Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 132-145).

L'adénosine monophosphate cyclique (AMPc) est une molécule très largement conservée dans le monde du vivant. Chez les bactéries, cette molécule signal est impliquée, entre autres, dans l'adaptation aux changements de milieu, au développement de la virulence, à la sporulation et la compétence. Bien qu'il fut démontré dans les années 1970 que cette molécule nécessitait un transporteur afin de traverser la membrane cellulaire, l'identité de celui-ci restait jusqu'à très récemment inconnue. Ce n'est qu'en 2011 que Hantke et ses collègues démontrèrent l'implication de la protéine TolC dans l'export de l'AMPc. Au cours de ma thèse, j'ai démontré le rôle prépondérant du complexe Opp dans l'import d'AMPc chez Escherichia coli. Ce complexe, formé des protéines OppABCD et F, est connu pour transporter des oligopeptides et se trouve dans la membrane interne de nombreuses bactéries. Pour arriver à la conclusion de son implication dans le transport d'AMPc, une banque de mutants a été créée dans une souche ne produisant pas d'AMPc (cyaA-). Afin d'identifier le transporteur responsable de l'import de l'AMPc, différents cribles qui testent la présence de cette molécule dans la cellule, ont ensuite été réalisée sur ces clones. Après analyse des résultats obtenus, l'opéron opp a été pressenti comme étant nécessaire à l'entrée de l'AMPc dans la cellule. Le double mutant cyaA-oppA- a été créé et de nouvelles expériences sont venues confirmer notre hypothèse. La protéine OppA a ensuite était surexprimée et purifiée pour nous permettre de faire des tests biochimiques d'interaction entre AMPc et OppA, basés sur la fluorescence émise par la protéine elle-même ou un homologue de l'AMPc, l'ε-AMPc. Ces expériences nous ont permis de confirmer l'interaction entre la protéine OppA et l'AMPc. Le système Opp est donc le principal importateur d'AMPc chez Escherichia coli, mais il ne semble pas être l'unique transporteur impliqué. Un autre candidat très intéressant est le complexe Dpp, connu pour transporter les dipeptides. En effet, les expériences préliminaires effectuées démontrent une diminution de la concentration intracellulaire d'AMPc dans une cellule cyaA-dppA- comparée à celle observée dans une souche cyaA-. Les travaux réalisés pendant ces trois dernières années permettent de conclure que le complexe Opp est le principal importateur d'AMPc, très probablement secondé par le complexe Dpp. / Cyclic adenosine monophosphate (cAMP) is a signalling molecule conserved in all reigns of life. In bacteria, cAMP plays an important role in processes as diverse as the adaptation to a changing environment, the control of virulence, sporulation and competence. Although it has been proven in the 1970s that this molecule needs an active transporter to traverse the plasma membrane, the first one of these transporters was discovered only a few years ago. In 2011, Hantke et al have shown that the TolC protein is involved in the efflux of cAMP. During my PhD work I have identified the Opp complex as a major player of cAMP import into Escherichia coli. This complex, composed of proteins called OppABCD and F, is known to transport oligopeptides across the inner membrane of numerous bacterial species. To prove the involvement of the Opp complex in cAMP transport, I have used transposon mutagenesis to generate a collection of random mutants in a strain that does not produce cAMP (cyaA-). Different screens were used to detect mutants with impaired transport of extracellular cAMP into the cell. The opp operon emerged as the most promising candidate from this screen. The double mutant cyaA-oppA- was constructed and experiments designed to test the function of OppA confirmed our hypothesis. Subsequently, I overexpressed and purified OppA in order to perform biochemical experiments destined to measure the physical interaction between cAMP and OppA. I show that the Opp system is the major importer of cAMP in Escherichia coli. However, it seems that Opp is not the unique importer of cAMP. The other, very interesting candidate is the complex Dpp, known to transport dipeptides. Preliminary experiments revealed a decreased amount of cAMP in strain cyaA-dppA- compared to strain cyaA-. The experiments carried out during the last three years allow us to conclude that the Opp complex is the major importer of cAMP into E. coli and that the Dpp complex is probably a secondary transporter.

Made available in DSpace on 2015-12-06T23:46:48Z (GMT). No. of bitstreams: 0 Previous issue date: 2007 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / OBJETIVO: Estudar a possível influência neurotrófica do nucleotídeo cíclico adenosina monofosfato (AMPc) na regeneração do nervo facial de ratos Wistar. MÉTODO: Trinta e dois animais foram submetidos à transecção completa e sutura imediata do nervo facial direito, sendo divididos em expostos e não expostos à , aplicação tópica de AMPc, com análises comportamentais (movimentação de vibrissas e fechamento da rima palpebral) e histométrica (contagem de fibras mielinizadas) em dois períodos - 14 e 28 dias após a lesão. RESULTADO: Encontramos diferenças estatísticas (pna análise comportamental, no 14° dia, e na análise histométrica, nos 14° e 28° dias, sugerindo uma precocidade na regeneração do nervo facial exposto ao AMPc. CONCLUSÃO: Nosso estudo constatou um possível efeito neurotrófico do AMPc na regeneração do nervo facial em ratos. / PURPOSE: To evaluate the possible neurotrophic influence of cyclic AMP on the facial nerve regeneration of Wistar rats. METHOD: Thirty two animals suffered complete transection and immediate suture of the right facial nerve, having been exposed, or not, to topical administration of cyclic AMP. Behavioral and histometric analysis was undertaken in two times – 14 and 28 days. RESULTS: We show statistical differences (p<0,05) in the behavioral analysis on the 14th day and in the histometric analysis on the 14th and 28th days, suggesting an earlier regeneration of the facial nerve when exposed to cAMP. CONCLUSION: This study demonstrates a possible neurotrophic effect of cAMP on the facial nerve regeneration of rats. / BV UNIFESP: Teses e dissertações

This thesis characterizes adenosine signalization in Drosophila and describes response to adenosine in various cell types. Extracellular adenosine mediates most of its physiological effects through its receptors but recent data also indicate that adenosine transport also has important physiological functions. It was shown in this thesis that adenosine stimulates only cAMP second messenger system in Drosophila cells endogenously expressing AdoR. The pharmacological profile of the DmAdoR was established using the cAMP functional assay. The utility of the agonist 2-chloroadenosine and antagonist SCH58261 were examined in flies in vivo and compared with phenotypes of DmAdoR mutants. The responses of Drosophila cells to adenosine mediated by adenosine transport were also examined. Different cell types exhibited striking differences in adenosine uptake and adenosine recycling that were closely connected with the regulation of carbohydrate and lipid metabolism. This thesis provides an important foundation for the study of interactions between adenosine receptor and adenosine transport.

Contrairement aux autres chimiokine, CX3CL1 a la particularité d'exister sous deux formes protéiques fonctionnelles : une forme soluble chimio-attractante impliquée dans le recrutement leucocytaire comme toutes les chimiokines et une forme membranaire qui confère au couple CX3CL1/CX3CR1, une propriété surprenante de molécule d'adhésion participant à l'arrêt et à la transmigration des leucocytes circulants. Le CX3CR1 appartient à la famille des Récepteurs Couplés aux Protéines Gi, c'est-à-dire qu'il inhibe l'enzyme de synthèse de l'AMP cyclique (AMPc), l'adénylate cyclase. L'étude de la cinétique et du rôle du signal AMPc déclenché en aval du CX3CR1, activé par la forme soluble ou membranaire du CX3CL1 font l'objet de ce travail de thèse. La réponse à la forme membranaire est de même amplitude que celle induite par la forme soluble, mais présente une cinétique considérablement ralentie. Ce ralentissement corrèle avec une moindre internalisation du CX3CR1, qui semble être retenu en surface par le ligand membranaire. Un recrutement plus lent des ? arrestines sur le CX3CR1 activé par le CX3CL1 membranaire renforce cette hypothèse d'une internalisation plus tardive du CX3CR1 comparé à une activation par la forme soluble. Le rôle physiologique de l'AMPc a été également exploré sur les deux fonctions principales du couple CX3CL1/CX3CR1 : le chimiotactisme et l'adhésion. Le rôle inhibiteur de l'AMPc sur ces deux fonctions, confirme une action immunosuppressive de ce messager secondaire. Ces résultats indiqueraient que, grâce à leurs réponses AMPc inhibitrices, les cellules activées par les chimiokines seraient sélectionnées pour une réponse efficace en milieu inflammatoire. / CX3CL1 is a particular chemokine which, in contrast to other chemokines exists in two physiological forms: a soluble form is implicated in chemotaxis and cellular migration like all chemokines; whereas a membranous form confers to the CX3CL1/CX3CR1 couple an adhesive role, contributing in particular to the arrest of circulating leukocytes and their migration to the site of inflammation. The CX3CR1 belongs to the family of Receptor Coupled with Proteins Gi (RCPG), which inhibits the enzyme that syntheses cyclic AMP (cAMP), the adenylyl cyclase. The study of the kinetics and the role of the cAMP signal triggered downstream of CX3CR1, activated by soluble or membranous form of the CX3CL1 are the aims of this work of thesis. The response induced by the membranous form has the same amplitude as the one induced by the soluble form, but has a significantly slowed kinetic. This slowdown correlates with less internalization of CX3CR1, which seems to be retained on the surface by the membranous ligand. A slower recruitment of β-arrestin on the CX3CR1-activated by membranous CX3CL1 strengthens the hypothesis of a later internalization of CX3CR1 compared to activation by the soluble form. The physiological role of cAMP was also explored in the two principal functions of the couple CX3CL1 / CX3CR1: chemotaxis and adhesion. The inhibiting effect of cAMP in these two functions confirms an immunosuppressive action of this second messenger. These results indicate that through their inhibitory cAMP responses, cells activated by chemokines are selected for an effective response in the inflammatory conditions.

No description available.

A population of stromal cells that retains osteogenic capacity in adult bone (adult bone stromal cells or aBSCs) exists and is under intense investigation in relation to osteogenesis and relevant pathology. aBSCs may be different from their embryonic or neonatal counterparts, and are influenced by species-/age-specific and other factors. Mice heterozygous for a null allele of prkar1a (Prkar1a+/-, a gene encoding for cyclic adenosine mono-phosphate (cAMP)-dependent regulatory subunit of protein kinase A (PKA), developed bone lesions that resembled fibrous dysplasia (FD) originated from cAMP-responsive osteogenic cells. Prkar1a +/- mice were crossed with mice heterozygous for catalytic subunit Calpha (Prkaca+/-), the main PKA activity-mediating molecule and generated mouse model with double heterozygosity for prkar1a and prkaca (Prkar1a +/-Prkaca+/-). Unexpectedly, Prkar1a+/-Prkaca+/- mice developed a large number of osseous lesions starting at 2--3 months of age that varied from the rare chondromas in the long bones and the ubiquitous osteochondrodysplasia of tail vertebral bodies to the occasional sarcoma in older animals. Cells from these lesions were fibroblast- and FD-like, and almost always originated from an area proximal to the growth plate and adjacent to endosteal surface of the periosteum; they expanded gradually in the bone marrow space. These cells expressed osteogenic cell markers, showed higher PKA activity that was mostly type II (PKA-II) and display an alternate pattern of catalytic subunit expression, and surprisingly possessed higher cAMP levels. In addition, markers of bone synthesis and lysis were increased. Gene expression profiling not only confirmed an early (progenitor) osteoblastic nature for these cells but also showed a signature that was indicative of mesenchymal-to-epithelial (MET) transition and increased Wnt signaling, particularly the brachyury expression. These studies show that a specific subpopulation of aBSCs can be stimulated in adult bone by PKA-II and altered Calpha activity, generating the only available germline mutant mouse model of a disorder that has similarities to human FD. Along with previous data, these studies also suggest that the effects of cAMP signaling on osteogenesis and stromal cell maintenance and proliferation in mice are age-, bone-, site- but also PKA-type and catalytic subunit-specific. / Parts of the work have been published in Proceedings of the National Academy of Sciences of the United States of America 2010; 107(19):8683--8. / Tsang, Kit Man. / Advisers: Constantine A. Stratakas; Kwak-Pui Fung. / Source: Dissertation Abstracts International, Volume: 72-04, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 144-183). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

This study (1) quantitatively compared steroid production in cultured Y-l mouse adrenal tumor cells exposed to Camel and Carlton-smoke derived residues, and (2) localized the effects in the cell. Basal steroid production was increased by Camel residues but not by Carlton, while ACTH stimulation was interfered with by both residues. Camel basal stimulation was comparable to that of cAMP, and was abolished by Cytochalasin D. The stimulation was also comparable to that of cholera toxin, which activates adenyl cyclase. Results indicate that residue components dissolve in the membrane stimulating adenyl cyclase at a point similar to or before that utilized by cholera toxin for its stimulating effect.

Adhesion of sickle erythrocytes to vascular endothelium may initiate or propagate occlusive events in sickle cell anemia, many of which are accompanied by infection and the associated inflammatory response. Inflammatory markers are also present in sickle patients during asymptomatic periods. Inflammatory cytokines upregulate expression of endothelial adhesion molecules that promote adhesion of sickle erythrocytes. The data in this work demonstrate that after 2 hrs of stimulation with the cytokine TNF- and alpha;, E-selectin, but not VCAM-1 is upregulated on human dermal microvascular endothelial cells. After 6 hrs of TNF- and alpha; stimulation, both VCAM-1 and E-selectin expression are upregulated on MECs, and sickle erythrocytes bind to both receptors. Because strategies to control inflammation-associated adhesion in vivo may need to account for both VCAM-1 and E-selectin mediated events, control of intracellular signaling pathways leading to receptor expression is an attractive strategy for inhibiting adhesion. Cyclic AMP and nitric oxide are two intracellular signaling molecules important to cytokine-induced receptor expression. The data in this work demonstrate that TNF- and alpha; induced VCAM-1 and E-selectin expression on endothelial cells and sickle erythrocyte adhesion are abated by increasing endothelial cyclic AMP concentrations using Forskolin, IBMX, or Bt2cAMP. Conversely, when sickle erythrocytes, rather than endothelial cells, are treated with reagents that increase intracellular cAMP, adhesion to unstimulated endothelial cells is increased in some patients. Treatment of endothelial cells with reagents such as SNP and DETA-NO that increase nitric oxide significantly inhibits VCAM-1, but not E-selectin expression, induced by TNF- and alpha; stimulation and significantly inhibits sickle erythrocyte adhesion. Treatment of sickle erythrocytes directly with these reagents may also inhibit adhesion. Together these data suggest that cAMP- and nitric oxide-dependent signaling are useful therapeutic targets to inhibit cytokine-induced sickle erythrocyte adhesion to endothelium.

Thesis (Ph. D.)--University of Missouri--Columbia, 2001. / Typescript. Vita. Includes bibliographical references (leaves 66-80). Also available on the Internet.