Calnexin deficiency and endoplasmic reticulum stress-induced apoptosis.

CIHR Research Group in Molecular Biology of Membrane Proteins and Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada.
In this study, we used calnexin-deficient cells to investigate the role of this protein in ER stress-induced apoptosis. We found that calnexin-deficient cells are relatively resistant to ER stress-induced apoptosis. However, caspase 3 and 8 cleavage and cytochrome c release were unchanged in these cells, indicating that ER to mitochondria "communication" during apoptotic stimulation is not affected in the absence of calnexin. The Bcl-2:Bax ratio was also not significantly changed in calnexin-deficient cells regardless of whether the ER stress was induced with thapsigargin or not. Ca(2+) homeostasis and ER morphology were unaffected by the lack of calnexin, but ER stress-induced Bap31 cleavage was significantly inhibited. Immunoprecipitation experiments revealed that Bap31 forms complexes with calnexin, which may play a role in apoptosis. The results suggest that calnexin may not play a role in the initiation of the ER stress but that the protein has an effect on later apoptotic events via its influence on Bap31 function.
Mesh Terms:
Apoptosis, Base Sequence, Blotting, Western, Calcium, Calcium-Binding Proteins, Calnexin, Cell Line, Cytoplasm, DNA Primers, Electrophoresis, Polyacrylamide Gel, Endoplasmic Reticulum, Homeostasis, Humans, Membrane Proteins, Microscopy, Electron, Proteins, Proto-Oncogene Proteins, Proto-Oncogene Proteins c-bcl-2, Reverse Transcriptase Polymerase Chain Reaction, Thapsigargin, bcl-2-Associated X Protein
Biochemistry Feb. 26, 2002; 41(8);2850-8 [PUBMED:11851433]
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