Fatty acid transport and its regulation

我们克隆并鉴定了五种哺乳动物脂肪酸转运蛋白(FATPs)。FATP1在心脏、脂肪细胞、肌肉和脑中高水平表达。FATP4主要表达在可吸收的小而密集的上皮细胞的刷状缘，是摄取LCFAs所必需的。人类FATP6仅在心肌中表达，在肥大组织中表达水平升高。我们的总体目标是了解脂肪酸转运的分子机制及其调控。我们关注FATPs以及其他与脂肪酸运输有关的蛋白质：“清道夫”受体CD36和SRI-BI；LACS(长链脂肪酰辅酶A合成酶)；以及细胞质FABP(脂肪酸结合蛋白)，以及它们在心脏、脂肪细胞和肠道上皮细胞脂肪酸运输中的作用。我们的具体目标是1)确定这些蛋白质是否在功能上协同作用，促进培养细胞对低分子脂肪酸的运输，以及脂肪酸是否在进入时被酯化为辅酶A，这取决于涉及的运输机制。2)确定各种FATP、FABP、SR-BI/CD36、LACS之间是否存在稳定的物理交互。3)通过反义实验确定在没有和存在胰岛素的情况下，哪种蛋白质对脂肪细胞摄取LCFA具有限速作用。4)确定胰岛素如何刺激脂肪细胞摄取LCFA，以及肿瘤坏死因子-α如何抑制脂肪细胞摄取LCFA。5)克隆并研究心脏特异的人类FATP6的嘌呤同源物。6)根据获得的结果，使用表达模型系统测试FATP1、FATP4和其他蛋白质在LCFA摄取中的作用，并确定这些蛋白质在整个小鼠脂肪代谢中的作用。因此，我们将1)确定这些候选脂肪酸转运蛋白在发育中和成年小鼠心脏中的表达模式。2)利用FATP1基因敲除小鼠和转基因FATP1过表达小鼠，研究FATP1在LCFA、脂肪组织、心脏和横纹肌的摄取和脂质代谢中的作用。3)利用基因敲除小鼠，确定FAT4、SR-BI和CD36在吸收上皮细胞从小肠摄取LCFAs中的作用。

We have cloned and characterized five mammalian fatty acid transport proteins (FATPs). FATP1 is expressed at high levels in heart, adipocytes, muscle, and brain. FATP4 is expressed predominantly in the brush border of the absorptive small intensive epithelial cells and is essential for uptake of LCFAs. Human FATP6 is expressed exclusively in heart muscle and its level is elevated in hypertrophic tissue. Our overall goal is to understand the molecular mechanism of fatty acid transport and its regulation. We focus on the FATPs as well as other proteins implicated in fatty acid transport: the "scavenger" receptors CD36 and SRI-BI; LACS (long chain fatty acyl CoA synthetase); and cytosolic FABPs (fatty acid binding proteins), and their roles in fatty acid transport in heart, adipocytes, and intestinal epithelial cells. Our specific aims are to 1) Determine whether these proteins functional synergize to enhance the transports of LCFAs by cultured cells and whether, depending on the transport mechanism involved, fatty acids are esterified to CoA upon entry. 2) Determine whether stable physical interactions occur between various FATPs, FABPs, SR-BI/CD36, and LACS. 3) Determine by antisense experiments which protein is rate-limiting for adipocyte LCFA uptake, both in the absence and presence of insulin. 4) Determine how insulin stimulates and TNF-alpha inhibits LCFA uptake by adipocytes 5) Clone and study the putative purine homologue of the cardiac-specific human FATP6. 6) Depending on the results obtained, use expression model systems to test the roles of FATP1, FATP4, and other proteins in LCFA uptake and determine the role of these proteins in whole-mouse lipid metabolism. Thus we will 1) Determine the expression pattern of these candidate fatty acid transport proteins within the developing and adult murine heart. 2) Using both FATP1 knockout and transgenic FATP1 over-expressing mice, determine the role of FATP1 in LCFA, uptake and lipid metabolism by adipose tissue and heart and striated muscle. 3) Using gene knock-out mice, determine the role of FAT4, SR- BI, and CD36 in uptake of LCFAs from the small intestine by the absorptive epithelial cells.