Identification of the BCL2/adenovirus E1B-19K protein-interacting protein 2 (BNIP-2) as a granzyme B target during human natural killer cell-mediated killing.
Cytotoxic lymphocytes eliminate infected cells and tumours via the perforin-mediated delivery of pro-apoptotic serine proteases known as granzymes. Granzyme B triggers apoptosis via the cleavage of a repertoire of cellular proteins, leading to caspase activation and mitochondrial depolarization. A simple bioinformatics strategy identified a candidate granzyme B cleavage site in the widely expressed BNIP-2 (BCL2/adenovirus E1B-19K protein-interacting protein 2). Granzyme B cleaved recombinant BNIP-2 in vitro and endogenous BNIP-2 was cleaved during the NK (natural killer) cell-mediated killing of tumour cells. Cleavage required the site identified in the bioinformatics screen and was caspase-independent. Expression of either full-length BNIP-2 or a truncated molecule mimicking the granzyme B cleaved form was pro-apoptotic and led to the caspase-dependent cleavage of BNIP-2 at a site distinct from granzyme B cleavage. Inhibition of BNIP-2 expression did not affect the susceptibility to NK cell-mediated killing. Furthermore, target cells in which BID (BH3-interacting domain death agonist) expression was inhibited also remained highly susceptible to NK cell-mediated killing, revealing redundancy in the pro-apoptotic response to human cytotoxic lymphocytes. Such redundancy reduces the opportunity for escape from apoptosis induction and maximizes the chances of immune-mediated clearance of infected cells or tumour cells.
Scott
Gina B
GB
Leeds Institute of Molecular Medicine, University of Leeds, St. James's University Hospital, UK.
Bowles
Paul A
PA
Wilson
Erica B
EB
Meade
Josephine L
JL
Low
Boon Chuan
BC
Davison
Adam
A
Blair
G Eric
GE
Cook
Graham P
GP
D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D017124:Conserved Sequence; D003602:Cytotoxicity, Immunologic; D053804:Granzymes / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D007694:Killer Cells, Natural / Q000276:immunology* / Q000378:metabolism; D008969:Molecular Sequence Data; D016415:Sequence Alignment; D013379:Substrate Specificity
C499184:BNIP2 protein, human; D002352:Carrier Proteins; D053804:Granzymes; D020169:Caspases