Interaction of 6-Phosphofructo-2-Kinase/Fructose-2,6-Bisphosphatase (PFK-2/FBPase-2) With Glucokinase Activates Glucose Phosphorylation and Glucose Metabolism in Insulin-Producing Cells

Massa, Laura; Baltrusch, Simone; Okar, David A.; Lange, Alex J.; Lenzen, Sigurd; Tiedge, Markus

doi:10.2337/diabetes.53.4.1020

Cited by 90 publications

(122 citation statements)

References 72 publications

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“…This discrepancy between our results and previous findings could be related to the different origin of these proteins (rat and human). In addition to DUSP12, PFKFB1 has previously been shown to interact with GCK in yeast two-hybrid assays [10] and a physiological role for this interaction was reported in pancreatic beta cells and hepatocytes [11,32]. We confirmed the interaction of GCK with PFKFB1 in pull-down experiments.…”

Section: Discussionsupporting

confidence: 77%

“…In addition, GCK activity is regulated through protein-protein interactions by the glucokinase (hexokinase 4) regulator (GCKR, also known as glucokinase regulatory protein [GKRP]), which acts as a competitive inhibitor with respect to glucose and also regulates the nucleo-cytoplasmic localisation of the enzyme [7][8][9]. In addition, GCK has been shown to associate with other partners, such as the bifunctional enzyme 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFKFB1, also known as PFK2) [10,11], a dual specificity phosphatase [12], the neuronal isoform of nitric oxide synthase [13], the proapoptotic Bcell leukaemia/lymphoma 2 (BCL2) family member BCL2-antagonist of cell death (BAD) [14] and the precursor of the propionyl-CoA carboxylase beta subunit [15]. Nevertheless, the biological significance of some of these interactions remains to be elucidated.…”

Section: Introductionmentioning

confidence: 99%

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Functional analysis of human glucokinase gene mutations causing MODY2: exploring the regulatory mechanisms of glucokinase activity

et al. 2006

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Aims/hypothesis Glucokinase (GCK) acts as a glucose sensor in the pancreatic beta cell and regulates insulin secretion. In the gene encoding GCK the heterozygous mutations that result in enzyme inactivation cause MODY2. Functional studies of naturally occurring GCK mutations associated with hyperglycaemia provide further insight into the biochemical basis of glucose sensor regulation. Materials and methods Identification of GCK mutations in selected MODY patients was performed by single-strand conformation polymorphism and direct sequencing. The kinetic parameters and thermal stability of recombinant mutant human GCK were determined, and in pull-down assays the effect of these mutations on the association of GCK with glucokinase (hexokinase 4) regulator (GCKR, also known as glucokinase regulatory protein [GKRP]) and 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFKFB1, also known as PFK2) was tested. Results We identified three novel GCK mutations: the insertion of an asparagine residue at position 161 (inserN161) and two missense mutations (M235V and R308W). We also identified a fourth mutation (R397L) reported in a previous work. Functional characterisation of these mutations revealed that insertion of asparagine residue N161 fully inactivates GCK, whereas the M235V and R308W mutations only partially impair enzymatic activity. In contrast, GCK kinetics was almost unaffected by the R397L mutation. Although none of these mutations affected the interaction of GCK with PFKFB1, we found that the R308W mutation caused protein instability and increased the strength of interaction with GCKR. Conclusions/interpretation Our results show that different MODY2 mutations impair GCK function through different mechanisms such as enzymatic activity, protein stability and increased interaction with GCKR, helping further elucidate the regulation of GCK activity.

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Section: Discussionsupporting

confidence: 77%

Section: Introductionmentioning

confidence: 99%

Functional analysis of human glucokinase gene mutations causing MODY2: exploring the regulatory mechanisms of glucokinase activity

et al. 2006

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“…In this sense, we cannot discard other short-term effects, i.e. the interactions of GK and GKRP present in the hypothalamus of rat and human brain (Alvarez et al 2002(Alvarez et al , 2005 or GK-PFK2 interaction as occurs in liver and b-cells (Massa et al 2004, Baltrusch & Tiedge 2006.…”

Section: Effect Of Ins and Other Peptides On Gk Activities In Hypothamentioning

confidence: 99%

Effects of glucose and insulin on glucokinase activity in rat hypothalamus

Sanz¹,

Roncero²,

Vázquez³

et al. 2007

Journal of Endocrinology

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In an attempt to study the role of glucokinase (GK) and the effects of glucose and peptides on GK gene expression and on the activity of this enzyme in the hypothalamus, we used two kinds of biological models: hypothalamic GT1-7 cells and rat hypothalamic slices. The expression of the GK gene in GT1-7 cells was reduced by insulin (INS) and was not modified by different glucose concentrations, while GK enzyme activities were significantly reduced by the different peptides. Interestingly, a distinctive pattern of GK activities between the ventromedial hypothalamus (VMH) and lateral hypothalamus (LH) were found, with higher enzyme activities in the VMH as the glucose concentrations rose, while LH enzyme activities decreased at 2 . 8 and 20 mM glucose, the latter effect being prevented by incubation with INS. These effects were produced only by D-glucose and the modifications found were due to GK, but not to other hexokinases. In addition, GK activities in the VMH and the LH were reduced by glucagonlike peptide 1, leptin, orexin B, INS, and neuropeptide Y (NPY), but this effect was only statistically significant for NPY in LH. Our results indicate that the effects of both glucose and peptides occur on GK enzyme activities rather than on GK gene transcription. Moreover, the effects of glucose and INS on GK activity suggest that in the brain GK behaves in a manner opposite to that in the liver, which might facilitate its role in glucose sensing. Finally, hypothalamic slices seem to offer a good physiological model to discriminate the effects between different areas.

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“…Even so, it is unclear how generalizable our findings are with regard to the specific receptors involved in ER Ca 2ϩ release. Some studies clearly favor a role for IP 3 Rs over ryanodine receptors in receptor-mediated potentiation of [glucose] mM FIGURE 7. Glucose-stimulated regulation of GCK in islets.…”

Section: Mechanism Of Gck Control By Er Camentioning

confidence: 99%

“…3 Under sufficiently high glucose concentrations in vitro, GCK undergoes a conformational shift that accelerates its activity and gives it a non-allosteric sigmoidal dependence for glucose (1). In cells, enhanced GCK activity can be achieved through cysteine S-nitrosylation via reaction with NO (2) or by interaction with the phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFK2) bifunctional enzyme (3,4). Our laboratory has extensively characterized the regulation of GCK by the NO pathway, describing roles for GCK S-nitrosylation in human diabetes (5), incretin hormone signaling (6), and regulation of GCK protein levels (7).…”

mentioning

confidence: 99%

Regulation of Glucokinase by Intracellular Calcium Levels in Pancreatic β Cells

Markwardt

Seckinger

Rizzo

2016

Journal of Biological Chemistry

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Glucokinase (GCK) controls the rate of glucose metabolism in pancreatic ␤ cells, and its activity is rate-limiting for insulin secretion. Posttranslational GCK activation can be stimulated through either G protein-coupled receptors or receptor tyrosine kinase signaling pathways, suggesting a common mechanism. Here we show that inhibiting Ca 2؉ release from the endoplasmic reticulum (ER) decouples GCK activation from receptor stimulation. Furthermore, pharmacological release of ER Ca 2؉ stimulates activation of a GCK optical biosensor and potentiates glucose metabolism, implicating rises in cytoplasmic Ca 2؉ as a critical regulatory mechanism. To explore the potential for glucose-stimulated GCK activation, the GCK biosensor was optimized using circularly permuted mCerulean3 proteins. This new sensor sensitively reports activation in response to insulin, glucagon-like peptide 1, and agents that raise cAMP levels. Transient, glucose-stimulated GCK activation was observed in ␤TC3 and MIN6 cells. An ER-localized channelrhodopsin was used to manipulate the cytoplasmic Ca 2؉ concentration in cells expressing the optimized FRET-GCK sensor. This permitted quantification of the relationship between cytoplasmic Ca 2؉ concentrations and GCK activation. Half-maximal activation of the FRET-GCK sensor was estimated to occur at ϳ400 nM Ca 2؉ . When expressed in islets, fluctuations in GCK activation were observed in response to glucose, and we estimated that posttranslational activation of GCK enhances glucose metabolism by ϳ35%. These results suggest a mechanism for integrative control over GCK activation and, therefore, glucose metabolism and insulin secretion through regulation of cytoplasmic Ca 2؉

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Interaction of 6-Phosphofructo-2-Kinase/Fructose-2,6-Bisphosphatase (PFK-2/FBPase-2) With Glucokinase Activates Glucose Phosphorylation and Glucose Metabolism in Insulin-Producing Cells

Cited by 90 publications

References 72 publications

Functional analysis of human glucokinase gene mutations causing MODY2: exploring the regulatory mechanisms of glucokinase activity

Functional analysis of human glucokinase gene mutations causing MODY2: exploring the regulatory mechanisms of glucokinase activity

Effects of glucose and insulin on glucokinase activity in rat hypothalamus

Regulation of Glucokinase by Intracellular Calcium Levels in Pancreatic β Cells

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