Non-canonical MAPK signaling in yeast

项目概要/摘要：丝裂原活化蛋白激酶（MAPK）是一个家族， 在许多人类疾病中失调的保守信号酶。许多 MAPK在经典信号通路中被MAPK激酶激活。这 活化机制已得到充分研究。其他的MAPK在非- 典型的信号通路通过结合蛋白，触发自磷酸化的 MAPK。关于这种激活机制以及它是如何 监管.酵母酿酒酵母是一个强大的模型系统，其中， 研究MAPK信号通路。Smk 1是酵母中减数分裂特异性MAPK，在细胞分裂中被激活。 结合蛋白Ssp 2通过非经典途径，因为减数分裂正在进行， 完成Smk 1然后通过以下方式控制配子（孢子）形成的减数分裂后程序： 磷酸化调节底物。后期促进复合物（APC）E3 泛素连接酶是染色体分离的关键调节因子。APC还发挥着 在将动物细胞的分化与细胞周期的G1/G 0期偶联中的作用。 Ssp 2激活Smk 1需要APC，但将APC与Smk 1连接的机制不清楚。 MAPK的激活直到最近才为人所知。在初步数据中，Isc 10已经被 被鉴定为将APC与Smk 1激活联系起来的抑制性蛋白。一个工作模型 对于该途径，假定Isc 10与Smk 1和Ssp 2在细胞质中形成复合物 准备激活的减数分裂细胞在这个模型中，平衡的三元复合物是 导入细胞核，其中细胞核常驻APC，与减数分裂特异性 靶向亚基Ama 1在减数分裂后期II触发Isc 10的泛素化。 这使得Ssp 2能够激活Smk 1的分子内自磷酸化，从而 激活MAPK，将孢子分化与核分裂完成偶联， 种族隔离为了测试和扩展这个模型，我们将：1-阐明如何抑制蛋白 Isc 10控制Smk 1激活，2-解密时空调节， MAPKs的APC，3-确定如何激活Smk 1控制减数分裂后的过程。 从这些研究中获得的见解将与控制MAPK的机制广泛相关 在发展计划的背景下，以及APC如何耦合 在高等真核生物的细胞周期分化程序。

Project Summary/Abstract: Mitogen activated protein kinases (MAPKs) are a family of conserved signaling enzymes that are dysregulated in numerous human diseases. Many MAPKs are activated in canonical signaling pathways by MAPK kinases. This mechanism of activation has been well-studied. Other MAPKs are activated in non- canonical signaling pathways by binding proteins that trigger autophosphorylation of the MAPK. Relatively little is known about this mechanism of activation and how it is regulated. The yeast Saccharomyces cerevisiae is a powerful model system in which to study MAPK signaling. Smk1 is a meiosis-specific MAPK in yeast that is activated in a non-canonical pathway by a binding protein, Ssp2, as the meiotic divisions are being completed. Smk1 then controls the post-meiotic program of gamete (spore) formation by phosphorylating regulatory substrates. The anaphase promoting complex (APC) E3 ubiquitin-ligase is a key regulator of chromosome segregation. The APC also plays a role in coupling the differentiation of animal cells to the G1/G0 phase of the cell-cycle. The APC is required for Ssp2 to activate Smk1 yet the mechanism linking the APC to MAPK activation was until recently unknown. In preliminary data, Isc10 has been identified as an inhibitory protein that links the APC to Smk1 activation. A working model for this pathway posits that Isc10 forms a complex with Smk1 and Ssp2 in the cytoplasm of meiotic cells that is poised for activation. In this model, the poised ternary complex is imported into nuclei, where the nuclear resident APC, complexed with a meiosis-specific targeting subunit, Ama1, triggers ubiquitylation of Isc10 after anaphase of meiosis II. This allows Ssp2 to activate the intramolecular autophosphorylation of Smk1, thereby activating the MAPK and coupling spore differentiation to the completion of nuclear segregation. To test and extend this model we will: 1- Elucidate how the inhibitor protein Isc10 controls Smk1 activation, 2- Decipher the spatiotemporal regulation that links MAPKs to the APC, 3- Determine how activated Smk1 controls post-meiotic processes. Insights from these studies will be broadly relevant to mechanisms that control MAPK signaling in the context of developmental programs and how the APC couples differentiation programs to the cell-cycle in higher eukaryotes.