Un controlled accumulation of Type I collagen, the hallmark of scleroderma, results in fibrosis of skin and other affected organs. This process is attributed to constitutive activation of collagen gene transcription in scleroderma fibroblasts, Transforming growth factor-beta (TGF-beta), a potent stimulus for collagen synthesis, is strongly implicated in pathological fibrogenesis , whereas interferon gamma (IFN- gamma) antagonize the effects of TGF-beta and as important for prevention of scarring. Recently, SMAD and STAT1 have been identified as intracellular signal transducers of TGF-beta and IFN-gamma, respectively. However, the pathways for modulating collagen gene transcription in response to these cytokines, and the transcriptional mechanisms involved, remain poorly understood. Our laboratory has established the role of SMAD3 in TGF-beta stimulation of collagen gene regulation of Type I collagen gene transcription, and to delineate alterations that result in its constitutive up-regulation in scleroderma. To this end, building on recent insights from our laboratory relating to TGF- beta and IFN-gamma signaling in fibroblasts and the role of p300/CBP in these pathways, I propose to examine the hypothesis that these co- activators are involved in stimulation as well as inhibition of collagen transcription, and integrate antagonistic signaling to the Typ1 collagen gene promoters. The hypothesis will be tested in the following three Specific Aims: 1) to elucidate the involvement of p300/CBP in activation of Type I collagen transcription by TGF-beta in normal fibroblasts; 2) to dissect the molecular mechanisms underlying antagonistic regulation of collagen gene transcription in these cells by TGF-beta and IFN-gamma; and 3) to examine SMAD-p300/CBP co-activator interactions in scleroderma fibroblasts with constitutive up-regulation of collagen gene transcription. The pilot studies described in this application are based on recent breakthroughs in understanding TGF-beta signaling and the role of co-activators in transcriptional regulation. By enhancing our knowledge of how transcription of collagen genes is regulated in fibroblasts, these studies could ultimately lead to the design of novel therapeutic strategies to selectively modulate this process in Scleroderma.
