《Cell》11月02 highlights中英文摘要

tophelix1114

Targeted Deletion of AIF Decreases Mitochondrial Oxidative Phosphorylation and Protects from Obesity and Diabetes

靶向性删除AIF能降低线粒体氧化磷酸化水平并防治肥胖和糖尿病

Type-2 diabetes results from the development of insulin resistance and a concomitant impairment of insulin secretion. Recent studies place altered mitochondrial oxidative phosphorylation (OxPhos) as an underlying genetic element of insulin resistance. However, the causative or compensatory nature of these OxPhos changes has yet to be proven. Here, we show that muscle- and liver-specific AIF ablation in mice initiates a pattern of OxPhos deficiency closely mimicking that of human insulin resistance, and contrary to current expectations, results in increased glucose tolerance, reduced fat mass, and increased insulin sensitivity. These results are maintained upon high-fat feeding and in both genetic mosaic and ubiquitous OxPhos-deficient mutants. Importantly, the effects of AIF on glucose metabolism are acutely inducible and reversible. These findings establish that tissue-specific as well as global OxPhos defects in mice can counteract the development of insulin resistance, diabetes, and obesity.

2型糖尿病是由胰岛素分泌功能损伤并发胰岛素抵抗引起的。最近的一些研究认为线粒体氧化磷酸化（OxPhos）异常是胰岛素抵抗产生的遗传学原因。然而，这些氧化磷酸化异常的原因仍然需要阐明。本文中，我们证明小鼠肌肉和肝脏中特异AIF消融能够导致氧化磷酸化水平降低，这与当前的预期相反，但类似人类胰岛素抵抗：葡萄糖水平上升，脂肪降解而且胰岛素敏感性增高。当对遗传花叶及泛素化氧化磷酸化缺陷的突变株进行高脂肪喂养时，出现了上述结果。重要的是， AIF对葡萄糖代谢的影响可以精确诱导并可逆发生。这些发现说明小鼠中组织特异性缺陷（例如氧化磷酸化水平）能阻碍胰岛素抵抗，肥胖及糖尿病的发生。


Anti-PlGF Inhibits Growth of VEGF(R)-Inhibitor-Resistant Tumors without Affecting Healthy Vessels

抗胎盘生长因子（Anti-PlGF）能抑制血管内皮生长因子（VEGF（R））抑制剂耐药肿瘤的生长而不损害健康血管

Novel antiangiogenic strategies with complementary mechanisms are needed to maximize efficacy and minimize resistance to current angiogenesis inhibitors. We explored the therapeutic potential and mechanisms of αPlGF, an antibody against placental growth factor (PlGF), a VEGF homolog, which regulates the angiogenic switch in disease, but not in health. αPlGF inhibited growth and metastasis of various tumors, including those resistant to VEGF(R) inhibitors (VEGFRIs), and enhanced the efficacy of chemotherapy and VEGFRIs. αPlGF inhibited angiogenesis, lymphangiogenesis, and tumor cell motility. Distinct from VEGFRIs, αPlGF prevented infiltration of angiogenic macrophages and severe tumor hypoxia, and thus, did not switch on the angiogenic rescue program responsible for resistance to VEGFRIs. Moreover, it did not cause or enhance VEGFRI-related side effects. The efficacy and safety of αPlGF, its pleiotropic and complementary mechanism to VEGFRIs, and the negligible induction of an angiogenic rescue program suggest that αPlGF may constitute a novel approach for cancer treatment.

当前依赖互补机制的抗血管生成新疗法要求最大限度地增强血管生成抑制因子的效果并最小限度地发生耐药性。我们发现了αPlGF的作用机制及治疗潜力。 aPIGF，又称抗胎盘生长因子，和血管内皮生长因子VEGFR同源，参与调控发病部位的血管生成，而不影响健康组织。αPlGF抑制多种肿瘤的生长代谢，包括那些对VEGFR抑制剂产生抵抗的肿瘤，并能增强VEGF抑制剂和化学疗法的效果。αPlGF抑制血管生成，淋巴管生成，以及肿瘤细胞转移。和 VEGFR抑制剂不同的是，αPlGF阻碍巨噬细胞渗透并参与造成肿瘤缺氧，而且，不促发耐VEGFR抑制剂的血管生成援救程序。此外，不会引起或增强 VEGFR抑制剂相关的副作用。αPlGF有着多效性，与VEGFR抑制剂的互补机制，轻微到忽略的援救反应，都说明αPlGF也许开辟了癌症治疗的新途径。


SUMO-Specific Protease 1 Is Essential for Stabilization of HIF1α during Hypoxia

SUMO特异的蛋白酶1在组织缺氧时对于维持HIF1a的稳定有着重要作用

SUMOylation is a dynamic process, catalyzed by SUMO-specific ligases and reversed by Sentrin/SUMO-specific proteases (SENPs). The physiologic consequences of SUMOylation and deSUMOylation are not fully understood. Here we investigate the phenotypes of mice lacking SENP1 and find that SENP1?/? embryos show severe fetal anemia stemming from deficient erythropoietin (Epo) production and die midgestation. We determine that SENP1 controls Epo production by regulating the stability of hypoxia-inducible factor 1α (HIF1α) during hypoxia. Hypoxia induces SUMOylation of HIF1α, which promotes its binding to a ubiquitin ligase, von Hippel-Lindau (VHL) protein, through a proline hydroxylation-independent mechanism, leading to its ubiquitination and degradation. In SENP1?/? MEFs, hypoxia-induced
transcription of HIF1α-dependent genes such as vascular endothelial growth factor (VEGF) and glucose transporter 1 (Glut-1) is markedly reduced. These results show that SENP1 plays a key role in the regulation of the hypoxic response through regulation of HIF1α stability and that SUMOylation can serve as a direct signal for ubiquitin-dependent degradation.

由SUMO特异的连接酶催化的SUMO化修饰是一种动力学过程，Sentrin/SUMO专一的蛋白酶（SENPs）催化逆反应。SUMO化修饰和去修饰的生理学后果目前仍然未知。本文我们研究了SENP1缺陷小鼠的显型，发现SENP1缺陷的晶胚中由于促红细胞生成素Epo缺乏引发胎型贫血症，妊娠期死亡。我们认为SENP1通过调控氧缺乏诱导因子1a的稳定性控制Epo产量。HIF1a的SUMO化修饰促进其Hippel-Lindau（VHL）蛋白通过依赖脯氨酸的羟化机制与泛素化连接酶结合，进而促发泛素化和降解。在SENP1?/? MEFs，氧缺乏诱导HIF1a依赖的基因发生转录，这些基因包括血管内皮生长因子VEGF，葡糖转运体1（Glut—1）明显减少。这些结果表明 SENP1通过调节HIF1a的稳定性，在氧缺乏反应的调控方面起着重要作用，而SUMO化修饰可以作为直接信号介导泛素依赖的降解。


Plasmodium Circumsporozoite Protein Promotes the Development of the Liver Stages of the Parasite

变形虫环子孢子蛋白促发肝脏中寄生虫感染

The liver stages of malaria are clinically silent but have a central role in the Plasmodium life cycle. Liver stages of the parasite containing thousands of merozoites grow inside hepatocytes for several days without triggering an inflammatory response. We show here that Plasmodium uses a PEXEL/VTS motif to introduce the circumsporozoite (CS) protein into the hepatocyte cytoplasm and a nuclear localization signal (NLS) to enter its nucleus. CS outcompetes NFκB nuclear import, thus downregulating the expression of many genes controlled by NFκB, including those involved in inflammation. CS also influences the expression of over one thousand host genes involved in diverse metabolic processes to create a favorable niche for the parasite growth. The presence of CS in the hepatocyte enhances parasite growth of the liver stages in vitro and in vivo. These findings have far reaching implications for drug and vaccine development against the liver stages of the malaria parasite.

疟原虫在肝脏中的感染在临床上的研究还没有相关记载，但它在疟原虫生活周期里占据着中心地位。肝脏中寄生虫感染使得感染后数日，肝实质细胞中产生成千上万裂殖子而不触发炎症反应。本文中我们发现疟原虫使用PEXEL/VTS基序介导环化孢子蛋白CS进入肝实质细胞质并促使核定位信号（NLS）进入细胞核中。CS竞争NFκB核转运，因此下调了许多由NFκB调控的基因表达水平，比如参与炎症反应的基因。CS同样影响着宿主中超过一千种参与不同代谢途径的基因的表达，为寄生虫的生长提供一个有利环境。肝实质细胞中的CS在体外和体内实验中都表明能增强已感染肝脏中寄生虫的生长。这些发现对于肝脏感染疟原寄生虫药物和疫苗的开发有深远意义。


Hydrodynamic Flow-Mediated Protein Sorting on the Cell Surface of Trypanosomes

流体力介导的蛋白在锥体虫细胞表面发生分拣

The unicellular parasite Trypanosoma brucei rapidly removes host-derived immunoglobulin (Ig) from its cell surface, which is dominated by a single type of glycosylphosphatidylinositol-anchored variant surface glycoprotein (VSG). We have determined the mechanism of antibody clearance and found that Ig-VSG immune complexes are passively sorted to the posterior cell pole, where they are endocytosed. The backward movement of immune complexes requires forward cellular motility but is independent of endocytosis and of actin function. We suggest that the hydrodynamic flow acting on swimming trypanosomes causes directional movement of Ig-VSG immune complexes in the plane of the plasma membrane, that is, immunoglobulins attached to VSG function as molecular sails. Protein sorting by hydrodynamic forces helps to protect trypanosomes against complement-mediated immune destruction in culture and possibly in infected mammals but likewise may be of functional significance at the surface of other cell types such as epithelial cells lining blood vessels.

单细胞寄生虫锥体虫brucei能快速把宿主衍生的免疫球蛋白从细胞表面移开，这是由单型糖肌醇磷脂连接的多表面糖蛋白调控的。我们验证了抗体清除机制并发现Ig-VSG免疫复合物被分拣形成细胞极，而后被吞噬。免疫复合物向后的运动需要相反方向的推动力，但是吞噬作用是单独发生的，同样肌动蛋白也是如此。我们认为锥体虫泳动的流体力间接引起Ig-VSG免疫球蛋白在质膜平面上的运动，也就是说，免疫球蛋白相当于VSG功能上的分子“帆”。培养时或感染的哺乳动物体内，很可能流体力引起的蛋白分拣有助于锥体虫逃避补体介导的免疫杀灭，类似的情况也可能存在于其他类型细胞表面（如上皮细胞系的血管细胞）。


Functional Specificity of a Hox Protein Mediated by the Recognition of Minor Groove Structure

Hox蛋白通过识别小沟结构介导功能特异性

control of gene expression. Members of the Hox family of transcription factors bind DNA by making nearly identical major groove contacts via the recognition helices of their homeodomains. In vivo specificity, however, often depends on extended and unstructured regions that link Hox homeodomains to a DNA-bound cofactor, Extradenticle (Exd). Using a combination of structure determination, computational analysis, and in vitro and in vivo assays, we show that Hox proteins recognize specific Hox-Exd binding sites via residues located in these extended regions that insert into the minor groove but only when presented with the correct DNA sequence. Our results suggest that these residues, which are conserved in a paralog-specific manner, confer specificity by recognizing a sequence-dependent DNA structure instead of directly reading a specific DNA sequence.

基因表达的控制手，转录因子中的Hox家族成员通过它们同源结构域的螺旋结构识别DNA大沟并结合。然而，在特异的体内实验中，连接Hox和DNA结合辅助因子的却常常是一些延伸和无结构的Exd区域。通过结构测定重组，计算机分析，体内体外实验，我们证明Hox蛋白通过这些残留的只插入正确配对DNA小沟的延伸区域识别特异Hox-Exd结合位点。我们的实验结果显示这些残留物通过特异旁系同源方式识别，即通过依赖序列的DNA结构而不是直接识别特异 DNA序列。


Functional Specificity among Ribosomal Proteins Regulates Gene Expression

核糖体蛋白功能特异调控基因表达

Duplicated genes escape gene loss by conferring a dosage benefit or evolving diverged functions. The yeast Saccharomyces cerevisiae contains many duplicated genes encoding ribosomal proteins. Prior studies have suggested that these duplicated proteins are functionally redundant and affect cellular processes in proportion to their expression. In contrast, through studies of ASH1 mRNA in yeast, we demonstrate paralog-specific requirements for the translation of localized mRNAs. Intriguingly, these paralog-specific effects are limited to a distinct subset of duplicated ribosomal proteins. Moreover, transcriptional and phenotypic profiling of cells lacking specific ribosomal proteins reveals differences between the functional roles of ribosomal protein paralogs that extend beyond effects on mRNA localization. Finally, we show that ribosomal protein paralogs exhibit differential requirements for assembly and localization. Together, our data indicate complex specialization of ribosomal proteins for specific cellular processes and support the existence of a ribosomal code.

重叠基因通过剂量效益或功能分化防止基因缺失。酿酒酵母含有许多编码核糖体蛋白的重叠基因。先前的研究认为这些重复蛋白没有功能，其表达能影响细胞行为。相反，通过对酵母ASH1 mRNA的研究，我们发现旁系同源体专一性要求定位mRNA的翻译。有趣的是，这些旁系同源体专一性受到不同核糖体重叠蛋白亚基的影响。此外，旁系同源核糖体蛋白显示不同功能，显示特异缺失不同核糖体蛋白细胞的转录和表型都不同，说明其功能不只局限于对mRNA定位。最后，我们证明旁系同源核糖体蛋白显示出不同的装配和定位功能。总之，我们的研究说明核糖体蛋白复杂的特异化是为了满足不同的细胞功能，并预示有一套核糖体密码的存在。



Simian Virus 40 Depends on ER Protein Folding and Quality Control Factors for Entry into Host Cells

猿病毒40依赖ER蛋白折叠和质量控制因子介导进入宿主细胞

Cell entry of Simian Virus 40 (SV40) involves caveolar/lipid raft-mediated endocytosis, vesicular transport to the endoplasmic reticulum (ER), translocation into the cytosol, and import into the nucleus. We analyzed the effects of ER-associated processes and factors on infection and on isolated viruses and found that SV40 makes use of the thiol-disulfide oxidoreductases, ERp57 and PDI, as well as the retrotranslocation proteins Derlin-1 and Sel1L. ERp57 isomerizes specific interchain disulfides connecting the major capsid protein, VP1, to a crosslinked network of neighbors, thus uncoupling about 12 of 72 VP1 pentamers. Cryo-electron tomography indicated that loss of interchain disulfides coupled with calcium depletion induces selective dissociation of the 12 vertex pentamers, a step likely to mimic uncoating of the virus in the cytosol. Thus, the virus utilizes the protein folding machinery for initial uncoating before exploiting the ER-associated degradation machinery presumably to escape from the ER lumen into the cytosol.

猿病毒40（SV40）依靠胞膜窖/脂筏介导的内吞作用进入宿主细胞，而后由小泡转运至内质网（ER），经细胞溶胶，进入细胞核。通过分析感染和分离的病毒的ER相关行为和因子，我们发现SV40利用巯基—二硫键氧化还原酶ERp57和PDI以及逆转运蛋白Derlin-1和Sel1L。ERp57能使特异的链键二硫键发生异构化，使主要衣壳蛋白VP1与邻近的蛋白发生网络交联，从而使72个VP1五聚体中12个发生解耦连作用。低温电子断层扫描术显示钙消耗与链间二硫键耦连作用的解除，诱导顶部12个五聚体发生选择性解聚，与病毒在细胞溶胶中脱壳的情况类似。因此，病毒在使用ER相关的降解机制从ER腔 “逃”到细胞溶胶之前，可能利用蛋白质折叠机制实现最初脱壳。


Sigma-1 Receptor Chaperones at the ER- Mitochondrion Interface Regulate Ca2+ Signaling and Cell Survival

ER-线粒体分界面上的Sigma-1受体伴侣调控钙离子信号通路与细胞生存

Communication between the endoplasmic reticulum (ER) and mitochondrion is important for bioenergetics and cellular survival. The ER supplies Ca2+ directly to mitochondria via inositol 1,4,5-trisphosphate receptors (IP3Rs) at close contacts between the two organelles referred to as mitochondrion-associated ER membrane (MAM). We found here that the ER protein sigma-1 receptor (Sig-1R), which is implicated in neuroprotection, carcinogenesis, and neuroplasticity, is a Ca2+-sensitive and ligand-operated receptor chaperone at MAM. Normally, Sig-1Rs form a complex at MAM with another chaperone, BiP. Upon ER Ca2+ depletion or via ligand stimulation, Sig-1Rs dissociate from BiP, leading to a prolonged Ca2+ signaling into mitochondria via IP3Rs. Sig-1Rs can translocate under chronic ER stress. Increasing Sig-1Rs in cells counteracts ER stress response, whereas decreasing them enhances apoptosis. These results reveal that the orchestrated ER chaperone machinery at MAM, by sensing ER Ca2+ concentrations, regulates ER-mitochondrial interorganellar Ca2+ signaling and cell survival.

内质网ER和线粒体之间的作用对于生物能和细胞生存至关重要。ER通过1，4，5-三磷酸肌醇IP3R直接为线粒体提供钙离子，是由线粒体相关ER膜 MAM在两种细胞器之间发生“亲密接触”实现的。我们发现和神经保护，癌症，神经可塑性相关的ER蛋白sigma-1受体（Sig-1R）
，是MAM上一种钙离子敏感的配体操作的受体伴侣。通常，Sig-1Rs在MAM上和另一种叫做BiP的伴侣形成复合物。在ER上，钙离子消耗或配体刺激，引起Sig-1Rs与BiP解聚，进而通过IP3Rs传递钙离子信号至线粒体。Sig-1Rs能在长时间的ER压力下发生移动。增加细胞的Sig- 1Rs能缓和ER的压力反应，相反，减少细胞的Sig-1Rs能增强凋亡作用。这些结果说明MAM上有序的ER伴侣分子通过感应ER的钙离子浓度，调控 ER-线粒体之间钙离子信号通讯和细胞生存。


Allosteric Activation of DegS, a Stress Sensor PDZ Protease

DegS别构化激活，PDZ蛋白酶的压力感受器

Regulated intramembrane proteolysis is a method for transducing signals between cellular compartments. When protein folding is compromised in the periplasm of E. coli, the C termini of outer-membrane proteins (OMPs) bind to the PDZ domains of the trimeric DegS protease and activate cleavage of RseA, a transmembrane transcriptional regulator. We show here that DegS is an allosteric enzyme. OMP binding shifts the equilibrium from a nonfunctional state, in which the active sites are unreactive, to the functional proteolytic conformation. Crystallographic, biochemical, and mutagenic experiments show that the unliganded PDZ domains are inhibitory and suggest that OMP binding per se is sufficient to stabilize the relaxed conformation and activate DegS. OMP-induced activation and RseA binding are both positively cooperative, allowing switch-like behavior of the OMP-DegS-RseA system. Residues involved in the DegS allosteric switch are conserved in the DegP/HtrA and HtrA2/Omi families, suggesting that many PDZ proteases use a common mechanism of allosteric activation.

调节膜内蛋白水解作用是细胞器之间信号转导的一种方式。当大肠杆菌E.coli周质中蛋白折叠发生阻碍，外膜蛋白OMPs的C端与三聚体DegS蛋白酶的 PDZ区域发生结合，促使ResA裂解。ResA是一种跨膜的转录调控因子。本文中，我们证明了DegS是一种别构酶。OMP结合使得无功能态（即活性区域处于钝化状态）转变为活性的有水解蛋白功能的构形。检晶仪，生化和诱变实验表明未连接配体的PDZ区域处于抑制状态，这说明OMP的结合足够维持R态的稳定并激活DegS。OMP诱导的激活与RseA的结合协同发生，OMP-DegS-RseA系统在其中发挥了电闸的作用。DegS构像不发生转变的部分与DegP/HtrA和HtrA2/Omi家族保守，这表明许多PDZ蛋白酶的构像激活机制存在共同之处。


Dissecting Timing Variability in Yeast Meiosis

酵母减数分裂期长短多样性分析

Cell-to-cell variability in the timing of cell-fate changes can be advantageous for a population of single-celled organisms growing in a fluctuating environment. We study timing variability during meiosis in Saccharomyces cerevisiae, initiated upon nutritional
starvation. We use time-lapse fluorescence microscopy to measure the timing of meiotic events in single cells and find that the duration of meiosis is highly variable between cells. This variability is concentrated between the beginning of starvation and the onset of early meiosis genes. Cell-cycle variability and nutritional history have little effect on this timing variability. Rather, variation in the production rate of the meiotic master regulator Ime1 and its gradual increase over time govern this variability, and cell size effects are channeled through Ime1. These results tie phenotypic variability with expression dynamics of a transcriptional regulator and provide a general framework for the study of temporal developmental processes.

细胞时间的可变性导致细胞命运不同，这对于单细胞生物体在不利环境中生存有重要意义。基于营养饥饿，我们研究了酿酒酵母减数分裂期的时间变化。我们使用定时的荧光显微镜来检测单细胞中减数分裂事件的时间，发现不同细胞减数分裂期长短明显不同。在饥饿发生伊始，这种不同尤为集中，表现在早期基因。细胞周期变化以及营养史对于这种时间多样没有多大影响。更进一步说，减数分裂精确调控者Ime1产物的比例不同，并且随时间延长Ime1产物增多，导致多样性。细胞大小从而取决于Ime1。这些发现把表型的多样性和转录调控因子表达的动力学结合起来，为同等学科的发展提供了一个很好的适用框架。