LIPID AND LIPOPROTEIN METABOLISM IN INSECTS

这项研究的长期目标是确定基本机制 参与昆虫的脂肪运输和储存；发现哪一种 这些机制是昆虫特有的，可能成为 对昆虫的生物控制；并确定这些机制中的哪一种 可作为了解脊椎动物体内脂质运输的模型。 而脊椎动物依赖于一组脂蛋白来影响脂肪 在运输方面，昆虫主要使用一种单一类型的脂蛋白，脂蛋白， 用于脂类运输。脂蛋白比脊椎动物更多才多艺 脂蛋白在其运输的不同脂类方面以及更多 比脊椎动物脂蛋白更有效的是，在很大程度上，它 将脂类输送到组织中，而不是自身内化和 被毁了。脂蛋白可以在其核心携带多种脂类，其中 甘油二酯(DG)是主要成分。脂蛋白是在脂肪中生成的 身体作为一种新生的脂蛋白，含有载脂蛋白和 磷脂，但不含DG或其他转运脂。DG的获取自 中肠和运输到脂肪体储存。货物的运输 从中肠到脂肪体的DG是由两个脂蛋白受体介导的：一个是 与DG贫脂蛋白特异结合的中肠 促进DG从中肠到脂蛋白的移动，以及在中肠中的另一种 脂肪身体，它与富含DG的脂蛋白特异性结合， 促进DG从脂蛋白到脂肪体的运动。具体目标1是 旨在提纯和鉴定这些受体。在飞来的途中 成虫来自许多物种，脂肪体内储存的三酰甘油 转化为DG，离开脂肪身体并被脂蛋白摄取 在血淋巴中，然后被输送到飞行肌肉，在那里 DG被转化为脂肪酸，脂肪酸被氧化提供能量 飞行所需的。脂蛋白对DG的摄取依赖于 可溶性载脂蛋白apolipophorin-III(ApoLpIII) 在血淋巴中游离。ApoLp-III与脂蛋白结合，并极大地 增加其运载DG的能力。最近，apoLp-的X射线结构- III已确定。具体目标2旨在研究这一机制。 ApoLp-III与脂蛋白表面结合。另一个标志是 脂蛋白新陈代谢是指它将特定的脂类输送到 特定的组织。鉴于脂红素携带着一种复杂的 脂类，如何选择性地将特定的脂类输送到特定的 组织出现了吗？需要检验的假设是，组织特异性 脂类输送需要两种成分：1)特定的脂类结合 组织细胞内的蛋白质和2)非内化 组织细胞表面的脂蛋白受体。特定的 AIM 3旨在通过研究类胡萝卜素运输来检验这一假说 在家蚕中，几个突变体在类胡萝卜素的运输 系统已经存在。

The long-term goals of this research are to determine the basic mechanisms involved in lipid transport and storage in insects; to discover which of these mechanisms are specific to insects and might be targets for biorational control of insects; and to ascertain which of these mechanisms can be used as models for understanding lipid transport in vertebrates. Whereas vertebrates rely on a battery of lipoproteins to effect lipid transport, insects use primarily a single type of lipoprotein, LIPOPHORIN, for lipid transport. Lipophorin is both more versatile than vertebrate lipoproteins in terms of the diverse lipids it transports and more efficient than vertebrate lipoproteins in that, for the most part, it delivers lipids to tissues without itself being internalized and destroyed. Lipophorin can carry a variety of lipids in its core, of which diacylglycerol (DG) is the major component. Lipophorin is made in the fat body as a nascent lipoprotein which contains apolipoproteins and phospholipid, but no DG or other transported lipids. DG is acquired from the midgut and transported to the fat body for storage. The transport of DG from midgut to fat body is mediated by two lipophorin receptors: one in the midgut which specifically binds DG-poor lipophorin and which facilitates movement of DG from midgut to lipophorin, and another in the fat body, which specifically binds DG-rich lipophorin and which facilitates movement of DG from lipophorin to fat body. Specific Aim 1 is designed to purify and characterize these receptors. During flight in adult insects from many species, fat body triacylglycerol stores are converted to DG, which leaves the fat body and is taken up by lipophorin in the hemolymph, and then is transported to the flight muscle, where the DG is converted to fatty acids which are oxidized to provide the energy required for flight. The uptake of DG by lipophorin is dependent on a soluble apolipoprotein, apolipophorin-III (apoLpIII), which is present free in the hemolymph. ApoLp-III binds to lipophorin and greatly increases it capacity to carry DG. Recently, the x-ray structure of apoLp- III has been determined. Specific Aim 2 is designed to study the mechanism whereby apoLp-III binds to lipoprotein surfaces. Another hallmark of lipophorin metabolism is its ability to deliver specific lipids to specific tissues. Given that lipophorin carries a complex mixture of lipids, how does selective delivery of a specific lipid to a specific tissue occur? The hypothesis to be tested is that the tissue specificity of lipid delivery requires two components: 1) a specific lipid-binding protein within the cells of the tissue and 2) a non-internalizing lipoprotein receptor on the surface of the cells of the tissue. Specific Aim 3 is designed to test this hypothesis by studying carotenoid transport in Bombyx mori, in which several mutants in the carotenoid transport system exist.