Non-canonical MAPK signaling in yeast

项目摘要/摘要：丝裂原活化蛋白激酶(MAPK)是一类 保守的信号酶，在许多人类疾病中都是不受调控的。许多 MAPK在典型的信号通路中被MAPK激酶激活。这 活化机理已经得到了很好的研究。其他MAPK在非 通过结合蛋白来触发自磷酸化的典型信号通路 MAPK。对于这种激活机制以及它是如何被激活的，人们知之甚少 受监管的。酵母酿酒酵母是一个强大的模型系统，在其中 研究MAPK信号转导。Smk1是酵母中一种减数分裂特异的MAPK，它在一种 结合蛋白Ssp2的非经典途径，因为减数分裂正在进行 完成。然后Smk1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。后期促进复合体(APC)E3 泛素连接酶是染色体分离的关键调节因子。APC还扮演着一个 在将动物细胞分化耦合到细胞周期的G1/G0期中的作用。 Ssp2需要APC才能激活SMK1，但将APC链接到 直到最近，MAPK的激活还不得而知。在初步数据中，Isc10已经被 被鉴定为一种抑制蛋白，将APC与Smk1激活联系在一起。一个工作模式 因为这个途径假设Isc10在细胞质中与Smk1和Ssp2形成一个复合体 准备激活的减数分裂细胞。在这个模型中，稳定的三元络合物是 进入细胞核，在那里的核驻留APC，与减数分裂特异的复合体 靶向亚基AMA1在减数分裂II后期触发Isc10的泛素化。 这允许Ssp2激活Smk1的分子内自动磷酸化，从而 激活MAPK和偶联孢子分化完成核 种族隔离。为了测试和扩展这个模型，我们将：1-阐明抑制蛋白是如何 ISC10控制SMK1的激活，2-破译连接的时空规律 MAPKs到APC，3-确定激活的Smk1如何控制减数分裂后过程。 来自这些研究的见解将广泛地与控制MAPK的机制相关 发育计划背景下的信号以及APC如何配对 高等真核生物细胞周期的分化程序。

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.