TAK1 Regulation of TGF-beta and IL-1 signaling

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DESCRIPTION (provided by applicant): Cytokines play important roles in human development and disease. Specificity and cross-talk of cytokine signaling pathways appear to be important for fine-tuning stress responses and cell fate decision during development. Transforming growth factor beta (TGF-beta) is involved in cell growth, differentiation, tissue remodeling, immune response and angiogenesis. Interleukin 1 (IL-1) pathway plays a central role in the generation of inflammatory responses. We have found that both TGF-beta and IL-1 activate TGF-beta activated kinase 1 (TAK1) MAPKKK. Active form of TAK1 can enhance both TGF-beta- and IL-l-dependent transcription. In response to IL-1 stimulation, TAK1 activates transcription factors AP-1 and NF-KappaB. While TGF-6 stimulation does activate TAK1, the role of TAK1 in TGF-beta signaling pathway is not known. Recently, we found that TAK1 associates with a transcriptional repressor SnoN, a negative regulator of TGF-beta signaling. TAK1 induces degradation of SnoN. We hypothesize that TGF-beta activates TAK1 to induce phosphorylation of SnoN and targets SnoN for proteasomal degradation, thereby up-regulating TGF-b signal transduction. In addition, we hypothesize that TGF-beta and IL-1 activate TAK1 in distinct manner via specific scaffold/regulatory proteins to induce their unique cellular responses. Thus, the overall objectives of this proposal are; to delineate the pathway and functional role of TAK1 in TGF-beta signaling and to elucidate the mechanisms through which TAK1 regulates signal pathway specificity. To accomplish these objectives and to test our hypotheses we will: i) determine the mechanism and role of TAK1-induced SnoN degradation in TGF-b signaling pathway; ii) isolate and characterize molecules associated with TAK1 and iii) generate a skin specific knockout of TAK1 to characterize the in vivo role of TAK1 in a tissue in which TGF-beta play important roles. These studies will address unsolved questions regarding the mechanisms of TGF-beta and IL-1 family signaling and will provide an understanding of the physiological function of TAK 1 in vivo.