Effects of crowding on the diffusivity of membrane adhered particles
Effects of crowding on the diffusivity of membrane adhered particles
复制标题
拥挤对膜粘附颗粒扩散率的影响
DOI：
10.1039/d3sm01269g
复制
发表时间：
2023
期刊：
影响因子：
3.4
通讯作者：
Beltramo, Peter J.
中科院分区：
文献类型：
--
作者：
Liu, Paige;Beltramo, Peter J.
细胞膜内含物（例如整合膜蛋白和结合受体）的横向扩散驱动关键的生物过程，包括复合物的形成、细胞间信号传导和膜运输。这些扩散过程因夹杂物的集中或“拥挤”程度而变得复杂，夹杂物可占据膜面积的 30-50%。在这项工作中，我们阐明了独立式人造细胞膜中模型膜内含物浓度的增加对内含物扩散率和膜表观粘度的影响。通过对共价束缚在双层上的荧光微粒进行多粒子追踪，我们展示了从预期的布朗动力学（精确测量膜粘度）到随着粒子面积分数从 1% 增加到 30% 左右（接近拥挤的生理水平）而扩散系数降低的亚扩散行为的转变。在高度拥挤时，观察到非高斯行为的出现。使用将二维扩散系数与膜粘度相关的流体动力学模型，我们从颗粒扩散率确定双层的表观粘度，并显示表观膜粘度随着颗粒面积分数的增加而增加。然而，这种增加的规模与单层夹杂物扩散和本体悬浮液流变学的行为相反。这些结果表明，模型膜拥挤的生理水平会显着改变系统的动力学和表观粘度，这对于理解膜蛋白相互作用和颗粒膜传输过程具有重要意义。
The lateral diffusion of cell membrane inclusions, such as integral membrane proteins and bound receptors, drives critical biological processes, including the formation of complexes, cell–cell signaling, and membrane trafficking. These diffusive processes are complicated by how concentrated, or “crowded”, the inclusions are, which can occupy between 30–50% of the area fraction of the membrane. In this work, we elucidate the effects of increasing concentration of model membrane inclusions in a free-standing artificial cell membrane on inclusion diffusivity and the apparent viscosity of the membrane. By multiple particle tracking of fluorescent microparticles covalently tethered to the bilayer, we show the transition from expected Brownian dynamics, which accurately measure the membrane viscosity, to subdiffusive behavior with decreased diffusion coefficient as the particle area fraction increases from 1% to around 30%, approaching physiological levels of crowding. At high crowding, the onset of non-Gaussian behavior is observed. Using hydrodynamic models relating the 2D diffusion coefficient to the viscosity of a membrane, we determine the apparent viscosity of the bilayer from the particle diffusivity and show an increase in the apparent membrane viscosity with increasing particle area fraction. However, the scaling of this increase is in contrast with the behavior of monolayer inclusion diffusion and bulk suspension rheology. These results demonstrate that physiological levels of model membrane crowding nontrivially alter the dynamics and apparent viscosity of the system, which has implications for understanding membrane protein interactions and particle-membrane transport processes.