Structure and Function of the LH, FSH, and TSH Receptors

描述(申请人提供)：黄体生成素、卵泡刺激素和促甲状腺激素受体，统称为糖蛋白激素受体(GPH-R‘s)，组成视紫红质样G蛋白偶联受体(GPCR’s)的一个独特的亚家族。它们每个都由一个大的结合激素的胞外结构域和一个与G蛋白(主要是Gs)偶联的七个跨膜(TM)结构域组成。每一种受体的活性状态都通过激素的结合或通过诱导结构性活性的离散突变来稳定。这项资助的目的是确定GPH-R激活的结构基础。通常，我们将使用两种实验方法，每种方法都将与分子建模相结合。第一种方法利用破坏性和互换突变来检验这一假设，即在三个GPH-R中高度保守的TM残基参与螺旋间相互作用，从而稳定处于静息状态的受体。第二种方法使用来自给定物种或来自不同物种的给定GPH-R的不同GPH-R之间的选择性嵌合体突变来检验这样的假设，即某些不同的TM残基通过影响螺旋间相互作用来调节GPH-R的活性。尽管GPH-R的TM区具有高度的氨基酸同一性，但某些GPH-R对的基础活性、突变诱导或激素诱导的激活程度明显不同。通过在两个不同性质的相关GPH-R之间交换发散的TM残基，我们可以保持受体的整体完整性(因为发散的残基能够维持整体结构)，并确定赋予或多或少活性的精确氨基酸。计算机建模将与这些实验策略中的每一个相结合，以帮助数据解释和定义那些在静息状态、突变诱导的活动状态和激素稳定的活动状态下稳定GPH-R的螺旋间相互作用。这一建议的具体目的是：1.确定GPH-R的保守残基在维持受体的静止状态中所起的作用。2.确定GPH-R休止态的不同构造活性的结构基础。3.通过激活突变，确定GPH-R的不同易感性被稳定在激活状态的结构基础。4.确定GPH-R不同程度激活Gs的结构基础。

DESCRIPTION (provided by applicant): The LH, FSH and TSH receptors, collectively known as the glycoprotein hormone receptor (GPH-R's), comprise a unique subfamily of rhodopsin-like G protein-coupled receptors (GPCR's). They are each composed of a large extracellular domain that binds hormone and a seven transmembrane (TM) domain that couples to G proteins, primarily Gs. The active states of each of these receptors are stabilized by the binding of hormone or by discrete mutations that induce constitutive activity. The aims of this grant are to determine the structural basis for the activation of the GPH-R's. In general, we will use two experimental approaches, each of which will be coupled with molecular modeling. The first approach utilizes disruptive and reciprocal mutagenesis to test the hypothesis that TM residues that are highly conserved in the three GPH-R's participate in interhelical interactions that stabilize the receptors in the resting state. The second approach uses selective chimera mutagenesis between different GPH-R's from a given species or from a given GPH-R of different species to test the hypothesis that certain divergent TM residues modulate the activities of the GPH-R's by affecting interhelical interactions. In spite of the high degree of amino acid identity in the TM regions of the GPH-R's, certain pairs of GPH-R's exhibit markedly different degrees of basal activity, mutation-induced, or hormone-induced activation. By interchanging the divergent TM residues between two related GPH-R's with differing properties, we can maintain the overall integrity of the receptor (because the divergent residues are capable of maintaining the overall structure) and determine the precise amino acids that confer the greater or lesser degree of activity. Computer modeling will be coupled with each of these experimental strategies to aid in data interpretation and to define those interhelical interactions that stabilize the GPH-R's in the resting states, in mutation-induced active states, and in hormone-stabilized active states. The specific aims of this proposal are: 1. Determine the roles that conserved residues of the GPH-R's have in maintaining the resting states of the receptors. 2. Determine the structural basis for the different degrees of constitutive activity of the resting states of the GPH-R's. 3. Determine the structural basis for the different susceptibilities of the GPH-R's to be stabilized in an active state by activating mutations. 4. Determine the structural basis for the different degrees of hormone-stimulated Gs activation by GPH-R's.