Molecular mechanisms of IL-1R-TLR mediated signaling

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The goal of Project 1 is to understand the molecular mechanisms by which interleukin (IL)-IR-toll-like receptor (TLR) signaling modulates the development and pathogenesis of atherosclerosis. Genetic and biochemical studies by us and others revealed that IL-1R-TLRs induce TAK1 (TGFp-activated kinase 1)- and MEKK3 (MAP kinase kinase kinase 3)-dependent pathways, involving cascades of kinases organized by multiple adapter molecules into parallel and sequential signaling complexes, leading to activation of the transcription factor NFkB. IL-1R-TLRs also mediate mRNA stabilization of cytokines and chemokines, which is essential for effective inflammatory response. We have recently shown that IL-1R-TLR-mediated TAK1- dependent NFkB activation is coupled with the mRNA stabilization pathway to induce the robust production of cytokines and chemokines. On the other hand, the IL-1-R-TLR-mediated MEKKS-dependent pathway is uncoupled from mRNA stabilization pathway and is only able to induce expression of genes that are not regulated by mRNA stability (including inhibitory molecules A20 and IkBa), exerting an overall inhibitory effect on inflammatory gene expression. Based on these findings, we hypothesize that IL-1R-TLRs trigger inflammatory response by coupling TAK1-dependent NFkB activation with mRNA stabilization pathway to induce robust production of cytokines and chemokines. The IL-1R-TLR-mediated MEKK3-dependent NFkB activation pathway is inhibitory to the overall inflammatory response by uncoupling gene transcription from mRNA stabilization and by producing inhibitory signaling molecules that turn down production of cytokines and chemokines. To test this hypothesis, we propose to elucidate the molecular mechanisms that coordin- ately regulate IL-1R-TLR-induced TAK1-dependent NFkB activation and mRNA stabilization pathways (Aim 1); delineate molecular mechanisms for IL-1R-TLR-induced MEKKS-dependent NFkB activation and its role in uncoupling gene transcription from mRNA stabilization (Aim 2); and investigate the patho-physiological functions of IL-1R-TLR-induced TAK1- versus MEKKS-dependent NFkB activation and mRNA stability signaling cascades in the development of atherosclerosis (Aim 3). RELEVANCE (See instructions): NfkB is an important factor that regulates the inflammatory response in macrophages. Our studies will elucidate a new mechanism that will help to explain how NFkB regulates the onset, progression, and resolution of inflammation in vascular diseases such as atherosclerosis. Our long-term objective is to develop more effective anti-inflammatory and anti-atherogenic small molecule drugs.