Membrane transformations of fusion and budding.

Area of Science:

• Cell Biology
• Biophysics

Background:

• Membrane fusion and budding are essential for cellular processes like trafficking and exocytosis.
• Classical models describe fusion as pore opening and budding as vesicle formation from flat membranes.

Purpose of the Study:

• To synthesize a new model of membrane fusion and budding based on recent visualization breakthroughs.
• To describe the mechanistic principles and functions underlying these dynamic membrane transformations.

Main Methods:

• Review of recent breakthroughs in real-time visualization of membrane transformations.
• Synthesis of a new model integrating diverse mechanistic principles.

Main Results:

• Fusion involves hemi-to-full fusion, pore expansion, constriction, and closure; vesicles can shrink, enlarge, or fuse with others.
• Endocytosis follows exocytosis via Ω-shaped profile closure, formed through specific shape transitions or fusion.
• Multiple molecular machineries (e.g., Calcium/SNARE, cytoskeleton, dynamin) coordinate diverse fusion and budding modes.

Conclusions:

• The new model offers a more comprehensive view of membrane fusion and budding dynamics.
• These coordinated processes are crucial for regulating vesicle trafficking, content release, and maintaining membrane homeostasis.
• The described mechanisms and functions may be conserved across various fusion and budding events.