Simple and highly sensitive assay system for TNFR2-mediated soluble- and transmembrane-TNF activity

Drugs that target tumor necrosis factor-alpha (TNF) are particularly important in the treatment of severe inflammatory progression in rheumatoid arthritis, Crohn's disease and psoriasis. Despite the central role of the TNF/TNF receptor (TNFR) in various disease states, there is a paucity of information concerning TNFR2 signaling. In this study, we have developed a simple and highly sensitive cell-death based assay system for analyzing TNFR2-mediated bioactivity that can be used to screen for TNFR2-selective drugs. Using a lentiviral vector, a chimeric receptor was engineered from the extracellular and transmembrane domain of human TNFR2 and the intracellular domain of mouse Fas and the recombinant protein was then expressed in TNFR1(-/-)R2(-/-) mouse preadipocytes. Our results demonstrate that this chimeric receptor is capable of inducing apoptosis by transmembrane- as well as soluble-TNF stimuli. Moreover, we found that our bioassay based on cell death phenotype had an approximately 80-fold higher sensitivity over existing bioassays. We believe our assay system will be an invaluable research tool for studying TNFR2 and for screening TNFR2-targeted drugs.