Heilig Yvonne, Dettmann Anne, Mouriño-Pérez Rosa R, Schmitt Kerstin, Valerius Oliver, Seiler Stephan
Institute for Biology II - Molecular Plant Physiology, Albert-Ludwigs University Freiburg, Freiburg, Germany.
Department of Microbiology, Center for Scientific Research and Higher Education of Ensenada (CICESE), Baja California, Mexico.
PLoS Genet. 2014 Apr 24;10(4):e1004306. doi: 10.1371/journal.pgen.1004306. eCollection 2014 Apr.
Nuclear DBF2p-related (NDR) kinases constitute a functionally conserved protein family of eukaryotic regulators that control cell division and polarity. In fungi, they function as effector kinases of the morphogenesis (MOR) and septation initiation (SIN) networks and are activated by pathway-specific germinal centre (GC) kinases. We characterized a third GC kinase, MST-1, that connects both kinase cascades. Genetic and biochemical interactions with SIN components and life cell imaging identify MST-1 as SIN-associated kinase that functions in parallel with the GC kinase SID-1 to activate the SIN-effector kinase DBF-2. SID-1 and MST-1 are both regulated by the upstream SIN kinase CDC-7, yet in an opposite manner. Aberrant cortical actomyosin rings are formed in Δmst-1, which resulted in mis-positioned septa and irregular spirals, indicating that MST-1-dependent regulation of the SIN is required for proper formation and constriction of the septal actomyosin ring. However, MST-1 also interacts with several components of the MOR network and modulates MOR activity at multiple levels. MST-1 functions as promiscuous enzyme and also activates the MOR effector kinase COT-1 through hydrophobic motif phosphorylation. In addition, MST-1 physically interacts with the MOR kinase POD-6, and dimerization of both proteins inactivates the GC kinase hetero-complex. These data specify an antagonistic relationship between the SIN and MOR during septum formation in the filamentous ascomycete model Neurospora crassa that is, at least in part, coordinated through the GC kinase MST-1. The similarity of the SIN and MOR pathways to the animal Hippo and Ndr pathways, respectively, suggests that intensive cross-communication between distinct NDR kinase modules may also be relevant for the homologous NDR kinases of higher eukaryotes.
核DBF2p相关(NDR)激酶构成了一个功能保守的真核生物调节蛋白家族,其控制细胞分裂和极性。在真菌中,它们作为形态发生(MOR)和隔膜起始(SIN)网络的效应激酶发挥作用,并被特定途径的生发中心(GC)激酶激活。我们鉴定了第三种GC激酶MST-1,它连接了这两个激酶级联反应。与SIN成分的遗传和生化相互作用以及活细胞成像确定MST-1为与SIN相关的激酶,其与GC激酶SID-1平行发挥作用以激活SIN效应激酶DBF-2。SID-1和MST-1均受上游SIN激酶CDC-7的调节,但方式相反。在Δmst-1中形成异常的皮质肌动球蛋白环,这导致隔膜定位错误和螺旋不规则,表明SIN的MST-1依赖性调节是隔膜肌动球蛋白环正确形成和收缩所必需的。然而,MST-1也与MOR网络的几个成分相互作用,并在多个水平上调节MOR活性。MST-1作为一种多效性酶,还通过疏水基序磷酸化激活MOR效应激酶COT-1。此外,MST-1与MOR激酶POD-6发生物理相互作用,并且两种蛋白质的二聚化使GC激酶异源复合物失活。这些数据表明在丝状子囊菌模型粗糙脉孢菌的隔膜形成过程中,SIN和MOR之间存在拮抗关系,这至少部分是通过GC激酶MST-1协调的。SIN和MOR途径分别与动物Hippo和Ndr途径的相似性表明,不同NDR激酶模块之间的密集交叉通讯可能也与高等真核生物的同源NDR激酶相关。