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