Adiponectin signaling and regulation

描述(申请人提供)：脂联素/Acrp30是最近发现的一种脂肪组织衍生激素，具有抗糖尿病和胰岛素增敏功能。脂联素信号是如何从其受体转导并在细胞中调节的，目前尚不清楚。为了鉴定脂联素受体下游相互作用的分子，我们以脂联素受体1的胞内部分(AdipoR1)为诱饵，筛选了酵母双杂交文库。这一筛选导致了APPL-1的鉴定，APPL-1是一种包含磷酸酪氨酸结合PTB结构域、Pleckstrin同源(PH)结构域和亮氨酸拉链基序的接头蛋白，是一种AdipoR1相关蛋白。APPL-1在体外和哺乳动物细胞中与AdipoR1相互作用。重要的是，APPL-1的过表达促进了AMP激活的蛋白激酶(AMPK)和p38丝裂原激活的蛋白激酶(MAPK)的磷酸化，两者都被证明介导了脂联素刺激的脂肪酸氧化和葡萄糖摄取。这些新的发现表明，AdipoR1和APPL-1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。APPL-1是迄今为止发现的唯一与脂联素受体结合的细胞内信号分子。为了验证这一假说，我们将：1)确定调控APPL-1和AdipoR1之间相互作用的分子机制；2)表征APPL-1刺激p38MAPK磷酸化的生化机制以及APPL-1在脂联素刺激的p38MAPK激活和下游功能中的功能作用；3)阐明APPL-1刺激AMPK磷酸化的生化机制并表征APPL-1在脂联素刺激的AMPK激活和下游功能中的功能作用。这些研究的结果不仅将有助于我们了解脂联素信号通路及其调控，还将为设计治疗肥胖症和2型糖尿病等临床重要疾病的新药物干预措施提供有价值的信息。

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.