Regulation of JNK Signaling by Dual Specificity Phosphatases in Adipocytes

描述(由申请人提供)：肥胖和糖尿病是全球范围内严重的医疗保健问题，困扰着数百万人，导致神经疾病、心血管疾病、高血压和中风。肥胖症和2型糖尿病发病率的上升，特别是在儿童中的发病率上升，引起了人们对未来财政和患者护理资源的担忧，这些资源将是护理这些患有严重影响生活质量和预期寿命的衰弱并发症所必需的。越来越多的实验和临床证据表明，c-Jun氨基末端激酶(JNK)信号通路是肥胖引起的脂肪堆积和导致糖尿病的胰岛素抵抗增加之间的关键环节。虽然关于激活JNK信号的上游事件的作用已经了解很多，但关于失活这一途径的机制及其对生物学结果的影响的信息却很少。本应用的目的是确定双特异性磷酸酶(DUSPs)在氧化应激条件下调节JNK去磷酸化和功能后果的机制作用，氧化应激导致脂肪细胞对胰岛素的敏感性丧失。在初步研究中，我们证明了在氧化应激条件下，未分化前脂肪细胞和胰岛素反应性脂肪细胞中JNK的磷酸化程度明显不同，在持续刺激存在的情况下，JNK通过涉及RNA和蛋白质合成的机制迅速去磷酸化，并且DUSPs在基因表达水平上受到显著调控，这与JNK激活程度的表型差异相一致。基于这些数据，我们提出了一个中心假设，即JNK对氧化应激的反应是通过以脂肪细胞表型特异性的方式调节特定的DUSP来控制的。我们将在两个目标上检验中心假说。第一个决定了DUSPs在调节脂肪细胞JNK活性中的机制作用。第二部分研究了DUSP如何通过形成一个将JNK激活与JNK去磷酸化联系起来的调节反馈环路来提供对胰岛素抵抗的保护。一旦我们了解了DUSP如何调节脂肪细胞中的JNK信号，就有望调节这种调节，以达到治疗肥胖和糖尿病及相关并发症的目的。 公共卫生相关性：肥胖和糖尿病发病率的上升已被普遍确定为所有发达国家最重要的健康问题之一。尽管被认为是所有慢性病流行病中最昂贵和最可预防的，但近1.8亿美国人超重，5400万人患有糖尿病前期，2000万糖尿病患者。虽然已经证实JNK信号通路的激活是胰岛素抵抗发生发展的重要一步，但在以失活这一途径的机制为中心的知识库中存在着一个关键的缺口，该途径提供了保护与糖尿病相关的胰岛素敏感性丧失的机制。这项拟议的研究将在导致胰岛素抵抗的条件下，建立脂肪细胞中蛋白磷酸酶和JNK活性之间的功能关系。了解减弱JNK活性的机制以及与肥胖和糖尿病之间的联系的相关性的积极影响将是显著的。

DESCRIPTION (provided by applicant): Obesity and diabetes mellitus are significant healthcare concerns worldwide that afflict millions of individuals leading to neuropathies, cardiovascular disease, hypertension, and stroke. The rising incidence of obesity and type 2 diabetes, especially among children, raises future concerns in regards to financial and patient care resources that will be necessary to care for these individuals with debilitating complications that dramatically affect quality of life as well as life expectancy. Mounting experimental and clinical evidence has established c- Jun N-terminal kinase (JNK) signaling pathways as a critical link between the accumulation of fat mass with obesity and the rise of insulin resistance contributing to diabetes. While much has been learned concerning the role of upstream events that activate JNK signaling, little information has emerged regarding mechanisms that deactivate this pathway and their effect on biological outcome. The objectives of this application is to determine the mechanistic role of dual specificity phosphatases (DUSPs) in regulating JNK dephosphorylation and functional consequences under conditions of oxidative stress that lead to a loss of insulin sensitivity in adipocytes. In preliminary studies, we demonstrate that the extent of JNK phosphorylation is markedly different between undifferentiated preadipocytes and insulin-responsive adipocytes under conditions of oxidative stress, that JNK is dephosphorylated rapidly in the presence of continuing stimuli through mechanisms involving RNA and protein synthesis, and that DUSPs are dramatically regulated at the level of gene expression consistent with a role in mediating the phenotypic difference in the extent of JNK activation. Based on these data, we developed the central hypothesis that compartmentalized JNK activation and function in response to oxidative stress is controlled via regulation of specific DUSPs in an adipocyte phenotype-specific manner. We will test the central hypothesis in two aims. The first determines the mechanistic role of DUSPs in regulating JNK activity in adipocytes. The second examines how DUSPs afford protection against insulin resistance by forming a regulatory feedback loop linking JNK activation with JNK dephosphorylation. Once we understand how DUSPs regulate JNK signaling in adipocytes, it is expected that it will become possible to modulate that regulation for the therapeutic purpose of treating obesity and diabetes and associated complications. PUBLIC HEALTH RELEVANCE: The rising incidence of obesity and diabetes has been universally established as among the most important health concerns of all developed nations. Although consider the most costly and preventable of all chronic disease epidemics, nearly 180 million Americans are overweight and 54 million are pre-diabetic in addition to 20 million with diabetes. While it is has been established that activation of JNK signaling is an important step in the development of insulin resistance, there is a critical gap in the knowledge base that centers on mechanisms which deactivate this pathway affording protection against the loss of insulin sensitivity associated with diabetes. The proposed research will establish functional relationship between protein phosphatases and JNK activity in adipocytes under condition leading to insulin resistance. The positive impact of understanding mechanisms that attenuate JNK activity and the relevance to the link between obesity and diabetes will be significant.