Impact of Nanoscale Hindrances on the Relationship between Lipid Packing and Diffusion in Model Membranes.

Daniel Beckers,Erdinc Sezgin,Dunja Urbancic

doi:10.1021/acs.jpcb.0c00445

Abstract

Membrane models have allowed for precise study of the plasma membrane’s biophysical properties, helping to unravel both structural and dynamic motifs within cell biology. Freestanding and supported bilayer systems are popular models to reconstitute membrane-related processes. Although it is well-known that each have their advantages and limitations, comprehensive comparison of their biophysical properties is still lacking. Here, we compare the diffusion and lipid packing in giant unilamellar vesicles, planar and spherical supported membranes, and cell-derived giant plasma membrane vesicles. We apply florescence correlation spectroscopy (FCS), spectral imaging, and super-resolution stimulated emission depletion FCS to study the diffusivity, lipid packing, and nanoscale architecture of these membrane systems, respectively. Our data show that lipid packing and diffusivity is tightly correlated in freestanding bilayers. However, nanoscale interactions in the supported bilayers cause deviation from this correlation. These data are essential to develop accurate theoretical models of the plasma membrane and will serve as a guideline for suitable model selection in future studies to reconstitute biological processes.

Highlights

The cascades for signal transduction usually begin at the cell surface, and for this reason the plasma membrane can be considered as the main hub for cellular signaling.[1]
Our chosen models span from freestanding giant unilamellar vesicles (GUVs) to supported planar supported lipid bilayers (SLBs) and spherical bead supported lipid bilayers (BSLBs) constructs and to the more cellular inspired bilayer model of giant plasma membrane vesicles (GPMVs) (Figure 1)
Few studies have ventured a comprehensive comparison of their biophysical properties as a function of the inherent parameters.[18,25,28,40−43] a few studies have highlighted this concern by demonstrating altered protein functionality in different membrane models.[44,45]

Summary

Introduction

The cascades for signal transduction usually begin at the cell surface, and for this reason the plasma membrane can be considered as the main hub for cellular signaling.[1] drawing conclusions about membrane behavior and architecture proves challenging, not least because poorly understood or still unknown processes influence its dynamics.[2,3] Our current knowledge shows that plasma membrane is a vastly complex and intricate system.[4] to truly appreciate and understand the finesse behind membrane dynamics, a “bottomup” approach to discern different processes can prove useful.[5] Several systems address this, employing a basic skeleton of only the essential biological components of the plasma membrane but engineered to allow systematic incorporation of complexity.[6] Such reductionist systems can mimic membranes and allow membrane-associated events to be systematically broken down to reveal their key contributing species owing to their controllable compositional complexity.[7] Popular models include freestanding bilayers of synthetic lipids such as giant unilamellar vesicles (GUVs)[8] or membrane blebs of live cells known as giant plasma membrane vesicles (GPMVs).[9,10] the development of solid substrates to support bilayers has shown promise, with two prominent constructs being the planar substrate/supported lipid bilayers (SLBs)[11,12] and spherical bead supported lipid bilayers (BSLBs)[13,14] ( termed spherical supported lipid bilayers, SSLBs)

Methods

Results

Conclusion