scholarly journals Two glucose sensing/signaling pathways stimulate glucose-induced inactivation of maltose permease in Saccharomyces.

1997 ◽  
Vol 8 (7) ◽  
pp. 1293-1304 ◽  
Author(s):  
H Jiang ◽  
I Medintz ◽  
C A Michels
Keyword(s):  
Signaling Pathways ◽  
Glucose Transport ◽  
Glucose Sensor ◽  
Constitutive Expression ◽  
Glucose Sensing ◽  
Regulation Of Transcription ◽  
Carbohydrate Utilization ◽  
Maltose Permease ◽  
Glucose Levels ◽  
Dependent Signal

Glucose is a global metabolic regulator in Saccharomyces. It controls the expression of many genes involved in carbohydrate utilization at the level of transcription, and it induces the inactivation of several enzymes by a posttranslational mechanism. SNF3, RGT2, GRR1 and RGT1 are known to be involved in glucose regulation of transcription. We tested the roles of these genes in glucose-induced inactivation of maltose permease. Our results suggest that at least two signaling pathways are used to monitor glucose levels. One pathway requires glucose sensor transcript and the second pathway is independent of glucose transport. Rgt2p, which along with Snf3p monitors extracellular glucose levels, appears to be the glucose sensor for the glucose-transport-independent pathway. Transmission of the Rgt2p-dependent signal requires Grr1p. RGT2 and GRR1 also play a role in regulating the expression of the HXT genes, which appear to be the upstream components of the glucose-transport-dependent pathway regulating maltose permease inactivation. RGT2-1, which was identified as a dominant mutation causing constitutive expression of several HXT genes, causes constitutive proteolysis of maltose permease, that is, in the absence of glucose. A model of these glucose sensing/signaling pathways is presented.

scholarly journals Metabolic Signals Trigger Glucose-Induced Inactivation of Maltose Permease in Saccharomyces

2000 ◽  
Vol 182 (3) ◽  
pp. 647-654 ◽  
Author(s):  
Hua Jiang ◽  
Igor Medintz ◽  
Bin Zhang ◽  
Corinne A. Michels
Keyword(s):  
Glucose Transport ◽  
Mammalian Cells ◽  
Glucose Repression ◽  
Carbon Sources ◽  
Glucose Sensing ◽  
High Rate ◽  
Transport Activity ◽  
Maltose Permease ◽  
Maltose Transport ◽  
Rapid Inactivation

ABSTRACT Organisms such as Saccharomyces capable of utilizing several different sugars selectively ferment glucose when less desirable carbon sources are also available. This is achieved by several mechanisms. Glucose down-regulates the transcription of genes involved in utilization of these alternate carbon sources. Additionally, it causes posttranslational modifications of enzymes and transporters, leading to their inactivation and/or degradation. Two glucose sensing and signaling pathways stimulate glucose-induced inactivation of maltose permease. Pathway 1 uses Rgt2p as a sensor of extracellular glucose and causes degradation of maltose permease protein. Pathway 2 is dependent on glucose transport and stimulates degradation of permease protein and very rapid inactivation of maltose transport activity, more rapid than can be explained by loss of protein alone. In this report, we characterize signal generation through pathway 2 using the rapid inactivation of maltose transport activity as an assay of signaling activity. We find that pathway 2 is dependent onHXK2 and to a lesser extent HXK1. The correlation between pathway 2 signaling and glucose repression suggests that these pathways share common upstream components. We demonstrate that glucose transport via galactose permease is able to stimulate pathway 2. Moreover, rapid transport and fermentation of a number of fermentable sugars (including galactose and maltose, not just glucose) are sufficient to generate a pathway 2 signal. These results indicate that pathway 2 responds to a high rate of sugar fermentation and monitors an intracellular metabolic signal. Production of this signal is not specific to glucose, glucose catabolism, glucose transport by the Hxt transporters, or glucose phosphorylation by hexokinase 1 or 2. Similarities between this yeast glucose sensing pathway and glucose sensing mechanisms in mammalian cells are discussed.

scholarly journals Glucose Sensor Using Redox Active Oligonucleotide-Templated Silver Nanoclusters

Nanomaterials ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 1065 ◽  
Author(s):  
Kathryn L. Schroeder ◽  
Renee V. Goreham ◽  
Thomas Nann
Keyword(s):  
Glucose Oxidase ◽  
Glucose Sensor ◽  
Glucose Sensing ◽  
Emission Peak ◽  
Silver Nanoclusters ◽  
Glucose Levels ◽  
Redox Active ◽  
Emission Change

Redox active, photoluminescent silver nanoclusters templated with oligonucleotides were developed for glucose sensing. The silver nanoclusters had a photoluminescent emission at 610 nm that reversibly changed to 530 nm upon oxidation. The reversible emission change was measured with photoluminescent spectroscopy and used to detect H2O2, which is a by-product of the reaction of glucose with glucose oxidase. The ratio of the un-oxidised emission peak (610 nm) and the oxidised analogue (530 nm) was used to measure glucose concentrations up to 20 mM, well within glucose levels found in blood. Also, the reversibility of this system enables the silver nanoclusters to be reused.

scholarly journals A Glucose Sensor in Candida albicans

2006 ◽  
Vol 5 (10) ◽  
pp. 1726-1737 ◽  
Author(s):  
Victoria Brown ◽  
Jessica A. Sexton ◽  
Mark Johnston
Keyword(s):  
Candida Albicans ◽  
Glucose Sensor ◽  
Glucose Sensing ◽  
Glucose Sensors ◽  
Glucose Levels ◽  
High Affinity ◽  
Expression Of Genes ◽  
Hexose Transporters ◽  
Genes Encoding ◽  
Sensor Glucose

ABSTRACT The Hgt4 protein of Candida albicans (orf19.5962) is orthologous to the Snf3 and Rgt2 glucose sensors of Saccharomyces cerevisiae that govern sugar acquisition by regulating the expression of genes encoding hexose transporters. We found that HGT4 is required for glucose induction of the expression of HGT12, HXT10, and HGT7, which encode apparent hexose transporters in C. albicans. An hgt4Δ mutant is defective for growth on fermentable sugars, which is consistent with the idea that Hgt4 is a sensor of glucose and similar sugars. Hgt4 appears to be sensitive to glucose levels similar to those in human serum (∼5 mM). HGT4 expression is repressed by high levels of glucose, which is consistent with the idea that it encodes a high-affinity sugar sensor. Glucose sensing through Hgt4 affects the yeast-to-hyphal morphological switch of C. albicans cells: hgt4Δ mutants are hypofilamented, and a constitutively signaling form of Hgt4 confers hyperfilamentation of cells. The hgt4Δ mutant is less virulent than wild-type cells in a mouse model of disseminated candidiasis. These results suggest that Hgt4 is a high-affinity glucose sensor that contributes to the virulence of C. albicans.

scholarly journals An Equipment-Free, Paper-Based Electrochemical Sensor for Visual Monitoring of Glucose Levels in Urine

2019 ◽  
Vol 24 (5) ◽  
pp. 499-505
Author(s):  
Maedeh Mohammadifar ◽  
Mehdi Tahernia ◽  
Seokheun Choi
Keyword(s):  
Glucose Sensor ◽  
Light Emitting Diode ◽  
Low Cost ◽  
Glucose Sensing ◽  
Glucose Biosensor ◽  
Paper Strip ◽  
Visual Responses ◽  
Free Paper ◽  
Light Emitting ◽  
Glucose Levels

A novel electrochemical glucose sensor was created for a simple but semiquantitative visual screening of specific glucose concentrations in urine. This noninvasive glucose biosensor integrated a disposable, paper-based sensing strip and a simple amplifier circuit with a visual readout. The paper strip consisted of five enzyme-activated electrodes. Each electrode was connected to a specific indicator circuit that triggered a light-emitting diode (LED) when a predefined glucose concentration was reached. The device features (1) low-cost, disposable, paper-based glucose oxidase (GOx)/poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) sensing electrodes, (2) simple signal amplification, and (3) on-site, rapid, and visual detection. The sensor generated reliable, discrete visual responses to determine five glucose levels (1, 2, 3, 4, and higher than 4 mM) in urine in less than 2 min. This innovative approach will provide a simple but powerful glucose sensing paradigm for use in POC diagnostics.

New perspectives on pancreatic islet glucokinase

1984 ◽  
Vol 246 (1) ◽  
pp. E1-E13 ◽  
Author(s):  
M. D. Meglasson ◽  
F. M. Matschinsky
Keyword(s):  
Beta Cells ◽  
Insulin Release ◽  
Type Ii Diabetes ◽  
Glucose Sensor ◽  
Glucose Sensing ◽  
Glucose Disposal ◽  
Type Ii ◽  
Glucose Levels ◽  
Diabetes Type Ii ◽  
Qualified Candidate

Control of blood sugar involves the complex interaction of the pancreatic glucose-sensing beta-cells with the liver, which serves as the primary site of glucose disposal after a meal. Glucokinase occupies an important role in controlling glucose phosphorylation and metabolism both in the liver and in pancreatic islets. In the beta-cells, glucokinase functions as pacemaker of glycolysis at physiological glucose levels. It determines the unique characteristics of islet hexose usage, that is, the rate, affinity, cooperativity, and anomeric discrimination of glucose metabolism. Because glycolysis controls hexose-induced insulin release, glucokinase is considered the best-qualified candidate for the elusive glucose sensor of beta-cells. A deficiency of glucokinase would disturb glucose homeostasis. Decreased islet glucokinase would diminish islet glycolysis and would result in a higher set point of beta-cells for glucose-induced insulin release. Decreased liver glucokinase would cause less efficient hepatic glucose disposal. Human maturity-onset diabetes (type II diabetes) has these characteristics. It is thus conceivable that certain forms of type II diabetes are due to a glucokinase deficiency.

Possibility of distinct insulin-signaling pathways beyond phosphatidylinositol 3-kinase-mediating glucose transport and lipogenesis

Diabetes ◽  
1998 ◽  
Vol 47 (2) ◽  
pp. 179-185 ◽  
Author(s):  
R. W. Stevenson ◽  
D. K. Kreutter ◽  
K. M. Andrews ◽  
P. E. Genereux ◽  
E. M. Gibbs
Keyword(s):  
Signaling Pathways ◽  
Glucose Transport ◽  
Insulin Signaling ◽  
Phosphatidylinositol 3 Kinase ◽  
Phosphatidylinositol 3

The Artificial Pancreas in Cyborg Bodies

2020 ◽  
pp. 412-430
Author(s):  
Anthony Ryan Hatch ◽  
Julia T. Gordon ◽  
Sonya R. Sternlieb
Keyword(s):  
Glucose Sensor ◽  
Social Inequalities ◽  
Infusion Pump ◽  
Artificial Pancreas ◽  
Small Scale ◽  
Glucose Levels ◽  
Loop Design ◽  
Access To Health ◽  
Do It Yourself ◽  
And Control

The new artificial pancreas system includes a body-attached blood glucose sensor that tracks glucose levels, a worn insulin infusion pump that communicates with the sensor, and features new software that integrates the two systems. The artificial pancreas is purportedly revolutionary because of its closed-loop design, which means that the machine can give insulin without direct patient intervention. It can read a blood sugar and administer insulin based on an algorithm. But, the hardware for the corporate artificial pancreas is expensive and its software code is closed-access. Yet, well-educated, tech-savvy diabetics have been fashioning their own fully automated do-it-yourself (DIY) artificial pancreases for years, relying on small-scale manufacturing, open-source software, and inventive repurposing of corporate hardware. In this chapter, we trace the corporate and DIY artificial pancreases as they grapple with issues of design and accessibility in a content where not everyone can become a diabetic cyborg. The corporate artificial pancreas offers the cyborg low levels of agency and no ownership and control over his or her own data; it also requires access to health insurance in order to procure and use the technology. The DIY artificial pancreas offers patients a more robust of agency but also requires high levels of intellectual capital to hack the devices and make the system work safely. We argue that efforts to increase agency, radically democratize biotechnology, and expand information ownership in the DIY movement are characterized by ideologies and social inequalities that also define corporate pathways.

scholarly journals Waste eggshell membrane-templated synthesis of functional Cu2+–Cu+/biochar for an ultrasensitive electrochemical enzyme-free glucose sensor

RSC Advances ◽  
2021 ◽  
Vol 11 (31) ◽  
pp. 18994-18999
Author(s):  
Linzhi Li ◽  
Tianzeng Huang ◽  
Saijun He ◽  
Xing Liu ◽  
Qi Chen ◽  
...  
Keyword(s):  
Glucose Sensor ◽  
Glucose Sensing ◽  
Fabrication Process ◽  
Eggshell Membrane ◽  
Templated Synthesis ◽  
Free Glucose

The fabrication process of the nonenzyme glucose sensing based Cu2+–Cu+/biochar.

scholarly journals Insulin blunts the response of glucose-excited neurons in the ventrolateral-ventromedial hypothalamic nucleus to decreased glucose

2009 ◽  
Vol 296 (5) ◽  
pp. E1101-E1109 ◽  
Author(s):  
Victoria E. Cotero ◽  
Vanessa H. Routh
Keyword(s):  
Energy Homeostasis ◽  
Ventromedial Hypothalamus ◽  
Glucose Sensing ◽  
Hypothalamic Nucleus ◽  
Compensatory Mechanisms ◽  
Glucose Levels ◽  
Compound C ◽  
Obesity And Diabetes ◽  
Extracellular Glucose ◽  
Pi3k Signaling Pathway

Insulin signaling is dysfunctional in obesity and diabetes. Moreover, central glucose-sensing mechanisms are impaired in these diseases. This is associated with abnormalities in hypothalamic glucose-sensing neurons. Glucose-sensing neurons reside in key areas of the brain involved in glucose and energy homeostasis, such as the ventromedial hypothalamus (VMH). Our results indicate that insulin opens the KATP channel on VMH GE neurons in 5, 2.5, and 0.1 mM glucose. Furthermore, insulin reduced the sensitivity of VMH GE neurons to a decrease in extracellular glucose level from 2.5 to 0.1 mM. This change in the glucose sensitivity in the presence of insulin was reversed by the phosphatidylinositol 3-kinase (PI3K) inhibitor wortmannin (10 nM) but not by the mitogen-activated kinase (MAPK) inhibitor PD-98059 (PD; 50 μM). Finally, neither the AMPK inhibitor compound C nor the AMPK activator AICAR altered the activity of VMH GE neurons. These data suggest that insulin attenuates the ability of VMH GE neurons to sense decreased glucose via the PI3K signaling pathway. Furthermore, these data are consistent with the role of insulin as a satiety factor. That is, in the presence of insulin, glucose levels must decline further before GE neurons respond. Thus, the set point for detection of glucose deficit and initiation of compensatory mechanisms would be lowered.

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