Fas-associated factor 1, FAF1, is a member of Fas death-inducing signaling complex.
FAF1 has been introduced as a Fas-binding protein. However, the function of FAF1 in apoptotic execution is not established. Based on the fact that FAF1 is a Fas-binding protein, we asked if FAF1 interacted with other members of the Fas-death-inducing signaling complex (Fas-DISC) such as Fas-associated death domain protein (FADD) ... and caspase-8. FAF1 could interact with caspase-8 and FADD in vivo as well as in vitro. The death effector domains (DEDs) of caspase-8 and FADD interacted with the amino acid 181-381 region of FAF1, previously known to have apoptotic potential. Considering that FAF1 directly binds to Fas and caspase-8, FAF1 shows similar protein-interacting characteristics to that of FADD. In the coimmunoprecipitation with an anti-Fas antibody (APO-1) in Jurkat cells, endogenous FAF1 was associated with the precipitates in which caspase-8 was present. By confocal microscopic analysis, both Fas and FAF1 were detected in the cytoplasmic membrane before Fas activation, and in the cytoplasm after Fas activation. FADD and caspase-8 colocalized with Fas in Jurkat cells validating the presence of FAF1 in the authentic Fas-DISC. Overexpression of FAF1 in Jurkat cells caused significant apoptotic death. In addition, the FAF1 deletion mutant lacking the N terminus where Fas, FADD, and caspase-8 interact protected Jurkat cells from Fas-induced apoptosis demonstrating dominant-negative phenotype. Cell death by overexpression of FAF1 was suppressed significantly in both FADD- and caspase-8-deficient Jurkat cells when compared with that in their parental Jurkat cells. Collectively, our data show that FAF1 is a member of Fas-DISC acting upstream of caspase-8.
Mesh Terms:
Adaptor Proteins, Signal Transducing, Amino Acid Sequence, Apoptosis, Carrier Proteins, Caspase 8, Caspase 9, Caspases, Death Domain Receptor Signaling Adaptor Proteins, Fas-Associated Death Domain Protein, Humans, Jurkat Cells, Molecular Sequence Data, Protein Structure, Tertiary, Receptors, Tumor Necrosis Factor, Sequence Alignment, Signal Transduction
Adaptor Proteins, Signal Transducing, Amino Acid Sequence, Apoptosis, Carrier Proteins, Caspase 8, Caspase 9, Caspases, Death Domain Receptor Signaling Adaptor Proteins, Fas-Associated Death Domain Protein, Humans, Jurkat Cells, Molecular Sequence Data, Protein Structure, Tertiary, Receptors, Tumor Necrosis Factor, Sequence Alignment, Signal Transduction
J. Biol. Chem.
Date: Jun. 27, 2003
PubMed ID: 12702723
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