Critical Phenomena in Plasma Membrane Organization and Function

TL;DR

This review discusses how plasma membrane heterogeneity is influenced by critical phenomena near a phase transition point, highlighting the role of liquid-liquid phase separation in membrane organization and function.

Contribution

It synthesizes recent experimental evidence supporting the criticality hypothesis in plasma membranes and explores its implications for membrane heterogeneity and cellular responses.

Findings

Membrane heterogeneity can be explained by proximity to a critical point.

Critical phenomena predict membrane responses to composition changes.

Liquid-liquid phase separation underpins membrane organization.

Abstract

Lateral organization in the plane of the plasma membrane is an important driver of biological processes. The past dozen years have seen increasing experimental support for the notion that lipid organization plays an important role in modulating this heterogeneity. Various biophysical mechanisms rooted in the concept of liquid-liquid phase separation have been proposed to explain diverse experimental observations of heterogeneity in model and cell membranes, with distinct but overlapping applicability. In this review, we focus on evidence for and consequences of the hypothesis that the plasma membrane is poised near an equilibrium miscibility critical point. Critical phenomena explain certain features of the heterogeneity observed in cells and model systems, but also go beyond heterogeneity to predict other interesting phenomena, including responses to composition perturbations.