Caspase-2 primes cancer cells for TRAIL-mediated apoptosis by processing procaspase-8.
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Shin S, Lee Y, Kim W, Ko H, Choi H, Kim K
Caspase-2 primes cancer cells for TRAIL-mediated apoptosis by processing procaspase-8.
EMBO J. 2005 Oct 19;24(20):3532-42. Epub 2005 Sep 29.
- PubMed ID
- 16193064 [ View in PubMed]
- Abstract
Although caspase-2 is believed to be involved in death receptor-mediated apoptosis, the exact function, mode of activation, and regulation of caspase-2 remain unknown. Here we show that protein kinase (PK) CK2 phosphorylates procaspase-2 directly at serine-157. When intracellular PKCK2 activity is low or downregulated by specific inhibitors, procaspase-2 is dephosphorylated, dimerized, and activated in a PIDDosome-independent manner. The activated caspase-2 then processes procaspase-8 monomers between the large and small subunits, thereby priming cancer cells for TNF-related apoptosis-inducing ligand (TRAIL)-mediated apoptosis. The processed procaspase-8 that is recruited to death-inducing signaling complex by TRAIL engagement becomes fully activated, and cancer cells undergo apoptosis. PKCK2 activity is low in TRAIL-sensitive cancer cell lines but high in TRAIL-resistant cancer cell lines. Thus, downregulating PKCK2 activity is required for TRAIL-mediated apoptosis to occur in TRAIL-resistant cancer cells. Our data provide novel insights into the regulation, mode of activation, and function of caspase-2 in TRAIL-mediated apoptosis.