Importance of the major extracellular domain of CD9 and the epidermal growth factor (EGF)-like domain of heparin-binding EGF-like growth factor for up-regulation of binding and activity.
Heparin-binding epidermal growth factor (EGF)-like growth factor (HB-EGF) is a member of the EGF family of growth factors. The membrane-anchored form of HB-EGF (proHB-EGF) is mitogenically active to neighboring cells as well as being a precursor of the soluble form. In addition to its mitogenic activity, proHB-EGF has the property of binding to diphtheria toxin (DT), serving as the specific receptor for DT. Tetramembrane-spanning protein CD9, a member of the TM4 superfamily, is physically associated with proHB-EGF at the cell surface and up-regulates both mitogenic and DT binding activities of proHB-EGF. To understand this up-regulation mechanism, we studied essential regions of both CD9 and proHB-EGF for up-regulation. Immunoprecipitation experiments revealed that not only CD9 but also other TM4 proteins including CD63, CD81, and CD82 associate with proHB-EGF on the cell surface. However, these TM4 proteins did not up-regulate DT binding activity of proHB-EGF. Transfection of a series of chimeric constructs comprising CD9 and CD81 showed that the major extracellular domain of CD9 is essential for up-regulation. Assays of DT binding activity and juxtacrine mitogenic activity of the deletion mutants of proHB-EGF and chimeric molecules, derived from proHB-EGF and TGF-alpha, showed that the essential domain of proHB-EGF for up-regulation is the EGF-like domain. These results indicate that the interaction of the extracellular domains of both molecules is important for up-regulation.
Nakamura
K
K
Division of Cell Biology, Institute of Life Science, and Research Center for Innovative Cancer Therapy, Kurume University, Kurume, Fukuoka 839-0861, Japan.
Mitamura
T
T
Takahashi
T
T
Kobayashi
T
T
Mekada
E
E
D000818:Animals; D015703:Antigens, CD / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D002522:Chlorocebus aethiops; D004815:Epidermal Growth Factor / Q000737:chemistry* / Q000378:metabolism; D006493:Heparin / Q000378:metabolism*; D066257:Heparin-binding EGF-like Growth Factor; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins; D051861:Kangai-1 Protein; D007739:L Cells; D008562:Membrane Glycoproteins / Q000378:metabolism; D008565:Membrane Proteins; D051379:Mice; D010980:Platelet Membrane Glycoproteins / Q000378:metabolism; D011485:Protein Binding; D011518:Proto-Oncogene Proteins; D011956:Receptors, Cell Surface / Q000737:chemistry; D013329:Structure-Activity Relationship; D060225:Tetraspanin 28; D060245:Tetraspanin 29; D060149:Tetraspanin 30; D015854:Up-Regulation; D014709:Vero Cells
D015703:Antigens, CD; C554586:CD63 protein, human; C554798:CD81 protein, human; C497688:CD82 protein, human; C554869:CD9 protein, human; C554587:Cd63 protein, mouse; C554799:Cd81 protein, mouse; C497689:Cd82 antigen, mouse; C554870:Cd9 protein, mouse; C587883:HBEGF protein, human; C587884:Hbegf protein, mouse; D066257:Heparin-binding EGF-like Growth Factor; D036341:Intercellular Signaling Peptides and Proteins; D051861:Kangai-1 Protein; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D010980:Platelet Membrane Glycoproteins; D011518:Proto-Oncogene Proteins; D011956:Receptors, Cell Surface; D060225:Tetraspanin 28; D060245:Tetraspanin 29; D060149:Tetraspanin 30; D004815:Epidermal Growth Factor; D006493:Heparin