JUN Kinase Signaling in the Lung

描述（由申请人提供）：小GTPase Ras蛋白在传导调节细胞生长、存活和分化的细胞外信号中起重要作用。生长因子和细胞因子通过募集诸如seven - less之子（SOS）之类的蛋白来激活Ras，这些蛋白作为鸟嘌呤核苷酸交换因子，将不活跃的GDP-Ras转化为活跃的GTP-Ras。Ras随后将信号传递到下游信号通路，如丝裂原活化蛋白激酶通路。MAPK通路由三种蛋白激酶- Raf、MEK和MAP激酶组成。这些激酶通过磷酸化级联转导Ras信号。MAPKs包括c- jun - nh2末端激酶（JNK）、细胞外调节激酶（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生长、存活和分化。从酵母双杂交实验中，我们克隆了一种新的jnk相互作用蛋白，我们称之为Ras信号修饰因子（RSM）。我们发现生长因子和tnf - α诱导RSM磷酸化，导致RSM与Sos和Raf相关。这有两个重要的结果，促进sos介导的Ras激活，随后Ras激活Raf，导致ERK激活的强度和持续时间增强。氧化应激激活JNK通路导致细胞凋亡，而ERK通路保护细胞免于凋亡，我们观察到RSM保护成纤维细胞免于tnf - α诱导的凋亡。在肺中，氧化应激已被证明可诱导伤口成纤维细胞凋亡。因此，RSM可能通过激活ERK通路和抑制JNK激活来保护表达丰富RSM的肺成纤维细胞免受氧化应激损伤。此外，ERK通路介导生长因子诱导的成纤维细胞增殖和迁移，这一过程对伤口愈合至关重要，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通路中的动态分子支架蛋白。我们提出的研究将探讨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JNK通路中的RSM；(2)表征RSM激活Raf/ERK通路的机制；(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的、独特的Ras信号转导调节剂的生物学功能。

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.