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https://www.readbyqxmd.com/read/28938119/the-pyrenoid-an-overlooked-organelle-comes-out-of-age
#1
Jean-David Rochaix
The pyrenoid is a membrane-less organelle that exists in various photosynthetic organisms, such as algae, and wherein most global CO2 fixation occurs. Two papers from the Jonikas lab in this issue of Cell provide new insights into the structure, protein composition, and dynamics of this important organelle.
September 21, 2017: Cell
https://www.readbyqxmd.com/read/28938114/the-eukaryotic-co2-concentrating-organelle-is-liquid-like-and-exhibits-dynamic-reorganization
#2
Elizabeth S Freeman Rosenzweig, Bin Xu, Luis Kuhn Cuellar, Antonio Martinez-Sanchez, Miroslava Schaffer, Mike Strauss, Heather N Cartwright, Pierre Ronceray, Jürgen M Plitzko, Friedrich Förster, Ned S Wingreen, Benjamin D Engel, Luke C M Mackinder, Martin C Jonikas
Approximately 30%-40% of global CO2 fixation occurs inside a non-membrane-bound organelle called the pyrenoid, which is found within the chloroplasts of most eukaryotic algae. The pyrenoid matrix is densely packed with the CO2-fixing enzyme Rubisco and is thought to be a crystalline or amorphous solid. Here, we show that the pyrenoid matrix of the unicellular alga Chlamydomonas reinhardtii is not crystalline but behaves as a liquid that dissolves and condenses during cell division. Furthermore, we show that new pyrenoids are formed both by fission and de novo assembly...
September 21, 2017: Cell
https://www.readbyqxmd.com/read/28938113/a-spatial-interactome-reveals-the-protein-organization-of-the-algal-co2-concentrating-mechanism
#3
Luke C M Mackinder, Chris Chen, Ryan D Leib, Weronika Patena, Sean R Blum, Matthew Rodman, Silvia Ramundo, Christopher M Adams, Martin C Jonikas
Approximately one-third of global CO2 fixation is performed by eukaryotic algae. Nearly all algae enhance their carbon assimilation by operating a CO2-concentrating mechanism (CCM) built around an organelle called the pyrenoid, whose protein composition is largely unknown. Here, we developed tools in the model alga Chlamydomonas reinhardtii to determine the localizations of 135 candidate CCM proteins and physical interactors of 38 of these proteins. Our data reveal the identity of 89 pyrenoid proteins, including Rubisco-interacting proteins, photosystem I assembly factor candidates, and inorganic carbon flux components...
September 21, 2017: Cell
https://www.readbyqxmd.com/read/28937869/effect-of-microtubule-disruption-on-dynamics-of-acidic-organelles-in-the-axons-of-primary-cultured-retinal-ganglion-cells
#4
Seiji Miyake, Yuji Takihara, Satoshi Yokota, Yoshihiro Takamura, Masaru Inatani
PURPOSE: Axonal transport is fundamental to autophagy in neuronal cells. To understand its biological significance in various conditions, it is necessary to monitor the process of autophagy. However, monitoring methods are often limited to static analyses, such as protein expression and histological observations. Autophagy has multistep process and is highly dynamic; therefore, additional techniques are necessary to study autophagy. In this study, we quantified the dynamics of autophagy-related organelle transport under conditions of dynamic instability and catastrophic disruption of microtubules using in vitro live imaging...
September 22, 2017: Current Eye Research
https://www.readbyqxmd.com/read/28937680/salinomycin-kills-cancer-stem-cells-by-sequestering-iron-in-lysosomes
#5
Trang Thi Mai, Ahmed Hamaï, Antje Hienzsch, Tatiana Cañeque, Sebastian Müller, Julien Wicinski, Olivier Cabaud, Christine Leroy, Amandine David, Verónica Acevedo, Akihide Ryo, Christophe Ginestier, Daniel Birnbaum, Emmanuelle Charafe-Jauffret, Patrice Codogno, Maryam Mehrpour, Raphaël Rodriguez
Cancer stem cells (CSCs) represent a subset of cells within tumours that exhibit self-renewal properties and the capacity to seed tumours. CSCs are typically refractory to conventional treatments and have been associated to metastasis and relapse. Salinomycin operates as a selective agent against CSCs through mechanisms that remain elusive. Here, we provide evidence that a synthetic derivative of salinomycin, which we named ironomycin (AM5), exhibits a more potent and selective activity against breast CSCs in vitro and in vivo, by accumulating and sequestering iron in lysosomes...
October 2017: Nature Chemistry
https://www.readbyqxmd.com/read/28937655/why-are-functional-amyloids-non-toxic-in-humans
#6
REVIEW
Matthew P Jackson, Eric W Hewitt
Amyloids were first identified in association with amyloidoses, human diseases in which proteins and peptides misfold into amyloid fibrils. Subsequent studies have identified an array of functional amyloid fibrils that perform physiological roles in humans. Given the potential for the production of toxic species in amyloid assembly reactions, it is remarkable that cells can produce these functional amyloids without suffering any obvious ill effect. Although the precise mechanisms are unclear, there are a number of ways in which amyloid toxicity may be prevented...
September 22, 2017: Biomolecules
https://www.readbyqxmd.com/read/28936802/significance-of-mitochondrial-protein-post-translational-modifications-in-pathophysiology-of-brain-injury
#7
Nina Klimova, Aaron Long, Tibor Kristian
Mitochondria are complex organelles that undergo constant fusion and fission in order to adapt to the ever-changing cellular environment. The fusion/fission proteins, localized in the inner and outer mitochondrial membrane, play critical roles under pathological conditions such as acute brain injury and neurodegenerative diseases. Post-translational modifications of these proteins tightly regulate their function and activity, ultimately impacting mitochondrial dynamics and their efficiency to generate ATP. The individual post-translational modifications that are known to affect mitochondrial dynamics include SUMOylation, ubiquitination, phosphorylation, S-nitrosylation, acetylation, O-linked N-acetyl-glucosamine glycosylation, ADP-ribosylation, and proteolytic cleavage...
September 21, 2017: Translational Stroke Research
https://www.readbyqxmd.com/read/28936658/analysis-of-peroxisome-biogenesis-in-pollen-by-confocal-microscopy-and-transmission-electron-microscopy
#8
Peng-Fei Jia, Hong-Ju Li, Wei-Cai Yang
Peroxisome is an essential single-membrane bound organelle in most eukaryotic cells and functions in diverse cellular processes. De novo formation, division, and turnover of peroxisomes contribute to its biogenesis, morphology, and population regulation. In plants, peroxisome plays multiple roles, including metabolism, development, and stress response. Defective peroxisome biogenesis and development retard plant growth, adaption, and reproduction. Through tracing the subcellular localization of fluorescent reporter tagged matrix protein of peroxisome, fluorescence microscopy is a reliable and fast way to detect peroxisome biogenesis...
2017: Methods in Molecular Biology
https://www.readbyqxmd.com/read/28936487/platelet-dense-granules-begin-to-selectively-accumulate-mepacrine-during-proplatelet-formation
#9
Hayley A Hanby, Jialing Bao, Ji-Yoon Noh, Danuta Jarocha, Mortimer Poncz, Mitchell J Weiss, Michael S Marks
Platelet dense granules (DGs) are storage organelles for calcium ions, small organic molecules such as ADP and serotonin, and larger polyphosphates that are secreted upon platelet stimulation to enhance platelet activation, adhesion, and stabilization at sites of vascular damage. DGs are thought to fully mature within megakaryocytes (MKs) prior to platelet formation. Here we challenge this notion by exploiting vital fluorescent dyes to distinguish mildly acidic DGs from highly acidic compartments by microscopy in platelets and MKs...
August 22, 2017: Blood Advances
https://www.readbyqxmd.com/read/28936467/peroxisome-motility-measurement-and-quantification-assay
#10
Jeremy Metz, Inês G Castro, Michael Schrader
Organelle movement, distribution and interaction contribute to the organisation of the eukaryotic cell. Peroxisomes are multifunctional organelles which contribute to cellular lipid metabolism and ROS homeostasis. They distribute uniformly in mammalian cells and move along microtubules via kinesin and dynein motors. Their metabolic cooperation with mitochondria and the endoplasmic reticulum (ER) is essential for the β-oxidation of fatty acids and the synthesis of myelin lipids and polyunsaturated fatty acids...
September 5, 2017: Bio-protocol
https://www.readbyqxmd.com/read/28935841/light-and-plastid-signals-regulate-different-sets-of-genes-in-the-albino-mutant-pap7-1
#11
Björn Grübler, Livia Merendino, Sven O Twardziok, Morgane Mininno, Guillaume Allorent, Fabien Chevalier, Monique Liebers, Robert Blanvillain, Klaus Mayer, Silva Lerbs-Mache, Stephane Ravanel, Thomas Pfannschmidt
Plants possessing dysfunctional plastids due to defects in pigment biosynthesis or translation are known to repress photosynthesis-associated nuclear genes (PhANGs) via retrograde signals from the disturbed organelles towards the nucleus. These signals are thought to be essential for proper biogenesis and function of the plastid. Mutants lacking plastid-encoded RNA polymerase-associated proteins (PAPs) display a genetic arrest in eoplast-chloroplast transition leading to an albino phenotype in the light. Retrograde signaling in these mutants, thus, could be expected to be similar as under conditions inducing plastid dysfunction...
September 21, 2017: Plant Physiology
https://www.readbyqxmd.com/read/28935754/pervasive-genome-wide-transcription-in-the-organelle-genomes-of-diverse-plastid-bearing-protists
#12
Matheus Sanitá Lima, David Roy Smith
Organelle genomes are among the most sequenced kinds of chromosome. This is largely because they are small and widely used in molecular studies, but also because next-generation sequencing (NGS) technologies made sequencing easier, faster, and cheaper. However, studies of organelle RNA have not kept pace with those of DNA, despite huge amounts of freely available eukaryotic RNA-sequencing (RNA-seq) data. Little is known about organelle transcription in non-model species, and most of the available eukaryotic RNA-seq data have not been mined for organelle transcripts...
September 21, 2017: G3: Genes—Genomes—Genetics
https://www.readbyqxmd.com/read/28935608/mechanical-coupling-of-microtubule-dependent-motor-teams-during-peroxisome-transport-in-drosophila-s2-cells
#13
María Cecilia De Rossi, Diana E Wetzler, Lorena Benseñor, María Emilia De Rossi, Mariela Sued, Daniela Rodríguez, Vladimir Gelfand, Luciana Bruno, Valeria Levi
BACKGROUND: Intracellular transport requires molecular motors that step along cytoskeletal filaments actively dragging cargoes through the crowded cytoplasm. Here, we explore the interplay of the opposed polarity motors kinesin-1 and cytoplasmic dynein during peroxisome transport along microtubules in Drosophila S2 cells. METHODS: We used single particle tracking with nanometer accuracy and millisecond time resolution to extract quantitative information on the bidirectional motion of organelles...
September 18, 2017: Biochimica et Biophysica Acta
https://www.readbyqxmd.com/read/28935577/human-pancreatic-acinar-cells-proteomic-characterization-physiologic-responses-and-organellar-disorders-in-ex-vivo-pancreatitis
#14
Aurelia Lugea, Richard T Waldron, Olga A Mareninova, Natalia Shalbueva, Nan Deng, Hsin-Yuan Su, Diane D Thomas, Elaina K Jones, Scott W Messenger, Jiayue Yang, Cheng Hu, Ilya Gukovsky, Zhenqiu Liu, Guy E Groblewski, Anna S Gukovskaya, Fred S Gorelick, Stephen J Pandol
Knowledge of the molecular mechanisms of acute pancreatitis is largely based on studies using rodents. To assess similar mechanisms in humans, we performed ex vivo pancreatitis studies in human acini isolated from cadaveric pancreata from organ donors. Since data on these human acinar preparations are sparse, we assessed their functional integrity, and cellular and organellar morphology using light, fluorescence and electron microscopy; and their proteome by liquid chromatography-tandem mass spectrometry (LC-MS/MS)...
September 18, 2017: American Journal of Pathology
https://www.readbyqxmd.com/read/28935166/mitochondrial-nanotunnels
#15
REVIEW
Amy E Vincent, Doug M Turnbull, Veronica Eisner, György Hajnóczky, Martin Picard
Insight into the regulation of complex physiological systems emerges from understanding how biological units communicate with each other. Recent findings show that mitochondria communicate at a distance with each other via nanotunnels, thin double-membrane protrusions that connect the matrices of non-adjacent mitochondria. Emerging evidence suggest that mitochondrial nanotunnels are generated by immobilized mitochondria and transport proteins. This review integrates data from the evolutionarily conserved structure and function of intercellular projections in bacteria with recent developments in mitochondrial imaging that permit nanotunnel visualization in eukaryotes...
September 18, 2017: Trends in Cell Biology
https://www.readbyqxmd.com/read/28934381/carboxysomes-metabolic-modules-for-co2-fixation
#16
Aiko Turmo, C Raul Gonzalez-Esquer, Cheryl A Kerfeld
The carboxysome is a bacterial microcompartment encapsulating the enzymes carbonic anhydrase and ribulose-1,5-bisphosphate carboxylase/oxygenase. As the site of CO2 fixation, it serves an essential role in the carbon dioxide concentrating mechanism of many chemoautotrophs and all cyanobacteria. Carboxysomes and other bacterial microcompartments self-assemble through specific protein-protein interactions that are typically mediated by conserved protein domains. In this review, we frame our current understanding of carboxysomes in the context of their component protein domains with their inherent function as the 'building blocks' of carboxysomes...
October 2, 2017: FEMS Microbiology Letters
https://www.readbyqxmd.com/read/28934226/pathological-alterations-in-liver-injury-following-congestive-heart-failure-induced-by-volume-overload-in-rats
#17
Mohammed Shaqura, Doaa M Mohamed, Noureddin B Aboryag, Lama Bedewi, Lukas Dehe, Sascha Treskatsch, Mehdi Shakibaei, Michael Schäfer, Shaaban A Mousa
Heart failure has emerged as a disease with significant public health implications. Following progression of heart failure, heart and liver dysfunction are frequently combined in hospitalized patients leading to increased morbidity and mortality. Here, we investigated the underlying pathological alterations in liver injury following heart failure. Heart failure was induced using a modified infrarenal aortocaval fistula (ACF) in male Wistar rats. Sham operated and ACF rats were compared for their morphometric and hemodynamic data, for histopathological and ultrastructural changes in the liver as well as differences in the expression of apoptotic factors...
2017: PloS One
https://www.readbyqxmd.com/read/28934149/oncolytic-reovirus-infection-is-facilitated-by-the-autophagic-machinery
#18
Vera Kemp, Iris J C Dautzenberg, Ronald W Limpens, Diana J M van den Wollenberg, Rob C Hoeben
Mammalian reovirus is a double-stranded RNA virus that selectively infects and lyses transformed cells, making it an attractive oncolytic agent. Despite clinical evidence for anti-tumor activity, its efficacy as a stand-alone therapy remains to be improved. The success of future trials can be greatly influenced by the identification and the regulation of the cellular pathways that are important for reovirus replication and oncolysis. Here, we demonstrate that reovirus induces autophagy in several cell lines, evident from the formation of Atg5-Atg12 complexes, microtubule-associated protein 1 light chain 3 (LC3) lipidation, p62 degradation, the appearance of acidic vesicular organelles, and LC3 puncta...
September 21, 2017: Viruses
https://www.readbyqxmd.com/read/28933989/role-of-pex5-ubiquitination-in-maintaining-peroxisome-dynamics-and-homeostasis
#19
Wei Wang, Suresh Subramani
Peroxisomes are essential and dynamic organelles that allow cells to rapidly adapt and cope with changing environments and/or physiological conditions by modulation of both peroxisome biogenesis and turnover. Peroxisome biogenesis involves the assembly of peroxisome membranes and the import of peroxisomal matrix proteins. The latter depends on the receptor, PEX5, which recognizes peroxisomal matrix proteins in the cytosol directly or indirectly, and transports them to the peroxisomal lumen. In this review, we discuss the role of PEX5 ubiquitination in both peroxisome biogenesis and turnover, specifically in PEX5 receptor recycling, stability and abundance, as well as its role in pexophagy (autophagic degradation of peroxisomes)...
September 21, 2017: Cell Cycle
https://www.readbyqxmd.com/read/28933638/autophagy-pathway-cellular-and-molecular-mechanisms
#20
Li Yu, Yang Chen, Sharon A Tooze
Macroautophagy/autophagy is an essential, conserved self-eating process that cells perform to allow degradation of intracellular components, including soluble proteins, aggregated proteins, organelles, macromolecular complexes, and foreign bodies. The process requires formation of a double-membrane structure containing the sequestered cytoplasmic material, the autophagosome, that ultimately fuses with the lysosome. This review will define this process and the cellular pathways required, from the formation of the double membrane to the fusion with lysosomes in molecular terms, and in particular highlight the recent progress in our understanding of this complex process...
September 21, 2017: Autophagy
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