Browsing by Author "Casal, Margarida"
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- Candida glabrata susceptibility to antifungals and phagocytosis is modulated by acetatePublication . Mota, Sandra; Alves, Rosana; Carneiro, Catarina; Silva, Sónia; Brown, Alistair J.; Istel, Fabian; Kuchler, Karl; Sampaio, Paula; Casal, Margarida; Henriques, Mariana; Paiva, SandraCandida glabrata is considered a major opportunistic fungal pathogen of humans. The capacity of this yeast species to cause infections is dependent on the ability to grow within the human host environment and to assimilate the carbon sources available. Previous studies have suggested that C. albicans can encounter glucose-poor microenvironments during infection and that the ability to use alternative non-fermentable carbon sources, such as carboxylic acids, contributes to the virulence of this fungus. Transcriptional studies on C. glabrata cells identified a similar response, upon nutrient deprivation. In this work, we aimed at analyzing biofilm formation, antifungal drug resistance, and phagocytosis of C. glabrata cells grown in the presence of acetic acid as an alternative carbon source. C. glabrata planktonic cells grown in media containing acetic acid were more susceptible to fluconazole and were better phagocytosed and killed by macrophages than when compared to media lacking acetic acid. Growth in acetic acid also affected the ability of C. glabrata to form biofilms. The genes ADY2a, ADY2b, FPS1, FPS2, and ATO3, encoding putative carboxylate transporters, were upregulated in C. glabrata planktonic and biofilm cells in the presence of acetic acid. Phagocytosis assays with fps1 and ady2a mutant strains suggested a potential role of FPS1 and ADY2a in the phagocytosis process. These results highlight how acidic pH niches, associated with the presence of acetic acid, can impact in the treatment of C. glabrata infections, in particular in vaginal candidiasis.
- Comunicar ciência: a formação em competências transversais dos estudantes de doutoramento da Escola de Ciências da Universidade do MinhoPublication . Salgado, Ana; Côrte-Real, Manuela; Casal, MargaridaOs cientistas são cada vez mais avaliados pela sua capacidade de transmitir ideias e descobertas. Como tal precisam de desenvolver competências de comunicação em diferentes contextos, não apenas entre pares. Nos dias que correm revela-se fundamental abandonar a torre de marfim e dialogar com outros públicos. A Escola de Ciências da Universidade do Minho decidiu investir no desenvolvimento de competências de comunicação de ciência nos últimos anos, através da criação de cursos com diferentes formatos e objetivos.
- Glucose metabolism as a potential therapeutic target in Cytarabine-resistant acute Myeloid leukemiaPublication . Pereira-Vieira, Joana; Weber, Daniela D.; Silva, Sâmia; Barbosa-Matos, Catarina; Granja, Sara; Reis, Rui Manuel; Queirós, Odília; Ko, Young H.; Kofler, Barbara; Casal, Margarida; Baltazar, Fátima; Granja, SaraAltered glycolytic metabolism has been associated with chemoresistance in acute myeloid leukemia (AML). However, there are still aspects that need clarification, as well as how to explore these metabolic alterations in therapy. In the present study, we aimed to elucidate the role of glucose metabolism in the acquired resistance of AML cells to cytarabine (Ara-C) and to explore it as a therapeutic target. Resistance was induced by stepwise exposure of AML cells to increasing concentrations of Ara-C. Ara-C-resistant cells were characterized for their growth capacity, genetic alterations, metabolic profile, and sensitivity to different metabolic inhibitors. Ara-C-resistant AML cell lines, KG-1 Ara-R, and MOLM13 Ara-R presented different metabolic profiles. KG-1 Ara-R cells exhibited a more pronounced glycolytic phenotype than parental cells, with a weaker acute response to 3-bromopyruvate (3-BP) but higher sensitivity after 48 h. KG-1 Ara-R cells also display increased respiration rates and are more sensitive to phenformin than parental cells. On the other hand, MOLM13 Ara-R cells display a glucose metabolism profile similar to parental cells, as well as sensitivity to glycolytic inhibitors. These results indicate that acquired resistance to Ara-C in AML may involve metabolic adaptations, which can be explored therapeutically in the AML patient setting who developed resistance to therapy.
- Lactic acid increases the susceptibility of Candida albicans to fluconazolePublication . Alves, Rosana; Mota, Sandra; Silva, Sónia; Rodrigues, Célia; Brown, Alistair J.; Henriques, Mariana; Casal, Margarida; Paiva, SandraCandida spp. often inhabit niches that are glucose-limited but rich in alternative carbon sources, such as lactate or acetate, an ability that contributes to cells’ virulence. In glucose-poor niches, Candida albicans cells express JEN1 and JEN2 genes encoding the carboxylic acids transporters Jen1 and Jen2, respectively, which have been reported to be important in the early stages of infection. In this work, we aimed at analysing biofilm formation and antifungal drug resistance of C. albicans cells grown either in the presence of glucose or lactic acid. Additionally, we tested the involvement of Jen1 and Jen2 on these processes. Our results show that biofilm formation and susceptibility to fluconazole depend on the carbon source used. Wild-type and jen1jen2 lactic acid-grown cells formed more biofilm biomass, with predominance of yeast cells, than the ones grown in glucose. In the presence of this sugar a hyphae network is observed only for wild-type cells. In the presence of lactic acid, a jen1jen2 mutant strain exhibited a more compact biofilm with higher resistance to fluconazole when compared to the wild type. In the case of planktonic cells, the phenotype was exactly the opposite; the double mutant strain was more susceptible to fluconazole in lactic acid containing media. These findings show that carboxylic acids transporters have an important role in biofilm formation and in the acquisition of resistance to antifungal drugs, supporting the view that adaptation of Candida cells to the carbon source present in host niches affects their pathogenicity.
- Role of the DHH1 Gene in the Regulation of Monocarboxylic Acids Transporters Expression in Saccharomyces cerevisiaePublication . Mota, Sandra; Vieira, Neide; Barbosa, Sónia; Delaveau, Thierry; Torchet, Claire; Saux, Agnès Le; Garcia, Mathilde; Pereira, Ana; Lemoine, Sophie; Coulpier, Fanny; Darzacq, Xavier; Benard, Lionel; Casal, Margarida; Devaux, Frédéric; Paiva, SandraPrevious experiments revealed that DHH1, a RNA helicase involved in the regulation of mRNA stability and translation, complemented the phenotype of a Saccharomyces cerevisiae mutant affected in the expression of genes coding for monocarboxylic-acids transporters, JEN1 and ADY2 (Paiva S, Althoff S, Casal M, Leao C. FEMS Microbiol Lett, 1999, 170∶301–306). In wild type cells, JEN1 expression had been shown to be undetectable in the presence of glucose or formic acid, and induced in the presence of lactate. In this work, we show that JEN1 mRNA accumulates in a dhh1 mutant, when formic acid was used as sole carbon source. Dhh1 interacts with the decapping activator Dcp1 and with the deadenylase complex. This led to the hypothesis that JEN1 expression is post-transcriptionally regulated by Dhh1 in formic acid. Analyses of JEN1 mRNAs decay in wild-type and dhh1 mutant strains confirmed this hypothesis. In these conditions, the stabilized JEN1 mRNA was associated to polysomes but no Jen1 protein could be detected, either by measurable lactate carrier activity, Jen1-GFP fluorescence detection or western blots. These results revealed the complexity of the expression regulation of JEN1 in S. cerevisiae and evidenced the importance of DHH1 in this process. Additionally, microarray analyses of dhh1 mutant indicated that Dhh1 plays a large role in metabolic adaptation, suggesting that carbon source changes triggers a complex interplay between transcriptional and post-transcriptional effects.
- The carboxylic acid transporters Jen1 and Jen2 affect the architecture and fluconazole susceptibility of Candida albicans biofilm in the presence of lactatePublication . Alves, Rosana; Mota, Sandra; Silva, Sónia; F. Rodrigues, Célia; P. Brown, Alistair J.; Henriques, Mariana; Casal, Margarida; Paiva, SandraCandida albicans has the ability to adapt to different host niches, often glucose-limited but rich in alternative carbon sources. In these glucose-poor microenvironments, this pathogen expresses JEN1 and JEN2 genes, encoding carboxylate transporters, which are important in the early stages of infection. This work investigated how host microenvironments, in particular acidic containing lactic acid, affect C. albicans biofilm formation and antifungal drug resistance. Multiple components of the extracellular matrix were also analysed, including their impact on antifungal drug resistance, and the involvement of both Jen1 and Jen2 in this process. The results show that growth on lactate affects biofilm formation, morphology and susceptibility to fluconazole and that both Jen1 and Jen2 might play a role in these processes. These results support the view that the adaptation of Candida cells to the carbon source present in the host niches affects their pathogenicity.
- The transport of carboxylic acids and important role of the Jen1p transporter during the development of yeast coloniesPublication . Paiva, Sandra; Strachotová, Dita; Kučerová, Helena; Hlaváček, Otakar; Mota, Sandra; Casal, Margarida; Palková, Zdena; Váchová, LibušeOn solid substrates, yeast colonies pass through distinct developmental phases characterized by the changes in pH of their surroundings from acidic to nearly alkaline and vice versa. At the beginning of the alkali phase colonies start to produce ammonia, which functions as a quorum-sensing molecule inducing the reprogramming of cell metabolism. Such reprogramming includes, among others, the activation of several plasma membrane transporters and is connected with colony differentiation. In the present study, we show that colony cells can use two transport mechanisms to import lactic acid: a 'saturable' component of the transport, which requires the presence of a functional Jen1p transporter, and a 'non-saturable' component (diffusion) that is independent of Jen1p. During colony development, the efficiency of both transport components changes similarly in central and outer colonial cells. Although the lactate uptake capacity of central cells gradually decreases during colony development, the lactate uptake capacity of outer cells peaks during the alkali phase and is also kept relatively high in the second acidic phase. This lactate uptake profile correlates with the localization of the Jen1p transporter to the plasma membrane of colony cells. Both lactic acid uptake mechanisms are diminished in sok2 colonies where JEN1 expression is decreased. The Sok2p transcription factor may therefore be involved in the regulation of non-saturable lactic acid uptake in yeast colonies.