Defining signal selection from the free fatty acid receptor FFA4; implications for physiological functions

G蛋白偶联受体（GPCR）是主要位于细胞表面的蛋白质大家族，其充当身体细胞和组织的外部环境变化的传感器。虽然GPCR家族的成员已经是最成功的一类药物靶点，但其中相对较少的成员尚未以这种方式靶向。我们认为这是由于缺乏对许多GPCR的基础生物学的理解，以及缺乏药理学工具化合物和适当的动物模型来测试它们在正常生理学和疾病背景下的体内功能。虽然传统上被认为是设计用于检测和指导细胞对各种激素和神经递质浓度的变化做出反应，但最近已经清楚的是，大量的GPCR被设计用于直接对食物消化产生的代谢物的变化做出反应，并且这样做，它们提醒身体器官协调对营养缺乏或过剩的反应。鉴于目前正在上升到流行比例的许多疾病，例如糖尿病和肥胖症，是从摄入明显过量的高热量食物和缺乏锻炼的“西方生活方式”发展而来的，那么模仿或阻断GPCR对这些代谢产物的影响可能具有有益的效果。事实上，对于我们计划详细研究的受体，称为游离脂肪酸受体4（FFA 4），了解其激活时调节血糖水平的能力，并增加激素胰岛素的有效性，已经导致制药行业正在努力评估FFA 4的激活是否可能是治疗II型糖尿病的新方法。FFA 4由体内多种类型的细胞表达，这表明激活或阻断这种受体也可能对其他疾病有益。很明显，FFA 4可以通过控制许多不同的信号通路来指示细胞做出反应，在拟议的研究中，我们计划解开这种复杂性，并了解哪些信号在不同类型的细胞和组织中占主导地位，以及这如何决定激活FFA 4的结果。我们将以多种方式做到这一点。其中最令人兴奋和重要的将是利用小鼠的细胞和组织，在我们目前对BBSRC资助的这种受体的研究中，我们已经通过基因工程表达了一种只能与所谓的G蛋白相互作用而不能与抑制蛋白相互作用的FFA 4。抑制蛋白是一组关键的信号蛋白，与激活的FFA 4强烈相互作用。比较正常和抑制蛋白相互作用缺陷小鼠细胞和组织中FFA 4功能的研究将提供这一信息，这将在不同类型的脂肪细胞和免疫系统细胞的组织中进行检查。之所以选择这些，是因为FFA 4被认为在脂肪细胞发育和炎症等领域发挥作用，以及如何对用于缩小化疗中癌症的药物产生耐药性。与这些大的总体目标同时，我们还计划开发和利用阻止FFA 4行动的化学品，这些化学品比目前可用的化学品有很大改进，详细绘制FFA 4的表达模式，并使用我们从目前BBSRC资助中开发的细胞，这些细胞已经被“基因组-编辑“以消除信号传导途径的特定子集，以使我们能够评估激活FFA 4的不同类型的分子是否可以选择性地控制FFA 4的信号传导潜力。FFA 4。到拟议的研究结束时，FFA 4将不再是一个研究不足的GPCR，我们将能够有信心地说，如果调节这种受体可能是治疗糖尿病以外的“西方生活方式”疾病的一种手段。

G protein-coupled receptors (GPCRs) are a large family of proteins, located predominantly at the surface of cells, that act as sensors of changes in the external environment of cells and tissues of the body. Although members of the GPCR family are already the most successful class of drug targets, relatively few of them have yet been targeted in this way. We believe this is due to a lack of understanding of the basic underpinning biology of many GPCRs, and a paucity of pharmacological tool compounds and appropriate animal models to test their in vivo function in both normal physiology and in the context of disease. Although traditionally viewed as being designed to detect and instruct cells to respond to alterations in the concentration of various hormones and neurotransmitters, in recent times it has become clear that a substantial number of GPCRs are designed to respond directly to alterations in metabolites that are produced by digestion of foodstuffs and, in so doing, they alert organs of the body to co-ordinate responses to either a dearth or a surplus of nutrients. Given that many diseases that are currently rising to epidemic proportions, e.g. diabetes and obesity, develop from a 'Western lifestyle' of intake of a marked excess of highly calorific foods and a lack of exercise, then mimicking or blocking the effects of the GPCRs for such metabolic products may have beneficial effects. Indeed, for the receptor we plan to study in detail, which is called free fatty acid receptor 4 (FFA4), understanding of its ability when activated to regulate blood glucose levels, and to increase the effectiveness of the hormone insulin, has resulted in ongoing efforts by the pharmaceutical industry to assess if activation of FFA4 might be a novel approach to treat type II diabetes.Like many other GPCRs, FFA4 is expressed by range of types of cells in the body, leading to suggestions that either activating or blocking this receptor might also have benefits in other conditions. It is clear that FFA4 can instruct cells to respond by controlling a number of different signalling pathways and in the proposed studies we plan to unravel this complexity and to understand which signals are predominant in different types of cells and tissues and how this determines the outcome of activating FFA4. We will do this in a number of ways. One of the most exciting and important will be to utilise cells and tissues from mice, that in our current studies on this receptor that BBSRC have funded, we have genetically engineered to express a form of FFA4 that can only interact with so called G proteins and not with arrestins. Arrestins are a key set of signalling proteins that interact strongly with activated FFA4. Studies that compare functions of FFA4 in cells and tissues from normal and arrestin-interaction deficient mice will provide this information, and this will be examined in tissues that range from different types of fat cells, to cells of the immune system. These have been selected because of the roles FFA4 has been suggested to play in areas that range from fat cell development and inflammation, to how resistance develops to drugs that are used to shrink cancers in chemotherapy. In parallel with these large, overarching objectives we also plan to develop and utilise chemicals that block the actions of FFA4 that are much improved on those currently available, map in detail the expression pattern of FFA4 and employ cells we have developed from current BBSRC funding that have been 'genome-edited' to eliminate specific subsets of signalling pathways to allow us to assess if different types of molecule that activate FFA4 can selectively control the signalling potential of FFA4. By the end of the proposed studies FFA4 will no longer be a poorly studied GPCR and we will be in position to state with some confidence if regulating this receptor might be a means to treat 'Western lifestyle' diseases beyond diabetes.