Human and Mouse Granzyme A Induce a Proinflammatory Cytokine Response

Abstract

Granzyme A (GzmA) is considered a major proapoptotic protease. We have discovered that GzmA-induced cell death involves rapid membrane damage that depends on the synergy between micromolar concentrations of GzmA and sublytic perforin (PFN). Ironically, GzmA and GzmB, independent of their catalytic activity, both mediated this swift necrosis. Even without PFN, lower concentrations of human GzmA stimulated monocytic cells to secrete proinflammatory cytokines (interleukin-1beta [IL-1beta], TNFalpha, and IL-6) that were blocked by a caspase-1 inhibitor. Moreover, murine GzmA and GzmA(+) cytotoxic T lymphocytes (CTLs) induce IL-1beta from primary mouse macrophages, and GzmA(-/-) mice resist lipopolysaccharide-induced toxicity. Thus, the granule secretory pathway plays an unexpected role in inflammation, with GzmA acting as an endogenous modulator.

Mouse granzyme A induces a novel death with writhing morphology that is mechanistically distinct from granzyme B-induced apoptosis

“…Consistent with previous reports showing modest cytotoxic activity for mGzmA, but none for its human counterpart, 10 we found that proteolytically active recombinant human GzmA (hGzmA) was very poorly cytotoxic when administered with Pfp (Supplementary Figure S7). As hGzmA has been hypothesised to be more involved in promoting proinflammatory immune responses rather than direct cytotoxicity, 8 our data supports the possibility that hGzmA may have developed into a primarily non-cytotoxic immune regulator, whereas mGzmA retained its cytotoxicity, possibly in response to various mouse pathogens.…”

“…[8][9][10]24 Here, we have demonstrated that cell death can be induced when mGzmA is delivered by NKs via authentic CL/target cell interactions.…”

“…5,6 This oxidative stress is predicted to cause translocation of the SET complex into the nucleus, where GzmA cleaves components of the SET complex and induces DNA damage through single-stranded nicking, resulting in cell death. 5,7 However, these findings have been difficult to corroborate and recent studies from several independent groups using recombinant or native protease have reported that GzmA has little cytotoxicity [8][9][10] or that GzmA may simply enhance Pfp-mediated membranolysis. 8 In contrast, studies using GzmB À / À CTL suggest that GzmA does have a role in target cell death.…”

“…5,7 However, these findings have been difficult to corroborate and recent studies from several independent groups using recombinant or native protease have reported that GzmA has little cytotoxicity [8][9][10] or that GzmA may simply enhance Pfp-mediated membranolysis. 8 In contrast, studies using GzmB À / À CTL suggest that GzmA does have a role in target cell death. 11,12 To address this controversy in a physiologically relevant context, we used intact primary mouse NKs to deliver Gzms in order to analyse the features of GzmA-mediated cell death.…”

Granzyme A expression reveals distinct cytolytic CTL subsets following influenza A virus infection

“…Recently, an intriguing function for grzA in eliciting inflammation has been described. Metkar et al provide evidence that both mouse and human grzA stimulate monocytic cells to secrete proinflammatory cytokines [16]. The study of grzA may therefore yield insights into the broader biological roles of the grz family.…”