Dynein tethers and stabilizes dynamic microtubule plus ends

Area of Science:

• Cell Biology
• Cytoskeletal Dynamics
• Molecular Motors

Background:

• Microtubules exhibit dynamic instability, alternating growth and shortening, enabling exploration of cellular space.
• The "search and capture" model suggests microtubule end anchoring at the cell cortex is crucial for cell polarization and organelle transport.
• Cortical cytoplasmic dynein is known to capture and tether microtubules at the cell periphery.

Purpose of the Study:

• To investigate the mechanism by which cortical dynein influences microtubule dynamics.
• To determine if dynein motor activity is required for microtubule capture and stabilization.
• To elucidate the role of dynein in regulating microtubule plus-end stability at the cell cortex.

Main Methods:

• Development of a minimal in vitro system using dynein-bound beads and optical traps to manipulate microtubule plus ends.
• Assays measuring the lateral diffusion of microtubule ends in the presence of dynein.
• Experiments with dynamic microtubules to assess dynein's effect on barrier-induced catastrophe.
• ATP-dependency assays to confirm the role of dynein motor activity.
• Computational modeling to understand the physical mechanism of dynein-mediated stabilization.

Main Results:

• Dynein significantly reduced the lateral diffusion of microtubule plus ends, a distinct effect compared to kinesin-1 and EB1.
• Dynein delayed barrier-induced catastrophe in dynamic microtubules in an ATP-dependent manner.
• Computational modeling indicated that dynein stabilizes microtubules by exerting tension on protofilaments.

Conclusions:

• Cortical dynein captures and tethers microtubule plus ends, reducing their lateral mobility.
• Dynein motor activity stabilizes dynamic microtubule plus ends by delaying catastrophe, likely through protofilament tension.
• This mechanism contributes to the regulation of microtubule dynamics at the cell cortex.