Intracellular channeling of fatty acids by acyl-CoA synthetases

从概念上讲，长链脂肪酸在细胞内的利用可细分为三个步骤：跨质膜的细胞摄取，通过辅酶A的酯化活化，以及随后的代谢。酰基辅酶a合成酶激活脂肪酸进行细胞内代谢，但也参与摄取。脂肪酸的主要途径是储存、膜生物合成和转化为能量。活化脂肪酸是如何被引导到一个特定的代谢途径的，在分子水平上还没有得到很好的理解。我们之前的研究表明，定位于内质网或线粒体的酰基辅酶a合成酶可以调节脂肪酸摄取的程度。最近的数据与多种不同的长链酰基辅酶a合成酶在同一细胞类型中同时表达，但其亚细胞定位不同的观点一致。引人注目的是，脂肪酸最初的亚细胞定位依赖于被表达的酰基辅酶a合成酶的类型和定位。从我们的发现中得出的假设表明酰基辅酶a合成酶活性的空间组织是引导脂肪酸走向特定代谢命运的关键因素。主要的实验策略旨在为这一观点提供确凿的证据。模型系统是组织培养细胞，表达不同的酰基辅酶a合成酶或相同的酰基辅酶a合成酶，被工程定位于不同的亚细胞区室。生理和荧光脂肪酸的代谢和运输将通过薄层色谱，亚细胞分离和显微镜分析。参与脂肪酸摄取和代谢的蛋白质是治疗肥胖和相关疾病的重要药物靶点。只有对这些分子进行基础研究，才能产生新的治疗策略。

Conceptionally, the intracellular utilization of long chain fatty acids can be subdivided into three steps: Cellular uptake across the plasma membrane, activation by esterification with coenzyme A, and subsequent metabolism. Acyl-CoA synthetases activate fatty acids for intracellular metabolism but are also involved in uptake. The predominant pathways for fatty acids are storage, membrane biosynthesis and conversion to energy. How activated fatty acids are channeled towards one particular metabolic pathway is not well understood on the molecular level. We previously showed that acyl-CoA synthetases localized to either the ER or to mitochondria can regulate the extent of fatty acid uptake. Recent data are consistent with the idea that multiple different long chain acyl-CoA synthetases are expressed simultaneously at the same time in the same cell type but differ in their subcellular localization. Strikingly, the initial subcellular localization of fatty acids taken up is dependent on the type and localization of the acyl-CoA synthetase being expressed. The hypothesis derived from our findings implies that the spatial organization of acyl-CoA synthetase activity is a key factor in channeling fatty acids towards a particular metabolic fate. The major experimental strategy aims at providing solid evidence for this idea. The model systems are tissue culture cells expressing either different acyl-CoA synthetases or the same acyl-CoA synthetase engineered to be localized to different subcellular compartments. The metabolism and trafficking of both physiological and fluorescent fatty acids will be analyzed by thin layer chromatography, subcellular fractionation and microscopy. Proteins involved in fatty acid uptake and metabolism are important pharmaceutical targets for the treatment of adipositas and associated diseases. Only basic research on these molecules will enable new strategies for therapy.