Gasdermins (GSDMs) are a family of pore-forming effectors that permeabilize the cell membrane during the cell death program pyroptosis1. GSDMs are activated by proteolytic removal of autoinhibitory carboxy-terminal domains, typically by caspase regulators1,2,3,4,5,6,7,8,9. However, no activator is known for one member of this family, GSDMA. Here we show that the major human pathogen group A Streptococcus (GAS) secretes a protease virulence factor, SpeB, that induces GSDMA-dependent pyroptosis. SpeB cleavage of GSDMA releases an active amino-terminal fragment that can insert into membranes to form lytic pores. GSDMA is primarily expressed in the skin10, and keratinocytes infected with SpeB-expressing GAS die of GSDMA-dependent pyroptosis. Mice have three homologues of human GSDMA, and triple-knockout mice are more susceptible to invasive infection by a pandemic hypervirulent M1T1 clone of GAS. These results indicate that GSDMA is critical in the immune defence against invasive skin infections by GAS. Furthermore, they show that GSDMs can act independently of host regulators as direct sensors of exogenous proteases. As SpeB is essential for tissue invasion and survival within skin cells, these results suggest that GSDMA can act akin to a guard protein that directly detects concerning virulence activities of microorganisms that present a severe infectious threat.
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We thank V. Nizet for insights and bacterial strains. This study received materials from the Emory Investigational Clinical Microbiology Core (supported by the Department of Medicine, Division of Infectious Diseases) and the Emory Mouse Transgenic and Gene Targeting Core (subsidized by the Emory University School of Medicine and receives support from National Institutes of Health (NIH; UL1TR000454)). C.N.L. received support from NIH grants AI130223 and AI153071. The content is solely the responsibility of the authors and does not necessarily reflect the official views of the NIH.
D.L.L. and C.N.L. are named inventors on a US provisional patent application (No. 63/234,810) that describes GSDMA activities.
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Extended data figures and tables
a, Cytotoxicity of HEK293Ts transfected with human GSDMs ± SpeB. Data are the mean±s.d. of 4 technical replicates. P values were calculated by two-tailed Student’s t-test. b, Membranes spotted with lipids were incubated with indicated proteins and binding was assessed by immunoblot for GSDMA. c, Thermal melt analysis of GSDMA and GSDMAΔ240-247 with melting temperatures indicated. (a–c) data are representative of three independent experiments.
Human GSDMA (Q96QA5), mouse GSDMA_1 (Q9EST1), mouse GSDMA_2 (Q32M21), mouse GSDMA_3 (Q5Y4Y6) aligned with Clustal Omega algorithm in DNASTAR. Disordered solvent accessible loop (gray box). Inverted arrows identify cleavage sites of SpeB on hGSDMA. Residues 240–247 of hGSDMA are identified (green bar).
a, b, Keratinocytes were infected (MOI = 100) with GAS 5448, isogenic mutant controls, or clinical isolates for 4 h and (a) lysis measured by LDH release and (b) SpeB activity measured using specific substrate Mca-IFFDTWDNE-Lys-Dnp. c, GAS labeled with Bocillin was incubated with keratinocytes (MOI = 100) 1 h, washed, and adherence measured by fluorescence. Data are representative of three independent experiments with 3 technical replicates and are presented as the mean±s.d. P values were calculated by two-way ANOVA compared to 5448 (M1) control; P < 0.0001.
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LaRock, D.L., Johnson, A.F., Wilde, S. et al. Group A Streptococcus induces GSDMA-dependent pyroptosis in keratinocytes. Nature 605, 527–531 (2022). https://doi.org/10.1038/s41586-022-04717-x