Regulation of JNK Signaling by Dual Specificity Phosphatases in Adipocytes

描述（由申请人提供）：肥胖和糖尿病是世界范围内重要的医疗保健问题，困扰着数百万人，导致神经病变、心血管疾病、高血压和中风。肥胖和2型糖尿病发病率的上升，尤其是在儿童中，引起了未来对经济和患者护理资源的关注，这些资源将是照顾这些患有严重影响生活质量和预期寿命的衰弱性并发症的个人所必需的。越来越多的实验和临床证据表明，c- Jun n -末端激酶（JNK）信号通路是肥胖脂肪积累和胰岛素抵抗上升导致糖尿病之间的关键联系。虽然关于上游事件激活JNK信号的作用已经了解了很多，但关于该途径的失活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）在调节JNK去磷酸化和氧化应激条件下导致脂肪细胞胰岛素敏感性丧失的功能后果中的机制作用。在初步研究中，我们证明在氧化应激条件下，JNK的磷酸化程度在未分化的前脂肪细胞和胰岛素应答的脂肪细胞之间存在显著差异，JNK在持续刺激下通过涉及RNA和蛋白质合成的机制迅速去磷酸化。并且dusp在基因表达水平上受到显著调节，这与介导JNK激活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，JNK的区隔活化和功能是通过脂肪细胞表型特异性的特异性dusp调节来控制的。我们将从两个方面检验中心假设。首先确定DUSPs在脂肪细胞中调节JNK活性的机制作用。第二项研究探讨了DUSPs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来保护胰岛素抵抗。一旦我们了解了DUSPs如何调节脂肪细胞中的JNK信号传导，预计将有可能调节这种调节，以达到治疗肥胖和糖尿病及相关并发症的目的。

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.