Propagating cell-membrane waves driven by curved activators of actin polymerization

Area of Science:

• Cell Biology
• Biophysics
• Cytoskeleton Dynamics

Background:

• Cells generate membrane waves involving the actin cytoskeleton, including Circular Dorsal Ruffles (CDRs).
• CDRs are linked to endocytosis and receptor internalization.
• Previously, CDRs were associated with concave membrane-bound activators of actin polymerization.

Purpose of the Study:

• To investigate the role of convex membrane proteins in CDR formation.
• To develop a theoretical model explaining CDRs based on membrane curvature and actin polymerization.
• To understand the interplay between membrane protein shape and actin cytoskeleton organization.

Main Methods:

• Experimental observation of protein localization in CDRs using immortalized mouse embryo fibroblasts.
• Inhibition of myosin II contractility to assess its effect on CDRs.
• Development and analysis of a theoretical model for wave formation.

Main Results:

• Experimental evidence shows convex membrane proteins localize to CDRs.
• CDRs are insensitive to myosin II contractility inhibition.
• The theoretical model demonstrates that both concave and convex activators are essential for wave propagation.
• Model predicts wave initiation depends on a threshold of actin polymerization.

Conclusions:

• Curved membrane proteins (both concave and convex) are crucial for organizing the actin cytoskeleton and cell shape.
• The interplay between membrane curvature activators and actin polymerization drives CDR formation.
• The findings provide a new framework for understanding cell shape dynamics and membrane-protein interactions.