Degradation of Mcl-1 by granzyme B: implications for Bim-mediated mitochondrial apoptotic events.
Recent studies have suggested that in the absence of Bid, granzyme B (GrB) can utilize an unknown alternative pathway to mediate mitochondrial apoptotic events. The current study has elucidated just such a pathway for GrB-mediated mitochondrial apoptotic alterations. Two Bcl-2 family members have been identified as interactive players in this newly discovered mitochondrial response to GrB: the pro-survival protein Mcl-1L and the pro-apoptotic protein, Bim. Expression of Mcl-1L, which localizes mainly to the outer mitochondrial membrane, decreases significantly in cells subjected to CTL-free cytotoxicity mediated by a combination of GrB and replication-deficient adenovirus. The data suggest that Mcl-1L is a substrate for GrB and for caspase-3, but the two enzymes appear to target different cleavage sites. The cleavage pattern of endogenous Mcl-1L resembles that of in vitro translated Mcl-1L subjected to similar proteolytic activity. Co-immunoprecipitation experiments performed with endogenous as well as with in vitro translated proteins suggest that Mcl-1L is a high affinity binding partner of the three isoforms of Bim (extra-long, long, and short). Bim, a BH3-only protein, is capable of mediating the release of mitochondrial cytochrome c, and this activity is inhibited by the presence of exogenous Mcl-1L. The findings presented herein imply that Mcl-1L degradation by either GrB or caspase-3 interferes with Bim sequestration by Mcl-1L.
Han
Jie
J
Departments of Pathology and Plastic Surgery, The University of Pittsburgh School of Medicine and The University of Pittsburgh Cancer Institute, Pittsburgh, Pennsylvania 15213, USA.
Goldstein
Leslie A
LA
Gastman
Brian R
BR
Froelich
Christopher J
CJ
Yin
Xiao-Ming
XM
Rabinowich
Hannah
H
D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins; D000072224:Bcl-2-Like Protein 11; D001665:Binding Sites; D015153:Blotting, Western; D002352:Carrier Proteins / Q000378:metabolism*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002470:Cell Survival; D003001:Cloning, Molecular; D045304:Cytochromes c / Q000378:metabolism; D015536:Down-Regulation; D004591:Electrophoresis, Polyacrylamide Gel; D053804:Granzymes; D006367:HeLa Cells; D006801:Humans; D019169:Jurkat Cells; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D008928:Mitochondria / Q000378:metabolism / Q000473:pathology*; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins / Q000378:metabolism*; D011233:Precipitin Tests; D011485:Protein Binding; D014176:Protein Biosynthesis; D020033:Protein Isoforms; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2; D012697:Serine Endopeptidases / Q000494:pharmacology*; D013347:Subcellular Fractions; D014158:Transcription, Genetic
D051017:Apoptosis Regulatory Proteins; C000606775:BCL2L11 protein, human; D000072224:Bcl-2-Like Protein 11; C000606776:Bcl2l11 protein, mouse; D002352:Carrier Proteins; C579094:Mcl1 protein, mouse; D008565:Membrane Proteins; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins; D020033:Protein Isoforms; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D045304:Cytochromes c; C509213:GZMB protein, human; D053804:Granzymes; C509214:Gzmb protein, mouse; D012697:Serine Endopeptidases; C505407:CASP3 protein, human; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases