# The Plasma Membrane is Compartmentalized by a Self-Similar Cortical Actin Meshwork

## TL;DR

This study visualizes the cortical actin meshwork in live cells, revealing its self-similar, fractal organization that compartmentalizes the plasma membrane and influences membrane protein diffusion.

## Contribution

It provides direct high-resolution imaging evidence of the actin meshwork's fractal structure and its role in membrane compartmentalization, addressing previous visualization challenges.

## Key findings

- Actin forms a self-similar, fractal meshwork.
- Membrane proteins are transiently confined by actin fences.
- The actin meshwork creates hierarchical membrane compartments.

## Abstract

A broad range of membrane proteins display anomalous diffusion on the cell surface. Different methods provide evidence for obstructed subdiffusion and diffusion on a fractal space, but the underlying structure inducing anomalous diffusion has never been visualized due to experimental challenges. We addressed this problem by imaging the cortical actin at high resolution while simultaneously tracking individual membrane proteins in live mammalian cells. Our data confirm that actin introduces barriers leading to compartmentalization of the plasma membrane and that membrane proteins are transiently confined within actin fences. Furthermore, superresolution imaging shows that the cortical actin is organized into a self-similar meshwork. These results present a hierarchical nanoscale picture of the plasma membrane.