线粒体质量控制失调与恶性肿瘤发生和发展相关性的研究进展

线粒体活性氧增多、线粒体DNA突变和拷贝数改变、Ca~(2+)超载、凋亡异常等功能障碍与肿瘤发生、生长、侵袭、转移密切相关.随着研究的逐渐深入,人们认识到线粒体是个动态的细胞器,在生理、病理因素刺激下,经线粒体融合/分裂、线粒体自噬、线粒体生物合成以及线粒体分子伴侣和线粒体未折叠蛋白反应的协同调控,在细胞器和分子水平达到对线粒体及其蛋白质的质量控制,限制和延缓功能受损线粒体的积累和过度增多,维持线粒体数量、形态、功能和蛋白质量的动态平衡,保证细胞正常生命活动的进行,使其更好地适应环境.若线粒体及其蛋白的稳态调节能力下降或失衡,会导致受损线粒体的积累并引发细胞内环境的紊乱,影响线粒体功能的正常发挥,从而诱导正常细胞的恶性转化.     

p62蛋白的分子功能及其在疾病中的研究进展

螯合体1(SQSTM1/p62)是一种选择性自噬接头蛋白,在清除待降解蛋白、维持细胞内蛋白质稳态中发挥重要的调控作用。p62蛋白具有多个功能结构域,介导与多种蛋白质发生相互作用进而精确调节特定的信号通路,从而将p62蛋白与氧化防御系统、炎症反应和营养感知等重要生命过程联系起来。研究表明p62的突变或者表达异常与多种疾病的发生发展过程密切相关,包括神经退行性疾病、肿瘤、感染性疾病、遗传性疾病以及慢性疾病等。本文综述了p62蛋白的结构特征、分子功能,并系统介绍其在蛋白质稳态和信号通路调控中的多种功能,总结了p62在疾病发生发展中的复杂性与多面性,以期为p62蛋白的功能与相关疾病研究提供参考。     

Mitofilin对线粒体功能和疾病发生的影响

Mitofilin是一种线粒体内膜蛋白,与多种线粒体蛋白相互作用,共同参与线粒体内膜嵴形态的维持、线粒体内蛋白质的转运过程等。干扰mitofilin~表达不仅引起线粒体结构的异常,而且明显抑制了线粒体功能的正常发挥。最近的研究表明,在多种疾病中mitonlin都异常表达,从而导致线粒体结构的完整性和功能的障碍,促进了疾病的发生发展。     

综述与专论: 线粒体未折叠蛋白反应调控线虫衰老研究进展

蛋白质稳态是生物细胞应对压力的核心。线粒体作为一种重要的细胞器,依赖复杂的蛋白质网络行使正常功能,因此蛋白质稳态对其十分重要。当生物体受到外界压力,产生了蛋白质稳态的改变,为了维持机体功能的正常运转,细胞会激活一种称为线粒体未折叠蛋白反应的转录应答机制,从而维持线粒体蛋白质稳态,恢复线粒体功能,以应对压力,保持机体健康。本文主要介绍了线粒体的特征,线粒体未折叠蛋白反应的概念,线虫中线粒体未折叠蛋白反应的信号转导机制,以及线粒体未折叠蛋白反应对线虫衰老的影响。     

线粒体蛋白质组及蛋白质量控制

线粒体是哺乳动物细胞内重要细胞器,不仅通过氧化磷酸化产生ATP为细胞提供能量,也参与调节钙离子稳态、活性氧(reactive oxygen species,ROS)的产生、细胞应激反应和细胞死亡等过程,其功能障碍不仅导致多种人类疾病的发生,而且也能降低动物卵母细胞质量和早期胚胎发育能力。大量证据表明,线粒体的功能依赖于线粒体蛋白质组完整性和稳态。基于此,该文综述了线粒体蛋白组、线粒体蛋白转运,聚焦蛋白酶、分子伴侣、线粒体囊泡、线粒体自噬和线粒体未折叠蛋白反应在帮助正确的蛋白质折叠,去除错误折叠或聚集的蛋白质和清除功能失调的线粒体方面的作用,为调控线粒体蛋白质量,从而维持线粒体健康、降低疾病发生提供理论依据。     

核糖体相关质量控制与核糖体自噬研究进展

细胞中蛋白质处于不断合成和降解的动态更新过程中,其稳态与细胞功能密切相关。细胞中存在多种蛋白质质量控制（protein quality control,PQC）机制来监测蛋白质合成和降解过程的异常,以确保蛋白质组的完整性和细胞适应性。核糖体是细胞内数量最多的细胞器,系细胞内蛋白质合成的主要场所。现已明确,核糖体相关质量控制（ribosome-associated quality control,RQC）与核糖体自噬能通过溶酶体依赖和非依赖途径调节细胞内核糖体数量及功能以维持蛋白质稳态,从而增强细胞在应激状态下的适应能力。RQC失调、核糖体自噬障碍则参与多种疾病的发生及发展过程,靶向RQC和核糖体自噬可能成为防治多种疾病的有效手段。本综述聚焦核糖体相关的PQC途径,并进一步讨论了它们在蛋白质稳态维持中的重要地位及其在人类疾病发生发展中的潜在作用。     

铜转运与肿瘤——铂耐药及靶向治疗北大核心CSCD

铜作为酪氨酸酶、铜蓝蛋白等多种酶的辅因子,在机体多种生理功能中发挥了重要作用,是维持人体正常功能的一种必需的微量元素。而铜转运系统,包括铜转运蛋白家族(CTR)、铜转运ATP合酶及相关分子伴侣等,在细胞的铜稳态中发挥了重要作用,继而与维持细胞的正常功能息息相关。在肿瘤研究中,目前发现铜转运系统会影响肿瘤对铂类药物的敏感性,针对铜转运的肿瘤靶向治疗也成为肿瘤研究的热点之一。     

蛋白酪氨酸磷酸酶SHP-2与疾病的相关性研究进展

蛋白酪氨酸磷酸酶家族由130多种蛋白酪氨酸磷酸酶组成,它们和蛋白质酪氨酸激酶家族一起调控蛋白质中酪氨酸残基的磷酸化以及去磷酸化的动态平衡,它们的活性直接决定细胞内蛋白质的磷酸化水平的高低。SHP-2是蛋白酪氨酸磷酸酶家族的一员,在各种细胞和组织中均有广泛的表达,参与多个信号传导通路,介导细胞的生长、分化、迁移、粘附及凋亡等。SHP-2的表达异常会导致多种疾病的产生,但是相关综述较少,同时未见文献报道其在胶质瘤中的作用,因此本文简要介绍SHP-2的结构、功能、信号传导,并阐述了SHP-2与常见疾病的关系。     

铜转运与肿瘤——铂耐药及靶向治疗

铜作为酪氨酸酶、铜蓝蛋白等多种酶的辅因子,在机体多种生理功能中发挥了重要作用,是维持人体正常功能的一种必需的微量元素。而铜转运系统,包括铜转运蛋白家族(CTR)、铜转运ATP合酶及相关分子伴侣等,在细胞的铜稳态中发挥了重要作用,继而与维持细胞的正常功能息息相关。在肿瘤研究中,目前发现铜转运系统会影响肿瘤对铂类药物的敏感性,针对铜转运的肿瘤靶向治疗也成为肿瘤研究的热点之一。     

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。     

Interrelation Between Protein Synthesis,Proteostasis and Life Span

The production of newly synthesized proteins is a key process of protein homeostasis that initiates the biosynthetic flux of proteins and thereby determines the composition, stability and functionality of the proteome. Protein synthesis is highly regulated on multiple levels to adapt the proteome to environmental and physiological challenges such as aging and proteotoxic conditions. Imbalances of protein folding conditions are sensed by the cell that then trigger a cascade of signaling pathways aiming to restore the protein folding equilibrium. One regulatory node to rebalance proteostasis upon stress is the control of protein synthesis itself. Translation is reduced as an immediate response to perturbations of the protein folding equilibrium that can be observed in the cytosol as well as in the organelles such as the endoplasmatic reticulum and mitochondria. As reduction of protein synthesis is linked to life span increase, the signaling pathways regu-lating protein synthesis might be putative targets for treatments of age-related diseases. Eukaryotic cells have evolved a complex system for protein synthesis regulation and this review will summarize cellular strategies to regulate mRNA translation upon stress and its impact on longevity.     

Protein homeostasis disorders of key enzymes of amino acids metabolism: mutation-induced protein kinetic destabilization and new therapeutic strategies

Many inborn errors of amino acids metabolism are caused by single point mutations affecting the ability of proteins to fold properly (i.e., protein homeostasis), thus leading to enzyme loss-of-function. Mutations may affect protein homeostasis by altering intrinsic physical properties of the polypeptide (folding thermodynamics, and rates of folding/unfolding/misfolding) as well as the interaction of partially folded states with elements of the protein homeostasis network (such as molecular chaperones and proteolytic machineries). Understanding these mutational effects on protein homeostasis is required to develop new therapeutic strategies aimed to target specific features of the mutant polypeptide. Here, I review recent work in three different diseases of protein homeostasis associated to inborn errors of amino acids metabolism: phenylketonuria, inherited homocystinuria and primary hyperoxaluria type I. These three different genetic disorders involve proteins operating in different cell organelles and displaying different structural complexities. Mutations often decrease protein kinetic stability of the native state (i.e., its half-life for irreversible denaturation), which can be studied using simple kinetic models amenable to biophysical and biochemical characterization. Natural ligands and pharmacological chaperones are shown to stabilize mutant enzymes, thus supporting their therapeutic application to overcome protein kinetic destabilization. The role of molecular chaperones in protein folding and misfolding is also discussed as well as their potential pharmacological modulation as promising new therapeutic approaches. Since current available treatments for these diseases are either burdening or only successful in a fraction of patients, alternative treatments must be considered covering studies from protein structure and biophysics to studies in animal models and patients.     

Enhanced stability of human prion proteins with two disulfide bridges

We compare the folding equilibrium of the globular domain of the human prion protein with two variants of this domain, for which an additional disulfide bond was introduced into the location where it is found in the naturally occurring doppel protein. We find that the unfolding transition midpoint of the variants is shifted toward higher denaturant concentration, indicating that the engineered disulfide bond significantly stabilizes the global protein structure. Our results further reveal that the two-disulfide variant proteins, while possessing the same global fold as the wild-type, display marked differences in their folding pathway-in particular, the absence of a characteristic alpha-helix to beta-sheet transition, which is a fundamental feature associated with misfolding of proteins into amyloid fibrils, especially in the context of prion diseases. These surprising characteristics of disulfide mutant prion proteins have important implications for the understanding of the generic aberrant processes leading to amyloid fibril formation and protein aggregation, as well as providing insight into possible therapeutic strategies.     

The threads that tie protein-folding diseases

From unicellular organisms to humans, cells have evolved elegant systems to facilitate careful folding of proteins and the maintenance of protein homeostasis. Key modulators of protein homeostasis include a large, conserved family of proteins known as molecular chaperones, which augment the folding of nascent polypeptides and temper adverse consequences of cellular stress. However, errors in protein folding can still occur, resulting in the accumulation of misfolded proteins that strain cellular quality-control systems. In some cases, misfolded proteins can be targeted for degradation by the proteasome or via autophagy. Nevertheless, protein misfolding is a feature of many complex, genetically and clinically pleiotropic diseases, including neurodegenerative disorders and cancer. In recent years, substantial progress has been made in unraveling the complexity of protein folding using model systems, and we are now closer to being able to diagnose and treat the growing number of protein-folding diseases. To showcase some of these important recent advances, and also to inspire discussion on approaches to tackle unanswered questions, Disease Models & Mechanisms (DMM) presents a special collection of reviews from researchers at the cutting-edge of the field.KEY WORDS: Chaperones, Neurodegeneration, Protein folding     

Roles of CHOP/GADD153 in endoplasmic reticulum stress

Endoplasmic reticulum (ER) is the site of synthesis and folding of secretory proteins. Perturbations of ER homeostasis affect protein folding and cause ER stress. ER can sense the stress and respond to it through translational attenuation, upregulation of the genes for ER chaperones and related proteins, and degradation of unfolded proteins by a quality-control system. However, when the ER function is severely impaired, the organelle elicits apoptotic signals. ER stress has been implicated in a variety of common diseases such as diabetes, ischemia and neurodegenerative disorders. One of the components of the ER stress-mediated apoptosis pathway is C/EBP homologous protein (CHOP), also known as growth arrest- and DNA damage-inducible gene 153 (GADD153). Here, we summarize the current understanding of the roles of CHOP/GADD153 in ER stress-mediated apoptosis and in diseases including diabetes, brain ischemia and neurodegenerative disease.     

Naturally occurring organic osmolytes: from cell physiology to disease prevention

Osmolytes are naturally occurring organic compounds, which represent different chemical classes including amino acids, methylamines, and polyols. By accumulating high concentrations of osmolytes, organisms adapt to perturbations that can cause structural changes in their cellular proteins. Osmolytes shift equilibrium toward natively-folded conformations by raising the free energy of the unfolded state. As osmolytes predominantly affect the protein backbone, the balance between osmolyte-backbone interactions and amino acid side chain-solvent interactions determines protein folding. Abnormal cell volume regulation significantly contributes to the pathophysiology of several disorders, and cells respond to these changes by importing, exporting, or synthesizing osmolytes to maintain volume homeostasis. In recent years, it has become quite evident that cells regulate many biological processes such as protein folding, protein disaggregation, and protein-protein interactions via accumulation of specific osmolytes. Many genetic diseases are attributed to the problems associated with protein misfolding/aggregation, and it has been shown that certain osmolytes can protect these proteins from misfolding. Thus, osmolytes can be utilized as therapeutic targets for such diseases. In this review article, we discuss the role of naturally occurring osmolytes in protein stability, underlying mechanisms, and their potential use as therapeutic molecules.     

Protein misfolding and retinal degeneration

The retina is a highly complex and specialized organ that performs preliminary analysis of visual information. Composed of highly metabolically active tissue, the retina requires a precise and well-balanced means of maintaining its functional activity during extended periods of time. Maintenance and regulation of a vast array of different structural and functional proteins is required for normal function of the retina. This process is referred to as protein homeostasis and involves a variety of activities, including protein synthesis, folding, transport, degradation, elimination, and recycling. Deregulation of any of these activities can lead to malfunctioning of the retina, from subtle subclinical signs to severe retinal degenerative diseases leading to blindness. Examples of retinal degenerative diseases caused by disruption of protein homeostasis include retinitis pigmentosa and Stargardt's disease. A detailed discussion of the role of disruption in protein homeostasis in these and other retinal diseases is presented, followed by examples of some existing and potential treatments.     

Predicting repeat protein folding kinetics from an experimentally determined folding energy landscape

The Notch ankyrin domain is a repeat protein whose folding has been characterized through equilibrium and kinetic measurements. In previous work, equilibrium folding free energies of truncated constructs were used to generate an experimentally determined folding energy landscape (Mello and Barrick, Proc Natl Acad Sci USA 2004;101:14102–14107). Here, this folding energy landscape is used to parameterize a kinetic model in which local transition probabilities between partly folded states are based on energy values from the landscape. The landscape‐based model correctly predicts highly diverse experimentally determined folding kinetics of the Notch ankyrin domain and sequence variants. These predictions include monophasic folding and biphasic unfolding, curvature in the unfolding limb of the chevron plot, population of a transient unfolding intermediate, relative folding rates of 19 variants spanning three orders of magnitude, and a change in the folding pathway that results from C‐terminal stabilization. These findings indicate that the folding pathway(s) of the Notch ankyrin domain are thermodynamically selected: the primary determinants of kinetic behavior can be simply deduced from the local stability of individual repeats.