Institute of Physical Chemistry, University of Muenster, Corrensstr. 28/30, 48149 Muenster, Germany.
Institute of Cell Dynamics and Imaging, University of Muenster, Von-Esmarch-Str. 56, 48149 Muenster, Germany.
J Phys Chem B. 2022 May 5;126(17):3240-3256. doi: 10.1021/acs.jpcb.2c00192. Epub 2022 Apr 21.
Clustering of transmembrane proteins underlies a multitude of fundamental biological processes at the plasma membrane (PM) such as receptor activation, lateral domain formation, and mechanotransduction. The self-association of the respective transmembrane domains (TMDs) has also been suggested to be responsible for the micron-scaled patterns seen for integral membrane proteins in the budding yeast PM. However, the underlying interplay between the local lipid composition and the TMD identity is still not mechanistically understood. In this work, we combined coarse-grained molecular dynamics simulations of simplified bilayer systems with high-resolution live-cell microscopy to analyze the distribution of a representative helical yeast TMD from the PM sensor Slg1 within different lipid environments. In our simulations, we specifically evaluated the effects of acyl chain saturation and anionic lipid head groups on the association of two TMDs. We found that weak lipid-protein interactions significantly affect the configuration of TMD dimers and the free energy of association. Increased amounts of unsaturated phospholipids (PLs) strongly reduced the helix-helix interaction, while the presence of anionic phosphatidylserine (PS) hardly affected the dimer formation. We could experimentally confirm this surprising lack of effect of PS using the network factor, a mesoscopic measure of PM pattern formation in yeast cells. Simulations also showed that the formation of TMD dimers in turn increased the order parameter of the surrounding lipids and induced long-range perturbations in lipid organization. In summary, our results shed new light on the mechanisms of lipid-mediated dimerization of TMDs in complex lipid mixtures.
跨膜蛋白的聚类是质膜（PM）中许多基本生物过程的基础，如受体激活、侧域形成和机械转导。各自的跨膜结构域（TMD）的自缔合也被认为是导致出芽酵母 PM 中完整膜蛋白呈现微米级图案的原因。然而，局部脂质组成与 TMD 身份之间的相互作用的机制仍不清楚。在这项工作中，我们结合简化双层系统的粗粒度分子动力学模拟和高分辨率活细胞显微镜，分析了来自 PM 传感器 Slg1 的代表性酵母 TMD 在不同脂质环境中的分布。在我们的模拟中，我们特别评估了酰基链饱和度和阴离子脂质头部基团对两个 TMD 缔合的影响。我们发现，弱的脂质-蛋白相互作用显著影响 TMD 二聚体的构象和缔合的自由能。不饱和磷脂（PL）含量的增加强烈降低了螺旋-螺旋相互作用，而阴离子磷脂酰丝氨酸（PS）的存在几乎不影响二聚体形成。我们可以使用网络因子（酵母细胞中 PM 模式形成的介观度量）实验证实 PS 缺乏这种令人惊讶的影响。模拟还表明，TMD 二聚体的形成反过来又增加了周围脂质的有序参数，并诱导了脂质组织的长程扰动。总之，我们的结果为复杂脂质混合物中 TMD 介导的二聚化的脂质机制提供了新的认识。
