title: Transforming growth factor beta-dependent sequential activation of Smad, Bim, and caspase-9 mediates physiological apoptosis in gastric epithelial cells.
abstract: Transforming growth factor beta (TGF-beta) has been implicated in the maintenance of homeostasis in various organs, including the gastric epithelium. In particular, TGF-beta-induced signaling was shown to be required for the differentiation-associated physiological apoptosis of gastric epithelial cells, but its mechanism has not been well understood. In this study, the molecular mechanism of TGF-beta-induced apoptosis was analyzed in a human gastric epithelial cell line, SNU16, as an in vitro model. Expression of Smad7 and Bcl-X(L), but not viral FLIP, was shown to prevent TGF-beta-induced apoptosis, indicating an exclusive requirement of the activation of Smad signaling pathway and mitochondrial dysfunction followed by activation of caspase-9. In addition, treatment with TGF-beta induced binding of Bim, a proapoptotic Bcl-2 homology domain 3 (BH3)-only protein, to Bcl-X(L), which is dependent on the activation of Smad, and reduction in the expression of Bim by RNA interference decreased the sensitivity to TGF-beta-induced apoptosis. Moreover, we found abnormalities in the gastric epithelium of both Bim and caspase-9 knockout mice; these abnormalities were associated with a defect of physiological apoptosis in gastric epithelial cells. These results indicate for the first time that TGF-beta is involved in the physiological loss of gastric epithelial cells by activating apoptosis mediated by Smad, Bim, and caspase-9.
authors.affiliation: Graduate School of Biostudies, Kyoto University, SCRB/Building G, Yoshida Konoe-cho, Sakyo-ku, Kyoto 606-8501, Japan.
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Ohgushi
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Kuroki
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Fukamachi
authors.forename: Lorraine A
authors.initials: LA
authors.lastname: O'Reilly
authors.forename: Keisuke
authors.initials: K
authors.lastname: Kuida
authors.forename: Andreas
authors.initials: A
authors.lastname: Strasser
authors.forename: Shin
authors.initials: S
authors.lastname: Yonehara
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism*; D000072224:Bcl-2-Like Protein 11; D015153:Blotting, Western; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism*; D002454:Cell Differentiation; D002460:Cell Line; D045744:Cell Line, Tumor; D003433:Crosses, Genetic; D003513:Cycloheximide / Q000494:pharmacology; D004848:Epithelium / Q000378:metabolism*; D005260:Female; D005753:Gastric Mucosa / Q000378:metabolism*; D006801:Humans; D047468:Immunoprecipitation; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008928:Mitochondria / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D034622:RNA Interference; D012680:Sensitivity and Specificity; D015398:Signal Transduction; D051785:Smad Proteins / Q000378:metabolism*; D051906:Smad7 Protein / Q000378:metabolism; D013997:Time Factors; D016212:Transforming Growth Factor beta / Q000378:metabolism*; D053773:Transforming Growth Factor beta1; D051020:bcl-X Protein / Q000378:metabolism
chemical_list: D051017:Apoptosis Regulatory Proteins; C000606775:BCL2L11 protein, human; D000072224:Bcl-2-Like Protein 11; C000606776:Bcl2l11 protein, mouse; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C506386:CFLAR protein, human; C506387:Cflar protein, mouse; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; D051785:Smad Proteins; D051906:Smad7 Protein; C508960:TGFB1 protein, human; C508961:Tgfb1 protein, mouse; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D051020:bcl-X Protein; D000255:Adenosine Triphosphate; D003513:Cycloheximide; C506433:CASP9 protein, human; C506434:Casp9 protein, mouse; D053453:Caspase 9; D020169:Caspases