Mukhaleva Elizaveta, Yang Tianyi, Sadler Fredrik, Sivaramakrishnan Sivaraj, Ma Ning, Vaidehi Nagarajan
Irell and Manella Graduate School of Biological Sciences, Beckman Research Institute of the City of Hope, Duarte, CA, USA.
Department of Computational and Quantitative Medicine, Beckman Research Institute of the City of Hope, Duarte, CA, USA.
bioRxiv. 2023 Nov 29:2023.11.28.569080. doi: 10.1101/2023.11.28.569080.
The structurally disordered intracellular loops (ICLs) of G protein-coupled receptors (GPCRs) play a critical role in G protein coupling. In our previous work, we used a combination of FRET-based and computational methodologies to show that the third intracellular loop (ICL3) modulates the activity and G protein coupling selectivity in GPCRs. In the current study, we have uncovered the role of several lipid components in modulating the conformational ensemble of ICL3 of the β2-adrenergic receptor (β2AR). Our findings indicate that phosphatidylinositol 4,5-bisphosphate (PIP2) in the inner leaflet of the membrane bilayer acts as a stabilizing anchor for ICL3, opening the intracellular cavity to facilitate G protein coupling. This interaction between PIP2 and ICL3 causes tilting of β2AR within the cellular membrane. Notably, this tilting of the receptor is supported by ganglioside GM3 stabilizing the extracellular loops on the outer leaflet of the bilayer, thereby exerting an allosteric effect on the orthosteric ligand binding pocket. Our results underscore the significance of lipids in modulating GPCR activity, proposing an allosteric mechanism that occurs through the receptor's orientation within the membrane.
G蛋白偶联受体（GPCRs）结构紊乱的细胞内环（ICLs）在G蛋白偶联中起关键作用。在我们之前的工作中，我们结合基于荧光共振能量转移（FRET）的方法和计算方法，证明第三细胞内环（ICL3）调节GPCRs的活性和G蛋白偶联选择性。在当前研究中，我们揭示了几种脂质成分在调节β2肾上腺素能受体（β2AR）的ICL3构象集合中的作用。我们的研究结果表明，膜双层内小叶中的磷脂酰肌醇4,5-二磷酸（PIP2）作为ICL3的稳定锚，打开细胞内腔以促进G蛋白偶联。PIP2与ICL3之间的这种相互作用导致β2AR在细胞膜内倾斜。值得注意的是，这种受体的倾斜由神经节苷脂GM3支持，GM3稳定双层外小叶上的细胞外环，从而对正构配体结合口袋产生变构效应。我们的结果强调了脂质在调节GPCR活性中的重要性，提出了一种通过受体在膜内的取向发生的变构机制。
