FUNCTION AND REGULATION OF SOMATOSTATIN RECEPTORS

生长抑素受体的功能和调节

• 批准号: 2734017
• 负责人: AGNES SCHONBRUNN
• 金额: $ 25.43万
• 依托单位: UNIVERSITY OF TEXAS HLTH SCI CTR HOUSTON
• 依托单位国家: 美国
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-07-01 至 2000-07-14
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2734017
• 关键词: G protein; RNase protection assay; cell type; hormone receptor; hormone regulation /control mechanism; immunoprecipitation; laboratory rabbit; messenger RNA; northern blottings; peptide hormone analog; phosphorylation; polymerase chain reaction; protein isoforms; protein structure function; receptor binding; receptor coupling; receptor expression; receptor sensitivity; second messengers; somatostatin; tissue /cell culture; western blottings

Somatostatin (SRIF) is a neuropeptide which acts as a hormone, a neurotransmitter or an autocrine regulator to inhibit secretion and/or proliferation in endocrine, exocrine, neuronal and tumor cells. SRIF has been implicated in numerous physiological processes ranging from growth to memory as well as in several disorders including endocrine cancers and Alzheimer's disease. The biological actions of this peptide are initiated by binding to plasma membrane receptors which are coupled to effector enzymes and ion channels via o proteins. Recently five related SRIF receptor (sstr) genes have been identified by molecular cloning. These sstr subtypes are believed to serve unique biological roles by virtue of their tissue specific expression and particular biochemical properties. However, we do not understand the function of any individual sstr in its normal cellular milieu. Such studies have been difficult because SRIF- responsive tissues and cell lines often express multiple sstr's and, in the absence of subtype specific SRIF analogs, the actions of individual receptors cannot be identified. Moreover, sstr function depends on cellular environment so that the behavior of a receptor expressed in heterologous cells does not necessarily mimic that of endogenous receptors. This proposal has two overall goals: (l) characterize the signal transduction mechanisms activated by sstr subtypes, and (2) elucidate the mechanisms involved in the regulation of sstr's. In the last award period, we developed several receptor antibodies each of which immunoprecipitates the corresponding sstr subtype specifically. Moreover, we developed conditions such that the G-proteins coupled to sstr's in membranes remain receptor associated in the immunoprecipitate. We propose to characterize the G proteins coupled to each sstr subtype in different target cells by immunoprecipitating each receptor and identifying the associated G protein subunits with G protein specific antisera. We will therefore determine how cellular milieu affects the specificity of sstr-G protein coupling. Further, we will use biochemical and electrophysiological techniques to identify the effectors regulated by individual receptor subtypes in different target cells. We also propose to examine the mechanisms involved in sstr desensitization and regulation. Some SRIF responses are rapidly desensitized whereas others are not. Moreover, we have shown that sstr's are subject to chronic regulation by several different hormones. We propose to determine how specific hormonal treatments alter the expression of different sstr subtype mRNAs and proteins. In addition, we will examine the role of receptor phosphorylation in SRIF desensitization. Together these studies will elucidate the cellular mechanisms by which SRIF induces its biological actions and will identify the molecular basis for hormone induced changes in cellular responsiveness to SRIF.

生长抑素（SRIF）是一种神经肽，它作为一种激素， 神经递质或自分泌调节剂以抑制分泌和/或 内分泌、外分泌、神经元和肿瘤细胞中的增殖。SRIF有 与许多生理过程有关，包括生长 以及包括内分泌癌在内的多种疾病， 老年痴呆症这种肽的生物学作用是由 通过与质膜受体结合，所述质膜受体与效应物偶联， 酶和通过蛋白质的离子通道。最近五个相关的SRIF 受体（SSTR）基因已经通过分子克隆鉴定。这些 SSTR亚型被认为具有独特的生物学作用， 它们的组织特异性表达和特定的生物化学性质。 然而，我们并不了解任何一个单独的sstr在其 正常的细胞环境这些研究一直很困难，因为SRIF- 应答组织和细胞系通常表达多个SSTR， 缺乏亚型特异性SRIF类似物，个体的作用 受体无法识别。此外，sstr函数依赖于 细胞环境，从而使表达的受体的行为 异源细胞不一定模仿内源细胞 受体。该提案有两个总体目标：（l） 由SSTR亚型激活的信号转导机制，和（2） 阐明参与调节SSTR的机制。在 在上一个授标期间，我们开发了几种受体抗体， 特异性免疫沉淀相应的SSTR亚型。此外，委员会认为， 我们开发了这样的条件，即G蛋白与SSTR的偶联， 膜保持与免疫沉淀物相关的受体。我们提出 为了表征不同sstr亚型中与每个sstr亚型偶联的G蛋白， 通过免疫沉淀每种受体并鉴定 相关的G蛋白亚单位与G蛋白特异性抗血清。我们将 从而确定细胞环境如何影响sstr-G的特异性 蛋白质偶联此外，我们将使用生物化学和 电生理学技术来识别受 不同靶细胞中的单个受体亚型。我们亦建议 研究sstr脱敏的机制， 调控一些SRIF反应迅速脱敏，而另一些反应则迅速脱敏。 并不是。此外，我们已经表明，sstr的是受慢性 由几种不同的激素调节。我们建议确定如何 特定的激素治疗改变了不同的sstr的表达， 亚型mRNA和蛋白质。此外，我们还将研究 SRIF脱敏中的受体磷酸化。这些研究 将阐明SRIF诱导其表达的细胞机制。 生物作用，并将确定激素的分子基础 诱导细胞对SRIF反应性的变化。