TGF-beta signaling in the kidney

背景：转化生长因子- β 1 （TGF-B1）是一种多效细胞因子，控制多种细胞功能，包括细胞增殖、分化、凋亡和细胞外基质（ECM）合成。TGF-B1是ECM蛋白合成和积累的有效诱导剂，作为包括肾脏在内的多种组织中纤维形成的中心介质，在进行性疾病的发病机制中起关键作用。然而，肾纤维化的发病机制和终末期肾功能衰竭的确切机制仍不完全清楚。我们之前的研究主要集中在p38丝裂原活化蛋白激酶（MAPK）上，这是肾细胞中一个主要的应激信号转导途径，可被TGF-B1快速激活。在小鼠系膜细胞和小管上皮细胞中，我们发现MKK3是激活p38 MAPK和TGF-B1刺激原a1(1)胶原所需的直接上游MAPK激酶。我们的假设是，MKK3-p38 α和p38 δ MAPK信号转导通路是组织损伤反应的关键介质，其中TGF-B1信号ECM合成和积累导致进行性肾纤维化。本课题将重点研究TGF-B1信号通路的细胞和分子机制，并进一步研究TGF-B1 MKK3-p38 MAPK信号通路上游激活因子，并在体外研究其在肾小管上皮细胞损伤反应中的功能作用。体内相关性将在肾纤维化的实验模型中寻找。我们将采用最先进的方法，包括TGF-B受体的各种显性阴性突变体，mapk和特定p38亚型，使用短干扰RNA （siRNA）诱导的RNAi （RNA干扰）进行基因沉默，以及转基因小鼠，各种mapk的空小鼠，特别是MKK3。相关性：尽管TGF-B1在肾纤维化发展中的核心作用已被充分证明，但不加选择地抑制TGF-B1作用的一般策略可能被证明是不谨慎的。本提案中的研究将为进一步了解TGF-B1信号转导的分子机制提供重要的新信息，我们可能能够选择性地阻断TGF-B1有害作用的信号通路。

DESCRIPTION (provided by applicant): Background: Transforming growth factor-beta 1 (TGF-B1) is a pleiotropic cytokine which controls multiple cellular functions including cell proliferation, differentiation, apoptosis, and extracellular matrix (ECM) synthesis. TGF-B1 is a potent inducer of ECM protein synthesis and accumulation, and plays a key role in the pathogenesis of progressive diseases as a central mediator of fibrogenesis in a variety of tissues, including the kidney. However, the precise mechanisms responsible for the pathogenesis of renal fibrosis and progression to end-stage renal failure remain incompletely understood. Our previous studies have focused on the p38 mitogen-activated protein kinase (MAPK), a major stress signal transducing pathway that is rapidly activated by TGF-B1 in renal cells. We have identified MKK3 as the immediate upstream MAPK kinase required for activation of p38 MAPK and stimulation of pro-a1(l) collagen by TGF-B1 in murine mesangial cells and tubular epithelial cells. Our hypothesis is that the MKK3-p38 alpha and p38 delta MAPK signal transduction pathway is the critical mediator of tissue injury response in which TGF-B1 signals ECM synthesis and accumulation leading to progressive renal fibrosis. This proposal will focus on examining the cellular and molecular mechanism of TGF-B1 signaling, and we will further investigate the upstream activators of MKK3-p38 MAPK signaling pathway for TGF-B1, and examine their functional role in injury responses in renal tubular epithelial cells in vitro. In vivo correlates will be sought in an experimental model of renal fibrosis. We will employ state-of-the art approaches including a variety of dominant negative mutants of TGF-B receptors, the MAPKs and specific p38 isoforms, gene silencing by the use of RNAi (RNA interference) induced by short interfering RNA (siRNA), and genetically altered mice, the null mice for the various MAPKs, particularly the MKK3. Relevance: Although the central role of TGF-B1 in the development of renal fibrosis is well documented, general strategies to indiscriminately inhibit TGF-B1 actions altogether may prove to be imprudent. The studies in this proposal will yield important and novel information in furthering our understanding of the molecular mechanisms of TGF-B1 signal transduction, that we may be able to selectively block the pathway that signals the deleterious effects of TGF-B1.