CaMKII and Polo-like kinase 1 sequentially phosphorylate the cytostatic factor Emi2/XErp1 to trigger its destruction and meiotic exit
CaMKII and Polo-like kinase 1 sequentially phosphorylate the cytostatic factor Emi2/XErp1 to trigger its destruction and meiotic exit
复制标题
DOI：
10.1073/pnas.0509549102
复制
发表时间：
2006-01-17
影响因子：
11.1
通讯作者：
Jackson, PK
中科院分区：
文献类型：
--
作者：
Hansen, DV;Tung, JJ;Jackson, PK
在脊椎动物减数分裂中，未受精卵被细胞抑制因子(CSF)阻止在中期II，这是维持有丝分裂周期蛋白依赖的激酶活性所必需的。受精后细胞内游离钙离子瞬间增加，导致脑脊液失活，并通过后期促进复合体或环体(APC/C)破坏泛素依赖的细胞周期蛋白。钙/钙调蛋白依赖的蛋白激酶II(CaMKII)和Polo-like kinasePlx1是钙离子诱导的减数分裂退出的关键因子，但这些激酶的关键靶点尚不清楚。APC/C抑制剂Emi2或XErp1最近被认为是维持中期11停滞所需的关键脑脊液成分，并通过Plx1的磷酸化和SCFβTrCP复合体的泛素化来响应钙信号而迅速被破坏。一个重要的问题是，游离钙离子的增加如何将Plx1的活性导向Emi2。在这里，我们证明了CaMKII是钙离子诱导的Emi2破坏所必需的，并且CaMKII起着“启动激酶”的作用，直接在特定的基序上磷酸化Emi2，诱导与Plx1的Polo Box结构域的强烈相互作用。我们证明了对CaMKII磷酸化Emi2的严格要求是脑脊液抑制的一个特殊特征，我们还使用磷酸酶抑制剂来证明Emi2的另一种失活模式独立于它的破坏。我们坚定地确立了脑脊液成分Emi2是第一个已知的CaMKII在脑脊液释放中的关键和直接靶标，提供了一个详细的分子机制来解释CaMKII和Plx1如何协调地指导APC/C的激活和受精后的减数分裂退出。
In vertebrate meiosis, unfertilized eggs are arrested in metaphase II by cytostatic factor (CSF), which is required to maintain mitotic cyclin-dependent kinase activity. Fertilization triggers a transient increase in cytosolic free Ca2+, which leads to CSF inactivation and ubiquitin-dependent cyclin destruction through the anaphase promoting complex or cyclosome (APC/C). The Ca2+/calmodulin-dependent protein kinase II (CaMKII) and the Polo-like kinase Plx1 are essential factors for Ca2+-induced meiotic exit, but the critical targets of these kinases were unknown. The APC/C inhibitor Emi2 or XErp1 has recently been characterized as a pivotal CSF component, required to maintain metaphase 11 arrest and rapidly destroyed in response to Ca2+ signaling through phosphorylation by Plx1 and ubiquitination by the SCFbeta TrCP complex. An important question is how the increase in free Ca2+ targets Plx1 activity toward Emi2. Here, we demonstrate that CaMKII is required for Ca2+-induced Emi2 destruction, and that CaMKII functions as a "priming kinase," directly phosphorylating Emi2 at a specific motif to induce a strong interaction with the Polo Box domain of Plx1. We show that the strict requirement for CaMKII to phosphorylate Emi2 is a specific feature of CSF arrest, and we also use phosphatase inhibitors to demonstrate an additional mode of Emi2 inactivation independent of its destruction. We firmly establish the CSF component Emi2 as the first-known critical and direct target of CaMKII in CSF release, providing a detailed molecular mechanism explaining how CaMKII and Plx1 coordinately direct APC/C activation and meiotic exit upon fertilization.