Cheney Philip P, Weisgerber Alan W, Feuerbach Alec M, Knowles Michelle K
Department of Pharmaceutical Sciences, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA.
Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80208, USA.
Membranes (Basel). 2017 Mar 15;7(1):15. doi: 10.3390/membranes7010015.
The plasma membrane is a highly compartmentalized, dynamic material and this organization is essential for a wide variety of cellular processes. Nanoscale domains allow proteins to organize for cell signaling, endo- and exocytosis, and other essential processes. Even in the absence of proteins, lipids have the ability to organize into domains as a result of a variety of chemical and physical interactions. One feature of membranes that affects lipid domain formation is membrane curvature. To directly test the role of curvature in lipid sorting, we measured the accumulation of two similar lipids, 1,2-Dihexadecanoyl--glycero-3-phosphoethanolamine (DHPE) and hexadecanoic acid (HDA), using a supported lipid bilayer that was assembled over a nanopatterned surface to obtain regions of membrane curvature. Both lipids studied contain 16 carbon, saturated tails and a head group tag for fluorescence microscopy measurements. The accumulation of lipids at curvatures ranging from 28 nm to 55 nm radii was measured and fluorescein labeled DHPE accumulated more than fluorescein labeled HDA at regions of membrane curvature. We then tested whether single biotinylated DHPE molecules sense curvature using single particle tracking methods. Similar to groups of fluorescein labeled DHPE accumulating at curvature, the dynamics of single molecules of biotinylated DHPE was also affected by membrane curvature and highly confined motion was observed.
质膜是一种高度分隔的动态物质，这种组织形式对于多种细胞过程至关重要。纳米级结构域使蛋白质能够组织起来参与细胞信号传导、胞吞和胞吐作用以及其他重要过程。即使在没有蛋白质的情况下，由于各种化学和物理相互作用，脂质也有能力组织成结构域。影响脂质结构域形成的膜的一个特征是膜曲率。为了直接测试曲率在脂质分选中的作用，我们使用在纳米图案化表面上组装的支持脂质双层来获得膜曲率区域，测量了两种相似脂质，1,2 - 二己酰 - sn - 甘油 - 3 - 磷酸乙醇胺（DHPE）和十六烷酸（HDA）的积累情况。所研究的两种脂质都含有16个碳的饱和尾部以及用于荧光显微镜测量的头部基团标签。测量了脂质在半径为28纳米至55纳米的曲率处的积累情况，并且在膜曲率区域，荧光素标记的DHPE比荧光素标记的HDA积累得更多。然后，我们使用单粒子追踪方法测试了单个生物素化的DHPE分子是否能感知曲率。与荧光素标记的DHPE在曲率处积累的情况类似，生物素化的DHPE单分子的动力学也受到膜曲率的影响，并且观察到了高度受限的运动。
