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Evidence for a Pneumocystis carinii Flo8-like transcription factor: insights into organism adhesion.

ABSTRACT: Pneumocystis carinii (Pc) adhesion to alveolar epithelial cells is well established and is thought to be a prerequisite for the initiation of Pneumocystis pneumonia. Pc binding events occur in part through the major Pc surface glycoprotein Msg, as well as an integrin-like molecule termed PcInt1. Recent data from the Pc sequencing project also demonstrate DNA sequences homologous to other genes important in Candida spp. binding to mammalian host cells, as well as organism binding to polystyrene surfaces and in biofilm formation. One of these genes, flo8, a transcription factor needed for downstream cAMP/PKA-pathway-mediated activation of the major adhesion/flocculin Flo11 in yeast, was cloned from a Pc cDNA library utilizing a partial sequence available in the Pc genome database. A CHEF blot of Pc genomic DNA yielded a single band providing evidence this gene is present in the organism. BLASTP analysis of the predicted protein demonstrated 41 % homology to the Saccharomyces cerevisiae Flo8. Northern blotting demonstrated greatest expression at pH 6.0-8.0, pH comparable to reported fungal biofilm milieu. Western blot and immunoprecipitation assays of PcFlo8 protein in isolated cyst and tropic life forms confirmed the presence of the cognate protein in these Pc life forms. Heterologous expression of Pcflo8 cDNA in flo8?-deficient yeast strains demonstrated that the Pcflo8 was able to restore yeast binding to polystyrene and invasive growth of yeast flo8? cells. Furthermore, Pcflo8 promoted yeast binding to HEK293 human epithelial cells, strengthening its functional classification as a Flo8 transcription factor. Taken together, these data suggest that PcFlo8 is expressed by Pc and may exert activity in organism adhesion and biofilm formation.

SUBMITTER: Kottom TJ

PROVIDER: S-EPMC4724269 | biostudies-literature | 2016 Feb

REPOSITORIES: biostudies-literature

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Evidence for a Pneumocystis carinii Flo8-like transcription factor: insights into organism adhesion.

Kottom Theodore J TJ Limper Andrew H AH

Medical microbiology and immunology 20150728 1

Pneumocystis carinii (Pc) adhesion to alveolar epithelial cells is well established and is thought to be a prerequisite for the initiation of Pneumocystis pneumonia. Pc binding events occur in part through the major Pc surface glycoprotein Msg, as well as an integrin-like molecule termed PcInt1. Recent data from the Pc sequencing project also demonstrate DNA sequences homologous to other genes important in Candida spp. binding to mammalian host cells, as well as organism binding to polystyrene s ...[more]

PMID: 26215665

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Project description:Alveolar macrophages from Pneumocystis carinii-infected hosts are defective in phagocytosis (W. Chen, J. W. Mills, and A. G. Harmsen, Int. J. Exp. Pathol. 73:709-720, 1992; H. Koziel et al., J. Clin. Investig. 102:1332-1344, 1998). Experiments were performed to determine whether this defect is specific for P. carinii organisms. The results showed that these macrophages were unable to phagocytose both P. carinii organisms and fluorescein isothiocyanate (FITC)-conjugated latex beads, indicating that alveolar macrophages from P. carinii-infected hosts have a general defect in phagocytosis. To determine whether this defect correlates with the recently discovered down-regulation of the GATA-2 transcription factor gene during P. carinii infection, alveolar macrophages from dexamethasone-suppressed or healthy rats were treated with anti-GATA-2 oligonucleotides and then assayed for phagocytosis. Aliquots of the alveolar macrophages were also treated with the sense oligonucleotides as the control. Cells treated with the antisense oligonucleotides were found to have a 46% reduction in phagocytosis of P. carinii organisms and a 65% reduction in phagocytosis of FITC-latex beads compared to those treated with the sense oligonucleotides. To determine whether the defect in phagocytosis in alveolar macrophages from P. carinii-infected hosts can be corrected by overexpression of GATA-2, a plasmid containing the rat GATA-2 gene in the sense orientation driven by the cytomegalovirus (CMV) promoter was introduced into alveolar macrophages from P. carinii-infected rats. Aliquots of the same cells transfected with a plasmid containing GATA-2 in the antisense orientation relative to the CMV promoter served as the control. Alveolar macrophages treated with the sense GATA-2 expression construct were found to increase their phagocytic activity by 66% in phagocytosis of P. carinii organisms and by 280% in phagocytosis of FITC-latex beads compared to those that received the antisense GATA-2 construct. The results of this study indicate that GATA-2 plays an important role in the regulation of phagocytosis in alveolar macrophages during P. carinii infection.

Dataset Information

Evidence for a Pneumocystis carinii Flo8-like transcription factor: insights into organism adhesion.

Publications

Evidence for a Pneumocystis carinii Flo8-like transcription factor: insights into organism adhesion.

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