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Metabotropic glutamate receptors: mechanism of activation
Hlaváčková, Veronika ; Blahoš, Jaroslav (advisor) ; Vyklický, Ladislav (referee) ; Martásek, Pavel (referee) ; Konvalinka, Jan (referee)
Any living organism receives constantly many signals that have to be evaluated and weighted to respond in an appropriate way. To perform all functions needed for precise control of homeostasis and for communication with the surrounding environment, signals coming from the outside are recognized and transferred into modulation of intracellular signaling cascades. These mediate response to the extracellular stimulus as well as intercellular communication. Cell communication is mediated by several types of receptors, located either intracellularly (including nuclear receptors) that modulate gene transcription and receptors localized on plasma membrane. Cell membrane receptors are transmembrane proteins that are divided into three superfamilies according to their structure and principles of signal transduction. These are ion channel-linked receptors, enzyme-linked receptors and G-protein-coupled receptors (GPCRs). GPCRs comprise the biggest family of membrane receptors and are one of the largest gene families in general. They are encoded by about 1% of genes in mammals. Many of them bind sensory ligands (rhodopsin, taste and olfactory receptors), but others also recognize ions, amino acids, nucleotides, peptides and large glycoproteins (1). They play a crucial role in such distant physiological functions as...
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Ionotropic glutamate receptors and excitotoxicity
Skřenková, Kristýna ; Vyklický, Ladislav (advisor) ; Moravec, Jan (referee)
Glutamate is the major excitatory neurotransmitter in the mammalian central nervous system and its excitatory role is mediated trough activation of glutamatergic ionotropic receptors which are responsible for synaptic transmission and play an important role in learning and memory formation. However, excessive exposure to glutamate can result in excitotoxicity which may lead to cell death. The following text is focused on one group of glutamate receptors - NMDA receptors. The study of the receptors is in the centre of current neurobiology research because there is a series of experimental and clinical evidences that they directly participate in the development of serious diseases such as Alzheimer's disease, Parkinson's disease, Huntington's disease and may cause neuronal damage in trauma, hypoxia and embolia. The aim of this bachelor thesis is to give a brief overview of current knowledge about the structure and function of NMDA receptors and mechanisms of their activation which leads to excitotoxicity and related neuroprotection.
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The study of functional and molecular properties of NMDA receptors
Vyklický, Vojtěch ; Vyklický, Ladislav (advisor) ; Chvátal, Alexandr (referee) ; Tureček, Rostislav (referee)
N-methyl-D-aspartate (NMDA) receptors are a subtype of ionotropic glutamate receptors, which mediate fast synaptic transmission in the vertebrate central nervous system and play a key role in synaptic plasticity. NMDA receptor overexcitation leads to cell death that underlies many serious neurological and psychiatric disorders. The aim of our research was to characterize novel drugs that modulate NMDAR activity. We have tested a series of newly synthesized steroidal compounds for their activity on recombinant receptors. We have demonstrated a relationship between the structure of the analogues of a naturally occurring neurosteroid pregnanolone sulfate and their ability to modulate NMDA receptors. The results of our experiments characterize the role of substituents at the steroid A and D ring. We have found specific substituents on carbons C3 and C17 of the steroidal skeleton that lead to a substantial increase of steroid efficacy and the ability to positively affect the ratio between the inhibition of stationary and non-stationary receptor activation. These two states represent receptors long-term activated (tonically) and synaptically activated (phasically), respectively. Using electrophysiological and optical methods in combination with mathematical modeling we have shown that the plasma membrane plays an...
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Multiple regulatory roles of the transmembrane adaptor protein NTAL in gene transcription and mast cell physiology
Polakovičová, Iva ; Dráber, Petr (advisor) ; Vyklický, Ladislav (referee) ; Hašek, Jiří (referee)
(EN) This thesis focuses mainly on understanding of the regulatory roles of the transmembrane adaptor proteins, non-T cell activation linker (NTAL) and phosphoprotein associated with glycosphingolipid-enriched microdomains (PAG), in murine mast cell signaling. There are conflicting reports on the role of NTAL in the high affinity immunoglobulin E receptor (FcεRI) activation pathways in mast cells. Studies carried out on mast cells prepared from NTAL knock-out mice have indicated that NTAL is a negative regulator of FcεRI signaling, whereas experiments performed on human mast cells and rat basophilic leukemia cells with silenced NTAL expression have suggested its positive regulatory role. To thoroughly examine the involvement of NTAL in FcεRI-mediated signaling events in mouse mast cells and to determine whether different methodologies of NTAL ablation have different physiological consequences, we utilized a broad range of assays. Using bone marrow-derived mast cells (BMMCs) as a model, we obtained cells from NTAL wild type and knock-out cells and using lentiviral delivery approach we transduced part of the wild type cells, with vector bearing NTAL shRNA or empty vector to generate NTAL knock-down cells and control cells, respectively. Comparison of all four groups of generated cells in our assays...
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Membrane Properties of Glial Cells after Ischemia in vivo
Pivoňková, Helena ; Anděrová, Miroslava (advisor) ; Vyklický, Ladislav (referee) ; Vlachová, Viktorie (referee)
In my PhD thesis, I aimed to characterize the membrane properties of astrocytes and NG2 glia during the acute and chronic phases of the ischemic injury in the central nervous system with a focus on the expression and activity of K+ ion channels. Two ischemia models in rats were used for the experiments - global cerebral ischemia 5 causing selective neuronal loss and astrogliosis in the CA1 region of the hippocampus, and incubation of spinal cord segments in a solution with high K+ concentration. We found that hippocampal astrocytes depolarize starting 3 days after ischemia, and demonstrate an increase in the inward rectification of their whole cell currents 1 month after ischemia. The Kir4.1 channel expression in the hippocampal tissue was downregulated starting 3 days after ischemia, while the expression of Kir2.1, Kir5.1 and TREK1 channels was strongly upregulated in reactive astrocytes 1 month after ischemia. NG2 glia displayed a significant increase in the outwardly rectifying delayed and A-type K+ (KDR and KA) currents 2 hours and 3 days after ischemia, and a decrease in the inwardly rectifying K+ currents 3 days after ischemia, a typical current pattern of proliferating cells. Complex astrocytes in the spinal cord pre-incubated in a solution with high [K+] showed the largest changes in their membrane...
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mmunohistochemical analysis of the inhibitory glycine and GABAB receptors in the MNTB
Trojanová, Johana ; Tureček, Rostislav (advisor) ; Druga, Rastislav (referee) ; Vyklický, Ladislav (referee)
Properties of glycine (GlyR) and GABAB (GABABR) receptors were studied in the adult rat medial nucleus of the trapezoid body (MNTB). MNTB belongs among brainstem auditory nuclei. Prevailing cell type in the MNTB is the principal cell (PC). Each PC receives two types of synaptic inputs. Excitatory input originating at contralateral anteroventral cochlear nucleus (AVCN), forms a giant glutamatergic nerve terminal, calyx of Held (CH). Inhibitory inputs are brought by glycinergic and GABAergic fibers of unclear origin. Synaptically released GABA and glycine modulate excitatory synaptic transmission in MNTB via receptors expressed by presynaptic and postsynaptic neurons. The goal of our work was to elucidate both the subcellular distribution and subunit composition of the receptors, thereby extend our knowledge of the function of the receptors in the MNTB. We used immunohistochemical staining methods. The receptors were labelled by specific antibodies localized in the nervous tissue by means of fluorescence or electron microscopy. The experimental work consisted of three phases. During the first phase we revealed that GlyRs in the MNTB form two distinct populations. Postsynaptic receptors form α1β heteromeric clusters on somatodendritic parts of PCs. These clusters colocalize with glycinergic endings...
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Characterization of molecular components in cannabinoid signaling pathways.
Hájková, Alena ; Blahoš, Jaroslav (advisor) ; Vyklický, Ladislav (referee) ; Maletínská, Lenka (referee)
The cannabinoid receptor 1 (CB1R), a member of the G-protein coupled receptors superfamily, is a key player in endocannabinoid signalling. The CB1R is found presynaptically in neurones where it modulates synaptic plasticity. Precise description of the molecular mechanisms of synaptic neurotransmission is crucial for understanding of brain diseases and development of new therapeutic aproaches. Possible pharmacological targets of CB1R signalling include the treatment of various ailments such as energy imbalance disorders (anorexia, obesity), drug addiction, pain, insomnia, and some psychiatric conditions. This study reveals the "Src homology 3-domain growth factor receptor-bound 2-like (endophilin) interacting protein 1" (SGIP1) as a novel interacting partner of the CB1R. The SGIP1 is an intracellular neuronal protein localized predominantly in axon terminals and is involved in clathrin mediated endocytosis. The overexpression of SGIP1 imbalance energy homeostasis and leads to obesity. We show that SGIP1 affects CB1R signalling via ERK1/2 whereas G-protein signallization remains unaltered. The SGIP1 also hinders CB1R internalization from the cell surface and supports its interaction with β-arrestin2. Also, we demonstrated heterodimerization of the main splice variants of metabotropic glutamate...
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Functional role of purinergic P2X receptors in the supraoptic nuclei of the rat and structure-function relations of recombinant P2X receptors.
Vávra, Vojtěch ; Zemková, Hana (advisor) ; Novák, František (referee) ; Vyklický, Ladislav (referee)
Purinergic P2X receptors are non-selective cationic channels gated by extracellular ATP. Up to now, seven mammalian subunits, termed P2X1-X7, have been cloned and characterized. These receptors comprise a new membrane channel family with distinct structural and functional features. P2X receptors take part in a signalling network called "purinergic signalling" which is widely exploited in both somatic and neuronal tissues. In the central nervous system, they are highly expressed in the hypothalamus and hypophysis, where they participate in the regulation of homeostatic and reproductional functions. The main focus of my Thesis is on the expression and functional role of P2X receptors in supraoptic nuclei of the rat hypothalamus. These nuclei contain two populations of magnocellular neurons which produce either oxytocin or arginine-vasopressin. Delivery of the hormones into the systemic blood relies on the electrical activity of supraoptic neurons, which is in turn governed by the incomming synaptic inputs. It has been recently shown, that the process of hormone release from supraoptic neurons is regulated by extracellular ATP. However, purinergic signals that regulate hormone secretion are not well understood. The aim of my study was to identify subtypes of P2X receptors expressed in the supraoptic...
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Study of functional and pharmacological properties of NMDA receptors
Hubálková, Pavla ; Vyklický, Ladislav (advisor) ; Horáček, Jiří (referee) ; Novotný, Jiří (referee)
Pavla Hubalkova Doctoral study program: Neuroscience, 2021 Doctoral thesis: Study of functional and pharmacological properties of NMDA receptors ABSTRACT N-methyl-D-aspartate (NMDA) receptors are a subtype of ionotropic glutamate receptors crucial for synaptic transmission and learning and memory processes. After activation and opening of the ion channel, they are permeable to calcium ions (Ca2+ ) that mediate further signaling. Hypo- or hyperfunction of NMDA receptors leads to the development of severe neurological and psychiatric diseases. NMDA receptors are modulated by many endogenous and exogenous substances. These include neurosteroids - steroids synthesised de novo in the central nervous system and their synthetic analogues, which, depending on their structure, can have positive or negative modulatory effects. Using electrophysiological and molecular-biological techniques, we have clarified the molecular mechanism of increased sensitivity of NMDA receptors to inhibitory neurosteroids following a transient increase in intracellular Ca2+ concentration. The increase in neurosteroid inhibitory activity at NMDA receptors is related to Ca2+ -induced depalmitoylation of three cysteines (C849, C854, C871) in the intracellular part of the GluN2B subunit. This simultaneously leads to a change in the receptor's...
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