Role of FLASH in Receptor-mediated Apoptosis and Coordinatation of NF-ĸB Activity via TRAF2

다국어 초록 (Multilingual Abstract)

FLASH is a protein recently shown to interact with the death effector domain(DED) of caspase-8 and is likely to be a component of the death-inducing signaling complex(DISC) in receptor-mediated apoptosis. Here we show that anti-sense oligonucleotide-induced inhibition of FLASH expression abolished TNF-induced activation of NF-ĸB in HEK293 cells, as determined by luciferase-reporter gene expression driven by a NF-ĸB-responsive promoter. Conversely, overexpression of FLASH dose-dependently activated NF-ĸB, an effect suppressed by dominant negative mutants of TRAF2, NIK, and IKK, and partially by those of TRAF5 and TRAF6. TRAF2 was co-immunoprecipitated with FLASH from the cell extracts of HEK293 cells or HeLa cells stably expressing exogenous FALSH(HeLa/HA-FLASH). Furthermore, serial deletion mapping demonstrated that a domain spanning the residues 856-1191 of FLASH(NAD) activated NF-ĸB as efficiently as the full-length and could directly bind to TRAF2 in vitro and in the transfected cells. These results suggest that FLASH coordinates downstream NF-ĸB activity via a TRAF2-dependent pathway in the TNF- signaling. Further, we will show and discuss that caspase-8 is involved in the receptor-mediated activation of NF-ĸB through FLASH.