Phase transitions of the coupled membrane-cytoskeleton modify cellular shape

Area of Science:

• Cell Biology
• Biophysics
• Soft Matter Physics

Background:

• Cell membrane protrusions and protein segregation are vital for cellular functions.
• Mechanical properties of the substrate significantly impact cell morphology and behavior.
• Existing models do not fully explain the interplay between membrane mechanics and protein organization.

Purpose of the Study:

• To propose a theoretical mechanism for membrane protrusion formation and protein phase separation.
• To investigate the role of membrane protein spontaneous curvature, cell-substrate adhesion, and actin polymerization forces.
• To link theoretical predictions to experimental observations in living cells and model systems.

Main Methods:

• Development of a continuum model coupling membrane and protein dynamics.
• Inclusion of cell-substrate adhesion and protrusive actin force.
• Application of linear stability analysis to identify phase separation regimes.

Main Results:

• Strong adhesion energy and actin polymerization force can induce membrane protein phase separation and protrusion formation.
• Phase separation occurs even when spontaneous curvature and aggregation potential alone are insufficient.
• Finite-size patterns emerge when spontaneous curvature energy is a dominant factor.

Conclusions:

• The proposed model provides a mechanistic explanation for substrate-induced cell morphology changes.
• The model successfully predicts different instability characteristics relevant to observed cellular phenomena.
• Testable predictions are offered for future experimental validation.