JUN Kinase Signaling in the Lung

描述(由申请人提供)：小的GTP酶Ras蛋白在细胞外信号传递中发挥重要作用，该信号调节细胞的生长、存活和分化。生长因子和细胞因子通过募集蛋白质激活RAS，如SOS，SOS作为鸟嘌呤核苷酸交换因子，将失活的GDP-RAS转化为活性的GTP-RAS。RAS然后将信号传递到下游的信号通路，如丝裂原激活蛋白(MAP)激酶通路。MAPK通路由Raf、MEK和MAP三种蛋白激酶组成。这些激酶通过磷酸化级联反应转导RAS信号。MAPK包括c-jun-NH2末端激酶(JNK)、细胞外调节蛋白激酶(ERK)和p38。这些MAPK调节多种转录因子的表达，这些转录因子调节细胞的生长、存活和分化。在酵母双杂交实验中，我们克隆了一种新的JNK相互作用蛋白，我们称之为RAS信号调节蛋白(RSM)。我们发现，生长因子和肿瘤坏死因子-α诱导RSM的磷酸化，导致RSM与SOS和Raf的联系。这有两个重要的结果，促进了SOS介导的RAS的激活，随后RAS激活了Raf，导致ERK激活的幅度和持续时间增加。氧化应激激活JNK途径导致细胞凋亡，而ERK途径保护细胞免于凋亡，我们观察到RSM保护成纤维细胞免受肿瘤坏死因子-α诱导的细胞凋亡。在肺部，氧化应激可诱导伤口成纤维细胞的凋亡。因此，丹参可能通过激活ERK通路，抑制JNK活性，对富含丹参的肺成纤维细胞的氧化应激损伤具有保护作用。此外，ERK通路介导了生长因子诱导的成纤维细胞的增殖和迁移，这是伤口愈合的关键过程，因此RSM可能增强肺成纤维细胞对生长因子的增殖和迁移反应。我们认为RSM是RAS途径中一个动态的分子支架蛋白。我们建议的研究将研究RSM如何调节RAS信号转导，并影响肺成纤维细胞对氧化应激的反应。我们提出了三个目标：(1)分析RSM在JNK途径中的作用；(2)表征RSM激活Raf/ERK途径的机制；(3)检测RSM在肺成纤维细胞中的功能。这些研究将阐明一种新颖而独特的RAS信号转导调节因子的生物学功能。

DESCRIPTION (provided by applicant): The small GTPase Ras proteins play an essential role in transducing extracellular signals that regulate cell growth, survival, and differentiation. Growth factors and cytokines activate Ras by recruiting proteins such as Son of Sevenless (SOS), which acts as guanine nucleotide exchange factors and converts inactive GDP-Ras to active GTP-Ras. Ras then transmits signals to downstream signaling pathways such as the mitogen-activated protein (MAP) kinase pathway. The MAPK pathway is composed of three protein kinases- Raf, MEK and MAP kinase. These kinases transduce Ras signals through a phosphorylation cascade. The MAPKs include c-Jun-NH2-terminal kinase (JNK), extracellular-regulated kinase (ERK) and p38. These MAPK regulate expression of diverse transcription factors that regulate cell growth, survival, and differentiation. From a yeast two-hybrid assay, we cloned a novel JNK-interacting protein that we call Ras Signaling Modifier (RSM). We find that growth factors and TNF-alpha induce phosphorylation of RSM leading to the association of RSM with Sos and Raf. This has two important consequences, the facilitation of Sos-mediated activation of Ras followed by Ras activation of Raf leading to an enhanced magnitude and duration of ERK activation. Oxidative stress activates the JNK pathway causing apoptosis while the ERK pathway protects cells from apoptosis and we observed that RSM protects fibroblasts from TNF-alpha-induced apoptosis. In the lung, oxidative stress has been shown to induce apoptosis of wound fibroblasts. Therefore, RSM may protect against oxidative stress injury in lung fibroblasts, which express abundant RSM, by activating the ERK pathway and inhibiting JNK activation. In addition, the ERK pathway mediates growth factor-induced proliferation and migration of fibroblasts, processes that are critical for wound healing so that RSM may augment the proliferative and migratory response to growth factors in lung fibroblasts. We view RSM as a dynamic molecular scaffolding protein in the Ras pathway. Our proposed studies will examine how RSM regulates Ras signal transduction and affects the response of lung fibroblasts to oxidative stress. We put forth three Aims: (1) Analysis of RSM in the JNK pathway; (2) Characterize the mechanism of RSM activation of the Raf/ERK pathway; and (3) Examine RSM function in lung fibroblasts. These studies will elucidate the biological function of a novel and unique regulator of Ras signal transduction.