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Dimitrios Stamou

Rasmus Herlo, Viktor K Lund, Matthew D Lycas, Anna M Jansen, George Khelashvili, Rita C Andersen, Vikram Bhatia, Thomas S Pedersen, Pedro B C Albornoz, Niklaus Johner, Ina Ammendrup-Johnsen, Nikolaj R Christensen, Simon Erlendsson, Mikkel Stoklund, Jannik B Larsen, Harel Weinstein, Ole Kjærulff, Dimitrios Stamou, Ulrik Gether, Kenneth L Madsen
BAR domains are dimeric protein modules that sense, induce, and stabilize lipid membrane curvature. Here, we show that membrane curvature sensing (MCS) directs cellular localization and function of the BAR domain protein PICK1. In PICK1, and the homologous proteins ICA69 and arfaptin2, we identify an amphipathic helix N-terminal to the BAR domain that mediates MCS. Mutational disruption of the helix in PICK1 impaired MCS without affecting membrane binding per se. In insulin-producing INS-1E cells, super-resolution microscopy revealed that disruption of the helix selectively compromised PICK1 density on insulin granules of high curvature during their maturation...
May 15, 2018: Cell Reports
Aliki Stamou, Athanasios Liaskas, Ioannis-Georgios Tzanninis, Eftyhia Kanioura, Dimitrios Politis, Kalliopi-Anna Poulia, Vasiliki Skarlatou, Nora-Athina Viniou, Konstantinos Konstantopoulos, Panagiotis Diamantopoulos
No abstract text is available yet for this article.
April 2018: Clinical Nutrition ESPEN
Konstantinos Droutsas, Dimitrios Papaconstantinou, Ilias Georgalas, Georgios Kymionis, Konstantinos Andreanos, Elli Stamou, Nikolaos Mamas
PURPOSE: To describe the use of equine pericardium as an off-label temporary emergency treatment of scleral and corneal perforations. METHODS: Three eyes of two male patients aged 34 and 38 years were included, i.e. a case with a history of severe bilateral thermal burn undergoing phacoemulsification complicated by tearing of the main port causing iris exposure and a patient with bilateral corneal perforation secondary to non-infectious corneal melt due to presumed ocular non-steroid anti-inflammatory drug abuse...
December 19, 2017: International Ophthalmology
Jannik B Larsen, Celeste Kennard, Søren L Pedersen, Knud J Jensen, Mark J Uline, Nikos S Hatzakis, Dimitrios Stamou
Proteins anchored to membranes through covalently linked fatty acids and/or isoprenoid groups play crucial roles in all forms of life. Sorting and trafficking of lipidated proteins has traditionally been discussed in the context of partitioning to membrane domains of different lipid composition. We recently showed that membrane shape/curvature can in itself mediate the recruitment of lipidated proteins. However, exactly how membrane curvature and composition synergize remains largely unexplored. Here we investigated how three critical structural parameters of lipids, namely acyl chain saturation, headgroup size, and acyl chain length, modulate the capacity of membrane curvature to recruit lipidated proteins...
September 19, 2017: Biophysical Journal
Theodora Agalioti, Anastasios D Giannou, Anthi C Krontira, Nikolaos I Kanellakis, Danai Kati, Malamati Vreka, Mario Pepe, Magda Spella, Ioannis Lilis, Dimitra E Zazara, Eirini Nikolouli, Nikolitsa Spiropoulou, Andreas Papadakis, Konstantina Papadia, Apostolos Voulgaridis, Vaggelis Harokopos, Panagiota Stamou, Silke Meiners, Oliver Eickelberg, Linda A Snyder, Sophia G Antimisiaris, Dimitrios Kardamakis, Ioannis Psallidas, Antonia Marazioti, Georgios T Stathopoulos
Malignant pleural effusion (MPE) is the lethal consequence of various human cancers metastatic to the pleural cavity. However, the mechanisms responsible for the development of MPE are still obscure. Here we show that mutant KRAS is important for MPE induction in mice. Pleural disseminated, mutant KRAS bearing tumour cells upregulate and systemically release chemokine ligand 2 (CCL2) into the bloodstream to mobilize myeloid cells from the host bone marrow to the pleural space via the spleen. These cells promote MPE formation, as indicated by splenectomy and splenocyte restoration experiments...
May 16, 2017: Nature Communications
Kadla R Rosholm, Natascha Leijnse, Anna Mantsiou, Vadym Tkach, Søren L Pedersen, Volker F Wirth, Lene B Oddershede, Knud J Jensen, Karen L Martinez, Nikos S Hatzakis, Poul Martin Bendix, Andrew Callan-Jones, Dimitrios Stamou
The targeted spatial organization (sorting) of Gprotein-coupled receptors (GPCRs) is essential for their biological function and often takes place in highly curved membrane compartments such as filopodia, endocytic pits, trafficking vesicles or endosome tubules. However, the influence of geometrical membrane curvature on GPCR sorting remains unknown. Here we used fluorescence imaging to establish a quantitative correlation between membrane curvature and sorting of three prototypic class A GPCRs (the neuropeptide Y receptor Y2, the β1 adrenergic receptor and the β2 adrenergic receptor) in living cells...
July 2017: Nature Chemical Biology
Salome Veshaguri, Sune M Christensen, Gerdi C Kemmer, Garima Ghale, Mads P Møller, Christina Lohr, Andreas L Christensen, Bo H Justesen, Ida L Jørgensen, Jürgen Schiller, Nikos S Hatzakis, Michael Grabe, Thomas Günther Pomorski, Dimitrios Stamou
In eukaryotes, P-type adenosine triphosphatases (ATPases) generate the plasma membrane potential and drive secondary transport systems; however, despite their importance, their regulation remains poorly understood. We monitored at the single-molecule level the activity of the prototypic proton-pumping P-type ATPase Arabidopsis thaliana isoform 2 (AHA2). Our measurements, combined with a physical nonequilibrium model of vesicle acidification, revealed that pumping is stochastically interrupted by long-lived (~100 seconds) inactive or leaky states...
March 25, 2016: Science
Sune M Christensen, Meredith G Triplet, Christopher Rhodes, Jeffrey S Iwig, Hsiung-Lin Tu, Dimitrios Stamou, Jay T Groves
Activation of small GTPases of the Ras superfamily by guanine nucleotide exchange factors (GEFs) is a key step in numerous cell signaling processes. Unveiling the detailed molecular mechanisms of GEF-GTPase signaling interactions is of great importance due to their central roles in cell biology, including critical disease states, and their potential as therapeutic targets. Here we present an assay to monitor individual Ras activation events catalyzed by single molecules of the GEF Son of Sevenless (SOS) in the natural membrane environment...
April 13, 2016: Nano Letters
Mengqiu Li, Sune K Jørgensen, Duncan G G McMillan, Łukasz Krzemiński, Nikolaos N Daskalakis, Riitta H Partanen, Marijonas Tutkus, Roman Tuma, Dimitrios Stamou, Nikos S Hatzakis, Lars J C Jeuken
Heme-copper oxidases (HCOs) are key enzymes in prokaryotes and eukaryotes for energy production during aerobic respiration. They catalyze the reduction of the terminal electron acceptor, oxygen, and utilize the Gibbs free energy to transport protons across a membrane to generate a proton (ΔpH) and electrochemical gradient termed proton motive force (PMF), which provides the driving force for the adenosine triphosphate (ATP) synthesis. Excessive PMF is known to limit the turnover of HCOs, but the molecular mechanism of this regulatory feedback remains relatively unexplored...
December 30, 2015: Journal of the American Chemical Society
Lars Iversen, Signe Mathiasen, Jannik Bruun Larsen, Dimitrios Stamou
No abstract text is available yet for this article.
November 2015: Nature Chemical Biology
Konstantinos Stamou, Dimitrios Tsamis, Nikolaos Pallas, Evangelia Samanta, Nikolaos Courcoutsakis, Panos Prassopoulos, Antonios-Apostolos Tentes
BACKGROUND: Encouraging results on survival of patients with malignant peritoneal mesothelioma have been shown with the use of cytoreductive surgery and perioperative intraperitoneal chemotherapy. This study explores the impact of aggressive surgical treatment on overall survival of peritoneal mesothelioma. METHODS: This is a retrospective analysis of prospectively collected clinical data of all patients with diagnosis of malignant peritoneal mesothelioma treated in a designated referral centre in Greece...
2015: International Journal of Hyperthermia
Sharon E Miller, Signe Mathiasen, Nicholas A Bright, Fabienne Pierre, Bernard T Kelly, Nikolay Kladt, Astrid Schauss, Christien J Merrifield, Dimitrios Stamou, Stefan Höning, David J Owen
The size of endocytic clathrin-coated vesicles (CCVs) is remarkably uniform, suggesting that it is optimized to achieve the appropriate levels of cargo and lipid internalization. The three most abundant proteins in mammalian endocytic CCVs are clathrin and the two cargo-selecting, clathrin adaptors, CALM and AP2. Here we demonstrate that depletion of CALM causes a substantial increase in the ratio of "open" clathrin-coated pits (CCPs) to "necked"/"closed" CCVs and a doubling of CCP/CCV diameter, whereas AP2 depletion has opposite effects...
April 20, 2015: Developmental Cell
Lixue Zhang, Sune M Christensen, Poul Martin Bendix, Vikram Kjøller Bhatia, Steffen Loft, Dimitrios Stamou
Single nanoparticle analysis: An interferometric optical approach calibrates sizes of gold nanoparticles (AuNPs) from the interference intensities by calibrating their interferometric signals against the corresponding transmission electron microscopy measurements. This method is used to investigate whether size affects the diffusion behavior of AuNPs conjugated to supported lipid bilayer membranes and to multiplex the simultaneous detection of three different AuNP labels.
August 5, 2015: Small
Jannik Bruun Larsen, Martin Borch Jensen, Vikram K Bhatia, Søren L Pedersen, Thomas Bjørnholm, Lars Iversen, Mark Uline, Igal Szleifer, Knud J Jensen, Nikos S Hatzakis, Dimitrios Stamou
Trafficking and sorting of membrane-anchored Ras GTPases are regulated by partitioning between distinct membrane domains. Here, in vitro experiments and microscopic molecular theory reveal membrane curvature as a new modulator of N-Ras lipid anchor and palmitoyl chain partitioning. Membrane curvature was essential for enrichment in raft-like liquid-ordered phases; enrichment was driven by relief of lateral pressure upon anchor insertion and most likely affects the localization of lipidated proteins in general...
March 2015: Nature Chemical Biology
Signe Mathiasen, Sune M Christensen, Juan José Fung, Søren G F Rasmussen, Jonathan F Fay, Sune K Jorgensen, Salome Veshaguri, David L Farrens, Maria Kiskowski, Brian Kobilka, Dimitrios Stamou
Proteoliposome reconstitution is a standard method to stabilize purified transmembrane proteins in membranes for structural and functional assays. Here we quantified intrareconstitution heterogeneities in single proteoliposomes using fluorescence microscopy. Our results suggest that compositional heterogeneities can severely skew ensemble-average proteoliposome measurements but also enable ultraminiaturized high-content screens. We took advantage of this screening capability to map the oligomerization energy of the β2-adrenergic receptor using ∼10(9)-fold less protein than conventional assays...
September 2014: Nature Methods
Lars Iversen, Hsiung-Lin Tu, Wan-Chen Lin, Sune M Christensen, Steven M Abel, Jeff Iwig, Hung-Jen Wu, Jodi Gureasko, Christopher Rhodes, Rebecca S Petit, Scott D Hansen, Peter Thill, Cheng-Han Yu, Dimitrios Stamou, Arup K Chakraborty, John Kuriyan, Jay T Groves
Activation of the small guanosine triphosphatase H-Ras by the exchange factor Son of Sevenless (SOS) is an important hub for signal transduction. Multiple layers of regulation, through protein and membrane interactions, govern activity of SOS. We characterized the specific activity of individual SOS molecules catalyzing nucleotide exchange in H-Ras. Single-molecule kinetic traces revealed that SOS samples a broad distribution of turnover rates through stochastic fluctuations between distinct, long-lived (more than 100 seconds), functional states...
July 4, 2014: Science
Dimitris J Apostolopoulos, Efstratios N Koletsis, Trifon Spyridonidis, Anna Paschali, Nikolaos Papandrianos, Eleni Stamou, Pavlos J Vassilakos, Dimitrios Dougenis
OBJECTIVE: To investigate the potential role of Tc-99m depreotide (Tc-DEPR) in the preoperative lymph node (N) staging of non-small-cell lung cancer (NSCLC). METHODS: Sixty-one patients with NSCLC at the potentially operable stage were enrolled and underwent scintigraphy before surgery (n=56) or mediastinoscopy (n=5). Imaging was performed with a hybrid single photon emission computed tomography/computed tomography (SPECT/CT) system. Depreotide uptake in N stations was evaluated visually and semi-quantitatively and compared to histology...
June 2014: Annals of Nuclear Medicine
Asger Tonnesen, Sune M Christensen, Vadym Tkach, Dimitrios Stamou
Transmembrane proteins are embedded in cellular membranes of varied lipid composition and geometrical curvature. Here, we studied for the first time the allosteric effect of geometrical membrane curvature on transmembrane protein structure and function. We used single-channel optical analysis of the prototypic transmembrane β-barrel α-hemolysin (α-HL) reconstituted on immobilized single small unilamellar liposomes of different diameter and therefore curvature. Our data demonstrate that physiologically abundant geometrical membrane curvatures can enforce a dramatic allosteric regulation (1000-fold inhibition) of α-HL permeability...
January 7, 2014: Biophysical Journal
Tomas Laursen, Aparajita Singha, Nicolai Rantzau, Marijonas Tutkus, Jonas Borch, Per Hedegård, Dimitrios Stamou, Birger Lindberg Møller, Nikos S Hatzakis
Electron transfer between membrane spanning oxidoreductase enzymes controls vital metabolic processes. Here we studied for the first time with single molecule resolution the function of P450 oxidoreductase (POR), the canonical membrane spanning activator of all microsomal cytochrome P450 enzymes. Measurements and statistical analysis of individual catalytic turnover cycles shows POR to sample at least two major functional states. This phenotype may underlie regulatory interactions with different cytochromes P450 but to date has remained masked in bulk kinetics...
March 21, 2014: ACS Chemical Biology
Hongxia Zhao, Alphée Michelot, Essi V Koskela, Vadym Tkach, Dimitrios Stamou, David G Drubin, Pekka Lappalainen
Bin-Amphiphysin-Rvs (BAR) domain proteins are central regulators of many cellular processes involving membrane dynamics. BAR domains sculpt phosphoinositide-rich membranes to generate membrane protrusions or invaginations. Here, we report that, in addition to regulating membrane geometry, BAR domains can generate extremely stable lipid microdomains by "freezing" phosphoinositide dynamics. This is a general feature of BAR domains, because the yeast endocytic BAR and Fes/CIP4 homology BAR (F-BAR) domains, the inverse BAR domain of Pinkbar, and the eisosomal BAR protein Lsp1 induced phosphoinositide clustering and halted lipid diffusion, despite differences in mechanisms of membrane interactions...
September 26, 2013: Cell Reports
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