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Studium exprese MDR pump u kvasinek Saccharomyces cerevisiae za různých růstových podmínek: metoda s fluorescenční sondou diS-C3(3)
Zahumenský, Jakub ; Gášková, Dana (advisor) ; Krůšek, Jan (referee)
In this work, we studied two yeast ABC transporters, Pdr10p and Pdr15p. At the time of assignment of this thesis, it was believed that these proteins contribute to the yeast MDR phenotype (PDR) on the grounds of their high homology to another yeast MDR protein, Pdr5p. In order to study these pumps, two sets of isogenic null-mutant strains were prepared with all possible combinations of gene deletions. We report that both of the studied proteins are very important in sus- taining the normal plasma membrane microenvironment for the most abundant, and essential, yeast plasma membrane protein, H+ -ATPase and so influence the membrane potential. Pdr10p and Pdr15p thus play an as yet unknown role in reg- ulation of the activity of this enzyme. Furthermore, we report that deletion of the genes coding for these proteins severely reduces the ability of the H+ -ATPase to be activated by the protonophore CCCP which is a weak acid. Studies performed with immunosuppressant FK506 further show that this compound reduces the viability of S. cerevisiae mutant strain PLY643 lacking genes coding for Pdr5p, Snq2p and Yor1p. Further deletion of Pdr10p and Pdr15p does not increase the lethality of this compound. Neither CCCP nor FK506 are substrates of the stud- ied pumps. 1
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Calcium homeostasis and modulation of nociceptive synaptic transmission
Sojka, David ; Paleček, Jiří (advisor) ; Žurmanová, Jitka (referee) ; Krůšek, Jan (referee)
2 SUMMARY OF THE THESIS This study was designed to improve our knowledge regarding mechanisms of nociceptive signaling at spinal cord level. One of the forms of spinal cord synaptic transmission modulation is central sensitization, a manifestation of synaptic plasticity at spinal cord level, which was found to be present at many chronic pain syndromes. This study deals mainly with a development of calcium imaging technique with a final goal to study mechanisms of central sensitization in vitro on population of dorsal horn neurons. We have analyzed synaptically evoked intracellular Ca changes as a result of dorsal root stimulation in a superficial dorsal horn area in spinal cord slices and found two types of Ca responses: one synchronized with electrical stimulation and a second one, delayed response due to Ca release from internal stores. The delayed Ca release was not previously shown to be present in these neurons and it was not dependent on activation of ionotropic glutamatergic receptors, suggesting involvement of metabotropic receptor pathway. The presence of this delayed type of Ca response could have a significant role in the induction of some types of chronic pain syndromes since intracellular calcium increase is thought to be a key trigger point in spinal cord neurons sensitization. An important...
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Modulation of synaptic transmission, studies on spinal cord slices in vitro
Mrózková, Petra ; Paleček, Jiří (advisor) ; Krůšek, Jan (referee)
Modulation of a synaptic transmission in the spinal cord dorsal horn plays a key role in nociceptive signalling, especially in states of pathological pain. The goal of this study was to develop a method for calcium imaging in spinal cord slices in vitro. This method allowed us to record changes of intracellular free calcium ions concentration (iCa2+ ), that are a major mediator of neuronal plasticity. In this work, we have focused on application of this method in a conventional fluorescence microscope and on the role of different neuromodulators of synaptic activity. Changes of iCa2+ induced by dorsal root electrical stimulation were recorded altogether in 744 dorsal horn (lamina I and II) neurons. In the first series of experiments, stimulation protocols activating preferentially A and A + C dorsal root fibers were used and long-term stability of the calcium responses was verified. The dorsal root stimulation induced in the neurons fast and delayed type of calcium response. Application of AMPA and NMDA receptors antagonists, CNQX (50μM) and MK801 (45μM), reduced the calcium response amplitude and confirmed the importance of glutamate receptors in synaptic activation. In several experiments the effect of capsaicin a TRPV1 receptors agonist, application was tested. Application of even low...
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Biophysical studies of membrane transport proteins from Nramp/MntH family and their function
Ňuňuková, Věra ; Chaloupka, Roman (advisor) ; Krůšek, Jan (referee) ; Kubala, Martin (referee)
Three synthetic peptides corresponding to transmembrane segments TMS1, TMS3 and TMS6 of secondary-active transporter MntH from Escherichia coli were used as a suitable alternative model enabling to study TMS structure, TMS interaction with membranes, TMS mutual interaction and also function of MntH. The secondary structure of the peptides was estimated in different environments using circular dichroism spectroscopy. These peptides interacted with and adopted helical conformation in lipid membranes. Electrophysiological experiments demonstrated that individual TMS were able under certain conditions to form ion channels in model biological membranes. Electrophysiological properties of these weakly cation-selective ion channels were strongly dependent on surrounding pH. Manganese ion, as a physiological substrate of MntH, enhanced the conductivity of TMS1 and TMS6 channels, influenced the transition between closed and open states and affected the conformation of all studied peptides. For TMS3 Mn2+ was crucial for formation of ion channels. It was shown that a single functionally important TMS can retain some of the functional properties of the full-length protein. These findings can contribute to understanding of structure-function relationship at the molecular level. However, it remains unclear to what extent...
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The role of TRPV1 receptors in nociceptive signalling at spinal cord level
Mrózková, Petra ; Paleček, Jiří (advisor) ; Novotný, Jiří (referee) ; Krůšek, Jan (referee)
Modulation of nociceptive synaptic transmission in the spinal cord dorsal horn plays a key role in the development and maintenance of pathological pain states and chronic pain diseases. Important role in this process play Transient receptor potential Vanilloid 1 receptors (TRPV1), present on presynaptic endings of primary afferents in the superficial spinal cord dorsal horn. Changes in TRPV1 activity have significant impact on nociceptive transmission. There are number of processes that influence the function of spinal TRPV1 receptors. This work is focused on the role of protease-activated receptors type 2 (PAR2), C-C motif chemokine ligand 2 (CCL2) and the effect of chemotherapeutic drug paclitaxel in modulation of synaptic nociceptive transmission and activation of TRPV1 receptors. PAR2 receptors belong to a family of four G-protein-coupled receptors activated by proteases. The role of PAR2 receptors in pain perception is closely related to their presence in a population of dorsal root ganglion neurons, where they are also co-expressed with TRPV1. Activation of PAR2 may lead to peripheral and central sensitization. Chemokine CCL2 and its main receptor CCR2 were suggested to be an important factor in the development of neuropathic pain after peripheral nerve injury. In our study we focused on the...
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Study of the action of ivermectin on purinergic P2X4 receptor
Jelínková, Irena ; Teisinger, Jan (advisor) ; Šťastný, František (referee) ; Krůšek, Jan (referee)
The P2X4 receptor is ATP-gated cation channel. It is the only mamrnalian purinergic receptor which is modulated by extracellularly applied ivennectin (IVM). rVM is an allosteric modulator that has several effects on receptor [unction: it increases sensitivity to agonists, potentiates maximum current amplitude and prolongs the deactivation kinetics of the channel after agonist washout. The aim of this study was to localize IVM binding site and using its positive allosteric effect to get new inforrnatioll about the structure and function of P2X. receptor. Initially we focused on identification of regions and residues responsible for IVM effect on channel function. We used several chimeras of P2X2 and P2X. receptors and P2X. receptors with single point mutatioll. Experiments with chimeric receptors revealed that extracellular sequence V49-V61 but not tbe sequ nce V64-Y315 is important for the effects af IVM on channel deactivation. Receptor-specific alanine mutations placed in transmembrane domains 029-V61 and N338-L358 showed the importance of residues W50, V61 and V357 for TVM effect Oll channel deactivation. We tested further the irnportance of aH residues in transmembrane domains. Cysteine scanning mutagenesis supported the relevance of previously identified W50 residue and showed the importance ofresidues...
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