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Membrane Sterols

Konstantinos Koussis, Evi Goulielmaki, Anna Chalari, Chrislaine Withers-Martinez, Inga Siden-Kiamos, Kai Matuschewski, Thanasis G Loukeris
Site-2 proteases (S2P) belong to the M50 family of metalloproteases, which typically perform essential roles by mediating activation of membrane-bound transcription factors through regulated intramembrane proteolysis (RIP). Protease-dependent liberation of dormant transcription factors triggers diverse cellular responses, such as sterol regulation, Notch signalling and the unfolded protein response. Plasmodium parasites rely on regulated proteolysis for controlling essential pathways throughout the life cycle...
2017: PloS One
Michael A Cahill, Amy E Medlock
Progesterone Receptor Membrane Component 1 (PGRMC1) is located in many different subcellular locations with many different attested and probably location-specific functions. PGRMC1 was recently identified in the mitochondrial outer membrane where it interacts with ferrochelatase, the last enzyme in the heme synthetic pathway. It has been proposed that PGRMC1 may act as a chaperone to shuttle newly synthesized heme from the mitochondrion to cytochrome P450 (cyP450) enzymes. Here we consider potential roles that PGRMC1 may play in transferring heme, and other small hydrophobic ligands such as cholesterol and steroids, between the hydrophobic compartment of the membrane lipid bilayer interior to aqueous proteins, and perhaps to the membranes of other organelles...
January 16, 2017: Journal of Steroid Biochemistry and Molecular Biology
Kai Xu, Peter D Nagy
: Membranous structures derived from various organelles are important for replication of plus-stranded RNA viruses. Although the important roles of co-opted host proteins in RNA virus replication have been appreciated for a decade, the equally important functions of cellular lipids in virus replication are gaining full attention only recently. Previous works with Tomato bushy stunt tombusvirus (TBSV) in model host yeast have revealed essential roles for phosphatidylethanolamine and sterols in viral replication...
January 18, 2017: Journal of Virology
Jason M Arne, Made Airanthi K Widjaja-Adhi, Taylor Hughes, Kevin W Huynh, Josie A Silvaroli, Sylwia Chelstowska, Vera Y Moiseenkova-Bell, Marcin Golczak
The esterification of alcohols with fatty acids is a universal mechanism to form inert storage forms of sterols, di- and triacylglycerols, and retinoids. In ocular tissues, formation of retinyl esters is an essential step in the enzymatic regeneration of the visual chromophore (11-cis-retinal). Acyl-CoA wax alcohol acyltransferase 2 (AWAT2), also known as multifunctional O-acyltransferase (MFAT), is an integral membrane enzyme with a broad substrate specificity that has been shown to preferentially esterify 11-cis-retinol and thus contribute to formation of readily available pool of cis retinoids in the eye...
January 17, 2017: Journal of Lipid Research
Shiva Emami, Sodeif Azadmard-Damirchi, Seyed Hadi Peighambardoust, Javad Hesari, Hadi Valizadeh, Roland Faller
An atomic-level molecular dynamics simulation was carried out to study the effects of a plant sterol (sitosterol) and glucosylceramide (GlcCer) on a 1,2-dilinoleoylposphocholine (DLiPC) membrane. Initially, a membrane containing 50mol % sitosterol was compared with that containing the same ratio of cholesterol. These simulations showed differential condensing and ordering effects of sitosterol and cholesterol, with cholesterol being slightly more efficient than sitosterol in packing the membrane more tightly to a liquid ordered phase...
January 11, 2017: Chemistry and Physics of Lipids
Nicholas L Cianciola, Stacey Chung, Danny Manor, Cathleen R Carlin
: Human adenoviruses generally cause mild self-limiting infections but can lead to serious disease and even be fatal in high-risk individuals, underscoring the importance of understanding how the virus counteracts host defense mechanisms. This study had two goals. First, determine the molecular basis of cholesterol homeostatic responses induced by the early region 3 membrane protein RIDα via its direct interaction with the sterol-binding protein ORP1L. Second, determine how this interaction regulates innate immunity to adenovirus...
January 11, 2017: Journal of Virology
Rebika Shrestha, Cari M Anderson, Alfredo E Cardenas, Ron Elber, Lauren J Webb
Biological membranes are heterogeneous structures with complex electrostatic profiles arising from lipids, sterols, membrane proteins, and water molecules. We investigated the effect of cholesterol and its derivative 6-ketocholestanol (6-kc) on membrane electrostatics by directly measuring the dipole electric field (F ) within lipid bilayers containing cholesterol or 6-kc at concentrations of 0-40 mol% through the vibrational Stark effect (VSE). We found that adding low concentrations of cholesterol, up to ~10 mol%, increases F, while adding more cholesterol up to 40 mol% lowers F...
January 10, 2017: Journal of Physical Chemistry. B
Chang Wang, Yuming Yu, Steven L Regen
The forces that drive lipid raft formation are poorly understood. To date, most of the attention has focused on attractive interactions between cholesterol and high-melting lipids. Remarkably little attention has been paid to repulsive forces. Here, we show that repulsive interactions between an exchangeable mimic of cholesterol and an exchangeable mimic of a low-melting phospholipid in liquid-disordered bilayers can be much stronger than the attractive forces between this same sterol and an exchangeable mimic of a high-melting phospholipid in liquid-ordered bilayers...
January 9, 2017: Angewandte Chemie
Jonas Van der Paal, Claudia Verheyen, Erik C Neyts, Annemie Bogaerts
In recent years, the ability of cold atmospheric pressure plasmas (CAPS) to selectively induce cell death in cancer cells has been widely established. This selectivity has been assigned to the reactive oxygen and nitrogen species (RONS) created in CAPs. To provide new insights in the search for an explanation for the observed selectivity, we calculate the transfer free energy of multiple ROS across membranes containing a varying amount of cholesterol. The cholesterol fraction is investigated as a selectivity parameter because membranes of cancer cells are known to contain lower fractions of cholesterol compared to healthy cells...
January 6, 2017: Scientific Reports
Kamila Riedlová, Michaela Nekardová, Petr Kačer, Kamila Syslová, Mario Vazdar, Pavel Jungwirth, Eva Kudová, Lukasz Cwiklik
Interactions of two neurosteroids, inhibiting membrane-bound N-Methyl-d-aspartate receptors, with phospholipid membranes are studied. Namely, endogenous pregnanolone sulfate is compared with pregnanolone glutamate, the latter being a novel synthetic steroidal inhibitor of these receptors with potential pharmaceutical use. Molecular-level details of steroid-phospholipid membranes interactions are scrutinized employing molecular dynamics simulations supported by quantum chemical calculations to assess steroid lipophilicity...
December 30, 2016: Chemistry and Physics of Lipids
Pu Pu, Craig E Stone, Joshua T Burdick, John I Murray, Meera V Sundaram
Lipocalins are secreted cup-shaped glycoproteins that bind sterols, fatty acids, and other lipophilic molecules. Lipocalins have been implicated in a wide array of processes related to lipophilic cargo transport, sequestration and signaling, and several are used as biomarkers for human disease, but the functions of most lipocalins remain poorly understood. Here we show that the C. elegans lipocalin LPR-1 is required to maintain apical membrane integrity and a continuous lumen in two narrow, unicellular tubes, the excretory duct and pore, during a period of rapid lumen elongation...
December 30, 2016: Genetics
Amy B Banta, Jeremy H Wei, Clare C C Gill, José-Luis Giner, Paula V Welander
Cyclic triterpenoids are a broad class of polycyclic lipids produced by bacteria and eukaryotes. They are biologically relevant for their roles in cellular physiology, including membrane structure and function, and biochemically relevant for their exquisite enzymatic cyclization mechanism. Cyclic triterpenoids are also geobiologically significant as they are readily preserved in sediments and are used as biomarkers for ancient life throughout Earth's history. Isoarborinol is one such triterpenoid whose only known biological sources are certain angiosperms and whose diagenetic derivatives (arboranes) are often used as indicators of terrestrial input into aquatic environments...
January 10, 2017: Proceedings of the National Academy of Sciences of the United States of America
Michael N Trinh, Feiran Lu, Xiaochun Li, Akash Das, Qiren Liang, Jef K De Brabander, Michael S Brown, Joseph L Goldstein
Niemann-Pick C1 (NPC1), a membrane protein of lysosomes, is required for the export of cholesterol derived from receptor-mediated endocytosis of LDL. Lysosomal cholesterol export is reportedly inhibited by itraconazole, a triazole that is used as an antifungal drug [Xu et al. (2010) Proc Natl Acad Sci USA 107:4764-4769]. Here we show that posaconazole, another triazole, also blocks cholesterol export from lysosomes. We prepared P-X, a photoactivatable cross-linking derivative of posaconazole. P-X cross-linked to NPC1 when added to intact cells...
January 3, 2017: Proceedings of the National Academy of Sciences of the United States of America
L F Galiullina, O V Aganova, I A Latfullin, G S Musabirova, A V Aganov, V V Klochkov
Hydroxy-methyl-glutaryl-coenzyme A (HMG-CoA) reductase inhibitors or statins reduce the amount of low-density lipoprotein (LDL) cholesterol, which is known as a well-established risk factor for atherosclerosis. Despite the fact that statins have a common pharmacologic target essential to sterol biosynthesis, their efficacy, safety, and potential non-LDL actions vary significantly for different statins. There is a hypothesis that pharmacological features of statins depend on their location in cell membrane, but to the present day there is a lack of information in literature on interactions of statins with the surface of the cell membrane in liquid media...
December 16, 2016: Biochimica et Biophysica Acta
Nanbiao Long, Xiaoling Xu, Qiuqiong Zeng, Hong Sang, Ling Lu
: Ergosterol, a fungal specific sterol enriched in cell plasma membranes, is an effective antifungal drug target. However, current knowledge of the ergosterol biosynthesis process in the saprophytic human fungal pathogen Aspergillus fumigatus remains limited. In this study, we identified that two endoplasmic reticulum-localized sterol C-24 reductases encoded by both erg4A and erg4B homologs are required to catalyze the reaction during the final step of ergosterol biosynthesis. Loss of one homolog of Erg4 induces the over-expression of the other one, accompanied with almost normal ergosterol synthesis and the wild-type colony growth...
December 16, 2016: Applied and Environmental Microbiology
Sascha Martens, Shuhei Nakamura, Tamotsu Yoshimori
Autophagosomes are double membrane organelles that are formed during a process referred to as macroautophagy. They serve to deliver cytoplasmic material into the lysosome for degradation. Autophagosomes are formed in a de novo manner and are the result of substantial membrane remodeling processes involving numerous protein-lipid interactions. While most studies focus on the proteins involved in autophagosome formation it is obvious that lipids including phospholipids, sphingolipids and sterols play an equally important role...
October 27, 2016: Journal of Molecular Biology
Jeremy S Dittman, Anant K Menon
Sterol transport between the endoplasmic reticulum (ER) and plasma membrane (PM) occurs by nonvesicular mechanisms requiring sterol transport proteins (STPs). Here we examine the idea that transport is enhanced at membrane contact sites where the ER is closely apposed to the PM. We conclude that sterol desorption from the membrane, rather than STP-mediated diffusion, is rate limiting in the cellular context, so there is no apparent kinetic benefit to having STP-mediated sterol transfer occur at contact sites...
December 9, 2016: Trends in Biochemical Sciences
Heba Al Khamici, Khondher R Hossain, Bruce A Cornell, Stella M Valenzuela
The Chloride Intracellular Ion Channel (CLIC) family consists of six conserved proteins in humans. These are a group of enigmatic proteins, which adopt both a soluble and membrane bound form. CLIC1 was found to be a metamorphic protein, where under specific environmental triggers it adopts more than one stable reversible soluble structural conformation. CLIC1 was found to spontaneously insert into cell membranes and form chloride ion channels. However, factors that control the structural transition of CLIC1 from being an aqueous soluble protein into a membrane bound protein have yet to be adequately described...
December 8, 2016: Membranes
Sherrelle Milligan, Gregory G Martin, Danilo Landrock, Avery L McIntosh, John T Mackie, Friedhelm Schroeder, Ann B Kier
In vitro studies suggest that liver fatty acid binding protein (L-FABP) and sterol carrier protein-2/sterol carrier protein-x (SCP2/SCPx) gene products facilitate uptake and metabolism and detoxification of dietary-derived phytol in mammals. However, concomitant upregulation of L-FABP in SCP2/SCPx null mice complicates interpretation of their physiological phenotype. Therefore, the impact of ablating both the L-FABP gene and SCP2/SCPx gene (L-FABP/SCP2/SCPx null or TKO) was examined in phytol-fed female wild-type (WT) and TKO mice...
December 6, 2016: Biochimica et Biophysica Acta
Abdullah Al Mamun, Michio Hashimoto, Masanori Katakura, Yoko Tanabe, Satoru Tsuchikura, Shahdat Hossain, Osamu Shido
The effects of cholesterol-lowering statins, which substantially benefit future cardiovascular events, on fatty acid metabolism have remained largely obscured. In this study, we investigated the effects of atorvastatin on fatty acid metabolism together with the effects of TAK-085 containing highly purified eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) ethyl ester on atorvastatin-induced n-3 polyunsaturated fatty acid lowering in SHR.Cg-Lepr(cp)/NDmcr (SHRcp) rats, as a metabolic syndrome model...
January 2017: Biomedicine & Pharmacotherapy, Biomédecine & Pharmacothérapie
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