Defining the role of ERK5 kinase and ERK5 transcriptional activities in cell migration and EMT using novel ERK5 inhibitors

我们体内的细胞不断受到环境变化的影响，它们包含一个广泛的信号通路网络，协调适当的反应。在发育中的胚胎中，细胞可能会收到刺激或指示它们分裂的信号（所谓的生长因子），也可能会收到指示它们停止分裂并进行“分化”的信号，在这个过程中，细胞获得了构成我们成人身体中离散组织的特殊细胞类型的特征，如神经、免疫系统中的血细胞或我们的皮肤。这种细胞分裂和分化的过程在成人的某些组织中继续进行；不断自我更新，比如我们的皮肤。细胞要对生长或分化信号作出反应，必须激活关键的生长或分化蛋白；这通常涉及到增加这些蛋白质的丰度。这些蛋白质的遗传信息储存在离散的DNA片段（基因）中，这些DNA片段位于细胞核中的染色体上。当细胞接收到生长信号时，这些基因被“转录因子”“读取”，转录因子是一种与DNA结合的分离蛋白质，将DNA信息转录成信使RNA （mRNA）分子，而信使RNA分子又被“翻译”成相关的蛋白质。这种转录和翻译的耦合过程被称为“基因表达”。这整个复杂的过程是由控制每一步的信号通路精心策划的。控制是这里的关键词。例如，如果细胞分裂过多或不能正确分化，它们可能会癌变。控制细胞分裂和分化的信号通路通常涉及被称为蛋白激酶的酶级联反应。这些酶用磷酸基团“标记”其他蛋白质（这一过程被称为磷酸化），这改变了蛋白质的活性、丰度或定位。标记的蛋白质被称为蛋白激酶的“底物”。该项目涉及一种名为ERK5的蛋白激酶。1. 人们对寻找阻断ERK5活性的药物（ERK5抑制剂或ERK5i）很感兴趣，因为它们可能有助于治疗炎症、心血管疾病或癌症。事实上，我们一直在与一组科学家合作，以确定抑制ERK5激酶活性的新ERK5i。然而，令我们惊讶的是，它们实际上促进了基因读取或转录。ERK5蛋白的不寻常之处在于它有两个完全不同的功能区域或结构域。第一个是激酶结构域，它使底物磷酸化；第二个是转录因子结构域，它与DNA结合以读取基因。我们的研究结果表明，当ERK5i抑制激酶结构域时，它会引起激活转录因子结构域的结构变化。所以一个目标是在分子水平上理解这是如何发生的以及这对于设计ERK5抑制剂是好事还是坏事。其次，我们想要确定ERK5结合的基因，这样我们就可以更好地理解ERK5在基因表达中的作用，特别是ERK5的两个功能域。3. 我们最近的实验表明，ERK5活性在调节被称为上皮-间质转化（EMT）的分化过程中很重要。EMT在胚胎发育、伤口修复以及癌细胞在身体周围扩散并侵入新部位（这一过程称为转移）的过程中都很重要。事实上，我们已经发现阻断ERK5活性可以逆转EMT并阻止细胞的运动。所以这个项目的最终目的是了解ERK5如何控制这个EMT过程，以及它是由ERK5的激酶结构域还是基因读取结构域控制的。这项研究应该告诉我们更多关于ERK5的正常作用和调控。ERK5在临床条件（炎症、心血管疾病、癌症）中也可能很重要，因此我们的研究结果可能会产生更广泛的影响，我们将与这些领域的科学家合作来推进这一进展。

The cells in our body are constantly subjected to changes in their environment and they contain an extensive network of signalling pathways that coordinate appropriate responses. In the developing embryo, cells may receive stimuli or cues telling them to divide (so called growth factors) or they may receive cues telling them to cease dividing and undergo 'differentiation', a process in which cells acquire the characteristics of specialized cell types that make up the discrete tissues in our adult bodies such as nerves, blood cells in the immune system or our skin. This process of cell division and differentiation continues in adults in certain tissues; which constantly renew themselves such as our skin. For cells to respond to growth or differentiation cues they must activate key growth or differentiation proteins; this often involves increasing the abundance of these proteins. The genetic information for these proteins is stored in discrete pieces of DNA (genes), which reside on chromosomes in the nucleus. When a cell receives a growth signal these genes are 'read' by 'transcription factors', discrete proteins that bind to DNA and transcribe the DNA information the into messenger RNA (mRNA) molecules, which are in turn 'translated' into the relevant proteins. This coupled process of transcription and translation is called 'gene expression'.This whole complex process is orchestrated by signalling pathways, which control every step. Control is the key word here. For example, if the cells divide too much or fail to differentiate correctly they may become cancerous. The signalling pathways controlling cell division and differentiation typically involve cascades of enzymes called protein kinases. These enzymes 'tag' other proteins with a phosphate group (a process called phosphorylation) and this changes the activity, abundance or localisation of the protein. The tagged protein is referred to as the 'substrate' of the protein kinase enzyme. This project concerns a protein kinase called ERK5. 1. There is much interest in finding drugs that block ERK5 activity (ERK5 inhibitors or ERK5i) as they may help to treat inflammation, cardiovascular disease or cancer. Indeed, we have been working with a team of scientists to identify new ERK5i that inhibit ERK5 kinase activity. However, to our surprise they actually promote gene reading or transcription. The ERK5 protein is unusual in that it has two quite different functional regions or domains. The first is the kinase domain, which phosphorylates substrates; the second is a transcription factor domain, which binds DNA to read genes. Our results suggest that when an ERK5i inhibits the kinase domain it causes structural changes that activate the transcription factor domain. So one aim is to understand at the molecular level how this happens and whether this is a good thing or a bad thing for designing ERK5 inhibitors.2. Second, we want to identify the genes that ERK5 binds to so we can better understand the role of ERK5 - and specifically the two functional domains of ERK5 - in gene expression. 3. Our recent experiments have suggested that ERK5 activity is important in regulating a differentiation process called epithelial-to-mesenchymal transition (or EMT). EMT is important during development of the embryo, during wound repair and for cancer cells to spread around the body and invade new sites - a process called metastases. Indeed, we have found that blocking ERK5 activity reverses EMT and prevents the movement of cells. So a final aim of this project is to understand how ERK5 controls this EMT process and whether it is controlled by the kinase domain or the gene reading domain of ERK5.This study should tell us more about the normal role and regulation of ERK5. ERK5 may also be important in clinical conditions (inflammation, cardiovascular disease, cancer) so our results may have wider impacts and we will work with scientists in these areas to progress this.