Mechanisms for Size-Dependent Protein Segregation at Immune Synapses Assessed with Molecular Rulers
Mechanisms for Size-Dependent Protein Segregation at Immune Synapses Assessed with Molecular Rulers
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DOI：
10.1016/j.bpj.2011.05.013
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发表时间：
2011-06-22
影响因子：
3.4
通讯作者：
Davis, Daniel M.
中科院分区：
文献类型：
--
作者：
Alakoskela, Juha-Matti;Koner, Apurba L.;Davis, Daniel M.
免疫突触是由几种类型的免疫细胞与靶细胞或抗原呈递细胞接触形成的专门的细胞间接触。晚期免疫突触通常是被整联蛋白复合物包围的免疫细胞受体-配体对的靶心模式。根据晶体结构，许多免疫细胞受体-配体对的膜间距离类似于 15 nm，但整联蛋白-配体对的膜间距离类似于 40 nm。这两类膜间键的紧密接近需要显着的膜弯曲，并且此类蛋白质可以根据其大小进行分离，这可能是受体触发的关键。然而，可用于评估突触膜间组织的工具是有限的。在这里，我们提出了一种新方法来测试尺寸在蛋白质细胞间组织中的重要性，使用活细胞显微镜观察一系列尺寸的荧光标记分子和量子点作为分子标尺。小颗粒很容易与与其同源自然杀伤细胞受体结合的 MHC I 类突触共定位，而大于 15 nm 的颗粒则越来越多地从这种相互作用中分离出来。结合按比例粒子吸附理论对粒子划分进行的建模，这些分子标尺展示了膜弯曲弹性如何驱动免疫突触内蛋白质的尺寸依赖性排除。
Immunological synapses are specialized intercellular contacts formed by several types of immune cells in contact with target cells or antigen-presenting cells. A late-stage immune synapse is commonly a bulls-eye pattern of immune cell receptor-ligand pairs surrounded by integrin complexes. Based on crystal structures, the intermembrane distance would be similar to 15 nm for many immune cell receptor-ligand pairs, but similar to 40 nm for integrin-ligand pairs. Close proximity of these two classes of intermembrane bonds would require significant membrane bending and such proteins can segregate according to their size, which may be key for receptor triggering. However, tools available to evaluate the intermembrane organization of the synapse are limited. Here, we present what we believe to be a novel approach to test the importance of size in the intercellular organization of proteins, using live-cell microscopy of a size-series of fluorescently-labeled molecules and quantum dots to act as molecular rulers. Small particles readily colocalized at the synapse with MHC class I bound to its cognate natural killer cell receptor, whereas particles larger than 15 nm were increasingly segregated from this interaction. Combined with modeling of the partitioning of the particles by scaled-particle adsorption theory, these molecular rulers show how membrane-bending elasticity can drive size-dependent exclusion of proteins within immune synapses.