Fig. 6

The biogenesis and release mechanisms of exosomes during pyroptosis. Classical: The ESCRT-0 complex initiates intracellular sorting and recruits ESCRT-I. Collaboratively, ESCRT-I and ESCRT-II orchestrate membrane invagination, giving rise to early endosomes (ESEs). These ESEs undergo mutual fusion, maturing into late endosomes (LSEs). Pyroptosis: NLRP3 oligomerizes and recruits pro-caspase 1 and ASC to assemble the NLRP3 inflammasome. Upon activation, caspase-1 in the NLRP3 inflammasome cleaves the substrate protein GSDMD. This cleavage results in the translocation of the N-terminal fragment of GSDMD to the plasma membrane, where it interacts with phospholipids and forms 10–15 nm pores. GSDMD can also form complexes with ESCRT. Cascanically, caspase-4/5/11 are directly activated to cleave GSDMD, resulting in the formation of pores in the membrane. The NLRP3 inflammasome, caspase-1, and N-terminal fragment of GSDMD can promote LSE formation and cargo sorting, leading to encapsulation in the endolysosomal lumen. Inflammatory cytokines such as IL-1β and IL-18 can also be encapsulated in LSEs. Ultimately, LSEs fuse into MVBs. MVBs release exosomes through GSDMD-ESCRT-driven membrane invagination. Exosomes can also be released by the ruptured cell membrane or actively released through GSDMD pores in the membrane. In addition to exosomes, pyroptotic cells also release pyroptosis bodies. (Black arrows: involved in pyroptosis mechanisms; purple arrows: involved in exosome biogenesis; curved purple arrows: involved in the formation of exosome cargo)