Allergen protease-activated stress granule assembly and gasdermin D fragmentation control interleukin-33 secretion

Abstract

Interleukin (IL)-33, an epithelial cell-derived cytokine that responds rapidly to environmental insult, has a critical role in initiating airway in ammation, such as that in asthma. However, the molecular mechanism underlying IL-33 secretion following allergen exposure is not clear. Here, we demonstrated that Gasdermin D (Gsdmd) functions as a conduit for IL-33 secretion following allergen protease exposure. Gsdmd was rapidly cleaved into a functional neo-form, the N-terminal p40 fragment (p40 NT-Gsdmd), in the murine airway epithelium when cells were exposed to allergen proteases from fungi, house dust mites (HDMs), or bacteria. This cleavage event that produces the p40 Gsdmd fragment was independent of in ammatory caspases-1/11, as it could not be inhibited by caspase-1 and caspase-11 de ciency in murine cells. The functional p40 NT-Gsdmd fragment directly contributed to the secretion of both the nuclear full-length form and cytosolic mature form of IL-33. Both Gsdmd de ciency and blockade of the generation of p40 by amino acid mutation or deletion of residues 308-313 (ELRQQ) in the Gsdmd sequence could e ciently prevent IL-33 release in airway epithelial cells. In mice, Gsdmd de ciency prevented IL-33 release and hindered the activation of group 2 innate lymphoid cells (ILC2s), thus alleviating airway in ammation and lung tissue damage after stimulation with HDMs or papain. Our ndings uncovered a mechanism of Gsdmd-mediated IL-33 release under allergen exposure and offer insight into Gsdmd cleavage prevention as a potential approach to reduce allergic airway in ammation.

Gasdermin-D activation promotes NLRP3 activation and host resistance to Leishmania infection

“…Instead, we detect the formation of a 25-kDa fragment, which is independent of caspases 1/7/8/11. The size of this cleaved fragment is also not consistent with GSDMD fragments cleaved by Caspase-8 44,45 , Caspase-3/7 46,47 , and the recently described 40-kDa fragment generated by allergen proteases 48 . It is possible that this alternative cleavage of GSDMD induced by Leishmania results in the inactivation of GSDMD-mediated pores, accounting to explain the transient GSDMD activation that occurred in the absence of cell death in the infected macrophages.…”

Gasdermin D as a cellular switch to orientate immune responses via IL-33 or IL-1β

“…Due to the absence of a secretory signal sequence, IL-33 was thought to be passively released during cell necrosis, physical stress or tissue damage and was accordingly considered an alarmin [2]. However, Chen et al recently demonstrated that in response to exposure to allergen proteases, IL-33 is transported from the nucleus to the cytosol via stress granule (SG) assembly followed by subsequent release of the active cytokine through membrane pores formed by the unusual p40 N-terminal fragment of gasdermin D (Gsdmd) [3]. Importantly, these events were not associated with any signs of cell death, thus uncovering a new pathway of IL-33 release distinct from the "alarmin" archetype (Fig.…”

“…During canonical inflammasome-induced pyroptosis, Gsdmd is proteolytically cleaved by activated caspase-1 to generate an active fragment with membrane pore-forming abilities, which allows the release of IL-1β and IL-18 through unconventional protein secretion [4]. In contrast, Chen et al observed that following stimulation with the allergen protease papain, the formation of a novel p40 or p35 N-terminal (NT) Gsdmd fragment in murine MLE-12 or human A549 epithelial cell lines, respectively, occurred [3]. The appearance of these neofragments was concomitant with the delocalization of IL-33 from the cell nucleus and its release into the supernatant without apparent cell death or caspase activation.…”

Dual Immune Regulatory Roles of Interleukin-33 in Pathological Conditions

“…Second, DCs of mice infected with Nippostrongylus brasiliensis expressed the pore-forming protein perforin-2 functioned as a conduit on the plasma membrane to facilitate IL-33 export contributing to mucosal immunoregulation [ 37 ]. In contrast with myeloid cells, Chen et al [ 38 ] recently found that a neo-form murine amino-terminal p40 fragment gasdermin D promoted cytosolic IL-33 secretion by forming pores in the cell membrane without the apparent occurrence of cell death in allergen-exposed lung epithelial cells. After full-length IL-33 is released by cells under injury or stress, the serine proteases cathepsin G and elastase, released by neutrophils and mast cells, can shear full-length IL-33 to produce highly active IL-33 [ 39 , 40 , 41 ].…”