生理病理状态下线粒体合成ATP动态调控机制

线粒体是细胞的代谢中心之一,不仅产生大量的ATP为细胞提供能量,还参与多种生物分子（例如核酸、氨基酸、胆固醇和脂肪酸）合成及代谢废物的处理。ATP是细胞重要的“能源货币”,是能量载体和信号分子,参与调节细胞的各种生命活动。动物与人在激烈运动时,ATP消耗速率增加数十倍,但细胞内的ATP仍维持在“设定点”水平,不出现降低。因此,传统生理学观点认为,动物细胞内ATP水平保持恒定。但新的研究结果表明,生物细胞内ATP水平存在波动。生理条件下,增加能量物资（糖、脂和氨基酸等）和氧供,促进线粒体ATP合成,可使细胞内ATP水平出现一过性升高。新的研究证明,在肥胖情况下,由于能量物质的过多供应,细胞内ATP水平出现持续性升高,构成代谢紊乱的源头信号。线粒体ATP合成受多种因素影响,如氧化应激、钙超载、缺氧、线粒体膜通透性增加和线粒体DNA突变等。这些因素与疾病条件下细胞内ATP水平持续降低相关,常见的疾病包括阿尔茨海默症、帕金森疾病、精神分裂症、肿瘤、心衰、全身炎症反应综合征等。本综述简要概述线粒体调节细胞内ATP水平的研究进展,重点讨论造成ATP波动的因素、机制及病理生理学意义。     

生理病理状态下线粒体合成ATP的动态调控机制

线粒体是细胞的代谢中心之一,不仅产生大量的ATP为细胞提供能量,还参与多种生物分子(例如核酸、氨基酸、胆固醇和脂肪酸)合成及代谢废物的处理.ATP是细胞重要的“能源货币”,是能量载体和信号分子,参与调节细胞的各种生命活动.动物与人在激烈运动时,ATP消耗速率增加数十倍,但细胞内的ATP仍维持在“设定点”水平,不出现降低...     

细胞内ATP水平调节机制在肥胖病理生理中的作用

ATP是细胞的重要能源。传统观点认为细胞内ATP水平相对恒定,不会出现持续升高。而新的研究提示:在能量过剩状态下,ATP水平在多种组织中持续升高,这种升高与能量过剩引起的代谢紊乱密切相关,但其升高机制尚不清楚。本文通过回顾本研究组前期实验结果和文献,论述调节细胞内ATP水平的多种因素,其中涉及超氧离子、线粒体炫、抗氧化剂、抗凋亡蛋白(Bcl-xL)、AMP活化的蛋白激酶以及二甲双胍等,重点讨论这些因素改变ATP设定点的作用及其潜在机制,评估它们在细胞内ATP水平升高或降低中扮演的角色。本文以能量过剩的分子机制为中心,探讨细胞内ATP水平升高导致胰岛素抵抗的分子机制,同时阐明新的实验结果与ATP传统观点之间发生矛盾的可能原因。作者认为在肥胖条件下,ATP水平升高是细胞能量过剩的重要信号,该信号通过激活反馈通路抑制线粒体功能,造成糖脂代谢紊乱。     

ATP浓度和缺氧暴露对大鼠脑线粒体RNA和蛋白质体外合成的影响

本文探讨介质中ATP浓度和急,慢性缺氧暴露对大鼠脑线粒体内RNA和蛋白质合成的影响。用差速离心法分离正常和低压舱模拟4000m高原急性连续缺氧暴露3d和慢性连续缺氧暴露40d大鼠脑线粒体,用体外无细胞（cell-free in vitro)^3H-UTP和^3H-Leucine掺入法分别测定线粒体RNA和蛋白质合成活性,结果显示,大鼠急性缺氧暴露后大脑皮质线粒体RNA体外合成活性降低40%,蛋白质合成活性降低60%;慢性缺氧暴露后线粒体RNA和蛋白质合成活性分别为对照的72%和76%;ATP对正常大鼠脑线粒体RNA以及蛋白质的体外合成活性的影响均呈双相性,大于或小于1mmol/L均可产生不同程度的抑制效应,结果提示,缺氧可在转录和翻译两个水平上影响脑线粒体mtDNA的表达,而慢性缺氧暴露时,线粒体半自主性功能的改善可能是机体对缺氧适应的细胞机制之一;ATP对脑线粒体内转录和释放活性的调节是一种经济有效的反馈调节方式。     

酵母线粒体ATP合酶生物合成及组装机制研究进展

线粒体ATP合酶是线粒体氧化磷酸化的关键酶,其功能缺陷会导致能量代谢障碍相关的线粒体疾病。线粒体ATP合酶是由多个亚基组成的蛋白复合物,其生物合成和组装是个复杂的生物过程。酵母是研究线粒体ATP合酶结构、生物合成和组装机制的模式实验材料之一,且相关研究取得了很多进展。本文概述了国内外用酿酒酵母研究线粒体ATP合酶的结构、调控线粒体ATP合酶亚基生物合成和组装的辅助蛋白及合酶的模块化组装过程的研究进展,以期为线粒体ATP合酶的工作机制及相关线粒体疾病的研究提供理论借鉴和参考依据。     

竹节参对力竭运动大鼠心肌线粒体ATP酶活性的影响

目的：探讨竹节参对力竭运动大鼠心肌线粒体ATP酶活性的影响。方法：建立力竭运动大鼠模型,测定心肌线粒体ATP酶的活性,研究竹节参对大强度耐力训练大鼠心肌线粒体的保护作用。结果：力竭运动引起大鼠心肌线粒体ATPase（Na＋,K＋-ATPase和Ca2＋-ATPase）活性显著下降,而运动加药组Ca2＋-ATPase有显著升高,Na＋,K＋-ATPase也有明显升高,且ATPase活性均接近于安静对照组的水平。结论：竹节参可提高力竭运动大鼠心肌线粒体内Na＋,K＋-ATP酶和Ca2＋-ATP酶的活性,提示其具有保护线粒体的作用。     

线粒体ATP合酶抑制因子1在线粒体稳态中的调节作用

线粒体作为细胞的重要能量来源,其数量、质量及功能的稳定对维持细胞的正常活动至关重要,且其稳态的调节依赖于线粒体质量控制系统(包括线粒体自噬、线粒体融合/分裂及线粒体生物合成等)。线粒体蛋白ATP合酶抑制因子1(ATP synthase inhibitor 1, IF1)是线粒体基质中抑制F1FoATP酶/合酶活性的天然小分子蛋白质。在细胞缺氧缺血等特殊生理情况下, IF1通过改变自身的聚合状态,抑制F1FoATP酶水解ATP的活性,从而抑制细胞内的ATP被过度水解。最近的研究证实, IF1的抑制作用是双向的,其即可抑制F1FoATP酶活性,又可抑制F1FoATP合酶活性。因此, IF1可通过靶向F1FoATP酶/合酶活性及相关信号通路,参与调节线粒体质量,维持线粒体稳态。该文综述IF1在线粒体质量控制中的相关调节机制,包括IF1维持线粒体氧化还原平衡、IF1介导线粒体自噬、IF1促进线粒体融合/分裂三条通路,以及三者之间相互作用的关系,为探索IF1在相关疾病的发生、发展及治疗中的作用提供理论参考。     

线粒体动力学及线粒体自噬调控机制的研究进展

线粒体形态和功能的异常与多种疾病的发生密切相关。线粒体通过不断的分裂和融合,维持线粒体网络的动态平衡,该过程称为线粒体动力学,是维持线粒体形态、分布和数量,保证细胞稳态的重要基础。此外,机体还通过线粒体自噬过程降解胞内功能异常的线粒体,维持线粒体稳态。线粒体动力学与线粒体自噬二者之间可相互调控,共同维持线粒体质量平衡。探讨线粒体动力学和线粒体自噬的调控机制对揭示多种疾病发生的分子机制、开发新的靶向线粒体动力学蛋白或线粒体自噬调控蛋白的药物具有重要意义。本文从线粒体动力学与线粒体自噬出发,对线粒体动力学调控机制、线粒体自噬及其发生机制以及二者的相互作用关系、线粒体动力学及线粒体自噬与人类相关疾病等方面作一综述。     

外源胆固醇对水稻根端线粒体ATP酶活力的影响

外源胆固醇无论是通过根系吸收或是直接与离体线粒体一起温育的方式,在试验浓度范围内均能提高水稻根端线粒体ATP酶的活力,同时观察到外源胆固醇能明显降低ATP酶表现活化能(Apparent activation energy,AEa)在Arrhenius图上的折点温度。其中通过根系吸收进入线粒体膜内后,其线粒体ATP酶AEa的两个折点温度由对照的27.7℃和15.5℃分别降低到24.5℃和12.7℃;直接与离体线粒体一起温育的两个折点温度分别降低到18.8℃和9.6℃。试验结果证明,适量的外源胆固醇不仅对水稻根端线粒体ATP酶活力具有明显的促进作用,而且对降低线粒体膜脂的相变温度也有明显的调节作用。     

线粒体囊泡调控机制与生理功能研究进展

线粒体在细胞的生命活动过程中承担重要作用,线粒体通过自身质量控制维持线粒体健康.线粒体囊泡作为一种新型的线粒体质量控制机制,通过靶向到不同的细胞器,调控线粒体内氧化/受损蛋白的降解;激活免疫系统,发挥抗原呈递和杀灭细菌的功能,从而维持线粒体以及细胞的稳态平衡.本文就线粒体囊泡的调控机制以及生物学功能的研究进展进行综述.     

Changes in ATP Concentration, Mitochondrial Structures, and Rhodamine 123 Binding in Two Marine Dinoflagellates Cultured in the Presence of Parathion

Parathion, an organophosphorus insecticide, is highly toxic to the two free-living marine dinoflagellates Prorocentrum micans Ehrenberg (autotrophic) and Crypthecodinium cohnii Biechler (heterotrophic). To study its non-antiacetylcholinesterase action we assessed its effect on the mitochondrial system, as shown by changes in intracellular ATP concentration and in rhodamine 123 fluorescence evaluated by image analysis. The technique of image analysis permits direct assessment of changes in the overall activity of mitochondria in living cells. Mitochondrial structures were also examined in the electron microscope. The three methods of investigation yielded complementary results. In P. micans , parathion noticeably altered mitochondria but did not significantly alter ATP concentrations. In C. cohnii , however, mitochondrial disturbance was slight, whereas ATP increased greatly. We think, therefore, that parathion has different effects on mitochondria in the two organisms, and in particular that it increases mitochondrial activity in C. cohnii .     

Communicative interaction of myosins along an actin filament in the presence of ATP

Myosin molecules contacting an actin filament in the presence of ATP were found to regulate the filamental fluctuations due to ATP hydrolysis in a communicative manner along the filament. As an evidence of the occurrence of the communication, ATP-activated fluctuating displacements of the filament in the direction perpendicular to its longitudinal axis were identified to propagate at a finite velocity not less than about 0.2 μm/s unidirectionally along the filament.     

Differential gene expression during apoptosis induced by a serum factor: Role of mitochondrial F<Subscript>0</Subscript>-F<Subscript>1</Subscript> ATP synthase complex

The number of genes that are up regulated or down regulated during apoptosis is large and still increasing. In an attempt to characterize differential gene expression during serum factor induced apoptosis in AK-5 cells (a rat histiocytoma), we found subunit 6 and subunit 8 of the transmembrane proton channel and subunit alpha of the catalytic core of the mitochondrial F₀-F₁ ATP synthase complex to be up regulated during apoptosis. The increase in the expression levels of these subunits was concomitant with a transient increase in the intracellular ATP levels, suggesting that the increase in cellular ATP content is a result of the increase in the expression of ATP synthase subunits' gene and de novo protein synthesis. Depleting the cellular ATP levels with oligomycin inhibited apoptosis significantly, pointing to the requirement of ATP during apoptosis. Caspase 1 and caspase 3 activity and the loss of mitochondrial membrane potential were also inhibited by oligomycin during apoptosis in these cells, suggesting that the oligomycin induced inhibition of apoptosis could be due to inhibition of caspase activity and inhibition of mitochondrial depolarization. However, cytochrome C release during apoptosis was found to be completely independent of intracellular ATP content. Besides the ATP synthase complex genes, other mitochondrial genes like cytochrome C oxidase subunit II and III also showed elevated levels of expression during apoptosis. This kind of a mitochondrial gene expression profile suggests that in AK-5 cells, these genes are upregulated in a time-linked manner to ensure sufficient intracellular ATP levels and an efficient functioning of the mitochondrial respiratory chain for successful completion of the apoptotic pathway.     

HtrA2 deficiency causes mitochondrial uncoupling through the F1F0-ATP synthase and consequent ATP depletion

Loss of the mitochondrial protease HtrA2 (Omi) in mice leads to mitochondrial dysfunction, neurodegeneration and premature death, but the mechanism underlying this pathology remains unclear. Using primary cultures from wild-type and HtrA2-knockout mice, we find that HtrA2 deficiency significantly reduces mitochondrial membrane potential in a range of cell types. This depolarisation was found to result from mitochondrial uncoupling, as mitochondrial respiration was increased in HtrA2-deficient cells and respiratory control ratio was dramatically reduced. HtrA2-knockout cells exhibit increased proton translocation through the ATP synthase, in combination with decreased ATP production and truncation of the F1 α-subunit, suggesting the ATP synthase as the source of the proton leak. Uncoupling in the HtrA2-deficient mice is accompanied by altered breathing pattern and, on a cellular level, ATP depletion and vulnerability to chemical ischaemia. We propose that this vulnerability may ultimately cause the neurodegeneration observed in these mice.     

The Role of Mitochondrially Derived ATP in Synaptic Vesicle Recycling

Synaptic mitochondria are thought to be critical in supporting neuronal energy requirements at the synapse, and bioenergetic failure at the synapse may impair neural transmission and contribute to neurodegeneration. However, little is known about the energy requirements of synaptic vesicle release or whether these energy requirements go unmet in disease, primarily due to a lack of appropriate tools and sensitive assays. To determine the dependence of synaptic vesicle cycling on mitochondrially derived ATP levels, we developed two complementary assays sensitive to mitochondrially derived ATP in individual, living hippocampal boutons. The first is a functional assay for mitochondrially derived ATP that uses the extent of synaptic vesicle cycling as a surrogate for ATP level. The second uses ATP FRET sensors to directly measure ATP at the synapse. Using these assays, we show that endocytosis has high ATP requirements and that vesicle reacidification and exocytosis require comparatively little energy. We then show that to meet these energy needs, mitochondrially derived ATP is rapidly dispersed in axons, thereby maintaining near normal levels of ATP even in boutons lacking mitochondria. As a result, the capacity for synaptic vesicle cycling is similar in boutons without mitochondria as in those with mitochondria. Finally, we show that loss of a key respiratory subunit implicated in Leigh disease markedly decreases mitochondrially derived ATP levels in axons, thus inhibiting synaptic vesicle cycling. This proves that mitochondria-based energy failure can occur and be detected in individual neurons that have a genetic mitochondrial defect.     

SLP‐2 is required for stress‐induced mitochondrial hyperfusion

Mitochondria are dynamic organelles, the morphology of which results from an equilibrium between two opposing processes, fusion and fission. Mitochondrial fusion relies on dynamin‐related GTPases, the mitofusins (MFN1 and 2) in the outer mitochondrial membrane and OPA1 (optic atrophy 1) in the inner mitochondrial membrane. Apart from a role in the maintenance of mitochondrial DNA, little is known about the physiological role of mitochondrial fusion. Here we report that mitochondria hyperfuse and form a highly interconnected network in cells exposed to selective stresses. This process precedes mitochondrial fission when it is triggered by apoptotic stimuli such as UV irradiation or actinomycin D. Stress‐induced mitochondrial hyperfusion (SIMH) is independent of MFN2, BAX/BAK, and prohibitins, but requires L‐OPA1, MFN1, and the mitochondrial inner membrane protein SLP‐2. In the absence of SLP‐2, L‐OPA1 is lost and SIMH is prevented. SIMH is accompanied by increased mitochondrial ATP production and represents a novel adaptive pro‐survival response against stress.