Membrane Curvature Revisited the Archetype of Rhodopsin Studied by Time-Resolved Electronic Spectroscopy
Membrane Curvature Revisited the Archetype of Rhodopsin Studied by Time-Resolved Electronic Spectroscopy
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DOI：
10.1016/j.bpj.2020.11.007
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发表时间：
2021-02-02
影响因子：
3.4
通讯作者：
Brown, Michael F.
中科院分区：
文献类型：
--
作者：
Fried, Steven D. E.;Lewis, James W.;Brown, Michael F.
g蛋白偶联受体（gpcr）是最大和最具药理针对性的膜蛋白家族。在这里，我们使用视紫红质作为原型来理解膜脂对参与GPCR激活的构象变化的影响。用含磷酸胆碱（PC）或磷酸乙醇胺（PE）取代基的1-棕榈酰-2-油基-sn-甘油和1,2-二油基-sn-甘油磷脂，将视紫红质与酰基链不饱和程度和极性头基大小不同的脂质进行重组。利用时间分辨紫外-可见光谱学测量光激发后受体的激活谱。我们发现，更饱和的POPC脂类将平衡移回非活性状态，而小头基团、高度不饱和的DOPE脂类则倾向于活性状态。增加不饱和度和减小头基团大小具有相似的效果，它们结合起来产生对视紫红质活化的控制，并且需要蛋白脂溶剂化能和双层表面静电以外的因素。因此，我们考虑了曲率自由能与疏水匹配的平衡，并展示了我们的数据如何支持蛋白质和脂质之间耦合的柔性表面模型（FSM）。FSM是基于helrich的膜弯曲能公式，我们之前首次应用于脂质-蛋白质相互作用。膜弹性和弯曲应变是由组成脂质之间的侧压不平衡引起的，并在膜水平上驱动关键的生理过程。自发的负单层向水弯曲是由不饱和的小头基脂质介导的，并在紫红质吸收光后直接与GPCR激活结合。据我们所知，我们首次使用时间分辨方法在平衡和预平衡演化状态下证明了这种调制。
G-protein-coupled receptors (GPCRs) comprise the largest and most pharmacologically targeted membrane protein family. Here, we used the visual receptor rhodopsin as an archetype for understanding membrane lipid influences on conformational changes involved in GPCR activation. Visual rhodopsin was recombined with lipids varying in their degree of acyl chain unsaturation and polar headgroup size using 1-palmitoyl-2-oleoyl-sn-glycero- and 1,2-dioleoyl-sn-glycerophospholipids with phosphocholine (PC) or phosphoethanolamine (PE) substituents. The receptor activation profile after light excitation was measured using time-resolved ultraviolet-visible spectroscopy. We discovered that more saturated POPC lipids back shifted the equilibrium to the inactive state, whereas the small-headgroup, highly unsaturated DOPE lipids favored the active state. Increasing unsaturation and decreasing headgroup size have similar effects that combine to yield control of rhodopsin activation, and necessitate factors beyond proteolipid solvation energy and bilayer surface electrostatics. Hence, we consider a balance of curvature free energy with hydrophobic matching and demonstrate how our data support a flexible surface model (FSM) for the coupling between proteins and lipids. The FSM is based on the Helfrich formulation of membrane bending energy as we previously first applied to lipid-protein interactions. Membrane elasticity and curvature strain are induced by lateral pressure imbalances between the constituent lipids and drive key physiological processes at the membrane level. Spontaneous negative monolayer curvature toward water is mediated by unsaturated, small-headgroup lipids and couples directly to GPCR activation upon light absorption by rhodopsin. For the first time to our knowledge, we demonstrate this modulation in both the equilibrium and pre-equilibrium evolving states using a time-resolved approach.