Granzyme A loading induces rapid cytolysis and a novel form of DNA damage independently of caspase activation.
Cytotoxic lymphocytes trigger apoptosis by releasing perforin and granzymes (Grn). GrnB activates the caspase apoptotic pathway, but little is known about GrnA-induced cell death. Perforin was used to load recombinant GrnA and GrnB and enzymatically inactive variants into target cells. GrnA induces single-strand DNA breaks that can be labeled with Klenow polymerase and visualized on alkaline gels. GrnA-induced DNA damage but not cytolysis requires GrnA proteolysis. GrnA-induced membrane perturbation, nuclear condensation, and DNA damage are unimpaired by caspase blockade. GrnA fails to induce cleavage of caspase-3, lamin B, rho-GTPase, or PARP. GrnA-induced cytotoxicity and cleavage of PHAP II, a previously identified GrnA substrate, are unimpaired in Jurkat cells that overexpress bcl-2. Therefore, GrnA activates a novel apoptotic pathway.
Beresford
P J
PJ
Center for Blood Research and Department of Pediatrics, Harvard Medical School, Boston, Massachusetts 02115, USA.
Xia
Z
Z
Greenberg
A H
AH
Lieberman
J
J
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D020169:Caspases / Q000378:metabolism*; D003602:Cytotoxicity, Immunologic / Q000187:drug effects; D004249:DNA Damage; D004789:Enzyme Activation; D004950:Esterases / Q000378:metabolism; D015870:Gene Expression; D019254:Genes, bcl-2 / Q000235:genetics; D053804:Granzymes; D006801:Humans; D020014:K562 Cells / Q000187:drug effects; D012697:Serine Endopeptidases / Q000494:pharmacology*; D013602:T-Lymphocytes, Cytotoxic / Q000187:drug effects*; D014407:Tumor Cells, Cultured
D004950:Esterases; D053804:Granzymes; D012697:Serine Endopeptidases; C509212:GZMA protein, human; D020169:Caspases