Physico-Chimie Curie

Internships Opportunities

Exploring Membrane Phase Separation Dynamics Modulated by Active Actin Networks

Animal cells continually reshape and reorganize their surfaces to facilitate growth and development. The cell surface is a thin (~ 10 nm), essentially two-dimensional complex fluid. Its basic structure is provided by a lipid membrane. Notably, this membrane can undergo phase transition, giving rise to nano-scaled lipid domains1 [1]. These lipid domains play a crucial role in cell functions, such as clustering membrane receptors to enhance chemical signaling for immune response.

Inside the cell, a network of polymers known as the actin cortex is physically linked to the membrane, providing structural support. Additionally, myosin molecular motors supply energy and exert mechanical forces on both the cortex and the membrane. The actin cortex, along with various protein molecules, plays a pivotal role in altering membrane shape and reorganizing membrane proteins. While much is known about how the cell cortex can change the shape of the membrane, we know little about how the active actin network influences the process of membrane phase transition2 [2]. The objective of this project is to address this question.

In this project, we will construct a reconstituted system comprising a flat solid-supported membrane capable of undergoing phase transitions, molecular motors, and the actin cytoskeleton. We have already obtained preliminary results demonstrating how molecular motors can transform nematic actin structure into a astar-like pattern (Figure). Our project will involve examining the dynamics of actin filaments and the phase-separated membrane using super-resolution imaging and single molecule tracking. Simultaneously, we will collaborate closely with theoreticians to develop a mechanical model that can assist in interpreting our experimental findings.

  1. Levental, I.; Levental, K. R.; Heberle, F. A. Lipid Rafts: Controversies Resolved, Mysteries Remain. Trends Cell Biol. 2020. ↩︎
  2. Köster, D. V.; Mayor, S. Cortical Actin and the Plasma Membrane: Inextricably Intertwined. Curr. Opin. Cell Biol. 2016, 38, 81–89. ↩︎

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