:Paclitaxel