Role of Fox03a in Regulating the IPF Fibroblast Phenotype

描述（由申请人提供）：特发性肺纤维化（IPF）是一种进行性、致死性纤维化肺部疾病，目前尚无有效治疗方法。前哨形态病变为成纤维细胞病灶，由富含I型胶原的肌成纤维细胞组成。鉴于肌成纤维细胞是增生并在肺泡壁沉积胶原蛋白的细胞，初步证据支持肌成纤维细胞在IPF无情进展中的关键作用。尽管研究强烈支持IPF成纤维细胞表现出独特的病理表型的观点，但关于导致进行性纤维化的IPF成纤维细胞的病理性质与正常肺修复所必需的肌成纤维细胞的生理功能之间的差异，知识上仍然存在很大差距。本研究的目的是表征IPF成纤维细胞病理性质的分子过程。我们发现聚合型胶原通过高PTEN活性抑制了主要的PI3K/Akt信号通路，从而抑制了正常成纤维细胞的增殖。相反，在IPF成纤维细胞中，由于PTEN活性不适当的降低，PI3K/Akt信号被异常激活，这使得这些细胞能够避开聚合胶原的增殖抑制特性。我们获得的数据表明，在IPF成纤维细胞中，活化的PI3K/Akt信号抑制FoxO3a转录激活因子的功能。FoxO3a调控细胞周期抑制蛋白p27和凋亡诱导蛋白Bim，这两个蛋白分别参与细胞增殖和存活的控制。我们的机制研究指出，整合素介导的FoxO3a磷酸化和/或降解是IPF成纤维细胞中FoxO3a功能抑制的潜在原因。我们认为这种病理缺陷破坏了FoxO3a转录激活因子的功能，导致p27和Bim的抑制。这可能使IPF成纤维细胞具有超增殖和抗凋亡表型。为了验证我们的假设，我们将：目标1。检验异常激活的PI3K/Akt通路抑制IPF成纤维细胞中FoxO3a转录激活因子功能的假设。目标2。探讨FoxO3a在聚合胶原上调控IPF成纤维细胞增殖和存活的功能作用及机制。目标3。研究激活的整合素/PI3K/Akt信号通路抑制IPF成纤维细胞FoxO3a功能的分子机制。公共卫生相关性：特发性肺纤维化（IPF）是一种慢性、致死性间质性肺疾病。前哨形态病变为成纤维细胞病灶，由包埋在富含I型胶原的基质中的成纤维细胞组成。聚合型胶原抑制正常成纤维细胞增殖的机制涉及维持高PTEN活性，抑制PI3K/Akt信号通路。然而，在IPF成纤维细胞中，由于PTEN活性低，PI3K/Akt信号异常激活，使这些细胞能够避开聚合胶原的增殖抑制特性。我们获得的数据表明，在IPF成纤维细胞中，活化的Akt抑制FoxO3a转录激活因子的功能。FoxO3a调节参与控制细胞增殖和存活的关键蛋白的表达。我们认为FoxO3a功能的破坏可能使IPF成纤维细胞具有超增殖和抗凋亡表型。确定控制IPF成纤维细胞病理行为的关键调控节点可能为限制IPF特征的进行性纤维化提供分子治疗靶点。确定控制IPF成纤维细胞病理行为的关键调控节点可能为限制IPF特征的进行性纤维化提供分子治疗靶点。

DESCRIPTION (provided by applicant): Idiopathic Pulmonary Fibrosis (IPF) is a progressive, fatal fibrotic lung disease for which there is no effective therapy. The sentinel morphological lesion is the fibroblastic focus, which is composed of myofibroblasts in a type I collagen rich matrix. Prima facie evidence supports the critical role for myofibroblasts in the relentless progression of IPF given that this is the cell that proliferates and deposits collagen in the alveolar wall. Although studies strongly support the notion that IPF fibroblasts display a distinct pathological phenotype, large gaps in knowledge remain regarding differences between the pathological nature of IPF fibroblasts responsible for progressive fibrosis and the physiologic function of myofibroblasts essential for normal lung repair. The objective of this proposal is to characterize the molecular processes underlying the pathological nature of IPF fibroblasts. We have discovered that polymerized type I collagen suppresses normal fibroblast proliferation via high PTEN activity which inhibits the major PI3K/Akt signaling pathway. In contrast, in IPF fibroblasts, the PI3K/Akt signal is aberrantly activated due to inappropriately low PTEN activity and this permits these cells to elude the proliferation suppressive properties of polymerized collagen. We have generated data indicating that in IPF fibroblasts, the activated PI3K/Akt signal inhibits the function of the FoxO3a transcriptional activator. FoxO3a regulates the cell cycle inhibitor protein p27 and apoptosis inducing protein Bim, two critical proteins involved in the control of cell proliferation and survival, respectively. Our mechanistic studies point to integrin-mediated phosphorylation and/or degradation of FoxO3a as the underlying cause of suppression of FoxO3a function in IPF fibroblasts. We suggest that this pathological defect disrupts the function of the FoxO3a transcriptional activator leading to suppression of p27 and Bim. This may confer IPF fibroblasts with a hyper-proliferative and apoptotic-resistant phenotype. To test our hypothesis we will: Aim 1.Examine the hypothesis that the abnormally activated PI3K/Akt pathway suppresses the function of the FoxO3a transcriptional activator in IPF fibroblasts. Aim 2. Examine the functional role and mechanism of FoxO3a regulation of IPF fibroblast proliferation and survival on polymerized collagen. Aim 3. Examine the molecular mechanism by which the activated integrin/PI3K/Akt signaling pathway suppresses FoxO3a function in IPF fibroblasts. PUBLIC HEALTH RLEVANCE: Idiopathic pulmonary fibrosis (IPF) is a chronic, lethal interstitial lung disease. The sentinel morphological lesion is the fibroblastic focus, which is composed of fibroblasts embedded in a type I collagen rich matrix. Polymerized type I collagen suppresses normal fibroblast proliferation by a mechanism involving maintenance of high PTEN activity which inhibits the PI3K/Akt signal pathway. However, in IPF fibroblasts the PI3K/Akt signal is aberrantly activated due to low PTEN activity, permitting these cells to elude the proliferation suppressive properties of polymerized collagen. We have generated data indicating that in IPF fibroblasts, activated Akt inhibits the function of the FoxO3a transcriptional activator. FoxO3a regulates the expression of critical proteins involved in the control of cell proliferation and survival. We suggest that disruption of the function of FoxO3a may confer IPF fibroblasts with a hyper-proliferative and apoptotic-resistant phenotype. Identifying key regulatory nodes controlling the pathologic behavior of IPF fibroblasts may provide molecular therapeutic targets to limit the progressive fibrosis that characterizes IPF. Identifying key regulatory nodes controlling the pathologic behavior of IPF fibroblasts may provide molecular therapeutic targets to limit the progressive fibrosis that characterizes IPF.