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Elsa Perrody, Laurence Abrami, Michal Feldman, Beatrice Kunz, Sylvie Urbé, Gisou van der Goot
Many membrane proteins fold inefficiently and require the help of enzymes and chaperones. Here we reveal a novel folding assistance system that operates on membrane proteins from the cytosolic side of the endoplasmic reticulum (ER). We show that folding of the Wnt signaling coreceptor LRP6 is promoted by ubiquitination of a specific lysine, retaining it in the ER while avoiding degradation. Subsequent ER exit requires removal of ubiquitin from this lysine by the deubiquitinating enzyme USP19. This ubiquitination-deubiquitination is conceptually reminiscent of the glucosylation-deglucosylation occurring in the ER lumen during the calnexin/calreticulin folding cycle...
October 18, 2016: ELife
Sang Joon Won, Dahvid Davda, Kristin J Labby, Sin Ye Hwang, Rachel E Pricer, Jaimeen D Majmudar, Kira A Armacost, Laura A Rodriguez, Christina L Rodriguez, Fei San Chong, Kristopher A Torossian, Jasmine Palakurthi, Edward S Hur, Jennifer L Meagher, Charles L Brooks, Jeanne A Stuckey, Brent R Martin
Post-translational S-palmitoylation directs the trafficking and membrane localization of hundreds of cellular proteins, often involving a coordinated palmitoylation cycle that requires both protein acyl transferases (PATs) and acyl protein thioesterases (APTs) to actively re-distribute S-palmitoylated proteins towards different cellular membrane compartments. This process is necessary for the trafficking and oncogenic signaling of S-palmitoylated Ras isoforms, and potentially other peripheral membrane proteins...
October 17, 2016: ACS Chemical Biology
Jingtao Luo, Yun Hong, Xiaoan Tao, Xi Wei, Lun Zhang, Qiang Li
Unlike normal cells, cancer cells are recently identified to rely on aerobic glycolysis for energy production called the Warburg effect. Several attempts are being made to target this metabolic reprogramming pathway in treating cancers; however, the successful rate is very limited. In this study, we investigated the functional roles of fatty acid oxidation key enzyme carnitine palmitoyl transferase 1a (CPT-1a), during the metabolic programming of pancreatic ductal adenocarcinoma (PDAC) cells induced by glucose deprivation...
October 13, 2016: Tumour Biology: the Journal of the International Society for Oncodevelopmental Biology and Medicine
Efrat Gottlieb-Abraham, Orit Gutman, Govind M Pai, Ignacio Rubio, Yoav I Henis
The interactions of Src family kinases (SFKs) with the plasma membrane are crucial for their activity. They depend on their fatty-acylated N-termini, containing N-myristate and either a polybasic cluster (in Src) or palmitoylation sites (e.g., Fyn). To investigate the roles of these moieties in SFK membrane association, we employed FRAP beam-size analysis to study the membrane interactions of c-Src-GFP or Fyn-GFP fatty-acylation mutants. Our studies showed for the first time that the membrane association of Fyn is more stable than that of Src, an effect lost in a Fyn mutant lacking the palmitoylation sites...
October 12, 2016: Molecular Biology of the Cell
Kiera R Flynn, Lisandra L Martin, M Leigh Ackland, Angel A J Torriero
Docosahexaenoic acid (DHA) is the most abundant polyunsaturated omega-3 fatty acid found in mammalian neuronal cell membranes. While DHA is known to be important for neuronal cell survival, little is know about how DHA interacts with phospholipid bilayers. This study presents a detailed quartz crystal microbalance with dissipation monitoring (QCM-D) analysis of free DHA interactions with individual and mixed phospholipid supported lipid bilayers (SLB). DHA incorporation and subsequent changes to the SLBs viscoelastic properties were observed to be concentration-dependent, influenced by the phospholipid species, the head-group charge and the presence or absence of calcium ions...
October 11, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Meredith Meyer, Attila D Kovács, David A Pearce
Infantile CLN1 disease, also known as infantile neuronal ceroid lipofuscinosis, is a fatal childhood neurodegenerative disorder caused by mutations in the CLN1 gene. CLN1 encodes a soluble lysosomal enzyme, palmitoyl protein thioesterase 1 (PPT1), and it is still unclear why neurons are selectively vulnerable to the loss of PPT1 enzyme activity in infantile CLN1 disease. To examine the effects of PPT1 deficiency on several well-defined neuronal signaling and cell death pathways, different toxic insults were applied in cerebellar granule neuron cultures prepared from wild type (WT) and palmitoyl protein thioesterase 1-deficient (Ppt1 (-/-) ) mice, a model of infantile CLN1 disease...
October 8, 2016: Metabolic Brain Disease
C Satriano, G Lupo, C Motta, C D Anfuso, P Di Pietro, B Kasemo
Hybrid nanoassemblies of ferritin and silica-supported lipid bilayers (ferritin-SLBs) have been prepared and tested for the adhesion, spreading and proliferation of retinal microvascular endothelial cells (ECs). Lipid membranes with varying surface charge were obtained by mixing cationic 1-palmitoyl-2-oleoyl-sn-glycero-3-ethylphosphocholine (POEPC) with zwitterionic 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) at increasing POPC/POEPC ratios. The supported bilayer formation and their subsequent interaction processes with ferritin were studied at the pH of 7...
October 4, 2016: Colloids and Surfaces. B, Biointerfaces
Miriam Payá-Milans, Jose Antonio Aznar-Moreno, Tiago S Balbuena, Richard P Haslam, Satinder K Gidda, Javier Pérez-Hormaeche, Robert T Mullen, Jay J Thelen, Johnathan A Napier, Joaquín J Salas, Rafael Garcés, Enrique Martínez-Force, Mónica Venegas-Calerón
In oil crops, triacylglycerol biosynthesis is an important metabolic pathway in which glycerol-3-phosphate acyltransferase (GPAT) performs the first acylation step. Mass spectrometry analysis of developing sunflower (Helianthus annuus) seed membrane fractions identified an abundant GPAT, HaGPAT9 isoform 1, with a N-terminal peptide that possessed two phosphorylated residues with possible regulatory function. HaGPAT9-1 belongs to a broad eukaryotic GPAT family, similar to mammalian GPAT3, and it represents one of the two sunflower GPAT9 isoforms, sharing 90% identity with HaGPAT9-2...
November 2016: Plant Science: An International Journal of Experimental Plant Biology
Debby P Chang, Aleksandra P Dabkowska, Richard A Campbell, Maria Wadsäter, Justas Barauskas, Fredrik Tiberg, Tommy Nylander
Reversed lipid liquid crystalline nanoparticles (LCNPs) of the cubic micellar (I2) phase have high potential in drug delivery applications due to their ability to encapsulate both hydrophobic and hydrophilic drug molecules. Their interactions with various interfaces, and the consequences for the particle structure and integrity, are essential considerations in their effectiveness as drug delivery vehicles. Here, we have studied LCNPs formed of equal fractions of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine and glycerol dioleate in the presence of different fractions of the stabilizer Polysorbate 80...
September 29, 2016: Physical Chemistry Chemical Physics: PCCP
Brett J Roberts, Robert A Svoboda, Andrew M Overmiller, Joshua D Lewis, Andrew P Kowalczyk, My G Mahoney, Keith R Johnson, James K Wahl
Desmosomes are prominent adhesive junctions present between many epithelial cells as well as cardiomyocytes. The mechanisms controlling desmosome assembly and remodeling in epithelial and cardiac tissue are poorly understood. We recently identified protein palmitoylation as a mechanism regulating desmosome dynamics. In this study we have focused on the palmitoylation of the desmosomal cadherin, desmoglein-2 (Dsg2), and characterized the role that palmitoylation of Dsg2 plays in its localization and stability in cultured cells...
October 4, 2016: Journal of Biological Chemistry
Huanjie Wang, Fancui Meng
The interactions between rofecoxib and POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) bilayer were studied using all-atom molecular dynamics simulation method. Four POPC bilayer systems with different number of rofecoxib molecules were constructed to simulate different drug concentration. The free energy of rofecoxib passing across pure POPC bilayer has two minima (at z ∼1.2nm or 1.6nm). As for the high concentration model, the minimum of the free energy profile slightly shifts to the bilayer center...
September 23, 2016: Journal of Molecular Graphics & Modelling
Wolfgang Bernhard
Lung surfactant is a complex with a unique phospholipid and protein composition. Its specific function is to reduce surface tension at the pulmonary air-liquid interface. The underlying Young-Laplace equation, applying to the surface of any geometrical structure, is the more important the smaller its radii are. It therefore applies to the alveoli and bronchioli of mature lungs, as well as to the tubules and saccules of immature lungs. Surfactant comprises 80% phosphatidylcholine (PC), of which dipalmitoyl-PC, palmitoyl-myristoyl-PC and palmitoyl-palmitoleoyl-PC together are 75%...
September 29, 2016: Annals of Anatomy, Anatomischer Anzeiger: Official Organ of the Anatomische Gesellschaft
Nancy Gupta, Satish Vedi, Dennis Y Kunimoto, Babita Agrawal, Rakesh Kumar
Mycobacterium tuberculosis (Mtb), the bacterial cause of tuberculosis, is a leading infectious agent worldwide. The development of a new vaccine against Mtb is essential to control global spread of tuberculosis, since the current vaccine BCG is not very effective and antibiotic resistance is a serious, burgeoning problem. ESAT-6 is a secreted protein of Mtb, which is absent in BCG but has been implicated in inducing protective immunity against Mtb. Peptide based subunit vaccines are attractive due to their safety and high specificity in eliciting immune responses, but small synthetic peptides are usually not very immunogenic...
September 29, 2016: Vaccine
Rachel Fickes, Dennis R Voelker, Karin Zemski Berry, Robert C Murphy
RATIONALE: Structural analogs of the bioactive lipid, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol, were synthesized with a xylitol polar headgroup and both diacyl and diether radyl groups. Mass spectral characterization of xylitol phospholipids (PX) was carried out using collisional activation and high resolution mass measurements of positive molecular ion species and compared with the phosphatidylglycerol (PG) analogs. METHODS: Xylitol phospholipids were synthesized using a transphosphatidylation reaction catalyzed by phospholipase D and purified by HPLC...
September 30, 2016: Rapid Communications in Mass Spectrometry: RCM
Birgit Ploier, Anant K Menon
Scramblases translocate phospholipids across the membrane bilayer bidirectionally in an ATP-independent manner. The first scramblase to be identified and biochemically verified was opsin, the apoprotein of the photoreceptor rhodopsin. Rhodopsin is a G protein-coupled receptor localized in rod photoreceptor disc membranes of the retina where it is responsible for the perception of light. Rhodopsin's scramblase activity does not depend on its ligand 11-cis-retinal, i.e., the apoprotein opsin is also active as a scramblase...
2016: Journal of Visualized Experiments: JoVE
Laura E Mariani, Maarten F Bijlsma, Anna I Ivanova, Sarah K Suciu, Richard A Kahn, Tamara Caspary
The regulatory GTPase Arl13b localizes to primary cilia, where it regulates Sonic hedgehog (Shh) signaling. Missense mutations in ARL13B can cause the ciliopathy Joubert syndrome, while the mouse null allele is embryonic lethal. We used mouse embryonic fibroblasts as a system to determine the effects of Arl13b mutations on Shh signaling. We tested a total of seven different mutants, three JS-causing variants, two point mutants predicted to alter guanine nucleotide handling, one that disrupts cilia localization, and one that prevents palmitoylation and thus membrane binding, in assays of transcriptional and non-transcriptional Shh signaling...
September 28, 2016: Molecular Biology of the Cell
Manuel Adrian Troncoso-Ponce, Guillaume Barthole, Geoffrey Tremblais, Alexandra To, Martine Miquel, Loic Lepiniec, Sébastien Baud
In angiosperms, double fertilization of the embryo sac initiates the development of the embryo and the endosperm. In Arabidopsis thaliana, an exalbuminous species, the endosperm is reduced to one cell layer during seed maturation and reserves such as oil are massively deposited in the enlarging embryo. Here, we consider the strikingly different fatty acid (FA) compositions of the oils stored in the two zygotic tissues. Endosperm oil is enriched in ω-7 monounsaturated FAs, that represent more than 20 Mol% of total FAs, whereas these molecular species are ten-fold less abundant in the embryo...
September 28, 2016: Plant Cell
Sheila López-Cobo, Carmen Campos-Silva, Mar Valés-Gómez
Communication within the immune system depends on the release of factors that can travel and transmit information at points distant from the cell that produced them. In general, immune cells use two key strategies that can occur either at the plasma membrane or in intracellular compartments to produce such factors, vesicle release and proteolytic cleavage. Release of soluble factors in exosomes, a subset of vesicles that originate from intracellular compartments, depends generally on biochemical and lipid environment features...
2016: Frontiers in Cell and Developmental Biology
Joana Fernandes Guerreiro, Alexander Muir, Subramaniam Ramachandran, Jeremy Thorner, Isabel Sá-Correia
Acetic acid-induced inhibition of yeast growth and metabolism limits the productivity of industrial fermentation processes, especially when lignocellulosic hydrolysates are used as feedstock in industrial biotechnology. Tolerance to acetic acid of food spoilage yeasts is also a problem in the preservation of acidic foods and beverages. Thus, understanding the molecular mechanisms underlying adaptation and tolerance to acetic acid stress is increasingly important in Industrial Biotechnology and Food Industry...
September 26, 2016: Biochemical Journal
Liqing Gu, Renã A S Robinson
Cysteine is a highly reactive amino acid and is subject to a variety of reversible post-translational modifications (PTMs), including nitrosylation, glutathionylation, palmitoylation, as well as formation of sulfenic acid and disulfides. These modifications are not only involved in normal biological activities, such as enzymatic catalysis, redox signaling and cellular homeostasis, but can also be the result of oxidative damage. Especially in aging and neurodegenerative diseases, oxidative stress leads to aberrant cysteine oxidations that affect protein structure and function leading to neurodegeneration as well as other detrimental effects...
September 26, 2016: Proteomics. Clinical Applications
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