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的重大医疗保健问题，困扰着数百万人，导致神经病变、心血管疾病、高血压和中风。肥胖症和2型糖尿病的发病率不断上升，特别是在儿童中，引起了未来对财务和患者护理资源的关注，这些资源对于照顾这些患有严重影响生活质量和预期寿命的衰弱并发症的人是必要的。越来越多的实验和临床证据已经确立了c-Jun N-末端激酶（JNK）信号传导途径作为伴随肥胖的脂肪量积累与导致糖尿病的胰岛素抵抗的上升之间的关键联系。虽然已经了解了很多关于上游事件的作用，激活JNK信号转导，很少有信息已经出现的机制，使这一途径失活，其对生物学结果的影响。本申请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中的机制作用，所述氧化应激条件导致脂肪细胞中胰岛素敏感性丧失。在初步研究中，我们证明了在氧化应激条件下，JNK磷酸化的程度在未分化的前脂肪细胞和胰岛素反应性脂肪细胞之间显著不同，JNK在持续刺激的存在下通过涉及RNA和蛋白质合成的机制快速去磷酸化，并且DUSPs在基因表达水平上受到显著调节，这与介导JNK活化程度的表型差异的作用一致。基于这些数据，我们提出了一个中心假设，即在氧化应激反应中，区室化的JNK激活和功能是通过以脂肪细胞表型特异性方式调节特定的DUSPs来控制的。我们将从两个方面检验中心假设。第一个确定了DUSPs在调节脂肪细胞中JNK活性中的机制作用。第二个研究DUSPs如何通过形成连接JNK活化与JNK去磷酸化的调节反馈环来提供针对胰岛素抵抗的保护。一旦我们了解了DUSPs如何调节脂肪细胞中的JNK信号传导，预计将有可能调节该调节以治疗肥胖和糖尿病及其相关并发症。 公共卫生相关性：肥胖症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，另外还有2000万人患有糖尿病。虽然已经确定JNK信号传导的激活是胰岛素抵抗发展中的重要步骤，但是在以使该途径失活的机制为中心的知识基础中存在关键的空白，该机制提供针对与糖尿病相关的胰岛素敏感性丧失的保护。该研究将建立蛋白磷酸酶和JNK活性在导致胰岛素抵抗的条件下在脂肪细胞中的功能关系。了解JNK活性减弱的机制以及肥胖和糖尿病之间联系的相关性将产生重大的积极影响。

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.