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FLASH coordinates NF-kappa B activity via TRAF2
1Department of Life Science, Kwangju Institute of Science and Technology, Puk-gu, Kwangju 500-712, Korea.
Abstract:
FLASH is a protein recently shown to interact with the death effector domain of caspase-8 and is likely to be a component of the death-inducing signaling complex in receptor-mediated apoptosis. Here we show that antisense oligonucleotide-induced inhibition of FLASH expression abolished TNF-alpha-induced activation of NF-kappaB in HEK293 cells, as determined by luciferase reporter gene expression driven by a NF-kappaB responsive promoter. Conversely, overexpression of FLASH dose-dependently activated NF-kappaB, an effect suppressed by dominant negative mutants of TRAF2, NIK, and IKKalpha, 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 FLASH (HeLa/HA-FLASH). Furthermore, serial deletion mapping demonstrated that a domain spanning the residues 856-1191 of FLASH activated NF-kappaB as efficiently as the full-length and could directly bind to TRAF2 in vitro and in the transfected cells. Taken together, these results suggest that FLASH coordinates downstream NF-kappaB activity via a TRAF2-dependent pathway in the TNF-alpha signaling.
Insights
The FLASH protein regulates the NF-kappaB pathway activation, crucial for tumor necrosis factor-alpha (TNF-alpha) signaling. Inhibiting FLASH blocks TNF-alpha-induced NF-kappaB activation, while its overexpression enhances it via TRAF2.
Area of Science:
- Cellular biology
- Molecular signaling
- Immunology
Background:
- The FLASH protein interacts with caspase-8 and is involved in apoptosis.
- Tumor necrosis factor-alpha (TNF-alpha) signaling activates the NF-kappaB pathway.
- Understanding FLASH's role in TNF-alpha signaling is crucial for cellular regulation.
Purpose of the Study:
- To investigate the role of FLASH in TNF-alpha-induced NF-kappaB activation.
- To elucidate the molecular mechanism by which FLASH influences NF-kappaB signaling.
- To identify interacting partners of FLASH in the TNF-alpha pathway.
Main Methods:
- Antisense oligonucleotide-induced inhibition of FLASH expression.
- Overexpression of FLASH and dominant-negative mutants.
- Luciferase reporter gene assay for NF-kappaB activity.
- Co-immunoprecipitation and in vitro binding assays.
Main Results:
- FLASH inhibition abolished TNF-alpha-induced NF-kappaB activation.
- FLASH overexpression dose-dependently activated NF-kappaB.
- FLASH directly interacts with TRAF2, a key signaling intermediate.
- A specific domain of FLASH (residues 856-1191) mediates NF-kappaB activation and TRAF2 binding.
Conclusions:
- FLASH plays a significant role in coordinating NF-kappaB activity downstream of TNF-alpha.
- The FLASH-TRAF2 interaction is critical for this regulation.
- FLASH acts as a molecular link in the TNF-alpha signaling pathway, influencing NF-kappaB activation via TRAF2.