FUNCTION OF CALCITONIN RECEPTORS

猪、人和小鼠降钙素受体的克隆 (CTRS)及其结构特征分析 表明它们属于一个新的G蛋白偶联受体家族 这包括几个促胰液素/高血糖素的受体。 肽家族与甲状旁腺激素/甲状旁腺激素相关 多肽。CTR cDNA为我们提供了实验工具 定义广谱的生物和生物的分子基础 降钙素(CT)的药理作用及测定 观察到CT与相关基因交叉反应的机制 配基。CTR独特的功能特性的基础， 包括连接到多个信号转导通路的能力 而产生持续激活的腺苷酸环化酶也可以 探索过了。初步研究表明，CTR亚型和 可能是具有不同功能属性的子类型。这些发现 为具体目标1提供基础，即克隆和表征 不同CTR亚型和不同亚型的结构和功能特性 相关受体。观察到的结构和功能的异质性 我们在已经克隆的CTR cDNA中检测到 可以证明对CT反应的组织特异性调节的基础 以及相关的多肽。特定目标2将使用原位杂交技术 从CTR克隆制备的探针和免疫组织化学 CTR抗体，以确定这些抗体的组织分布 感受器。因为CTR受体家族表现出结构 与G蛋白的其他成员不同的特征- 偶联受体超家族的结构/功能关系 这些额外的克隆CTR cDNA，以定义结构决定因素 这是CTR独特的功能特性的基础。具体目标3 建议使用定点突变和构建技术 以定义与之相关的结构域 与激活相关的G蛋白的配体结合和偶联 特定的信号通路。耐火性的发展 (“逃避”)CT的低血钙效应是一个重要的问题 CT的临床和治疗应用。对机制的洞察 潜在的这种情况应该导致更有效地使用CT在 治疗骨骼重塑障碍。明确目标的目标 4将定义这种状态的分子和细胞基础 对CT的耐受性及其与过程的关系 受体脱敏和下调。

The recent cloning of porcine, human and murine calcitonin receptors (CTRs) by our laboratory and analysis of their structural features indicates that they belong to a new family of G protein-coupled receptors that includes the receptors for several members of the secretin/glucagon peptide family and parathyroid hormone/parathyroid hormone related peptide. The CTR cDNAs have provided us with experimental tools to define the molecular basis for the broad spectrum of biological and pharmacological effects of calcitonin (CT) and for determining the mechanisms underlying the observed cross-reactivity of CT with related ligands. The basis for the unique functional properties of the CTR, including the capacity to couple to multiple signal transduction pathways and to produce sustained activation of adenylate cyclase can also be explored. Initial studies indicate the presence of CTR isoforms and possibly subtypes with distinct functional properties. These findings provide the basis for Specific Aim 1 which is to clone and characterize the structural and functional properties of different CTR isoforms and related receptors. The observed structural and functional heterogeneity that we have detected among the CTR cDNAs that we have already cloned could proved the basis for tissue-specific regulation of responses to CT and related peptides. Specific Aim 2 will use in situ hybridization with probes prepared from the CTR clones and immunohistochemistry with antibodies to the CTR, to establish the tissue distribution of these receptors. Because the CTR family of receptors exhibits structural features that are different from the other members of the G protein- coupled receptor super family, the structure/function relationships for these additional clone CTR cDNAs, to define the structural determinants underlying the unique functional properties of the CTR. Specific Aim 3 proposes to use techniques of site-directed mutagenesis and construction of chimeric receptors to define the structural domains associated with ligand binding and coupling to G proteins associated with activation of specific signaling pathways. The development of refractoriness ("escape") to the hypocalcemic effects of CT is a significant problem in the clinical and therapeutic use of CT. Insights into the mechanisms underlying this condition should lead to more effective use of CT in the treatment of disorders of skeletal remodeling. The goal of Specific Aim 4 will be to define the molecular and cellular basis of this state of refractoriness to CT and to establish its relationship to the processes of receptor desensitization and down-regulation.