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Original Article |
Correspondence to: R. Chris Bleackley, Dept. of Biochemistry, 463 Medical Sciences Bldg., University of Alberta, Edmonton, Alberta T6G 2H7, Canada. Tel:780-492-3968 Fax:780-492-0886
Cytotoxic T lymphocytes (CTLs) destroy target cells through a mechanism involving the exocytosis of cytolytic granule components including granzyme B (grB) and perforin, which have been shown to induce apoptosis through caspase activation. However, grB has also been linked with caspase-independent disruption of mitochondrial function. We show here that cytochrome c release requires the direct proteolytic cleavage of Bid by grB to generate a 14-kD grB-truncated product (gtBid) that translocates to mitochondria. In turn, gtBid recruits Bax to mitochondria through a caspase-independent mechanism where it becomes integrated into the membrane and induces cytochrome c release. Our results provide evidence for a new pathway by which CTLs inflict damage and explain the caspase-independent mechanism of mitochondrial dysfunction.
Key Words: cytotoxic T lymphocyte, granzyme B, Bcl-2, Bid, Bax
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