SHORT-CHAIN DEHYDROGENASES IN RETINOL/STEROL METABOLISM

视黄酸在多种胎儿和成人的分化和发育中起着重要作用 组织中视黄酸由视黄醇经两步生产：首先，视黄醇通过还原反应转化为视黄醛。 可逆氧化，然后将视黄醇不可逆地氧化成视黄酸。视黄醇的氧化是 视黄酸生产中的限速步骤，决定视黄酸生物合成的总速率 从视黄醇。在上一个资助期间，我们已经确定了人类短链的两个亚家族， 脱氢酶/还原酶（SDR）超家族的蛋白质，其对类视色素具有活性。表达时 在完整细胞中，RoDH样SDR赋予将视黄醇氧化为视黄醇醛的能力，而RalR 1样SDR赋予将视黄醇氧化为视黄醇醛的能力。 酶赋予将视黄醇还原回视黄醇的能力。根据这些观察，我们 我认为这两组人SDR通过调节人组织中的类维生素A稳态， 视黄醇和视黄醇醛之间的平衡，从而调节视黄酸的速率 生物合成为了验证我们的假设，我们建议在人类和动物中描述类维生素A代谢 在存在和不存在RoDH-和RalR 1-样SDR的情况下的组织。实验根据第一 具体目的将检验人器官型中RoDH样SDR基因表达沉默的假设 皮筏培养导致视黄醇氧化为视黄醇的速率降低，而RalR 1- 类似于SDR基因表达导致视黄醇转化为视黄醇的速率降低。实验 在第二个具体目标下，将补充人体皮肤筏的离体研究， RalR 1基因敲除小鼠模型，并将检验RalR 1对于减少 小鼠组织中的视黄醇转化为视黄醇。因为在体外，RalR 1的小鼠直系同源物是高度活性的， 除了视黄醇外，我们还将测试RalR 1是否有助于 中链醛的还原。据报道，类维生素A稳态被破坏， 癌细胞，酒精性肝病和胎儿酒精综合征。拟议的研究将提供一个 更好地理解维甲酸代谢失调的分子基础， 病理状态。

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.