EAGER: Topographically Induced Lateral Organization in Biomimetic Lipid Membranes

Living cells constantly undergo shape changes to facilitate biological functions that are essential to the cell survival. These shape changes are primarily driven by an intracellular network of filaments and tubules, known as the cytoskeleton. During cell reshaping, forces applied by the cytoskeleton cause deformations in the cell membrane, a thin layer of lipids and proteins defining the cell boundary.

Importantly, such deformations have been linked to changes in molecular arrangements, and emergent functions, within cell membranes. However, it is unclear to what extent variations in membrane shapes can induce and regulate molecular rearrangements, particularly clusters (or domains) of lipid molecules implied in various cell functions. This EArly-concept Grant for Exploratory Research (EAGER) project aims to explore this important phenomenon through systematic experimental studies of membrane curvature and emergent lipid domains.

This will be accomplished through a novel design of nanofabricated substrates, coated with a soft hydrogel film, that mimic the cell cytoskeleton. Model lipid membranes, deposited on the fabricated substrates, will illustrate how membrane curvature and cytoskeletal interactions influence the formation, growth, and stability of lipid domains. The experiments will be synergistically integrated with computer simulations to uncover the molecular mechanisms underlying the observed lipid domain behavior.

Throughout the course of the project, the principal investigator will train graduate and undergraduate students in experimental and computational methods which will prepare them for careers in STEM. Findings from this project will be communicated to the scientific community and the general public through conference presentations, peer-reviewed publications, open-source data analysis software, and video-recorded instructional tutorials.

Cell membranes adopt various shapes and curvatures, much of which are driven by dynamic cytoskeletal deformations and are critical to the cell function. Cells are thought to use membrane reshaping as a mechanism to translate mechanical signals into compositional rearrangements and subsequent biochemical processes. Such rearrangements include the formation and stabilization of functional lipid domains that act as platforms for localizing signaling proteins and maintaining the cell viability.

However, a clear understanding of how membrane topography drives the structuring and localization of lipid domains is still lacking. The main goal of this project is to elucidate the key factors underlying curvature-induced domain patterning in lipid membranes, including local curvature and energetic penalties. This will be achieved using a suite of complementary experimental, theoretical, and computational methods along with a novel design of topographically structured hydrogel scaffolds as a proxy to the cell cytoskeleton.

A primary objective of the project is to optimize membrane topography and membrane-scaffold interactions to allow systematic studies of emergent lipid domains. The aim is to identify the role of topography and interactions in controlling the size, localization, and diffusion of the lipid domains. A distinctive feature of this project is the use of off-specular neutron scattering, aided with theoretical developments and computer simulations, to determine domain organization on the nanoscale, i.e. beyond the resolution of optical microscopy methods.

Developments in this area will open new avenues for investigations of nanoscale membrane structures that are seldom explored but are critical to biological applications, including artificial cells and membrane-based biosensors.

This project is jointly funded by Molecular and Cellular Biosciences (MCB) Division (Molecular Biophysics and Cellular Dynamics and Function clusters) and the Biomechanics and Mechanobiology Program at Civil, Mechanical, and Manufacturing Innovation Division.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.