Apaf-1 Pyroptosome Senses Mitochondrial Permeability Transition

Abstract

HighlightsBile acids trigger caspase-4/11 and GSDME dependent pyroptosis Caspase-4/11 is a general sensor of mitochondrial permeability transition (MPT) MPT drives Apaf-1/capase-4 pryoptosome assembly Caspase-11 and GSDME mediated pyroptosis underlies cholesteric liver damage eTOC Blurb Persistent mitochondrial permeability transition elicited by bile acids, calcium overload and specifically ANT1 activators drives assembly of Apaf-1-capase-4/11 pyroptosome triggering GSDME dependent pryroptosis. 3 SUMMARY Caspase-4 directly senses and is activated by cytosolic LPS in conditions of pathogen infection. It is unclear whether and how caspase-4 detects host derived factors for triggering pyroptosis. Here we show that mitochondrial permeability transition (MPT) promotes the assembly of a protein complex comprised of Apaf-1 and caspase-4 (caspase-11 in mice)， defined herein as pyroptosome, for the execution of facilitated pyroptosis. MPT induced by bile acids and calcium overload, and specifically by an adenine nucleotide translocator 1 (ANT1) activator, triggered pyroptosome assembly. Different from the direct cleavage of GSDMD by LPS-activated caspase-4, caspase-4 activated in the Apaf-1 pyroptosome proceeds to cleave caspase-3 and thereby gasdermin E (GSDME) to induce pyroptosis. Caspase-11 initiated and GSDME executed pyroptosis underlies cholesteric liver failure. These findings identify Apaf-1 pyroptosome as a pivotal machinery for cells sensing MPT signals and may shed lights on understanding how cells execute pyroptosis under sterile conditions.contrast, knockout of caspase-1 exerted little influence on bile acid induced cell death and IL-1α secretion, confirming that the featured cell death triggered by bile acid is caspase-11 mediated pyroptosis (Figures 1I-L). Cytotoxicity of bile acids at concentrations higher than 400 μ M might be partially related to their detergent effects (Benedetti et al., 1997). We further demonstrated that equivalent amount of SDS to that of 200 μ M bile acid was unable to activate caspases, excluding the possibility of detergent effects being involved in caspase activation by bile acids (Figures S1J-M). Neither RIP1 inhibitor nor MLKL inhibitor blocked bile acids induced cell death, suggesting that bile acids induced cell death was not necroptosis (Figures S1N and S1O). Moreover, our previous results excluded TLR4 dependence of bile acids function (Hao et al., 2017) and the assay here further verified that bile acids applied as well as cell cultures were free of LPS contamination and bile acids were tested without LPS priming for all experiments performed in this study (STAR Methods).

ER stress induces caspase‐2‐tBID‐GSDME‐dependent cell death in neurons lytically infected with herpes simplex virus type 2

“…These data indicate that BID serves downstream of CASP2 to activate GSDME-mediated pyroptosis. As described above, tBID targets the mitochondria to promote depolarization and the intrinsic apoptosis cell death pathways (Bock & Tait, 2020;Xu et al, 2021). Accordingly, we observed that HSV-2 infection strongly impaired mitochondrial function as measured by NADPH reductase activity (Fig 4G).…”

Neurotoxic β-amyloid oligomers cause mitochondrial dysfunction—the trigger for PANoptosis in neurons

“…Cyto C also triggers the inositol trisphosphate (IP3) receptor, thereby increasing cytoplasmic Ca 2+ levels and ROS generation. Apaf-1 can also interact with caspase 4 to form a novel protein complex that further activates the caspase-3-GSDME signaling pathway, leading to rapid cell pyroptosis (Xu et al, 2021b). Activated caspases can also cleave GSDM proteins, releasing their N-terminal domains; the released domains bind to membrane lipids and continuously disrupt the inner and outer mitochondrial membranes while inducing cell pyroptosis (Liu et al, 2021;Miao et al, 2023).…”