LAMININ GENE EXPRESSION IN GLOMERULAR CELLS

描述（申请人提供）：肾小球硬化是进行性肾脏疾病最严重的后遗症。肾小球硬化是由蛋白质的异常积累引起的，其中一些蛋白质通常构成肾小球基底膜（GBM）和系膜基质（MM）。层粘连蛋白是GBM和MM的成分之一，在肾小球疾病的进展过程中在肾小球内积累。许多生长因子，包括转化生长因子- β (tgf - β)，激活肾小球细胞，导致层粘连蛋白的异常积累。虽然已知层粘连蛋白在肾小球硬化的发展中起关键作用，但调节层粘连蛋白链表达的机制尚不完全清楚。用tgf - β和其他生长因子治疗肾小球细胞可增加层粘连蛋白γ - 1链mRNA水平。人和啮齿类动物的层粘连蛋白γ -1链（LAMC1）基因启动子包含由转录因子uE3 （TFE3）激活的关键bcn-1元件。在肾小球系膜细胞中，通过LAMC1启动子的Smad结合元件（SBE）和tgf - β信号通路，Smad蛋白极大地增强了tfe3介导的bcn-1元件的激活。通过TFE3和Smad蛋白的协同作用，LAMC1启动子的bcn-1元件依赖性激活提供了tgf - β如何介导内源性LAMC1基因在这些细胞中的激活的见解。转录共激活因子CREB结合蛋白（CBP）的表达增加了系膜细胞中LAMC1启动子的活性。本研究的目标是确定肾小球细胞中tgf - β诱导的LAMC 1基因转录的TFE3和smad依赖性激活的分子机制。我们提出了以下具体目标来探索这些机制。我们将定义CBP和其他共激活剂在介导tfe3 - smad依赖性tgf - β诱导的LAMC1基因表达中的作用。我们将确定与TFE3蛋白相互作用的基础转录机制的组成部分，并确定它们在介导tgf - β诱导的基因表达中的作用。我们将定义负责TFE3-Smad3协同激活LAMC1基因响应tgf - β的分子机制。这些研究将深入了解tgf - β利用转录机制来指导肾小球细胞中TFE3和smad依赖性LAMC1基因的转录。这些研究的结果预计将对理解tgf - β触发细胞外基质和肾小球细胞中表达的其他基因编码成分的基因转录的基本机制产生广泛的影响。

DESCRIPTION (provided by applicant): Glomerulosclerosis is the most serious sequela of progressive renal disease. Glomerulosclerosis results from an abnormal accumulation of proteins, some of which, that normally make up the glomerular basement membrane (GBM) and mesangial matrix (MM). Laminin is one of the components of GBM and MM that accumulates within glomeruli during the progression of glomerular disease. A number of growth factors, including transforming growth factor-beta (TGF-beta), activate glomerular cells resulting in abnormal accumulation of laminin. Although laminin is known to play a key role in the development of glomerulosclerosis, the mechanisms that regulate expression of laminin chains are incompletely understood. Treatment of glomerular cells with TGF-beta and other growth factors increases mRNA levels of laminin gamma1 chain. The human and rodent laminin gamma1 chain (LAMC1) gene promoters contain the critical bcn-1 element that is activated by transcription factor uE3 (TFE3). In glomerular mesangial cells, the TFE3-mediated activation of the bcn-1 element is greatly augmented by Smad proteins, acting through the LAMC1 promoter's Smad binding elements (SBE), and by the TGF-beta-signaling pathways. The bcn-1-element-dependent activation of the LAMC1 promoter by the synergistic action of TFE3 and Smad proteins provides insight into how TGF-beta mediates activation of the endogenous LAMC1 gene in these cells. Expression of the transcriptional co-activator, CREB binding protein (CBP), increased the activity of the LAMC1 promoter in mesangial cells. The goal of the current proposal is to define the molecular mechanisms responsible for the TFE3- and Smad-dependent activation of LAMC 1 gene transcription that is induced by TGF-beta in glomerular cells. The following specific aims are proposed to explore these mechanisms. We will define the role of CBP and other co-activators in mediating the TFE3-Smad-dependent TGF-beta-induced LAMC1 gene expression. We will identify components of the basal transcriptional machinery that interact with TFE3 protein and define their role in mediating TGF-beta-induced gene expression. We will define the molecular mechanisms responsible for the TFE3-Smad3 synergistic activation of the LAMC1 gene in response to TGF-beta. These studies will provide insight into transcriptional mechanisms utilized by TGF-beta to direct TFE3- and Smad-dependent LAMC1 gene transcription in glomerular cells. The results of these studies are anticipated to have a broad impact on understanding the basic mechanisms by which TGF-beta triggers transcription of genes encoding components of extracellular matrix and of other genes expressed in glomerular cells.