Arias Hugo Rubén
Department of Pharmaceutical Sciences, Midwestern University, Glendale, AZ, USA.
Methods Mol Biol. 2010;606:291-318. doi: 10.1007/978-1-60761-447-0_20.
Electron paramagnetic resonance (EPR) spectroscopy is a powerful technique that permits the study of membrane-embedded proteins in its lipid environment by assessing the interaction of spin labels with the protein in its natural environment (i.e., native membranes) or in reconstituted systems prepared with exogenous lipid species. Nicotinic acetylcholine receptors (AChRs) contain a large surface in intimate contact with the lipid membrane. AChRs, members of the Cys-loop receptor superfamily, have essential functional roles in the nervous system and its malfunctioning has been considered as the origin of several neurological diseases including Alzheimer's disease, drug addiction, depression, and schizophrenia. In this regard, these receptors have been extensively studied as therapeutic targets for the action of several drugs. The majority of the marketed medications bind to the neurotransmitter sites, the so-called agonists. However, several drugs, some of them still in clinical trials, interact with non-competitive antagonist (NCA) binding sites. A potential location for these binding sites is the proper ion channel, blocking ion flux and thus, inhibiting membrane depolarization. However, several NCAs also bind to the lipid-protein interface, modulating the AChR functional properties. The best known examples of these NCAs are local and general anesthetics. Several endogenous molecules such as free fatty acids and neurosteroids also bind to the lipid-protein interface, probably mediating important physiological functions. Phospholipids, natural components of lipid membranes interacting with the AChR, are also essential to maintain the structural and functional properties of the AChR. EPR studies showed that local anesthetics bind to the lipid-protein interface by essentially the same dynamic mechanisms found in lipids, and that local and general anesthetics preferably decrease the phospholipid but not the fatty acid interactions with the AChR. This is consistent with the existence of annular and non-annular lipid domains on the AChR.
电子顺磁共振（EPR）光谱法是一种强大的技术，它可以通过评估自旋标记物与处于天然环境（即天然膜）或由外源性脂质种类制备的重构系统中的蛋白质之间的相互作用，来研究脂质环境中膜嵌入蛋白。烟碱型乙酰胆碱受体（AChRs）具有与脂质膜紧密接触的大表面。AChRs是半胱氨酸环受体超家族的成员，在神经系统中具有重要的功能作用，其功能失调被认为是包括阿尔茨海默病、药物成瘾、抑郁症和精神分裂症在内的几种神经疾病的根源。在这方面，这些受体已被广泛研究作为几种药物作用的治疗靶点。大多数市售药物与神经递质位点结合，即所谓的激动剂。然而，几种药物，其中一些仍在临床试验中，与非竞争性拮抗剂（NCA）结合位点相互作用。这些结合位点的一个潜在位置是适当的离子通道，阻断离子通量，从而抑制膜去极化。然而，几种NCA也与脂蛋白界面结合，调节AChR的功能特性。这些NCA最著名的例子是局部和全身麻醉剂。几种内源性分子，如游离脂肪酸和神经甾体，也与脂蛋白界面结合，可能介导重要的生理功能。与AChR相互作用的脂质膜天然成分磷脂，对于维持AChR的结构和功能特性也至关重要。EPR研究表明，局部麻醉剂通过与脂质中发现的基本相同的动态机制与脂蛋白界面结合，并且局部和全身麻醉剂优选减少磷脂与AChR的相互作用，而不是脂肪酸与AChR的相互作用。这与AChR上存在环状和非环状脂质结构域是一致的。
