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Measuring G-protein-coupled Receptor Signaling via Radio-labeled GTP Binding
Published on: June 9, 2017
在患有内分泌功能增加和丧失的患者中,Gsα的快速GDP释放
T Iiri1, P Herzmark, J M Nakamoto
1Department of Pharmacology, University of California, San Francisco 94143-0450.
Nature
|September 8, 1994
概括
一个新的Gsα子单元突变通过构成性地激活腺酸环酶,导致测试毒性和类型Ia的伪副类甲状腺症. 这种突变导致激素独立的激素分泌和在体温下Gs活性受损.
科学领域:
- 内分泌学 在内分泌学.
- 分子生物学分子生物学
- 遗传学 是一个遗传学.
背景情况:
- 化激素 (LH) 通过G蛋白Gs和adenylyl cyclase刺激莱迪格细胞中的激素的产生.
- 测试毒素症是一种早期青春期的形式,涉及LH独立的激素分泌,通常是由于黄素化激素受体或Gs通路突变.
- 类型Ia (PHP-Ia) 的伪低甲状腺症的特征是激素抵抗 (例如甲状腺激素,甲状腺刺激激素) 和减少Gs活性.
研究的目的:
- 在两个不相关的男孩身上,研究一种罕见的测试毒素症和PHP-Ia组合的分子基础.
- 为了阐明在这些患者中发现的特定Gsα子单元突变的功能后果.
主要方法:
- 基因分析以确定Gsα子单元基因中的突变.
- 试验室内研究,以评估表达突变的Gsα子单元的培养细胞中的腺环酶活性和cAMP积累.
- 对突变的Gsα子单元的温度稳定性测试.
主要成果:
- 在这两名患者的Gsα子单元基因中发现了一种突变,用氨酸 (alpha s-A366S) 取代366位的氨酸.
- 阿尔法s-A366S突变构成性地激活了adenylyl cyclase,导致荷尔蒙独立的cAMP积累,并解释了测试毒素化表型.
- 阿尔法s-A366S蛋白在丸温度下稳定,但在37°C下迅速降解,因Gs活性丧失而导致PHP-Ia表型.
结论:
- 阿尔法s-A366S突变对毒性和PHP-Ia的双重表型负责.
- 突变的Gsα子单位的加速GDP释放是其构成性活动和热可溶性的基础.
- 这项研究强调了Gs蛋白功能和温度敏感性在不同内分泌通路中的关键作用.
相关概念视频
GTPases and their Regulation
Guanine nucleotide-binding proteins (G-proteins), also known as GTPases, are a superfamily of proteins that regulate many cellular processes, such as cell signaling, vesicular transport, and the regulation of cell shape and motility. Mutation or dysfunction of these proteins can lead to disease. There are around 40,000 known G-proteins that can broadly be classified into two groups ‒ small G-proteins consisting of a single domain and large multi-domain G-proteins.
Large G-proteins, also known...
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Three regulatory proteins control their activity:
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Activation and Inactivation of G Proteins
Heterotrimeric G proteins are guanine nucleotide-binding proteins. As the name suggests, heterotrimeric G proteins are composed of three subunits: alpha, beta, and gamma. They remain GDP-bound or GTP-bound inside the cells and switch between inactive/active states. The Gα subunit possesses the nucleotide-binding pocket that binds guanine nucleotides and switches between GDP or GTP-bound states. In contrast, the Gꞵ and Gγ subunits are always bound together with high affinity and are together...
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Some GPCRs transmit signals through adenylyl cyclase (AC), a transmembrane enzyme. AC helps synthesize second messenger cyclic adenosine monophosphate (cAMP). AC catalyzes cyclization reaction and converts ATP to cAMP by releasing a pyrophosphate. The pyrophosphate is further hydrolyzed to phosphate by the enzyme pyrophosphatase, which drives cAMP synthesis to completion. However, cAMP is rapidly degraded to 5′ AMP by the enzymes phosphodiesterase (PDE), preventing overstimulation of cells.
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Major Hormones and Their Functions
Hormones, the biochemical messengers produced by endocrine glands, are pivotal in regulating bodily functions and maintaining homeostasis. Each hormone's balance is crucial; imbalances can lead to significant physiological disruptions. Major hormones include oxytocin, cortisol, epinephrine, estrogen, testosterone, thyroxine, growth hormone, insulin, and glucagon.
Oxytocin, produced in the hypothalamus and released by the pituitary gland, plays a role in social bonding, childbirth, and lactation.
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