CSIR-Centre for Cellular and Molecular Biology, Hyderabad 500 007, India.
Centre for Microphotonics, Faculty of Science, Engineering and Technology, Swinburne University of Technology, Hawthorn, Victoria 3122, Australia.
Faraday Discuss. 2018 Apr 1;207:409-421. doi: 10.1039/c7fd00192d. Epub 2018 Jan 23.
The oligomerization of G protein-coupled receptors (GPCRs) represents an important process in GPCR function and drug discovery. We have addressed cholesterol-dependent oligomerization state of the serotonin receptor, a representative GPCR and an important drug target, utilizing photobleaching image correlation spectroscopy (pbICS). pbICS allows determination of oligomeric state of membrane receptors since change in cluster density upon photobleaching is dependent on the oligomeric state. Our results show that oligomeric state of the serotonin receptor is modulated by cell membrane cholesterol and a trimeric population of the receptor prevails in control (normal) cholesterol conditions. Interestingly, upon lowering membrane cholesterol, the predominant oligomeric population of the receptor changes to dimers. This is associated with an increase in specific ligand binding activity of the receptor, thereby implying a crucial role of receptor dimers in ligand binding activity. Upon cholesterol replenishment, the distribution of receptor oligomers is further changed such that the trimers become the major population, with a concomitant restoration of ligand binding activity to the control level. These results demonstrate the utility of pbICS in monitoring oligomeric states of membrane receptors in general, and the cholesterol-dependent oligomeric state of the serotonin receptor in particular. We envision that functional correlates of oligomeric states of GPCRs could provide better understanding of GPCR function in health and disease, and help design better therapeutic strategies.
G 蛋白偶联受体（GPCR）的寡聚化是 GPCR 功能和药物发现的一个重要过程。我们利用光漂白图像相关光谱（pbICS）研究了血清素受体的胆固醇依赖性寡聚化状态，血清素受体是一种代表性的 GPCR，也是一个重要的药物靶点。pbICS 可用于确定膜受体的寡聚状态，因为光漂白后聚集体密度的变化取决于寡聚状态。我们的结果表明，血清素受体的寡聚状态受细胞膜胆固醇调节，在正常胆固醇条件下，受体以三聚体形式为主。有趣的是，降低膜胆固醇后，受体的主要寡聚体形式变为二聚体。这与受体的特异性配体结合活性增加有关，表明受体二聚体在配体结合活性中起关键作用。胆固醇补充后，受体寡聚体的分布进一步改变，三聚体成为主要形式，配体结合活性恢复到对照水平。这些结果表明，pbICS 可用于监测一般膜受体的寡聚状态，特别是血清素受体的胆固醇依赖性寡聚状态。我们设想，GPCR 寡聚状态的功能相关性可以更好地理解 GPCR 在健康和疾病中的功能，并有助于设计更好的治疗策略。
