Functional mapping and identification of novel regulators for the Toll/Interleukin-1 signalling network by transcription expression cloning

Sustained inflammatory responses are central to the development and progression of chronic diseases, including atherosclerosis and rheumatoid arthritis. A large number of stimuli initiate inflammation by acting on Toll-Interleukin-1 related (TIR) domain containing receptors, producing multiple second messengers and thence large scale transcriptional changes. The mechanism by which this activation occurs is complex, and the continuing isolation of novel pathway components, mostly based on sequence similarities and protein-protein interaction studies, suggests that many elements of the TIR-initiated signalling network remain to be identified. Here we use a new technique, allowing identification of components based on function. We report the performance of the screen, our identification of human tribbles as a novel protein family regulating inflammatory signalling networks, and the detection of ten other components with poorly characterized roles in inflammatory signalling pathways. In total, we have identified 28 signalling molecules of diverse molecular mechanism by screening 11% of a cDNA library for the ability to modulation expression of human IL-8, and other molecules remain to be followed up. The results suggest that the number of human genes involved in IL-8 induction pathways exceed 100. The isolation of signalling components by the approach we describe allows detection of new classes of signalling components independent of existing techniques for doing so; it is simple and robust, and constitutes a general method for mapping signal transduction systems controlling gene expression.