Stefani, Caroline, Bruchez, Anna M., Rosasco, Mario G., Yoshida, Anna E., Fasano, Kayla J., Levan, Paula F., Lorant, Alina, Hubbard, Nicholas W., Oberst, Andrew, Stuart, Lynda M., and Lacy-Hulbert, Adam
Pore-forming toxins (PFTs) are the largest class of bacterial toxins and contribute to virulence by triggering host cell death. Vertebrates also express endogenous pore-forming proteins that induce cell death as part of host defense. To mitigate damage and promote survival, cells mobilize membrane repair mechanisms to neutralize and counteract pores, but how these pathways are activated is poorly understood. Here, we use a transposon-based gene activation screen to discover pathways that counteract the cytotoxicity of the archetypal PFT Staphylococcus aureus α-toxin. We identify the endolysosomal protein LITAF as a mediator of cellular resistance to PFT-induced cell death that is active against both bacterial toxins and the endogenous pore, gasdermin D, a terminal effector of pyroptosis. Activation of the ubiquitin ligase NEDD4 by potassium efflux mobilizes LITAF to recruit the endosomal sorting complexes required for transport (ESCRT) machinery to repair damaged membrane. Cells lacking LITAF, or carrying naturally occurring disease-associated mutations of LITAF, are highly susceptible to pore-induced death. Notably, LITAF-mediated repair occurs at endosomal membranes, resulting in expulsion of damaged membranes as exosomes, rather than through direct excision of pores from the surface plasma membrane. These results identify LITAF as a key effector that links sensing of cellular damage to repair. Editor's summary: Membrane pores caused by bacterial pore-forming toxins (PFTs) or endogenous pore-forming proteins can trigger cell death. Membrane repair machinery can promote cell survival and resistance to PFTs, but the cellular mechanisms underlying defense against these toxins are not well defined. Stefani et al. performed a transposon mutagenesis screen to identify genes involved in resistance to Staphylococcus aureus α-toxin–induced cell death. They identified that LITAF, an endolysosomal protein, was required for cell survival after α-toxin– and gasdermin D–induced cell death. K+ efflux through membrane pores promoted LITAF localization to endosomes containing α-toxin and initiated assembly of ESCRT machinery, resulting in secretion of damaged membrane in exosomes. This work uncovers a key role for LITAF in sensing plasma membrane damage and activating membrane repair machinery. —Hannah Isles [ABSTRACT FROM AUTHOR]