Area difference between monolayers facilitates budding of lipid droplets from vesicles

Area of Science:

• Cell biology
• Biophysics
• Membrane dynamics

Background:

• Lipid droplets (LDs) are crucial for cellular lipid and energy balance.
• Little is known about mechanical interactions between LDs and vesicles, especially leaflet area differences.
• Theoretical models for LD-membrane interactions are lacking.

Purpose of the Study:

• To theoretically investigate how monolayer area difference influences LD budding and morphological evolution within a vesicle membrane.
• To rationalize the effects of area difference between vesicle leaflets on LD evolution.
• To establish phase diagrams for LD budding based on interfacial energy and area ratios.

Main Methods:

• Theoretical modeling of lipid droplet-vesicle membrane interactions.
• Analysis of how monolayer area difference affects LD morphology.
• Development of phase diagrams for outward and inward budding.

Main Results:

• Monolayer area difference and interfacial energy strength promote LD budding, transforming confined LDs from bulges to spherical protrusions.
• Budding direction favors the monolayer with a higher phospholipid concentration.
• Vesicle osmotic pressure promotes budding at small area differences but inhibits it at large differences.

Conclusions:

• The study provides a theoretical framework for understanding LD budding driven by leaflet asymmetry.
• Findings highlight the importance of mechanical forces and lipid composition in LD-membrane dynamics.
• The established phase diagrams offer insights into LD morphological transitions.