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A protein complex better known for its role in microtubule nucleation at the centrosome is also a stabilizing factor that controls cytoskeletal dynamics, say Bouissou et al.
γ-Tubulin and its partners in the γ-tubulin ring complex (γ-TuRC) initiate the growth of new microtubules. This is particularly important during mitosis—cells missing γ-TuRC subunits either fail to divide or go through the process slowly. Little is known about the complex's function in interphase, however.
Bouissou et al. depleted several γ-TuRC components (including γ-tubulin itself) in Drosophila cells and found that microtubule organization was unaffected. But live microscopy revealed that the microtubules in these cells were more dynamic and more likely to switch from growing to shrinking, whereas microtubules from control cells often remained paused. The researchers saw γ-TuRC dotting the length of microtubules, and determined that these spots corresponded to sites where dynamic microtubules would either pause or begin to regrow. Microtubules tended not to depolymerize past the points of γ-TuRC, suggesting that the complex acts as a stabilizing factor, perhaps by counteracting the binding of other microtubule-associated proteins that promote disassembly.
Because Drosophila cell microtubules are arranged somewhat differently to those in most animal cells, the group now wants to see whether γ-TuRC has a similar function in other cell types. Senior author Brigitte Raynaud-Messina also plans to investigate whether the complex regulates specialized subsets of microtubules that particularly need stabilizing.