Sudo Haruka, Maru Yoshiro
Department of Pharmacology, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjuku-ku, Tokyo 162-8666, Japan.
Hum Mol Genet. 2008 Aug 15;17(16):2524-40. doi: 10.1093/hmg/ddn153. Epub 2008 May 18.
Human chromosome region 10q23-24 is one of the most frequently found regions that show loss of heterozygosity in prostate cancers. A candidate tumor suppressor LAPSER1/LZTS2 (LAPSER1) is located in 10q24.3 that has been reported to be deleted as frequently as the neighboring PTEN locus. We previously reported that LAPSER1 binds p80 katanin, a subunit of the katanin heterodimer. In this report, we show that the LAPSER1 C terminal domain inhibits katanin-mediated microtubule severing in vitro and we detected this inhibition at centrosomes by tracing the nucleated de novo, severed, and transported microtubules in cells. This functional association is also supported by the intracellular localization. Centrosomal localization of LAPSER1 was independent of microtubules and was preferential to mother centrioles. In primary cultured neurons, LAPSER1 also colocalizes with p80 katanin. LAPSER1 alters cell proliferation by regulating cytokinesis. As subcellular mechanisms that underlie the tumor suppressive activity, exogenous LAPSER1 expression inhibited central spindle formation by abrogating microtubule transportation and a similar mode of inhibition was found in axogenesis. Katanin knockdown and dominant negative inhibitor of katanin provided similar phenotypes. Prophase LAPSER1 inhibited centrosomal gamma-tubulin accumulation, which resulted in retardation of mitotic entry. Furthermore, interphase inhibition of katanin by LAPSER1 expression resulted in prevention of cell motility that was accompanied by the increased acetylated microtubules. LAPSER1 knockdown increased cell migration that was inhibited by the expression of ninein, a microtubule release inhibitor. These results indicate that microtubule severing at centrosomes is a novel tumor-associated molecular subcircuit in cells, in which LAPSER1 is a regulator.
人类染色体区域10q23 - 24是前列腺癌中最常出现杂合性缺失的区域之一。候选肿瘤抑制因子LAPSER1/LZTS2（LAPSER1）位于10q24.3，据报道其缺失频率与邻近的PTEN基因座一样高。我们之前报道过LAPSER1与katanin异二聚体的一个亚基p80 katanin结合。在本报告中，我们表明LAPSER1的C末端结构域在体外抑制katanin介导的微管切断，并且通过追踪细胞中新生的、切断的和运输的微管，我们在中心体处检测到了这种抑制作用。这种功能关联也得到了细胞内定位的支持。LAPSER1在中心体的定位独立于微管，并且优先定位于母中心粒。在原代培养的神经元中，LAPSER1也与p80 katanin共定位。LAPSER1通过调节胞质分裂来改变细胞增殖。作为肿瘤抑制活性基础的亚细胞机制，外源性LAPSER1表达通过消除微管运输来抑制中央纺锤体形成，并且在轴突形成中也发现了类似的抑制模式。Katanin敲低和katanin的显性负性抑制剂产生了相似的表型。前期LAPSER1抑制中心体γ - 微管蛋白的积累，这导致有丝分裂进入延迟。此外，LAPSER1表达对katanin的间期抑制导致细胞运动性的预防，同时伴随着乙酰化微管的增加。LAPSER1敲低增加了细胞迁移，而微管释放抑制剂ninein的表达抑制了这种迁移。这些结果表明，中心体处的微管切断是细胞中一种新的肿瘤相关分子亚回路，其中LAPSER1是一种调节因子。
