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Published on: March 15, 2014
Divergent microtubule assembly rates after short- versus long-term loss of end-modulating kinesins
Linda Wordeman1, Justin Decarreau2, Juan Jesus Vicente2
1Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, WA 98195 worde@uw.edu.
Abstract:
Depletion of microtubule (MT) regulators can initiate stable alterations in MT assembly rates that affect chromosome instability and mitotic spindle function, but the manner by which cellular MT assembly rates can stably increase or decrease is not understood. To investigate this phenomenon, we measured the response of microtubule assembly to both rapid and long-term loss of MT regulators MCAK/Kif2C and Kif18A. Depletion of MCAK/Kif2C by siRNA stably decreases MT assembly rates in mitotic spindles, whereas depletion of Kif18A stably increases rates of assembly. Surprisingly, this is not phenocopied by rapid rapamycin-dependent relocalization of MCAK/Kif2C and Kif18A to the plasma membrane. Instead, this treatment yields opposite affects on MT assembly. Rapidly increased MT assembly rates are balanced by a decrease in nucleated microtubules, whereas nucleation appears to be maximal and limiting for decreased MT assembly rates and also for long-term treatments. We measured amplified tubulin synthesis during long-term depletion of MT regulators and hypothesize that this is the basis for different phenotypes arising from long-term versus rapid depletion of MT regulators.
Insights
Microtubule (MT) regulators MCAK/Kif2C and Kif18A influence chromosome stability. Long-term depletion stably alters MT assembly rates, unlike rapid depletion, suggesting amplified tubulin synthesis plays a key role.
Area of Science:
- Cell Biology
- Molecular Biology
- Genetics
Background:
- Microtubule (MT) dynamics are crucial for chromosome segregation and mitotic spindle function.
- Stable alterations in MT assembly rates can arise from depletion of MT regulators, but the mechanisms are unclear.
Purpose of the Study:
- To investigate how cellular MT assembly rates stably increase or decrease.
- To understand the differential effects of rapid versus long-term depletion of MT regulators.
Main Methods:
- Utilized siRNA to deplete MT regulators MCAK/Kif2C and Kif18A.
- Measured MT assembly rates in response to both rapid and long-term depletion.
- Employed rapamycin-dependent relocalization to study rapid MT regulator changes.
Main Results:
- Depletion of MCAK/Kif2C stably decreased MT assembly rates.
- Depletion of Kif18A stably increased MT assembly rates.
- Rapid MT regulator depletion yielded opposite effects compared to long-term depletion, with nucleation being a limiting factor.
Conclusions:
- Long-term depletion of MT regulators leads to stable changes in MT assembly rates.
- Amplified tubulin synthesis during long-term depletion may explain differing phenotypes.
- Nucleation is maximal and limiting for decreased MT assembly rates and long-term treatments.
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