Coupling Anisotropic Curvature and Nematic Order: Mechanisms of Membrane Shape Remodeling

TL;DR

This paper presents a theoretical framework showing how anisotropic membrane components influence vesicle shapes through curvature sensing, nematic interactions, and topological defects, revealing new phases and mechanisms of membrane remodeling.

Contribution

It introduces a unified theoretical model linking anisotropic curvature, nematic order, and membrane shape changes, identifying novel vesicle phases and defect localization mechanisms.

Findings

Arc-shaped CMCs induce pearling-to-cylinder transition.

Saddle-shaped CMCs stabilize membrane necks.

Topological defects localize to high-curvature regions.

Abstract

This study theoretically investigates how anisotropic curved membrane components (CMCs) control vesicle morphology through curvature sensing, nematic alignment, topological defects, and volume constraints. By comparing arc-shaped and saddle-shaped CMCs, we identify a rich spectrum of steady-state phases. For fully CMC-covered vesicles, arc-shaped components drive a pearling-to-cylinder transition as nematic interactions strengthen, while on partially CMC-covered vesicles, the saddle-shaped CMCs stabilize necks between the convex regions of bare membrane. We map the steady-state shapes of vesicles partially covered by arc-like and saddle-shaped CMCs, exposing how different vesicle shapes depend on the interplay between nematic interactions and volume constraints, revealing several novel phases. By investigating the in-plane nematic field, we find that topological defects consistently localize to high-curvature regions, revealing how intrinsic and deviatoric curvature effects cooperate in membrane remodeling. These findings establish a unified framework for understanding how proteins and lipid domains with anisotropic intrinsic curvature shape cellular structures -- from organelle morphogenesis to global cell shape.