Adiponectin signaling and regulation

描述（由申请人提供）：脂联素/Acrp30是一种最近发现的脂肪组织来源的激素，具有抗糖尿病和胰岛素增敏功能。脂联素信号如何从其受体转导并在细胞中调节目前尚不清楚。为了鉴定脂联素受体下游的相互作用分子，我们以脂联素受体1 （AdipoR1）的细胞内部分为诱饵，筛选了酵母双杂交cDNA文库。通过筛选，我们鉴定出了appl1，一个包含磷酸酪氨酸结合PTB结构域、Pleckstrin同源结构域（PH）和亮氨酸拉链基序的接头蛋白，作为adipor1相关蛋白。在体外和哺乳动物细胞中，appl1与AdipoR1相互作用。重要的是，appl1的过表达刺激了AMP活化蛋白激酶（AMPK）和p38丝裂原活化蛋白激酶（MAPK）的磷酸化，这两者都被证明介导脂联素刺激的脂肪酸氧化和葡萄糖摄取。这些新发现表明，AdipoR1和appl1之间的相互作用可能是脂联素结合及其下游事件之间缺失的一环，而appl1是迄今为止鉴定出的唯一与脂联素受体结合的细胞内信号分子。为了验证这一假设，我们将：1)确定调节appl1和AdipoR1相互作用的分子机制；2)表征appl1刺激p38 MAPK磷酸化的生化机制，以及appl1在脂联素刺激的p38 MAPK活化和下游功能中的功能作用；3)阐明appl1刺激AMPK磷酸化的生化机制，表征appl1在脂联素刺激AMPK活化及其下游功能中的功能作用。这些研究结果不仅有助于我们对脂联素信号通路及其调控的理解，而且还将为肥胖和2型糖尿病等临床重要疾病的新药物干预设计提供有价值的信息。

DESCRIPTION (provided by applicant): Adiponectin/Acrp30 is a recently identified adipose tissue-derived hormone with anti-diabetic and insulin sensitizing functions. How the adiponectin signal is transduced from its receptor and regulated in cells is currently unknown. To identify interacting molecules downstream of the adiponectin receptor, we screened a yeast two-hybrid cDNA library using the intracellular portion of the adiponectin receptor 1 (AdipoR1) as bait. This screening led to the identification of APPL-1, an Adaptor protein containing a Phosphotyrosine binding PTB) domain, a Pleckstrin homology (PH) domain, and a Leucine zipper motif, as an AdipoR1-associated protein. APPL-1 interacted with AdipoR1 in vitro and in mammalian cells. Importantly, overexpression of APPL-1 stimulated phosphorylation of AMP activated protein kinase (AMPK) and p38 mitogen activated protein kinase (MAPK), both of which have been shown to mediate adiponectin-stimulated fatty acid oxidation and glucose uptake. These novel findings suggest that the interaction between AdipoR1 and APPL-1, the only intracellular signaling molecule identified so far that binds to the adiponectin receptor, may be the missing link between adiponectin binding and its downstream events. To test this hypothesis, we will: 1) Define the molecular mechanisms that regulate the interaction between APPL-1 and AdipoR1; 2) Characterize the biochemical mechanism by which APPL-1 stimulates p38 MAPK phosphorylation and the functional role of APPL-1 in adiponectin-stimulated p38 MAPK activation and downstream function; 3) Elucidate the biochemical mechanism by which APPL-1 stimulates AMPK phosphorylation and characterize the functional role of APPL-1 in adiponectin-stimulated AMPK activation and downstream function. Results from these studies will not only shed light on our understanding of the adiponectin signaling pathway and its regulation, but will also provide valuable information on the design of new pharmacological interventions for clinically important diseases such as obesity and Type 2 Diabetes.