Dynactin functions as both a dynamic tether and brake during dynein-driven motility

Area of Science:

• Cell Biology
• Molecular Motors
• Neuroscience

Background:

• Dynactin is a crucial cofactor for cytoplasmic dynein, a microtubule-based motor protein.
• The precise mechanism by which dynactin regulates dynein activity remains incompletely understood.
• Dynactin's role in cellular functions is vital, but its activation mechanism for dynein is unclear.

Purpose of the Study:

• To investigate the regulatory role of the dynactin subunit p150(Glued) on cytoplasmic dynein.
• To elucidate the mechanism of dynactin-mediated dynein activation using single-molecule approaches.
• To examine the impact of disease-associated mutations on dynactin's regulatory functions.

Main Methods:

• Utilized dual-color total internal reflection fluorescence microscopy for single-molecule analysis.
• Investigated the formation and motility of dynein-p150(Glued) co-complexes.
• Analyzed motility in cell extracts to assess the function of the p150(Glued) CAP-Gly domain.

Main Results:

• p150(Glued) concentration-dependently recruits and tethers dynein to microtubules.
• The CAP-Gly domain of p150(Glued) reduces dynein-dynactin complex detachment rates from microtubules.
• The CAP-Gly domain acts as a brake, slowing dynein motor velocity, and disease mutations abolish these effects.

Conclusions:

• Dynactin enhances dynein's initial recruitment to microtubules.
• Dynactin promotes sustained engagement of dynein with its microtubule track.
• Dysfunction of the dynactin CAP-Gly domain due to mutations contributes to neurodegenerative processes.