3D pattern formation of a protein-membrane suspension

TL;DR

This study demonstrates that membrane fragmentation into liposomes enables 3D pattern formation by Min proteins, revealing new dynamical behaviors and scaling effects that differ from continuous membranes, advancing understanding of cellular patterning mechanisms.

Contribution

It shows that protein-membrane suspensions can produce large-scale 3D patterns, expanding the understanding of pattern formation beyond traditional 2D membrane systems.

Findings

3D patterns emerge on fragmented membranes despite loss of continuity

A variety of dynamical patterns including traveling waves and spirals are observed

Physical properties of liposomes rescale key parameters like binding rates and diffusion

Abstract

Many essential cellular processes, including cell division and the establishment of cell polarity during embryogenesis, are regulated by pattern-forming proteins. These proteins often need to bind to a substrate, such as the cell membrane, onto which they interact and form two-dimensional (2D) patterns. It is unclear how the membrane's continuity and dimensionality impact pattern formation. Here, we address this gap using the MinDE system, a prototypical example of pattern-forming membrane proteins. We show that when the lipid substrate is fragmented into submicrometer-sized diffusive liposomes, ATP-driven protein-protein interactions generate three-dimensional (3D) spatially extended patterns, despite the complete loss of membrane continuity. Remarkably, these 3D patterns emerge at scales four orders of magnitude larger than the individual liposomes. By systematically varying protein concentration, liposome size, and density, we observed and characterized a variety of 3D dynamical patterns not seen on continuous 2D membranes, including traveling waves, dynamical spirals, and a coexistence phase. Simulations and linear stability analysis of a coarse-grained model revealed that the physical properties of the dispersed membrane effectively rescale both the protein-membrane binding rates and diffusion, two key parameters governing pattern formation and wavelength selection. These findings highlight the robustness of Min's pattern-forming ability, suggesting that protein-membrane suspensions could serve as an adaptable template for studying out-of-equilibrium self-organization in 3D, beyond in vivo contexts.