title: Cleavage of calnexin caused by apoptotic stimuli: implication for the regulation of apoptosis.
abstract: Calnexin is an endoplasmic reticulum (ER)-resident molecular chaperone that plays an essential role in the correct folding of membrane proteins. We found that calnexin is subjected to partial cleavage in apoptotic mouse cells. Both ER stress-inducing and ER stress-non-inducing apoptotic stimuli caused the cleavage of calnexin, indicating that this event does not always occur downstream of ER stress. The inhibition of caspases that target the amino acid sequence DXXD abrogated calnexin cleavage in apoptotic stimulus-treated cells. In addition, disruption of one of two DXXD sequences located in the cytoplasmic domain caused calnexin to escape cleavage during apoptosis. Furthermore, calnexin was cleaved in vitro by recombinant caspase-3 or caspase-7. Finally, the overexpression of a presumed cleavage product of calnexin partly inhibited apoptosis. These results collectively suggest that caspase-3 or caspase-7 cleaves calnexin, whose cleaved product leads to the attenuation of apoptosis.
authors.affiliation: Department of Molecular Neurobiology, Institute for Developmental Research, Aichi Human Service Center, Kasugai 480-0392, Japan. takizawa@inst-hsc.jp
authors.forename: Takenori
authors.initials: T
authors.lastname: Takizawa
authors.forename: Chizuru
authors.initials: C
authors.lastname: Tatematsu
authors.forename: Kimi
authors.initials: K
authors.lastname: Watanabe
authors.forename: Kanefusa
authors.initials: K
authors.lastname: Kato
authors.forename: Yoshinobu
authors.initials: Y
authors.lastname: Nakanishi
mesh_terms: D000818:Animals; D017209:Apoptosis; D022762:CCAAT-Enhancer-Binding Proteins / Q000378:metabolism; D019556:COS Cells; D037281:Calnexin / Q000737:chemistry* / Q000378:metabolism; D053148:Caspase 3; D053179:Caspase 7; D020169:Caspases / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D004721:Endoplasmic Reticulum / Q000378:metabolism; D019084:Fluorescent Antibody Technique, Indirect; D049452:Green Fluorescent Proteins / Q000378:metabolism; D051379:Mice; D041681:NIH 3T3 Cells; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D013997:Time Factors; D051742:Transcription Factor CHOP; D014157:Transcription Factors / Q000378:metabolism; D014162:Transfection
chemical_list: D022762:CCAAT-Enhancer-Binding Proteins; D018076:DNA, Complementary; C497250:Ddit3 protein, mouse; D014157:Transcription Factors; D037281:Calnexin; D051742:Transcription Factor CHOP; D049452:Green Fluorescent Proteins; D004247:DNA; C505409:Casp3 protein, mouse; C505524:Casp7 protein, mouse; D053148:Caspase 3; D053179:Caspase 7; D020169:Caspases