Novel alleles of yeast hexokinase PII with distinct effects on catalytic activity and catabolite repression of SUC2

Hohmann, Stefan; Winderickx, Joris; Winde, Johannes H. de; Valckx, Dirk; Cobbaert, P; Luyten, Kattie; Meirsman, Catherine De; Ramos, José; Thevelein, Johan M.

doi:10.1099/13500872-145-3-703

Cited by 71 publications

(65 citation statements)

References 36 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In the wild-type and in the mutant strains, induced Lip1 expression remained suppressed by glucose and fructose. These results do not indicate that catabolite suppression in B. cinerea occurs via hexose kinases, as has been described for yeast (Entian, 1980;Hohmann et al, 1999). In A. nidulans, evidence for a common role of hexokinase and glucokinase in catabolite repression was obtained (Flipphi et al, 2003).…”

Section: Role Of Hexose Kinases In Botrytis Cinereamentioning

confidence: 54%

The Botrytis cinerea hexokinase, Hxk1, but not the glucokinase, Glk1, is required for normal growth and sugar metabolism, and for pathogenicity on fruits

Rui

Hahn

2007

Microbiology

View full text Add to dashboard Cite

Hexose kinases play a central role in the initiation of sugar metabolism of living organisms and have also been implicated in carbon catabolite repression in yeasts and plants. In this study, the genes encoding glucokinase (Glk1) and hexokinase (Hxk1) from the plant-pathogenic ascomycete Botrytis cinerea were isolated and functionally characterized. Glk1-deficient mutants were indistinguishable from the wild-type in all growth parameters tested. In contrast, Dhxk1 mutants lacking Hxk1 showed a pleiotropic growth defect. On artificial media, vegetative growth was retarded, and conidia formation strongly reduced. No or only marginal growth of Dhxk1 mutants was observed when fructose, galactose, sucrose or sorbitol were used as carbon sources, and fructose inhibited growth of the mutant in the presence of other carbon sources. B. cinerea mutants containing hxk1 alleles with point mutations leading to enzymically inactive enzymes showed phenotypes similar to the Dhxk1 disruption mutant, indicating that loss of hexose phosphorylation activity of Hxk1 is solely responsible for the pleiotropic growth defect. Virulence of the Dhxk1 mutants was dependent on the plant tissue: on leaves, lesion formation was only slightly retarded compared to the wild-type, whereas only small lesions were formed on apples, strawberries and tomatoes. The low virulence of Dhxk1 mutants on fruits was correlated with their high contents of sugars, in particular fructose. Heterologous expression of Hxk1 and Glk1 in yeast allowed their enzymic characterization, revealing kinetic properties similar to other fungal hexokinases and glucokinases. Both Dglk1 and Dhxk1 mutants showed normal glucose repression of secreted lipase 1 activity, indicating that, in contrast to yeast, B. cinerea hexose kinases are not involved in carbon catabolite repression. INTRODUCTIONHexose kinases are crucial enzymes for most living cells, by catalysing the intracellular trapping and feeding into metabolism of the hexoses glucose and fructose after their uptake. In addition, hexokinases have been shown in yeast, plants and mammals to participate in glucose signalling (De Winde et al., 1996;Moore et al., 2003;Efrat et al., 1994). Saccharomyces cerevisiae has three enzymes catalysing hexose phosphorylation, namely hexokinases (EC 2 . 7 . 1 . 1) Hxk1 and Hxk2, and glucokinase (EC 2 . 7 . 1 . 2) Glk1. Each of these enzymes can support growth on glucose, while either of the two hexokinases is required for growth on fructose (Lobo & Maitra, 1977;Gancedo et al., 1977). Hxk2, in addition, is mainly required for catabolite repression, which prevents the expression of genes involved in catabolism of less preferred carbon sources in the presence of a more favourable nutrient such as glucose (Entian, 1980). In the presence of glucose, Hxk2 interacts with the carbon catabolite repressor Mig1 and thereby is translocated into the nucleus. In the nucleus, the Hxk2-Mig1 complex seems to form a repressor complex that binds to the promoters of carbon-catabolite-repressible genes (Ahuatzi ...

show abstract

Section: Role Of Hexose Kinases In Botrytis Cinereamentioning

confidence: 54%

The Botrytis cinerea hexokinase, Hxk1, but not the glucokinase, Glk1, is required for normal growth and sugar metabolism, and for pathogenicity on fruits

Rui

Hahn

2007

Microbiology

View full text Add to dashboard Cite

show abstract

“…(i) When the GLK1 gene is overexpressed in an hxk1 hxk2 double null mutant the transformed strains are still insensitive to glucose repression although a 3-fold increase of phosphorylating activity is achieved (6). (ii) Glucose repression is not linearly relieved with decreasing kinase activity, indicating that sugar kinase activity and sugar signaling are mediated at least in part through separated domains of Hxk2 (30,31). (iii) Mutant alleles with low catalytic activity were still fully functional in glucose signaling (32).…”

Section: Discussionmentioning

confidence: 99%

The Glucose-regulated Nuclear Localization of Hexokinase 2 in Saccharomyces cerevisiae Is Mig1-dependent

Ahuatzi¹,

Herrero²,

la³

et al. 2004

Journal of Biological Chemistry

116

186

View full text Add to dashboard Cite

Two major mediators of glucose repression in Saccharomyces cerevisiae are the proteins Mig1 and Hxk2. The mechanism of Hxk2-dependent glucose repression pathway is not well understood, but the Mig1-dependent part of the pathway has been elucidated in great detail. Here we report that Hxk2 has a glucose-regulated nuclear localization and that Mig1, a transcriptional repressor responsible for glucose repression of many genes, is required to sequester Hxk2 into the nucleus. Mig1 and Hxk2 interacted in vivo in a yeast two-hybrid assay and in vitro in immunoprecipitation and glutathione S-transferase pull-down experiments. We found that the Lys 6 -Met 15 decapeptide of Hxk2, which is necessary for nuclear localization of the protein, is also essential for interaction with the Mig1 protein. Our results also show that the Hxk2-Mig1 interaction is of physiological significance because both proteins have been found interacting together in a cluster with DNA fragments containing the MIG1 site of SUC2 promoter. We conclude that Hxk2 operates by interacting with Mig1 to generate a repressor complex located in the nucleus of S. cerevisiae during growth in glucose medium.The yeast Saccharomyces cerevisiae can use different carbon sources for growth, but evolution has selected mechanisms for the preferential and efficient utilization of glucose. In this yeast, glucose regulates carbon utilization mainly by the repression or activation of the transcription of numerous genes that encode enzymes implicated in carbon metabolism (1, 2). Although several of the genes implicated in the pathways that control glucose repression have been identified, a complete mechanistic picture of the process is not yet available. The Hxk2 and Mig1 proteins participate as important repressors in the glucose signaling pathway (3, 4).Hxk2 is the protein that initiates the intracellular metabolism of glucose by its phosphorylation at C-6, but in addition it plays a vital role in glucose repression (5). In hxk2 mutants repression of several genes by glucose is no longer operative (6, 7). If Hxk2 acts as a transcriptional repressor, it should be found in the cell nucleus at least under certain conditions. In fact, results obtained using different approaches have demonstrated that about 15% of the protein is localized in the nucleus (8,9) and that this localization is required for glucose repression of SUC2, HXK1, and GLK1 genes (9, 10). Moreover it has been shown that the nuclear Hxk2 is involved in the formation of specific DNA-protein complexes during glucose-dependent repression of these genes (9, 10).Mig1 is a C 2 H 2 zinc finger protein that binds to the motif WWWWWN(G/C)(C/T)GGGG in several promoters (11). Once bound to this MIG1 element, it recruits the Tup1-Cyc8 (Ssn6p) complex that represses gene transcription during growth in glucose (12). The activity of Mig1 is regulated by phosphorylation and subcellular localization. In high glucose, Mig1 is dephosphorylated by the Glc7-Reg1 protein phosphatase complex (13) and is located in the nucleus wher...

show abstract

“…Snf1p kinases seem to monitor the energy status of the cell; they are activated by AMP, which is high when the energy level of the cell is low (649). However, in S. cerevisiae the signal that controls Snf1p is not clearly defined; the long-known fact that the hexokinases affect catabolite repression keeps the discussion open if they somehow control Snf1p directly (84,185,233).…”

Section: Nutrient-controlled Signaling and Stress Responsesmentioning

confidence: 99%

“…This makes it necessary to use a tps1⌬ hxk2⌬ double mutant, in which the gene for the main hexokinase has been deleted. The double mutant can grow on glucose but, due to the lack of Hxk2p, displays other pleiotropic effects, for instance, in glucose repression (231,233). The use of a tps2⌬ mutant to block trehalose biosynthesis is also problematic, since this mutation has pleiotropic effects due to trehalose-6-phosphate accumulation (597).…”

Section: Metabolism Of Trehalose and Glycogenmentioning

confidence: 99%

Osmotic Stress Signaling and Osmoadaptation in Yeasts

Hohmann

2002

Microbiol Mol Biol Rev

Self Cite

1,526

1,440

View full text Add to dashboard Cite

The ability to adapt to altered availability of free water is a fundamental property of living cells. The principles underlying osmoadaptation are well conserved. The yeast Saccharomyces cerevisiae is an excellent model system with which to study the molecular biology and physiology of osmoadaptation. Upon a shift to high osmolarity, yeast cells rapidly stimulate a mitogen-activated protein (MAP) kinase cascade, the high-osmolarity glycerol (HOG) pathway, which orchestrates part of the transcriptional response. The dynamic operation of the HOG pathway has been well studied, and similar osmosensing pathways exist in other eukaryotes. Protein kinase A, which seems to mediate a response to diverse stress conditions, is also involved in the transcriptional response program. Expression changes after a shift to high osmolarity aim at adjusting metabolism and the production of cellular protectants. Accumulation of the osmolyte glycerol, which is also controlled by altering transmembrane glycerol transport, is of central importance. Upon a shift from high to low osmolarity, yeast cells stimulate a different MAP kinase cascade, the cell integrity pathway. The transcriptional program upon hypo-osmotic shock seems to aim at adjusting cell surface properties. Rapid export of glycerol is an important event in adaptation to low osmolarity. Osmoadaptation, adjustment of cell surface properties, and the control of cell morphogenesis, growth, and proliferation are highly coordinated processes. The Skn7p response regulator may be involved in coordinating these events. An integrated understanding of osmoadaptation requires not only knowledge of the function of many uncharacterized genes but also further insight into the time line of events, their interdependence, their dynamics, and their spatial organization as well as the importance of subtle effects

show abstract

Novel alleles of yeast hexokinase PII with distinct effects on catalytic activity and catabolite repression of SUC2

Cited by 71 publications

References 36 publications

The Botrytis cinerea hexokinase, Hxk1, but not the glucokinase, Glk1, is required for normal growth and sugar metabolism, and for pathogenicity on fruits

The Botrytis cinerea hexokinase, Hxk1, but not the glucokinase, Glk1, is required for normal growth and sugar metabolism, and for pathogenicity on fruits

The Glucose-regulated Nuclear Localization of Hexokinase 2 in Saccharomyces cerevisiae Is Mig1-dependent

Osmotic Stress Signaling and Osmoadaptation in Yeasts

Contact Info

Product

Resources

About