Heme-, Redox-, and CO-dependent Regulation of Heme Homeostasis

血红素加氧酶(HO2和HO2)和REV-Erbβ在细胞保护和血红素依赖中发挥关键作用 CO代谢和信号转导。HO2和REV-Erbβ在其血红素和硫醇二硫化物的模式上有相似之处 通过它们的血红素反应基序(HRMS)进行氧化还原调节。HO1和HO2是唯一的血红素降解系统 在哺乳动物身上。HOS具有细胞保护作用，可催化血红素降解，以避免有毒的血红素堆积(&gt；1微米)。在……里面 此外，HO产生细胞保护信号分子CO和胆绿素(抗氧化剂的前体， 胆红素)。因此，HO1和HO2对心血管、肾脏和中枢神经系统具有保护作用 血红素/铁相关氧化应激所致的病理改变。REV-ERBβ，是一种转录抑制因子，发挥广泛的作用 新陈代谢、炎症反应和昼夜节律的控制。REV-ERB水平降低扰乱血脂 并导致心脏功能异常，如心脏线粒体功能、新陈代谢、 信号和收缩功能。HO2结合了三个等价物的血红素，一个在其催化位置，另一个在 它的两个调节血红素反应基序(HRM)中的每一个，而REV-ERBβ在其HRM上结合一个血红素。 HO1在其催化核心结合了单一的血红素，这与HO2高度保守。我们最近描述了一部小说 HO2催化核心在细胞血红素生物利用度调节中的作用 血红素缺乏条件下HO2对溶酶体降解的影响。我们现在将讨论HO2如何协调这些过程 以实现细胞内血红素的动态平衡，并确定可诱导的HO1是否起到类似的隔离作用 在血红素生物利用度方面。我们还发现了HO2中的HRMS在将血红素穿梭到催化剂中的新角色 在与血红素伴侣的相互作用中。我们现在将讨论这些体外数据的细胞相关性 以及伴侣是直接将血红素转移到催化核心，还是如我们所建议的那样转移到含有HRM的 HO2的尾巴。成功地将全长HO2及其膜结合区整合到纳米盘中 和脂质体，我们现在将比较这种生理上最相关的形式的HO在其 膜环境与可溶性蛋白的关系。我们最近发现，亚铁血红素的细胞形态， 以及最具生物有效性的形式是氧化(在Fe3+状态下)。我们还确定了一种耦合机制 在驱动其静止的Fe3+状态向Fe2+-CO状态转换的血红蛋白中。我们下一步打算 阐明REV-ERBβ从血红素负载到羰化的细胞调控机制。 此外，我们计划揭示由HO产生的细胞保护性CO是否被局部转移和 直接通过HO和REV-Erb之间形成的蛋白质-蛋白质复合体，或者如果HO产生的CO旅行到 通过被动细胞扩散来靶向蛋白质。我们的研究将有助于我们理解Ho参与细胞 对氧化应激诱导的心血管、肾脏和中枢神经系统病理和 为什么REV-ERBβ功能障碍与新陈代谢、昼夜节律和炎症相关。

Heme oxygenases (HO2 and HO2) and Rev-Erbβ play critical roles in cytoprotection and in heme-dependent CO metabolism and signaling. HO2 and Rev-Erbβ exhibit similarities in their modes of heme and thiol-disulfide redox regulation via their heme responsive motifs (HRMs). HO1 and HO2 are the sole heme degrading systems in mammals. The HOs are cytoprotective, catalyzing heme degradation to avert toxic heme buildup (>1 µM). In addition, HO produces both the cytoprotective signaling molecule CO and biliverdin (precursor of the antioxidant, bilirubin). Thus, HO1 and HO2 play a protective role against cardiovascular, renal, and central nervous system pathologies induced by heme/Fe-related oxidative stress. Rev-Erbβ, is a transcriptional repressor, exerting wide control of metabolism, inflammatory responses, and the circadian rhythm. Decreased Rev-Erb levels disrupt lipid homeostasis and cause abnormalities in heart functions like cardiac mitochondrial function, metabolism, signaling, and contractile function. HO2 binds three equivalents of heme, one at its catalytic site and another at each of its two regulatory heme responsive motifs (HRMs), whereas Rev-Erbβ binds a single heme at its HRM. HO1 binds a single heme at its catalytic core, which is highly conserved with HO2. We recently described novel roles for the HO2 catalytic core in regulating cellular heme bioavailability via heme sequestration and committing HO2 to lysosomal degradation under heme deficiency. We will now tackle how HO2 coordinates these processes for achieving cellular heme homeostasis and to determine if the inducible HO1 plays a similar sequestration role in heme bioavailability. We also uncovered novel roles for the HRMs in HO2 in shuttling heme to the catalytic site and in interacting with heme chaperones. We will now address the cellular relevance of these in vitro data and whether the chaperone transfers heme directly to the catalytic core or, as we propose, to the HRM-containing tail of HO2. Having successfully incorporated full-length-HO2 with its membrane-binding region into nanodiscs and liposomes, we will now compare the properties of this most physiologically relevant form of HO in its membrane environment with those of the soluble protein. We recently discovered that the cellular form of heme, as well as the most bioavailable form, is oxidized (in the Fe3+ state). We also identified a coupling mechanism within hemeproteins that drives conversion of their resting Fe3+ state to the Fe2+-CO state. We next intend to elucidate the cellular mechanism of Rev-Erbβ regulation starting from heme loading to carbonylation. Furthermore, we plan to reveal whether cytoprotective CO, which is generated by HO, is transferred locally and directly through a protein-protein complex formed between HO and Rev-Erb or if HO-generated CO travels to target proteins by passive cellular diffusion. Our research will help us to understand HO’s involvement in cellular protection against oxidative stress-induced cardiovascular, renal, and central nervous system pathologies and why dysfunction in Rev-erbβ is associated with disorders in metabolism, circadian rhythm, and inflammation.