| Post Translational Modifications | Cleavage at Asp-276 by CASP1 (mature and uncleaved precursor forms), CASP4/CASP11 or CASP8 relieves autoinhibition and is sufficient to initiate pyroptosis. Cleavage by CASP1 and CASP4/CASP11 is not strictly dependent on the consensus cleavage site on GSDMD but depends on an exosite interface on CASP1 that recognizes and binds the Gasdermin-D, C-terminal (GSDMD-CT) part. Cleavage by CASP8 takes place following inactivation of MAP3K7/TAK1 by Yersinia toxin YopJ. Cleavage at Asp-88 by CASP3 or CAPS7 inactivates the ability to mediate pyroptosis, but generates the Gasdermin-D, p13 chain, which translocates to the nucleus and acts as a transcription regulator. Cleavage by papain allergen generates the Gasdermin-D, p40 chain. Gasdermin-D: Succination of Cys-192 by the Krebs cycle intermediate fumarate, which leads to S-(2-succinyl)cysteine residues, inhibits processing by caspases, and ability to initiate pyroptosis. Succination modification is catalyzed by a non-enzymatic reaction caused by an accumulation of fumarate. |
| Function | Gasdermin-D: Precursor of a pore-forming protein that plays a key role in host defense against pathogen infection and danger signals. This form constitutes the precursor of the pore-forming protein: upon cleavage, the released N-terminal moiety (Gasdermin-D, N-terminal) binds to membranes and forms pores, triggering pyroptosis. Gasdermin-D, N-terminal: Promotes pyroptosis in response to microbial infection and danger signals. Produced by the cleavage of gasdermin-D by inflammatory caspases CASP1 or CASP4/CASP11 in response to canonical, as well as non-canonical (such as cytosolic LPS) inflammasome activators. After cleavage, moves to the plasma membrane where it strongly binds to inner leaflet lipids, including monophosphorylated phosphatidylinositols, such as phosphatidylinositol 4-phosphate, bisphosphorylated phosphatidylinositols, such as phosphatidylinositol (4,5)-bisphosphate, as well as phosphatidylinositol (3,4,5)-bisphosphate, and more weakly to phosphatidic acid and phosphatidylserine. Homooligomerizes within the membrane and forms pores of 10-15 nanometers (nm) of inner diameter, allowing the release of mature interleukin-1 (IL1B and IL18) and triggering pyroptosis. Gasdermin pores also allow the release of mature caspase-7 (CASP7). Also forms pores in the mitochondrial membrane, resulting in release of mitochondrial DNA (mtDNA) into the cytosol. Gasdermin-D, N-terminal released from pyroptotic cells into the extracellular milieu rapidly binds to and kills both Gram-negative and Gram-positive bacteria, without harming neighboring mammalian cells, as it does not disrupt the plasma membrane from the outside due to lipid-binding specificity. Under cell culture conditions, also active against intracellular bacteria, such as Listeria monocytogenes. Also active in response to MAP3K7/TAK1 inactivation by Yersinia toxin YopJ, which triggers cleavage by CASP8 and subsequent activation. Strongly binds to bacterial and mitochondrial lipids, including cardiolipin. Does not bind to unphosphorylated phosphatidylinositol, phosphatidylethanolamine nor phosphatidylcholine. Gasdermin-D, p13: Transcription coactivator produced by the cleavage by CASP3 or CASP7 in the upper small intestine in response to dietary antigens. Required to maintain food tolerance in small intestine: translocates to the nucleus and acts as a coactivator for STAT1 to induce the transcription of CIITA and MHC class II molecules, which in turn induce type 1 regulatory T (Tr1) cells in upper small intestine. Gasdermin-D, p40: Produced by the cleavage by papain allergen. After cleavage, moves to the plasma membrane and homooligomerizes within the membrane and forms pores of 10-15 nanometers (nm) of inner diameter, allowing the specific release of mature interleukin-33 (IL33), promoting type 2 inflammatory immune response. |
