Identification of ARTS-1 as a novel TNFR1-binding protein that promotes TNFR1 ectodomain shedding

Abstract

death domain association produces a platform for the recruitment of additional signaling molecules (3).TRADD recruitment of Fas-associated death domain mediates caspase activation and apoptosis, while recruitment of receptor-interacting protein and TNFRassociated factor 2 activates NF-B and AP-1 signaling pathways that mediate the transcription of proinflammatory, immunoregulatory, and antiapoptotic genes.TNFR1-mediated events can be modified by proteolytic cleavage and shedding of cell-surface TNF receptors.Soluble TNF receptors function as TNF-binding proteins that compete with cell-surface TNF receptors, thereby decreasing TNF bioactivity (4).TNF receptor shedding may also decrease the number of cell-surface receptors available for ligand binding.Soluble TNF receptors can also reversibly bind to and stabilize soluble trimeric TNF ligand (5).Subsequent dissociation of TNF from soluble TNF receptors may replenish the soluble TNF ligand pool, with the complex serving as a reservoir for release of TNF when levels are low.Therefore, soluble TNF receptors may serve a buffering function, attenuating TNF bioactivity when levels are elevated and reconstituting TNF when levels have declined (5).In this study, we sought to identify proteins regulating TNFR1 ectodomain shedding.We reasoned that such proteins might be identified via a yeast two-hybrid approach using the extracellular domain of human TNFR1 as a bait fusion protein to screen a human lung