New principles for initiation and regulation of pattern recognition receptor signalling

Inflammation is a host response that is triggered by noxious stimuli that appear during infection and tissue injury. The recent discoveries that several families of pattern recognition receptors (PRRs) directly sense inflammatory stimuli and activate innate immune cells have greatly increased our molecular understanding of inflammatory diseases. While genetic approaches, such as gene targeting in mice, were key in defining the PRR receptors and their signalling pathways, much less is known about how the a ctivation threshold of PRR signalling is regulated by cell biological processes. Toll-like receptors (TLRs) are the most important PRRs for the control of inflammatory responses. We have combined cell biology, biochemistry and innate immunity approaches to identify and decipher the cellular machinery that initiates and regulates PRR signalling from endosomes, phagosomes and cytosol. In particular we have uncovered the trafficking routes of the TLR4 adaptor molecule TRAM and analyzed TLR2 and TLR4 trafficking to intracellular signalling compartments in which IFN-beta responses are initiated. Furthermore, we have molecularly defined the function of the UNC93B1 that regulates TLR3,7,8 and 9 trafficking to endosome to perform signalling. An important part of this project has been to establish the molecular basis for inflammasome activation. Novel and groundbreaking data were obtained that were published in Nature Immunology and PNAS. In total 18 papers have been published from this project. We have used advanced cell biological methods together with innate immune biology to reveal new PRR signalling principles. Completion of this project have contributed to identification of causes and therapeutic targets for inflammatory diseases.

Inflammation is a host response that is triggered by noxious stimuli that appear during infection and tissue injury. The recent discoveries that several families of pattern recognition receptors (PRRs) directly sense inflammatory stimuli and activate inn ate immune cells have greatly increased our molecular understanding of inflammatory diseases. While genetic approaches, such as gene targeting in mice, were key in defining the PRR receptors and their signalling pathways, much less is known about how the activation threshold of PRR signalling is regulated by cell biological processes. Toll-like receptors (TLRs) are the most important PRRs for the control of inflammatory responses. We will combine cell biology, biochemistry and innate immunity approaches t o identify and decipher the cellular machinery that initiates and regulates PRR signalling from endosomes, phagosomes and cytosol. In particular we will uncover the trafficking routes of the TLR adapter molecule TRAM and we will analyze TLR2 and TLR4 traf ficking to intracellular signalling compartments in which IFN-b responses are initiated. Furthermore, we aim to molecularly define the function of genes that regulate endosomal TLR trafficking and signalling and we will identify novel factors that act in cellular activation by nucleic acids. To achieve these goals we will elucidate key vesicle transport components that regulate TLR- and adapter trafficking and signalling from endosomes and phagosomes. An important part of this project will also be to esta blish the molecular basis for activation of the novel inflammasome, NLRP12. Within this proposal advanced cell biological methods are used and by integration of cell biology with innate immune biology a novel and unconventional approach is taken to reveal new PRR signalling principles. Successful completion of this project will contribute to identification of novel causes and therapeutic targets for inflammatory diseases.