Okadaic acid overcomes the blocked cell cycle caused by depleting Cdc2-related kinases in Trypanosoma brucei
Okadaic acid overcomes the blocked cell cycle caused by depleting Cdc2-related kinases in Trypanosoma brucei
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DOI：
10.1016/j.yexcr.2006.07.022
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发表时间：
2006-11-01
影响因子：
3.7
通讯作者：
Wang, Ching C.
中科院分区：
文献类型：
--
作者：
Li, Ziyin;Tu, Xiaoming;Wang, Ching C.
有丝分裂和胞质分裂在真核细胞中是高度协调的。但是处于G1期或有丝分裂停滞的布氏锥虫前循环型仍然能够分裂，产生无核子细胞（类虫体）。冈田酸（OKA）是蛋白磷酸酶PP1和PP2A的抑制剂，已知它能抑制动基体复制和细胞分裂，产生具有单个动基体的多核细胞。然而，当通过RNA干扰特异性cdc2相关激酶（CRKs）的敲低使细胞停滞在G1或G2/M期时，DNA合成和核分裂在没有动基体复制或细胞分裂的情况下恢复，像在野生型中一样产生多核细胞。然而，通过消耗有丝分裂细胞周期蛋白CycB2或极光B激酶同源物TbAUK1而停滞在G2/M期的细胞，并没有因OKA处理而被解除停滞。因此这种现象类似于通过抑制PP2A激活非洲爪蟾卵母细胞中的Cdc2 [Maton等人，非洲爪蟾卵母细胞中Cdc2和极光 - A的差异调节：磷酸酶2A的关键作用。《细胞科学杂志》118（2005）2485 - 2494]。然而，通过RNA干扰同时敲低布氏锥虫中的7种PP1或PP2A催化亚基并没有产生多核细胞。这可以通过假设一种OKA敏感的磷酸酶直接或间接对CRK进行负调控来解释，这种磷酸酶可能像在非洲爪蟾卵母细胞中一样是PP2A，以及一种OKA敏感的蛋白质对动基体复制进行正调控。对一种PP2A特异性抑制剂福司曲星在通过CRK消耗而停滞在G2/M期的细胞上进行测试，或者从CRK消耗的细胞中敲低PP2A催化亚基，都显示G2/M期阻滞部分解除但没有形成多核细胞。这些观察结果支持上述假设，并表明存在一种新的OKA敏感的调节动基体复制的蛋白质，其仍有待鉴定。（c）2006爱思唯尔公司。保留所有权利。
Mitosis and cytokinesis are highly coordinated in eukaryotic cells. But procyclic-form Trypanosoma brucei under GI or mitotic arrest is still capable of dividing, resulting in anucleate daughter cells (zoids). Okadaic acid (OKA), an inhibitor of protein phosphatases PP1 and PP2A, is known to inhibit kinetoplast replication and cell division yielding multinucleate cells with single kinetoplasts. However, when OKA was applied to cells arrested in G1 or G2/M phase via RNAi knockdown of specific cdc2-related kinases (CRKs), DNA synthesis and nuclear division were resumed without kinetoplast replication or cell division, resulting in multinucleate cells as in the wild type. Cells arrested in G2/M via depleting the mitotic cyclin CycB2 or an aurora B kinase homologue TbAUK1 were, however, not released by OKA treatment. The phenomenon is thus similar to the OKA activation of Cdc2 in Xenopus oocyte by inhibiting PP2A [Maton, et al., Differential regulation of Cdc2 and Aurora-A in Xenopus oocytes: a crucial role of phosphatase 2A. J. Cell Sci. 118 (2005) 2485-2494]. A simultaneous knockdown of the seven PP1s or the PP2A catalytic subunit in T. brucei by RNA interference did not, however, result in multinucleate cells. This could be explained by assuming a negative regulation, either directly or indirectly, of CRK by an OKA-sensitive phosphatase, which could be a PP2A as in the Xenopus oocyte and a positive regulation of kinetoplast replication by an OKA-susceptible protein(s). Test of a PP2A-specific inhibitor, fostriecin, on cells arrested in G2/M via CRK depletion or a knockdown of the PP2A catalytic subunit from the CRK-depleted cells both showed a partial lift of the G2/M block without forming multinucleate cells. These observations support the abovementioned assumption and suggest the presence of a novel OKA-sensitive protein(s) regulating kinetoplast replication that still remains to be identified. (c) 2006 Elsevier Inc. All rights reserved.