TY - JOUR A1 - Koenig, Sebastian A1 - Wolf, Reinhard A1 - Heisenberg, Martin T1 - Visual Attention in Flies-Dopamine in the Mushroom Bodies Mediates the After-Effect of Cueing JF - PLoS ONE N2 - Visual environments may simultaneously comprise stimuli of different significance. Often such stimuli require incompatible responses. Selective visual attention allows an animal to respond exclusively to the stimuli at a certain location in the visual field. In the process of establishing its focus of attention the animal can be influenced by external cues. Here we characterize the behavioral properties and neural mechanism of cueing in the fly Drosophila melanogaster. A cue can be attractive, repulsive or ineffective depending upon (e.g.) its visual properties and location in the visual field. Dopamine signaling in the brain is required to maintain the effect of cueing once the cue has disappeared. Raising or lowering dopamine at the synapse abolishes this after-effect. Specifically, dopamine is necessary and sufficient in the αβ-lobes of the mushroom bodies. Evidence is provided for an involvement of the αβ\(_{posterior}\) Kenyon cells. KW - dopamine transporters KW - Drosophila melanogaster KW - synapses KW - dopaminergics KW - dopamine KW - sensory cues KW - RNA interference KW - vision Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-179564 VL - 11 IS - 8 ER - TY - THES A1 - Blachutzik, Jörg O. T1 - Visualisierung von Plasmamembran-Domänen in Arabidopsis thaliana T1 - Visualization of plasma membrane domains in Arabidopsis thaliana N2 - Unter Verwendung fluoreszenzmarkierter Remorine der taxonomischen Gruppe 1b wurden Nanodomänen in Arabidopsis Plasmamembranen (PM) unter Verwendung hoch auflösender Laser Scanning-Systeme sichtbar gemacht. In diesen kompartimentierten Membranbereichen lagerten sich Sterol-abhängige Remorine aus verschiedenen Pflanzen-familien zusammen und zeigten dort Kolokalisation. Dies wurde statistisch belegt durch hohe Pearson und Spearman Korrelationskoeffizienten. Remorine konnten schließlich als pflanzliche Markerproteine für kompartimentierte Membranbereiche etabliert werden. Die Nanodomänen zeigten zu keinem Zeitpunkt laterale Bewegungen in der PM und scheinen sowohl von zytoskelettären Strukturen als auch von Komponenten der Zellwand stabilisiert zu werden. Möglicherweise spielen transmembrane Tetraspanine sowie GPI-verankerte SKU5-Proteine eine Rolle bei der stabilen Verankerung. Für zwei native Arabidopsis Remorine wurden posttranslationale Modifikationsstellen aufgedeckt, die der Anheftung dieser hydrophilen Proteine an die PM dienen. Weiterhin scheinen gleichartige Remorine miteinander zu interagieren. Beispielsweise waren im Zytosol lokalisierte Remorin-Mutanten bei einer gleichzeitigen Expression der entsprechenden Vollängenproteine erneut an der PM zu finden. Für die Remorine wurde postuliert, dass sie mit anderen Proteinen interagieren und dabei makromolekulare Strukturen ausbilden. Den Remorinen könnte daher eine Aufgabe bei der molekularen Organisation pflanzlicher Membrandomänen zukommen, indem sie ein filamentartiges Netzwerk innerhalb distinkter Domänen ausbilden, das möglicherweise zur Stabilität und Aufrechterhaltung dieser spezialisierten Bereiche beiträgt. Unter Einbeziehung der STED-Mikroskopie wurde eine empirische Größenverteilung von 97±4nm Durchmesser für PM-ständige Domänen in Arabidopsis ermittelt. Hinsichtlich der physiologischen Relevanz konnte gezeigt werden, dass die Domänen eine Rolle bei der ABA-vermittelten, kalziumabhängigen Regulation des Anionenkanals SLAH3 einnehmen. SLAH3 wird durch kalziumabhängige Kinasen aus der CDPK-Familie aktiviert, im Speziellen durch CPK21 und CPK23. Beide Kinasen werden durch die ABA-sensitiven Phosphatasen ABI1 und ABI2 reguliert. Die spezifisch stattfindenden Interaktionen zwischen SLAH3 und CPK21, sowie zwischen CPK21 und ABI1 waren auf Nanodomänen beschränkt und wurden durch die Methodik der bimolekularen Fluoreszenzkomplementation erstmals in planta nachgewiesen, mit Remorinen der taxonomischen Gruppe 1b als etablierte Markerproteine für Membrandomänen. N2 - In this work, membrane nanodomains have been visualized in planta via confocal microscopy of group 1b Remorin proteins fused to fluorescent proteins. Within these nanodomains, sterol-dependent Remorins originating from different plant species accumulated as shown by multiple color colocalization microscopy, and through which it was statistically verified by high Spearman and Pearson correlation coefficients. Thus, group 1b Remorins were established here as reliable marker proteins for plasma membrane (PM) nanodomains in plants. Since individual domains did not exhibit any kind of lateral movement within the plane of the membrane, a stabilization of them from cytoskeletal components as well as from components of the cell wall was presumed. Other proteins such as trans-membrane Tetraspanins and GPI-anchored proteins like SKU5 were ruled out as possible candidates being involved in the maintenance of domains´ lateral stability. For two Remorins originating from Arabidopsis thaliana, sites of posttranslational lipid modifications, which allow the proteins to anchor to the plasma membrane, were revealed. In experiments using truncated Remorins with these modification sites deleted, the mutant Remorins appeared to be no longer located at the PM but rather within the cytosol. Truncated Remorins re-appeared at the PM as soon as the full length Remorin proteins were co-expressed. In close proximity to the sites of lipid modifications a highly conserved C-terminal region, whose likely role is to facilitate homo-Remorin protein interactions, was uncovered. Therefore Remorins could possibly be involved in the molecular organization of a filamentous protein structure that could help mediate the stability and maintenance of individual domains. As well, the sizes of individual nanodomains were empirically measured in Arabidopsis thaliana mesophyll cells with STED microscopy, which allowed for optical measurements of domains with 60nm resolution, and were narrowly distributed in a histogram of domain diameters with an average diameter of 97 ± 4nm. One possible physiological role of PM-based nanodomains was demonstrated to be the ABA-mediated, calcium-dependent regulation of the SLAH3 anion channel. At the inception of the regulation, SLAH3 becomes activated upon phosphorylation by calcium-dependent protein kinases of the CDPK-family, CPK21 and CPK23. Both CPK´s in turn are regulated by the ABA-dependent phosphatases ABI1 and ABI2. As visualized by fluorescence colocalization microscopy for the first time, the interactions between SLAH3 and CPK21, as well as interactions between CPK21 and ABI1 were restricted to PM compartments. As well, these protein interactions were corroborated by also imaging them in planta using the bimolecular fluorescence complementation technique - involving group 1b Remorins as the established marker proteins for PM nanodomains. KW - Plasmamembran KW - Fluoreszmikroskopie KW - Ackerschmalwand KW - plasma membrane KW - fluorescence microscopy KW - Remorin KW - protoplasts KW - Protoplasten Y1 - 2012 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-71925 ER - TY - THES A1 - Gromova, Kira V. T1 - Visualization of the Smad direct signaling response to Bone Morphogenetic Protein 4 activation with FRET-based biosensors T1 - Visualisierung der Smad-vermittelten Signaltransduktion nach Aktivierung mit "Bone Morphogenetic Protein" 4 mittels FRET-basierter Biosensoren N2 - The Transforming Growth Factor (TGF) superfamily of cytokines and their serine/threonine kinase receptors play an important role in the regulation of cell division, differentiation, adhesion, migration, organization, and death. Smad proteins are the major intracellular signal transducers for the TGF receptor superfamily that mediate the signal from the membrane into the nucleus. Bone Morphogenetic Protein-4 (BMP-4) is a representative of the TGF superfamily, which regulates the formation of teeth, limbs and bone, and also plays a role in fracture repair. Binding of BMP-4 to its receptor stimulates phosphorylation of Smad1, which subsequently recruits Smad4. A hetero-oligomeric complex consisting of Smad1 and Smad4 then translocates into the nucleus and regulates transcription of target genes by interacting with transcription factors. Although the individual steps of the signaling cascade from the receptor to the nucleus have been identified, the exact kinetics and the rate limiting step(s) have remained elusive. Standard biochemical techniques are not suitable for resolving these issues, as they do not offer sufficiently high sensitivity and temporal resolution. In this study, advanced optical techniques were used for direct visualization of Smad signaling in live mammalian cells. Novel fluorescent biosensors were developed by fusing cyan and yellow fluorescent proteins to the signaling molecules Smad1 and Smad4. By measuring Fluorescence Resonance Energy Transfer (FRET) between the two fluorescent proteins, the kinetics of BMP/Smad signaling was unraveled. A rate-limiting delay of 2 - 5 minutes occurred between BMP receptor stimulation and Smad1 activation. A similar delay was observed in the complex formation between Smad1 and Smad4. Further experimentation indicated that the delay is dependent on the Mad homology 1 (MH1) domain of Smad1. These results give new insights into the dynamics of the BMP receptor – Smad1/4 signaling process and provide a new tool for studying Smads and for testing inhibitory drugs. N2 - Die Transforming Growth Factor" (TGF)-Superfamilie der Cytokine und ihrer Serin/Threonin-Kinase-Rezeptoren spielt eine bedeutende Rolle bei der Regulierung der Zellteilung, -differenzierung, -adhäsion, -migration, -organisation, und beim Zelltod. Die Smad-Proteine sind die wichtigsten intrazellulären Signalüberträger für die TGF-Rezeptor-Familie, da sie das Signal von der Zellmembran zum Kern übermitteln. Das ,,Bone Morphogenetic Protein4" (BMP-4) ist ein Vertreter der TGF-Familie, der die Bildung von Zähnen, Gliedmaßen und Knochen reguliert und darüber hinaus eine Rolle bei der Frakturheilung spielt. Das Binden von BMP-4 an seinen Rezeptor stimuliert die Phosphorylierung von Smad1, welches in der Folge Smad4 rekrutiert. Ein hetero-oligomerer Komplex bestehend aus Smad1 und Smad4 verlagert sich dann in den Zellkern, wo er durch Interaktion mit Transkriptionsfaktoren die Transkription von Zielgenen reguliert. Obwohl die einzelnen Schritte der Signalkaskade vom Rezeptor bis in den Zellkern bereits identifiziert wurden, blieben die Kinetik und die geschwindigkeitsbegrenzenden Schritte bisher unbekannt. Gängige biochemische Methoden eignen sich nicht um diese Fragen zu lösen, da sie nicht über ausreichende Empfindlichkeit und zeitliches Auflösungsvermögen verfügen. In der vorliegenden Arbeit wurden hochentwickelte optische Techniken angewandt, um die Smad-vermittelte Signaltransduktion direkt in lebenden Zellen sichtbar zu machen. Neue fluoreszierende Biosensoren wurden konstruiert, indem gelb- und cyan-fluoreszierende Proteine mit den Signalmoleküle Smad1 und Smad4 fusioniert wurden. Durch Messung des "Fluorescent Resonance Energy Transfer" (FRET) zwischen den zwei fluoreszierenden Proteinen konnte die Kinetik der BMP-Smad-Signalkaskade bestimmt werden. Zwischen der Stimulation des Rezeptors und der Aktivierung von Smad1 trat eine geschwindigkeitsbegrenzende Verzögerung von 2-5 Minuten auf. Eine ähnliche Verzögerung wurde bei der Bildung des Komplexes aus Smad1 und Smad4 beobachtet. Weitere Experimente zeigten, dass die Verzögerung von der Mad-Homologie-Domäne 1 (MH1) von Smad1 abhängt. Die Ergebnisse dieser Arbeit geben neue Einblicke in die Dynamik der BMP-Rezeptor-Smad1/4 Signaltransduktion und stellen neue Werkzeuge zur Untersuchung von Smads und zur Austestung inhibitorischer Wirkstoffe zur Verfügung. KW - FRET KW - Mikroskopie KW - Signaltransduktion KW - Smad KW - BMP KW - FRET KW - microscopy KW - signaling KW - Smad KW - bone morphogenetic protein KW - fluorescent protein Y1 - 2007 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-25855 ER - TY - JOUR A1 - Kraft, Peter A1 - Drechsler, Christiane A1 - Gunreben, Ignaz A1 - Nieswandt, Bernhard A1 - Stoll, Guido A1 - Heuschmann, Peter Ulrich A1 - Kleinschnitz, Christoph T1 - Von Willebrand Factor Regulation in Patients with Acute and Chronic Cerebrovascular Disease: A Pilot, Case-Control Study JF - PLoS ONE N2 - Background and Purpose In animal models, von Willebrand factor (VWF) is involved in thrombus formation and propagation of ischemic stroke. However, the pathophysiological relevance of this molecule in humans, and its potential use as a biomarker for the risk and severity of ischemic stroke remains unclear. This study had two aims: to identify predictors of altered VWF levels and to examine whether VWF levels differ between acute cerebrovascular events and chronic cerebrovascular disease (CCD). Methods A case–control study was undertaken between 2010 and 2013 at our University clinic. In total, 116 patients with acute ischemic stroke (AIS) or transitory ischemic attack (TIA), 117 patients with CCD, and 104 healthy volunteers (HV) were included. Blood was taken at days 0, 1, and 3 in patients with AIS or TIA, and once in CCD patients and HV. VWF serum levels were measured and correlated with demographic and clinical parameters by multivariate linear regression and ANOVA. Results Patients with CCD (158±46%) had significantly higher VWF levels than HV (113±36%, P<0.001), but lower levels than AIS/TIA patients (200±95%, P<0.001). Age, sex, and stroke severity influenced VWF levels (P<0.05). Conclusions VWF levels differed across disease subtypes and patient characteristics. Our study confirms increased VWF levels as a risk factor for cerebrovascular disease and, moreover, suggests that it may represent a potential biomarker for stroke severity, warranting further investigation. KW - cerebrovascular diseases KW - sex addiction KW - biomarkers KW - ischemic stroke KW - blood KW - stroke KW - platelets KW - demography Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-119588 SN - 1932-6203 VL - 9 IS - 6 ER - TY - JOUR A1 - Mammadova-Bach, Elmina A1 - Braun, Attila T1 - Zinc homeostasis in platelet-related diseases JF - International Journal of Molecular Sciences N2 - Zn\(^{2+}\) deficiency in the human population is frequent in underdeveloped countries. Worldwide, approximatively 2 billion people consume Zn\(^{2+}\)-deficient diets, accounting for 1–4% of deaths each year, mainly in infants with a compromised immune system. Depending on the severity of Zn\(^{2+}\) deficiency, clinical symptoms are associated with impaired wound healing, alopecia, diarrhea, poor growth, dysfunction of the immune and nervous system with congenital abnormalities and bleeding disorders. Poor nutritional Zn\(^{2+}\) status in patients with metastatic squamous cell carcinoma or with advanced non-Hodgkin lymphoma, was accompanied by cutaneous bleeding and platelet dysfunction. Forcing Zn\(^{2+}\) uptake in the gut using different nutritional supplementation of Zn\(^{2+}\) could ameliorate many of these pathological symptoms in humans. Feeding adult rodents with a low Zn\(^{2+}\) diet caused poor platelet aggregation and increased bleeding tendency, thereby attracting great scientific interest in investigating the role of Zn\(^{2+}\) in hemostasis. Storage protein metallothionein maintains or releases Zn\(^{2+}\) in the cytoplasm, and the dynamic change of this cytoplasmic Zn\(^{2+}\) pool is regulated by the redox status of the cell. An increase of labile Zn\(^{2+}\) pool can be toxic for the cells, and therefore cytoplasmic Zn\(^{2+}\) levels are tightly regulated by several Zn\(^{2+}\) transporters located on the cell surface and also on the intracellular membrane of Zn\(^{2+}\) storage organelles, such as secretory vesicles, endoplasmic reticulum or Golgi apparatus. Although Zn\(^{2+}\) is a critical cofactor for more than 2000 transcription factors and 300 enzymes, regulating cell differentiation, proliferation, and basic metabolic functions of the cells, the molecular mechanisms of Zn\(^{2+}\) transport and the physiological role of Zn\(^{2+}\) store in megakaryocyte and platelet function remain elusive. In this review, we summarize the contribution of extracellular or intracellular Zn\(^{2+}\) to megakaryocyte and platelet function and discuss the consequences of dysregulated Zn\(^{2+}\) homeostasis in platelet-related diseases by focusing on thrombosis, ischemic stroke and storage pool diseases. KW - Zinc KW - platelets KW - hemostasis KW - thrombosis KW - ischemic stroke KW - storage-pool diseases Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-285554 SN - 1422-0067 VL - 20 IS - 21 ER -