Dynein arms are strain-dependent direction-switching force generators.

Area of Science:

• Molecular Motor Dynamics
• Cellular Mechanics
• Biophysics

Background:

• Dynein motors are crucial for intracellular transport, typically moving towards the minus end of microtubules.
• Previous studies indicated oscillatory or bidirectional force generation in dyneins under specific conditions.
• The response of axonemal dynein to mechanical forces and its capacity for directional switching remained largely unexplored.

Purpose of the Study:

• To investigate whether axonemal dynein can switch its force generation direction.
• To characterize the force-generating capabilities of axonemal dynein under varying mechanical conditions.
• To understand the role of external forces in modulating dynein's directional movement.

Main Methods:

• Utilized optical trap techniques to measure force generation by dynein.
• Employed UV-photolysis of caged ATP to control motor activity.
• Studied both isolated dynein and dynein arms attached to doublet microtubules.

Main Results:

• Observed that axonemal dynein can repeatedly generate force in both forward (5-6 pN) and backward (∼4 pN) directions along microtubules.
• Demonstrated bidirectional force generation in both isolated dynein and dynein arms attached to native structures.
• Showed that applying a plus-end directed external force before ATP application can stimulate backward force generation.

Conclusions:

• Axonemal dynein exhibits unique, multi-modal force generation, including bidirectional and oscillatory capabilities.
• Mechanical strain plays a significant role in switching the directionality of force generation in axonemal dyneins.
• These findings expand our understanding of motor protein mechanics and regulation.