Honigmann Alf, Sadeghi Sina, Keller Jan, Hell Stefan W, Eggeling Christian, Vink Richard
Department of NanoBiophotonics, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany.
Elife. 2014 Mar 18;3:e01671. doi: 10.7554/eLife.01671.
The eukaryotic cell membrane is connected to a dense actin rich cortex. We present FCS and STED experiments showing that dense membrane bound actin networks have severe influence on lipid phase separation. A minimal actin cortex was bound to a supported lipid bilayer via biotinylated lipid streptavidin complexes (pinning sites). In general, actin binding to ternary membranes prevented macroscopic liquid-ordered and liquid-disordered domain formation, even at low temperature. Instead, depending on the type of pinning lipid, an actin correlated multi-domain pattern was observed. FCS measurements revealed hindered diffusion of lipids in the presence of an actin network. To explain our experimental findings, a new simulation model is proposed, in which the membrane composition, the membrane curvature, and the actin pinning sites are all coupled. Our results reveal a mechanism how cells may prevent macroscopic demixing of their membrane components, while at the same time regulate the local membrane composition. DOI: http://dx.doi.org/10.7554/eLife.01671.001.
真核细胞膜与富含肌动蛋白的致密皮质层相连。我们展示了荧光相关光谱（FCS）和受激发射损耗（STED）实验，结果表明致密的膜结合肌动蛋白网络对脂质相分离有严重影响。通过生物素化脂质链霉亲和素复合物（固定位点）将最小的肌动蛋白皮质层与支撑脂质双层相连。一般来说，肌动蛋白与三元膜的结合会阻止宏观的液晶相和液相无序结构域的形成，即使在低温下也是如此。相反，根据固定脂质的类型，会观察到一种与肌动蛋白相关的多结构域模式。FCS测量结果表明，在存在肌动蛋白网络的情况下，脂质的扩散受到阻碍。为了解释我们的实验结果，我们提出了一个新的模拟模型，其中膜组成、膜曲率和肌动蛋白固定位点都是相互关联的。我们的结果揭示了一种细胞如何防止其膜成分发生宏观相分离，同时又能调节局部膜组成的机制。DOI: http://dx.doi.org/10.7554/eLife.01671.001
