title: The tetraspanin CD9 modulates epidermal growth factor receptor signaling in cancer cells.
abstract: CD9 is a member of the tetraspanins, and has been shown to be involved in a variety of cellular activities such as migration, proliferation, and adhesion. In addition, it has been known that CD9 can associate with other proteins. Here we demonstrated the physical and functional association of CD9 with epidermal growth factor receptor (EGFR) on MKN-28 cells. Double-immunofluorescent staining and immunoprecipitation demonstrated the complex formation of CD9-EGFR and CD9-beta(1) integrin, and that both complexes are colocalized on the cell surface especially at the cell-cell contact site. Anti-CD9 monoclonal antibody ALB6 induced a dotted or patch-like aggregation pattern of both CD9-EGFR and CD9-beta(1) integrin. The internalization of EGFR after EGF-stimulation was significantly enhanced by the treatment with ALB6. CD9 can associate with EGFR in hepatocellular carcinoma cells (HepG2/CD9) and Chinese hamster ovary cancer cells (CHO-HER/CD9), which were transfected with pTJ/human EGFR/CD9. Furthermore expression of CD9 specifically attenuated EGFR signaling in CHO-HER/CD9 cells through the down regulation of surface expression of EGFR. These results suggest that CD9 might have an important role that attenuates EGFR signaling. Therefore, CD9 not only associates EGFR but also a new regulator, which may affect EGF-induced signaling in cancer cells.
authors.affiliation: Department of Gastroenterology and Hepatology, Graduate School of Medicine, Osaka University, Suita, Japan. murayama@hosp.itami.hyogo.jp
authors.forename: Yoko
authors.initials: Y
authors.lastname: Murayama
authors.forename: Yasuhisa
authors.initials: Y
authors.lastname: Shinomura
authors.forename: Kenji
authors.initials: K
authors.lastname: Oritani
authors.forename: Jun-Ichiro
authors.initials: J
authors.lastname: Miyagawa
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Yoshida
authors.forename: Makoto
authors.initials: M
authors.lastname: Nishida
authors.forename: Fumie
authors.initials: F
authors.lastname: Katsube
authors.forename: Masamichi
authors.initials: M
authors.lastname: Shiraga
authors.forename: Tamana
authors.initials: T
authors.lastname: Miyazaki
authors.forename: Taisei
authors.initials: T
authors.lastname: Nakamoto
authors.forename: Shusaku
authors.initials: S
authors.lastname: Tsutsui
authors.forename: Shinji
authors.initials: S
authors.lastname: Tamura
authors.forename: Shigeki
authors.initials: S
authors.lastname: Higashiyama
authors.forename: Iichirou
authors.initials: I
authors.lastname: Shimomura
authors.forename: Norio
authors.initials: N
authors.lastname: Hayashi
mesh_terms: D000818:Animals; D000906:Antibodies / Q000378:metabolism; D015703:Antigens, CD / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor / Q000378:metabolism*; D006224:Cricetinae; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D019012:Integrin beta1 / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D046912:Multiprotein Complexes / Q000378:metabolism; D009369:Neoplasms / Q000378:metabolism* / Q000473:pathology; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D060245:Tetraspanin 29
chemical_list: D000906:Antibodies; D015703:Antigens, CD; C554869:CD9 protein, human; D019012:Integrin beta1; D008562:Membrane Glycoproteins; D046912:Multiprotein Complexes; D034741:RNA, Small Interfering; D060245:Tetraspanin 29; D066246:ErbB Receptors