C. elegans CED-3 caspase promotes non-apoptotic linker cell dismantling but not death onset

Abstract

Nuclear degradation accompanies cell death. To study this process, we followed nuclear dismantling of the C. elegans linker cell, which undergoes non-apoptotic morphologically-conserved cell death characterized by nuclear envelope crenellations and cell splitting. We show that although linker cell death is cell autonomous, nucleus elimination follows engulfment and is blocked in rab-35 and arf-6 phagosome maturation mutants. Surprisingly, although linker cell death is independent of the apoptotic caspase CED-3, CED-3 is partially required within the linker cell, and upstream of RAB-35 and ARF-6, for cell splitting, engulfment, and nucleus elimination. In parallel studies, we found that the kinase inhibitor staurosporine causes mouse embryonic fibroblasts to undergo caspase-independent non-apoptotic death accompanied by nuclear crenellations and, paradoxically, by Caspase-3/7 activation. Our findings suggest mechanistic similarities between staurosporine-induced and linker cell death, revealing that, in some contexts, caspases do not initiate cell death but instead promote subcellular tasks required for cell clearance.