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以细分为三个步骤：细胞跨膜摄取，辅酶A酯化激活，以及随后的代谢。酰辅酶A合成酶激活细胞内代谢的脂肪酸，但也参与摄取。脂肪酸的主要途径是储存、膜生物合成和能量转化。在分子水平上，活化的脂肪酸是如何被引导到一条特定的代谢途径上的还不是很清楚。我们以前发现，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的观点是一致的，但它们在亚细胞中的定位不同。值得注意的是，脂肪酸最初的亚细胞定位取决于所表达的酰基辅酶A合成酶的类型和定位。根据我们的发现得出的假说暗示，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。主要的实验战略旨在为这一想法提供坚实的证据。模型系统是组织培养细胞，表达不同的酰辅酶A合成酶，或者表达相同的酰基辅酶A合成酶，定位于不同的亚细胞室。生理脂肪酸和荧光脂肪酸的代谢和运输将通过薄层层析、亚细胞分离和显微镜进行分析。参与脂肪酸摄取和代谢的蛋白质是治疗肥胖症和相关疾病的重要药物靶点。只有对这些分子的基础研究才能使新的治疗策略成为可能。

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.