FUNCTION AND REGULATION OF FATTY ACID BINDING PROTEINS

长链脂肪酸通过细胞质的运输和 它们随后的高效利用用于能源生产和 甘油脂合成可能由14-15 kDa的不同家族促进 细胞质脂肪酸结合蛋白(FABP)。中美之间的差异 几个化合物的结构、组织表达和配体结合特性 FABP基因产物也表明它们是功能专门化的， 但这些蛋白质在脂肪酸运输和运输中的确切作用 新陈代谢仍然知之甚少。通过它们与脂肪酸的结合 并促进它们的细胞质扩散和代谢利用 FABP还可以保护细胞免受高浓度游离脂肪的影响 酸。为了与这种作用保持一致，肝脏FABP的基因转录(L- FABP)是与线粒体外脂肪酶协同诱导的 外源生物的酸氧化途径(包括低脂性过氧化物体 增殖因子)抑制线粒体的β-氧化，并通过脂肪 在细胞脂肪酸条件下积累的酰基代谢物 超载。线粒体外酶的诱导机制 过氧化体和内质网中的脂肪酸氧化途径 涉及一种核受体的激活，即过氧化物酶体增殖物 通过L-FABP主要结合的配体激活受体。L- 因此，FABP可能通过脂肪酰基代谢产物来调节PPAR的激活 从而在细胞的维持中发挥重要作用 以过度分娩为特征的疾病状态的动态平衡 或损害细胞对长链脂肪酸的利用，例如， 饥饿、糖尿病、酒精性肝病、雷氏综合征和先天 线粒体β-氧化的错误。这项建议的目的如下： 他们的主要目标是：1)阐明FABP在脂肪中的功能 酸的运输和代谢；2)对酸运输和代谢关系的理解 L-FABP的功能、表达及其对PPAR功能的调节 调节基因调节，并将：(A)通过选择性地 粘附素结合蛋白在非洲爪哇卵母细胞中的过表达及L结合蛋白的作用 以及它的结构同系物在细胞内的比较功能 长链脂肪的运输、氧化、酯化和合成 酸；(B)测定L-FABP(和L-FABP反义)的作用 L-FABP配体激活PPAR在哺乳动物细胞系中的表达 表达报告基因转染法；(B)确定区域 L-FABP、过氧化物酶和PPAR在肝脏中的表达模式 小叶通过原位杂交，和(C)建立了分子基础 定位L-FABP基因中的PPAR反应元件诱导L-FABP 利用构建的启动子-报告基因构建的5‘启动子区域 转化为原代肝细胞。通过使用这些方法， 拟议的研究将提供有关 胞质FABP的功能知之甚少 构成细胞对疾病状态适应性反应的机制 以增加脂肪酸流量和积累为特征的。

The transport of long-chain fatty acids through the cell cytoplasm and their subsequent efficient utilization for energy production and glycerolipid synthesis may be facilitated by a diverse family of 14-15 kDa cytoplasmic fatty acid binding proteins (FABP). Differences in the structure, tissue expression and ligand-binding properties of the several FABP gene products also suggest that they are functionally specialized, but the exact role of these proteins in fatty acid transport and metabolism remains poorly understood. Through their binding of fatty acids and promoting their cytoplasmic diffusion and metabolic utilization, the FABP may also protect the cell from high concentrations of unbound fatty acids. In keeping with such a role, gene transcription of liver FABP (L- FABP) is induced in concert with enzymes of the extramitochondrial fatty acid oxidation pathways by xenobiotics (including hypolipidemic peroxisome proliferators) that inhibit mitochondrial beta-oxidation, and by fatty acyl metabolites that accumulate under conditions of cellular fatty acid overload. The mechanism of induction of enzymes of the extramitochondrial fatty acid oxidation pathways in peroxisomes and endoplasmic reticulum involves the activation of a nuclear receptor, the peroxisome proliferator activated receptor (PPAR) by ligands which are largely bound by L-FABP. L- FABP may thus modulate the activation of PPAR by fatty acyl metabolites and thereby play an important role in the maintenance of cellular homeostasis in disease states characterized by either excessive delivery or impaired cellular utilization of long-chain fatty acids, e.g., starvation, diabetes, alcoholic liver disease, Reye's Syndrome and inborn errors of mitochondrial beta-oxidation. The aims of this proposal have, as their broad goals: 1) the elucidation of the function of the FABP in fatty acid transport and metabolism and 2) the understanding of the relationship of L-FABP function, expression and regulation to the function of PPAR- mediate gene regulation, and are to: (a) determine, through the selective overexpression of FABP in Xenopus laevis oocytes, the function of L-FABP and the comparative function of its structural congeners in the cellular transport, oxidation, esterification and synthesis of long-chain fatty acids; (b) determine the effect of L-FABP (and L-FABP antisense) expression in mammalian cell lines on PPAR activation by L-FABP ligands in expression-reporter gene transfection assays; (b)determine the regional patterns of L-FABP, peroxisomal enzyme and PPAR expression in the liver lobule by in situ hybridization, and (c) establish the molecular basis for L-FABP induction by localizing PPAR response elements in the L-FABP gene 5' promoter region using promoter-reporter gene constructs transfected into primary hepatocytes. Through the use of these approaches, the proposed studies will provide important new information regarding the poorly understood function of the cytosolic FABP, and the molecular mechanisms that underlie the cellular adaptive response to disease states characterized by increased fatty acid flux and accumulation.