title: Granzyme A loading induces rapid cytolysis and a novel form of DNA damage independently of caspase activation.
abstract: 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.
authors.affiliation: Center for Blood Research and Department of Pediatrics, Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: P J
authors.initials: PJ
authors.lastname: Beresford
authors.forename: Z
authors.initials: Z
authors.lastname: Xia
authors.forename: A H
authors.initials: AH
authors.lastname: Greenberg
authors.forename: J
authors.initials: J
authors.lastname: Lieberman
mesh_terms: 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
chemical_list: D004950:Esterases; D053804:Granzymes; D012697:Serine Endopeptidases; C509212:GZMA protein, human; D020169:Caspases