Twin enzymes, divergent control: The cholesterogenic enzymes DHCR14 and LBR are differentially regulated transcriptionally and post-translationally
Twin enzymes, divergent control: The cholesterogenic enzymes DHCR14 and LBR are differentially regulated transcriptionally and post-translationally
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DOI：
10.1074/jbc.ra119.011323
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发表时间：
2020-02-28
影响因子：
4.8
通讯作者：
Brown, Andrew J.
中科院分区：
文献类型：
--
作者：
Capell-Hattam, Isabelle M.;Sharpe, Laura J.;Brown, Andrew J.
胆固醇合成是一个严格调控的过程，无论是转录还是翻译后都是如此。对胆固醇合成的转录控制相对来说是很清楚的。然而，在胆固醇生物合成的20种酶中，翻译后调节只有一小部分被研究过。胆固醇产生的四种类固醇还原酶中的三种，7-脱氢胆固醇还原酶(DHCR7)、14-脱氢胆固醇还原酶(DHCR14)和层粘连蛋白-B受体(LBR)，在进化上有很高的序列同源性和预测的结构同源性。DHCR14和LBR在胆固醇生物合成中具有相同的？-14还原酶活性，但对它们的翻译后调控知之甚少。我们先前已经确定了DHCR7翻译后控制的特定模式，但尚不清楚这些调控机制是否与DHCR14和LBR相同。利用稳定表达表位标记的DHCR14或LBR的CHO-7细胞，我们研究了这些酶的翻译后调节。我们发现，DHCR14和LBR经历了不同的翻译后调节，在胆固醇和其他甾醇中间体的触发下，DHCR14迅速翻转，而LBR保持稳定。DHCR14是通过泛素-蛋白酶体系统降解的，我们鉴定了几个可能的相互作用伙伴，包括一些调节DHCR14水平的E3连接酶。有趣的是，我们发现在一系列人体组织中的基因表达与C14-类固醇还原酶之间呈负相关；一种酶或另一种酶倾向于在每个组织中主要表达。总体而言，我们的发现表明，虽然LBR往往是结构性活性的C14-甾醇还原酶，但DHCR14的水平是可调节的，对局部细胞对胆固醇的需求做出反应。
Cholesterol synthesis is a tightly regulated process, both transcriptionally and post-translationally. Transcriptional control of cholesterol synthesis is relatively well-understood. However, of the ?20 enzymes in cholesterol biosynthesis, post-translational regulation has only been examined for a small number. Three of the four sterol reductases in cholesterol production, 7-dehydrocholesterol reductase (DHCR7), 14-dehydrocholesterol reductase (DHCR14), and lamin-B receptor (LBR), share evolutionary ties with a high level of sequence homology and predicted structural homology. DHCR14 and LBR uniquely share the same ?-14 reductase activity in cholesterol biosynthesis, yet little is known about their post-translational regulation. We have previously identified specific modes of post-translational control of DHCR7, but it is unknown whether these regulatory mechanisms are shared by DHCR14 and LBR. Using CHO-7 cells stably expressing epitope-tagged DHCR14 or LBR, we investigated the post-translational regulation of these enzymes. We found that DHCR14 and LBR undergo differential post-translational regulation, with DHCR14 being rapidly turned over, triggered by cholesterol and other sterol intermediates, whereas LBR remained stable. DHCR14 is degraded via the ubiquitin-proteasome system, and we identified several DHCR14 and DHCR7 putative interaction partners, including a number of E3 ligases that modulate DHCR14 levels. Interestingly, we found that gene expression across an array of human tissues showed a negative relationship between the C14-sterol reductases; one enzyme or the other tends to be predominantly expressed in each tissue. Overall, our findings indicate that whereas LBR tends to be the constitutively active C14-sterol reductase, DHCR14 levels are tunable, responding to the local cellular demands for cholesterol.