Preuss U, Biernat J, Mandelkow E M, Mandelkow E
Max-Planck-Unit for Structural Molecular Biology, Hamburg, Germany.
J Cell Sci. 1997 Mar;110 ( Pt 6):789-800. doi: 10.1242/jcs.110.6.789.
Tau is a neuronal microtubule-associated protein which promotes microtubule assembly. The C-terminal half of the protein contains three or four tandem repeats that are often considered to be the microtubule binding domain. This view is in conflict with in vitro data showing that the repeat domain binds only weakly to microtubules while the domains flanking the repeats bind strongly, even in the absence of the repeats. This has lead us to propose a 'jaws' model of tau whereby the regions flanking the repeats are considered as targetting domains, responsible for positioning tau on the microtubule surface, and the repeats which act as catalytic domains for microtubule assembly. To examine whether this model is appropriate in vivo we generated recombinant tau isoforms and microinjected them into CHO cells. Immunofluorescence microscopy of microtubules and tau shows that binding to microtubules, stabilization of microtubules and formation of bundles is not achieved by tau constructs comprising individual domains, but requires the combination of the flanking regions and the repeat domain. The results show that the jaws model describes the interactions between tau and microtubules in living cells. Since the targetting and catalytic domains are affected differently by phosphorylation the model provides a basis for studying the regulation of the interaction between microtubules and tau or other microtubule-associated proteins.
tau蛋白是一种与神经元微管相关的蛋白质，可促进微管组装。该蛋白的C端含有三个或四个串联重复序列，通常被认为是微管结合结构域。这一观点与体外实验数据相矛盾，体外实验数据表明，即使在没有重复序列的情况下，重复结构域与微管的结合也很弱，而重复序列两侧的结构域与微管的结合很强。这使我们提出了tau蛋白的“钳口”模型，据此，重复序列两侧的区域被视为靶向结构域，负责将tau蛋白定位在微管表面，而重复序列则作为微管组装的催化结构域。为了检验该模型在体内是否适用，我们制备了重组tau蛋白异构体并将其显微注射到CHO细胞中。对微管和tau蛋白进行免疫荧光显微镜观察发现，仅包含单个结构域的tau蛋白构建体无法实现与微管的结合、微管的稳定以及束状结构的形成，而是需要侧翼区域和重复结构域的组合。结果表明，“钳口”模型描述了活细胞中tau蛋白与微管之间的相互作用。由于靶向结构域和催化结构域受磷酸化的影响不同，该模型为研究微管与tau蛋白或其他微管相关蛋白之间相互作用的调控提供了基础。
