scholarly journals Characterization of KlGRR1 and SMS1 Genes, Two New Elements of the Glucose Signaling Pathway of Kluyveromyces lactis

2008 ◽  
Vol 7 (8) ◽  
pp. 1299-1308 ◽  
Author(s):  
Martina Hnatova ◽  
Micheline Wésolowski-Louvel ◽  
Guenaëlle Dieppois ◽  
Julien Deffaud ◽  
Marc Lemaire
Keyword(s):  
Signaling Pathway ◽  
Glucose Transporter ◽  
Glucose Sensor ◽  
Kluyveromyces Lactis ◽  
Single Gene ◽  
Negative Regulator ◽  
Casein Kinase I ◽  
Glucose Signaling ◽  
F Box Protein

ABSTRACT The expression of the major glucose transporter gene, RAG1, is induced by glucose in Kluyveromyces lactis. This regulation involves several pathways, including one that is similar to Snf3/Rgt2-ScRgt1 in Saccharomyces cerevisiae. We have identified missing key components of the K. lactis glucose signaling pathway by comparison to the same pathway of S. cerevisiae. We characterized a new mutation, rag19, which impairs RAG1 regulation. The Rag19 protein is 43% identical to the F-box protein ScGrr1 of S. cerevisiae and is able to complement an Scgrr1 mutation. In the K. lactis genome, we identified a single gene, SMS1 (for similar to Mth1 and Std1), that encodes a protein showing an average of 50% identity with Mth1 and Std1, regulators of the ScRgt1 repressor. The suppression of the rag4 (glucose sensor), rag8 (casein kinase I), and rag19 mutations by the Δsms1 deletion, together with the restoration of RAG1 transcription in the double mutants, demonstrates that Sms1 is a negative regulator of RAG1 expression and is acting downstream of Rag4, Rag8, and Rag19 in the cascade. We report that Sms1 regulates KlRgt1 repressor activity by preventing its phosphorylation in the absence of glucose, and that SMS1 is regulated by glucose, both at the transcriptional and the posttranslational level. Two-hybrid interactions of Sms1 with the glucose sensor and KlRgt1 repressor suggest that Sms1 mediates the glucose signal from the plasma membrane to the nucleus. All of these data demonstrated that Sms1 was the K. lactis homolog of MTH1 and STD1 of S. cerevisiae. Interestingly, MTH1 and STD1 were unable to complement a Δsms1 mutation.

scholarly journals Glycolysis Controls Plasma Membrane Glucose Sensors To Promote Glucose Signaling in Yeasts

2014 ◽  
Vol 35 (4) ◽  
pp. 747-757 ◽  
Author(s):  
Amélie Cairey-Remonnay ◽  
Julien Deffaud ◽  
Micheline Wésolowski-Louvel ◽  
Marc Lemaire ◽  
Alexandre Soulard
Keyword(s):  
Signaling Pathway ◽  
Glucose Sensor ◽  
Kluyveromyces Lactis ◽  
Glucose Sensors ◽  
Content Type ◽  
Glucose Signaling ◽  
Extracellular Glucose ◽  
Glucose Accumulation ◽  
The Stability ◽  
Intracellular Glucose

Sensing of extracellular glucose is necessary for cells to adapt to glucose variation in their environment. In the respiratory yeastKluyveromyces lactis, extracellular glucose controls the expression of major glucose permease geneRAG1through a cascade similar to theSaccharomyces cerevisiaeSnf3/Rgt2/Rgt1 glucose signaling pathway. This regulation depends also on intracellular glucose metabolism since we previously showed that glucose induction of theRAG1gene is abolished in glycolytic mutants. Here we show that glycolysis regulatesRAG1expression through theK. lactisRgt1 (KlRgt1) glucose signaling pathway by targeting the localization and probably the stability of Rag4, the single Snf3/Rgt2-type glucose sensor ofK. lactis. Additionally, the control exerted by glycolysis on glucose signaling seems to be conserved inS. cerevisiae. This retrocontrol might prevent yeasts from unnecessary glucose transport and intracellular glucose accumulation.

scholarly journals Rgt1p of Saccharomyces cerevisiae, a key regulator of glucose-induced genes, is both an activator and a repressor of transcription.

1996 ◽  
Vol 16 (11) ◽  
pp. 6419-6426 ◽  
Author(s):  
S Ozcan ◽  
T Leong ◽  
M Johnston
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Glucose Transporter ◽  
Glucose Sensor ◽  
Glucose Sensors ◽  
Hexose Transporter ◽  
Glucose Signaling ◽  
Low Glucose ◽  
Induced Genes ◽  
Low Levels ◽  
High Concentrations

The RGT1 gene of Saccharomyces cerevisiae plays a central role in the glucose-induced expression of hexose transporter (HXT) genes. Genetic evidence suggests that it encodes a repressor of the HXT genes whose function is inhibited by glucose. Here, we report the isolation of RGT1 and demonstrate that it encodes a bifunctional transcription factor. Rgt1p displays three different transcriptional modes in response to glucose: (i) in the absence of glucose, it functions as a transcriptional repressor; (ii) high concentrations of glucose cause it to function as a transcriptional activator; and (iii) in cells growing on low levels of glucose, Rgt1p has a neutral role, neither repressing nor activating transcription. Glucose alters Rgt1p function through a pathway that includes two glucose sensors, Snf3p and Rgt2p, and Grr1p. The glucose transporter Snf3p, which appears to be a low-glucose sensor, is required for inhibition of Rgt1p repressor function by low levels of glucose. Rgt2p, a glucose transporter that functions as a high-glucose sensor, is required for conversion of Rgt1p into an activator by high levels of glucose. Grr1p, a component of the glucose signaling pathway, is required both for inactivation of Rgt1p repressor function by low levels of glucose and for conversion of Rgt1p into an activator at high levels of glucose. Thus, signals generated by two different glucose sensors act through Grr1p to determine Rgt1p function.

The hexokinase gene is required for transcriptional regulation of the glucose transporter gene RAG1 in Kluyveromyces lactis

1993 ◽  
Vol 13 (7) ◽  
pp. 3882-3889
Author(s):  
C Prior ◽  
P Mamessier ◽  
H Fukuhara ◽  
X J Chen ◽  
M Wesolowski-Louvel
Keyword(s):  
Glucose Transporter ◽  
Kinase Activity ◽  
Glucose Repression ◽  
Kluyveromyces Lactis ◽  
Transport Systems ◽  
Transporter Gene ◽  
Rag1 Gene ◽  
Sugar Kinase

The RAG1 gene of Kluyveromyces lactis encodes a low-affinity glucose/fructose transporter. Its transcription is induced by glucose, fructose, and several other sugars. The RAG4, RAG5, and RAG8 genes are trans-acting genes controlling the expression of the RAG1 gene. We report here the characterization of one of these genes, RAG5. The nucleotide sequence of the cloned RAG5 gene indicated that it encodes a protein that is homologous to hexokinases of Saccharomyces cerevisiae. rag5 mutants showed no detectable hexokinase or glucokinase activity, suggesting that the sugar kinase activity encoded by this gene is the only hexokinase in K. lactis. Both high- and low-affinity transport systems of glucose were affected in rag5 mutants. The defect of the low-affinity component was found to be due to a block of transcription of the RAG1 gene by the hexokinase mutation. In vivo complementation of the rag5 mutation by the HXK2 gene of S. cerevisiae and complementation of hxk1 hxk2 mutations of S. cerevisiae by the RAG5 gene showed that RAG5 and HXK2 were equivalent for sugar-phosphorylating activity but that RAG5 could not restore glucose repression in the S. cerevisiae hexokinase mutants.

scholarly journals The hexokinase gene is required for transcriptional regulation of the glucose transporter gene RAG1 in Kluyveromyces lactis.

1993 ◽  
Vol 13 (7) ◽  
pp. 3882-3889 ◽  
Author(s):  
C Prior ◽  
P Mamessier ◽  
H Fukuhara ◽  
X J Chen ◽  
M Wesolowski-Louvel
Keyword(s):  
Glucose Transporter ◽  
Kinase Activity ◽  
Glucose Repression ◽  
Kluyveromyces Lactis ◽  
Transport Systems ◽  
Transporter Gene ◽  
Rag1 Gene ◽  
Sugar Kinase

The RAG1 gene of Kluyveromyces lactis encodes a low-affinity glucose/fructose transporter. Its transcription is induced by glucose, fructose, and several other sugars. The RAG4, RAG5, and RAG8 genes are trans-acting genes controlling the expression of the RAG1 gene. We report here the characterization of one of these genes, RAG5. The nucleotide sequence of the cloned RAG5 gene indicated that it encodes a protein that is homologous to hexokinases of Saccharomyces cerevisiae. rag5 mutants showed no detectable hexokinase or glucokinase activity, suggesting that the sugar kinase activity encoded by this gene is the only hexokinase in K. lactis. Both high- and low-affinity transport systems of glucose were affected in rag5 mutants. The defect of the low-affinity component was found to be due to a block of transcription of the RAG1 gene by the hexokinase mutation. In vivo complementation of the rag5 mutation by the HXK2 gene of S. cerevisiae and complementation of hxk1 hxk2 mutations of S. cerevisiae by the RAG5 gene showed that RAG5 and HXK2 were equivalent for sugar-phosphorylating activity but that RAG5 could not restore glucose repression in the S. cerevisiae hexokinase mutants.

scholarly journals Evidence that human oral glucose detection involves a sweet taste pathway and a glucose transporter pathway

PLoS ONE ◽  
2021 ◽  
Vol 16 (10) ◽  
pp. e0256989
Author(s):  
Paul A. S. Breslin ◽  
Akiko Izumi ◽  
Anilet Tharp ◽  
Tadahiro Ohkuri ◽  
Yoshiaki Yokoo ◽  
...  
Keyword(s):  
Signaling Pathway ◽  
Glucose Transporter ◽  
Taste Receptor ◽  
Sweet Taste ◽  
Oral Glucose ◽  
Glucose Detection ◽  
Detection Thresholds ◽  
Glucose Signaling ◽  
Sweet Taste Receptor ◽  
Class 1

The taste stimulus glucose comprises approximately half of the commercial sugar sweeteners used today, whether in the form of the di-saccharide sucrose (glucose-fructose) or half of high-fructose corn syrup (HFCS). Therefore, oral glucose has been presumed to contribute to the sweet taste of foods when combined with fructose. In light of recent rodent data on the role of oral metabolic glucose signaling, we examined psychopharmacologically whether oral glucose detection may also involve an additional pathway in humans to the traditional sweet taste transduction via the class 1 taste receptors T1R2/T1R3. In a series of experiments, we first compared oral glucose detection thresholds to sucralose thresholds without and with addition of the T1R receptor inhibitor Na-lactisole. Next, we compared oral detection thresholds of glucose to sucralose and to the non-metabolizable glucose analog, α-methyl-D-glucopyranoside (MDG) without and with the addition of the glucose co-transport component sodium (NaCl). Finally, we compared oral detection thresholds for glucose, MDG, fructose, and sucralose without and with the sodium-glucose co-transporter (SGLT) inhibitor phlorizin. In each experiment, psychopharmacological data were consistent with glucose engaging an additional signaling pathway to the sweet taste receptor T1R2/T1R3 pathway. Na-lactisole addition impaired detection of the non-caloric sweetener sucralose much more than it did glucose, consistent with glucose using an additional signaling pathway. The addition of NaCl had a beneficial impact on the detection of glucose and its analog MDG and impaired sucralose detection, consistent with glucose utilizing a sodium-glucose co-transporter. The addition of the SGLT inhibitor phlorizin impaired detection of glucose and MDG more than it did sucralose, and had no effect on fructose, further evidence consistent with glucose utilizing a sodium-glucose co-transporter. Together, these results support the idea that oral detection of glucose engages two signaling pathways: one that is comprised of the T1R2/T1R3 sweet taste receptor and the other that utilizes an SGLT glucose transporter.

Functional characterization of mouse sodium/glucose transporter type 3b

2010 ◽  
Vol 299 (1) ◽  
pp. C58-C65 ◽  
Author(s):  
Oscar Aljure ◽  
Ana Díez-Sampedro
Keyword(s):  
Steady State ◽  
Human Genome ◽  
Conformational Changes ◽  
Glucose Transporter ◽  
Glucose Sensor ◽  
Functional Characterization ◽  
Sugar Transport ◽  
Tightly Coupled ◽  
Type 3

Despite belonging to a family of sugar cotransporters, human sodium/glucose transporter type 3 (hSGLT3) does not transport sugar, but it depolarizes the cell in the presence of extracellular sugar, and thus it has been suggested to work as a sugar sensor. In the human genome there is one SGLT3 gene, yet in mouse there are two. In this study we cloned one of them, mouse SGLT3b (mSGLT3b) and characterized the protein. We found that mSGLT3b has low affinity for sugars, as does hSGLT3, but surprisingly, mSGLT3b transports sugar, although the sugar transport is not as tightly coupled to cations as in SGLT1. Moreover, the sugar specificity of mSGLT3b has characteristics reminiscent of both SGLT1 and hSGLT3: mSGLT3b does not respond to galactose, similar to hSGLT3, but neither does it respond to 1-deoxynojirimycin, unlike hSGLT3 but similar to SGLT1. mSGLT3b has low apparent affinities for sugar and Na+ and, furthermore, displays pre-steady-state currents, which in SGLT1 report on conformational changes in the protein. Finally, phlorizin, the typical inhibitor of SGLT proteins, also inhibits mSGLT3b. In summary, although mSGLT3b has some characteristics that resemble SGLT1 and others that are similar to hSGLT3, its low sugar affinity and uncoupled sugar transport lead us to conclude that mSGLT3b likely functions as a physiological glucose sensor similar to hSGLT3.

scholarly journals RAG4 Gene Encodes a Glucose Sensor in Kluyveromyces lactis

Genetics ◽  
2001 ◽  
Vol 158 (2) ◽  
pp. 541-548
Author(s):  
Svätopluk Betina ◽  
Paola Goffrini ◽  
Iliana Ferrero ◽  
Micheline Wésolowski-Louvel
Keyword(s):  
Glucose Transporter ◽  
Glucose Sensor ◽  
Glucose Repression ◽  
Kluyveromyces Lactis ◽  
Glucose Sensing ◽  
Dual Function ◽  
Wild Type ◽  
Transporter Family ◽  
Low Concentrations ◽  
High Concentrations

Abstract The rag4 mutant of Kluyveromyces lactis was previously isolated as a fermentation-deficient mutant, in which transcription of the major glucose transporter gene RAG1 was affected. The wild-type RAG4 was cloned by complementation of the rag4 mutation and found to encode a protein homologous to Snf3 and Rgt2 of Saccharomyces cerevisiae. These two proteins are thought to be sensors of low and high concentrations of glucose, respectively. Rag4, like Snf3 and Rgt2, is predicted to have the transmembrane structure of sugar transporter family proteins as well as a long C-terminal cytoplasmic tail possessing a characteristic 25-amino-acid sequence. Rag4 may therefore be expected to have a glucose-sensing function. However, the rag4 mutation was fully complemented by one copy of either SNF3 or RGT2. Since K. lactis appears to have no other genes of the SNF3/RGT2 type, we suggest that Rag4 of K. lactis may have a dual function of signaling high and low concentrations of glucose. In rag4 mutants, glucose repression of several inducible enzymes is abolished.

scholarly journals The SWI/SNF KlSnf2 Subunit Controls the Glucose Signaling Pathway To Coordinate Glycolysis and Glucose Transport in Kluyveromyces lactis

2012 ◽  
Vol 11 (11) ◽  
pp. 1382-1390 ◽  
Author(s):  
Pascale Cotton ◽  
Alexandre Soulard ◽  
Micheline Wésolowski-Louvel ◽  
Marc Lemaire
Keyword(s):  
Signaling Pathway ◽  
Glucose Transport ◽  
Chromatin Remodeling ◽  
Kluyveromyces Lactis ◽  
Content Type ◽  
Glucose Signaling ◽  
Helix Loop Helix ◽  
Reverse Transcription Quantitative Pcr ◽  
Extracellular Glucose ◽  
Transcriptional Effect

ABSTRACTInKluyveromyces lactis, the expression of the major glucose permease geneRAG1is controlled by extracellular glucose through a signaling cascade similar to theSaccharomyces cerevisiaeSnf3/Rgt2/Rgt1 pathway. We have identified a key component of theK. lactisglucose signaling pathway by characterizing a new mutation,rag20-1, which impairs the regulation ofRAG1and hexokinaseRAG5genes by glucose. Functional complementation of therag20-1mutation identified theKlSNF2gene, which encodes a protein 59% identical toS. cerevisiaeSnf2, the major subunit of the SWI/SNF chromatin remodeling complex. Reverse transcription-quantitative PCR and chromatin immunoprecipitation analyses confirmed that the KlSnf2 protein binds toRAG1andRAG5promoters and promotes the recruitment of the basic helix-loop-helix Sck1 activator. Besides this transcriptional effect, KlSnf2 is also implicated in the glucose signaling pathway by controlling Sms1 and KlRgt1 posttranscriptional modifications. When KlSnf2 is absent, Sms1 is not degraded in the presence of glucose, leading to constitutiveRAG1gene repression by KlRgt1. Our work points out the crucial role played by KlSnf2 in the regulation of glucose transport and metabolism inK. lactis, notably, by suggesting a link between chromatin remodeling and the glucose signaling pathway.

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