A new identity for MLK3 as an NIMA-related, cell cycle-regulated kinase that is localized near centrosomes and influences microtubule organization.
A new identity for MLK3 as an NIMA-related, cell cycle-regulated kinase that is localized near centrosomes and influences microtubule organization.
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DOI：
10.1091/mbc.e02-02-0115
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发表时间：
2003
影响因子：
3.3
通讯作者：
K. Swenson;K. Winkler;A. Means
中科院分区：
文献类型：
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作者：
K. Swenson;K. Winkler;A. Means
虽然在所有真核生物中都发现了参与细胞周期G（2）/M转换的大多数蛋白质的保守对应物，但一个值得注意的例外是必需的但功能神秘的真菌激酶NIMA。虽然许多脊椎动物激酶已被确定与NIMA的催化结构域同源性，没有这些类似NIMA在其广泛的非催化区域，一个区域的NIMA功能构巢曲霉。我们使用生物信息学的方法来寻找与NIMA的非催化区同源的蛋白质，并确定了混合谱系激酶3（MLK 3）。MLK 3已被提议用作MAP激酶级联的组分，特别是导致c-Jun N-末端激酶（JNK）活化的那些。在这里，我们描述了内源性MLK 3的第一次深入研究，并报告说，像NIMA，MLK 3的磷酸化和活性增强在G（2）/M，而JNK保持无活性。与G（2）/M转换相一致，这一时期的标志是细胞质微管网络的急剧重组，内源性MLK 3短暂分散远离中心体和中心体近端位点，在间期定位。此外，当过表达时，MLK 3像NIMA一样定位于中心体区域，诱导细胞质微管的深刻破坏和不同于有丝分裂染色体浓缩的核畸变表型。使用siRNA技术的MLK 3蛋白的细胞消耗导致对微管稳定剂紫杉醇的敏感性增加。我们的研究表明MLK 3的一个新作用，与其在JNK通路中的功能分离，可能有助于促进微管不稳定性，这是M期进入的标志。
Although conserved counterparts for most proteins involved in the G(2)/M transition of the cell cycle have been found in all eukaryotes, a notable exception is the essential but functionally enigmatic fungal kinase NIMA. While a number of vertebrate kinases have been identified with catalytic domain homology to NIMA, none of these resemble NIMA within its extensive noncatalytic region, a region critical for NIMA function in Aspergillus nidulans. We used a bioinformatics approach to search for proteins with homology to the noncatalytic region of NIMA and identified mixed lineage kinase 3 (MLK3). MLK3 has been proposed to serve as a component in MAP kinase cascades, particularly those resulting in the activation of the c-Jun N-terminal kinase (JNK). Here we describe the first in-depth study of endogenous MLK3 and report that, like NIMA, MLK3 phosphorylation and activity are enhanced during G(2)/M, whereas JNK remains inactive. Coincident with the G(2)/M transition, a period marked by dramatic reorganization of the cytoplasmic microtubule network, endogenous MLK3 transiently disperses away from the centrosome and centrosomal-proximal sites where it is localized during interphase. Furthermore, when overexpressed, MLK3, like NIMA, localizes to the centrosomal region, induces profound disruption of cytoplasmic microtubules and a nuclear distortion phenotype that differs from mitotic chromosome condensation. Cellular depletion of MLK3 protein using siRNA technology results in an increased sensitivity to the microtubule-stabilizing agent taxol. Our studies suggest a new role for MLK3, separable from its function in the JNK pathway, that may contribute to promoting microtubule instability, a hallmark of M phase entry.