Genomic insights into the resolution of inflammation: Alternate splicing of key signalling molecules in the Toll-like receptor cascade.
The Toll-Like Receptor (Tlr) pathway is a central mediator of innate immune responses to pathogens. Tlr signalling in macrophages leads to well documented transcriptional, phenotypic and biochemical changes cumulating in inflammation. The resolution of this inflammatory signal is less well understood, but vital to limit tissue damage, sepsis and chronic inflammatory disease. Alternate splicing of key signalling molecules in the Tlr cascade has been shown to dramatically alter the signalling capacity of inflammatory cells. The production of dominant negative proteins through such splicing events has been documented for few proteins such as Irak-m and Myd88-s, yet it is not known how common this mechanism is. We exploited the FANTOM (functional annotation of the mouse genome) transcriptome dataset to systematically screen transcript variants of the Tlr cascade, Mapk, Pik3, IFN-? pathways. Two hundred and fifty six variant transcripts were identified, including novel variants of Tlr4, Ticam1, Tollip, Rac1, Irak1, 2 and 4, Mapk14/p38, Csf1r, Atf2 and Stat1. Functional annotation of variant proteins was assessed in light of inflammatory signalling in mouse primary macrophages. Splicing arrays were used to examine the expression of each variant transcript in primary and LPS-activated macrophages. We functionally tested the expression of Tlr4 transcripts under a range of cytokine conditions via Northern and qRT-PCR. The effects of variant Mapk14/p38 protein expression on macrophage activation and survival were demonstrated. Our data suggest a surprisingly common role for variant proteins in diversification/repression of inflammatory signalling.
Genomic insights into the regulation of inflammation
HISTORY AND ARCHAEOLOGY