title: CD9 amino acids critical for upregulation of diphtheria toxin binding.
abstract: CD9 associates with a diphtheria toxin receptor (DTR) that is identical to the membrane-anchored form of heparin-binding EGF-like growth factor. We determined the region of CD9 important for upregulation activity. Human and monkey CD9 upregulates DT binding activity of DTR, while mouse CD9 has no upregulation activity. Transfection of chimeric constructs comprising monkey and mouse CD9s showed that the human sequence between Ala156 and Asp183 is essential for the upregulation activity. Studies of mutants, replacing a single amino acid within the region between Ala156 and Asp183 of monkey CD9 with the corresponding amino acid residue in mouse CD9, revealed that substitution of Gly158 is critical for the reduction of the upregulation activity and secondly for the substitution of Val159 and Thr175. These three amino acid residues were deduced to be located on the head domain of the second extracellular loop, suggesting that interactions of CD9 with DTR or DT at the domain containing these three amino acids were important for the upregulation of DT binding.
authors.affiliation: Division of Cell Biology, Kurume University, Kurume, Fukuoka, 839-0861, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Hasuwa
authors.forename: Y
authors.initials: Y
authors.lastname: Shishido
authors.forename: A
authors.initials: A
authors.lastname: Yamazaki
authors.forename: T
authors.initials: T
authors.lastname: Kobayashi
authors.forename: X
authors.initials: X
authors.lastname: Yu
authors.forename: E
authors.initials: E
authors.lastname: Mekada
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D015703:Antigens, CD / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites / Q000235:genetics; D004167:Diphtheria Toxin / Q000378:metabolism*; D004815:Epidermal Growth Factor / Q000378:metabolism; D000882:Haplorhini; D066257:Heparin-binding EGF-like Growth Factor; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins; D007739:L Cells; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D051379:Mice; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D051381:Rats; D011956:Receptors, Cell Surface / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013045:Species Specificity; D060225:Tetraspanin 28; D060245:Tetraspanin 29; D015854:Up-Regulation
chemical_list: D015703:Antigens, CD; C554798:CD81 protein, human; C554869:CD9 protein, human; C554799:Cd81 protein, mouse; C554870:Cd9 protein, mouse; D004167:Diphtheria Toxin; C587883:HBEGF protein, human; C587884:Hbegf protein, mouse; C587885:Hbegf protein, rat; D066257:Heparin-binding EGF-like Growth Factor; D036341:Intercellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D011956:Receptors, Cell Surface; D011993:Recombinant Fusion Proteins; D060225:Tetraspanin 28; D060245:Tetraspanin 29; D004815:Epidermal Growth Factor