Department of Molecular, Cellular & Biomedical Sciences, City University of New York School of Medicine, City College of New York, NY, New York, United States of America.
Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, United States of America.
J Mol Cell Cardiol. 2021 Jun;155:36-49. doi: 10.1016/j.yjmcc.2021.02.013. Epub 2021 Feb 27.
Thioredoxin-interacting protein (Txnip) is a novel molecular target with translational potential in diverse human diseases. Txnip has several established cellular actions including binding to thioredoxin, a scavenger of reactive oxygen species (ROS). It has been long recognized from in vitro evidence that Txnip forms a disulfide bridge through cysteine 247 (C247) with reduced thioredoxin to inhibit the anti-oxidative properties of thioredoxin. However, the physiological significance of the Txnip-thioredoxin interaction remains largely undefined in vivo.
A single mutation of Txnip, C247S, abolishes the binding of Txnip with thioredoxin. Using a conditional and inducible approach with a mouse model of a mutant Txnip that does not bind thioredoxin, we tested whether the interaction of thioredoxin with Txnip is required for Txnip's pro-oxidative or cytotoxic effects in the heart.
Overexpression of Txnip C247S in cells resulted in a reduction in ROS, due to an inability to inhibit thioredoxin. Hypoxia (1% O, 24 h)-induced killing effects of Txnip were decreased by lower levels of cellular ROS in Txnip C247S-expressing cells compared with wild-type Txnip-expressing cells. Then, myocardial ischemic injuries were assessed in the animal model. Cardiomyocyte-specific Txnip C247S knock-in mice had better survival with smaller infarct size following myocardial infarction (MI) compared to control animals. The absence of Txnip's inhibition of thioredoxin promoted mitochondrial anti-oxidative capacities in cardiomyocytes, thereby protecting the heart from oxidative damage induced by MI. Furthermore, an unbiased RNA sequencing screen identified that hypoxia-inducible factor 1 signaling pathway was involved in Txnip C247S-mediated cardioprotective mechanisms.
Txnip is a cysteine-containing redox protein that robustly regulates the thioredoxin system via a disulfide bond-switching mechanism in adult cardiomyocytes. Our results provide the direct in vivo evidence that regulation of redox state by Txnip is a crucial component for myocardial homeostasis under ischemic stress.
硫氧还蛋白相互作用蛋白（Txnip）是一种新型的分子靶点，在多种人类疾病的转化研究中具有潜力。Txnip 具有多种已确定的细胞作用，包括与硫氧还蛋白结合，后者是活性氧（ROS）的清除剂。从体外证据中早就认识到，Txnip 通过半胱氨酸 247（C247）与还原型硫氧还蛋白形成二硫键，从而抑制硫氧还蛋白的抗氧化特性。然而，Txnip-硫氧还蛋白相互作用的生理意义在体内仍然很大程度上没有得到定义。
Txnip 的单个突变 C247S 消除了 Txnip 与硫氧还蛋白的结合。使用一种具有突变 Txnip 的条件和诱导型小鼠模型（该突变 Txnip 不能与硫氧还蛋白结合），我们测试了硫氧还蛋白与 Txnip 的相互作用是否是 Txnip 在心脏中的促氧化或细胞毒性作用所必需的。
细胞中 Txnip C247S 的过表达导致 ROS 减少，这是由于无法抑制硫氧还蛋白。与野生型 Txnip 表达细胞相比，Txnip C247S 表达细胞中的细胞 ROS 水平较低，从而降低了缺氧（1% O，24 h）诱导的 Txnip 杀伤作用。然后，在动物模型中评估心肌缺血损伤。与对照动物相比，心肌细胞特异性 Txnip C247S 敲入小鼠在心肌梗死（MI）后具有更好的存活率和更小的梗死面积。缺乏 Txnip 对硫氧还蛋白的抑制作用促进了心肌细胞中线粒体的抗氧化能力，从而保护心脏免受 MI 诱导的氧化损伤。此外，一项无偏 RNA 测序筛选发现，缺氧诱导因子 1 信号通路参与了 Txnip C247S 介导的心脏保护机制。
Txnip 是一种含半胱氨酸的氧化还原蛋白，它通过二硫键转换机制在成年心肌细胞中强烈调节硫氧还蛋白系统。我们的结果提供了直接的体内证据，表明 Txnip 通过调节氧化还原状态是心肌在缺血应激下维持体内平衡的关键组成部分。
