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Mammalian PITPs at the Golgi and ER-Golgi Membrane Contact Sites 哺乳动物高尔基体和er -高尔基体膜接触部位的pitp
Pub Date : 2020-10-01 DOI: 10.1177/2515256420964170
S. Cockcroft, S. Lev
Phosphatidylinositol (PI)-transfer proteins (PITPs) have been long recognized as proteins that modulate phosphoinositide levels in membranes through their intrinsic PI/PC-exchange activity. Recent studies from flies and mammals suggest that certain PITPs bind phosphatidic acid (PA) and possess PI/PA-exchange activity. Phosphoinositides and PA play critical roles in cell signaling and membrane trafficking, and numerous biochemical, genetic and functional studies have shown that PITPs regulate cellular lipid metabolism, various signaling pathways and intracellular membrane transport events. In this mini-review, we discuss the function of mammalian PITPs at the Golgi and ER-Golgi membrane contact sites (MCS) and highlight DAG (Diacylglycerol) as a central hub of PITPs functions. We describe PITPs-associated phospho-signaling network at the ER-Golgi interface, and share our perspective on future studies related to PITPs at MCSs.
磷脂酰肌醇(PI)-转移蛋白(PITPs)一直被认为是通过其固有的PI/ pc交换活性来调节膜内磷酸肌醇水平的蛋白质。最近对果蝇和哺乳动物的研究表明,某些PITPs结合磷脂酸(PA)并具有PI/PA交换活性。磷酸肌苷和磷酸腺苷在细胞信号传导和细胞膜运输中起着至关重要的作用,大量的生化、遗传和功能研究表明,pitp调节细胞脂质代谢、各种信号通路和细胞膜内运输事件。在这篇综述中,我们讨论了哺乳动物的PITPs在高尔基体和er -高尔基膜接触位点(MCS)的功能,并强调DAG(二酰基甘油)是PITPs功能的中心枢纽。我们描述了er -高尔基界面上与PITPs相关的磷酸化信号网络,并分享了我们对mcs中PITPs相关的未来研究的看法。
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引用次数: 5
Married at Birth: Regulation of Cellular Fat Metabolism by ER–Lipid Droplet Crosstalk 出生时结婚:er -脂滴串扰对细胞脂肪代谢的调节
Pub Date : 2020-09-01 DOI: 10.1177/2515256420934671
Zhe Cao, H. Y. Mak
The endoplasmic reticulum (ER) is a hub that coordinates neutral lipid synthesis, storage, and export. To fulfill this role, the ER maintains close contact with lipid droplets (LDs), which are evolutionarily conserved organelles for the storage of neutral lipids. Decades of biochemical evidence points to fatty acid modification and neutral lipid synthesis in the ER. Conceptually, lipid export into extracellular space or lipid retention intracellularly require the subsequent remodeling of an ER membrane leaflet that faces the lumen or cytoplasm, respectively. This is because LDs and very-low-density lipoprotein particles are all structures surrounded by a phospholipid monolayer. While the export of neutral lipids via very-low-density lipoprotein production is well characterized, there has been increasing interest in the mechanisms that underlie neutral lipid retention in LDs. Structural determination, in vitro reconstitution, and localization of key proteins by advanced microscopy techniques collectively enrich models of ER-LD engagement. In this review, we consider current concepts on how LDs emerge from the ER in a directional manner and how sustained ER-LD contacts support LD expansion.
内质网(ER)是协调中性脂合成、储存和输出的枢纽。为了实现这一作用,内质网与脂滴(ld)保持密切接触,脂滴是用于储存中性脂质的进化上保守的细胞器。几十年的生物化学证据指出,脂肪酸修饰和中性脂合成在内质网。从概念上讲,脂质输出到细胞外空间或脂质保留在细胞内需要随后分别重塑面向管腔或细胞质的内质网膜小叶。这是因为ld和非常低密度的脂蛋白颗粒都是由磷脂单层包围的结构。虽然通过极低密度脂蛋白的生产输出中性脂已经有了很好的特征,但人们对脂肪肝中性脂潴留的机制越来越感兴趣。通过先进的显微镜技术进行结构测定、体外重构和关键蛋白的定位,共同丰富了ER-LD结合的模型。在这篇综述中,我们考虑了当前关于LD如何以定向方式从ER中出现以及持续的ER-LD接触如何支持LD扩展的概念。
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引用次数: 3
Peroxisomal-PEX5 Controls Fasting-Induced Lipolysis 过氧化物酶体- pex5控制禁食诱导的脂肪分解
Pub Date : 2020-09-01 DOI: 10.1177/2515256420960303
Ji Seul Han, K. H. Han, J. B. Kim
Lipid droplets (LDs) are dynamic subcellular organelles which play critical roles for lipid homeostasis upon change of nutritional state. Although several organelles such as mitochondria and peroxisomes are involved in lipid metabolism, physiological roles and mediators involved in the spatiotemporal regulation of these subcellular organelles for energy metabolism has largely remained elusive. Our recent study implicates the importance of peroxisomes in the translocation of lipases onto LDs upon fasting cues. Also, we found that peroxisomal protein PEX5 modulates PKA-induced lipolysis by escorting ATGL toward LDs. This is accompanied by KIFC3-mediated migration of peroxisomes, leading to the physical contact between peroxisomes and LDs. In adipocyte-specific PEX5-knockout mice, fasting induced lipolysis is attenuated due to defective ATGL recruitment onto LDs. These results show that PEX5 plays a pivotal role in PKA induced lipolysis that occurs upon nutritional deprivation. We further speculate that the contact between LDs and peroxisomes could facilitate lipid metabolism via exchange of lipid metabolites between the organelles in response to nutritional changes.
脂滴是一种动态的亚细胞器,在营养状态变化时对脂质稳态起着至关重要的作用。虽然线粒体和过氧化物酶体等细胞器参与脂质代谢,但这些亚细胞细胞器对能量代谢的时空调节的生理作用和介质在很大程度上仍然是难以捉摸的。我们最近的研究表明,在禁食提示下,过氧化物酶体在脂肪酶易位到ld上的重要性。此外,我们发现过氧化物酶体蛋白PEX5通过护送ATGL进入ld来调节ppa诱导的脂肪分解。这伴随着kifc3介导的过氧化物酶体迁移,导致过氧化物酶体和ld之间的物理接触。在脂肪细胞特异性pex5敲除小鼠中,由于ATGL在ld上的募集缺陷,禁食诱导的脂肪分解减弱。这些结果表明,PEX5在营养剥夺时PKA诱导的脂肪分解中起关键作用。我们进一步推测,lld和过氧化物酶体之间的接触可能通过在细胞器之间交换脂质代谢物来促进脂质代谢,以响应营养变化。
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引用次数: 0
Seipin-Mediated Contacts as Gatekeepers of Lipid Flux at the Endoplasmic Reticulum–Lipid Droplet Nexus sepin介导的接触作为内质网-脂滴关系中脂通量的守门人
Pub Date : 2020-09-01 DOI: 10.1177/2515256420945820
Veijo T. Salo, M. Hölttä-Vuori, E. Ikonen
Lipid droplets (LDs) are dynamic cellular hubs of lipid metabolism. While LDs contact a plethora of organelles, they have the most intimate relationship with the endoplasmic reticulum (ER). Indeed, LDs are initially assembled at specialized ER subdomains, and recent work has unraveled an increasing array of proteins regulating ER-LD contacts. Among these, seipin, a highly conserved lipodystrophy protein critical for LD growth and adipogenesis, deserves special attention. Here, we review recent insights into the role of seipin in LD biogenesis and as a regulator of ER-LD contacts. These studies have also highlighted the evolving concept of ER and LDs as a functional continuum for lipid partitioning and pinpointed a role for seipin at the ER-LD nexus in controlling lipid flux between these compartments.
脂滴(ld)是脂质代谢的动态细胞中枢。虽然ld与大量细胞器接触,但它们与内质网(ER)的关系最为密切。事实上,ld最初是在专门的内质网亚域组装的,最近的工作已经揭示了越来越多的调节ER- ld接触的蛋白质。其中,seipin是一种高度保守的脂肪营养不良蛋白,对LD生长和脂肪形成至关重要,值得特别关注。在这里,我们回顾了最近关于seipin在LD生物发生中的作用以及作为ER-LD接触的调节剂的见解。这些研究还强调了ER和ld作为脂质分配的功能连续体的不断发展的概念,并确定了sepin在ER- ld联系中控制这些区室之间的脂质通量的作用。
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引用次数: 12
ORP1L, ORP1S, and ORP2: Lipid Sensors and Transporters ORP1L, ORP1S和ORP2:脂质传感器和转运蛋白
Pub Date : 2020-09-01 DOI: 10.1177/2515256420956818
Y. Aw, Andrew J. Brown, Jia-Wei Wu, Hongyuan Yang
Lipid transfer proteins are crucial for intracellular cholesterol trafficking at sites of membrane contact. In the OSBP/ORPs (oxysterol binding protein and OSBP-related proteins) family of lipid transfer proteins, ORP1L, ORP1S and ORP2 play important roles in cholesterol transport. ORP1L is an endosome/lysosome-anchored cholesterol sensor which may also move cholesterol bidirectionally at the interface between the endoplasmic reticulum and the endosome/lysosome. ORP2 delivers cholesterol to the plasma membrane, driven by PI(4,5)P2 hydrolysis. ORP1S may also transport cholesterol to the plasma membrane, although it is unclear if phosphoinositides are involved. The source of cholesterol delivered to the plasma membrane by ORP1S and ORP2 remains unclear. This review summarises the roles of these proteins in maintaining cellular cholesterol homeostasis and in human disease.
脂质转移蛋白对细胞膜接触部位的细胞内胆固醇运输至关重要。在OSBP/ORPs(氧甾醇结合蛋白和OSBP相关蛋白)脂质转运蛋白家族中,ORP1L、ORP1S和ORP2在胆固醇转运中发挥重要作用。ORP1L是一种内核体/溶酶体锚定的胆固醇传感器,它也可以在内质网和内核体/溶酶体之间的界面双向移动胆固醇。ORP2通过PI(4,5)P2水解将胆固醇传递到质膜。ORP1S也可能将胆固醇运输到质膜,尽管尚不清楚是否涉及磷酸肌苷。通过ORP1S和ORP2传递到质膜的胆固醇来源尚不清楚。本文综述了这些蛋白在维持细胞胆固醇稳态和人类疾病中的作用。
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引用次数: 2
Sphingolipid Metabolism at the ER-Golgi Contact Zone and Its Impact on Membrane Trafficking 内质-高尔基接触区鞘脂代谢及其对膜运输的影响
Pub Date : 2020-09-01 DOI: 10.1177/2515256420959514
Asako Goto, Aya Mizuike, K. Hanada
Proteins and lipids represent the two major constituents of biological membranes. Different organelles have different lipid compositions, which may be crucial for the execution and control of various organelle-specific functions. The interorganellar transport of lipids is dominated by mechanisms that are distinct from the vesicular mechanisms that underlie the interorganellar transport of proteins. Lipid transfer proteins (LTPs) efficiently and accurately mediate the trafficking of membrane lipids at the interfaces between different organelles. In this review, which focuses on sphingolipids, we describe the coordinated synthesis and transfer of lipids that occur at the endoplasmic reticulum (ER)-Golgi apparatus contact zones and discuss the impacts of lipid metabolism on membrane trafficking from the trans-Golgi network (TGN).
蛋白质和脂质是构成生物膜的两大主要成分。不同的细胞器具有不同的脂质组成,这可能对各种细胞器特异性功能的执行和控制至关重要。脂质在细胞器间运输的主要机制不同于蛋白质在细胞器间运输基础上的囊泡机制。脂质转移蛋白(LTPs)在不同细胞器之间的界面上有效而准确地介导膜脂的运输。在这篇综述中,我们描述了发生在内质网(ER)-高尔基体接触区脂质的协调合成和转移,并讨论了脂质代谢对反式高尔基网络(TGN)膜运输的影响。
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引用次数: 9
Nucleus–Plasma Membrane Contact Sites Are Formed During Spermiogenesis in the Acoel Symsagittifera roscoffensis 精子发生过程中核-质膜接触点的形成
Pub Date : 2020-06-01 DOI: 10.1177/2515256420926354
M. Hayes, Anne Zakrzewski, T. Levine, M. Telford
Symsagittifera roscoffensis is a small marine worm found in the intertidal zone of sandy beaches around the European shores of the Atlantic. S. roscoffensis is a member of the Acoelomorpha, a group of flatworms formerly classified with the Platyhelminthes, but now recognized as Xenacoelomorpha, a separate phylum of disputed affinity. We have used electron microscopy to examine the process of spermiogenesis (the final stage of spermatogenesis) in S. roscoffensis, by which spermatids form highly elongated spermatozoa. Their nuclei are long and thread-like, running most of the cell’s length, and during the process, a pair of flagella are fully incorporated into the cell body. Two previously undescribed interorganelle contact sites form at different stages of spermiogenesis. Strikingly, there is an extensive nucleus–plasma membrane contact site. Golgi-derived granules containing electron-dense filaments line up along the spermatid plasma membrane, undergo a conformational change, and donate material that forms a perinuclear layer that cements this contact site. We also show in spermatids at an earlier stage that the same granules are associated with microtubules, presumably for traffic along the elongating cell. We identify a second spermiogenesis-specific contact site where sheaths engulfing each internalizing flagellum contact the nuclear envelope.
rosscoffensis是一种小型海洋蠕虫,发现于大西洋沿岸欧洲沙滩的潮间带。S. roscoffensis是无形门的一个成员,无形门是一组扁虫,以前被归类为扁形门,但现在被认为是异形门,一个有争议的亲缘关系的独立门。我们使用电子显微镜检查了s.s roscoffensis的精子发生过程(精子发生的最后阶段),在这个过程中精子形成高度细长的精子。它们的细胞核很长,呈线状,占据了细胞的大部分长度,在这个过程中,一对鞭毛被完全整合到细胞体中。两个先前描述过的细胞器间接触位点在精子发生的不同阶段形成。引人注目的是,有广泛的核-质膜接触部位。含有电子密集细丝的高尔基衍生颗粒沿着精子质膜排列,经历构象变化,并提供物质形成核周层,将接触部位粘合。我们还显示,在精子细胞的早期阶段,相同的颗粒与微管相关联,可能是为了沿着伸长的细胞运输。我们确定了第二个精子发生特异性接触点,在那里鞘吞噬每个内化鞭毛接触核膜。
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引用次数: 1
A Little AXER ABC: ATP, BiP, and Calcium Form a Triumvirate Orchestrating Energy Homeostasis of the Endoplasmic Reticulum 小AXER ABC: ATP, BiP和钙形成内质网协调能量稳态的三位一体
Pub Date : 2020-05-01 DOI: 10.1177/2515256420926795
R. Zimmermann, Sven Lang
Pioneering work in the 1990s started to address an interesting question. How is the main cellular energy source, adenosine triphosphate (ATP), imported into the mammalian endoplasmic reticulum (ER)? Despite its high-energy demand, large volume, and structural as well as functional complexity, the ER harbors no intricate system for ATP synthesis or regeneration. Although the original biochemical reconstitution approaches established hallmarks of the ATP transport into the ER including nucleotide selectivity, affinity, and antiport mode, the more recent live-cell imaging methods employing sensitive, localized molecular probes identified the elusive ATP/adenosine diphosphate (ADP) exchanger. According to its selectivity and localization, the identified SLC35B1 protein was rebranded AXER. Here, we discuss the identification and regulation of AXER plus the cytosolic partners (AMP-activated protein kinase, AMPK) and subcellular structures (mitochondrial–ER contact sites, MERCs) acting in concert with it to orchestrate energy homeostasis of the mammalian ER. Furthermore, we combine the two seemingly controversial regulatory mechanisms (lowER and CaATiER) in a unifying hypothesis.
20世纪90年代的开创性工作开始解决一个有趣的问题。主要的细胞能量来源三磷酸腺苷(ATP)是如何进入哺乳动物内质网(ER)的?尽管其高能量需求,体积大,结构和功能复杂,但内质网没有复杂的ATP合成或再生系统。虽然最初的生化重构方法建立了ATP转运到内质网的特征,包括核苷酸选择性、亲和性和反端口模式,但最近使用敏感的、局部分子探针的活细胞成像方法确定了难以捉摸的ATP/二磷酸腺苷(ADP)交换剂。根据SLC35B1蛋白的选择性和定位,将鉴定的SLC35B1蛋白重新命名为AXER。在这里,我们讨论了AXER的鉴定和调控,以及胞质伙伴(amp激活的蛋白激酶,AMPK)和亚细胞结构(线粒体-内质网接触位点,MERCs)与它协同作用,协调哺乳动物内质网的能量稳态。此外,我们将两种看似有争议的调节机制(lowER和CaATiER)结合在一个统一的假设中。
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引用次数: 6
Tethering Fat: Tethers in Lipid Droplet Contact Sites 栓系脂肪:脂滴接触部位的栓系
Pub Date : 2020-03-01 DOI: 10.1177/2515256420908142
Maria Bohnert
Lipid droplets (LDs) are central hubs in cellular lipid handling. They serve as lipid storage organelles and are involved in neutral lipid biosynthesis and breakdown as well as in the production of phospholipids and sterols. For communication with other organelles, LDs are heavily engaged in contact sites. The molecular basis of these structures is formed by proteins or protein complexes termed tethers, which attach partner organelles to the surface of LDs. Here, we describe the structural and functional characteristics of recently identified LD tethers. Intriguingly, these LD tethers have additional features, such as the structural capacity to form tri-organellar contacts, domains specialized for interorganellar bulk lipid transfer, and connections to specific lipid metabolism enzymes, which might collectively contribute to the key role of LDs in cellular lipid flux.
脂滴(ld)是细胞脂质处理的中心枢纽。它们作为脂质储存细胞器,参与中性脂质的生物合成和分解,以及磷脂和甾醇的产生。为了与其他细胞器进行通信,ld大量参与接触位点。这些结构的分子基础是由蛋白质或称为系链的蛋白质复合物形成的,它们将伴侣细胞器附着在ld表面。在这里,我们描述了最近发现的LD系绳的结构和功能特征。有趣的是,这些LD系链还有其他特征,如形成三细胞器接触的结构能力,专门用于细胞器间大量脂质转移的结构域,以及与特定脂质代谢酶的连接,这些可能共同有助于LD在细胞脂质通量中的关键作用。
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引用次数: 19
The Molecular Era of Lipid Droplets 脂滴的分子时代
Pub Date : 2020-03-01 DOI: 10.1177/2515256420912090
W. Henne
Lipid droplets (LDs) are the primary lipid-storage compartments of eukaryotes and feature a unique architecture distinct from membrane-bound organelles. Observed for over a century but initially ignored, recent cell biological, structural, and modeling studies provide new insights into how LDs are made, how they form connections with other organelles, and the roles they play in human physiology and disease. In this brief review, we highlight some key insights that helped define the LD and its roles in the cell. We also summarize new studies of molecular tethers that facilitate the LD interorganelle crosstalk and emerging technologies that provide key insights into the functions and organization of LDs.
脂滴(ld)是真核生物的主要脂质储存室,具有不同于膜结合细胞器的独特结构。观察了一个多世纪,但最初被忽视,最近的细胞生物学,结构和建模研究为ld如何形成,它们如何与其他细胞器形成连接以及它们在人体生理和疾病中的作用提供了新的见解。在这篇简短的回顾中,我们强调了一些有助于定义LD及其在细胞中的作用的关键见解。我们还总结了促进LD细胞器间串扰的分子链的新研究以及为LD的功能和组织提供关键见解的新兴技术。
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引用次数: 8
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