scholarly journals RIM101-Dependent and -Independent Pathways Govern pH Responses in Candida albicans

2000 ◽  
Vol 20 (3) ◽  
pp. 971-978 ◽  
Author(s):  
Dana Davis ◽  
R. Bryce Wilson ◽  
Aaron P. Mitchell
Keyword(s):  
Gene Expression ◽  
Candida Albicans ◽  
Cellular Differentiation ◽  
Alkaline Ph ◽  
Ph Response ◽  
Pcr Product ◽  
Ph Dependent ◽  
Ph Range ◽  
The One

ABSTRACT Growth and differentiation of Candida albicans over a broad pH range underlie its ability to infect an array of tissues in susceptible hosts. We identified C. albicans RIM101,RIM20, and RIM8 based on their homology to components of the one known fungal pH response pathway. PCR product-disruption mutations in each gene cause defects in three responses to alkaline pH: filamentation, induction of PRA1and PHR1, and repression of PHR2. We find thatRIM101 itself is an alkaline-induced gene that also depends on Rim20p and Rim8p for induction. Two observations indicate that a novel pH response pathway also exists. First, PHR2 becomes an alkaline-induced gene in the absence of Rim101p, Rim20p, or Rim8p. Second, we created strains in which Rim101p activity is independent of Rim20p and Rim8p; in these strains, filamentation remains pH dependent. Thus, pH governs gene expression and cellular differentiation inC. albicans through both RIM101-dependent andRIM101-independent pathways.

scholarly journals Effect of Environmental pH on Morphological Development of Candida albicans Is Mediated via the PacC-Related Transcription Factor Encoded by PRR2

1999 ◽  
Vol 181 (24) ◽  
pp. 7524-7530 ◽  
Author(s):  
Ana M. Ramon ◽  
Amalia Porta ◽  
William A. Fonzi
Keyword(s):  
Gene Expression ◽  
Transcription Factor ◽  
Candida Albicans ◽  
Feedback Loop ◽  
Response Regulator ◽  
Morphological Development ◽  
Alkaline Ph ◽  
Ph Response ◽  
Related Transcription Factor ◽  
Ph Dependent

ABSTRACT The ability to respond to ambient pH is critical to the growth and virulence of the fungal pathogen Candida albicans. This response entails the differential expression of several genes affecting morphogenesis. To investigate the mechanism of pH-dependent gene expression, the C. albicans homolog of pacC, designated PRR2 (for pH response regulator), was identified and cloned. pacC encodes a zinc finger-containing transcription factor that mediates pH-dependent gene expression inAspergillus nidulans. Mutants lacking PRR2 can no longer induce the expression of alkaline-expressed genes or repress acid-expressed genes at alkaline pH. Although the mutation did not affect growth of the cells at acid or alkaline pH, the mutants exhibited medium-conditional defects in filamentation. PRR2was itself expressed in a pH-conditional manner, and its induction at alkaline pH was controlled by PRR1. PRR1 is homologous to palF, a regulator of pacC. Thus,PRR2 expression is controlled by a pH-dependent feedback loop. The results demonstrate that the pH response pathway ofAspergillus is conserved and that this pathway has been adapted to control dimorphism in C. albicans.

scholarly journals PRR1, a Homolog of Aspergillus nidulans palF, Controls pH-Dependent Gene Expression and Filamentation inCandida albicans

1999 ◽  
Vol 181 (24) ◽  
pp. 7516-7523 ◽  
Author(s):  
Amalia Porta ◽  
Ana M. Ramon ◽  
William A. Fonzi
Keyword(s):  
Gene Expression ◽  
Aspergillus Nidulans ◽  
Response Regulator ◽  
Null Mutant ◽  
Alkaline Ph ◽  
Hyphal Development ◽  
Ph Response ◽  
Multiple Components ◽  
Ph Dependent ◽  
Incandida Albicans

ABSTRACT The pH of the environment has been implicated in controlling the yeast-hypha transition and pathogenesis of Candida albicans. Several C. albicans genes, includingPHR1 and PHR2, are pH dependent in their expression. To investigate the mechanism of pH-dependent expression, we have cloned and characterized PRR1 (for pH response regulator). PRR1 is homologous to palF, a component of the pH response pathway in Aspergillus nidulans. Expression of PRR1 was itself pH dependent, being maximal at acid pH but reduced severalfold at alkaline pH. In aprr1 null mutant the alkaline-induced expression ofPHR1 was completely abolished. Conversely, expression ofPHR2 was no longer repressed at alkaline pH. Aprr1 null mutant exhibited no morphological abnormalities at either pH; however, it lost the ability to form hyphae on medium 199 and on 10% serum plates. The ability to filament on serum was not restored by forced expression of PHR1, indicating that additional PRR1-dependent genes are required for hyphal development. These developmental genes appear to be distinct from those controlled by the developmental regulator EFG1, since theEFG1-dependent gene HWP1 was expressed normally in the prr1 null mutant. We conclude that PRR1encodes a component of the pH-dependent response pathway in C. albicans and that this pathway regulates the expression of multiple components of hyphal development.

scholarly journals Candida albicans RIM101 pH Response Pathway Is Required for Host-Pathogen Interactions

2000 ◽  
Vol 68 (10) ◽  
pp. 5953-5959 ◽  
Author(s):  
Dana Davis ◽  
John E. Edwards ◽  
Aaron P. Mitchell ◽  
Ashraf S. Ibrahim
Keyword(s):  
Gene Expression ◽  
Endothelial Cells ◽  
Candida Albicans ◽  
Marked Reduction ◽  
Endothelial Damage ◽  
Systemic Candidiasis ◽  
Ph Response

ABSTRACT The ability of Candida albicans to respond to diverse environments is critical for its success as a pathogen. TheRIM101 pathway controls gene expression and the yeast-to-hyphal transition in C. albicans in response to changes in environmental pH in vitro. In this study, we found that theRIM101 pathway is necessary in vivo for pathogenesis. First, we show thatrim101−/rim101− andrim8−/rim8− mutants have a significant reduction in virulence using the mouse model of hematogenously disseminated systemic candidiasis. Second, these mutants show a marked reduction in kidney pathology. Third, therim101−/rim101− andrim8−/rim8− mutants show defects in the ability to damage endothelial cells in situ. Finally, we show that an activated allele of RIM101, RIM101-405, is a suppressor of the rim8− mutation in vivo as it rescues the virulence, histological, and endothelial damage defects of the rim8−/rim8− mutant. These results demonstrate that the RIM101 pathway is required for C. albicans virulence in vivo and that the function of Rim8p in pathogenesis is to activate Rim101p.

scholarly journals Evidence for Novel pH-Dependent Regulation of Candida albicans Rim101, a Direct Transcriptional Repressor of the Cell Wall β-Glycosidase Phr2

2006 ◽  
Vol 5 (9) ◽  
pp. 1550-1559 ◽  
Author(s):  
Yong-Un Baek ◽  
Samuel J. Martin ◽  
Dana A. Davis
Keyword(s):  
Gene Expression ◽  
Candida Albicans ◽  
Binding Site ◽  
Signal Transduction Pathway ◽  
Proteolytic Processing ◽  
Alkaline Ph ◽  
Ph Change ◽  
Response Gene ◽  
Alkaline Environments

ABSTRACT Candida albicans is a commensal fungus of mucosal surfaces that can cause disease in susceptible hosts. One aspect of the success of C. albicans as both a commensal and a pathogen is its ability to adapt to diverse environmental conditions, including dramatic variations in environmental pH. The response to a neutral-to-alkaline pH change is controlled by the Rim101 signal transduction pathway. In neutral-to-alkaline environments, the zinc finger transcription factor Rim101 is activated by the proteolytic removal of an inhibitory C-terminal domain. Upon activation, Rim101 acts to induce alkaline response gene expression and repress acidic response gene expression. Previously, recombinant Rim101 was shown to directly bind to the alkaline-pH-induced gene PHR1. Here, we demonstrate that endogenous Rim101 also directly binds to the alkaline-pH-repressed gene PHR2. Furthermore, we find that of the three putative binding sites, only the −124 site and, to a lesser extent, the −51 site play a role in vivo. In C. albicans, the predicted Rim101 binding site was thought to be CCAAGAA, divergent from the GCCAAG site defined in Aspergillus nidulans and Saccharomyces cerevisiae. Our results suggest that the Rim101 binding site in C. albicans is GCCAAGAA, but slight variations are tolerated in a context-dependent fashion. Finally, our data suggest that Rim101 activity is governed not only by proteolytic processing but also by an additional mechanism not previously described.

Inhibition of brush border sucrase by polyphenols in mouse intestine

2009 ◽  
Vol 30 (2) ◽  
pp. 111-117 ◽  
Author(s):  
Shiffalli Gupta ◽  
Safrun Mahmood ◽  
Rizwan H. Khan ◽  
Akhtar Mahmood
Keyword(s):  
Gallic Acid ◽  
Tannic Acid ◽  
Brush Border ◽  
Fluorescence Spectra ◽  
Acidic Ph ◽  
Alkaline Ph ◽  
Tryptophan Residues ◽  
Mouse Intestine ◽  
Ph Dependent ◽  
Ph Range

The interactions of gallic acid and tannic acid with purified brush border sucrase (EC 3.2.1.48) from mouse intestine have been studied. These findings indicate that both gallic acid and tannic acid inhibit sucrase activity, which is pH dependent. Kinetic analysis revealed that enzyme inhibition by gallic acid is a pure V effect at pH 5.0, which changes to mixed type at pH 7.2, and pure K effect at pH 8.5. In contrast, sucrase inhibition by tannic acid was a pure K effect at acidic pH and uncompetitive type in the alkaline pH range. Far-CD spectroscopic analysis revealed an increase in the helicity of the enzyme at acidic pH in the presence of tannic acid but no change at alkaline pH. Fluorescence spectra revealed a red shift in λmax of the enzyme, suggesting that tryptophan residues come to a more hydrophilic environment in the presence of polyphenols. These findings suggest that inhibition of mice sucrase by polyphenols is pH dependent, and is associated with conformational modifications of the enzyme.

scholarly journals Candida albicansMds3p, a Conserved Regulator of pH Responses and Virulence Identified Through Insertional Mutagenesis

Genetics ◽  
2002 ◽  
Vol 162 (4) ◽  
pp. 1573-1581 ◽  
Author(s):  
Dana A Davis ◽  
Vincent M Bruno ◽  
Lucio Loza ◽  
Scott G Filler ◽  
Aaron P Mitchell
Keyword(s):  
Drug Targets ◽  
Insertional Mutagenesis ◽  
Antibiotic Use ◽  
Alkaline Media ◽  
Alkaline Ph ◽  
Ph Response ◽  
New Genes ◽  
Ph Dependent ◽  
External Ph ◽  
Insertion Mutants

AbstractCandida albicans is a commensal fungus that causes diverse infections after antibiotic use or immune debilitation. Gene discovery has been limited because the organism is an asexual diploid. We have developed a strategy that yields random homozygous insertion mutants. The strategy has permitted identification of several prospective essential genes. Many of these genes are homologous to nonessential Saccharomyces cerevisiae genes, and some have no S. cerevisiae homolog. These findings may expand the range of antifungal drug targets. We have also identified new genes required for pH-dependent filamentation, a trait previously associated with virulence. One newly identified gene, MDS3, is required for expression in alkaline media of two filamentation-associated genes, HWP1 and ECE1, but is not required for expression of other pH-response genes. In S. cerevisiae, the two MDS3 homologs are required for growth in alkaline media, thus arguing that Mds3p function in adaptation to external pH changes is conserved. Epistasis tests show that Mds3p contributes to virulence and alkaline pH responses independently of the well-characterized Rim101p pH-response pathway.

The Reaction of Thiol Compounds with the Vitamin-K Dependent Clotting Factors

1969 ◽  
Vol 21 (03) ◽  
pp. 573-579 ◽  
Author(s):  
P Fantl
Keyword(s):  
Prothrombin Time ◽  
Vitamin K ◽  
Anaerobic Conditions ◽  
Clotting Factors ◽  
Thiol Compounds ◽  
Aerobic Conditions ◽  
One Stage ◽  
Factor Ii ◽  
Ph Dependent ◽  
The One

SummaryTreatment of human and dog oxalated plasma with 0.2 to 1.0 × 10−1 M 2.3-dithiopropanol (BAL) or dithiothreitol (DTT) at 2–4° C for 30 min results in the reduction of the vitamin-K dependent clotting factors II, VII, IX and X to the respective-SH derivatives. The reaction is pH dependent. Under aerobic conditions the delayed one stage prothrombin time can be partly reversed. Under anaerobic conditions a gradual prolongation of the one stage prothrombin time occurs without reversal.In very diluted plasma treated with the dithiols, prothrombin can be converted into thrombin if serum as source of active factors VII and X is added. In contrast SH factors VII, IX and X are inactive in the specific tests. Reoxidation to active factors II, VII, IX and X takes place during adsorption and elution of the SH derivatives. The experiments have indicated that not only factor II but also factors VII, IX and X have active-S-S-centres.

Comparative Two-Dimensional Gel Electrophoresis of Trypanosoma cruzi Mammalian-Stage Forms in an Alkaline pH Range

2015 ◽  
Vol 22 (12) ◽  
pp. 1066-1075 ◽  
Author(s):  
Adriana Magalhães ◽  
Rayner Queiroz ◽  
Izabela Bastos ◽  
Jaime Santana ◽  
Marcelo Sousa ◽  
...  
Keyword(s):  
Trypanosoma Cruzi ◽  
Gel Electrophoresis ◽  
Two Dimensional ◽  
Alkaline Ph ◽  
Two Dimensional Gel Electrophoresis ◽  
Ph Range

pH-Dependent Thermal Stability of Vibrio cholerae L-asparaginase

2019 ◽  
Vol 26 (10) ◽  
pp. 743-750 ◽  
Author(s):  
Remya Radha ◽  
Sathyanarayana N. Gummadi
Keyword(s):  
Vibrio Cholerae ◽  
Conformational Changes ◽  
Kinetic Studies ◽  
Structural Features ◽  
Structure Stability ◽  
Kcal Mole ◽  
Scanning Calorimetry ◽  
Wide Range ◽  
Ph Dependent ◽  
Ph Range

Background:pH is one of the decisive macromolecular properties of proteins that significantly affects enzyme structure, stability and reaction rate. Change in pH may protonate or deprotonate the side group of aminoacid residues in the protein, thereby resulting in changes in chemical and structural features. Hence studies on the kinetics of enzyme deactivation by pH are important for assessing the bio-functionality of industrial enzymes. L-asparaginase is one such important enzyme that has potent applications in cancer therapy and food industry.Objective:The objective of the study is to understand and analyze the influence of pH on deactivation and stability of Vibrio cholerae L-asparaginase.Methods:Kinetic studies were conducted to analyze the effect of pH on stability and deactivation of Vibrio cholerae L-asparaginase. Circular Dichroism (CD) and Differential Scanning Calorimetry (DSC) studies have been carried out to understand the pH-dependent conformational changes in the secondary structure of V. cholerae L-asparaginase.Results:The enzyme was found to be least stable at extreme acidic conditions (pH< 4.5) and exhibited a gradual increase in melting temperature from 40 to 81 °C within pH range of 4.0 to 7.0. Thermodynamic properties of protein were estimated and at pH 7.0 the protein exhibited ΔG37of 26.31 kcal mole-1, ΔH of 204.27 kcal mole-1 and ΔS of 574.06 cal mole-1 K-1.Conclusion:The stability and thermodynamic analysis revealed that V. cholerae L-asparaginase was highly stable over a wide range of pH, with the highest stability in the pH range of 5.0–7.0.

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