Heparin-binding EGF-like growth factor, which acts as the diphtheria toxin receptor, forms a complex with membrane protein DRAP27/CD9, which up-regulates functional receptors and diphtheria toxin sensitivity.
DRAP27, the monkey homolog of human CD9 antigen (DRAP27/CD9) and diphtheria toxin receptor (DTR) were expressed in mouse L cells. L cells transfected transiently with both DRAP27/CD9 and DTR cDNA bound approximately 10 times more diphtheria toxin (DT) than cells transfected with DTR alone. Stable L cell transfectants expressing both DTR and DRAP27/CD9 (LCH-1 cells) had 15 times more cell surface DT-binding sites and were 20 times more sensitive to DT than were stable L cell transfectants expressing DTR alone (LH-1 cells). Increased DT-binding and DT sensitivity were not due to increased DTR transcription or increased cell surface DTR protein. Co-immunoprecipitation of DRAP27/CD9 with DTR and chemical cross-linking suggest a tight association of these membrane-bound proteins. In addition, the identity of DTR and a growth factor (HB-EGF) was established. Immobilized DT specifically adsorbed HB-EGF precursor solubilized from transfected L cells and [125I]DT bound to immobilized recombinant HB-EGF. We conclude that DRAP27/CD9 associates tightly with DTR/HB-EGF and up-regulates the number of functional DTRs and DT sensitivity, and that HB-EGF is identical to DTR.
Iwamoto
R
R
Institute of Life Science, Kurume University, Fukuoka, Japan.
Higashiyama
S
S
Mitamura
T
T
Taniguchi
N
N
Klagsbrun
M
M
Mekada
E
E
D000595:Amino Acid Sequence; D000818:Animals; D015703:Antigens, CD / Q000378:metabolism; D004167:Diphtheria Toxin / Q000378:metabolism* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004815:Epidermal Growth Factor / Q000378:metabolism*; D066257:Heparin-binding EGF-like Growth Factor; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins; D007739:L Cells; D008562:Membrane Glycoproteins; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D011485:Protein Binding; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D060245:Tetraspanin 29; D014162:Transfection; D015854:Up-Regulation
D015703:Antigens, CD; C554869:CD9 protein, human; C554870:Cd9 protein, mouse; D004167:Diphtheria Toxin; C587883:HBEGF protein, human; C587884:Hbegf protein, mouse; D066257:Heparin-binding EGF-like Growth Factor; D036341:Intercellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D011956:Receptors, Cell Surface; D011994:Recombinant Proteins; D060245:Tetraspanin 29; D004815:Epidermal Growth Factor