HORMONE REGULATED GTP BINDING PROTEINS

异源三聚体G蛋白介导许多激素和神经递质以及各种其他调节剂穿过细胞质膜的信号传导。 它们是霍乱和百日咳等疾病过程的已知或可能位点，它们在细胞调节中的作用使它们可能促成糖尿病、原发性高血压和癌症等复杂疾病的病理学（如果不是病因学的话）。了解这些蛋白质在正常信号事件中的功能对于描述它们在疾病状态中的作用以及提供关于这些蛋白质作为药物干预靶点的未来可能发展的信息是至关重要的。 这项研究所基于的两个主要假设之一是，这些蛋白质广泛参与细胞信号转导取决于G蛋白亚基的巨大结构和功能多样性。 提出的研究的一个主要目标是确定亚基多样性的异源三聚体G蛋白信号转导中的作用。因此，前两个具体目标是：（1）确定G蛋白β和γ亚基结构多样性的起源和性质。 这些研究利用了与该项目相关的蛋白质化学和质谱专业知识。 (2)确定含有（a）不同β或γ亚型或（B）不同修饰的γ亚基亚型的γ β-γ二聚体之间的功能差异。这些研究主要使用分子生物学方法，将特定目标1下产生的信息应用于G蛋白亚基的生化表征。 G蛋白作用中的一个重要功能步骤是其α亚基与其相关β-γ二聚体的GTP依赖性解离。 这种反应对G蛋白介导的细胞信号传导过程具有不同的影响，这在很大程度上是由于它们的结构和功能多样性。 我们假设G蛋白亚基解离是信号转导的关键步骤，可以决定细胞对什么信号做出反应，以及这种反应的性质。 为了验证这一假设，第三个具体目标是：（3）确定完整膜和完整细胞中亚基解离的生理作用。 这些研究将专门测试特定目标1和2下表征的G蛋白亚基多样性是否被细胞利用来产生具有不同信号传导特性的G蛋白异源三聚体的变化模式。 该项目的结果将定义与这些蛋白质相关的功能多样性的潜在范围，并将其多样性定义为潜在的药物靶点。

Heterotrimeric G proteins mediate signaling across the plasma membranes of cells for many hormones and neurotransmitters, as well as for a wide variety of other regulatory agents. They are known or likely sites for disease processes such as cholera and pertussis, and their role in cellular regulation makes them likely contributors to the pathology, if not etiology, of complex diseases such as diabetes, essential hypertension and cancer. Understanding how these proteins function in normal signaling events is essential to describing their role in disease states and to providing information about the future possible development of these proteins as targets for pharmacologic intervention. One of the two main hypotheses upon which this research is based is that the widespread involvement of these proteins in cell signaling depends upon the immense structural and functional diversity of the G protein subunits. A primary objective of the proposed studies is to define the role of subunit diversity in signaling by heterotrimeric G proteins. Thus, the first two Specific Aims are: (1) To determine the origin and nature of the structural diversity of the beta and gamma subunits of G proteins. These studies take advantage of protein chemistry and mass spectrometry expertise associated with this project. (2) To determine the functional differences between Gbetagamma dimers containing (a) different beta or gamma isoforms or (b) differently modified gamma subunit isoforms. These studies use primarily molecular biology approaches to apply the information generated under Specific Aim 1 to the biochemical characterization of the G protein subunits. An important functional step in the action of G proteins is the GTP-dependent dissociation of their a subunit from their associated betagamma dimer. This reaction has diverse implications for the cellular signaling processes mediated by G proteins, in large part due to their structural and functional diversity. We hypothesize that G protein subunit dissociation is a key step in signal transduction that can determine to what signals cells respond, as well as the nature of that response. To test this hypothesis the third Specific Aim is: (3) To determine the physiological role of subunit dissociation in intact membranes and intact cells. These studies will specifically test whether the G protein subunit diversity characterized under Specific Aims 1 and 2 is utilized by cells to generate changing patterns of G protein heterotrimers with varying signaling properties. The results of this project will define the potential range of functional diversity associated with these proteins, and in so doing define their diversity as potential drug targets.