Retinoid Homeostasis

 描述(申请人提供)：从视黄醇(维生素A)生物合成全反式维甲酸(RA)会产生一种金盏花素，它调节细胞命运和分化细胞的功能，包括燃料使用、免疫功能和神经系统功能等。短链脱氢酶/还原酶(SDR)家族的多种视黄醇脱氢酶(RdH)和还原酶(RRD)催化视黄醇转化为视网膜或视网膜转化为视黄醇。在小鼠身上已经敲除了三种基因：脱氢酶Rdh1和Rdh10；还原酶Dhrs3。这三个基因敲除都揭示了维生素A缺乏的表型，分别与肥胖、神经系统发育和功能以及心脏和骨骼发育有关。每种基因在整个胚胎发育和成体中都有广泛的表达。此外，视网膜还原酶Dhrs3和视黄醇脱氢酶Rdh10似乎形成了促进异二聚体。视网膜脱氢酶(Raldh)催化RA生物合成的第二步，不可逆转地将视网膜转化为RA。Raldh1、Raldh2和Raldh3基因敲除的Raldh1、Raldh2和Raldh3具有反映RA缺陷的表型，但每一种都是不同的，分别涉及能量平衡、免疫功能/胚胎发生和发育。这些数据表明，特定的代谢物(酶组合，Rdh/RRD/Raldh)产生离散的RA池，以支持不同的维甲酸功能。这些假定的代谢物的协调调节和功能还没有被研究过。这项研究的长期目标是确定RA生物合成的位置，每个代谢产物的生物学影响，以及调节代谢产物表达的机制。除白色脂肪细胞外，几乎所有的细胞都形成多房性脂滴。LD起细胞器的作用，可产生类金龟子。然而，相对较少的研究集中在这种潜在的LD功能上。在LD生物合成之前，主要的视黄醇酯化酶卵磷脂：视黄醇酰基转移酶(LRAT)和Rdh1一样定位于平滑内质网。细胞内主要的视黄醇结合蛋白Crbp1定位于线粒体或线粒体相关膜(MAM)，Rdh10也是如此。在LD形成过程中，Crpb1、LRAT、Rdh10和Dhrs3，而不是Rdh1，位于LD表面或其附近。LRAT和Rdh10与LD的结合提高了它们的比酶活性。这个项目将检验这样一个假设，即LD在RA中加入了一种用于激活视黄醇的代谢物，该代谢物由精选的酶和维甲酸稳态的结合蛋白组成。其具体目的是：1)从肝细胞中分离出有助于LD类维A酸代谢的酶；2)确定与LD相关的类维A酸代谢酶的亚细胞起源(S)及其与LD相互作用的确切性质；3)确定LD的类维A酸生物合成能力。 身份证。该项目将产生对维甲酸的动态平衡、RA的生物合成以及LD作为金银花来源的功能具有重要意义的数据，并将提供关于维甲酸代谢在与LD相关的疾病(如癌症、炎症和糖尿病)中的作用的见解。

 DESCRIPTION (provided by applicant): Biosynthesis of all-trans-retinoic acid (RA) from retinol (vitamin A) produces an autacoid that regulates cell fate specification and functions of differentiated cells, including fuel use, immune function, and nervous system function, to name a few. Multiple retinol dehydrogenases (Rdh) and reductases (RRD) of the short-chain dehydrogenase/reductase gene (SDR) family catalyze conversion of retinol into retinal or retinal into retinol. Three have been knocked out in mice: the dehydrogenases Rdh1 and Rdh10; the reductase Dhrs3. These three knockouts each reveal a vitamin A-deficiency phenotype, associated with adiposity, nervous system development and function, and cardiac and skeletal development, respectively. Each has widespread expression throughout embryogenesis and in the adult. In addition, the retinal reductase Dhrs3 and the retinol dehydrogenase Rdh10 seem to form a facilitative heterodimer. Retinal dehydrogenases (Raldh) catalyze the second step of RA biosynthesis, irreversible conversion of retinal into RA. Knockouts of Raldh1, Raldh2, and Raldh3, show phenotypes reflecting RA deficiency, but each is distinct, involving energy balance, immune function/embryogenesis, and development, respectively. These data suggest that specific metabolons (enzyme combinations, Rdh/RRD/Raldh) generate discrete RA pools to support distinct retinoid functions. Coordinated regulation and function of these putative metabolons have not been examined. The long-term goals of this research are to determine sites of RA biosynthesis, biological impact of each metabolon, and mechanisms of regulating metabolon expression. Virtually all cells, except white adipocytes, form multilocular lipid droplet (LD). LD function as organelles that may generate autacoids. Relatively little research has focused on this potential LD function, however. Before LD biosynthesis, the major retinol esterifying enzyme, lecithin:retinol acyl transferase (LRAT), localizes in the smooth endoplasmic reticulum, as does Rdh1. The major intracellular retinol binding-protein, Crbp1 localizes with mitochondria or mitochondria associated membranes (MAM), as does Rdh10. During LD formation Crpb1, LRAT, Rdh10 and Dhrs3, but not Rdh1, locate at or near surfaces of LD. Association of LRAT and Rdh10 with LD increases their specific enzyme activity. This project will test the hypothesis that LD incorporate a metabolon for activating retinol into RA, which consists of select enzymes and binding-proteins of retinoid homeostasis. The specific aims are: 1) identify enzymes that contribute to retinoid metabolism in LD isolated from hepatocytes; 2) determine subcellular origin(s) of retinoid-metabolizing enzymes that associate with LD and the precise nature of their interactions with LD; 3) determine the retinoid biosynthesizing capacity of LD. This project will generate data significant to retinoid homeostasis, RA biosynthesis, and the function of LD as sources of autacoids, and will provide insight into the role of retinoid metabolism with respect to LD- associated diseases, such as cancer, inflammation, and diabetes.