Studying protein-protein interactions has been vital for understanding how proteins function within the cell, how biological processes are strictly regulated by these interactions, and what molecular mechanisms underlie cellular functions and diseases. Recent biochemical and biophysical studies have provided evidence supporting that G protein-coupled receptors (GPCRs) can and do interact with one another to form dimers or larger oligomeric complexes, which may determine the structure and function of GPCRs, including receptor trafficking, scaffolding and signaling. This may help to understand the physiological roles of GPCRs and mechanisms underlying certain disease pathologies and to provide an alternative approach for drug intervention.<p>Cannabinoid CB1 and dopamine D2 receptors are the most common GPCRs in the brain and exert a mutual regulation in brain functions involved in learning, memory and drug addiction. There is structural and functional evidence supporting the idea that CB1 and D2 receptors physically interact with each other in hippocampal and striatal neurons to modulate their functions. Direct evidence supporting a physical interaction between the CB1 and D2 receptors was obtained from cultured HEK293 cells stably coexpressed with both receptors.<p> This research project was designed to critically test the hypothesis that a specific protein sequence (i.e. motif) in the D2 receptor is responsible for in vitro protein-protein interactions between the CB1 and D2 receptors. To reach this goal, fusion proteins containing various domains and motifs of the CB1 and D2 receptors were prepared and then used first to determine the domains of the CB1 and D2 receptors responsible for in vitro protein-protein interactions between CB1 and D2 receptors, and then to identify the specific motifs in the D2 receptor responsible for in vitro CB1 coupling with the D2 receptors. The major method used in this study is in vitro pull-down assay, which uses a purified and tagged bait protein to generate a specific affinity support that is able to bind and purify a prey protein from a lysate sample. The present study provides the first evidence that CB1 intracellular C-terminal (CB1-CT) and D2 intracellular loop 3 (D2-IL3) can directly interact with each other, and that the specific motifs D2-IL3(Ⅳ1) and D2-IL3(Ⅳ3) in the D2 receptor are likely responsible for their in vitro coupling with the CB1 receptors. <p>The results of the present study are invaluable for future research exploring in vivo protein-protein interaction between the CB1 and D2 receptors in the rat striatum by co-immunoprecipitation. Specifically, future studies will determine whether the identified specific motifs D2-IL3(Ⅳ1) and D2-IL3(Ⅳ3) in the D2 receptor are indeed critical for their in vivo coupling with the CB1 receptors.

Studying protein-protein interactions has been vital for understanding how proteins function within the cell, how biological processes are strictly regulated by these interactions, and what molecular mechanisms underlie cellular functions and diseases. Recent biochemical and biophysical studies have provided evidence supporting that G protein-coupled receptors (GPCRs) can and do interact with one another to form dimers or larger oligomeric complexes, which may determine the structure and function of GPCRs, including receptor trafficking, scaffolding and signaling. This may help to understand the physiological roles of GPCRs and mechanisms underlying certain disease pathologies and to provide an alternative approach for drug intervention.<p>Cannabinoid CB1 and dopamine D2 receptors are the most common GPCRs in the brain and exert a mutual regulation in brain functions involved in learning, memory and drug addiction. There is structural and functional evidence supporting the idea that CB1 and D2 receptors physically interact with each other in hippocampal and striatal neurons to modulate their functions. Direct evidence supporting a physical interaction between the CB1 and D2 receptors was obtained from cultured HEK293 cells stably coexpressed with both receptors.<p> This research project was designed to critically test the hypothesis that a specific protein sequence (i.e. motif) in the D2 receptor is responsible for in vitro protein-protein interactions between the CB1 and D2 receptors. To reach this goal, fusion proteins containing various domains and motifs of the CB1 and D2 receptors were prepared and then used first to determine the domains of the CB1 and D2 receptors responsible for in vitro protein-protein interactions between CB1 and D2 receptors, and then to identify the specific motifs in the D2 receptor responsible for in vitro CB1 coupling with the D2 receptors. The major method used in this study is in vitro pull-down assay, which uses a purified and tagged bait protein to generate a specific affinity support that is able to bind and purify a prey protein from a lysate sample. The present study provides the first evidence that CB1 intracellular C-terminal (CB1-CT) and D2 intracellular loop 3 (D2-IL3) can directly interact with each other, and that the specific motifs D2-IL3(Ⅳ1) and D2-IL3(Ⅳ3) in the D2 receptor are likely responsible for their in vitro coupling with the CB1 receptors. <p>The results of the present study are invaluable for future research exploring in vivo protein-protein interaction between the CB1 and D2 receptors in the rat striatum by co-immunoprecipitation. Specifically, future studies will determine whether the identified specific motifs D2-IL3(Ⅳ1) and D2-IL3(Ⅳ3) in the D2 receptor are indeed critical for their in vivo coupling with the CB1 receptors.

Made available in DSpace on 2014-07-29T15:16:35Z (GMT). No. of bitstreams: 1 Dissertacao FINAL_EF_corrigida_BC-UFG.pdf: 1485117 bytes, checksum: ecdc9729cc08da2832a6566c39052f65 (MD5) Previous issue date: 2010-01-28 / The cell wall of pathogenic microbes acts as an initial barrier that is in contact with hostile environments. Besides functioning as a mechanical barrier, it harbours an immunogenic macromolecules arsenal. One of the ways that proteins can be associated to the cell wall, it is through GPI anchor. The hydrophobic C-terminal end of the &#946;-1,3-glucanosyltransferase enzyme of the human pathogenic fungus Paracoccidioides brasiliensis is characteristic of GPI anchored proteins. The &#946;-1,3-glucan assembling and rearrangement are essential since this molecule acts as a scaffold to support cell wall proteins and polysaccharides. In the thermodimorphic fungus P. brasiliensis, &#946;-1,3-glucan is found predominantly in mycelium form and &#945;-1,3-glucan is predominant in the yeast form. In this work, it was screened possible protein-protein interactions performed by &#946;-1,3-glucanosyltransferase 1 of P. brasiliensis (PbGel1p). To obtain these results, a P. brasiliensis cDNA library was screened with PbGel1p using the Saccharomyces cerevisiae two hybrid system. In addition, pull-down assay was used as an in vitro complementary technique to isolate proteins that interact direct or indirectly with PbGel1p. It was screened 38 gene products using two hybrid system and it was identified 3 proteins using the pull-down assay associated with mass spectrometry. The PbGel1p role in the cell wall maintenance and remodeling was indicated through the analysis of screened interactions, like alpha-glucosides permease, acid phosphatase, GDSL lipase, septin, actin, tubulin, HSP90 and pyruvate kinase. Furthermore, nuclear localization of PbGel1p and its role in the locus-specific transcriptional silencing were suggested based on such interactions: Qde2 argonaute, transcription elongation factor spt6, others transcription factors and ATP-citrate synthase. Therefore, this study indicated, for the first time, that PbGel1p has multiple location and it participates either in roles classically described for glucanosyltransferases, as the cell wall remodeling, or in recently described functions for this family of proteins, as the locus-specific transcriptional silencing. / A parede celular de microrganismos patogênicos atua como uma barreira inicial no contato entre o parasito e o hospedeiro. Além de funcionar como uma barreira mecânica, ela abriga um arsenal de macromoléculas imunogênicas. Uma forma pela qual as proteínas estão associadas à parede celular é por meio de âncoras-GPI. A extremidade carboxila hidrofóbica da enzima &#946;-1,3-glicanosiltransferase do fungo patogênico humano Paracoccidioides brasiliensis é característica de proteínas GPI-ancoradas. A montagem e o rearranjo de &#946;-1,3- glicana são de fundamental importância porque esta molécula serve como um esqueleto sobre o qual outros polissacarídeos e proteínas da parede celular estão associados. No fungo termodimórfico P. brasiliensis, &#946;-1,3-glicana é encontrada prioritariamente em micélio, sendo &#945;-1,3-glicana predominante em levedura. Foram rastreadas neste trabalho possíveis interações proteína-proteína realizadas pela &#946;-1,3-glicanosiltransferase 1 de P. brasiliensis (PbGel1p). Para isso utilizou-se a técnica de duplo-híbrido em Saccharomyces cerevisiae, rastreando-se uma biblioteca de cDNA do fungo P. brasiliensis com a enzima estudada. Adicionalmente, foi utilizado, como técnica complementar, o ensaio de pull-down, que isolou in vitro proteínas que interagem direta ou indiretamente com a PbGel1p. Foi possível rastrear 38 produtos gênicos através do sistema de duplo híbrido e isolar três proteínas pelo ensaio de pull-down, identificadas por espectrometria de massas. O papel da PbGel1p na manutenção e no remodelamento da parede celular do fungo foi indicado através da análise das interações rastreadas, como permease de &#945;-glicosídeos, fosfatase ácida, lipase da família GDSL, septina, actina, tubulina, HSP90 e piruvato quinase. Além disso, foram sugeridos a localização da PbGel1p no núcleo das células do fungo e seu papel no silenciamento gênico mediado por alterações estruturais, por meio do rastreamento das seguintes proteínas ligantes a PbGel1p: argonauta Qde2, fator de alongamento transcricional spt6, outros fatores transcricionais e ATP-citrato sintase. Portanto, este estudo indicou, pela primeira vez, que PbGel1p tem localização múltipla e participa tanto de funções classicamente descritas para glicanosiltransferases, como o remodelamento da parede celular, quanto de funções recentemente descritas para essa família de proteínas, como o silenciamento transcricional sítio-específico.

Submitted by Ana Caroline Costa (ana_caroline212@hotmail.com) on 2018-11-30T18:44:39Z No. of bitstreams: 2 Dissertação - Thaylla Horbylon Nascimento - 2017.pdf: 2748481 bytes, checksum: 12679d6d81f935cee0a82be36ee7480a (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2018-12-03T13:14:23Z (GMT) No. of bitstreams: 2 Dissertação - Thaylla Horbylon Nascimento - 2017.pdf: 2748481 bytes, checksum: 12679d6d81f935cee0a82be36ee7480a (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2018-12-03T13:14:23Z (GMT). No. of bitstreams: 2 Dissertação - Thaylla Horbylon Nascimento - 2017.pdf: 2748481 bytes, checksum: 12679d6d81f935cee0a82be36ee7480a (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-12-12 / Outro / Paracoccidioides comprises the genus of fungi causing paracoccidioidomycosis. The research of new treatments, especially those based on inhibition of metabolic pathways important for microorganisms has gained prominence and the aspartate pathway, necessary for the biosynthesis of threonine, isoleucine and methionine in microorganisms, is not found in humans. Catalyzing the second step of this pathway, we found aspartate semialdehyde dehydrogenase (ASADH), which has not yet been characterized in Paracoccidioides spp. and has no substituents in its catalytic function in the aspartate pathway. Thus, it is of interest the determination of its biological properties experimentally that their biological properties be determined experimentally. ASADH from Pb18 was cloned into vector pGEX-4T3, expressed in E. coli Stellar cells and purified on a glutathione-sepharose column. Then, antibodies were produced and used in Western blot assay to confirm protein expression. The pull-down-GST assay was performed and allowed the identification of complexes of interactions between ASADH and soluble proteins present in total protein extract of the yeast form of Pb18. Interactions with proteins of several functional categories, among them those related to the metabolism of threonine, isoleucine and methionine, were found, reinforcing the performance of ASADH in the amino acid biosynthesis of Pb18, as well as proteins related to substrate supply to the aspartate pathway and proteins that use metabolites of this pathway. Interactions with proteins involved in other metabolic pathways were also observed, as well as unprecedented interactions, suggesting the importance of ASADH in the functional processes of microorganisms. / Paracoccidioides compreende o gênero de fungos causadores da paracoccidioidomicose. A pesquisa de novos tratamentos, sobretudo aqueles baseados em inibição de vias metabólicas importantes para micro-organismos, tem ganhado destaque e a via do aspartato não é encontrada em humanos. A via do aspartato é necessária para a síntese de treonina, isoleucina e metionina. Catalisando o segundo passo dessa via, encontramos a aspartato semialdeído desidrogenase (ASADH), que ainda não foi caracterizada em Paracoccidioides spp. e não possui substituintes em sua função catalítica na via do aspartato. Assim, é de interesse que suas propriedades biológicas sejam determinadas experimentalmente. A ASADH proveniente de Pb18 foi clonada em vetor pGEX-4T3, expressa em células E. coli Stellar e purificada em coluna de glutationa-sefarose. Em seguida, anticorpos foram produzidos e utilizados em ensaio de Western-blot para confirmar a expressão proteica. O ensaio de pull-down-GST foi realizado e permitiu a identificação de complexos de interações entre a ASADH e proteínas solúveis presentes em extrato proteico total da forma de levedura de Pb18. Foram encontradas interações com proteínas de diversas categorias funcionais, dentre elas relacionadas ao metabolismo de treonina, isoleucina e metionina, reforçando a atuação da ASADH na biossíntese de aminoácidos de Pb18, bem como proteínas relacionadas ao fornecimento de substrato para a via do aspartato e proteínas que utilizam os metabólitos dessa via. Também foram observadas interações com proteínas envolvidas em outras vias metabólicas, assim como interações inéditas, sugerindo a importância de ASADH nos processos funcionais de micro-organismos.

An increasing interest in non-canonical nucleic acid structures has drawn the attention of the scientific community during the last few decades. One such structure, the G-quadruplex, has been the focus of an increasing number of scientists as G-quadruplexes are believed to play a role in biological processes such as telomere integrity and gene expression. Their existence in vivo is largely unproven but they have stimulated a lot of research into small molecules that interact with them. The development of a new class of such molecules is described in this thesis. A member of this family showed to be very selective in stabilising one particular G-quadruplex. The further development of another family of G-quadruplex interacting small molecules is also presented in this thesis and some of their effects in cellulo were assessed. Based on the scaffold of this family, an affinity probe was developed, which can mediate the isolation of its nucleic acid targets from human cells. This is the first example of the use of a small molecule with an affinity tag that has been used to isolate a nucleic acid target in a structure specific manner from human cells.

Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2016-08-04T11:29:03Z No. of bitstreams: 2 Dissertação - Mirian Vieira Teixeira - 2016.pdf: 1440228 bytes, checksum: a429eb9e9ac048fbcc06d59fca852c03 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2016-08-04T11:30:39Z (GMT) No. of bitstreams: 2 Dissertação - Mirian Vieira Teixeira - 2016.pdf: 1440228 bytes, checksum: a429eb9e9ac048fbcc06d59fca852c03 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2016-08-04T11:30:40Z (GMT). No. of bitstreams: 2 Dissertação - Mirian Vieira Teixeira - 2016.pdf: 1440228 bytes, checksum: a429eb9e9ac048fbcc06d59fca852c03 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2016-03-10 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / Fundação de Amparo à Pesquisa do Estado de Goiás - FAPEG / The Paracoccidioides genus comprises a complex of pathogenic fungi that are the etiologic agents of paracoccidioidomycosis (PCM), the most prevalent systemic mycosis in Latin America. The infection begins after inhalation of fungal propagules, which reach the epithelium of the alveoli where the transition from the mycelial to the pathogenic yeast form. Host elevated temperature triggers the morphological switch, which is necessary for fungal pathogenicity. The cAMP/protein kinase A (PKA) signaling pathway has been shown to be important in controlling morphological changes and the pathogenicity of several pathogenic fungi. Evidence also highlights the importance of the cAMP/PKA pathway in the morphological transition of Paracoccidioides. PKA is the major effector of this signaling pathway. The protein is an inactive tetramer composed of regulatory subunit, encoded by the BCY1 gene; and catalytic subunit, encoded by the TPK2 gene. Upon binding of cAMP to the regulatory subunits, the catalytic subunits dissociate and become active. Activated PKA subsequently phosphorylates protein kinases, transcription factors, and other substrates to control several biological processes. In this study, we evaluated the expression and interactions of Tpk2 protein Paracoccididioides spp. The Tpk2 is present in mycelium decreased during the initial stages of transition phases, and increases again at the end of differentiation, with maximal levels in yeast. We analyzed the interactions of recombinant Tpk2p with Paracoccidioides proteins using pull-down assays followed by MS analysis. Two interacting proteins were identified: the heat shock protein 90 (Hsp90) and a conserved hypothetical protein with a MFS domain. Hsp90 is involved in the regulation of morphogenesis, development and virulence in several thermal dimorphic fungi. These data are important for understanding the mechanisms that trigger the transition phases in Paracoccidioides. / O gênero Paracoccidioides compreende um complexo de fungos patogênicos, que são os agentes etiológicos da paracoccidioidomicose (PCM), a micose sistêmica mais prevalente na América Latina. A infecção inicia-se com a inalação de propágulos do fungo, que atingem o epitélio dos alvéolos pulmonares, onde ocorre à transição da forma de micélio para a forma patogênica, de levedura. Há evidências de que a temperatura seja o principal fator responsável pela diferenciação celular desses fungos, e sua patogenicidade é frequentemente associada com a transição dimórfica. A via de sinalização cAMP/ proteína quinase A (PKA) controla alterações morfológicas e de virulência/patogenicidade em várias espécies de fungos patogênicos humanos. Evidências apontam também para a importância da via cAMP/PKA em Paracoccidioides spp. A PKA é o principal efetor desta via de sinalização. A proteína na forma inativa é um tetrâmero composto de subunidade regulatória, codificada pelo gene BCY1; e subunidade catalítica, codificada pelo gene TPK2. Após a ligação de cAMP às subunidades regulatórias, as subunidades catalíticas dissociam-se e tornam-se ativas. Ativada a PKA fosforila proteína-quinases, fatores de transcrição, e outros substratos para controlar diversos processos biológicos. Neste estudo, avaliamos a expressão e as interações da proteína Tpk2 de Paracoccididioides spp. A Tpk2 está presente em micélio, diminui nos estágios iniciais da transição de fases e volta a aumentar no final da diferenciação, apresentando níveis máximos na levedura. Foram analisadas as interações de Tpk2p recombinante com proteínas de Paracoccidioides utilizando ensaios de pull-down, seguido por análise de MS. Foram identificadas duas proteínas que interagem: a proteína de choque térmico 90 (Hsp90) e uma proteína hipotética conservada com um domínio MFS. Hsp90 está envolvido na regulação da morfogênese, desenvolvimento e virulência em vários fungos dimórficos térmicos. Estes dados são importantes para entendimento dos mecanismos que disparam a transição de fases em Paracoccidioides spp.

Submitted by Cássia Santos (cassia.bcufg@gmail.com) on 2017-09-01T13:05:01Z No. of bitstreams: 2 Dissertação - Wanderson Lucas da Costa - 2017.pdf: 3043089 bytes, checksum: 32c1b9c81dae778ab37d939fdba41eb5 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2017-09-15T13:46:23Z (GMT) No. of bitstreams: 2 Dissertação - Wanderson Lucas da Costa - 2017.pdf: 3043089 bytes, checksum: 32c1b9c81dae778ab37d939fdba41eb5 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-09-15T13:46:23Z (GMT). No. of bitstreams: 2 Dissertação - Wanderson Lucas da Costa - 2017.pdf: 3043089 bytes, checksum: 32c1b9c81dae778ab37d939fdba41eb5 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-08-07 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Paracoccidioides spp. are thermodymorphic fungi that when inhaled by humans, these conidia find a favorable environment, changing to the yeast phase and becoming pathogenic causing paracoccidioidomycosis (PCM), one of the most prevalent systemic mycoses in Brazil. Some antifungals are used in the treatment of PCM. Treatment depends on the patient's progression and tolerability of each drug, but their treatment may be for long periods and cause various side effects in the patient. The chiquimate pathway is coordinated by 7 enzymes that perform consecutive steps to convert erythrose-4-phosphate and phosphoenol pyruvate (PEP) into chorismate. In microorganisms, this pathway is involved in the production of the amino acids phenylalanine, tyrosine and tryptophan; These amino acids are essential to the maintenance of these organisms. In this work, pGEX4T3 vector cloning and heterologous expression of Pb18 EPSP synthase belonging to the chiquimate pathway were performed. This protein was expressed in E. coli (DE3) strain and purified. Antibodies were produced for expression analysis of the protein in Western blot. The modeling of EPSP synthase was performed aiming to identify the amino acids involved in the active site. The pull down-GST assay with soluble Pb18 proteins allowed the identification of 40 proteins that interact with EPSP synthase. These proteins belong to different functional categories, which are involved with the availability of phosphoenol pyruvate, the substrate necessary for the functioning of the chiquimate pathway. / Paracoccidioides spp. são fungos termodimórficos que ao serem inalados pelo ser humano, esses conídios encontram um ambiente propício, mudando para a fase de levedura e tornando-se patogênico causando a paracoccidioidomicose (PCM), umas das micoses sistêmicas de maior prevalência no Brasil. Alguns antifúngicos são empregados no tratamento da PCM. O tratamento depende do avanço da doença e da capacidade de tolerância do paciente a cada medicamento, mas o seu tratamento pode ser por longos períodos e causando diversos efeitos colaterais no paciente. A via do chiquimato é coordenada pela ação de 7 enzimas que realizam passos consecutivos para transformar a eritrose-4-fosfato e fosfoenol piruvato (PEP) em corismato. Em micro-organismos, esta via está envolvida com a produção dos aminoácidos fenilalanina, tirosina e triptofano; estes aminoácidos são essenciais à manutenção desses organismos. Neste trabalho foi realizado a clonagem em vetor pGEX4T3 e expressão heteróloga da EPSP–sintase de Pb18 pertencente à via do chiquimato. Essa proteína foi expressa em linhagem E. coli (DE3) e purificada. Os anticorpos foram produzidos para análise da expressão da proteína em Western blot. A modelagem da EPSP-sintase foi realizada visando identificar os aminoácidos envolvidos no sítio ativo. O ensaio de pull down-GST com proteínas solúveis de Pb18 possibilitou a identificação de 40 proteínas que interagem com EPSP-sintase. Essas proteínas pertencem a diferentes categorias funcionais, as quais estão envolvidas com a disponibilidade de fosfoenol piruvato, substrato necessário para o funcionamento da via do chiquimato.

Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2017-04-24T13:45:43Z No. of bitstreams: 2 Dissertação - Andrea Leite Camargo Santana - 2017.pdf: 3114758 bytes, checksum: 4fa4c3e9a2e7062f2940b053f1250619 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2017-04-24T13:46:06Z (GMT) No. of bitstreams: 2 Dissertação - Andrea Leite Camargo Santana - 2017.pdf: 3114758 bytes, checksum: 4fa4c3e9a2e7062f2940b053f1250619 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-04-24T13:46:06Z (GMT). No. of bitstreams: 2 Dissertação - Andrea Leite Camargo Santana - 2017.pdf: 3114758 bytes, checksum: 4fa4c3e9a2e7062f2940b053f1250619 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-03-29 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / Paracoccidioides fungi are the causative agents of paracoccidioidomycosis, an endemic disease in Latin America with great socioeconomic importance. Inhalation of spores, the infectious particles of the fungus, is a common way to get the infection. Its treatment is slow and generates long-term side effects making it necessary to study new metabolic pathways that can be potential targets for antifungal development. In this context, stands out the chiquimate pathway in Paracoccidioides spp., related to the production of chorismate and production of aromatic amino acids, and the chorismate synthase involved in the last stage of this pathway. The chorismate synthase from Pb18 was cloned into pGEX-4T3 vector, expressed in pLysS cells and purified on a glutathione-sepharose column. Antibodies were produced from the immunization of mice with the recombinant protein obtained and used in Western blot assay to confirm protein expression. For characterization of the enzyme, its modeling was carried out. Pull-down-GST assay was performed to identify interactions between the chorismate synthase and soluble proteins present in total protein extract of Pb18. The interactions found included proteins of different functional categories related to protein synthesis, related with metabolism of common intermediates such as folate and quinolinate or related with the availability of ATP, phosphoenolpyruvate and erythrose-4-phosphate required in the chiquimate pathway. Unexpected interactions with proteins of the cell cycle and also with regulating proteins of the cell division process were observed. / Fungos do gênero Paracoccidioides são os agentes causadores da paracoccidioidomicose, uma doença endêmica na América Latina de grande importância socioeconômica. A inalação de esporos, partículas infecciosas do fungo, é uma forma comum de adquirir a infecção. O seu tratamento é lento e gera efeitos colaterais tornando necessário o estudo de novas vias metabólicas que sejam potenciais alvos para o desenvolvimento de antifúngicos. Nesse contexto, destaca-se a via do chiquimato em Paracoccidioides spp., relacionada à obtenção de corismato e produção de aminoácidos aromáticos, sendo corismato sintase a enzima envolvida na última etapa dessa via. A corismato sintase proveniente de Pb18 foi clonada em vetor pGEX-4T3, expressa em células pLysS e purificada em coluna de glutationa-sefarose. Anticorpos foram produzidos a partir da imunização de camundongos com a proteína recombinante obtida e utilizados em ensaio de Western blot a fim de confirmar a expressão proteica. A modelagem da corismato sintase foi realizada e os aminoácidos envolvidos no sítio ativo foram identificados. Ensaios de pull-down-GST foram realizados a fim de identificar os complexos de interações entre a corismato sintase e proteínas solúveis presentes em extrato proteico total de Pb18. As interações encontradas incluíram proteínas de diferentes categorias funcionais relacionadas à síntese proteica, ao metabolismo de intermediários comuns como folato e quinolinato ou ainda com a disponibilidade de ATP, fosfoenolpiruvato e eritrose-4-fosfato necessários na via do chiquimato. Interações inesperadas com proteínas do ciclo celular e também com proteínas reguladoras do processo de divisão celular foram observadas.

La protéine Vif du VIH-1 contrecarre le facteur de restriction APOBEC3G (A3G) en diminuant son niveau d'expression dans les cellules infectées. Ceci est mis en œuvre entre autres par l'inhibition de sa traduction, un mécanisme encore peu compris. La première partie de ma thèse contribue à la caractérisation d'une petite ORF (uORF) qui se situe dans la 5'-UTR de l'ARNm d'A3G et d'A3F en amont de leurs ORF respectives. Cette uORF s'est révélée cruciale pour la régulation de la traduction d'A3G en présence et absence de Vif. Dans la deuxième partie de cette thèse, différents protocoles ont été mis en œuvre pour identifier les protéines associées avec l'ARNm d'A3G, qui pourraient jouer un rôle dans le mécanisme d'inhibition traductionnelle d'A3G par Vif. Ainsi, plusieurs protéines ont été identifiées dont la présence sur l'ARNm d'A3G semble modulée par Vif. / The HIV-1 Vif protein counteracts the restriction factor APOBEC3G (A3G) by downregulating its expression level in infected cells. This is achieved in different ways, one of which is translational inhibition, a mechanism that is still poorly understood. The first part of my thesis contributes to the characterization of a small upstream ORF (uORF), that is found in the 5'-UTR of A3G and A3F mRNAs. This uORF has been found to be crucial for regulation of A3G translation and is necessary to allow Vif-mediated translational inhibition. In the second part of this thesis, different protocols have been set up in order to identify A3G mRNA-associated cellular proteins which might play a role in the mechanism of Vif-mediated translational inhibition. Several proteins, whose presence on A3G mRNA seems to be modulated by Vif have been identified.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.