Confined diffusion of transmembrane proteins and lipids induced by the same actin meshwork lining the plasma membrane.
Confined diffusion of transmembrane proteins and lipids induced by the same actin meshwork lining the plasma membrane.
复制标题
DOI：
10.1091/mbc.e15-04-0186
复制
发表时间：
2016-04-01
影响因子：
3.3
通讯作者：
Kusumi A
中科院分区：
文献类型：
--
作者：
Fujiwara TK;Iwasawa K;Kalay Z;Tsunoyama TA;Watanabe Y;Umemura YM;Murakoshi H;Suzuki KG;Nemoto YL;Morone N;Kusumi A
用~lt；25-μS的超高速单分子示踪和电子断层扫描表明，质膜中的跨膜蛋白和磷脂在相同大小的亚微米之间跳跃，可能由排列在肌动蛋白膜骨架围栏上的锚定的跨膜蛋白纠察队划定，每1-58ms一次。质膜中扩散速率的调节机制仍未解决，尽管它们在质膜中的反应速率的空间调节中很重要所提出的模型包括在PtK2细胞中发现的纳米级非连续区域的捕获，由于拥挤而导致的缓慢扩散，以及肌动蛋白诱导的区间化。在这里，通过应用高时间分辨率的单粒子跟踪，主要是PtK2-cell PM，我们发现在这里使用的所有五种细胞系中，即使在肌动蛋白调节药物处理后，非RAFT磷脂和跨膜蛋白、转铁蛋白受体的受限扩散和跳跃运动(称为“HOP扩散”)，以及这两个分子的相同间隔大小(实际大小取决于细胞)。截面大小和胞质结构域大小都影响跳频。电子断层扫描证实位于PtK2细胞质膜表面8.8 nm范围内的肌动蛋白膜骨架(MSK)与PM分子扩散的隔室大小相同。膜蛋白的胞外基质和胞外结构域不参与HOP扩散。这些结果支持以肌动蛋白为基础的MSK内锚定TM蛋白纠察物的模型，作为调节扩散的主要机制。
Ultraspeed single-molecule tracking with <25-μs resolution and electron tomography show that transmembrane proteins and phospholipids in the plasma membrane hop among submicrometer compartments of the same size, probably delimited by the anchored-transmembrane-protein pickets lining the actin-based membrane-skeleton fence, once every 1–58 ms. The mechanisms by which the diffusion rate in the plasma membrane (PM) is regulated remain unresolved, despite their importance in spatially regulating the reaction rates in the PM. Proposed models include entrapment in nanoscale noncontiguous domains found in PtK2 cells, slow diffusion due to crowding, and actin-induced compartmentalization. Here, by applying single-particle tracking at high time resolutions, mainly to the PtK2-cell PM, we found confined diffusion plus hop movements (termed “hop diffusion”) for both a nonraft phospholipid and a transmembrane protein, transferrin receptor, and equal compartment sizes for these two molecules in all five of the cell lines used here (actual sizes were cell dependent), even after treatment with actin-modulating drugs. The cross-section size and the cytoplasmic domain size both affected the hop frequency. Electron tomography identified the actin-based membrane skeleton (MSK) located within 8.8 nm from the PM cytoplasmic surface of PtK2 cells and demonstrated that the MSK mesh size was the same as the compartment size for PM molecular diffusion. The extracellular matrix and extracellular domains of membrane proteins were not involved in hop diffusion. These results support a model of anchored TM-protein pickets lining actin-based MSK as a major mechanism for regulating diffusion.