African horse sickness virus (AHSV) affects equine populations around the world. It is the cause of a high rate of morbidity and associated large economic losses in affected regions. The virus is a segmented double stranded RNA virus and a member of Orbivirus genus in the Reoviridae family. The prototype member of the orbiviruses is bluetongue virus (STY) and other members include Chuzan virus and St. Croix River virus. These viruses are all characterized by a genome of ten dsRNA segments that encode at least ten different proteins. Three of the minor core proteins are found within the core of BTV. These are all associated with the RNA transcription complex and the enzymatic activities with which they are associated include an RNA polymerase (VP1), an RNA capping enzyme (VP4) and an RNA helicase (VP6). Genes homologous to the BTV genes that encode these proteins are found in all members of the Orbivirus genus. The aim of this thesis is to characterize VP4 of AHSV, the capping enzyme candidate, and to compare it to other orbivirus capping enzymes. Possible functional motifs and regions of importance within the orbivirus capping enzymes will be identified. The gene will also be expressed and used to perform assays to characterize the different enzymatic activities of VP4. The VP4 cDNA of AHSV serotype 3 was cloned and sequenced. From the full-length verified nucleotide sequence an open reading frame was identified and used to predict the amino acid sequence. These were compared to other orbivirus species including STY, Chuzan virus and St. Croix River virus. These alignments identified a number of highly conserved regions, consisting of four or more amino acids conserved between all the sequences analyzed. A fibronectin type 3-like motif, containing 12 conserved amino acids, was identified which could be responsible for protein binding. This motif contains 12 conserved amino acids making it a good candidate for a functional motif. Conservation does not, however, always predict regions of importance. In BTV a lysine-containing motif was identified to be responsible for GMP binding. This region is not conserved between the different viruses. AHSV has a motif containing a lysine residue similar to the motif identified in rotavirus and reovirus. Two other motifs described in BTV were also not conserved in the other viruses. One of them, a leucine zipper, was shown to dimerize BTV VP4. Phylogenetically, AHSV and Chuzan virus are the most closely related while BTV is more distant and St. Croix River virus forms a distinct out-group when the different VP4 sequences are compared. AHSV-3 VP4 was expressed as a histidine-tagged protein in the baculovirus expression system. Not unexpectedly, the protein was found to be insoluble, similar to BTV VP4 produced by means of the same system. However, whereas BTV VP4 could be solubilized by the addition of salt the AHSV VP4 remained insoluble at high salt concentrations. Several adjustments were made. Cells were lysed in a high salt buffer, the pH of the buffers was adjusted and sucrose cushions were used but none of the methods was found to improve the yield of soluble VP4 significantly. However, the pellet containing VP4 was relatively empty of contaminating protein and, therefore, a number of enzymatic assays were performed with the pellet. Assays for inorganic phosphatase and nucleotide phosphatase were performed. Strikingly, both assays indicated the presence of active phosphatases in the WT and VP4 pellets. Also, an assay was performed for guanylyltransferase activity but no activity was observed for this assay. The sequence data therefore points to VP4 as the probable capping enzyme although it may have a different structural complex. The failure to produce a reliable source of soluble purified AHSV VP4 made it impossible to provide evidence to confirm the associated enzymatic activities. / Dissertation (MSc(Genetics))--University of Pretoria, 2005. / Genetics / unrestricted

No description available.

Cronobacter species cause serious infections such as meningitis and enteritis in newborns and neonates, with the major vehicle being contaminated powdered infant formula. The main objectives of this study were i) to identify potential virulence factors, such as enterotoxin production; ii) characterize the gene(s) involved in adhesion and invasion of the human brain microvascular endothelial cells (HBMEC); and iii) determine whether strains from clinical, food, and environmental sources differ in their ability to produce surface-attached bacterial aggregates, known as biofilms. Random transposon mutagenesis was used on strains demonstrating the best adherence and invasion to blood- brain barrier cell lines (BBB). Isogenic mutants were then screened for increased or decreased adherence and invasion. Screening of the transposon library identified one isogenic mutant of a clinical strain which lost the ability to adhere to BBB cells. The transposon rescue revealed the insertion site to be within a diguanylate cyclase (DGC) gene. The major function of DGC in many Gram-negative bacteria is to synthesize cyclic diguanylate (c-di-GMP), a secondary bacterial metabolite known for regulating biofilm formation, motility, and virulence or aspects of microbial pathogenicity. Based on the findings of this study, DGC appears to play an important role in Cronobacter species’ ability to produce biofilms and may also have a role of the pathogenicity in the microorganism.

Orientador: Edson Antunes / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas / Made available in DSpace on 2018-08-26T14:39:41Z (GMT). No. of bitstreams: 1 BaldisseraJunior_Lineu_D.pdf: 1965195 bytes, checksum: 107b841684637a6a66bcdb7b9e929cef (MD5) Previous issue date: 2015 / Resumo: O recrutamento de eosinófilos para o pulmão inflamado é uma característica central da asma alérgica. Há relatos de que a ativação da guanilil ciclase solúvel (GCs) exerce atividade anti-inflamatória por inibir o recrutamento de leucócitos, e que o aumento de GMPc intracelular inibe a migração in vitro de eosinófilos humanos. A GCs é estimulada pelo NO, seu agonista fisiológico. Outros compostos são capazes de estimular a GCs de forma independente do NO, como as moléculas da família dos estimuladores NO-independentes e heme-dependentes, e, mais recentemente, por compostos estimuladores NO- e heme-independentes, chamados de ativadores da GCs. Neste contexto, o objetivo deste trabalho foi avaliar os efeitos do BAY 60-2770 (ativador NO- e heme-independente da GCs) em modelo murino de asma alérgica e na quimiotaxia in vitro de eosinófilos humanos induzida pela eotaxina. Para tanto, camundongos machos C57Bl6 (25 g, 6 semanas de idade) foram sensibilizados (2 injeções s.c. de 100 ?g de ovalbumina, nos dias 0 e 7) e submetidos ao desafio intranasal com OVA (10 ?g; duas vezes por dia, com intervalos de 6 horas entre cada desafio) nos dia 14 e 15, na presença e/ou ausência (veículo) do tratamento crônico com BAY 60-2770 (1mg/Kg/gavage; 14 dias). Os animais foram anestesiados e sacrificados 48 horas após o primeiro desafio, e as amostras biológicas colhidas para análise. O perfil inflamatório alérgico foi avaliado através da contagem total e diferencial de leucócitos no lavado broncoalveolar (LBA), sangue periférico, perfusato de medula óssea (MO) e em corte histológico. Foram dosados os níveis de IgE sérica específica a OVA, citocinas Th1 (IFN-?), Th2 (IL-4, IL-5, IL-10), TNF-? e eotaxina no LBA. A expressão proteica da GCs (subunidades ?2 e ?1) e da iNOS foi quantificada no parênquima pulmonar. O desenho experimental foi dividido em quatro grupos, a saber: grupo tratado com Veículo e instilado com Salina (VS); grupo tratado com Veículo e desafiado com OVA (VO); grupo tratado com BAY 60-2770 e instilado com Salina (BS); grupo tratado com o BAY 60-2770 e desafiado com OVA (BO). Nossos resultados mostraram níveis elevados (p<0,05) de IgE em soro de animais sensibilizados comparados com animais naive, confirmando a eficácia da sensibilização, que não foi alterada pelo tratamento com BAY 60-2770. O desafio alérgico à OVA (grupo VO), como esperado, gerou uma resposta inflamatória alérgica pulmonar, caracterizada pela presença marcante de eosinófilos no pulmão e de níveis elevados de IL-4 no LBA, assim como eosinofilia sanguínea e eosinofilopoese na medula óssea. Esta resposta foi significativamente acompanhada da redução da expressão da GCs (subunidades ?1 e ?1) e aumento da expressão protéica da iNOS no parênquima pulmonar, comparada a animais não desafiados (grupo VS). Não foram observadas diferenças nos níveis de TNF-? e eotaxina no LBA entre os grupos. As citocinas IFN-? e IL-10 não foram detectadas no LBA em nenhum grupo experimental. O tratamento crônico com BAY 60-2770 (grupo BO) reduziu significativamente os níveis de IL-4 e IL-5 no LBA, inibiu a eosinofilia pulmonar (LBA), sanguínea e peri-bronquiolar, e suprimiu a eosinofilopoiese na medula óssea, os quais foram acompanhados da restauração da expressão da GCs (?1 e ?1) e da iNOS no parênquima pulmonar, comparado com o grupo desafiado tratado com veículo (grupo VO). Em experimentos separados, eosinófilos humanos de indivíduos saudáveis foram submetidos aos ensaios de quimiotaxia induzida por eotaxina (300 ng/mL) na presença do BAY 60-2770 individualmente e/ou co-incubado com inibidor da GCs, ODQ (10 ?M). Nas mesmas condições, foram determinados os níveis de GMPc intracelular, e realizado o teste de viabilidade celular por redução do MTT. A resposta quimiotática induzida por eotaxina foi significativamente inibida pelo BAY 60-2770 (10 ?M), de modo dependente de GMPc. O efeito inibitório do BAY 60-2770 foi potencializado pela prévia co-incubação com ODQ, que elevou marcantemente os níveis de GMPc intracelulares e inibiu significativamente a migração de eosinófilos frente à eotaxina nas concentrações de 1, 3 e 5 ?M de BAY 60-2770. A viabilidade celular não foi afetada pelo BAY 60-2770. Em conjunto, nossos resultados mostram que o BAY 60-2770 é capaz de reduzir a inflamação alérgica pulmonar murina, e de inibir de forma dependente de GMPc a migração de eosinófilos humanos induzida por eotaxina. Concluímos que o BAY 60-2770 apresenta potencial valor terapêutico na asma alérgica / Abstract: Eosinophil recruitment to inflamed lung is a hallmark of allergic asthma. The literature has shown that soluble guanylyl cyclase (sGC) plays a key antiinflammatory role by inhibiting leukocyte recruitment, and that increased cGMP intracellular levels inhibit human eosinophil chemotaxis in vitro. The soluble guanylyl cyclase is stimulated by NO, its physiological agonist. Other compounds are able to NO-independently stimulate sGC, such as the family of NO-independent and heme-dependent stimulators, and the NO- and heme-independent stimulators, known as sGC activators. Therefore, this study aimed to investigate the effects of BAY 60-2770 (NO- and haem-independent sGC activator) in pulmonary allergic inflammation in mice and human eosinophil chemotaxis in vitro induced by eotaxin. Part I: Male C57BL6 mice were sensitized (100 ?g of ovalbumin, s.c.; day 0 and 7) and intranasally challenged with OVA (10 ?g; twice a day, 6 h between challenges) at days 14 and 15, with BAY 60-2770 (1 mg/Kg/gavage; 14 days) and/or its vehicle. Mice were anaesthetized and exsanguinated at 48 hours post first-OVA challenge, and biological samples were collected. The inflammatory profile was evaluated by total and differential cell counts in bronchoalveolar lavage (BAL) fluids, peripheral blood, bone marrow perfusate and histological slides. Serum OVA-specific IgE levels were measured and Th1 (IFN-?), Th2 (IL-4, IL-5, IL-10) cytokines, TNF-? and eotaxin levels were quantified in BAL fluids. Soluble guanylyl cyclase subunits (?1 and ?1) and iNOS protein expression were determined in lung parenchyma. The experimental design was divided in four groups, namely: Vehicle treated-instilled with Saline (VS group); Vehicle treated-challenged with OVA (VO group); BAY 60-2770 treated-instilled with Saline (BS group) and BAY 60-2770 treated-challenged with OVA (BO group). Our results showed seric elevated IgE levels (p<0.05) in OVA-sensitized mice compared with naive animals, confirming the efficiency of sensitization procedure, which was not affected under BAY 60-2770 treatment. As expected, the OVA-challenge in VO group triggered a pulmonary allergic inflammatory response, characterized by markedly eosinophil migration to lung, elevated IL-4 levels in BAL fluid, as well as blood eosinophilia and marrow eosinophilopoiesis in bone marrow. This response was significantly accompanied by reduced GCs (subunits ?1 and ?1) and increased iNOS expression in lung parenchyma, compared with non-challenged animals (VS group). No differences on TNF-? and eotaxin levels in BAL fluids were observed among studied groups. Levels of IFN-? and IL-10 were not detected in BAL fluids of any groups. Chronic oral treatment with BAY 60-2770 (BO group) significantly reduced IL-4 and IL-5 levels in BAL fluids, inhibited pulmonary (BAL), blood and peri-bronchiolar eosinophilia, and supressed bone marrow eosinophilopoiesis, which was accompanied by restoration of sGC and iNOS expression in lung parenchyma, compared with vehicle treated group (VO). In separate experiments, isolated human eosinophils from healthy volunteers were individually incubated with BAY 60-2770 and/or previously co-incubated with the sGC inhibitor, ODQ (10 ?M), and allowed to migrate toward eotaxin (300 ng/ml; 1 h, 37°C) in chemotaxis chamber. In the same conditions, intracellular cGMP levels were determinated and cell viability test were performed by MTT reduction. Our data showed that human eosinophil migration to eotaxin was significantly inhibited by BAY 60-2770 (10 ?M) in a cGMP-dependent manner. Inhibitory effect of BAY 60-2770 was potentiated by previous co-incubation with ODQ, which markedly elevated cGMP intracellular levels and inhibited eosinophils migration induced by eotaxin at 1, 3 and 5 ?M BAY 60-2770 concentrations. The cell viability was not affected by BAY 60-2770. Together, our results show that BAY 60-2770 is able to reduce murine pulmonary allergic inflammation, and to inhibit human eosinophil migration toward eotaxin in cGMP-dependent manner. In conclusion, the compound BAY 60-2770 presents potential therapeutic value in allergic asthma / Doutorado / Farmacologia / Doutor em Farmacologia

Orientadores: Fabíola Taufic Mónica Iglesias, Edson Antunes / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas / Made available in DSpace on 2018-08-29T00:02:26Z (GMT). No. of bitstreams: 1 Fernandes_CamilaStefaniEstancial_M.pdf: 2289746 bytes, checksum: e67d3948b14883b515cd7e008bc69850 (MD5) Previous issue date: 2015 / Resumo: Duas classes de medicamentos denominadas estimuladores e ativadores da GCs foram desenvolvidas para uso terapêutico em situações patológicas, onde há menor biodisponibilidade NO ou tolerância farmacológica. A principal diferença entre os moduladores da GCs é que os ativadores atuam de maneira mais eficaz mesmo quando a enzima encontra-se no estado oxidado. O presente trabalho foi dividido em duas etapas, a saber: 1) caracterização farmacológica do ativador BAY 60-2770 em corpo cavernoso (CC) de coelho e 2) avaliação do efeito do ativador BAY 60-2770 e estimulador BAY 41-2272 da GCs em CC isolado de ratos espontaneamente hipertensos (SHR) e normotensos (WKY). O BAY 60-2770 promoveu relaxamento concentração dependente em corpo cavernoso de coelho (pEC50: 7,584 ± 0,1923), sendo este efeito potencializado na presença dos inibidores da GCs ODQ (10 µM; pEC50: 8,170 ± 0,1365) e da fosfodiesterase tipo 5 (PDE5), tadalafil (100 ?M; pEC50: 8,381 ± 0,1334). A contração induzida por estimulação elétrica foi reduzida em aproximadamente 50% na presença de BAY 60-2770, sendo este efeito potencializado na presença de ODQ. Em relação ao relaxamento induzido pela estimulação elétrica, o ODQ e BAY 60-2770 aboliu e aumentou, respectivamente o relaxamento. A co-incubação de BAY 60-2770 com ODQ não alterou o relaxamento em comparação com o ODQ sozinho. Curiosamente, quando BAY 60-2770 foi incubado 20 min antes da adição de ODQ, os relaxamentos induzidos por estimulação elétrica foram parcialmente restaurados quando comparado com o ODQ sozinho. Em relação à segunda etapa do trabalho, o relaxamento induzido pelos moduladores da GCs, BAY 60-2770 e BAY 41-2272 não diferiram em CC de ratos SHR comparados ao seu respectivo controle, porém, estes dados não corroboram com a quantificação de GMPc, no qual evidenciamos aumento dos seus níveis em CC de ratos SHR sendo estes níveis ainda maiores quando na presença de ODQ em comparação ao CC de WKY. Observamos também que o relaxamento induzido pela acetilcolina (ACh) encontrou-se reduzido em CC dos animais hipertensos, entretanto, a adição de BAY 60-2770 ou BAY 41-2272 restaurou este relaxamento. Não foi encontrada diferença na expressão das subunidades ?1 e ?1 da GCs em ratos SHR e WKY, porém quando analisamos a expressão da PDE-5, verificamos maior expressão em CC de ratos SHR. O BAY 60-2770 foi capaz de elevar a pressão intracavernosa em CC de ratos normotensos em todas as frequências estudadas, porém esta elevação somente foi significativa na frequência de 16 Hz. Considerando que 1) BAY 60-2770 induziu relaxamento em CC de coelho e de rato hipertenso de maneira mais potente que o estimulador BAY 41-2272, 2) a adição de ODQ potencializou o relaxamento do BAY 60-2770, mas não do BAY 41-2272 em CC de ambas espécies, 3) o aumento dos níveis de GMPc foi maior em CC de ratos SHR após estímulo com BAY 60-2770, mas não com BAY 41-2272 pode-se concluir que em situações patológicas onde há oxidação da GCs e/ou menor biodisponilidade de NO, os ativadores da GCs seriam mais vantajosos que os estimuladores ou inibidores da PDE5 para o tratamento da disfunção erétil / Abstract: Two classes of drugs referred to as stimulators and sGC activators have been developed for therapeutic use in pathological situations where there is less NO bioavailability and pharmacological tolerance. The main difference between the sGC activators modulators is that they act more effectively even when the enzyme is in the oxidized state. This study was divided into two stages: 1) pharmacological characterization of BAY 60-2770 activator in corpus cavernosum (CC) of rabbit and 2) evaluation of the effect of BAY 60-2770 BAY 41-2272 activator and stimulator of GCs isolated from spontaneously hypertensive rats (SHR) and normotensive (WKY). The BAY 60-2770 induced concentration-dependent relaxation in rabbit corpus cavernosum (pEC 50: 7.584 ± 0.1923), and this increased effect in the presence of GCs ODQ inhibitors (10 ?M; pEC 50: 8.170 ± 0.1365) and the phosphodiesterase type 5 (PDE5), tadalafil (100 ?m; pEC50: 8.381 ± 0.1334). The contraction induced by electric stimulation was reduced by approximately 50% in the presence of BAY 60-2770, and this increased effect in the presence of ODQ. In relation to the relaxation induced by electrical stimulation, ODQ and BAY 60-2770 abolished and increased, respectively the relaxation. Co-incubation with BAY 60-2770 with ODQ did not change compared to the relaxation with only ODQ. Curiously, when BAY 60-2770 was incubated 20 minutes before addition of ODQ, the relaxation induced by electric stimulation was partially restored when compared with only ODQ. In the second part, relaxation induced by modulators of GCs, BAY 60-2770 and BAY 41-2272 did not differ in SHR CC compared to their respective control, however, these data do not corroborate the quantification of cGMP, in which we observed an increase in their levels in SHR rats and these levels even higher in the presence of ODQ in comparing the CC of WKY. We also observed a reduction of the relaxation induced by acetylcholine (ACh) in CC of hypertensive animals, however, the addition of BAY 60-2770 or BAY 41-2272 restored this relaxation. There was no difference in the expression of ?1 and ?1 subunits of sGC in SHR and WKY rats, but when we analyzed the expression of PDE-5, we found greater expression in SHR. The BAY 60-2770 was able to raise up the intracavernous pressure in the normotensive rats in all studied frequencies, but this increase was only significant in the frequency of 16 Hz. Considering 1) BAY 60-2770 induced relaxation in rabbit and hypertensive rat so that the most potent stimulator BAY 41-2272, 2) addition of ODQ potentiated relaxation of BAY 60-2770, but not in BAY 41-2272 in CC of both, 3) increased levels cGMP was greater in SHR rats after stimulation with BAY 60-2770, but not in BAY 41-2272 so can be concluded that in pathologic situations where there is oxidation of GCs and / or low bioavailability of NO, would activators of sGC more advantageous than PDE5 inhibitors or stimulators for the treatment of erectile dysfunction / Mestrado / Farmacologia / Mestra em Farmacologia

O segundo mensageiro cGMP está envolvido em diversas funções celulares incluindo a visão em mamíferos. Embora trabalhos anteriores mostrassem variações nos níveis de cGMP durante o ciclo de vida de Blastocladiela emersonii e evidências da existência de enzimas específicas envolvidas na sua síntese (guanilato ciclase) e degradação (cGMP fosfodiesterase), nenhum genoma de fungo publicado até o momento mostrou a existência de genes codificando estas enzimas. Este fato é atribuído por evolucionistas à completa perda de motilidade dos fungos em geral, já que cGMP está primordialmente associado a células com cílios. Blastocladiomicetos, como Blastocladiella, apresentam células móveis em pelo menos um estágio do seu ciclo de vida, o que poderia explicar a existência dessa via nesses fungos. Uma investigação no banco de ESTs de B. emersonii revelou a existência de cDNAs codificando parte de prováveis guanilato ciclases (BeGC1, BeGC2 e BeGC3) e uma possível cGMP fosfodiesterase (BePDE). Assim, este trabalho buscou confirmar a existência destas enzimas e caracterizar a sinalização por cGMP em B. emersonii. A proteína recombinante selvagem correspondente ao domínio catalítico de BePDE mostrou atividade de degradação sobre cGMP e a mutação E389A foi capaz de alterar a especificidade por cGMP. Com o sequênciamento do genoma de B. emersonii obteve-se as sequências completas das guanilato ciclases. Em BeGC2 não foi possível identificar o ligante responsável por sua ativação. Em BeGC3, a presença de um domínio Heme-Pas sugeriu sua ativação por óxido nítrico. A presença de um domínio rodopsina em BeGC1 sugeriu sua ativação por luz. Experimentos de microscopia por imunofluorescência localizaram BeGC1 no \"eyespot\", BeGC2 no capacete nuclear e BeGC3 no citoplasma de zoósporos de B. emersonii. Verificamos também que zoósporos realizam fototaxia em direção à luz verde e que a adição de hidroxilamina, inibidor de rodopsina, ou do inibidor de guanilato ciclase LY83583 tem efeito negativo na fototaxia, bem como impede o aumento dos níveis de cGMP observado em zoósporos expostos à luz verde. O bloqueio da síntese de retinal por Norflurazon também inibiu a fototaxia sendo esta restaurada quando adicionamos retinalA1. Estes dados, juntamente com o fato de o domínio rodopsina de BeGC1 ser a única rodopsina presente no genoma, indicam que BeGC1 é responsável pela fototaxia nos zoósporos de B. emersonii. O genoma do fungo apresenta ainda um possível canal de potássio ativado por cGMP (BeCNG1) localizado na membrana plasmática de zoósporos, similar ao canal regulado por cGMP envolvido na visão em humanos. Ensaios de microfluorimetria também evidenciaram a presença de um canal ativado por cGMP relacionado com o influxo de potássio e a motilidade dos zoósporos. Um modelo para a via de sinalização da fototaxia em B.emersonii foi proposto e comparado com a sinalização presente na visão de mamíferos, destacando a existência de cGMP e rodopsina em ambos os processos e sugerindo uma possível origem comum. Portanto, os resultados obtidos suportam a existência da sinalização por cGMP em B. emersonii, além de indicar o papel dessa sinalização na fototaxia dos zoósporos, sendo esta a primeira via de sinalização por cGMP caracterizada em fungos. / The second messenger cyclic GMP is involved in a wide array of cellular processes including vision in mammals. Although previous studies demonstrated changes in cGMP levels during the life cycle of Blastocladiela emersonii and evidences of specific enzymes involved in its synthesis (guanylyl cyclase) and hydrolysis (cGMP-phosphodiesterase), no fungal genome published so far shows the presence of genes encoding these enzymes. Evolutionists attribute the absence of cGMP signaling pathways in higher fungi to the sedentary life style of these organisms, since cGMP is primarily associated with ciliated cells. However, blastocladiomycetes like Blastocladiella, have motile cells in at least one stage of their life cycle, which could explain the existence of this pathway in these primitive fungi. Inspection of B. emersonii EST data bank, revealed cDNAs encoding part of three putative guanylyl cyclases (BeGC1, BeGC2 e BeGC3) and one possible cGMP phosphodiesterase (BePDE). Thus, the purpose of this study was to confirm the existence of these enzymes and characterize the cGMP signaling pathway in this model. The recombinant protein containing the wild type catalytic domain of BePDE presented activity towards hydrolysis of cGMP and the E389A mutation of this domain changed the cGMP specificity of this enzyme. The complete nucleotide sequence of the guanylyl cyclases were obtained by sequencing of B. emersonii genome. In BeGC2 we were unable identify the ligand responsible for its activation, but in BeGC3, the presence of a Heme-Pas domain suggested its activation by nitric oxide. The presence of a rhodopsin domain in BeGC1 suggested its activation by light. Immunofluorescence microscopy localized BeGC1 in the \"eyespot\" structure, BeGC2 in the nuclear cap and BeGC3 in the cytoplasm of zoospores of B. emersonii. We found that Blastocladiella zoospores performed phototaxis toward green light and photobleaching of rhodopsin function using hydroxylamine prevented both phototaxis and the increased cGMP levels observed when zoospores were exposed to green light. The same effect was observed using the guanylyl cyclase inhibitor LY83583. Inhibition of retinal synthesis using Norflurazon prevented the phototaxis response, which could be restored by zoospore complementation with retinalA1. The BeGC1 gene is the only rhodopsin found in the draft assembly of B. emersonii genome, which indicates that BeGC1 is responsible for phototaxis observed in zoospores. We also found in the genome a possible cGMP-activated potassium channel (BeCNG1), localized in the plasma membrane of the zoospores, which is similar to the cGMP-activated channel involved in human vision. In addition, microfluorimetry assays revealed the presence of a cGMP-activated potassium channel involved in potassium influx and zoospore motility. The signaling model of B. emersonii phototaxis was proposed and compared with the mammalian vision system, with cGMP and rhodopsin acting in both signaling pathways, suggesting a common origin. Altogether our data indicate that Blastocladiella emersonii has a cGMP signaling system involved in phototaxis, being the first cGMP signaling pathway characterized in fungi.

Bordetella pertussis produces many virulent factors including adenylate cyclase toxin (CyaA) This toxin preferentially invades cells of immune system with integrin receptor CD11b/CD18 and weakens the immune system of the host. CyaA affects invaded cells in two ways. First, CyaA creates a cation-selective pores in the membrane of invaded cell and causes colloidal osmotic lysis. Second, CyaA converts cytosolic ATP into signal molecule cAMP, which causes a loss of physiological function of invaded cell and also leads to cellular death. The aim of my thesis was to test a suitability of a new model system composed from synthetic lipids - diphytanoyls, for a characterization of pore-forming properties of adenylate cyclase toxin. In the past, asolectin model system comprising many different lipid was used for characterization but it was found to be too complex for defining the role of individual lipids in CyaA activity. Further the effect of cholesterol for activity of CyaA was studied in a new model system because it was found recently that translocation of adenylate cyclase domain takes place at lipids rafts with high concentration of cholesterol. The last aim of my thesis was to characterize a newly discovered type of channel with the two conductance levels. Key words: Bordetella pertussis, adenylate...

Nitric oxide (NO) is an important signaling molecule in plants. In the pollen of Arabidopsis thaliana, NO causes re-orientation of the growing tube and this response is mediated by 3′,5′-cyclic guanosine monophosphate (cGMP). However, in plants, NO-sensors have remained somewhat elusive. Here, the findings of an NO-binding candidate, Arabidopsis thaliana DIACYLGLYCEROL KINASE 4 (ATDGK4; AT5G57690) is presented. In addition to the annotated diacylglycerol kinase domain, this molecule also harbors a predicted heme-NO/oxygen (H-NOX) binding site and a guanylyl cyclase (GC) catalytic domain which have been identified based on the alignment of functionally conserved amino acid residues across species. A 3D model of the molecule was constructed, and from which the locations of the kinase catalytic center, the ATP-binding site, the GC and H-NOX domains were estimated. Docking of ATP to the kinase catalytic center was also modeled. The recombinant ATDGK4 demonstrated kinase activity in vitro, catalyzing the ATP-dependent conversion of sn-1,2-diacylglycerol (DAG) to phosphatidic acid (PA). This activity was inhibited by the mammalian DAG kinase inhibitor R59949 and importantly also by the NO donors diethylamine NONOate (DEA NONOate) and sodium nitroprusside (SNP). Recombinant ATDGK4 also has GC activity in vitro, catalyzing the conversion of guanosine-5'-triphosphate (GTP) to cGMP. The catalytic domains of ATDGK4 kinase and GC may be independently regulated since the kinase but not the GC, was inhibited by NO while Ca2+ only stimulates the GC. It is likely that the DAG kinase product, PA, causes the release of Ca2+ from the intracellular stores and Ca2+ in turn activates the GC domain of ATDGK4 through a feedback mechanism. Analysis of publicly available microarray data has revealed that ATDGK4 is highly expressed in the pollen. Here, the pollen tubes of mis-expressing atdgk4 recorded slower growth rates than the wild-type (Col-0) and importantly, they showed altered NO responses. Specifically, the mis-expressing atdgk4 pollen tubes have growth rates that were less affected by NO and showed reduced bending angles when challenged by an NO source. Further works on atdgk4 knockout/knockdown mutants will reveal the biological functions of ATDGK4 in NO and/or cGMP signaling in the pollen, and in the broader fertilization process.

EN This Ph.D. thesis focuses on the heme containing gas sensor proteins. These proteins are predominantly present in bacteria, in which play an important role in processes like, sporulation, antibiotic resistance and so on. Heme containing sensor proteins composed of two domains. First one is a globin domain, which contains the heme molecule. Interaction of heme with gas molecule acts as a signal for the activation/inactivation of the second functional domain. Part of this thesis is formed by a review, which summarized the current knowledge about heme containing sensor proteins. In the next part of this thesis we focused on three representatives from the group of oxygen sensor proteins - histidine kinase AfGcHK, diguanylate cyclase YddV and phosphodiesterase EcDOS. The main aim of this thesis was to solve the mechanism of interdomain/intraprotein signal transduction in two oxygen sensor proteins with globin fold of their sensor domain (AfGcHK, YddV). For this purpose, we used the kinetic analysis of their functional domain activity and the methods of structural biology. We also studied the mechanism of interprotein signal transduction in AfGcHK and its cognate partner RR protein. It was also tested, how the presence of sodium disulfide affects the functional properties of oxygen sensor proteins...

Secretin and VIP stimulate cardiac adenylyl cyclase activity and exert a positive inotropic action in several mammalian species. This study examined positive inotropic activity and cAMP levels in rat papillary muscle. Isoproterenol and secretin increased contractions by 150 ± 31% and 129 ± 27%, respectively. VIP increased contraction by 30 ± 21% only at 10 μM. Isoproterenol significantly increased cAMP levels by 82%, whereas increases by secretin (58%) and VIP (56%) were not significant. These results are consistent with reports that secretin and VIP stimulate cardiac adenylyl cyclase in the rat, but suggest that cAMP tissue levels cannot totally explain the positive inotropic responses to secretin and VIP.