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Membrane Sterols

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https://www.readbyqxmd.com/read/28922409/purification-and-characterisation-of-the-yeast-plasma-membrane-atp-binding-cassette-transporter-pdr11p
#1
Katrine Rude Laub, Magdalena Marek, Lyubomir Dimitrov Stanchev, Sara Abad Herrera, Tamara Kanashova, Adèle Bourmaud, Gunnar Dittmar, Thomas Günther Pomorski
The ATP binding cassette (ABC) transporters Pdr11p and its paralog Aus1p are expressed under anaerobic growth conditions at the plasma membrane of the yeast Saccharomyces cerevisiae and are required for sterol uptake. However, the precise mechanism by which these ABC transporters facilitate sterol movement is unknown. In this study, an overexpression and purification procedure was developed with the aim to characterise the Pdr11p transporter. Engineering of Pdr11p variants fused at the C terminus with green fluorescent protein (Pdr11p-GFP) and containing a FLAG tag at the N terminus facilitated expression analysis and one-step purification, respectively...
2017: PloS One
https://www.readbyqxmd.com/read/28912102/cholesterol-affects-the-interaction-between-an-ionic-liquid-and-phospholipid-vesicles-a-study-by-differential-scanning-calorimetry-and-nanoplasmonic-sensing
#2
Giacomo Russo, Joanna Witos, Antti H Rantamäki, Susanne K Wiedmer
The present work aims at studying the interactions between cholesterol-rich phosphatidylcholine-based lipid vesicles and trioctylmethylphosphonium acetate ([P8881][OAc]), a biomass dissolving ionic liquid (IL). The effect of cholesterol was assayed by using differential scanning calorimetry (DSC) and nanoplasmonic sensing (NPS) measurement techniques. Cholesterol-enriched dipalmitoyl-phosphatidylcholine vesicles were exposed to different concentrations of the IL, and the derived membrane perturbation was monitored by DSC...
September 11, 2017: Biochimica et Biophysica Acta
https://www.readbyqxmd.com/read/28910986/elimination-of-the-last-reactions-in-ergosterol-biosynthesis-alters-the-resistance-of-saccharomyces-cerevisiae-to-multiple-stresses
#3
Guodong Liu, Yun Chen, Nils J Færgeman, Jens Nielsen
The sterol composition of membranes is known to influence many phenotypes of yeast. However, a systematic study of the relationship between sterol composition and stress resistances has not been conducted. Here, we therefore constructed single or double gene deletion mutants of the last four enzymes in ergosterol biosynthesis in a prototrophic genetic background of Saccharomyces cerevisiae. Identification of the sterol composition of these mutants revealed a high flexibility of the sterol-processing steps instead of the previously proposed sequential conversion...
September 1, 2017: FEMS Yeast Research
https://www.readbyqxmd.com/read/28910707/spectral-phasor-analysis-reveals-altered-membrane-order-and-function-of-root-hair-cells-in-arabidopsis-dry2-sqe1-5-drought-hypersensitive-mutant
#4
Florencia Sena, Mariana Sotelo-Silveira, Soledad Astrada, Miguel A Botella, Leonel Malacrida, Omar Borsani
Biological membranes allow the regulation of numerous cellular processes, which are affected when unfavorable environmental factors are perceived. Lipids and proteins are the principal components of biological membranes. Each lipid has unique biophysical properties, and, therefore the lipid composition of the membrane is critical to maintaining the bilayer structure and functionality. Membrane composition and integrity are becoming the focus of studies aiming to understand how plants adapt to its environment...
August 26, 2017: Plant Physiology and Biochemistry: PPB
https://www.readbyqxmd.com/read/28904410/recent-advances-in-ergosterol-biosynthesis-and-regulation-mechanisms-in-saccharomyces-cerevisiae
#5
REVIEW
Zhihong Hu, Bin He, Long Ma, Yunlong Sun, Yali Niu, Bin Zeng
Ergosterol, an important component of the fungal cell membrane, is not only essential for fungal growth and development but also very important for adaptation to stress in fungi. Ergosterol is also a direct precursor for steroid drugs. The biosynthesis of ergosterol can be divided into three modules: mevalonate, farnesyl pyrophosphate (farnesyl-PP) and ergosterol biosynthesis. The regulation of ergosterol content is mainly achieved by feedback regulation of ergosterol synthase activity through transcription, translation and posttranslational modification...
September 2017: Indian Journal of Microbiology
https://www.readbyqxmd.com/read/28883505/channel-formation-and-membrane-deformation-via-sterol-aided-polymorphism-of-amphidinol-3
#6
Masayuki Iwamoto, Ayumi Sumino, Eri Shimada, Masanao Kinoshita, Nobuaki Matsumori, Shigetoshi Oiki
Amphidinol 3 (AM3) is an anti-fungal polyene extracted from a marine dinoflagellate. Here, we examined the ion channel activity and membrane-embedded structure of AM3 using a lipid bilayer method and atomic force microscopy (AFM). AM3 exhibited large-conductance (~1 nS) and non-selective single-channel activity only when sterols were present in the membrane leaflet of the AM3-added side. The variable conductance suggests the formation of a multimeric barrel-stave pore. At high AM3 concentrations, giant-conductance "jumbo" channels (~40 nS) emerged...
September 7, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28882874/haploid-mammalian-genetic-screen-identifies-ubxd8-as-a-key-determinant-of-hmgcr-degradation-and-cholesterol-biosynthesis
#7
Anke Loregger, Matthijs Raaben, Josephine Tan, Saskia Scheij, Martina Moeton, Marlene van den Berg, Hila Gelberg-Etel, Elmer Stickel, Joseph Roitelman, Thijn Brummelkamp, Noam Zelcer
OBJECTIVE: The cellular demand for cholesterol requires control of its biosynthesis by the mevalonate pathway. Regulation of HMGCR (3-hydroxy-3-methylglutaryl coenzyme A reductase), a rate-limiting enzyme in this pathway and the target of statins, is a key control point herein. Accordingly, HMGCR is subject to negative and positive regulations. In particular, the ability of oxysterols and intermediates of the mevalonate pathway to stimulate its proteasomal degradation is an exquisite example of metabolically controlled feedback regulation...
September 7, 2017: Arteriosclerosis, Thrombosis, and Vascular Biology
https://www.readbyqxmd.com/read/28873756/phytosterols-induced-viscoelasticity-of-oleogels-prepared-by-using-monoglycerides
#8
Mohd Dona Bin Sintang, Sabine Danthine, Allison Brown, Davy Van de Walle, Ashok R Patel, Iris Tavernier, Tom Rimaux, Koen Dewettinck
Monoglycerides (MGs) and phytosterols (PS) are known to form firm oleogels with liquid oil. However, the oleogels are prone to undergo polymorphic transition over time that lead to crystals' aggregation thus, compromises physical properties. Thus, we combined MGs with PS to control the crystallization and modify the morphology of the combination oleogels, as both components are reported to interact together. The oleogels were prepared at different ratio combinations and characterized in their rheological, thermal, morphology, and diffraction properties...
October 2017: Food Research International
https://www.readbyqxmd.com/read/28872598/the-torc2-dependent-signaling-network-in-the-yeast-saccharomyces-cerevisiae
#9
REVIEW
Françoise M Roelants, Kristin L Leskoske, Maria Nieves Martinez Marshall, Melissa N Locke, Jeremy Thorner
To grow, eukaryotic cells must expand by inserting glycerolipids, sphingolipids, sterols, and proteins into their plasma membrane, and maintain the proper levels and bilayer distribution. A fungal cell must coordinate growth with enlargement of its cell wall. In Saccharomyces cerevisiae, a plasma membrane-localized protein kinase complex, Target of Rapamicin (TOR) complex-2 (TORC2) (mammalian ortholog is mTORC2), serves as a sensor and masterregulator of these plasma membrane- and cell wall-associated events by directly phosphorylating and thereby stimulating the activity of two types of effector protein kinases: Ypk1 (mammalian ortholog is SGK1), along with a paralog (Ypk2); and, Pkc1 (mammalian ortholog is PKN2/PRK2)...
September 5, 2017: Biomolecules
https://www.readbyqxmd.com/read/28863820/sterol-regulation-of-voltage-gated-k-channels
#10
Andras Balajthy, Peter Hajdu, Gyorgy Panyi, Zoltan Varga
Cholesterol is an essential lipid building block of the cellular plasma membrane. In addition to its structural role, it regulates the fluidity and raft structure of the membrane and influences the course of numerous membrane-linked signaling pathways and the function of transmembrane proteins, including ion channels. This is supported by a vast body of scientific data, which demonstrates the modulation of ion channels with a great variety of ion selectivity, gating, and tissue distribution by changes in membrane cholesterol...
2017: Current Topics in Membranes
https://www.readbyqxmd.com/read/28863819/differential-effects-of-sterols-on-ion-channels-stereospecific-binding-vs-stereospecific-response
#11
Nicolas Barbera, Manuela A A Ayee, Belinda S Akpa, Irena Levitan
Numerous ion channels have been shown to be regulated by the level of membrane cholesterol, but the mechanisms responsible for these effects are still not well understood. The key question in the field is how to discriminate between the contributions of the two central mechanisms that might be responsible for the sensitivity of ion channels to cholesterol: specific sterol-protein interactions or regulation of channels by the bilayer physical properties. Comparative analysis of cholesterol and its isomers on the function of an ion channel is a powerful tool to achieve this goal...
2017: Current Topics in Membranes
https://www.readbyqxmd.com/read/28858257/lamin-b-receptor-interplay-between-structure-function-and-localization
#12
REVIEW
Eleni Nikolakaki, Ilias Mylonis, Thomas Giannakouros
Lamin B receptor (LBR) is an integral protein of the inner nuclear membrane, containing a hydrophilic N-terminal end protruding into the nucleoplasm, eight hydrophobic segments that span the membrane and a short, nucleoplasmic C-terminal tail. Two seemingly unrelated functions have been attributed to LBR. Its N-terminal domain tethers heterochromatin to the nuclear periphery, thus contributing to the shape of interphase nuclear architecture, while its transmembrane domains exhibit sterol reductase activity...
August 31, 2017: Cells
https://www.readbyqxmd.com/read/28846071/er-phospholipid-composition-modulates-lipogenesis-during-feeding-and-in-obesity
#13
Xin Rong, Bo Wang, Elisa Nd Palladino, Thomas Q de Aguiar Vallim, David A Ford, Peter Tontonoz
Sterol regulatory element-binding protein 1c (SREBP-1c) is a central regulator of lipogenesis whose activity is controlled by proteolytic cleavage. The metabolic factors that affect its processing are incompletely understood. Here, we show that dynamic changes in the acyl chain composition of ER phospholipids affect SREBP-1c maturation in physiology and disease. The abundance of polyunsaturated phosphatidylcholine in liver ER is selectively increased in response to feeding and in the setting of obesity-linked insulin resistance...
August 28, 2017: Journal of Clinical Investigation
https://www.readbyqxmd.com/read/28841344/retrospective-on-cholesterol-homeostasis-the-central-role-of-scap
#14
Michael S Brown, Arun Radhakrishnan, Joseph L Goldstein
Scap is a polytopic membrane protein that functions as a molecular machine to control the cholesterol content of membranes in mammalian cells. In the 21 years since our laboratory discovered Scap, we have learned how it binds sterol regulatory element-binding proteins (SREBPs) and transports them from the endoplasmic reticulum (ER) to the Golgi for proteolytic processing. Proteolysis releases the SREBP transcription factor domains, which enter the nucleus to promote cholesterol synthesis and uptake. When cholesterol in ER membranes exceeds a threshold, the sterol binds to Scap, triggering several conformational changes that prevent the Scap-SREBP complex from leaving the ER...
August 25, 2017: Annual Review of Biochemistry
https://www.readbyqxmd.com/read/28837104/the-lipid-raft-proteome-of-african-trypanosomes-contains-many-flagellar-proteins
#15
Aabha I Sharma, Cheryl L Olson, David M Engman
Lipid rafts are liquid-ordered membrane microdomains that form by preferential association of 3-β-hydroxysterols, sphingolipids and raft-associated proteins often having acyl modifications. We isolated lipid rafts of the protozoan parasite Trypanosoma brucei and determined the protein composition of lipid rafts in the cell. This analysis revealed a striking enrichment of flagellar proteins and several putative signaling proteins in the lipid raft proteome. Calpains and intraflagellar transport proteins, in particular, were found to be abundant in the lipid raft proteome...
August 24, 2017: Pathogens
https://www.readbyqxmd.com/read/28831063/sterol-targeting-drugs-reveal-life-cycle-stage-specific-differences-in-trypanosome-lipid-rafts
#16
Aabha I Sharma, Cheryl L Olson, João I Mamede, Felipe Gazos-Lopes, Conrad L Epting, Igor C Almeida, David M Engman
Cilia play important roles in cell signaling, facilitated by the unique lipid environment of a ciliary membrane containing high concentrations of sterol-rich lipid rafts. The African trypanosome Trypanosoma brucei is a single-celled eukaryote with a single cilium/flagellum. We tested whether flagellar sterol enrichment results from selective flagellar partitioning of specific sterol species or from general enrichment of all sterols. While all sterols are enriched in the flagellum, cholesterol is especially enriched...
August 22, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28829376/the-potential-of-%C3%AE-spinasterol-to-mimic-the-membrane-properties-of-natural-cholesterol
#17
Ivan Haralampiev, Holger A Scheidt, Daniel Huster, Peter Müller
Sterols play a unique role for the structural and dynamical organization of membranes. The current study reports data on the membrane properties of the phytosterol (3β,5α,22E)-stigmasta-7,22-dien-3-β-ol (α-spinasterol), which represents an important component of argan oil and have not been investigated so far in molecular detail. In particular, the impact of α-spinasterol on the structure and organization of lipid membranes was investigated and compared with those of cholesterol. Various membrane parameters such as the molecular packing of the phospholipid fatty acyl chains, the membrane permeability toward polar molecules, and the formation of lateral membrane domains were studied...
August 22, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/28816608/function-of-plasma-membrane-microdomain-associated-proteins-during-legume-nodulation
#18
Zhenzhen Qiao, Marc Libault
Plasma membrane microdomains are plasma membrane sub-compartments enriched in sphingolipids and sterols, and composed by a specific set of proteins. They are involved in recognizing signal molecules, transducing these signals, and controlling endocytosis and exocytosis processes. In a recent study, applying biochemical and microscopic methods, we characterized the soybean GmFWL1 protein, a major regulator of soybean nodulation, as a new membrane microdomain-associated protein. Interestingly, upon rhizobia inoculation of the soybean root system, GmFWL1 and one of its interacting partners, GmFLOT2/4, both translocate to the root hair cell tip, the primary site of interaction and infection between soybean and Rhizobium...
August 17, 2017: Plant Signaling & Behavior
https://www.readbyqxmd.com/read/28794014/iron-affects-ire1-clustering-propensity-and-the-amplitude-of-endoplasmic-reticulum-stress-signaling
#19
Nir Cohen, Michal Breker, Anush Bakunts, Kristina Pesek, Ainara Chas, Josepmaria Argemí, Andrea Orsi, Lihi Gal, Silvia Chuartzman, Yoav Wigelman, Felix Jonas, Peter Walter, Robert Ernst, Tomás Aragón, Eelco van Anken, Maya Schuldiner
The unfolded protein response (UPR) allows cells to adjust secretory pathway capacity according to need. Ire1, the endoplasmic reticulum (ER) stress sensor and central activator of the UPR is conserved from the budding yeast Saccharomyces cerevisiae to humans. Under ER stress conditions, Ire1 clusters into foci that enable optimal UPR activation. To discover factors that affect Ire1 clustering, we performed a high-content screen using a whole-genome yeast mutant library expressing Ire1-mCherry. We imaged the strains following UPR induction and found 154 strains that displayed alterations in Ire1 clustering...
August 9, 2017: Journal of Cell Science
https://www.readbyqxmd.com/read/28774891/sterol-transporters-at-membrane-contact-sites-regulate-torc1-and-torc2-signaling
#20
Andrew Murley, Justin Yamada, Bradley J Niles, Alexandre Toulmay, William A Prinz, Ted Powers, Jodi Nunnari
Membrane contact sites (MCSs) function to facilitate the formation of membrane domains composed of specialized lipids, proteins, and nucleic acids. In cells, membrane domains regulate membrane dynamics and biochemical and signaling pathways. We and others identified a highly conserved family of sterol transport proteins (Ltc/Lam) localized at diverse MCSs. In this study, we describe data indicating that the yeast family members Ltc1 and Ltc3/4 function at the vacuole and plasma membrane, respectively, to create membrane domains that partition upstream regulators of the TORC1 and TORC2 signaling pathways to coordinate cellular stress responses with sterol homeostasis...
September 4, 2017: Journal of Cell Biology
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