Molecular mechanism of cytokinesis

（1）认为有丝分裂器向细胞皮质传递某种信号，使收缩环在适当的位置形成。然而，其机制尚未阐明。我研究了小麦胚芽凝集素（WGA）受体在这一过程中的作用，使用荧光素标记的WGA。WGA受体在中期分布于卵表面。在后期，它们聚集成团，后期变成纤维状。在末期，它们聚集在预期的犁沟区域，形成一个环。上面观察到的分布与荧光鬼笔环肽染色观察到的肌动蛋白丝非常相似。研究表明，WGA受体与细胞膜上的肌动蛋白结合位点有着密切的关系。否定了受体先聚集在预期的沟区，然后诱导肌动蛋白丝组装的可能性。2)当未受精的海胆卵与抑制蛋白磷酸酶活性的海绵毒素calyculin A孵育时，诱导卵裂。这些卵既不形成有丝分裂器，也不形成紫苑。肌动蛋白，肌球蛋白，和WGA受体积累在沟区。该过程被蛋白激酶抑制剂抑制。这表明蛋白磷酸化参与收缩环的形成。此外，染色体被浓缩，组蛋白1激酶活性以不依赖于细胞周期蛋白B的方式增加。3)去年，我报道了分离的卵裂沟从Clypeaster的卵使用洗涤剂含有培养基。我扩大了对奇异毛蟹卵的隔离。我还分离出clevage沟从卵Anthocidaris crassispina和Hemicentrotus pulcherrimus使用改进的培养基。我们在2-D凝胶中发现了这些卵共有的几种蛋白质，现在正在确定部分肽序列。

1)It has been considered that some signal is transfered from the mitotic apparatus to the cell cortex in order to form the contractile ring at a proper position. However, its mechanism has not been clarified yet. I investigated role of wheat germ agglutinin (WGA) receptors in this process, using fluorescein-labeled WGA. WGA receptors distributed on the surface of the egg during metaphase. They were aggregated into clusters during anaphase, which became fibrous in late anaphase. At telophase, they accumulated in the anticipated furrow region forming a ring. The distribution observed above was quite similar to that of actin filaments visualized by fluorescent phalloidin staining. It has been shown that the WGA receptors have intimate relationship to actin filament-anchoring sites on the plasma membrane. A possibility was denied that the receptors accumulate in the anticipated furrow region at first and then induce actin filament assembly. 2) When the unfertilized sea urchin eggs were incubated with calyculin A, a sponge toxin which inhibits activities of protein phopsphatases, cleavage was induced. Neither mitotic apparatus nor aster was formed in these eggs. Actin, myosin, and WGA receptors were accumulated in the furrow region. This process was inhibited by protein kinase inhibitors. It is suggested that protein phosphorylation is involved in the contractile ring formation. In addition, chromosomes were condensed and histone 1 kinase activity was increased in a cyclin Bindependent manner. 3) Last year, I reported isolation of cleavage furrows from Clypeaster japonicus eggs using a detergent-containing medium. I extended the isolation with Scaphechinus mirabilis eggs. I also isolated clevage furrows from eggs of Anthocidaris crassispina and Hemicentrotus pulcherrimus using modified medium. We found several proteins in 2-D gels common to these eggs and now determining partial peptide sequences.