Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan.
Cytoskeleton (Hoboken). 2012 Nov;69(11):913-8. doi: 10.1002/cm.21072. Epub 2012 Oct 1.
Cytokinesis in eukaryotes involves specific arrays of microtubules (MTs), which are known as the central spindle in animals, the anaphase spindle in yeasts, and the phragmoplast in plants. In plants, a mitogen-activated protein kinase (MAPK) cascade stimulates the turnover of phragmoplast MTs, which allows the expansion of the phragmoplast that is essential for cytokinesis including the formation of cell plates. A prerequisite for activation of this cascade is the interaction between mitotic kinesin NACK1 in tobacco (HINKEL in Arabidopsis) and MAPK kinase kinase NPK1 (ANP1, 2, 3 in Arabidopsis). Other members of this cascade are NQK1 MAPK kinase and NRK1/NTF6 MAPK in tobacco and the respective orthologs in Arabidopsis. All the components in the pathway (designated the NACK-PQR pathway) concentrate at the midzone of the phragmoplast in plant cells during cytokinesis. Downstream MAPKs in both plant species phosphorylate microtubule-associated protein 65 (MAP65). Interestingly, activities of components in the NACK-PQR pathway are downregulated by depolymerization of MTs. In the present review, we summarize current views on the mechanisms involved in activating the kinase cascade, a role of MAP65 phosphorylation by MAPK during cytokinesis, and the feedback mechanism for regulating inactivation of the kinase cascade.
真核细胞的胞质分裂涉及特定的微管（MTs）阵列，这些微管在动物中被称为中心纺锤体，在酵母中称为后期纺锤体，在植物中称为成膜体。在植物中，丝裂原激活蛋白激酶（MAPK）级联反应刺激成膜体 MT 的周转，这允许成膜体的扩展，这对于胞质分裂包括细胞板的形成是必不可少的。该级联反应的激活前提是烟草有丝分裂驱动蛋白 NACK1（拟南芥中的 HINKEL）与 MAPK 激酶激酶 NPK1（拟南芥中的 ANP1、2、3）之间的相互作用。该级联反应的其他成员是烟草中的 NQK1 MAPK 激酶和 NRK1/NTF6 MAPK 以及拟南芥中的相应同源物。该途径（指定为 NACK-PQR 途径）中的所有成分在植物细胞的胞质分裂过程中都集中在成膜体的中部区。在这两个植物物种中，下游 MAPK 磷酸化微管相关蛋白 65（MAP65）。有趣的是，MT 解聚下调了 NACK-PQR 途径中的成分活性。在本综述中，我们总结了目前关于激活激酶级联反应的机制、MAPK 在胞质分裂过程中磷酸化 MAP65 的作用以及调节激酶级联反应失活的反馈机制的观点。
