LIM kinase-mediated cofilin phosphorylation during mitosis is required for precise spindle positioning
LIM kinase-mediated cofilin phosphorylation during mitosis is required for precise spindle positioning
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DOI：
10.1074/jbc.m708644200
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发表时间：
2008-02-22
影响因子：
4.8
通讯作者：
Mizuno, Kensaku
中科院分区：
文献类型：
--
作者：
Kaji, Noriko;Muramoto, Aya;Mizuno, Kensaku
星体微管与皮质肌动蛋白网络的相互作用对有丝分裂纺锤体的正确定向至关重要；然而，在有丝分裂过程中，皮层肌动蛋白组织是如何被调节的，我们所知甚少。LIM激酶-1 （LIMK1）通过磷酸化和灭活cofilin（一种肌动蛋白解聚蛋白）来调节肌动蛋白动力学。有丝分裂时LIMK1活性增加。在这里，我们发现有丝分裂LIMK1的激活对于哺乳动物细胞准确的纺锤体定向至关重要。LIMK1的下调抑制了有丝分裂特异性的cofilin磷酸化的增加，并导致中期细胞皮层异常的cofilin定位，皮层肌动蛋白组织和星状微管的不稳定，纺锤体的不规则旋转和错位，以及后期发作的延迟。用LIMK1抑制剂肽或latrunculin a处理细胞或过表达非磷酸化的cofilin（S3A）突变体也获得了类似的结果。此外，在LIMK1敲低的细胞中，作为纺锤体取向重要调节因子的LGN（一种含有重复Leu-Gly-Asn三肽基序的蛋白质）在月牙形皮质区域的定位受到干扰。我们的研究结果表明，在有丝分裂期间，limk1介导的cofilin磷酸化是通过稳定皮质肌动蛋白网络来实现准确纺锤体定向所必需的。
The interaction of astral microtubules with cortical actin networks is essential for the correct orientation of the mitotic spindle; however, little is known about how the cortical actin organization is regulated during mitosis. LIM kinase-1 (LIMK1) regulates actin dynamics by phosphorylating and inactivating cofilin, an actin-depolymerizing protein. LIMK1 activity increases during mitosis. Here we show that mitotic LIMK1 activation is critical for accurate spindle orientation in mammalian cells. Knockdown of LIMK1 suppressed a mitosis-specific increase in cofilin phosphorylation and caused unusual cofilin localization in the cell cortex in metaphase, instability of cortical actin organization and astral microtubules, irregular rotation and misorientation of the spindle, and a delay in anaphase onset. Similar results were obtained by treating the cells with a LIMK1 inhibitor peptide or latrunculin A or by overexpressing a non-phosphorylatable cofilin(S3A) mutant. Furthermore, localization of LGN (a protein containing the repetitive Leu-Gly-Asn tripeptide motifs), an important regulator of spindle orientation, in the crescent-shaped cortical regions was perturbed in LIMK1 knockdown cells. Our results suggest that LIMK1-mediated cofilin phosphorylation is required for accurate spindle orientation by stabilizing cortical actin networks during mitosis.