Regulation of JNK Signaling in Epidermal Morphogenesis

描述（由申请人提供）：细胞的命运取决于它们对环境的感知和适当反应的能力。Jun Kinase （JNK）信号转导通路在多种发育和环境信号的作用下被激活，以控制细胞的基本行为，如增殖、分化、形态发生和凋亡，但调控对特定信号的适当反应的机制尚不清楚。人类JNK信号的不适当激活可导致多种疾病，包括慢性炎症、癌症和代谢性疾病，而在发育早期JNK信号的丢失会导致小鼠出生缺陷。本提案的总体目标是了解JNK信号是如何被调节以在动物发育和体内平衡中产生适当的反应。调节适当响应的一种方法是使用不同信号下游的信号换能器的独特组合。在果蝇的某些JNK依赖过程中选择性激活的候选换能器是由滑靴（slpr）位点编码的混合谱系激酶（MLK）。SLPR/MLK是组织形态发生必不可少的特异性调节因子，在JNK激酶（JNKKK）水平上起作用，刺激JNK依赖性组织重组。为了研究SLPR/MLK调控JNK信号和组织的分子机制，我们提出了以下具体目标：(1)通过SLPR突变动物的表型分析，结合突变、缺失和嵌合JNKKK转基因的表达，表征SLPR的基本功能域。(2)通过基因筛选修饰SLPR功能缺失相关缺陷的蛋白，鉴定JNK信号通路的修饰因子。(3)通过体外结合实验和体内遗传分析，确定MSN激酶和PVR通路在SLPR形态发生过程中选择性激活的作用。目的是阐明发育系统中对MLK的需求，MLK对JNK信号传导的调节，以及MLK蛋白复合物对特定JNK信号输出的选择性募集。这些研究可能最终提示一种分子机制来操纵JNK信号治疗。

DESCRIPTION (provided by applicant): The fate of cells depends on their ability to sense and respond appropriately to their environment. The Jun Kinase (JNK) signal transduction pathway is activated in response to a wide variety of developmental and environmental signals to control fundamental cell behaviors, such as proliferation, differentiation, morphogenesis, and apoptosis, but the mechanisms that regulate the appropriate response to particular signals are poorly understood. Inappropriate activation of JNK signaling in humans can result in numerous disorders including chronic inflammation, cancer, and metabolic disease, while loss of JNK signaling early in development results in birth defects in mice. The overall objective of this proposal is to understand how JNK signaling is regulated to generate the appropriate responses in animal development and homeostasis. One way to regulate the appropriate response is to use unique combinations of signal transducers downstream from different signals. A candidate transducer that is selectively activated in certain JNK dependent processes in Drosophila is the Mixed Lineage Kinase (MLK), encoded by the slipper (slpr) locus. SLPR/MLK is an essential and specific regulator of tissue morphogenesis, which functions at the level of JNK Kinase Kinase (JNKKK) to stimulate JNK-dependent tissue reorganization. To investigate the molecular mechanisms by which SLPR/MLK regulates JNK signaling and tissue organization, we propose the following specific aims: (1) Characterization of essential functional domains of SLPR using phenotypic analysis of slpr mutant animals, coupled with expression of mutant, deleted, and chimeric JNKKK transgenes. (2) Identification of modifiers of JNK signaling by genetic screening for proteins that modify the defects associated with loss of SLPR function. (3) Determine the role of MSN Kinase and the PVR pathway in selective activation of SLPR during morphogenesis by in vitro binding assays and in vivo genetic analysis. The aims are designed to elucidate the requirement for MLK in a developmental system, the regulation of JNK signaling by MLK, and the selective recruitment of MLK protein complexes for specific JNK signaling outputs. These studies may ultimately suggest a molecular mechanism to manipulate JNK signaling therapeutically.