Gasdermin D plays a vital role in the generation of neutrophil extracellular traps

Abstract

The death of a cell is an inevitable part of its biology. During homeostasis, most cells die through apoptosis. If homeostasis is disturbed, cell death can switch to proinflammatory forms of death, such as necroptosis, pyroptosis, or NETosis. We demonstrate that the formation of neutrophil extracellular traps (NETs), a special form of neutrophil cell death that releases chromatin structures to the extracellular space, is dependent on gasdermin D (GSDMD). GSDMD is a pore-forming protein and an executor of pyroptosis. We screened a chemical library and found a small molecule based on the pyrazolo-oxazepine scaffold that efficiently blocks NET formation and GSDMD-mediated pyroptotic cell death in human cells. During NETosis, GSDMD is proteolytically activated by neutrophil proteases and, in turn, affects protease activation and nuclear expansion in a feed-forward loop. In addition to the central role of GSDMD in pyroptosis, we propose that GSDMD also plays an essential function in NETosis.

Beyond inflammasomes: emerging function of gasdermins during apoptosis and NETosis

“…However, whether GSDMD promotes spontaneous neutrophil cell death is controversial, as other studies documented similar rate of spontaneous neutrophil death in wildtype versus Gsdmd-deficient neutrophils (Chen et al, 2018b;Burgener et al, 2019). In agreement with macrophage studies showing that the GSDMD NT fragment triggers proinflammatory cell death, a second study reported that activation of GSDMD by neutrophil elastase drives neutrophil cell lysis and NET extrusion, a well-appreciated antimicrobial defence mechanism (Sollberger et al, 2018). Therefore, it appears that GSDMD activity in neutrophils can either promote or dampen host defence.…”

Guanylate-binding proteins at the crossroad of noncanonical inflammasome activation during bacterial infections

“…In addition, the secretion of cytokines and mediators through GSDMD pores recruits neutrophils that remove these pore‐induced intracellular traps by efferocytosis, assisting the control of bacterial infection . Furthermore, recent studies linked GSDMD to the release of neutrophil extracellular traps (NETs), a cell death process termed NETosis . These structures are composed of neutrophil DNA and granular proteins such as neutrophil elastase (NE), myeloperoxidase, and cathepsin G. These NETs act as a barrier that avoids bacterial spreading and also kill pathogens by degrading their virulent factors .…”

“…These structures are composed of neutrophil DNA and granular proteins such as neutrophil elastase (NE), myeloperoxidase, and cathepsin G. These NETs act as a barrier that avoids bacterial spreading and also kill pathogens by degrading their virulent factors . In view of that, GSDMD can be cleaved by serine proteases such as NE . Once it is cleaved, it leads to pore formation in the membrane of neutrophil azurophilic granules, thus contributing to enhance NE release in the cytosol .…”

“…Furthermore, NE released in the cytosol can also cleave more GSDMD promoting a positive feedback as GSDMD triggers more pore formation in the neutrophil azurophilic granules membranes. Finally, cleaved GSDMD also inserts into plasmatic cell membrane culminating cell lysis and release of NETs . Notably, this is a process in which GSDMD is involved in pore formation independent of inflammasome activation.…”

“…On the other hand, PAMPs that trigger noncanonical inflammasome such as intracellular LPS can trigger GSDMD‐dependent NET formation, but independently of classical proteins such as NE and myeloperoxidase, describing a new pathway of NET release . Moreover, N‐terminal fragments of GSDMD were found in these traps after release, suggesting a possible role for GSDMD in pathogens restriction by directly killing microbes outside the cells . Remarkably, this direct killing may constitute a novel manner that GSDMD reduces the spread of viable pathogens from pyroptotic cells, although it lacks confirmation by in vivo studies.…”