Brandt R, Lee G
Center for Neurologic Diseases, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115.
J Neurochem. 1993 Sep;61(3):997-1005. doi: 10.1111/j.1471-4159.1993.tb03613.x.
The microtubule-associated protein tau is found primarily in neuronal tissues and is highly enriched in the axon. It promotes microtubule assembly in vitro and stabilizes microtubules in cells. To study how tau protein might be involved in the unique features of axonal microtubules, we have analyzed the effect of E. coli-synthesized tau protein using an in vitro centrosome-mediated microtubule regrowth assay over a wide range of tau/tubulin ratios. We report that microtubule assembly promoted by tau protein exhibits characteristic changes dependent on the tau/tubulin ratio. Above a threshold level, nucleation of new microtubules is favored over growth of existing ones. tau isoform variation does not change this phase transition in microtubule assembly. We discuss how tau might participate in the elaboration of axonal morphology based on our results and present evidence that the phase transition from microtubule growth to nucleation is critical for axonal development.
微管相关蛋白tau主要存在于神经组织中，且在轴突中高度富集。它在体外促进微管组装，并在细胞中稳定微管。为了研究tau蛋白如何参与轴突微管的独特特性，我们使用体外中心体介导的微管再生试验，在广泛的tau/微管蛋白比例范围内分析了大肠杆菌合成的tau蛋白的作用。我们报告说，tau蛋白促进的微管组装表现出依赖于tau/微管蛋白比例的特征性变化。高于阈值水平时，新微管的成核比现有微管的生长更受青睐。tau异构体的变化不会改变微管组装中的这种相变。我们根据研究结果讨论了tau如何参与轴突形态的形成，并提供证据表明从微管生长到成核的相变对轴突发育至关重要。
