TGF-beta signaling in the kidney

背景：转化生长因子-β1是一种多效性细胞因子，它控制多种细胞功能，包括细胞增殖、分化、凋亡和细胞外基质(ECM)的合成。转化生长因子-β1是细胞外基质蛋白合成和积累的有效诱导剂，在进展性疾病的发病机制中起着关键作用，是包括肾脏在内的各种组织中纤维化形成的中心介质。然而，肾纤维化和进展为终末期肾功能衰竭的确切机制仍不完全清楚。我们以前的研究主要集中在p38丝裂原活化蛋白激酶(MAPK)，这是一个主要的应激信号转导途径，在肾细胞中被转化生长因子-β1迅速激活。我们已经确定MKK3是一种直接上游的MAPK，在小鼠肾小球系膜细胞和肾小管上皮细胞中激活p38MAPK，并由转化生长因子-β1刺激原-A1(L)胶原。我们的假设是，MKK3-p38α和p38 Delta MAPK信号转导通路是组织损伤反应的关键介质，在此过程中，转化生长因子-β1信号合成和积聚ECM，导致进行性肾纤维化。本研究将重点研究转化生长因子-β1信号转导的细胞和分子机制，并进一步研究MKK3-p38MAPK信号通路上游激活因子对转化生长因子-β1的作用，探讨其在体外培养的肾小管上皮细胞损伤反应中的作用。体内的相关性将在肾脏纤维化的实验模型中寻找。我们将使用最先进的方法，包括各种显性负突变的转化生长因子-β受体，MAPK和特定的p38亚型，利用由短干扰RNA(SiRNA)诱导的RNAi(RNA干扰)的基因沉默，以及基因改变的小鼠，各种MAPK，特别是MKK3的缺失小鼠。相关性：尽管转化生长因子-β1在肾纤维化发展中的核心作用已被充分证明，但不加区别地完全抑制转化生长因子-β1作用的一般策略可能被证明是轻率的。这项研究将为我们进一步了解转化生长因子-β1信号转导的分子机制提供重要而新颖的信息，即我们可能能够选择性地阻断信号转导转化生长因子-β1有害作用的途径。

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.