title: Caspase 12 in calnexin-deficient cells.
abstract: We investigated a role for calnexin, caspase 12, and Bap31 in endoplasmic reticulum stress-induced apoptosis in calnexin-deficient mouse embryonic fibroblasts and a calnexin-deficient human T cell line (NKR). We showed that calnexin-deficient mouse embryonic fibroblasts are relatively resistant to endoplasmic reticulum stress-induced apoptosis. Western blot analysis demonstrated that both wild-type and calnexin-deficient cells contained a caspase 12 protein. Caspase 12 expression was slightly inhibited in calnexin-deficient cells, and the protein carried out specific cleavage in the presence of thapsigargin. Immunoprecipitation experiments revealed that in the endoplasmic reticulum, caspase 12 forms complexes with Bap31 and calnexin. Treatment of wild-type cells with thapsigargin induced apoptosis and cleavage of Bap31. However, in the absence of calnexin, there was no significant cleavage of Bap31. There was also a negligible processing of caspase 8 in these cells. This work indicates that calnexin may play a role in modulating the sensitivity of a cell to apoptosis induced by endoplasmic reticulum stress, in conjunction with caspase 12 and Bap31.
authors.affiliation: Membrane Protein Research Group, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Jody
authors.initials: J
authors.lastname: Groenendyk
authors.forename: Anna
authors.initials: A
authors.lastname: Zuppini
authors.forename: Gordon
authors.initials: G
authors.lastname: Shore
authors.forename: Michal
authors.initials: M
authors.lastname: Opas
authors.forename: R Chris
authors.initials: RC
authors.lastname: Bleackley
authors.forename: Marek
authors.initials: M
authors.lastname: Michalak
mesh_terms: D000818:Animals; D017209:Apoptosis; D037281:Calnexin / Q000378:metabolism*; D053454:Caspase 12 / Q000378:metabolism*; D061945:Caspase Inhibitors; D002460:Cell Line; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005434:Flow Cytometry; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D011485:Protein Binding
chemical_list: C091247:BCAP31 protein, human; D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D008565:Membrane Proteins; D037281:Calnexin; D053454:Caspase 12