Lysoptosis is an evolutionarily conserved cell death pathway moderated by intracellular serpins
Cliff J. Luke, Stephanie Markovina, Misty Good, Ira E. Wight, Brian J. Thomas, John M. Linneman, Wyatt E. Lanik, Olga Koroleva, Maggie R. Coffman, Mark T. Miedel, Qingqing Gong, Arlise Andress, Marlene Campos Guerrero, Songyan Wang, Liyun Chen, Wandy L. Beatty, Kelsey N. Hausmann, Frances V. White, James A. J. Fitzpatrick, Anthony Orvedahl, Stephen C. Pak, Gary A. Silverman
Abstract
Lysosomal membrane permeabilization (LMP) and cathepsin release typifies lysosome-dependent cell death (LDCD). However, LMP occurs in most regulated cell death programs suggesting LDCD is not an independent cell death pathway, but is conscripted to facilitate the final cellular demise by other cell death routines. Previously, we demonstrated that Caenorhabditis elegans (C. elegans) null for a cysteine protease inhibitor, srp-6, undergo a specific LDCD pathway characterized by LMP and cathepsin-dependent cytoplasmic proteolysis. We designated this cell death routine, lysoptosis, to distinguish it from other pathways employing LMP. In this study, mouse and human epithelial cells lacking srp-6 homologues, mSerpinb3a and SERPINB3, respectively, demonstrated a lysoptosis phenotype distinct from other cell death pathways. Like in C. elegans, this pathway depended on LMP and released cathepsins, predominantly cathepsin L. These studies suggested that lysoptosis is an evolutionarily-conserved eukaryotic LDCD that predominates in the absence of neutralizing endogenous inhibitors.