Regulation of CED-3 caspase localization and activation by C. elegans nuclear-membrane protein NPP-14

Abstract

Caspases are cysteine proteases with critical roles in apoptosis. The Caenorhabditis elegans caspase CED-3 is activated by autocatalytic cleavage, a process enhanced by CED-4. Here we report that CED-3 zymogen localizes to the perinuclear region in C. elegans germ cells and that CED-3 autocatalytic cleavage is held in check by C. elegans nuclei and activated by CED-4. The nuclear pore protein NPP-14 interacts with the prodomain of CED-3 zymogen, colocalizes with CED-3 in vivo, and inhibits CED-3 autoactivation in vitro. Several missense mutations in the CED-3 prodomain result in stronger association with NPP-14 and reduced CED-3 activation by CED-4 in the presence of nuclei or NPP-14, leading to cell death defects. Those same mutations enhance autocatalytic cleavage of CED-3 in vitro and increase apoptosis in vivo in the absence of npp-14. Our results reveal a critical role for nuclei and nuclear membrane proteins in regulating activation and localization of CED-3.

Interaction between DLC-1 and SAO-1 facilitates CED-4 translocation during apoptosis in the Caenorhabditis elegans germline

“…Once apoptosis activated, several caspase precursors, localized initially in mitochondria, are translocated to the nucleus where they execute their apoptotic functions [ 2 , 35 – 37 ]. Specifically, among the core apoptotic proteins, CED-4 translocated from the mitochondrial membrane to the nuclear membrane to activate CED-3 pro-caspase, and induce apoptosis [ 12 , 19 , 20 ]. This translocation requires the binding of CED-4 with CED-9 at the outer mitochondrial membrane.…”

“…The resultant conformational change in CED-9/BCL-2 leads to the release of CED-4/Apaf-1 from mitochondria and its subsequent translocation to the nuclear membrane [ 12 ]. Finally, the CED-3/Caspase protein is activated, and cell death ensues [ 13 – 19 ]. An increasing number of studies have suggested that the translocation of CED-4/Apaf-1 from mitochondria to the nuclear membrane is required to initiate and execute apoptosis [ 20 – 22 ].…”

Discovery of small molecule inhibitors for the C. elegans caspase CED-3 by high-throughput screening

“…In C.elegans , cell death is modulated by anti-apoptotic CED-9, caspase activator CED-4 and the executioner caspase CED-3 [7], with activation of CED-3 being the final step triggering apoptosis [8]. The onset of programmed cell death in C. elegans relies on a delicate interaction between CED-3, CED-4, CED-9, and EGL-1.…”

Direct pro-apoptotic role for NPM1 as a regulator of PIDDosome formation

“…For example, it was recently shown that the Caenorhabditis elegans sole caspase family member CED-3 (cell death protein 3), of which caspase-2 is the closest vertebrate relative, localizes in its inactive state in the perinuclear region of nematode germ cells. 9 Using elegant genetics and biochemistry, the Xue group demonstrated that the CED-3 zymogen engages in a direct interaction with the Nuclear Pore Protein NPP-14, which binds the CED-3 caspase recruitment domain (CARD) to prevent its association with the apoptotic protease activating factor-1 (Apaf-1) homolog, CED-4 (cell death protein 4). As a consequence, CED-3 is prevented from access to its activating platform, negating The mechanism by which DNA damage signals for NPM1-mediated PIDDosome formation is presently unclear but may involve direct phosphorylation of p53inducible protein with a death domain (PIDD) on threonine 788 (pT788) by ataxia telangiectasia mutated (ATM), which might generate a favorable confirmation for NPM1 binding to PIDD.…”

“…e1348325-2 S. SIDI AND L. BOUCHIER-HAYES apoptosis in cells destined to survive. 9 Similarly, the nucleolus may contain a potent inhibitor of PIDDosome formation, acting to prevent the caspase-2-RAIDD interaction or the RAIDD-PIDD interaction (Fig. 1B).…”