FUNCTION OF CALCITONIN RECEPTORS

猪、人和鼠降钙素受体的克隆 （CTR）的结构特征进行了分析 表明它们属于一个新的G蛋白偶联受体家族 包括胰泌素/胰高血糖素几个成员的受体 肽家族与甲状旁腺激素/甲状旁腺激素相关 肽。 CTR cDNA为我们提供了实验工具， 定义了广谱生物学和 降钙素（CT）的药理学作用，并确定 观察到的CT与相关的 配体。 CTR独特功能特性的基础， 包括与多个信号转导途径偶联的能力 并产生腺苷酸环化酶的持续激活， 探讨了 初步研究表明CTR亚型的存在， 可能是具有不同功能特性的亚型。 这些发现 为具体目标1提供基础，具体目标1是克隆和表征 不同CTR同种型的结构和功能特性， 相关受体 观察到的结构和功能异质性 我们在已经克隆的CTR cDNA中检测到的 可以证明组织特异性调节对CT的反应的基础 和相关肽。 Specific Aim 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的抗体，以建立这些抗体的组织分布。 受体。 因为CTR受体家族表现出结构上的 与G蛋白其他成员不同的特征 偶联受体超家族，结构/功能关系， 这些额外的克隆CTR cDNA，以定义结构决定簇， 这是CTR独特功能特性的基础。 具体目标3 建议使用定点诱变和构建技术 嵌合受体的结构域，以确定与 与G蛋白的配体结合和偶联， 特定的信号通路。 耐火材料的发展 （"逃避"）CT的低钙效应是一个重要的问题， CT的临床和治疗应用。 深入了解机制 这种情况的基础应该导致更有效地使用CT在 治疗骨骼重塑疾病。 具体目标的目标 4将是定义这种状态的分子和细胞基础， CT的不应性，并建立其与过程的关系 受体脱敏和下调的过程。

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.