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Although the processes used for temporarily storing and manipulating neural information have been extensively studied at the synaptic level far less attention has been given to the underlying cellular and molecular mechanisms that contribute to change in the intrinsic excitability of neurons. More importantly, how do these mechanisms of plasticity integrate with ongoing mechanisms of regulation of neural intrinsic excitability and, in turn, homeostasis of entire neural circuits? In this dissertation I describe the underlying mechanisms that contribute to persistent neural activity and, more globally, sensorimotor adaptation using weakly electric fish as my model system. Weakly electric fish have evolved a behavior adaptation known as the jamming avoidance response (JAR), and it is this adaptation that allows the organism to elevate its own electrical discharge in response to intraspecific interactions and subsequent distortions of the animal’s electric field. The elevation operates over a wide range and in vivo can last tens of hours upon cessation of a jamming stimulus. I demonstrate that the underlying mechanisms of the adaptation are mediated by calcium-dependent signaling in the pacemaker nucleus and that calcium-mediated phosphorylation plays an important role in the regulation of the long-term frequency elevation (LTFE). I demonstrate using an in vitro brain slice preparation from the weakly electric fish, Apteronotus leptorhynchus that the engram of memory formation depends on the cooperativity of calcium-dependent protein kinases and protein phosphatases. In addition, I show that the memory formation (in the form of LTFE) does not depend on the continued flux of calcium, but rather the phosphorylation events downstream of NMDA receptor activation. Moreover, I describe the differences in the expression of protein phosphatases and protein kinases as they relate to species-specific differences in sensorimotor adaptation. It is important to note that this is the first time that the cooperativity between different isoforms of protein kinase C (PKC) have been shown to play a role in graded long-term change in neuronal activity and, in turn, providing the neural basis of species-specific behavior. The neural adaptation of the electromotor system in weakly electric fish provides an excellent model system to study the underlying cellular and molecular events of vertebrate memory formation. / text

Calcineurin (CaN) is a highly regulated Ser/Thr protein phosphatase that plays critical roles in learning and memory, cardiac development and function, and immune system activation. Alterations in CaN regulation contribute to multiple disease states such as Down syndrome, cardiac hypertrophy, Alzheimer’s disease, and autoimmune disease. In addition, CaN is the target of the immunosuppressant drugs FK506 and cyclosporin A. Despite its importance, CaN regulation is not well understood on a molecular level. Full CaN activation requires binding of calcium-loaded calmodulin (CaM), however little is known about how CaM binding releases CaN’s autoinhibitory domain from the active site. Previous work has demonstrated that the regulatory domain of CaN (RD) is disordered. The binding of CaM to CaN results in RD folding. Folding of the RD in turn causes the autoinhibitory domain (AID) located C-terminal to the RD to be ejected from CaN’s active site. This binding-induced disorder-to-order transition is responsible for the activation of CaN by CaM. In this work, we explore the nature of the disorder in the RD and its transition to an ordered state, demonstrating that the RD exists in a compact disordered state that undergoes further compaction upon CaM binding. We also demonstrate that a single CaM molecule is responsible for binding to and activating CaN. Finally, we determine that the CaM binding to CaN induces an amphipathic helix (the distal helix) C-terminal to the CaM binding region. The distal helix undergoes a hairpin-like chain reversal in order to interact with the surface of CaM, resulting in the removal of the AID from CaN’s active site. We employ site-directed mutagenesis, size-exclusion chromatography, protein crystallography, circular dichroism spectroscopy, fluorescence anisotropy and correlation spectroscopy, and phosphatase activity assays to investigate the ordering of CaN’s regulatory domain, the stoichiometry of CaN:CaM binding, and the impact of the distal helix on CaM activation of CaN.

La non-adhésion (NA) est un enjeu majeur en transplantation rénale (TR). Nous avons réalisé une revue systématique dans laquelle les facteurs liés à la NA sont discutés. Et, sachant que la variabilité des taux sanguins d'anti-calcineurine (CNI) pose la question de NA, nous avons essayé d'identifier les facteurs qui lui sont associés. 37 articles sur l'adhésion ou NA en TR, publiés entre 2009 à 2014, ont été analysés. La NA fluctuait entre 2 et 96% et plusieurs facteurs lui étaient associés : a. jeune, homme, faible support social, sans emploi, faible éducation h. >3 mois post Tx, donneur vivant, >6 comorbidités c. >5 médicaments/j, >2 prises/j d. Croyances et/ou comportements négatifs e. Dépression et/ou anxiété. Puis, nous avons réalisé une étude transversale sur une cohorte de patients à 1 an post greffe de rein. . Les données cliniques, de l'entretien du pharmacien clinicien (PC) et de 6 questionnaires ont été collectées. 408 patients ont été inclus (61.2% d'hommes, âge médian 54 ans). Nous avons comparé 2 groupes selon le coefficient de variation (CV) des CNI : CV<30% (n=302) et >30% (n=106). En analyse univariée la distance hôpital-domicile, la ciclosporine, le délai post greffe et la présence de divergences à la conciliation médicamenteuse, étaient associés à un risque élevé de CV>30%. A l'inverse, le tacrolimus LP conférait un risque plus faible. En analyse multivariée, la présence de divergences était significative (OR=3.2 IC95% [1.21-9.01], p=0.02). Un CV>30% des CNI après 1 an de greffe semble refléter un phénomène de NA pouvant être confirmé par l'entretien avec le PC et constituer un outil simple pour la pratique clinique. / Non-adherence (NA) is a major issue after kidney transplantation (Tx). We realized a systematic review, in which criteria related to NA were discussed. And, considering that calcineurin inhibitors (CNI) blood levels variability raises the question of NA, we tried to identify factors associated to it. 37 studies on adherence and NA in TX, published between 2009 and 2014 were reviewed. NA fluctuated from 2 to 96% and sseveral factors were related to NA: a.Young age, male, low social support, unemployed, low education b. >3 months after Tx, living donor, >6 comorbidities c. >5 drugs/d, > 2 intakes/d d. Negative beliefs and/or behaviors e. Depression and anxiety. Then, we realised a cross sectional study on a cohort of kidney recipients grafted for more than 1 year. We recorded: clinical data, data from a clinical pharmacist (CP) interview and from 6 self-reports. 408 recipients were enrolled (61.2% male, median age 54 years old). We compared 2 groups according to a coefficient of variation (CV) for CNI blood levels: CV<30% (n=302) and >30% (n=106). In univariate analysis, the distance hospital-home, cyclosporine, time since Tx, discrepancies in the reconciliation process were associated with a greater risk of CV>30%. By contrast, tacrolimus once daily conferred a lower risk of CV >30%. In multivariate analysis discrepancies remained significant (OR=3.2 CI 95% [1.21-9.01], p=0.02). ACV >30% for CNI blood levels after lyear post Tx seems to reflect NA, and could easily be confirmed by the CP interview. This could be a simple method to detect NA in clinical routine.

Submitted by Fabíola Silva (fabiola.silva@famerp.br) on 2017-09-29T17:43:14Z No. of bitstreams: 1 camilamontoromfelicio_tese.pdf: 3396879 bytes, checksum: 0568a8c449b9fa50634fd25925b2f3e7 (MD5) / Made available in DSpace on 2017-09-29T17:43:14Z (GMT). No. of bitstreams: 1 camilamontoromfelicio_tese.pdf: 3396879 bytes, checksum: 0568a8c449b9fa50634fd25925b2f3e7 (MD5) Previous issue date: 2016-09-22 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Background: The use of kidneys from extended criteria donors (ECD) is associated with organs of inferior quality and, therefore, a high discarding rate. Clinical and histological tools available to assess non-ideal organs and predict outcomes of ECD have conflicting results. Objectives: To evaluated differences in the intragraft cytokine genes expression in ECD and SCD (standard criteria donors) kidney biopsies (Bx) pre and post-transplant (Tx) and sought possible changes induced by immunosuppressive regimens (ISS). Methodology: SCD and ECD recipients (RTx) were randomized to tacrolimus (Tac) or everolimus (Eve) and Bx were collected pre-implantation (T0 Bx; n = 80) and after 15 (T15 Bx; n = 64) and 90 days (T90 Bx; n = 51) post-Tx. Subgroups SCD-Tac, ECD-Tac, SCD-Eve and ECD-Eve were analyzed for clinical outcomes and clinical data were correlated with intragraft gene expression. Results: Overall, ECD-Eve and ECD-Tac had inferior one-year patient survival and ECD-Tac had lower graft survival than other groups while cytomegalovirus and de novo diabetes pos-Tx were higher in patients with Tac. After one year ECD-Eve patients had higher serum creatinine than ECD-Tac (p = 0.03). Acute rejection rates were higher in Eve group regardless donor type. T0 Bx of ECD showed higher expression of MCP-1, RANTES, TGF-β1 and IL-10 when compared with SCD. TGF-β1 related to the serum creatinine at harvesting the organ while length of donor hospitalization and ECD donor type were associated with upregulation of MCP-1 and RANTES. T15 Bx of patients from both groups taking Eve had increased FOXP3 and MCP-1. RANTES were upregulated only in the SCD-Eve group. Eve was the only variable associated with upregulation of FOXP3, MCP-1 and RANTES. Molecular profiling at T90 was similar except by an increase in FOXP3 transcripts restrict to SCD-Eve group. Positive expression of FOXP3 was associated with the use of Eve and delayed graft function (DGF) with the increased expression of MCP-1 and IL -10. We subtracted from Bx T15 and T90 gene expression values obtained in Bx T0 and two distinct types of molecular profile were found to SCD and ECD. SCD kidneys showed upregulation for all molecules, except TGF-β1 regardless of the ISS system, and ECD kidneys showed negative regulatory molecules for the same, except for slight positive FOXP3 and RANTES expressions. Conclusion: Pre-implantation Bx of ECD kidneys had an inflammatory molecular profile clearly distinct from SCD, with higher expression of RANTES, MCP-1, TGF-β1 and IL-10. Post-Tx, the ISS given modifies the initial cytokine expression pattern at different time points. / Introdução: O uso de rins de doadores com critérios estendidos (DCE) está associado com órgãos de qualidade inferior e, por isso acabam gerando alta taxa de descarte desses órgãos. Os métodos clínicos e histológicos usados como ferramentas para avaliar os órgãos “não ideais” e prever os desfechos dos DCE têm resultados conflitantes. Objetivos: Avaliar as diferenças na expressão gênica de biópsias (Bx) renais em DCE e doadores com critérios padrões (DCS) no pré e pós-transplante (Tx) e buscar possíveis alterações induzidas pelos regimes de imunossupressão (ISS). Metodologia: Receptores (RTx) de DCS e DCE foram randomizados para tacrolimo (Tac) ou everolimo (Eve) e as Bx foram coletadas no pré-transplante (T0 Bx; n = 80) e após 15 (T15 Bx; n = 64) e 90 dias (T90 Bx; n = 51) pós-Tx. Os subgrupos DCS-Tac, DCE-Tac, DCS-Eve e DCE-Eve foram analisados para os desfechos clínicos e os dados foram correlacionados com a expressão gênica intra-enxerto. Resultados: Receptores de DCE-Eve e DCE-Tac tiveram menor sobrevida em um ano pós-Tx. Infecção por citomegalovírus e diabetes mellitus pós-Tx foram maiores em pacientes tratados com Tac. Após um ano, receptores de DCE-Eve apresentaram creatinina sérica (sCr) mais elevada do que DCE-Tac. As taxas de rejeição aguda foram maiores no grupo Eve, independente do tipo de doador. Bx T0 de rins de DCE mostraram maior expressão de MCP-1, RANTES, TGF-β1 e IL-10 quando comparado com rins de DCS. TGF-β1 foi relacionado com a sCr na retirada do órgão, enquanto que o tempo de hospitalização de DCE foi associado com maior expressão de MCP-1 e RANTES. Bx T15 de pacientes dos grupos Eve apresentaram aumento de FOXP3 e MCP-1. A expressão de RANTES foi mais elevada no grupo DCS-Eve. O uso de Eve foi à única variável associada com maior expressão de FOXP3, MCP-1 e RANTES. O perfil das Bx após 90 dias foi similar exceto pelo aumento dos transcritos de FOXP3 restritos ao grupo DCS-Eve. A maior expressão de FOXP3 foi associada com o uso de Eve e a função tardia do enxerto com o aumento na expressão de MCP-1 e IL-10. Foram subtraídos das Bx T15 e T90, os valores de expressão gênica obtidos nas Bx T0, e dois tipos distintos de perfil molecular foram encontrados para DCS e DCE. Rins de DCS apresentaram maior expressão para todas as moléculas, exceto TGF-β1, independentemente do regime de ISS. Os rins de DCE mostraram menor expressão para as mesmas moléculas, exceto por aumento discreto na expressão de FOXP3 e RANTES. Conclusão: Bx pré-implantação de rins de DCE tiveram um perfil molecular inflamatório diferente de rins de DCS, com maior expressão de RANTES, MCP-1, TGF-β1 e IL-10. No pós-Tx, a ISS modificou o padrão inicial de expressão de citocinas nos tempos estudados.

Treating fungal infections is challenging due to the emergence of drug resistance and the limited number of clinically useful antifungal drugs. To improve clinical outcome it will be necessary to develop new antifungal drugs with different mechanisms of action and to discover drugs that improve the fungicidal activity of current antifungals. This study reveals a new role for fungal protein kinase C (PKC) signaling in resistance to drugs targeting the ergosterol biosynthesis pathway in the pathogenic fungus, Candida albicans, and the model yeast, Saccharomyces cerevisiae. PKC signaling enabled survival of antifungal-induced cell membrane stress in part through the mitogen-activated protein kinase (MAPK) cascade and through cross-talk with calcineurin signaling in both species. The molecular chaperone Hsp90, which stabilizes client proteins including calcineurin, also stabilized the terminal C. albicans MAPK, Mkc1. This establishes new circuitry connecting PKC with Hsp90 and calcineurin, and suggests that inhibiting fungal Pkc1 can be a promising strategy for treating life-threatening fungal infections.

Treating fungal infections is challenging due to the emergence of drug resistance and the limited number of clinically useful antifungal drugs. To improve clinical outcome it will be necessary to develop new antifungal drugs with different mechanisms of action and to discover drugs that improve the fungicidal activity of current antifungals. This study reveals a new role for fungal protein kinase C (PKC) signaling in resistance to drugs targeting the ergosterol biosynthesis pathway in the pathogenic fungus, Candida albicans, and the model yeast, Saccharomyces cerevisiae. PKC signaling enabled survival of antifungal-induced cell membrane stress in part through the mitogen-activated protein kinase (MAPK) cascade and through cross-talk with calcineurin signaling in both species. The molecular chaperone Hsp90, which stabilizes client proteins including calcineurin, also stabilized the terminal C. albicans MAPK, Mkc1. This establishes new circuitry connecting PKC with Hsp90 and calcineurin, and suggests that inhibiting fungal Pkc1 can be a promising strategy for treating life-threatening fungal infections.

<p>Although the majority of the population carries <em>Candida spp</em> as normal components of their microflora, these species are important human pathogens that have the ability to cause disease under conditions of immunosuppression or altered host defenses. The spectrum of disease caused by these species ranges from cutaneous infections of the skin, mouth, esophagus and vagina, to life-threatening systemic disease. Despite increases in drug resistance, the antifungal armamentarium has changed little over the past decade. Thus increasing our understanding of the life cycles of these organisms, not only how they propagate themselves, but also how genetic diversity is created within the population is of considerable import. Additionally expanding our knowledge of key signal transduction cascades that are important for cell survival and response to stress will add in developing new antifungal therapies and strategies. </p><p>This thesis addresses both of these key areas of fungal pathogenesis. In the first chapter, we use genome comparisons between parasexual, asexual, and sexual species of pathogenic <em>Candida</em> as a first approximation to answer the question of whether examining genome content alone can allow us to understand why species have a particular life cycle. We start by examining the structure of the mating type locus (<em>MAT</em>) of two sexual species <em>C. lusitaniae</em> and <em>C. guilliermondii</em>. Interestingly, both species are missing either one or two (respectively) canonical transcription factors suggesting that the control of sexual identity and meiosis in these organisms has been significantly rewired. Mutant analysis of the retained transcription factors is used to understand how sexual identity and sporulation are controlled in these strains. Secondly, based on the observation that these species are missing many key genes involved in mating and meiosis, we use meiotic mapping, SPO11 mutant analysis, and comparative genome hybridization to demonstrate that these species are indeed meiotic, but that the meiosis that occurs is occasional unfaithful generating aneuploid and diploid progeny. </p><p>In the second and third chapters we examine the calcineurin signaling pathway, which is crucial for mediated tolerance to cellular stresses including cations, azole antifungals, and passage through the host bloodstream. First, we show that clinical use of calcineurin inhibitors in combination with azole antifungals does not result in resistance to the combination, suggesting that if non-immunosuppressive analogs could be further developed this combinatorial strategy may have great clinical efficacy. Second, we use previous studies of the calcineurin signaling pathway in <em>S. cerevisiae</em> to direct a candidate gene approach for elucidating other components of this pathway in <em>C. albicans</em>. Specifically, we identify homologs of the <em>RCN1, MID1</em>, and <em>CCH1</em> genes, and use a combination of phenotypic assays and heterologous expression studies to understand the roles of these proteins in <em>C. albicans</em>. Although the mutant strains share some phenotypic properties with calcineurin deletion strains, none completely recapitulate a calcineurin mutant. </p><p>In the last chapter, we examine the plausibility of targeting the homoserine dehyrogenase (Hom6) protein in <em>C. albicans</em> and <em>C. glabrata</em> as a novel antifungal strategy. Studies in <em>S. cerevisiae</em> had demonstrated a synthetic lethality between hom6 and fpr1, the gene encoding FKBP12 a prolyl-isomerase that is the binding target of the immunosuppressant FK506. Thiss synthetic lethality was due to the buildup of a toxic intermediate in the methionine and threonine biosynthetic pathway as a result of deletion of hom6 and inhibition of FKBP12. We deleted <em>HOM6</em> from both <em>C. albicans</em> and the more highly drug-resistant species <em>C. glabrata</em>. Studies suggest that regulation of the threonine and methionine biosynthetic pathway in <em>C. albicans</em> has been rewired such that the synthetic lethality between hom6 and FKBP12 inhibition no longer exists. However, in <em>C. glabrata</em> preliminary analysis suggest that similarly to <em>S. cerevisiae</em> hom6 and inhibition of FKBP12 can result in cell death.</p> / Dissertation

Diss. (sammanfattning) Umeå : Umeå universitet, 2005. / Härtill 4 uppsatser.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2007. / Härtill 4 uppsatser.