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Immunoassays are routinely used as research tools to measure intracellular cAMP and cGMP concentrations. Ideally, this application requires antibodies with high sensitivity and specificity. The present work evaluates the cross-reactivity of commercially available cyclic nucleotide analogs with two non-radioactive and one radioactive cAMP and cGMP immunoassay. Most of the tested cyclic nucleotide analogs showed low degree competition with the antibodies; however, with Rp-cAMPS, 8-Br-cGMP and 8-pCPT-cGMP, a strong cross-reactivity with the corresponding cAMP and cGMP, respectively, immunoassays was observed. The determined EIA-binding constants enabled the measurement of the intracellular cyclic nucleotide concentrations and revealed a time- and lipophilicity-dependent cell membrane permeability of the compounds in the range of 10–30% of the extracellular applied concentration, thus allowing a more accurate prediction of the intracellular analog levels in a given experiment.
Die Funktion eines Genes zu erforschen, indem man es ausschaltet, und damit seiner Rolle im komplexen Zusammenspiel der einzelnen Prozesse des menschlichen Körpers nachzugehen, stellt heutzutage eines der vielversprechendsten Felder der Gentechnologie dar.
Der als RNA-Interferenz bekannte Mechanismus wurde in dieser Arbeit durch den Einsatz von sogenannten short hairpin RNAs (shRNAs), dauerhaft in das Wirtsgenom integrierter Knockdown-Träger, für das Gen bzw. Protein Y box binding Protein (YBX1) angewendet.
YBX1, ein Vertreter der Cold-Shock-Proteine, stellt einen zentralen Interakteur lebensnotwendiger Prozesse wie Proliferation, Apoptose und Embryogenese im menschlichen Körper dar. Seine Dysregulation wird jedoch auch in einen Zusammenhang mit Entzündung, Tumorformation und –aufrechterhaltung gebracht, unter anderem auch für das Multiple Myelom.
Das Multiple Myelom ist für 1% aller Krebserkrankungen weltweit verantwortlich mit noch immer ungelösten Problemen unzulänglicher Therapie und deletärer Prognose.
In der vorliegenden Arbeit wurde die Möglichkeit geschaffen, die Rolle von YBX1 für das Multiple Myelom mit Hilfe einer Maus-Plasmazelllinie in vivo zu untersuchen. Dies geschah durch die Suppression der Genexpression von YBX1 mittels verschiedener gegen YBX1 gerichteter Polymerase II-getriebener short hairpin RNAs (shRNAs). Diese wurden in ein lentivirales Plasmid kloniert. Durch das Vorhandensein von Tetrazyklin induzierbaren Promotoren (Tet-On bzw. Tet-Off) wurde die Möglichkeit geschaffen, einen konditionellen Knockdown von YBX1 zu induzieren. Dies war notwendig, da initiale Arbeiten mit humanen Myelomzelllinien zeigten, dass der Knockdown von YBX1 Apoptose induzieren kann. Mit diesem Konstrukt wurden in HEK293 Zellen lentivirale Partikel hergestellt und damit die murine Plasmozytomzelle MOPC315.BM stabil transduziert. Nach Selektion, Klonierung und Testung (Puromycin-Selektion, RFP-Expression und Western-Blot Analyse) stand ein Zellklon zur Verfügung, der einen induzierbaren YBX1 Knockdown zeigt.
Damit gelang die Etablierung eines gegen YBX1 gerichteten Vektorsystems in einer murinen Plasmazellinie in vitro. Mit Hilfe dieser Zelllinien kann nun in weiteren Arbeiten untersucht werden, wie ein YBX1 Knockdown das Tumorwachstum in vivo beinflusst.
Background: Hemostasis is a critical and active function of the blood mediated by platelets. Therefore, the prevention of pathological platelet aggregation is of great importance as well as of pharmaceutical and medical interest. Endogenous platelet inhibition is predominantly based on cyclic nucleotides (cAMP, cGMP) elevation and subsequent cyclic nucleotide-dependent protein kinase (PKA, PKG) activation. In turn, platelet phosphodiesterases (PDEs) and protein phosphatases counterbalance their activity. This main inhibitory pathway in human platelets is crucial for countervailing unwanted platelet activation. Consequently, the regulators of cyclic nucleotide signaling are of particular interest to pharmacology and therapeutics of atherothrombosis. Modeling of pharmacodynamics allows understanding this intricate signaling and supports the precise description of these pivotal targets for pharmacological modulation. Results: We modeled dynamically concentration-dependent responses of pathway effectors (inhibitors, activators, drug combinations) to cyclic nucleotide signaling as well as to downstream signaling events and verified resulting model predictions by experimental data. Experiments with various cAMP affecting compounds including antiplatelet drugs and their combinations revealed a high fidelity, fine-tuned cAMP signaling in platelets without crosstalk to the cGMP pathway. The model and the data provide evidence for two independent feedback loops: PKA, which is activated by elevated cAMP levels in the platelet, subsequently inhibits adenylyl cyclase (AC) but as well activates PDE3. By multi-experiment fitting, we established a comprehensive dynamic model with one predictive, optimized and validated set of parameters. Different pharmacological conditions (inhibition, activation, drug combinations, permanent and transient perturbations) are successfully tested and simulated, including statistical validation and sensitivity analysis. Downstream cyclic nucleotide signaling events target different phosphorylation sites for cAMP- and cGMP-dependent protein kinases (PKA, PKG) in the vasodilator-stimulated phosphoprotein (VASP). VASP phosphorylation as well as cAMP levels resulting from different drug strengths and combined stimulants were quantitatively modeled. These predictions were again experimentally validated. High sensitivity of the signaling pathway at low concentrations is involved in a fine-tuned balance as well as stable activation of this inhibitory cyclic nucleotide pathway. Conclusions: On the basis of experimental data, literature mining and database screening we established a dynamic in silico model of cyclic nucleotide signaling and probed its signaling sensitivity. Thoroughly validated, it successfully predicts drug combination effects on platelet function, including synergism, antagonism and regulatory loops.
Preclinical studies point to a pivotal role of the orexin 1 (OX1) receptor in arousal and fear learning and therefore suggest the HCRTR1 gene as a prime candidate in panic disorder (PD) with/without agoraphobia (AG), PD/AG treatment response, and PD/AG-related intermediate phenotypes. Here, a multilevel approach was applied to test the non-synonymous HCRTR1 C/T Ile408Val gene variant (rs2271933) for association with PD/AG in two independent case-control samples (total n = 613 cases, 1839 healthy subjects), as an outcome predictor of a six-weeks exposure-based cognitive behavioral therapy (CBT) in PD/AG patients (n = 189), as well as with respect to agoraphobic cognitions (ACQ) (n = 483 patients, n = 2382 healthy subjects), fMRI alerting network activation in healthy subjects (n = 94), and a behavioral avoidance task in PD/AG pre- and post-CBT (n = 271). The HCRTR1 rs2271933 T allele was associated with PD/AG in both samples independently, and in their meta-analysis (p = 4.2 × 10−7), particularly in the female subsample (p = 9.8 × 10−9). T allele carriers displayed a significantly poorer CBT outcome (e.g., Hamilton anxiety rating scale: p = 7.5 × 10−4). The T allele count was linked to higher ACQ sores in PD/AG and healthy subjects, decreased inferior frontal gyrus and increased locus coeruleus activation in the alerting network. Finally, the T allele count was associated with increased pre-CBT exposure avoidance and autonomic arousal as well as decreased post-CBT improvement. In sum, the present results provide converging evidence for an involvement of HCRTR1 gene variation in the etiology of PD/AG and PD/AG-related traits as well as treatment response to CBT, supporting future therapeutic approaches targeting the orexin-related arousal system.