Baas P W, Pienkowski T P, Kosik K S
Department of Anatomy, University of Wisconsin Medical School, Madison 53706.
J Cell Biol. 1991 Dec;115(5):1333-44. doi: 10.1083/jcb.115.5.1333.
We have indirectly analyzed the role of tau in generating the highly organized microtubule (MT) array of the axon. Axons contain MT arrays of uniform polarity orientation, plus ends distal to the cell body (Heidemann, S. R., J. M. Landers, and M. A. Hamborg. 1981. J. Cell Biol. 91:661-673). Surprisingly, these MTs do not radiate from a single discrete nucleating structure in the cell body (Sharp, G. A., K. Weber, and M. Osborn. 1982. Eur. J. Cell Biol. 29: 97-103), but rather stop and start at multiple sites along the length of the axon (Bray, D., and M. B. Bunge. 1981. J. Neurocytol. 10:589-605). When Sf9 ovarian cells are induced to express high levels of tau protein, they develop cellular processes which are similar in appearance to axons and which contain dense arrays of MTs (Knops, J., K. S. Kosik, G. Lee, J. D. Pardee, L. Cohen-Gould, and L. McConlogue. 1991. J. Cell Biol. 114:725-734). We have analyzed the organization of MTs within these arrays, and determined it to be similar, but not identical, to the organization of MTs within the axon. The caliber, MT number, and MT density vary significantly from process to process, but on average are manyfold higher in the tau-induced processes than typically found in axons. Greater than 89% of the MTs in the processes are oriented with their plus ends distal to the cell body, and this proportion is even higher in the processes that are most similar to axons with regard to caliber, MT number, and MT density. Similar to the situation in the axon, MTs are discontinuous along the length of the tau-induced processes, and do not emanate from any observable nucleating structure in the cell body. We have also identified bundles of MTs throughout the cell bodies of the Sf9 cells induced to express tau. Similar to the MT arrays in the processes, these MT bundles are not visibly associated with any other cytological structures that might regulate their polarity orientation. Nevertheless, these bundles consist of MTs most (greater than 82%) of which have the same polarity orientation. Collectively, these results suggest that tau may play a fundamental role in generating MT organization in the axon. In particular, a key property of tau may be to bundle MTs preferentially with the same polarity orientation.
我们间接分析了tau蛋白在生成轴突中高度有序的微管（MT）阵列方面的作用。轴突含有极性方向一致的MT阵列，其正端远离细胞体（海德曼，S.R.，J.M.兰德斯和M.A.汉伯格。1981年。《细胞生物学杂志》91:661 - 673）。令人惊讶的是，这些MT并非从细胞体中的单个离散成核结构发出（夏普，G.A.，K.韦伯和M.奥斯本。1982年。《欧洲细胞生物学杂志》29:97 - 103），而是在轴突长度上的多个位点终止和起始（布雷，D.和M.B.邦奇。1981年。《神经细胞生物学杂志》10:589 - 605）。当Sf9卵巢细胞被诱导高表达tau蛋白时，它们会形成外观类似于轴突且含有密集MT阵列的细胞突起（克诺普斯，J.，K.S.科西克，G.李，J.D.帕迪，L.科恩 - 古尔德和L.麦康洛格。1991年。《细胞生物学杂志》114:725 - 734）。我们分析了这些阵列中MT的组织情况，并确定其与轴突中MT的组织情况相似但不完全相同。不同突起之间的管径、MT数量和MT密度差异显著，但平均而言，tau诱导的突起中的这些指标比轴突中通常所见的要高许多倍。突起中超过89%的MT其正端远离细胞体，在管径、MT数量和MT密度方面与轴突最相似的突起中，这一比例甚至更高。与轴突中的情况类似，MT在tau诱导的突起长度上是不连续的，且并非从细胞体中任何可观察到的成核结构发出。我们还在诱导表达tau的Sf9细胞的整个细胞体中鉴定出了MT束。与突起中的MT阵列类似，这些MT束与任何可能调节其极性方向的其他细胞学结构没有明显关联。然而，这些束由MT组成，其中大多数（超过82%）具有相同的极性方向。总体而言，这些结果表明tau可能在轴突中MT组织的生成中起基本作用。特别是，tau的一个关键特性可能是优先将具有相同极性方向的MT捆绑在一起。
