Visualization of dynamic reorganization in freestanding planar lipid membranes by membrane-based reactions

Abstract

therefore, the systematic assessment of dynamic membrane behaviors has always been challenging. This thesis aims to figure out physicochemical factors contributing to the fine-controlled dynamic reorganization of cell membranes at a fundamental level. To begin with, we developed a powerful artificial membrane system capable of visualizing the spatiotemporal dynamics of membrane remodeling in real time. By simply using a TEM mesh grid and well-defined air/oil/water interfaces on its grid holes, we realized tens of uniform planar lipid bilayer membranes. The freestanding membranes are large but also highly stable, facilitating direct long-term monitoring of membrane reconstitution caused by external stimuli. Secondly, in order to demonstrate the superiority of our model membrane system, as an example, we investigated the effect of cholesterol trafficking, which is known to significantly affect biophysical properties of the cell membrane at different membrane compositions. Cholesterol transport into and out of the membranes at different rates enabled us to observe interesting phenomena, including cholesterol-mediated phase transition and decomposition, which have never been witnessed before. Lastly, we found the asymmetric membrane remodeling under enzymatic reactions, employing sphingomyelinases that regulate sphingolipid metabolism in cell membranes. We strongly believe that our technique can be broadly applied for exploring the dynamic membrane heterogeneity under various membrane-based reactions, providing valuable insight into the membrane dynamics.

Cell membranes have laterally segregated domains that actively change their size, shape, and compositions, which play an integral role in various biological functions. Although membrane dynamics is a vital part of cellular processes, the complexity of cell membranes has made its fundamental understanding difficult. Even available model membranes cannot be easily prepared and controlled