Drosophila katanin-60 depolymerizes and severs at microtubule defects

Area of Science:

• Cell Biology
• Molecular Motors
• Cytoskeleton Dynamics

Background:

• Microtubule (MT) dynamics are crucial for cellular functions and are regulated by MT-associated proteins.
• MT-severing enzymes, like katanin, are a key family of proteins controlling MT length and organization.
• Katanin (p60) is a well-known MT-severing enzyme whose precise mechanism of action requires further elucidation.

Purpose of the Study:

• To investigate the binding and severing mechanisms of katanin (p60) on microtubules at the single-molecule level.
• To understand the factors influencing katanin's activity, localization, and interaction with tubulin.
• To explore the role of ATP in katanin's function and dynamics.

Main Methods:

• Single-molecule total internal reflection fluorescence microscopy was employed to observe katanin-MT interactions.
• Experiments utilized varying concentrations of katanin and different tubulin states (GMPCPP-tubulin and GDP-tubulin).
• Katanin's binding duration, mobility, and oligomerization were analyzed in an ATP-dependent manner.

Main Results:

• Katanin's severing activity is directly dependent on its concentration.
• Katanin exhibits depolymerization activity by removing tubulin dimers from MT ends.
• Katanin preferentially localizes and severs at the interface of GMPCPP-tubulin and GDP-tubulin, indicating targeting of protofilament-shift defects.
• Katanin's binding duration, mobility, and oligomerization are regulated by ATP.

Conclusions:

• Katanin (p60) functions as an ATP-dependent microtubule-severing enzyme that targets specific structural defects.
• The enzyme's ability to depolymerize microtubules by removing tubulin dimers contributes to its role in MT dynamics.
• Understanding katanin's mechanism provides insights into the regulation of the microtubule cytoskeleton.