Collaborative Research: Mechanics of Tension-Induced Adaptation in Clathrin-Mediated Endocytosis

大分子进入细胞的运输通过一系列途径发生，通常被称为内吞作用。这些途径的特征是一连串的重塑事件，在此过程中，几乎平坦的质膜斑块转变为携带货物的闭合小泡。最常用的途径是网状蛋白介导的内吞作用(CME)，它在细胞膜和细胞器之间的脂类和蛋白质交换中起重要作用。因此，CME对于维持质膜的组织和调节各种细胞过程至关重要。最近对CME的研究表明，细胞通过适应蛋白质机制来感知机械环境，以确保CME的成功。细胞如何感知和适应机械环境以维持细胞运输还不是很清楚。这个项目的目标是通过理论和实验相结合的方法，获得对细胞中这种动态适应的机械性见解。由于细胞在不同的疾病状态下经历不同的机械环境，这项工作可以为疾病细胞中的细胞运输提供基本的见解，有助于改进的纳米颗粒药物的设计。这项工作将为观察到的网状蛋白介导的内吞作用中的机械敏感性和基于张力的适应提供物理解释。为了实现这一目标，膜-蛋白质相互作用的连续介质力学和蒙特卡罗模拟将与高分辨率活细胞和超分辨率荧光显微镜相辅相成，以检验在CME中膜相关蛋白组装和张力诱导适应的相互竞争的解释。这项研究将解决内吞作用文献中的两个主要争论。首先，它将确定笼状蛋白驱动膜曲率的能量最优机制。其次，它将确定膜感受张力并招募肌动蛋白细丝驱动囊泡生长的机制。数值和实验结果将量化关键的膜重塑蛋白在多大程度上能够对抗张力和驱动囊泡生长。总体而言，这些发现将揭示张力调节膜重塑蛋白组装的一般原理。

Transport of macromolecules into cells occurs via a collection of pathways, commonly referred to as endocytosis. These pathways are characterized by a chain of remodeling events during which an almost flat patch of plasma membrane is transformed into a cargo-carrying closed vesicle. The most commonly used pathway is called clathrin-mediated endocytosis (CME) which is important for the exchange of lipids and proteins between the plasma membrane and organelles. As such, CME is critical for maintaining the organization of the plasma membrane and regulating various cellular processes. Recent research on CME suggests that cells sense the mechanical environment by adapting the protein machinery to ensure successful CME. How cells sense and adapt to the mechanical environment to maintain cellular transport is not well understood. The goal of this project is to gain mechanistic insights into this dynamic adaptation in cells via combined theoretical and experimental approaches. Since cells experience varied mechanical environments in different diseased states, this work can provide fundamental insights into cellular transport in diseased cells that can help facilitate the design of improved nanoparticle-based drugs.This work will offer a physical explanation for the observed "mechanosensitivity" and tension-based adaptation in clathrin-mediated endocytosis. To achieve this objective, continuum mechanics and Monte Carlo simulations of membrane-protein interactions will be complimented with high-resolution live cell and super-resolution fluorescence microscopy to test the competing explanations for assembly of membrane-associated proteins and tension-induced adaptation in CME. This study will address two major debates in the endocytosis literature. First, it will identify the energetically optimal mechanism by which clathrin drives membrane curvature. Second, it will identify the mechanism by which membrane senses tension and recruits actin filaments for driving vesicle growth. The numerical and experimental findings will quantify the extent to which the key membrane-remodeling proteins can counter tension and drive vesicle growth. Overall, these findings would reveal the general principles by which tension regulates the assembly of membrane-remodeling proteins.