Catch-bond behaviour facilitates membrane tubulation by non-processive myosin 1b

Area of Science:

• Cell biology
• Biophysics
• Molecular motors

Background:

• Myosin 1b is a single-headed motor protein crucial for membrane tubule formation in vivo.
• It associates with membranes and actin filaments, exhibiting load-dependent catch-bond behavior.

Purpose of the Study:

• To investigate how myosin 1b's catch-bond properties contribute to membrane tube extraction.
• To link myosin 1b's motor function to its role in forming membrane tubules at endosomes and the trans-Golgi network.

Main Methods:

• Utilized a minimal reconstituted system with bundled actin filaments and membrane tubes.
• Observed myosin 1b's capacity to extract membrane tubes under varying conditions.
• Developed a theoretical model to analyze the role of catch-bond properties.

Main Results:

• Single-headed, non-processive myosin 1b efficiently extracts membrane tubes at low, biologically relevant densities.
• Unlike kinesins, myosin 1b does not accumulate at the tube tip, indicating a distinct mechanism.
• Theoretical modeling shows catch-bond properties enhance tube extraction under increasing membrane tension by lowering motor density requirements.

Conclusions:

• Myosin 1b's catch-bond behavior is key to its function in membrane tube formation.
• The motor's ability to extract tubes at low densities and without tip accumulation reveals a unique mechanism for membrane remodeling.