Cellular and molecular mechanisms of epithelial ion transport and excretion in invertebrates

所有陆生动物都能调节细胞和体液中的离子浓度。此外，他们还必须清除体内的废物和毒素。本研究探讨了昆虫和线虫体内的运输上皮如何排泄毒素并调节水、离子、酸和碱的水平。我们的一些上皮运输实验使用了模式生物，如果蝇和线虫，因为这些研究提供了与理解其他生物（包括人类）的相关过程相关的信息。上皮是在两个隔室之间形成屏障的细胞层，并在一个充满液体的隔室（通常是外部）和第二个内隔室之间运输无机盐（钠、氯化物等）和水等物质。外部隔室中的液体的例子包括流经水生物种鳃的水、消化道的内容物以及排泄系统中包含的尿液或血液滤液。内部隔室中的液体包括血液和细胞外液体，它们将营养物质运送到肠道和排泄系统。分泌或重吸收离子、营养物质、废物、毒素或水分的上皮细胞的活动可由释放到循环系统中的激素控制。这些激素与细胞膜上的受体结合并激活细胞内第二信使系统。这种细胞信号的级联反应通常会导致运输特定离子的膜蛋白的激活。研究昆虫和线虫的上皮转运机制和控制有三个好处：1)了解昆虫害虫种类中上皮转运的细胞机制和激素控制，有助于合理设计新的环保控制措施。例如，了解上皮细胞排泄有毒物质的机制有助于开发阻止害虫排泄的化合物。2)了解上皮细胞的转运机制对于理解昆虫和线虫如何适应不同的环境，以及自然或人为变化（如环境污染）如何对这些动物和其他动物产生有害影响至关重要。3)昆虫和线虫的上皮组织为理解细胞排泄和离子运输机制提供了有用的模型系统。利用基因特征良好的物种，如果蝇和线虫，使我们能够检查控制特定膜转运蛋白表达的基因突变或敲除的影响。这些研究帮助我们了解类似基因在包括人类在内的其他动物中的作用，从而有助于理解肠道和肾脏等组织疾病的基础。

All terrestrial animals regulate the concentrations of ions in their cells and body fluids. In addition, they must eliminate wastes and toxins from their bodies. This research examines how transporting epithelia within insects and nematode worms excrete toxins and regulate the levels of water, ions, acids and bases. Some of our experiments on epithelial transport use model organisms, such as fruit flies and the nematode worm C. elegans, because such studies provide information which is relevant to understanding related processes in other organisms, including humans. Epithelia are layers of cells which form a barrier between two compartments, and which transport materials such as inorganic salts (sodium, chloride, etc.) and water between one fluid-filled compartment, often external, and a second internal compartment. Examples of fluids in external compartments include water flowing over the gills of an aquatic species, the contents of the digestive tract, and urine or blood filtrate contained within the excretory system. Examples of fluids in internal compartments include the blood and extracellular fluids which transport nutrients to, or from, the gut and excretory system. The activities of epithelia which secrete or reabsorb ions, nutrients, waste materials, toxins or water from particular compartments can be controlled by hormones released into the circulatory system. The hormones bind to receptors in cell membranes and activate intracellular second messenger systems. This cascade of cell signaling often leads to activation of membrane proteins which transport particular ions. Research into the mechanisms and control of transporting epithelia in insects and nematodes provides three benefits: 1) Knowledge of the cellular mechanisms and hormonal control of transporting epithelia in pest species of insect facilitates rational design of novel and environmentally benign control measures. For example, understanding the mechanisms of excretion of toxic materials by epithelia aids development of compounds which block such excretion in pest insects. 2) Understanding the mechanisms of transporting epithelia is central to understanding how insects and nematodes adapt to different environments, and how natural or man-made changes (e.g. environmental pollution) may have deleterious effects on these and other animals. 3) Epithelial tissues of insects and nematodes provide useful model systems for understanding the cellular mechanisms of excretion and ion transport. The use of genetically well-characterized species, such as fruit flies and nematode worms, allows us to examine the effects of mutations or knockouts of genes controlling the expression of specific membrane transporters. Such studies help us to learn the roles of similar genes in other animals, including humans, and can thus contribute to understanding the basis of diseases in tissues such as the gut and the kidney.