Short-Chain Dehydrogenases in Retinol/Sterol Metabolism

维甲酸在多种胎儿和成人的分化和发育中起重要作用 纸巾。维甲酸由视黄醇分两步生成：第一步，视黄醇通过一步转化为视黄醛。 可逆氧化，然后视黄醛不可逆氧化为维甲酸。视黄醇的氧化是 维甲酸生产中的限速步骤，决定了维甲酸生物合成的总体速度 来自视黄醇。在前一个供资期间，我们确定了人类短链的两个子家族 脱氢酶/还原酶(SDRS)是一类对类维甲酸有活性的蛋白质超家族。在表达时 在完整的细胞中，类似RodH的SDR赋予了将视黄醇氧化为视黄醛的能力，而RalR1类似 酶可以将视黄醛还原为视黄醇。基于这些观察，我们 认为这两组人SDR通过调节组织中的维甲酸稳态来促进人体组织中的维甲酸稳态。 视黄醇和视黄醛之间的平衡，从而调节维甲酸的速率 生物合成。为了验证我们的假设，我们建议对人和动物的维甲酸代谢进行表征。 组织在存在和不存在RADH和RalR1样SDR的情况下。在第一次实验中 特定的目的将检验一种假设，即在人类器官型中沉默RodH样SDR基因的表达 皮筏培养导致视黄醇氧化成视黄醛的速率降低，而沉默RalR1- 与SDR一样，基因表达导致视黄醛转化为视黄醇的速率降低。实验 根据第二个具体目标，将补充人体皮肤筏的体外研究与体内研究 RalR1基因敲除小鼠模型，并将检验一种假设，即RalR1对于减少 小鼠组织中的视黄醛转化为视黄醇。因为在体外，RalR1的小鼠同源基因具有很高的活性 对于除了视黄醛之外的中链醛，我们还将测试RalR1是否有助于 中链醛的还原。据报道，维甲酸的动态平衡在 癌症细胞，在酒精性肝病和胎儿酒精综合征中。拟议的研究将提供一个 更好地了解维甲酸代谢失调的分子基础 病态。

Retinoic acid plays an important role in differentiation and development of a wide variety of fetal and adult tissues. Retinoic acid is produced from retinol in two steps: first, retinol is converted to retinaldehyde by a reversible oxidation, and then retinaldehyde is irreversibly oxidized to retinoic acid. The oxidation of retinol is the rate-limiting step in retinoic acid production that determines the overall rate of retinoic acid biosynthesis from retinol. During the previous funding period, we have identified two subfamilies of the human short-chain dehydrogenase/reductase (SDRs) superfamily of proteins that are active toward retinoids. When expressed in intact cells, RoDH-like SDRs confer the ability to oxidize retinol to retinaldehyde, whereas RalR1-like enzymes confer the ability to reduce retinaldehyde back to retinol. Based on these observations, we propose that both groups of human SDRs contribute to retinoid homeostasis in human tissues by regulating the equilibrium between retinol and retinaldehyde, and thereby, regulating the rate of retinoic acid biosynthesis. To test our hypothesis, we propose to characterize retinoid metabolism in human and animal tissues in the presence and in the absence of RoDH- and RalR1-like SDRs. Experiments under the first specific aim will test a hypothesis that silencing of RoDH-like SDR gene expression in human organotypic skin raft culture results in a decreased rate of retinol oxidation to retinaldehyde, whereas silencing of RalR1- like SDR gene expression results in a decreased rate of retinaldehyde conversion to retinol. Experiments under the second specific aim will complement the ex vivo studies in human skin rafts with in vivo studies in RalR1 knockout mouse model and will test a hypothesis that RalR1 is essential for the reduction of retinaldehyde to retinol in mouse tissues. Because in vitro the mouse ortholog of RalR1 is highly active toward medium-chain aldehydes in addition to retinaldehydes, we will also test whether RalR1 contributes to the reduction of medium-chain aldehydes. It has been reported that retinoid homeostasis is disrupted in cancer cells, in alcoholic liver disease and in fetal alcohol syndrome. The proposed studies will provide a better understanding of the molecular bases underlying disregulation of retinoid metabolism in various pathological states.