HORMONE REGULATED GTP-BINDING PROTEINS

可逆的G蛋白亚基相互作用将被研究以确定 这些蛋白质的性质对调节荷尔蒙的作用很重要。G 蛋白质是由α、β组成的异源三聚体GTP结合蛋白 和伽马亚基。它们通过质膜传递信号。 许多荷尔蒙和神经递质以及许多 其他调节性物质。外部信号激活内部G蛋白 通过刺激依赖GTP的α亚基解离细胞 从它们相关的Betagamma二聚体中。那么G蛋白的这些部分 独立控制细胞内的信号通路，使细胞 对环境中的信号做出适当的反应。在这种情况下的错误 信号系统可能是疾病过程的贡献者，例如 糖尿病、高血压和癌症。基于这样一个事实： 某些激素需要非常特殊的G蛋白亚型组合才能 它们的作用，假设G蛋白亚单位的解离和 激素信号传递过程中的重新结合提供了一种关键机制 协调细胞反应。例如，如果G蛋白亚基形成 瞬间或动态的异三聚体络合物，激素才能 当含有正确亚基的G蛋白被激活时 现在时。为了验证这一假说，贝塔格玛二聚体的区域 将确定结合G蛋白α亚基，该信息将 可用于建立灵敏和通用的G蛋白激活检测方法 通过完整的膜和细胞中的受体。这样做的具体目的是 应用范围：1)。确定…的结构和多样性 G蛋白杂三聚体中自然产生的伽马亚基。(2)。至 确定β亚基的翻译后修饰 G蛋白。3)。使用1)和2)中的信息来定义区域 在参与β-二聚体与α结合的G蛋白亚基中 亚单位。4)。确定G蛋白异源三聚体是否由 细胞内特定的亚基组合和可逆亚单位 解离产生改变亚基组成的杂三聚体。5)。 确定G蛋白亚基的发生、调节和功能 荧光标记多肽在完整膜中的解离 基于具体目标1-3中的工作。这些研究将测试 G蛋白亚基组成改变改变荷尔蒙的假说 细胞的反应。不管这一假设的真实性如何，这些 研究将确定G蛋白的性质，这些蛋白对 调节它们的荷尔蒙的作用。

Reversible G protein subunit interactions will be studied to determine the properties of these proteins important for mediating hormone action. G proteins are heterotrimeric GTP binding proteins composed of alpha, beta and gamma subunits. They mediate signalling across the plasma membranes of cells for many hormones and neurotransmitters, as well as for numerous other regulatory substances. External signals activate G proteins inside cells by stimulating GTP-dependent dissociation of their alpha subunit from their associated betagamma dimer. These parts of the G protein then independently control signalling pathways inside cells so that the cells respond appropriately to signals in their environment. Errors in such signalling systems are likely contributors to disease processes such as diabetes, essential hypertension and cancer. Based upon the fact that some hormones require very specific G protein isoform combinations for their effects, it is hypothesized that G protein subunit dissociation and reassociation during hormone signalling provides a key mechanism for coordinating cell responses. For example, if G protein subunits form transient or dynamic heterotrimeric complexes, hormones will only be able to stimulate cells when G proteins containing the correct subunits are present. To test this hypothesis the regions of betagamma dimers that bind G protein alpha subunits will be identified and this information will be used to develop sensitive and general assays for G protein activation by receptors in intact membranes and cells. The Specific Aims of this application are: 1). To determine the structure and diversity of naturally occurring gamma subunits in G protein heterotrimers. (2). To determine the post-translational modifications of the beta subunits of the G proteins. 3). To use the information from 1) and 2) to define regions in G protein subunits involved in the binding of betagamma dimers to alpha subunits. 4). To determine if G protein heterotrimers are formed of specific subunit combinations in cells and whether reversible subunit dissociation produces heterotrimers of changing subunit composition. 5). To determine the occurrence, regulation and function of G protein subunit dissociation in intact membranes using fluorescently-labeled peptides based upon the work in Specific Aims 1-3. These studies will test the hypothesis that changing G protein subunit composition alters hormonal responses of cells. Regardless of the validity of this hypothesis, these studies will define the properties of the G proteins important for the action of the hormones that regulate them.