scholarly journals Candida albicans Hexokinase 2 Challenges the Saccharomyces cerevisiae Moonlight Protein Model

2021 ◽  
Vol 9 (4) ◽  
pp. 848
Author(s):  
Romain Laurian ◽  
Jade Ravent ◽  
Karine Dementhon ◽  
Marc Lemaire ◽  
Alexandre Soulard ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Candida Albicans ◽  
Glucose Repression ◽  
Carbon Sources ◽  
Metabolic Adaptation ◽  
Dual Function ◽  
Pathogenic Yeast ◽  
Hexokinase 2 ◽  
Regulatory Functions ◽  
The Impact

Survival of the pathogenic yeast Candida albicans depends upon assimilation of fermentable and non-fermentable carbon sources detected in host microenvironments. Among the various carbon sources encountered in a human body, glucose is the primary source of energy. Its effective detection, metabolism and prioritization via glucose repression are primordial for the metabolic adaptation of the pathogen. In C. albicans, glucose phosphorylation is mainly performed by the hexokinase 2 (CaHxk2). In addition, in the presence of glucose, CaHxK2 migrates in the nucleus and contributes to the glucose repression signaling pathway. Based on the known dual function of the Saccharomyces cerevisiae hexokinase 2 (ScHxk2), we intended to explore the impact of both enzymatic and regulatory functions of CaHxk2 on virulence, using a site-directed mutagenesis approach. We show that the conserved aspartate residue at position 210, implicated in the interaction with glucose, is essential for enzymatic and glucose repression functions but also for filamentation and virulence in macrophages. Point mutations and deletion into the N-terminal region known to specifically affect glucose repression in ScHxk2 proved to be ineffective in CaHxk2. These results clearly show that enzymatic and regulatory functions of the hexokinase 2 cannot be unlinked in C. albicans.

scholarly journals The Evolutionary Rewiring of Ubiquitination Targets Has Reprogrammed the Regulation of Carbon Assimilation in the Pathogenic Yeast Candida albicans

mBio ◽  
2012 ◽  
Vol 3 (6) ◽  
Author(s):  
Doblin Sandai ◽  
Zhikang Yin ◽  
Laura Selway ◽  
David Stead ◽  
Janet Walker ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Fatty Acids ◽  
Candida Albicans ◽  
Isocitrate Lyase ◽  
Carbon Sources ◽  
Carbon Assimilation ◽  
Pathogenic Yeast ◽  
Content Type ◽  
Catabolite Inactivation ◽  
Accelerated Degradation

ABSTRACTMicrobes must assimilate carbon to grow and colonize their niches. Transcript profiling has suggested thatCandida albicans, a major pathogen of humans, regulates its carbon assimilation in an analogous fashion to the model yeastSaccharomyces cerevisiae, repressing metabolic pathways required for the use of alterative nonpreferred carbon sources when sugars are available. However, we show that there is significant dislocation between the proteome and transcriptome inC. albicans. Glucose triggers the degradation of theICL1andPCK1transcripts inC. albicans, yet isocitrate lyase (Icl1) and phosphoenolpyruvate carboxykinase (Pck1) are stable and are retained. Indeed, numerous enzymes required for the assimilation of carboxylic and fatty acids are not degraded in response to glucose. However, when expressed inC. albicans,S. cerevisiaeIcl1 (ScIcl1) is subjected to glucose-accelerated degradation, indicating that likeS. cerevisiae, this pathogen has the molecular apparatus required to execute ubiquitin-dependent catabolite inactivation.C. albicansIcl1 (CaIcl1) lacks analogous ubiquitination sites and is stable under these conditions, but the addition of a ubiquitination site programs glucose-accelerated degradation of CaIcl1. Also, catabolite inactivation is slowed inC. albicans ubi4cells. Ubiquitination sites are present in gluconeogenic and glyoxylate cycle enzymes fromS. cerevisiaebut absent from theirC. albicanshomologues. We conclude that evolutionary rewiring of ubiquitination targets has meant that following glucose exposure,C. albicansretains key metabolic functions, allowing it to continue to assimilate alternative carbon sources. This metabolic flexibility may be critical during infection, facilitating the rapid colonization of dynamic host niches containing complex arrays of nutrients.IMPORTANCEPathogenic microbes must assimilate a range of carbon sources to grow and colonize their hosts. Current views about carbon assimilation in the pathogenic yeastCandida albicansare strongly influenced by theSaccharomyces cerevisiaeparadigm in which cells faced with choices of nutrients first use energetically favorable sugars, degrading enzymes required for the assimilation of less favorable alternative carbon sources. We show that this is not the case inC. albicansbecause there has been significant evolutionary rewiring of the molecular signals that promote enzyme degradation in response to glucose. As a result, this major pathogen of humans retains enzymes required for the utilization of physiologically relevant carbon sources such as lactic acid and fatty acids, allowing it to continue to use these host nutrients even when glucose is available. This phenomenon probably enhances efficient colonization of host niches where sugars are only transiently available.

scholarly journals A Suppressor Mutation in the β-Subunit Kis1 Restores Functionality of the SNF1 Complex in Candida albicans snf4 Δ Mutants

mSphere ◽  
2021 ◽  
Author(s):  
Bernardo Ramírez-Zavala ◽  
Austin Mottola ◽  
Ines Krüger ◽  
Joachim Morschhäuser
Keyword(s):  
Candida Albicans ◽  
Protein Kinase ◽  
Carbon Sources ◽  
Metabolic Adaptation ◽  
Β Subunit ◽  
Wild Type ◽  
Pathogenic Yeast ◽  
Α Subunit ◽  
Content Type ◽  
Repressor Proteins

The highly conserved protein kinase SNF1 plays a key role in the metabolic adaptation of the pathogenic yeast Candida albicans , but it is not clear how it regulates its downstream targets in this fungus. We show that the repressor proteins Mig1 and Mig2 are phosphorylated also in cells lacking the catalytic α-subunit Snf1 of the SNF1 complex, but the amounts of both proteins were reduced in wild-type cells when glucose was replaced by alternative carbon sources, pointing to an indirect mechanism of regulation.

scholarly journals Multicopy FZF1 (SUL1) Suppresses the Sulfite Sensitivity but Not the Glucose Derepression or Aberrant Cell Morphology of a grr1 Mutant of Saccharomyces cerevisiae

Genetics ◽  
1996 ◽  
Vol 144 (2) ◽  
pp. 511-521 ◽  
Author(s):  
Dorina Avram ◽  
Alan T Bakalinsky
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Transcription Factor ◽  
Glucose Metabolism ◽  
Cell Morphology ◽  
Glucose Repression ◽  
Carbon Sources ◽  
Single Copy ◽  
Aberrant Cell ◽  
Growth Defects ◽  
Putative Transcription Factor

Abstract An ssu2 mutation in Sacccharomyces cermisiae, previously shown to cause sulfite sensitivity, was found to be allelic to GRR1, a gene previously implicated in glucose repression. The suppressor rgt1, which suppresses the growth defects of grr1 strains on glucose, did not fully suppress the sensitivity on glucose or nonglucose carbon sources, indicating that it is not strictly linked to a defect in glucose metabolism. Because the Cln1 protein was previously shown to be elevated in grr1 mutants, the effect of CLN1 overexpression on sulfite sensitivity was investigated. Overexpression in GRR1 cells resulted in sulfite sensitivity, suggesting a connection between CLN1 and sulfite metabolism. Multicopy FZF1, a putative transcription factor, was found to suppress the sulfite sensitive phenotype of grr1 strains, but not the glucose derepression or aberrant cell morphology. Multicopy FZF1 was also found to suppress the sensitivity of a number of other unrelated sulfite-sensitive mutants, but not that of ssu1 or met20, implying that FZF1 may act through Ssulp and Met20p. Disruption of FZF1 resulted in sulfite sensitivity when the construct was introduced in single copy at the FZF1 locus in a GRR1 strain, providing evidence that FZF1 is involved in sulfite metabolism.

Cloning and genetic mapping of SNF1, a gene required for expression of glucose-repressible genes in Saccharomyces cerevisiae

1984 ◽  
Vol 4 (1) ◽  
pp. 49-53
Author(s):  
J L Celenza ◽  
M Carlson
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Genetic Mapping ◽  
Gene Product ◽  
Structural Gene ◽  
Glucose Repression ◽  
Carbon Sources ◽  
Recombinant Plasmids ◽  
The Right ◽  
Integrating Vector

A functional SNF1 gene product is required to derepress expression of many glucose-repressible genes in Saccharomyces cerevisiae. Strains carrying a snf1 mutation are unable to grow on sucrose, galactose, maltose, melibiose, or nonfermentable carbon sources; utilization of these carbon sources is regulated by glucose repression. The inability of snf1 mutants to utilize sucrose results from failure to derepress expression of the structural gene for invertase at the RNA level. We isolated recombinant plasmids carrying the SNF1 gene by complementation of the snf1 defect in S. cerevisiae. A 3.5-kilobase region is common to the DNA segments cloned in five different plasmids. Transformation of S. cerevisiae with an integrating vector carrying a segment of the cloned DNA resulted in integration of the plasmid at the SNF1 locus. This result indicates that the cloned DNA is homologous to sequences at the SNF1 locus. By mapping a plasmid marker linked to SNF1 in this transformant, we showed that the SNF1 gene is located on chromosome IV. We then mapped snf1 to a position 5.6 centimorgans distal to rna3 on the right arm; snf1 is not extremely closely linked to any previously mapped mutation.

scholarly journals Hexokinase and glucokinases are essential for fitness and virulence in the pathogenic yeastCandida albicans

2018 ◽  
Author(s):  
Romain Laurian ◽  
Karine Dementhon ◽  
Bastien Doumèche ◽  
Alexandre Soulard ◽  
Thierry Noel ◽  
...  
Keyword(s):  
Stress Responses ◽  
Galleria Mellonella ◽  
Glucose Repression ◽  
Metabolic Adaptation ◽  
Metabolic Flexibility ◽  
Pathogenic Yeast ◽  
Regulatory Pathways ◽  
Metabolic Role ◽  
Wide Range ◽  
Hexose Phosphorylation

AbstractMetabolic flexibility promotes infection and commensal colonization by the opportunistic pathogenCandida albicans.Yeast cell survival depends upon assimilation of fermentable and non-fermentable locally available carbon sources. Physiologically relevant sugars like glucose and fructose are present at low level in host niches. However, because glucose is the preferred substrate for energy and biosynthesis of structural components, its efficient metabolization is fundamental for the metabolic adaptation of the pathogen. We explored and characterized theC. albicanshexose kinase system composed of one hexokinase (CaHxk2) and two glucokinases (CaGlk1 and CaGlk4). Using a set of mutant strains, we found that hexose phosphorylation is mostly assured by CaHxk2, which sustains growth on hexoses. Our data on hexokinase and glucokinase expression point out an absence of cross regulation mechanisms at the transcription level and different regulatory pathways. In the presence of glucose, CaHxk2 migrates in the nucleus and contributes to the glucose repression signaling pathway. In addition, CaHxk2 participates to oxidative, osmotic and cell wall stress responses, while glucokinases are overexpressed under hypoxia. Hexose phosphorylation is a key step necessary for filamentation, that is affected in the hexokinase mutant. Virulence of this mutant is clearly impacted in theGalleria mellonellaand macrophage models. Filamentation, glucose phosphorylation and stress response defects of the hexokinase mutant prevent host killing byC. albicans.By contributing to metabolic flexibility, stress answer response and morphogenesis, hexose kinase enzymes play an essential role in the virulence ofC. albicans.Author summaryThe pathogenic yeastC. albicansis both a powerful commensal and pathogen of humans that can infect wide range of organs and body sites. To grow in its host and establish an infection, the pathogen must assimilate carbon from these heterogenous environments.C. albicansregulates central carbon metabolism in a niche-specific manner, activating alternatively gluconeogenesis, glyoxylate cycle and the glycolytic metabolism. For yeast and other microorganisms, glucose is the preferred carbon and energy source and its accurate detection and metabolism is essential. However, the glycolytic hexose kinase system has not been investigated yet inC. albicans.In this report, we showed that hexokinase and glucokinases contribute to the fitness and virulence ofC. albicans.We revealed the main metabolic role of the hexokinase CaHxk2 which impacts on growth, glucose signalling, morphological transition and virulence. However, glucokinases contribute to the anoxic response and their implication in regulation processes is suggested.

scholarly journals Metabolic Reprogramming in the Opportunistic Yeast Candida albicans in Response to Hypoxia

mSphere ◽  
2020 ◽  
Vol 5 (1) ◽  
Author(s):  
Anaïs Burgain ◽  
Faiza Tebbji ◽  
Inès Khemiri ◽  
Adnane Sellam
Keyword(s):  
Cell Wall ◽  
Candida Albicans ◽  
Metabolic Pathways ◽  
Membrane Lipids ◽  
Oxygen Depletion ◽  
Metabolic Reprogramming ◽  
Pathogenic Yeast ◽  
Fungal Virulence ◽  
Content Type ◽  
The Impact

ABSTRACT Hypoxia is the predominant condition that the human opportunistic fungus Candida albicans encounters in the majority of the colonized niches within the host. So far, the impact of such a condition on the overall metabolism of this important human-pathogenic yeast has not been investigated. Here, we have undertaken a time-resolved metabolomics analysis to uncover the metabolic landscape of fungal cells experiencing hypoxia. Our data showed a dynamic reprogramming of many fundamental metabolic pathways, such as glycolysis, the pentose phosphate pathway, and different metabolic routes related to fungal cell wall biogenesis. The C. albicans lipidome was highly affected by oxygen depletion, with an increased level of free fatty acids and biochemical intermediates of membrane lipids, including phospholipids, lysophospholipids, sphingolipids, and mevalonate. The depletion of oxygen-dependent lipids such as ergosterol or phosphatidylcholine with longer and polyunsaturated lateral fatty acid chains was observed only at the later hypoxic time point (180 min). Transcriptomics data supported the main metabolic response to hypoxia when matched to our metabolomic profiles. The hypoxic metabolome reflected different physiological alterations of the cell wall and plasma membrane of C. albicans under an oxygen-limiting environment that were confirmed by different approaches. This study provided a framework for future in vivo investigations to examine relevant hypoxic metabolic trajectories in fungal virulence and fitness within the host. IMPORTANCE A critical aspect of cell fitness is the ability to sense and adapt to variations in oxygen levels in their local environment. Candida albicans is an opportunistic yeast that is the most prevalent human fungal pathogen. While hypoxia is the predominant condition that C. albicans encounters in most of its niches, its impact on fungal metabolism remains unexplored so far. Here, we provided a detailed landscape of the C. albicans metabolome that emphasized the importance of many metabolic routes for the adaptation of this yeast to oxygen depletion. The fungal hypoxic metabolome identified in this work provides a framework for future investigations to assess the contribution of relevant metabolic pathways in the fitness of C. albicans and other human eukaryotic pathogens with similar colonized human niches. As hypoxia is present at most of the fungal infection foci in the host, hypoxic metabolic pathways are thus an attractive target for antifungal therapy.

scholarly journals Rgt1, a glucose sensing transcription factor, is required for transcriptional repression of the HXK2 gene in Saccharomyces cerevisiae

2005 ◽  
Vol 388 (2) ◽  
pp. 697-703 ◽  
Author(s):  
Aaron PALOMINO ◽  
Pilar HERRERO ◽  
Fernando MORENO
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Transcription Factor ◽  
Transcriptional Repression ◽  
Glucose Repression ◽  
Fold Increase ◽  
Glucose Sensing ◽  
Start Codon ◽  
Dependent Manner ◽  
Gene Encoding ◽  
Regulatory Functions

Expression of HXK2, a gene encoding a Saccharomyces cerevisiae bifunctional protein with catalytic and regulatory functions, is controlled by glucose availability, being activated in the presence of glucose and inhibited when the levels of the sugar are low. In the present study, we identified Rgt1 as a transcription factor that, together with the Med8 protein, is essential for repression of the HXK2 gene in the absence of glucose. Rgt1 represses HXK2 expression by binding specifically to the motif (CGGAAAA) located at −395 bp relative to the ATG translation start codon in the HXK2 promoter. Disruption of the RGT1 gene causes an 18-fold increase in the level of HXK2 transcript in the absence of glucose. Rgt1 binds to the RGT1 element of HXK2 promoter in a glucose-dependent manner, and the repression of target gene depends on binding of Rgt1 to DNA. The physiological significance of the connection between two glucose-signalling pathways, the Snf3/Rgt2 that causes glucose induction and the Mig1/Hxk2 that causes glucose repression, was also analysed.

scholarly journals Duplicate upstream activating sequences in the promoter region of the Saccharomyces cerevisiae GAL7 gene.

1986 ◽  
Vol 6 (1) ◽  
pp. 246-256 ◽  
Author(s):  
M Tajima ◽  
Y Nogi ◽  
T Fukasawa
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Glucose Repression ◽  
Rotational Symmetry ◽  
Consensus Sequence ◽  
Carbon Sources ◽  
Constitutive Expression ◽  
Tata Box ◽  
Base Pairs ◽  
Multicopy Vector ◽  
In Cis

We constructed a series of deletions in the 5' noncoding region of the Saccharomyces cerevisiae GAL7 gene, fused them to the Escherichia coli gene lacZ, and introduced them into yeasts by using a multicopy vector. We then studied the effect of the deletions on beta-galactosidase synthesis directed by the gene fusions in media with various carbon sources. This analysis identified a TATA box and two upstream activating sequences as necessary elements for galactose-controlled GAL7 transcription. Two upstream activating sequences exhibiting 71% homology with each other were located 255 and 168 base pairs, respectively, upstream of the GAL7 transcription start point. Each sequence consists of 21 base pairs, displaying an approximate rotational symmetry with a core consensus sequence of GAA--AGCTGCTTC--CGCG. At least one of the two sequences is required for galactose induction and also for glucose repression of the GAL7'-lac'Z gene. Analysis with host regulatory mutants delta gal14 and delta gal180 suggests that these sequences are the site at which the GAL4 product exerts its action to activate the GAL7 gene. We also observed that a deletion lacking both upstream activation sequences allowed the gene fusion to be expressed in the absence of galactose at about 10% of the fully induced level of the intact fusion. This constitutive expression depended on the presence of the TATA box of GAL7 in cis but not on a functional GAL4 gene. The level of the uncontrolled expression was decreased by increasing the distance between the TATA box and the pBR322 sequence in the vector plasmid.

scholarly journals Saccharomyces cerevisiae as a model to study synthetic cannabinoids: the impact of using different carbon sources

2021 ◽  
Vol 53 (sup1) ◽  
pp. S80-S81
Author(s):  
Daniela Guerreiro ◽  
Carla Ferreira ◽  
Madalena Salema-Oom ◽  
Alexandre Quintas
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Synthetic Cannabinoids ◽  
Carbon Sources ◽  
The Impact
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