Overexpression of Rcan1-1L Inhibits Hypoxia-Induced Cell Apoptosis through Induction of Mitophagy

Mitophagy, a cellular process that selectively targets dysfunctional mitochondria for degradation, is currently a hot topic in research into the pathogenesis and treatment of many human diseases. Considering that hypoxia causes mitochondrial dysfunction, which results in cell death, we speculated that selective activation of mitophagy might promote cell survival under hypoxic conditions. In the present study, we introduced the Regulator of calcineurin 1-1L (Rcan1-1L) to initiate the mitophagy pathway and aimed to evaluate the effect of Rcan1-1L-induced mitophagy on cell survival under hypoxic conditions. Recombinant adenovirus vectors carrying Rcan1-1L were transfected into human umbilical vein endothelial cells and human adult cardiac myocytes. Using the 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide MTT assay and Trypan blue exclusion assay, Rcan1-1L overexpression was found to markedly reverse cell growth inhibition induced by hypoxia. Additionally, Rcan1-1L overexpression inhibited cell apoptosis under hypoxic conditions, as detected by annexin V-fluorescein isothiocyanate (FITC)/propidium iodide (PI) apoptosis assay. Meanwhile, the mitochondria-mediated cell apoptotic pathway was inhibited by Rcan1-1L. In contrast, knockdown of Rcan1-1L accelerated hypoxia-induced cell apoptosis. Moreover, Rcan1-1L overexpression significantly reduced mitochondrial mass, decreased depolarized mitochondria, and downregulated ATP and reactive oxygen species production. We further delineated that the loss of mitochondrial mass was due to the activation of mitophagy induced by Rcan1-1L. Rcan1-1L overexpression activated autophagy flux and promoted translocation of the specific mitophagy receptor Parkin into mitochondria from the cytosol, whereas inhibition of autophagy flux resulted in the accumulation of Parkin-loaded mitochondria. Finally, we demonstrated that mitochondrial permeability transition pore opening was significantly increased by Rcan1-1L overexpression, which suggested that Rcan1-1L might evoke mitophagy through regulating mitochondrial permeability transition pores. Taken together, we provide evidence that Rcan1-1L overexpression induces mitophagy, which in turn contributes to cell survival under hypoxic conditions, revealing for the first time that Rcan1-1L-induced mitophagy may be used for cardioprotection.     

线粒体自噬与人类疾病

线粒体在生物体的新陈代谢中起着非常重要的作用,不仅为代谢活动提供能量,还可以产生具有信号传递和基因调节作用的活性氧．线粒体发生功能障碍或损坏都可能造成严重的后果,甚至导致细胞死亡．受损线粒体通常通过线粒体自噬降解,研究发现线粒体自噬紊乱与多种疾病发生有关．本文阐述了线粒体自噬的调节机制和介导途径,详细论述了近年来线粒体自噬在神经退行性疾病、心脏病及肿瘤中的作用,总结指出线粒体自噬的两面性,即一方面正常范围内的线粒体自噬可以维持人体细胞的正常生理机能,另一方面,线粒体自噬水平过高和过低都会引发疾病．     

Cardiolipin remodeling by TAZ/tafazzin is selectively required for the initiation of mitophagy

Tafazzin (TAZ) is a phospholipid transacylase that catalyzes the remodeling of cardiolipin, a mitochondrial phospholipid required for oxidative phosphorylation. Mutations of TAZ cause Barth syndrome, which is characterized by mitochondrial dysfunction and dilated cardiomyopathy, leading to premature death. However, the molecular mechanisms underlying the cause of mitochondrial dysfunction in Barth syndrome remain poorly understood. Here we investigated the role of TAZ in regulating mitochondrial function and mitophagy. Using primary mouse embryonic fibroblasts (MEFs) with doxycycline-inducible knockdown of Taz, we showed that TAZ deficiency in MEFs caused defective mitophagosome biogenesis, but not other autophagic processes. Consistent with a key role of mitophagy in mitochondria quality control, TAZ deficiency in MEFs also led to impaired oxidative phosphorylation and severe oxidative stress. Together, these findings provide key insights on mitochondrial dysfunction in Barth syndrome, suggesting that pharmacological restoration of mitophagy may provide a novel treatment for this lethal condition.     

Cardiolipin in energy transducing membranes

Cardiolipin is a phospholipid located exclusively in energy transducing membranes such as the bacterial cytoplasmic membrane and the inner membrane of mitochondria. It plays both a structural and a functional role in many multimeric complexes associated with these membranes. The role of cardiolipin in higher order organization of components of the mitochondrial respiratory chain revealed by a combined molecular genetic and biochemical approach is described.Translated from Biokhimiya, Vol. 70, No. 2, 2005, pp. 191–196.Original Russian Text Copyright © 2005 by Mileykovskaya, Zhang, Dowhan.This revised version was published online in April 2005 with corrections to the post codes.     

线粒体自噬的研究进展

线粒体自噬（mitophagy）是指细胞通过自噬的机制选择性地清除线粒体的过程。选择性清除受损伤或功能不完整的线粒体对于整个线粒体网络的功能完整性和细胞生存来说十分关键。线粒体自噬的异常和很多疾病密切相关,因此对于线粒体自噬的具体分子机制以及生理意义研究有很重要的生物学意义。线粒体自噬的研究是目前生物学领域的研究热点,该文主要综述了近年来在线粒体自噬领域取得的研究进展,旨在为相关领域的研究提供参考。     

Cardiolipin remodeling by ALCAT1 links mitochondrial dysfunction to Parkinson’s diseases

Cardiolipin (CL) is a mitochondrial signature phospholipid that is required for membrane structure, respiration, dynamics, and mitophagy. Oxidative damage of CL by reactive oxygen species is implicated in the pathogenesis of Parkinson's disease (PD), but the underlying cause remains elusive. This work investigated the role of ALCAT1, an acyltransferase that catalyzes pathological remodeling of CL in various aging‐related diseases, in a mouse model of PD induced by 1‐methyl‐4‐phenyl‐1,2,4,6‐tetrahydropyridine (MPTP). We show that MPTP treatment caused oxidative stress, mtDNA mutations, and mitochondrial dysfunction in the midbrain. In contrast, ablation of the ALCAT1 gene or pharmacological inhibition of ALCAT1 prevented MPTP‐induced neurotoxicity, apoptosis, and motor deficits. ALCAT1 deficiency also mitigated mitochondrial dysfunction by modulating DRP1 translocation to the mitochondria. Moreover, pharmacological inhibition of ALCAT1 significantly improved mitophagy by promoting the recruitment of Parkin to dysfunctional mitochondria. Finally, ALCAT1 expression was upregulated by MPTP and by α‐synucleinopathy, a key hallmark of PD, whereas ALCAT1 deficiency prevented α‐synuclein oligomerization and S‐129 phosphorylation, implicating a key role of ALCAT1 in the etiology of mouse models of PD. Together, these findings identify ALCAT1 as a novel drug target for the treatment of PD.     

心磷脂重构与心血管疾病

心磷脂（cardiolipin, CL）是线粒体内膜的特征性磷脂,参与线粒体嵴的形成。心磷脂在线粒体内的合成伴随着特殊的分子重构过程,从而使其自身的4条酰基链形成特定的组成,以发挥其特殊的生理功能。研究发现,心磷脂重构对维持线粒体的形态及功能至关重要,其重构异常是大多数心血管疾病（cardiovascular disease, CVD）共有的病理现象,相应的分子机制研究得到了广泛关注。本文主要对心磷脂的理化特性及其生物合成途径,以及心磷脂重构在巴氏综合征（Barth syndrome, BTHS）、糖尿病心肌病（diabetic cardiomyopathy, DCM）以及心力衰竭（heart failure, HF）等心血管疾病的病理生理过程研究中的进展进行综述,以期为与心磷脂重构相关的心血管疾病的病理生理基础研究和药物干预的分子机制研究提供参考。     

Ensemble Properties of Bax Determine Its Function

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线粒体自噬在感染性疾病中的作用机制研究进展

线粒体自噬作为一种选择性自噬方式是近年研究的热点.细胞通过自噬机制选择性清除受损伤或不必需的线粒体,从而维持其功能稳态.近年来,越来越多的研究聚焦于病原体通过胁迫线粒体自噬在机体感染过程中调节先天免疫信号通路,从而影响感染性疾病的进程.本文分别从线粒体自噬在病毒、细菌和真菌感染性疾病中的作用机制研究进展进行综述,以期为...     

Surface-Binding to Cardiolipin Nanodomains Triggers Cytochrome c Pro-apoptotic Peroxidase Activity via Localized Dynamics

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Mitophagy receptor FUNDC1 regulates mitochondrial dynamics and mitophagy

Mitochondrial fragmentation due to imbalanced fission and fusion of mitochondria is a prerequisite for mitophagy, however, the exact “coupling” of mitochondrial dynamics and mitophagy remains unclear. We have previously identified that FUNDC1 recruits MAP1LC3B/LC3B (LC3) through its LC3-interacting region (LIR) motif to initiate mitophagy in mammalian cells. Here, we show that FUNDC1 interacts with both DNM1L/DRP1 and OPA1 to coordinate mitochondrial fission or fusion and mitophagy. OPA1 interacted with FUNDC1 via its Lys70 (K70) residue, and mutation of K70 to Ala (A), but not to Arg (R), abolished the interaction and promoted mitochondrial fission and mitophagy. Mitochondrial stress such as selenite or FCCP treatment caused the disassembly of the FUNDC1-OPA1 complex while enhancing DNM1L recruitment to the mitochondria. Furthermore, we observed that dephosphorylation of FUNDC1 under stress conditions promotes the dissociation of FUNDC1 from OPA1 and association with DNM1L. Our data suggest that FUNDC1 regulates both mitochondrial fission or fusion and mitophagy and mediates the “coupling” across the double membrane for mitochondrial dynamics and quality control.     

Parkin介导的线粒体自噬及细胞器互作机制

线粒体是细胞生理代谢活动发生的重要场所.线粒体生发降解平衡是维持能量代谢稳定的重要保障.Parkin作为E3泛素连接酶,通过PINK1/Parkin、LC3等多种信号参与调控线粒体自噬过程.此外,Parkin还能够影响线粒体相关内质网膜、调控细胞器间钙流,在线粒体-内质网对话过程中调控溶酶体途径介导的线粒体自噬.脂肪组...     

线粒体自噬影响胰岛素抵抗的作用及机制

胰岛素抵抗（IR）是诱发许多代谢疾病的关键因素,包括代谢综合征、非酒精性脂肪性肝病、动脉粥样硬化和2型糖尿病（T2DM）。随着相关代谢疾病日益增多,寻找新的治疗靶点迫在眉睫。线粒体自噬是一种选择性自噬,其通过清除受损和功能失调的线粒体以维持正常线粒体功能和能量代谢。研究发现,线粒体自噬在代谢疾病中有积极作用,线粒体自噬受到各种信号通路与信号分子调控而改善代谢疾病,如AMPK/ULK1、PINK1/Parkin信号通路以及BNIP3/Nix和FUNDC1等信号分子。本文阐述了线粒体自噬在胰岛素抵抗中的作用及调控机制,综述了近年的相关研究进展。     

氧化应激下植物线粒体自噬分析

线粒体自噬,是指通过选择性的识别并清除损伤、衰老及功能紊乱的线粒体,对维持细胞内线粒体质量和数量的平衡产生了重要作用。与动物和酵母中线粒体自噬的研究进展相比,植物线粒体自噬的途径及具体调控机制尚不明确。基于GFP标签,本文探究了氧化胁迫下植物线粒体自噬发生情况。研究发现甲基紫精诱导线粒体在液泡中积累,并呈现两种状态:1) GFP小体包含的线粒体; 2)不含GFP的线粒体。本研究发展的GFP标签策略可为植物线粒体自噬关键调控因子的筛选提供借鉴。     

巨噬细胞凋亡及其调控

巨噬细胞通过介导和调控自身及其他细胞凋亡而实现其免疫调节和效应细胞功能.引起巨噬细胞凋亡的原因有生物、化学、病理、自身等因素.不仅巨噬细胞自身凋亡和凋亡调控有其特点,更为有趣的是,巨噬细胞可根据需要：介导或抑制自身凋亡;介导或抑制其他细胞凋亡;抑制自身凋亡,介导其他细胞凋亡.这可能是巨噬细胞在免疫调节,特别是肿瘤免疫中发挥重要作用的基础.     

Mitophagy in hematopoietic stem cells

Hematopoietic stem cells (HSCs) are inherently quiescent and self-renewing, yet can differentiate and commit to multiple blood cell types. Intracellular mitochondrial content is dynamic, and there is an increase in mitochondrial content during differentiation and lineage commitment in HSCs. HSCs reside in a hypoxic niche within the bone marrow and rely heavily on glycolysis, while differentiated and committed progenitors rely on oxidative phosphorylation. Increased oxidative phosphorylation during differentiation and commitment is not only due to increased mitochondrial content but also due to changes in mitochondrial cytosolic distribution and efficiency. These changes in the intracellular mitochondrial landscape contribute signals toward regulating differentiation and commitment. Thus, a functional relationship exists between the mitochondria in HSCs and the state of the HSCs (i.e., stemness vs. differentiated). This review focuses on how autophagy-mediated mitochondrial clearance (i.e., mitophagy) may affect HSC mitochondrial content, thereby influencing the fate of HSCs and maintenance of hematopoietic homeostasis.     

促凋亡蛋白Bid诱导肝细胞凋亡的机制

为研究促凋亡蛋白Bid对肝细胞凋亡过程中的调节机制 ,在体内和体外分别用TNF α或抗Fas抗体诱导小鼠肝细胞凋亡 .免疫荧光染色观察Bax转位和构象变化 ;采用ELISA检测caspase 3和 8的活性 ;Western印迹测定Bid和Bax的裂解活化及Bax的转位和插入 .结果显示 :TNF α或抗Fas抗体通过激活Bid导致Bax转位和构象变化 ,使Bax得以插入线粒体膜诱导肝细胞凋亡 .阻断Bid的作用 ,则Bax的转位和插入明显被削弱 ,肝细胞的凋亡受到抑制 .提示由死亡受体诱导的肝细胞调亡可能受Bid调节 ,Bax转位和插入依赖于Bid .     

Mitophagy receptor FUNDC1 regulates mitochondrial homeostasis and protects the heart from I/R injury

Mitophagy plays pivotal roles in the selective disposal of unwanted mitochondria, and accumulation of damaged mitochondria has been linked to aging-related diseases. However, definitive proof that mitophagy regulates mitochondrial quality in vivo is lacking. It is also largely unclear whether damaged mitochondria are the cause or just the consequence of these diseases. We previously showed that FUNDC1 is a mitophagy receptor that interacts with LC3 to mediate mitophagy in response to hypoxia in cultured cells. We established Fundc1 knockout mouse models and used genetic and biochemical approaches, including a synthetic peptide that blocks the FUNDC1-LC3 interaction, to demonstrate that mitophagy regulates both mitochondrial quantity and quality in vivo in response to hypoxia or hypoxic conditions caused by ischemia-reperfusion (I/R) heart injury. We found that hypoxic mitophagy regulates platelet activities. Furthermore, we found that hypoxic preconditioning induces FUNDC1-dependent mitophagy in platelets and reduces I/R-induced heart injury, suggesting a new strategy to protect cardiac function and fight cardiovascular diseases.