Non-canonical MAPK signaling in yeast

项目概要/摘要：促分裂原活化蛋白激酶（MAPKs）是 在其活化过程中通过TXY基序的磷酸化而活化的信号传导酶 循环虽然双特异性MAPK激酶激活许多MAPK（典型信号传导）， 非典型激酶和自身磷酸化也可以激活MAPK（非典型的 信令）。关于经典信号通路在健康中的作用， 和疾病对非规范信号的了解要少得多。Smk 1是一个减数分裂- 酵母S.控制配子形成（孢子形成）的酿酒酵母 通过一个非经典的信号通路产生不同形式的MAPK， 在减数分裂的不同阶段。首先，CDK激活激酶Cak 1磷酸化 Smk 1在减数分裂发生时激活T残基。这 Smk 1的单磷酸化形式分布在整个细胞中。晚些 程序（在后期II），减数分裂特异性蛋白Ssp 2与Smk 1结合并激活 其Y残基的顺式自磷酸化。该反应发生在特定的 使这种特化细胞产生的单倍体细胞化的膜结构 师.因此，Ssp 2将双重磷酸化的MAPK脉冲传递到“右侧”， 在这个发展计划中的“正确时间”。这种时空特异性 通过Ssp 2蛋白的模块化实现;它通过靶向结构域（TD）定位， 它通过激酶激活结构域（KAD）激活MAPK的顺式自磷酸化。 Ssp 2KAD本身由结合Smk 1和调节RNA的片段组成 识别基序（RRM）。本文以Ssp 2KAD/Smk 1反应为模型， 研究MAPKs在发育系统中的自激活。具体 本课题的主要目的是：1-阐明非经典MAPK的分子机制 使用细菌重建系统和纯化蛋白质的信号传导，2-测试a Smk 1激活的基于竞争的开关位点模型，以及3-识别RNA 由Ssp 2中的RNA识别基序识别。

Project Summary/Abstract: Mitogen activated protein kinases (MAPKs) are key signaling enzymes that are activated by phosphorylation of a TXY motif in their activation loops. While dual-specificity MAPK kinases activate many MAPKs (canonical signaling), atypical kinases and autophosphorylation can also activate MAPKs (non-canonical signaling). A great deal is known about the role of canonical signaling pathways in health and disease. Much less is known about non-canonical signaling. Smk1 is a meiosis- specific MAPK in the yeast S. cerevisiae that controls gamete formation (sporulation) through a non-canonical signaling pathway that generates different forms of the MAPK at different stages of meiosis. First, the CDK activating kinase, Cak1, phosphorylates Smk1's activating T-residue as the meiotic divisions are taking place. This monophosphorylated form of Smk1 is distributed throughout the cell. Later in the program (at anaphase II), a meiosis-specific protein, Ssp2, binds to Smk1 and activates the cis-autophosphorylation of its Y-residue. This reaction occurs at specific membraneous structures that cellularize the haploids generated in this specialized cell division. Thus, Ssp2 delivers a pulse of the doubly phosphorylated MAPK to the “right place” at the “right time” in this developmental program. This spatiotemporal specificity is achieved by modularity of the Ssp2 protein; it is localized by a targeting domain (TD) and it activates cis-autophosphorylation of the MAPK via a kinase activating domain (KAD). The Ssp2KAD is itself composed of segments that bind Smk1 and a regulatory RNA recognition motif (RRM). This proposal is to use the Ssp2KAD/Smk1 reaction as a model to study autoactivation of MAPKs in the context of a developmental system. The specific aims of this proposal are: 1- Elucidate molecular mechanisms of non-canonical MAPK signaling using a bacterial reconstitution system and purified proteins, 2-Test a competition-based switch-site model for Smk1 activation, and 3- Identify the RNA(s) recognized by the RNA recognition motif in Ssp2.