help button home button Endocrine Society Endocrinology
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Purchase Article
Right arrow View Shopping Cart
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow Request Copyright Permission
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Fernandez-Mejia, C.
Right arrow Articles by German, M. S.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Fernandez-Mejia, C.
Right arrow Articles by German, M. S.
Endocrinology Vol. 142, No. 4 1448-1452
Copyright © 2001 by The Endocrine Society

ARTICLES

Cyclic Adenosine 3',5'-Monophosphate Increases Pancreatic Glucokinase Activity and Gene Expression1

Cristina Fernandez-Mejia, Jesus Vega-Allende, Alberto Rojas-Ochoa, Mauricio Rodriguez-Dorantes, Guillermo Romero-Navarro, Franz M. Matschinsky, Juehu Wang and Michael S. German

Nutritional Genetics Unit (C.F.M., J.V., A.R.O.), Biomedical Research Institute, National University of México, and School of Chemistry, National University of Mexico (M.R.D.), México City, C.P. 04530, México; School of Chemical-Biological Sciences (G.R.N.), Autonomous University of Sinaloa, Culiacán, Sinaloa, C.P. 80000, México; Hormone Research Institute, University of California (M.S.G., J.W.), San Francisco, California 94143-0534; and Diabetes Research Center, University of Pennsylvania Medical Center (F.M.M.), Philadelphia, Pennsylvania 19104-6015

Address all correspondence and requests for reprints to: Dr. Cristina Fernandez-Mejia, Unidad de Genetica de la Nutricion, Instituto de Investigaciones Biomedicas Universidad Nacional Autónoma de México/Instituto Nacional de Peditría, Avenue del Iman 1, Fourth Floor, México City, C.P. 04530, México. E-mail: crisfern{at}servidor.unam.mx


   Abstract
Top
 Abstract
Introduction
 Materials and Methods
 Results
 Discussion
 References
 
Comparison of the pancreatic and hepatic glucokinase gene transcripts reveals tissue-specific control of expression and the existence of two distinct promoters in a single glucokinase gene. The existence of alternate promoters suggests that separate factors regulate glucokinase transcription in the two tissues. Hepatic glucokinase expression has been shown to be repressed by cAMP; however, in the pancreatic ß-cell it is unlikely that cAMP represses glucokinase activity, as cAMP is known to positively affect glucose-induced insulin secretion, a process that in mature islets requires pancreatic glucokinase activity. In this work we demonstrate that cAMP indeed has a stimulatory effect on pancreatic glucokinase. The cyclic nucleotide stimulates pancreatic glucokinase activity after 3-h incubation, and maximal effects are observed after 6 and 12 h of treatment. Using the bDNA assay, a sensitive signal amplification technique, we detected relative increases in glucokinase messenger RNA levels of 40.5 ± 7.5% after 3-h incubation with cAMP. This stimulatory effect was increased to 106.3 ± 22% after 6-h incubation and sustained up to 12 h of incubation. Inhibition of gene transcription by actinomycin D abolishes cAMP-induced glucokinase activity. In transfected fetal islets, cAMP increased the activity of the -1000 bp rat glucokinase promoter by 60 ± 6%. These data demonstrate that cAMP has a stimulatory effect on pancreatic glucokinase gene expression and that the nucleotide has opposite effects on pancreatic and hepatic glucokinase, supporting the concept that glucokinase transcription in the liver and that in the ß-cell differ.


   Introduction
Top
 Abstract
 Introduction
Materials and Methods
 Results
 Discussion
 References
 
GLUCOKINASE (EC 2.7.1.1) is a tissue-specific enzyme present in hepatocytes, pancreatic ß-cells, and certain neuroendocrine cells of the brain and gut (1, 2, 3, 4, 5). Glucokinase plays a key role in glucose homeostasis, regulating insulin secretion in response to glucose in the ß-cells (6, 7) and uptake of glucose in the liver (8, 9). In humans, mutations in the glucokinase gene cause maturity-onset diabetes of the youth (10) or hyperinsulinemia (11).

Comparison of the pancreatic and hepatic glucokinase gene transcripts reveals a tissue-specific control of their expression as well as the existence of two distinct promoters in a single glucokinase gene (12, 13). The existence of alternate promoters suggests that separate factors regulate glucokinase transcription in the two tissues. In the liver, glucokinase activity is regulated at the level of gene transcription in response to fasting and refeeding (14), with insulin and glucagon serving as the mediators of this response (15, 16, 17). In contrast, in pancreatic ß-cells, glucose levels modulate glucokinase activity (2, 18, 19), and this modulation apparently occurs through posttranscriptional mechanisms (19). This difference might be expected considering the different functions of these two tissues in glucose homeostasis. In previous reports we have also demonstrated that pancreatic glucokinase transcription and activity are regulated by several hormones and vitamins, and that this hormonal regulation differs in hepatic and pancreatic genes (20, 21, 22).

In the liver glucokinase gene transcription is decreased by glucagon through increases on cAMP (15, 17, 23). This effect is consistent with the role of glucagon favoring gluconeogenesis and glycogenolysis. However, in the pancreatic ß-cell it is unlikely that cAMP represses glucokinase activity, because cAMP is known to positively affect glucose-induced insulin secretion, a process that in mature islets requires pancreatic glucokinase activity (24, 25, 26). In this work we investigated the effect of cAMP on glucokinase enzyme activity and gene expression. We chose pancreatic fetal islets because of their high percentage of ß-cell yield, their capacity to be transfected with the glucokinase promoter, and the lesser amount of time required for their isolation compared with the adult islets.


   Materials and Methods
Top
 Abstract
 Introduction
 Materials and Methods
Results
 Discussion
 References
 
Fetal islet culture
Twenty-one-day-gestation fetal Wistar rat islets were isolated as described previously (27). Briefly, pancreatic glands obtained from four to six rats were finely minced and digested with collagenase type D and 2 µl deoxyribonuclease I (Roche Molecular Biochemicals, Mannheim, Germany). The washed digest was suspended in RPMI 1640 medium containing 10% FBS, 11 mM glucose, 400 U/ml penicillin, and 200 mg streptomycin (Life Technologies, Inc., Gaithersburg, MD; supplemented RPMI 1640 medium) and distributed equally into two 60-mm tissue culture dishes (Costar, Cambridge, MA). Cultures were incubated for 5 h at 37 C in a humidified atmosphere of 5% CO2 to deplete them of fibroblasts. Islets were then seeded into 60-mm tissue culture dishes (Costar, Cambridge, MA) and treated either with 8-bromo-cAMP (Sigma, St. Louis, MO) or vehicle (RPMI 1640) at the concentrations and times indicated in the text. In experiments in which RNA synthesis was inhibited, islets were preincubated with or without actinomycin D1 at a concentration of 5 µg/ml for 1 h and then treated either with 8-bromo-cAMP (10-4 M) or vehicle (RPMI 1640) for 3 h.

Glucokinase assay
Islets from five or six pancreases, were harvested and centrifuged at 1200 rpm. Tissue pellets were lysed in 500 µl reporter lysis buffer (Promega Corp., Madison, WI) and vortexed, and cell membranes were disrupted by three freeze-thaw cycles. Five hundred microliters of GK buffer consisting of 50 mM Tris (pH 7.6), 4 mM EDTA, 150 mM KCl, 4 mM Mg2SO4, and 2.5 mM dithiothreitol were added. The lysates were then centrifuged at 4 C for 1 h at 35,000 x g in an ultracentrifuge (model Optima, Beckman Coulter, Inc., Palo Alto, CA). Supernatants were recovered, and enzymatic activity was assayed as described previously by Walker and Parry (28), using NAD (Sigma) as the coenzyme. Glucose-6-phosphate dehydrogenase from Leuconostoc mesenteroides (Sigma) was used as the coupling enzyme. Correction for low hexokinase activity was applied by subtracting the activity measured at 0.5 mM glucose from the activity measured at 100 mM glucose. Protein concentrations were determined by Bradford assay (29).

Messenger RNA (mRNA) analysis
Glucokinase and actin mRNA were quantified using branched DNA (bDNA) technology in a 96-microwell format as previously described for quantification of insulin pre-RNA and glucokinase (21, 30). All components, including buffers and DNA reagents, were obtained from Chiron Corp. (Emeryville, CA). RNA was extracted by either TRIzol (Life Technologies, Inc.) or cell lysis with 400 µl extraction buffer [78 mM HEPES (pH 8.0), 12.5 mM EDTA (pH 8.0), 6.27 mM LiCl, 1.6 lithium lauryl sulfate, proteinase K (1 mg/ml), single stranded DNA (19 µg/ml), 7.8% formamide, 0.05% sodium azide, and 0.05% Proclin 300]. RNA samples were mixed with 200 µl extraction buffer along with proteinase K and glucokinase capture and label probes, loaded in the microwell plate, sealed with an adhesive-backed mylar plate sealer (Microtiter Plate Sealer, Flow Laboratory, Rockville, MD), and incubated overnight at 63 C in a plate heater to capture the targeted nucleic acids to the oligonucleotide-modified microwell surface. After cooling at room temperature for 10 min, cells were washed twice with wash A (Chiron Corp.). Fifty microliters of branched DNA (bDNA) amplifier solution containing the bDNA amplifier probe at 1 pmol/ml in amplifier diluent (Chiron Corp.) were added and hybridized at 53 C for 30 min. After cooling and washing as described above, 50 µl of a mixture containing alkaline phosphatase-conjugated label probes (2 pmol/ml) in label diluent (Chiron Corp.) were added and hybridized at 53 C for 15 min. The plate was cooled and washed twice in buffer A as described above and then washed three times with wash solution B (Chiron Corp., Emeryville, CA). Finally, 50 µl chemiluminescent substrate (Lumiphos 530), an enzyme-triggered dioxetane substrate for alkaline phosphatase, were added, and the plate was incubated at 37 C for 25 min. Light emission was measured in a luminometer at 37 C. Each sample was assayed in triplicate and standardized to actin mRNA.

Plasmid constructs
The construction of pFOXCAT1 has been described previously (31). The rat ß-cell glucokinase 1000 promoter extends from -1000 to +14 bp and was a gift from M. Magnuson (Vanderbilt University, Nashville, TN) (32). The simian virus 40-luciferase pGL3-Control vector (Promega Corp.) was donated by Dr. E. Garrido (National Polytechnique Institute) and Dr. F. López-Casillas (National University of México, México City, México).

Fetal islet transfection
Experiments were performed as previously described by German et al. (33); briefly, 21-day-gestation fetal Wistar rat islets were isolated and digested for 5 min with collagenase type P and 2 µl deoxyribonuclease I (Roche). After 3 h of plating to deplete fibroblasts, islets were recovered and dispersed with 0.05% trypsin and 0.53 mM EDTA (Life Technologies, Inc.). Dispersed islets were incubated at 37 C in a humidified atmosphere of 5% CO2 after 3 h of plating to deplete culture of fibroblasts, then cells were harvested by rinsing the plates, pelleted, washed twice in room temperature PBS, resuspended in 0.8 ml PBS with 25 µg double cesium-purified plasmid DNA, and electroporated with a discharge of 175 V and 2000 µfarad in a BTX electroporation system model 600 (San Diego, CA). In cotransfection experiments 12.5 µg simian virus 40-luciferase vector were also added. The transfected cells were grown in supplemented RPMI containing 11 mM glucose with 8-bromo-cAMP (10-4 M) or vehicle (RPMI 1640) for approximately 48 h before harvesting and protein extraction. Chloramphenicol acetyltransferase (CAT) TLC was performed using 25 µg protein, and to generate enough CAT product, the sample was incubated for 3 h. CAT signals were analyzed using a PhosphorImager 425 (Molecular Dynamics, Inc., Costa Mesa, CA) or were counted in a scintillation counter (Minamaxi-ß Tri-carb, United Technologies, Packard, Meriden, CT). A commercial kit was used to measure luciferase activity (Promega Corp.).

Statistics
Data are presented as the mean ± SE. Individual comparisons were evaluated by Student’s paired two-tailed t test. Multiple comparisons were evaluated using one-way ANOVA. The significance level chosen was P < 0.05.


   Results
Top
 Abstract
 Introduction
 Materials and Methods
 Results
Discussion
 References
 
cAMP effect on glucokinase activity
We investigated the effects of different concentrations of cAMP on glucokinase activity in islets isolated from 21-day fetal rats. As shown in Fig. 1Go, 24-h incubation with cAMP concentrations as low as 10-5 M increased glucokinase activity significantly by 22 ± 4.8% (P < 0.05), and a cAMP concentration of 10-4 M produced a maximal increase (176.9 ± 6.6%). No further increase was achieved by a concentration of 10-3 M. In the same experimental model we assessed the time course of cAMP effect. As shown in Fig. 2Go, a cAMP concentration of 10-4 M increased glucokinase activity significantly (50.3 ± 20.2%; P < 0.05) after 3-h incubation. Greater increases of 116.5 ± 40% and 140.6 ± 17% were observed at 6 and 12 h of treatment, respectively. After 24-h incubation, the stimulatory effect of the cyclic nucleotide was only 76.9 ± 6.6%. A similar positive effect of cAMP on glucokinase activity was observed in both cultured adult islets and in RIN-m5F insulinoma cells (data not shown).



View larger version (51K):
[in this window]
[in a new window]
  		Figure 1. Effects of different concentrations of cAMP on glucokinase activity in primary cultures of fetal islets. Islets from 21-day-gestation fetal Wistar rats were obtained by collagenase digestion as described in Materials and Methods and were cultured for 24 h in the absence or presence of the designated concentrations of 8-bromo-cAMP. Each bar represents the mean percentage ± SE of glucokinase activity of six independent experiments (control glucokinase activity, 97.5 ± 12 pmol/h·islet). Significance was assessed by one-way ANOVA. The significance level chosen was P < 0.05.

 


View larger version (49K):
[in this window]
[in a new window]
  		Figure 2. Time-course effect of cAMP on glucokinase activity in primary cultures of islets. Islets from 21-day-gestation fetal Wistar rats were obtained by collagenase digestion as described in Materials and Methods and cultured for the indicated periods of time in either the absence or presence of 10-4 M 8-bromo-cAMP. Each bar represents the mean percentage ± SE of glucokinase activity of three to six independent experiments (control glucokinase activity, 102.5 ± 22 pmol/h·islet). Significance was assessed by one-way ANOVA. *, P <= 0.05.

 
cAMP effect on glucokinase mRNA levels
We determined whether the stimulatory effect of cAMP on glucokinase activity was related to an increase in glucokinase gene expression. Because glucokinase mRNA levels are low, we adapted the bDNA assay, a sensitive signal amplification technique (21, 30), to measure glucokinase mRNA levels. Each sample was standardized to actin, a constitutive mRNA that was not modified by the treatment. A cAMP concentration of 10-4 M for 3 h produced a relative increase of 40.5 ± 7.5% in glucokinase RNA levels; this stimulatory effect was increased to 106.3 ± 22% at 6 h of incubation and was sustained up to 12 h of incubation with the nucleotide (103 ± 15%). The effect was reduced to 41 ± 7.2% at 24 h (Fig. 3Go).



View larger version (56K):
[in this window]
[in a new window]
  		Figure 3. Effect of cAMP on glucokinase mRNA levels. Glucokinase mRNA was quantified using bDNA technology. Islets from 21-day-gestation fetal Wistar rats were cultured for the indicated periods of time in either the absence or presence of 10-4 M 8-bromo-cAMP. Each sample was standardized to actin, a constitutive gene that was not modified by the treatment (3 h, 101.13 ± 12%; 6 h, 99.7 ± 18%; 12 h, 87.3 ± 15.3%; 24 h, 86.2 ± 2.2%). Data are expressed as relative to those measured in cells without treatment. Each value represents the mean ± SE of three to five independent experiments. Significance was assessed by one-way ANOVA. *, P <= 0.05.

 
To determine whether the rapid increase in glucokinase activity in response to cAMP was related to the increase observed in its mRNA levels, we analyzed glucokinase activity in islets in which gene transcription was inhibited by actinomycin D. As shown in Fig. 4Go, the increase in glucokinase activity was prevented by the inhibitor. Microscopic analysis showed that the treatment with actinomycin did not affect the viability of the islets (data not shown).



View larger version (38K):
[in this window]
[in a new window]
  		Figure 4. Effect of actinomycin-inhibited transcription on glucokinase activity. Islets from 21-day-gestation fetal Wistar rats were preincubated with or without actinomycin D at a concentration of 5 µg/ml for 1 h, then treated either with 8-bromo-cAMP (10-4 M) or vehicle (RPMI 1640) for 3 h. Left panel, Islets treated with actinomycin; Right panel, Islets without actinomycin. Each value represents the mean ± SE of four experiments.

 
Effect of cAMP on glucokinase promoter activity
A construct containing -1000 kb of pancreatic glucokinase promoter driving the CAT reporter gene was transfected into primary cultures of fetal islets. Treatment with 10-3 M cAMP for 48 h increases glucokinase promoter activity by 60 ± 6% (Fig. 5Go). cAMP has no effect on the empty pFOX-CAT1 vector containing no promoter upstream of the CAT reporter gene. In cotransfection studies with a vector containing luciferase gene to correct for transfection efficiency, similar cAMP effects were observed (pFOX-CAT, 1.5 ± 10.5%; -1000 kb, 76.5 ± 10%; n = 2).



View larger version (31K):
[in this window]
[in a new window]
  		Figure 5. Effect of cAMP on glucokinase promoter activity. Fetal islets were transfected with pFOXCAT1 containing -1000 to +14 bp of rat ß-cell glucokinase promoter (A) or with the empty vector pFOXCAT1 (B). The cells were then incubated in medium in the presence or absence of 8-bromo-cAMP (10-4 M) for approximately 48 h. CAT activity was then assayed in 25 µg protein of the cell extracts and expressed relative to that measured in cells incubated without treatment. Each value represents the mean ± SE of three experiments. Significance was assessed by Student’s unpaired two-tailed t test. *, P <= 0.05.

 

   Discussion
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
References
 
In the present study we demonstrate that cAMP stimulates pancreatic glucokinase gene expression and glucokinase enzyme activity. This stimulatory effect of cAMP on pancreatic glucokinase is in contrast to the repressive effect of cAMP on hepatic glucokinase (15, 17, 23). This difference is in agreement with the different roles of cAMP in these two tissues. In the liver, cAMP mediates the effects of glucagon, which stimulates glucose production by the liver and therefore opposes the glucose catabolic pathways involving glucokinase. In contrast, in the ß-cell cAMP increases insulin secretion, a process that in mature islets is dependent on glucokinase.

The effect of cAMP on glucokinase is observed within 3 h of incubation with cAMP and peaks around 12 h. The facts that the rapid effect of cAMP on pancreatic glucokinase activity was paralleled by an increase in glucokinase mRNA levels, and that inhibition of mRNA synthesis by actinomycin suppresses the stimulatory effect of cAMP on glucokinase activity suggest that cAMP exerts its effect through the stimulation of pancreatic glucokinase gene expression. The positive effect of cAMP on glucokinase activity and mRNA levels was also observed in adult islets and in RINm5F (data not shown). The similar response of cAMP in fetal and adult islets is in agreement with previous observations (21, 34), indicating that glucokinase responds in a similar manner to different agents in fetal and in adult islets. Our results contrast with a previous report of Hinata et al. (35) that cAMP concentrations of 5 x 10-3 M decreased pancreatic glucokinase mRNA levels. These researchers, however, did not analyze other concentrations of the nucleotide and did not analyze the effect on glucokinase enzymatic activity or promoter activity.

We also demonstrated the ability of cAMP to activate the -1000 kb ß-cell glucokinase promoter, providing further evidence that cAMP affects pancreatic glucokinase gene transcription. However, we could not identify any cAMP response element consensus sequence on the -1000 kb ß cell glucokinase promoter. Further studies will be required to determine the precise mechanisms that mediate the cAMP effect on the pancreatic glucokinase promoter.

We and others have previously demonstrated that glucokinase isoenzymes are regulated differently in the pancreatic ß-cell and the liver (2, 19, 20), supporting the concept that alternate promoters and first exons confer differential isoenzyme regulation. In the pancreatic ß-cell, glucose acts as a positive regulator of glucokinase enzyme activity (2). Posttranscriptional regulation has been invoked to explain glucose induction of glucokinase in the ß-cell (19). In the liver, insulin, not glucose, is the positive stimulus for glucokinase activity and gene transcription (2, 15, 16, 17). Previously (20) we have shown that, in contrast to the stimulatory effect of thyroid hormone (T3) on hepatic glucokinase (36, 37, 38), the activity of pancreatic glucokinase is not affected by T3 despite the negative effect of T3 on glucokinase mRNA levels. The development of the enzyme in the islet and that in the liver also differ. In the pancreatic ß-cell, glucokinase is already present during fetal life (34), whereas in the liver glucokinase appears 2 weeks after birth (39, 40). The repression of glucokinase gene transcription in response to glucagon via cAMP is an essential feature of hepatic glucokinase regulation (15, 17, 23), but in this work we demonstrate that cAMP produces an increase in pancreatic glucokinase activity and expression.

Several studies have investigated the mechanisms by which an increase in cAMP potentiates glucose-induced insulin secretion. Increased rates of phosphorylation of ion channels in the ß-cell membrane via cAMP-dependent protein kinase A may be a mechanism leading to increased ß-cell sensitivity to primary stimuli (41, 42, 43, 44). In addition, cAMP has been shown to promote insulin release by an action distal to the regulatory steps of the secretory machinery (44, 45, 46). It appears, however, that increases in glucokinase gene expression also may contribute to the potentiation of glucose-induced insulin secretion induced by the cyclic nucleotide. Further studies will be required to determine the relative contribution of increased glucokinase activity to the overall effects of cAMP on insulin secretion.


   Acknowledgments
 
We are indebted to Dr. M. Magnuson (Vanderbilt University) for the glucokinase promoter plasmid. We are grateful to M. S. Gabriela Cabrera-Valladares for teaching the isolation of islets. We thank Lidia Martinez-Perez for the islet transfection experiments. We also thank Dr. Maria Eugenia Torres and Dr. Martha Robles for their helpful discussions.


   Footnotes
 
1 This work was supported by Grant DGAPA IN210894, Grant UC Mexus (to C.F.-M. and M.S.G.), and NIH Grant RO1-DK-48281 (to M.S.G.). Back

Received September 13, 2000.


   References
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 References
 

  1. Weinhouse S 1976 Regulation of glucokinase in liver. Curr Top Cell Regul 11:1–50[Medline]
  2. Bedoya FJ, Matschinsky FM, Shimizu T, O’Neil JJ, Appel MC 1986 Differential regulation of glucokinase activity in pancreatic islet and liver in the rat. J Biol Chem 261:10760–10764[Abstract/Free Full Text]
  3. Jetton TL, Liang Y, Pettepher CC, Zimmerman EC, Cox FG, Horvath K, Matschinsky FM, Magnuson MA 1994 Analysis of upstream glucokinase promoter activity in transgenic mice and identification of glucokinase in rare neuroendocrine cells in brain and gut. J Biol Chem 269:3641–3654[Abstract/Free Full Text]
  4. Linch RM, Tompkins LS, Brooks HL, Dunn-Meynell AA, Levin BE 2000 Localization of glucokinase expression in the rat brain. Diabetes 49:693–700[Abstract]
  5. Roncero I, Alvarez E, Vazquez P, Blazquez E 2000 Functional glucokinase forms are expressed in rat brain. J Neurochem 74:1848–1857[CrossRef][Medline]
  6. Meglasson MD, Matschinsky FM 1986 Pancreatic islet glucose metabolism and regulation of insulin secretion. Diabetes Metab Rev 2:163–214[Medline]
  7. Matschinsky FM 1996 A lesson in metabolic regulation inspired by the glucokinase glucose sensor paradigm. Diabetes 45:223–242[Abstract]
  8. Granner D, Pilkis S 1990 The genes of hepatic glucose metabolism. J Biol Chem 265:10173–10176[Free Full Text]
  9. Ferre T, Riu E, Bosch F, Valera A 1996 Evidence from transgenic mice that glucokinase is rate limiting for glucose utilization in the liver. FASEB J 10:213–1218
  10. Velho G, Frogel P, Clement K, Pueyo ME, Rakotoambinina B, Zouali H, Passa P, Cohen D, Robert JJ 1992 Primary pancreatic ß-cell defect caused by mutations in glucokinase gene in kindreds of maturity onset diabetes of the young. Lancet 340:444–448[CrossRef][Medline]
  11. Glaser B, Kesevan P, Heyman M, Davis E, Cuesta A, Buchs A, Stanley CA, Thornton PS, Permutt MA, Matschinsky FM, Herold KC 1998 Familial hyperglycemia caused by an activating glucokinase mutation. N Engl J. Med 338:226–230[Free Full Text]
  12. Magnuson MA, Shelton KD 1989 An alternate promoter in the glucokinase gene is active in the pancreatic ß cell. J Biol Chem 264:15936–15942[Abstract/Free Full Text]
  13. Magnuson MA 1990 Glucokinase gene structure. Functional implications of molecular genetic studies. Diabetes 39:523–527[Abstract]
  14. Iynedjian PB, Pilot PR, Nouspikel T, Milburn JL, Quaade C, Hughes S, Ucla C, Newgard CB 1989 Differential expression and regulation of the glucokinase gene in liver and islets of Langerhans. Proc Natl Acad Sci USA 86:7838–7842[Abstract/Free Full Text]
  15. Sibrowski W, Seitz HJ 1984 Rapid action of insulin and cyclic AMP in the regulation of functional messenger RNA coding for glucokinase in rat liver. J Biol Chem 259:343–346[Abstract/Free Full Text]
  16. Magnuson MA, Andreone TL, Printz RL, Koch S, Granner DK 1989 Rat glucokinase gene: structure and regulation by insulin. Proc Natl Acad Sci USA 86:4838–4842[Abstract/Free Full Text]
  17. Iynedjian PB, Jotterand D, Nouspikel T, Asfari M, Pilot PR 1989 Transcriptional induction of glucokinase gene by insulin in cultured liver cells and its repression by the glucagon-cAMP system. J Biol Chem 264:21824–21829[Abstract/Free Full Text]
  18. Burch TP, Trus MD, Berner DK, Leontire A, Zawalich KC, Matschinsky FM 1981 Adaptation of glycolytic enzymes. Glucose use and insulin release in rat pancreatic islets during fasting and refeeding. Diabetes 30:923–928[Abstract]
  19. Liang Y, Najafi H, Smith RM, Zimmerman EC, Magnuson MA, Tal M, Matschinsky FM 1992 Concordant glucose induction of glucokinase, glucose usage, and glucose-stimulated insulin release in pancreatic islets maintained in organ culture. Diabetes 41:792–806[Abstract]
  20. Fernández-Mejía C, Davison MB 1992 Regulation of glucokinase and proinsulin gene expression and insulin secretion in RIN-m5F cells by dexamethasone, retinoic acid and thyroid hormones. Endocrinology 120:1660–1668
  21. Cabrera-Valladares G, German MS, Matschinsky FM, Wang J, Fernandez-Mejia C 1999 Effect of retinoic acid on glucokinase activity and gene expression in primary cultures of pancreatic islets. Endocrinology 140:3091–3096[Abstract/Free Full Text]
  22. Romero-Navarro G, Cabrera-Valladares G, German MS, Matschinsky FM, Wang J, Fernandez-Mejia C 1999 Biotin regulation of pancreatic glucokinase and insulin in primary cultured rat islets and in biotin deficient rats. Endocrinology 140:4595–4600[Abstract/Free Full Text]
  23. Seitz HJ 1979 Regulation of rat liver glucokinase activity in vivo: predominant role of hepatic cAMP and glucocorticoids. Arch Biochem Biophys 195:348–391
  24. Sharp GWG 1979 The adenylate cyclase-cyclic AMP system in islets of Langerhans and its role in the control of insulin release. Diabetologia 16:287–297[CrossRef][Medline]
  25. Prentki M, Matschinsky FM 1987 Ca2+, cAMP and phospholipid-derived messengers in coupling mechanisms for insulin secretion. Physiol Rev 67:1185–1248[Free Full Text]
  26. Hughes SJ, Ashcroft SJH 1992 Cyclic AMP, protein phosphorylation and insulin secretion. In: Flatt PR (ed) Nutrient Regulation of Insulin Secretion. Portland Press, Cambridge, UK, pp 271–288
  27. German MS, Moss LM, Rutter WJ 1990 Regulation of insulin gene expression by glucose and calcium in transfected primary islet cultures. J Biol Chem 265:22063–22066[Abstract/Free Full Text]
  28. Walker DG, Parry MJ 1966 Glucokinase. In: Colowick SP, Kaplan NO (eds) Methods in Enzymology. Academic Press. New York and London, vol 9: 381–383
  29. Bradford MM 1976 A rapid sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein dye binding. Anal Biochem 72:248–254[CrossRef][Medline]
  30. Wang J, Shen L, Najafi H, Kolberg J, Matschinsky FM, Urdea M, German M 1997 Regulation of insulin preRNA splicing by glucose. Proc Natl Acad Sci USA 94:4360–4365[Abstract/Free Full Text]
  31. German MS, Wang J 1994 The insulin gene contains multiple transcriptional elements that respond to glucose. Mol Cell Biol 14:4067–4075[Abstract/Free Full Text]
  32. Shelton KD, Franklin AJ, Khoor A, Beechem J, Magnuson MA 1992 Multiple elements in upstream glucokinase contribute to transcription in insulin cells. Mol Cell Biol 12:4578–4589[Abstract/Free Full Text]
  33. German MS, Moss LM, Rutter WJ 1990 Regulation of insulin gene expression by glucose and calcium in transfected primary islet cultures. J Biol Chem 265:22063–22066
  34. Tu J, Tuch BE 1996 Glucose regulates the maximal velocities of glucokinase and glucose utilization in the mature fetal rat pancreatic islet. Diabetes 45:1068–1075[Abstract]
  35. Hinata S, Nishi S, Matsukage T, Ichiyama A, Yoshimi T 1994 Regulation of glucokinase gene expresssion in cultured rat islets: the inhibitory effect of T3 and glucagon, and the stimulatory effect of glibenclamide. Diabetes Res 26:13–23[Medline]
  36. Spence JT, Pitot HC 1979 Hormonal regulation of glucokinase in primary cultures of adult rat hepatocytes. J Biol Chem 254:123331–12336
  37. Sibrowski W, Mueller MJ, Seitz HJ 1981 Effect of different thyroid states on rat liver glucokinase synthesis and degradation in vivo. J Biol Chem 256:9490–9494[Abstract/Free Full Text]
  38. Hoppner W, Seitz HJ 1989 Effect of thyroid hormones on glucokinase gene transcription in rat liver. J Biol Chem 264:20643–20647[Abstract/Free Full Text]
  39. Walker DG, Holland G 1965 The development of hepatic glucokinase in the neonatal rat. Biochem J 97:845–854[Medline]
  40. Jamdar SC, Greengard O 1970 Premature formation of glucokinase in developing rat liver. J Biol Chem 258:9143–9146[Abstract/Free Full Text]
  41. Eddlestone GT, Oldham SB, Lipson LG, Premdas FH, Begeilman PM 1985 Electrical activity, cAMP concentration, and insulin release in mouse islets of Langerhans Am J Physiol 248:C145–C153
  42. Yaekura K, Kakei M, Yada T 1996 cAMP-signaling pathway acts in selective synergism with glucose or tolbutamide to increase cytosolic Ca++ in rat pancreatic ß-cells. Diabetes 45:295–301[Abstract]
  43. Rajan AS, Hill RS, Boyd AE 1989 Effect of rise in cAMP levels on Ca++ influx through voltage-dependent Ca channels in HIT cells. Diabetes 38:874–880[Abstract]
  44. Gromada J, Bokvist K, Ding W-G, Holst JJ, Nielsen JH, Rorsman P 1998 Glucagon-like peptide (7–36) amide stimulates exocytosis in human pancreatic ß cells by both proximal and distal regulatory steps in stimulus-secretion coupling. Diabetes 47:57–65[Abstract]
  45. Ammala C, Ashcroft FM, Rorsman P 1993 Calcium-independent potentiation of insulin release by cAMP in single ß-cells. Nature 363:356–358[CrossRef][Medline]
  46. Hughes SJ, Chalk JG, Ashcroft SJH 1989 Effect of secretagogues on cytosolic free calcium and insulin release at different extracellular ca concentrations in the hamster clonal ß-cell line HIT-T15. Mol Cell Endocrinol 65:35–41[CrossRef][Medline]



This article has been cited by other articles:


Home page
 J EndocrinolHome page
A. J Weinhaus, L. E Stout, N. V Bhagroo, T C. Brelje, and R. L Sorenson
Regulation of glucokinase in pancreatic islets by prolactin: a mechanism for increasing glucose-stimulated insulin secretion during pregnancy
J. Endocrinol., June 1, 2007; 193(3): 367 - 381.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Physiol. Endocrinol. Metab.Home page
J. Shao, L. Qiao, and J. E. Friedman
Prolactin, progesterone, and dexamethasone coordinately and adversely regulate glucokinase and cAMP/PDE cascades in MIN6 {beta}-cells
Am J Physiol Endocrinol Metab, February 1, 2004; 286(2): E304 - E310.
[Abstract] [Full Text] [PDF]

Home page
 DiabetesHome page
F. M. Matschinsky
Regulation of Pancreatic {beta}-Cell Glucokinase: From Basics to Therapeutics
Diabetes, December 1, 2002; 51(90003): S394 - 404.
[Abstract] [Full Text] [PDF]

Home page
 J. Biol. Chem.Home page
M. A. Rizzo, M. A. Magnuson, P. F. Drain, and D. W. Piston
A Functional Link between Glucokinase Binding to Insulin Granules and Conformational Alterations in Response to Glucose and Insulin
J. Biol. Chem., September 6, 2002; 277(37): 34168 - 34175.
[Abstract] [Full Text] [PDF]

Home page
 DiabetesHome page
H.-i. Kim, J.-Y. Cha, S.-Y. Kim, J.-w. Kim, K. J. Roh, J.-K. Seong, N. T. Lee, K.-Y. Choi, K.-S. Kim, and Y.-h. Ahn
Peroxisomal Proliferator-Activated Receptor-{gamma} Upregulates Glucokinase Gene Expression in {beta}-Cells
Diabetes, March 1, 2002; 51(3): 676 - 685.
[Abstract] [Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Purchase Article
Right arrow View Shopping Cart
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow Request Copyright Permission
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Fernandez-Mejia, C.
Right arrow Articles by German, M. S.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Fernandez-Mejia, C.
Right arrow Articles by German, M. S.

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Endocrinology Endocrine Reviews J. Clin. End. & Metab.
Molecular Endocrinology Recent Prog. Horm. Res. All Endocrine Journals