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Incidence and role of the purinergic P2X7 receptor in the immune system
Piskačová, Kateřina ; Zemková, Hana (advisor) ; Červená, Kateřina (referee)
It has been shown recently that extracellular ATP and its metabolite adenosine are key mediators in the immune system. Depending on the concentration, ATP may act as an activator or an inhibitor to the immune response, whereas adenosine is generally well known as a specific immunosupressor. Signals delivered by extracellular ATP and adenosine are detected and transduced by purinergic P2- and P1- receptors, respectively. In principle, all cells of the immune system express P2X, P2Y and adenosine P1 receptors on their plasmatic membrane. Therefore, the purinergic signaling extends to all components of the immune and inflammatory responses, including neurodegenerative diseases. This knowledge triggered a wave of interest in research, development and synthesis of new compounds having effect on P1- and P2- receptors that could help in the treatment of chronic inflammatory diseases and neurodegenerative diseases. This bachelor thesis will summarize the most recent knowledge on the role of the P2X7 receptor in these processes. This subtype of P2-receptor is unique because it is involved in the release of cytokines from immune cells and plays a role in the cell growth and apoptosis.
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Expression of AMPA glutamate receptor subunits in the suprachiasmatic nucleus of the rat
Červená, Kateřina ; Bendová, Zdeňka (advisor) ; Zemková, Hana (referee)
The main mammalian circadian pacemaker stored in suprachiasmatic nuclei of the hypothalamus (SCN) is adapted to changes in the external environement by synchronization of its endogenous period with periodic changes of light and dark during day and night. The information about light travels via glutamatergic retinohypothalamic tract to the ventrolateral part of the SCN. Activation of ionotropic glutamate receptors in this area provably mediates the transfer of information about light on the transcriptional mechanism of light-sensitive cells. The role of the NMDA type of ionotropic glutamate receptors is well studied in this field and it is known that some NMDA receptor subunits show a circadian rhythm and an increased expression after a light pulse. Signalization via AMPA type receptors is much less elucidated. The aim of this thesis was to determine which AMPA receptor subunits are expressed in the SCN of the rat and if these subunits show a daily rhythm of expression and a reactivity to light pulse, as well as to outline the possible roles of distinct AMPA receptor subunits in the SCN. Keywords: circadian rhythms, suprachiasmatic nuclei, glutamate receptors, AMPA
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Modulatory mechanisms of nociceptive TRP channels
Maršáková, Lenka ; Vlachová, Viktorie (advisor) ; Novotný, Jiří (referee) ; Zemková, Hana (referee)
Detection of painful stimuli in the periphery is mediated by temperature-sensitive transient receptor potential (TRP) channels which are expressed in primary afferent endings of free sensory neurons called nociceptors. TRP channels in nociceptors are involved in the detection of thermal, but also mechanical and chemical stimuli. Out of seven known types of temperature-sensitive TRP channels, three are responsible for detecting painful temperatures: vanilloid receptors TRPV1 (> 42 o C) and TRPV2 (> 52 o C) detect noxious heat, and ankyrin receptor TRPA1 detects noxious cold (< 17 o C). Better knowledge of TRP channel mechanisms of action is essential for understanding TRP channel functions and ultimately for the design of potential analgesics. New findings presented in this thesis clarify mechanisms of action of TRPV1 and TRPA1 receptors, focusing on camphor and voltage sensitivity of TRPV1 channels and calcium modulation of TRPA1 channels. The first topic discussed in this thesis is the mechanism of camphor sensitivity of TRPV1 receptor. Camphor is a naturally occurring substance known since time immemorial for its effective analgesic properties, yet its mechanism of action is not understood. Camphor is known to be a partial agonist of TRPV1 channel, a full agonist of TRPV3 channel, but also an inhibitor of...
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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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Structure and function of P2X receptors activated by extracellular ATP
Knězů, Michal ; Zemková, Hana (advisor) ; Hejnová, Lucie (referee)
ATP plays and important role in cellular signaling in many eukaryotic tissues. P2X receptors belong to a family of ligand-gated ion channels with ATP as naturally occurring ligand. They are responsible for many different physiological functions in organisms. There are several studies published in last 11 years about crystalization and structure of P2X receptors. These studies shed light on many phenomena regarding P2X receptors such as ligand binding, several types of modulation, characterization of P2X ion channel and mainly the overall structure of P2X receptors and unique structural elements of different P2X subtypes. These studies also help to explain reasons of P2X receptor desenzitization, mechanism of ion channel opening and conformational changes induced by ligand binding, a prerequisite of channel opening. The aim of this work is to summarize current knowledge about structures of P2X receptors. Key words: P2X receptor, purinergic signaling, ATP, ion channel, crystal structure
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Structural and pharmacological determinants of NMDA receptor channel gating
Ladislav, Marek ; Krůšek, Jan (advisor) ; Bendová, Zdeňka (referee) ; Zemková, Hana (referee)
N-methyl-D-aspartate receptors (NMDARs) are heterotetramers containing two obligatory glycine-binding (GluN1) and two glutamate/glycine-binding (GluN2/3) subunits. These receptors mediate excitatory synaptic transmission in the central nervous system and play a key role in high order neuronal processes as a learning and formation of memory. It has been shown that dysregulation of NMDARs is involved in the pathophysiology of neurological and psychiatric disorders. Each receptor is composed of four protomers exhibiting a conserved domain organization. The most distal part to the cell membrane is the amino-terminal domain that is linked to the ligand binding domain (LBD), which is connected to the pore-forming transmembrane domain (TMD) communicating with the intracellular carboxy-terminal domain. LBD and TMD are connected via three polypeptide chains - linkers. Channel opening is the key step in the NMDAR gating that allows the flux of ions across the membrane. The energy of agonist binding-evoked conformational changes is transferred via linkers to M3 helices forming an ion channel. The rearrangement of M3 helices in activated receptor makes the central cavity of the channel accessible. The details of energy transfer are not yet fully characterized, although accurate knowledge of the receptor gating...
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Incidence and role of the purinergic P2X7 receptor in the immune system
Piskačová, Kateřina ; Zemková, Hana (advisor) ; Červená, Kateřina (referee)
It has been shown recently that extracellular ATP and its metabolite adenosine are key mediators in the immune system. Depending on the concentration, ATP may act as an activator or an inhibitor to the immune response, whereas adenosine is generally well known as a specific immunosupressor. Signals delivered by extracellular ATP and adenosine are detected and transduced by purinergic P2- and P1- receptors, respectively. In principle, all cells of the immune system express P2X, P2Y and adenosine P1 receptors on their plasmatic membrane. Therefore, the purinergic signaling extends to all components of the immune and inflammatory responses, including neurodegenerative diseases. This knowledge triggered a wave of interest in research, development and synthesis of new compounds having effect on P1- and P2- receptors that could help in the treatment of chronic inflammatory diseases and neurodegenerative diseases. This bachelor thesis will summarize the most recent knowledge on the role of the P2X7 receptor in these processes. This subtype of P2-receptor is unique because it is involved in the release of cytokines from immune cells and plays a role in the cell growth and apoptosis.
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Role of reactive cysteines in the activation of the human TRPA1 ion channel
Synytsya, Viktor ; Vlachová, Viktorie (advisor) ; Zemková, Hana (referee)
TRPA1 is a thermosensitive ion channel from the family of TRP (transient receptor potential) receptors. In primary sensory neurons, TRPA1 is an important transducer of painful stimuli, where it contributes to detection of noxious, irritant and inflammatory compounds of endogenous and exogenous origin. The major activation mode of TRPA1 is covalent modification of N-terminal cysteines or lysines by electrophilic compounds. The potency of the electrophilic agonists is increased by voltage dependency of the TRPA1 channel, which contributes substantially during membrane depolarization. To date, the role of several cysteine residues in the N- terminus has been demonstrated. However, the functional role of six cysteines in the transmembrane domain is still unknown. The first part of the thesis focuses on the functional role of the transmembrane cysteines in the activation of human TRPA1 channel. Our results indicate that these sites do not mediate reactive-electrophile-induced activation but four of the six cysteines substantially contribute to voltage-dependent gating of the channel and two participate in calcium-dependent modulation of TRPA1. In the second part of this thesis we aim to explore the proximity of two specific charged residues, located in the linker between the fourth and the fifth...
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