Ubiquitous calpains promote both apoptosis and survival signals in response to different cell death stimuli.
The mu- and m-calpain proteases have been implicated in both pro- or anti-apoptotic functions. Here we compared cell death responses and apoptotic or survival signaling pathways in primary mouse embryonic fibroblasts (MEFs) derived from wild type or capn4 knock-out mice which lack both mu- and m-calpain activities. Capn4(-/-) MEFs displayed resistance to puromycin, camptothecin, etoposide, hydrogen peroxide, ultraviolet light, and serum starvation, which was consistent with pro-apoptotic roles for calpain. In contrast, capn4(-/-) MEFs were more susceptible to staurosporine (STS) and tumor necrosis factor alpha-induced cell death, which provided evidence for anti-apoptotic signaling roles for calpain. Bax activation, release of cytochrome c, and activation of caspase-9 and caspase-3 all correlated with the observed cell death responses of wild type or capn4(-/-) MEFs to the various challenges, suggesting that calpain might play distinct roles in transducing different death signals to the mitochondria. There was no evidence that calpain cleaved Bcl-2 family member proteins that regulate mitochondrial membrane permeability including Bcl-2, Bcl-xl, Bad, Bak, Bid, or Bim. However, activation of the phosphatidylinositol 3 (PI3)-kinase/Akt survival signaling pathway was compromised in capn4(-/-) MEFs under all challenges regardless of the cell death outcome, and blocking Akt activation using the PI3-kinase inhibitor LY294002 abolished the protective effect of calpain to STS challenge. We conclude that the anti-apoptotic function of calpain in tumor necrosis factor alpha- and STS-challenged cells relates to a novel role in activating the PI3-kinase/Akt survival pathway.
Tan
Yinfei
Y
Division of Cancer Biology and Genetics, Queen's University Cancer Research Institute, Botterall Hall Rm. A309, Kingston, Ontario K7L-3N6, Canada.
Wu
Chao
C
De Veyra
Teresa
T
Greer
Peter A
PA
D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D002154:Calpain / Q000235:genetics / Q000378:metabolism*; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D045304:Cytochromes c / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005347:Fibroblasts / Q000166:cytology / Q000201:enzymology*; D008247:Lysosomes / Q000378:metabolism; D051379:Mice; D008817:Mice, Mutant Strains; D008928:Mitochondria / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010718:Phosphatidylserines / Q000494:pharmacology; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D019311:Staurosporine / Q000494:pharmacology; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
D004791:Enzyme Inhibitors; D010718:Phosphatidylserines; D016159:Tumor Suppressor Protein p53; D045304:Cytochromes c; D011065:Poly(ADP-ribose) Polymerases; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D002154:Calpain; C449000:m-calpain; C449002:mu-calpain; D019311:Staurosporine