Nilsson H, Wallin M
Göteborg University, Department of Zoology, Zoophysiology, Sweden.
Cell Motil Cytoskeleton. 1998;41(3):254-63. doi: 10.1002/(SICI)1097-0169(1998)41:3<254::AID-CM6>3.0.CO;2-4.
The interplay between microtubules and the motor enzyme, cytoplasmic dynein, is essential for organisation of the cytoplasm, organelle transport, and cell division in eukaryotic cells. During mitosis, cytoplasmic dynein organises microtubules into two spindle pole asters, as well as the comparable multiple cytoplasmic asters induced by the microtubule-stabilising agent taxol. The mechanisms behind this cell cycle-regulated organisation are, however, not fully understood. We report here that the unidirectional dynein-dependent pigment organelle aggregation in taxol-treated melanophores from Atlantic cod, induces multiple microtubule asters. Usually, the pigment aggregates to a central pigment mass in the cell center, but pigment aggregation in taxol-treated cells induces formation of several peripheral pigment clusters that each localise to the center of a microtubule aster formation. When a cell with previously formed peripheral pigment clusters redisperse pigment, the asters disappear. Upon a subsequent reaggregation of the pigment, the aster formations reappear. The results indicate that the pigment aggregation process organises the microtubules into these formations. Immuno-electron microscopy of isolated pigment organelles indicates the presence of several dynein molecules on each pigment organelle, making it possible for each organelle to interact with several microtubules and thereby focusing microtubule minus ends. The possibility of unidirectional dynein-dependent organelle movement for organising microtubules into asters during cell division, and similarities in signal transduction between mitosis and pigment movement, are discussed.
微管与运动酶胞质动力蛋白之间的相互作用对于真核细胞的细胞质组织、细胞器运输和细胞分裂至关重要。在有丝分裂期间，胞质动力蛋白将微管组织成两个纺锤体极星状体，以及由微管稳定剂紫杉醇诱导的类似多个细胞质星状体。然而，这种细胞周期调节组织背后的机制尚未完全了解。我们在此报告，在经紫杉醇处理的大西洋鳕鱼黑素细胞中，单向动力蛋白依赖性色素细胞器聚集会诱导多个微管星状体形成。通常，色素会聚集到细胞中心的一个中央色素团块中，但在经紫杉醇处理的细胞中，色素聚集会诱导形成几个外周色素簇，每个外周色素簇都定位于微管星状体形成的中心。当一个具有先前形成的外周色素簇的细胞重新分散色素时，星状体消失。在色素随后重新聚集时，星状体形成再次出现。结果表明，色素聚集过程将微管组织成这些结构。对分离的色素细胞器进行免疫电子显微镜检查表明，每个色素细胞器上存在几个动力蛋白分子，这使得每个细胞器能够与多个微管相互作用，从而使微管负端聚焦。本文还讨论了在细胞分裂过程中单向动力蛋白依赖性细胞器运动将微管组织成星状体的可能性，以及有丝分裂和色素运动之间信号转导的相似性。
