ANTAGONISTIC ACTION OF AGOUTI AND AGOUTI RELATED PROTEIN

哺乳动物的遗传学为研究信号和基因调控提供了一个独特的系统。α -黑素细胞刺激激素（d-MSH）、Agouti和Agouti相关蛋白（Agrp）是三种分子，当作用于至少五种不同的黑素皮质素受体（Mclr-Mc5r）时，会影响色素沉积、修饰、性行为、学习、记忆、对疼痛的反应以及体重调节。药理研究表明，Agouti/Agrp与mcr /Mc4r之间的分子相互作用与黑素皮质素与其受体之间的分子相互作用截然不同。为了进一步了解这个问题，本项目旨在确定mcr和Mc4r受体的哪些部分是拮抗剂结合所必需的，并确定受体的这些部分是否以相同的方式影响拮抗剂和激动剂的作用。具体目标包括：通过产生嵌合的Mclr和Mc4r受体来识别影响拮抗剂结合/作用的特定结构域；对于赋予Agouti或Agrp作用特异性的一个或多个结构域，将进行位点定向诱变以确定负责特异性的特定残基；突变受体还将测试它们对一系列小分子黑素皮素的结合和cAMP反应，这些小分子黑素皮素赋予每个受体独特的药理学特征；在特定情况下，将使用体内试验，使用普遍表达Agouti或Agrp的动物，以及mcr或Mc4r受体的功能丧失突变。

The genetics of mammalian provides a unique system to study signalling and gene regulation. Alpha-melanocyte stimulating hormone (d-MSH), Agouti and Agouti related protein (Agrp), are three molecules, which when acting on at least five different melanocortin receptors (Mclr-Mc5r) affect pigmentation, grooming, sexual behaviour, learning, memory, responses to pain, as well as the regulation of body weight. Pharmacological studies suggest that the molecular interaction between Agouti/Agrp and the Mclr/Mc4r is quite distinct from that between melanocortins and their receptors. To gain further insight into this question, this project aims to determine which portions of the Mclr and Mc4r receptors are required for antagonist binding and to determine if these portions of the receptors affect antagonist and agonist action in the same manner. The specific aims include: the identification of specific domain/s that affects antagonist binding/action by generating chimaeric Mclr and Mc4r receptors; for a domain or domains that confer specificity of Agouti or Agrp action, site directed mutagenesis will be carried out to identify particular residues responsible for specificity; mutant receptors will also be tested for their binding and cAMP response to an array of small molecule melanocortins, which imbue each receptor with a unique pharmacological profile; in specific cases, use will be made of an in vivo assay using animals that ubiquitously express Agouti or Agrp, and loss-of-function mutations for the Mclr or Mc4r receptors.