Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

Submitted by Cristiane Chim (cristiane.chim@ucpel.edu.br) on 2016-11-11T11:14:08Z No. of bitstreams: 1 MARCO SALEH RIBEIRO.pdf: 1233321 bytes, checksum: aebd2e7f49d852825cab51345cf5eebc (MD5) / Made available in DSpace on 2016-11-11T11:14:08Z (GMT). No. of bitstreams: 1 MARCO SALEH RIBEIRO.pdf: 1233321 bytes, checksum: aebd2e7f49d852825cab51345cf5eebc (MD5) Previous issue date: 2015-08-31 / Bipolar disorder is a psychiatric illness associated with alternate states of depression and mania/hypomania episodes. Glycogen synthase kinase 3β (GSK-3β) and synaptosomal-associated protein 25 (SNAP-25) are associated respectively, with the modulation of gene expression and neural plasticity in the pathogenesis of mood disorders. Curcumin, active compound extracted from Curcuma longa, has been described as a neuroprotective agent in neurodegenerative disorders, although their mechanisms of action are not completely elucidated. In this study we investigate the impact of ketamine-induced model of mania on GSK-3β and SNAP-25 immunocontent, and assess in this model the neuroprotective effect of Curcumin pretreatment. Rats received peanut oil (vehicle), curcumin 20 or 50 mg/kg (p.o.), once a day for 14 days. From the 8th to the 14th day the animals also received saline or ketamine (25 mg/kg i.p.), once a day. On the 15th day of treatment, the animals received a single injection of ketamine or saline and the locomotor activity was assessed in the open-field apparatus after 30 min. Immunodetection of the proteins pGSK-3β and SNAP-25 were evaluated by Western Blotting in the prefrontal cortex (PFC) and the hippocampus (HP). The administration of Curcumin in doses of 20 and 50 mg/kg prevented the hyperlocomotion induced by ketamine in the open-field test. In addition, both doses of Curcumin prevented the decrease in density of pGSK-3β and SNAP-25 ketamine-induced in PFC and HP. In conclusion, our results show that Curcumin prevents hyperlocomotion and presents a neuroprotective effect by restoring SNAP-25 density probably via modulation of GSK-3β. / O transtorno bipolar é uma doença psiquiátrica associada a estados alternados de episódios de depressão e mania / hipomania. O glicogênio sintase quinase 3β (GSK-3β) e proteína associada a sinaptossomas de 25 (SNAP-25) estão associados, respectivamente, com a modulação da expressão gênica e a plasticidade neural na patogênese de perturbações do humor. A curcumina, composto ativo extraído de Curcuma longa, tem sido descrito como um agente neuroprotetor em desordens neurodegenerativas, embora o seu mecanismo de ação não está completamente elucidado. Neste estudo foi investigado o impacto do modelo induzida por cetamina de mania em GSK-3β e SNAP-25, e avaliado neste modelo, o efeito neuroprotetor da curcumina pré-tratamento. Os ratos receberam óleo de amendoim (veículo), curcumina 20 ou 50 mg / kg (p.o.), uma vez por dia durante 14 dias. A partir do dia 8 ao dia 14 os animais também receberam solução salina ou cetamina (25 mg / kg i.p.), uma vez por dia. No 15º dia de tratamento, os animais receberam uma única injeção de cetamina ou uma solução salina e a atividade locomotora foi avaliada no aparelho campo aberto após 30 min. Imunodetecção das proteínas pGSK-3p e SNAP-25 foram avaliadas por Western Blotting no córtex pré-frontal (PFC) eo hipocampo (HP). A administração da curcumina, em doses de 20 e 50 mg / kg preveniu o hiperlocomoção induzida por cetamina no teste de campo aberto. Além disso, ambas as doses de curcumina evitou a diminuição da densidade de pGSK-3β e SNAP-25 em PFC e HP induzida por cetamina. Em conclusão, os nossos resultados mostram que a curcumina impede hiperlocomoção e apresenta um efeito neuroprotector, restaurando SNAP-25, provavelmente, através da modulação da densidade de GSK-3β.

No description available.

Obwohl die Struktur und das Ausmaß dendritischer Verzweigungen eine wichtige Rolle bei der Informationsübertragung neuronaler Zellen spielen, ist bislang wenig über die Bausteine und Molekularmechanismen des Dendritenwachstums bekannt. Unter der Verwendung primär dissoziierter hippocampaler Zellkulturen embryonaler Mäuse untersuchte ich frühe Stadien des Zellfortsatzwachstums. Dabei konnte ich SNAP-25 (synaptosomal associated protein of 25 kDA), ein Schlüsselprotein der regulierten Exozytose, nicht nur in Axonen und terminalen Axonendigungen, sondern auch anhand von Doppelimmunmarkierungen mit den dendritischen Markern Transferrin-Rezeptor und MAP-2 in Dendriten lokalisieren. Die spezifische Inaktivierung von SNAP-25 durch Botulinumneurotoxin A (BoNT/A) führte zur Hemmung des Axonwachstums und des Vesikelrecyclings in terminalen Axonendigungen. Darüberhinaus wurde auch das Wachstum dendritischer Fortsätze von Körner- und Pyramidenzellen durch BoNT/A signifikant gehemmt. Daraus läßt sich schließen, daß SNAP-25, im Gegensatz zu Synaptobrevin, an konstitutiven Prozessen in den Axonen und Dendriten hippocampaler Neurone beteiligt ist. / Structure and dimension of the dendritic arbor are important determinants of information processing by the nerve cell, but mechanisms and molecules involved in dendritic growth are essentially unknown. I investigated early mechanisms of dendritic growth using mouse fetal hippocampal neurons in primary culture, which form processes during the first week in vitro. I detected a key component of regulated exocytosis, SNAP-25 (synaptosomal associated protein of 25 kDa)., in axons and axonal terminals as well as in dendrites identified by the occurrence of the dendritic markers transferrin receptor and MAP2. Selective inactivation of SNAP-25 by botulinum neurotoxin A (BoNTA) resulted in inhibition of axonal growth and of vesicle recycling in axonal terminals. In addition, dendritic growth of hippocampal pyramidal and granule neurons was significantly inhibited by BoNTA. These observations indicate that SNAP-25, but not synaptobrevin, is involved in constitutive axonal growth and dendrite formation by hippocampal neurons.

No description available.

Exocytosis, the fusion of a vesicle to a cellular membrane, involves a protein named SNAP-25. This protein, containing two alpha helices connected with a linker region, is localized to the cell membrane via palmitic acids attached to the cysteine residues of its linker region in a process called palmitoylation. Are cysteine residues of the SNAP-25 linker region palmitoylated in an ordered manner and to a particular extent? The answer to this question may give insight into the regulated nature of exocytosis. While it is generally accepted that SNAP-25 must be palmitoylated in order to perform its exocytotic functions, the details surrounding this process are still being discovered, defined, and understood. In these studies we replicate the oxidation, reduction, and palmitoylation of SNAP-25 in vitro. Palmitoylating SNAP-25 in vitro, a process which occurs regularly in vivo, allows us to determine the extent of palmitoylation. In vitro palmitoylation of SNAP-25 was studied both with and without a native palmitoyl acyl transferase (PAT), DHHC-17, the enzyme to attach palmitic acids to cysteines in the linker region of SNAP-25. These studies were done under a variety of conditions designed to identify (1) components necessary for optimal palmitoylation and (2) extent of palmitoylation with components that mimic native conditions. Palmitoylation is a common modification for a variety of proteins, both soluble and membrane-bound. Like phosphorylation, palmitoylation is reversible and may play an important role in regulation of cellular processes. Specifically, the palmitoylation of SNAP-25 may play a critical role in the regulation of exocytosis and therefore learning further details about this important process may help us to better understand a variety of neurodegenerative diseases and states of decreased or compromised exocytosis.

Neurons depend upon neurotransmitter release through regulated exocytosis to accomplish the immense processing performed within the central nervous system. The SNARE hypothesis points to a family of proteins that are thought to enable the membrane fusion that leads to exocytosis. The secondary structure of SNAP-25 is unique among SNARE proteins in that it has two alpha helical SNARE motifs and a cysteine rich (C85, C88, C90, C92) membrane interacting region but notransmembrane domain. The cysteines may be modified by palmitoylation or oxidation but the role of these modifications in vivo is not well understood. Our goal is to elucidate possible regulatory roles of SNAP-25 that relate to its unique structure and these reversible modifications. However, the study of SNAP-25 in reconstituted systems is hampered by a lack of readily available palmitoylated SNAP-25. A method for in vitro palmitoylation of SNAP-25 by HIP14, a neuronal acyltransferase, is described along with the application of a biotinylation streptavidin assay to verify palmitoylation. Palmitoylation increases the extent to which SNAP-25 interacts with lipids as observed with an environment sensitive trpytophan fluorescence assay. Palmitoylation also alters the phase transition of DPPC lipids differently than unpalmitoylated SNAP-25.This effect on the membrane may influence fusion events. Oxidation of the cysteine residues may be responsible for the sensitivity of SNAP-25 to reactive oxygen species. Our data suggests that, when oxidized, SNAP-25 does not interact with membranes to the same extent as palmitoylated SNAP-25. This may provide a mechanism for reducing exocytosis during oxidative stress. Also, oxidized SNAP-25 is not susceptible to Botulinum Neurotoxin E. The effects of oxidation and palmitoylation on the protein interactions of SNAP-25 may shed light on its role in the SNARE complex and membrane fusion.

No description available.