Actin-microtubule interactions in the algaNitella: analysis of the mechanism by which microtubule depolymerization potentiates cytochalasin's effects on streaming
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- Collings, D.A., Wasteneys, G.O. & Williamson, R.E. Protoplasma (1996) 191: 178. doi:10.1007/BF01281816
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In the characean algaNitella, depolymerization of microtubules potentiates the inhibitory effects of cytochalasins on cytoplasmic streaming. Microtubule depolymerization lowers the cytochalasin B and D concentrations required to inhibit streaming, accelerates inhibition and delays streaming recovery. Because microtubule depolymerization does not significantly alter3H-cytochalasin B uptake and release, elevated intracellular cytochalasin concentrations are not the basis for potentiation. Instead, microtubule depolymerization causes actin to become more sensitive to cytochalasin. This increased sensitivity of actin is unlikely to be due to direct stabilization of actin by microtubules, however, because very few microtubules colocalize with the subcortical actin bundles that generate streaming. Furthermore, microtubule reassembly, but not recovery of former transverse alignment, is sufficient for restoring the normal cellular responses to cytochalasin D. We hypothesize that either tubulin or microtubule-associated proteins, released when microtubules depolymerize, interact with the actin cytoskeleton and sensitize it to cytochalasin.
KeywordsActin Cytoplasmic streaming Cytochalasin Microtubule depolymerization Nitella Oryzalin
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