Rahaman Mizanur M, Nguyen Anh T, Miller Megan P, Hahn Scott A, Sparacino-Watkins Courtney, Jobbagy Soma, Carew Nolan T, Cantu-Medellin Nadiezhda, Wood Katherine C, Baty Catherine J, Schopfer Francisco J, Kelley Eric E, Gladwin Mark T, Martin Emil, Straub Adam C
From the Heart, Lung, Blood and Vascular Medicine Institute (M.M.R., A.T.N., M.P.M., S.A.H., C.S.-W., N.T.C., N.C.-M., K.C.W., M.T.G., A.C.S.), Division of Pulmonary, Allergy and Critical Care Medicine (C.S.-W., M.T.G.), Department of Pharmacology and Chemical Biology (S.J., C.J.B., F.J.S., A.C.S.), and Division of Renal-Electrolyte (C.J.B.), University of Pittsburgh, PA; Department of Physiology and Pharmacology, West Virginia University School of Medicine, Morgantown (E.E.K.); and Department of Internal Medicine, Division of Cardiology, University of Texas Houston Medical School (E.M.).
Circ Res. 2017 Jul 7;121(2):137-148. doi: 10.1161/CIRCRESAHA.117.310705. Epub 2017 Jun 5.
Soluble guanylate cyclase (sGC) heme iron, in its oxidized state (Fe), is desensitized to NO and limits cGMP production needed for downstream activation of protein kinase G-dependent signaling and blood vessel dilation.
Although reactive oxygen species are known to oxidize the sGC heme iron, the basic mechanism(s) governing sGC heme iron recycling to its NO-sensitive, reduced state remain poorly understood.
Oxidant challenge studies show that vascular smooth muscle cells have an intrinsic ability to reduce oxidized sGC heme iron and form protein-protein complexes between cytochrome b5 reductase 3, also known as methemoglobin reductase, and oxidized sGC. Genetic knockdown and pharmacological inhibition in vascular smooth muscle cells reveal that cytochrome b5 reductase 3 expression and activity is critical for NO-stimulated cGMP production and vasodilation. Mechanistically, we show that cytochrome b5 reductase 3 directly reduces oxidized sGC required for NO sensitization as assessed by biochemical, cellular, and ex vivo assays.
Together, these findings identify new insights into NO-sGC-cGMP signaling and reveal cytochrome b5 reductase 3 as the first identified physiological sGC heme iron reductase in vascular smooth muscle cells, serving as a critical regulator of cGMP production and protein kinase G-dependent signaling.
可溶性鸟苷酸环化酶（sGC）的血红素铁在氧化状态（Fe）下对一氧化氮（NO）不敏感，限制了蛋白激酶G依赖性信号传导和血管舒张下游激活所需的环磷酸鸟苷（cGMP）生成。
尽管已知活性氧会氧化sGC的血红素铁，但对于sGC血红素铁循环至其对NO敏感的还原状态的基本机制仍知之甚少。
氧化剂刺激研究表明，血管平滑肌细胞具有将氧化的sGC血红素铁还原的内在能力，并在细胞色素b5还原酶3（也称为高铁血红蛋白还原酶）与氧化的sGC之间形成蛋白质-蛋白质复合物。血管平滑肌细胞中的基因敲低和药理学抑制表明，细胞色素b5还原酶3的表达和活性对于NO刺激的cGMP生成和血管舒张至关重要。从机制上讲，我们通过生化、细胞和离体实验表明，细胞色素b5还原酶3直接还原NO致敏所需的氧化sGC。
总之，这些发现为NO-sGC-cGMP信号传导提供了新的见解，并揭示细胞色素b5还原酶3是血管平滑肌细胞中首个被鉴定出的生理性sGC血红素铁还原酶，是cGMP生成和蛋白激酶G依赖性信号传导的关键调节因子。
