1
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Dai T, Yang Y, Zhang J, Ma X, Chen L, Zhang C, Lv S, Li L, Tang R, Zhen N, Lu W, Li C, Hu R, Xiao Y, Dong Z. GCK exonic mutations induce abnormal biochemical activities and result in GCK-MODY. Front Genet 2023; 14:1120153. [PMID: 37082200 PMCID: PMC10110986 DOI: 10.3389/fgene.2023.1120153] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Accepted: 03/21/2023] [Indexed: 04/07/2023] Open
Abstract
Objective: Glucokinase-maturity-onset diabetes of the young (GCK-MODY; MODY2) is a rare genetic disorder caused by mutations in the glucokinase (GCK) gene. It is often under- or misdiagnosed in clinical practice, but correct diagnosis can be facilitated by genetic testing. In this study, we examined the genes of three patients diagnosed with GCK-MODY and tested their biochemical properties, such as protein stability and half-life, to explore the function of the mutant proteins and identify the pathogenic mechanism of GCK-MODY.Methods: Three patients with increased blood glucose levels were diagnosed with MODY2 according to the diagnostic guidelines of GCK-MODY proposed by the International Society for Pediatric and Adolescent Diabetes (ISPAD) in 2018. Next-generation sequencing (whole exome detection) was performed to detect gene mutations. The GCK gene and its mutations were introduced into the pCDNA3.0 and pGEX-4T-1 vectors. Following protein purification, enzyme activity assay, and protein immunoblotting, the enzyme activity of GCK was determined, along with the ubiquitination level of the mutant GCK protein.Results: Genetic testing revealed three mutations in the GCK gene of the three patients, including c.574C>T (p.R192W), c.758G>A (p.C253Y), and c.794G>A (p.G265D). The biochemical characteristics of the protein encoded by wild-type GCK and mutant GCK were different, compared to wild-type GCK, the enzyme activity encoded by the mutant GCK was reduced, suggesting thermal instability of the mutant GST-GCK. The protein stability and expression levels of the mutant GCK were reduced, and the enzyme activity of GCK was negatively correlated with the levels of fasting blood glucose and HbA1c. In addition, ubiquitination of the mutant GCK protein was higher than that of the wild-type, suggesting a higher degradation rate of mutant GCK than WT-GCK.Conclusion:GCK mutations lead to changes in the biochemical characteristics of its encoded proteins. The enzyme activities, protein expression, and protein stability of GCK may be reduced in patients with GCK gene mutations, which further causes glucose metabolism disorders and induces MODY2.
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Affiliation(s)
- Tongtong Dai
- Department of Pediatrics, Ruijin Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Yun Yang
- School of Medicine, Guizhou University, Guiyang, China
| | - Juanjuan Zhang
- Department of Pediatrics, Ruijin Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Xiaoyu Ma
- Department of Pediatrics, Ruijin Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Lifen Chen
- Department of Pediatrics, Ruijin Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Caiping Zhang
- Department of Pediatrics, Ruijin Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Sheng Lv
- Department of Pediatrics, Ruijin Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Lin Li
- Department of Pediatrics, Ruijin Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Renqiao Tang
- Department of Pediatrics, Ruijin Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Ni Zhen
- Department of Pediatrics, Ruijin Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Wenli Lu
- Department of Pediatrics, Ruijin Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Chuanyin Li
- Cancer Center, Shanghai Tenth People's Hospital, School of Medicine, Tongji University, Shanghai, China
| | - Ronggui Hu
- State Key Laboratory of Molecular Biology, Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, Shanghai, China
| | - Yuan Xiao
- Department of Pediatrics, Ruijin Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Zhiya Dong
- Department of Pediatrics, Ruijin Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
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2
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Goodarzi P, Habibi M, Roberts K, Sutton J, Shili CN, Lin D, Pezeshki A. Dietary Tryptophan Supplementation Alters Fat and Glucose Metabolism in a Low-Birthweight Piglet Model. Nutrients 2021; 13:2561. [PMID: 34444719 PMCID: PMC8399558 DOI: 10.3390/nu13082561] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2021] [Revised: 07/10/2021] [Accepted: 07/21/2021] [Indexed: 12/21/2022] Open
Abstract
Low birthweight (LBW) is associated with metabolic complications, such as glucose and lipid metabolism disturbances in early life. The objective of this study was to assess: (1) the effect of dietary tryptophan (Trp) on glucose and fat metabolism in an LBW piglet model, and (2) the role peripheral 5-hydroxytryptamine type 3 (5HT3) receptors in regulating the feeding behavior in LBW piglets fed with Trp-supplemented diets. Seven-day-old piglets were assigned to 4 treatments: normal birthweight-0%Trp (NBW-T0), LBW-0%Trp (LBW-T0), LBW-0.4%Trp (LBW-T0.4), and LBW-0.8%Trp (LBW-T0.8) for 3 weeks. Compared to LBW-T0, the blood glucose was decreased in LBW-T0.8 at 60 min following the meal test, and the triglycerides were lower in LBW-T0.4 and LBW-T0.8. Relative to LBW-T0, LBW-T0.8 had a lower transcript and protein abundance of hepatic glucose transporter-2, a higher mRNA abundance of glucokinase, and a lower transcript of phosphoenolpyruvate carboxykinase. LBW-T0.4 tended to have a lower protein abundance of sodium-glucose co-transporter 1 in the jejunum. In comparison with LBW-T0, LBW-T0.4 and LBW-T0.8 had a lower transcript of hepatic acetyl-CoA carboxylase, and LBW-T0.4 had a higher transcript of 3-hydroxyacyl-CoA dehydrogenase. Blocking 5-HT3 receptors with ondansetron reduced the feed intake in all groups, with a transient effect on LBW-T0, but more persistent effect on LBW-T0.8 and NBW-T0. In conclusion, Trp supplementation reduced the hepatic lipogenesis and gluconeogenesis, but increased the glycolysis in LBW piglets. Peripheral serotonin is likely involved in the regulation of feeding behavior, particularly in LBW piglets fed diets supplemented with a higher dose of Trp.
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Affiliation(s)
- Parniyan Goodarzi
- Department of Animal and Food Sciences, Oklahoma State University, Stillwater, OK 74078, USA; (P.G.); (M.H.); (K.R.); (J.S.); (C.N.S.)
| | - Mohammad Habibi
- Department of Animal and Food Sciences, Oklahoma State University, Stillwater, OK 74078, USA; (P.G.); (M.H.); (K.R.); (J.S.); (C.N.S.)
| | - Kennedy Roberts
- Department of Animal and Food Sciences, Oklahoma State University, Stillwater, OK 74078, USA; (P.G.); (M.H.); (K.R.); (J.S.); (C.N.S.)
| | - Julia Sutton
- Department of Animal and Food Sciences, Oklahoma State University, Stillwater, OK 74078, USA; (P.G.); (M.H.); (K.R.); (J.S.); (C.N.S.)
| | - Cedrick Ndhumba Shili
- Department of Animal and Food Sciences, Oklahoma State University, Stillwater, OK 74078, USA; (P.G.); (M.H.); (K.R.); (J.S.); (C.N.S.)
| | - Dingbo Lin
- Department of Nutritional Sciences, Oklahoma State University, Stillwater, OK 74078, USA;
| | - Adel Pezeshki
- Department of Animal and Food Sciences, Oklahoma State University, Stillwater, OK 74078, USA; (P.G.); (M.H.); (K.R.); (J.S.); (C.N.S.)
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3
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Pinaud S, Tetreau G, Poteaux P, Galinier R, Chaparro C, Lassalle D, Portet A, Simphor E, Gourbal B, Duval D. New Insights Into Biomphalysin Gene Family Diversification in the Vector Snail Biomphalaria glabrata. Front Immunol 2021; 12:635131. [PMID: 33868258 PMCID: PMC8047071 DOI: 10.3389/fimmu.2021.635131] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2020] [Accepted: 03/08/2021] [Indexed: 11/30/2022] Open
Abstract
Aerolysins initially characterized as virulence factors in bacteria are increasingly found in massive genome and transcriptome sequencing data from metazoans. Horizontal gene transfer has been demonstrated as the main way of aerolysin-related toxins acquisition in metazoans. However, only few studies have focused on their potential biological functions in such organisms. Herein, we present an extensive characterization of a multigene family encoding aerolysins - named biomphalysin - in Biomphalaria glabrata snail, the intermediate host of the trematode Schistosoma mansoni. Our results highlight that duplication and domestication of an acquired bacterial toxin gene in the snail genome result in the acquisition of a novel and diversified toxin family. Twenty-three biomphalysin genes were identified. All are expressed and exhibited a tissue-specific expression pattern. An in silico structural analysis was performed to highlight the central role played by two distinct domains i) a large lobe involved in the lytic function of these snail toxins which constrained their evolution and ii) a small lobe which is structurally variable between biomphalysin toxins and that matched to various functional domains involved in moiety recognition of targets cells. A functional approach suggests that the repertoire of biomphalysins that bind to pathogens, depends on the type of pathogen encountered. These results underline a neo-and sub-functionalization of the biomphalysin toxins, which have the potential to increase the range of effectors in the snail’s immune arsenal.
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Affiliation(s)
- Silvain Pinaud
- IHPE, Univ Montpellier, CNRS, IFREMER, Univ Perpignan Via Domitia, Perpignan, France.,CNRS, IFREMER, University of Montpellier, Perpignan, France
| | - Guillaume Tetreau
- IHPE, Univ Montpellier, CNRS, IFREMER, Univ Perpignan Via Domitia, Perpignan, France.,CNRS, IFREMER, University of Montpellier, Perpignan, France
| | - Pierre Poteaux
- IHPE, Univ Montpellier, CNRS, IFREMER, Univ Perpignan Via Domitia, Perpignan, France.,CNRS, IFREMER, University of Montpellier, Perpignan, France
| | - Richard Galinier
- IHPE, Univ Montpellier, CNRS, IFREMER, Univ Perpignan Via Domitia, Perpignan, France.,CNRS, IFREMER, University of Montpellier, Perpignan, France
| | - Cristian Chaparro
- IHPE, Univ Montpellier, CNRS, IFREMER, Univ Perpignan Via Domitia, Perpignan, France.,CNRS, IFREMER, University of Montpellier, Perpignan, France
| | - Damien Lassalle
- IHPE, Univ Montpellier, CNRS, IFREMER, Univ Perpignan Via Domitia, Perpignan, France.,CNRS, IFREMER, University of Montpellier, Perpignan, France
| | - Anaïs Portet
- IHPE, Univ Montpellier, CNRS, IFREMER, Univ Perpignan Via Domitia, Perpignan, France.,CNRS, IFREMER, University of Montpellier, Perpignan, France
| | - Elodie Simphor
- IHPE, Univ Montpellier, CNRS, IFREMER, Univ Perpignan Via Domitia, Perpignan, France.,CNRS, IFREMER, University of Montpellier, Perpignan, France
| | - Benjamin Gourbal
- IHPE, Univ Montpellier, CNRS, IFREMER, Univ Perpignan Via Domitia, Perpignan, France.,CNRS, IFREMER, University of Montpellier, Perpignan, France
| | - David Duval
- IHPE, Univ Montpellier, CNRS, IFREMER, Univ Perpignan Via Domitia, Perpignan, France.,CNRS, IFREMER, University of Montpellier, Perpignan, France
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4
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Liu W, Yao C, Shang Q, Liu Y, Liu C, Meng F. Insights into the binding of dorzagliatin with glucokinase: A molecular dynamics simulation. JOURNAL OF THEORETICAL & COMPUTATIONAL CHEMISTRY 2020. [DOI: 10.1142/s0219633620500273] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Human glucokinase (GK) is a potentially attractive target for diabetes, playing a prominent role in the control of glucose homeostasis. Dorzagliatin is the first GK activator (GKA) to enter phase III clinical trial. In this study, the possible binding mode of dorzagliatin with GK was investigated via the molecular simulation method. Two other systems in the absence of dorzagliatin and glucose were also studied to disclose the roles of dorzagliatin and glucose. The outcomes revealed that dorzagliatin can create the characteristic hydrogen bonds of GKA with Arg63, and Arg63 can form hydrogen bonds with nearby residues, making a tight binding hydrogen bond network around dorzagliatin. The presence of dorzagliatin can stabilize glucokinase for a period of time, and the binding of glucose may prevent the GK conformational change to a certain extent. Our results may be beneficial to mechanism understanding of GKA, and will be useful in design of novel GKAs for treating metabolic diseases.
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Affiliation(s)
- Wei Liu
- Tianjin Key Laboratory of Molecular, Design and Drug Discovery, Tianjin Institute of Pharmaceutical Research, Tianjin 300301, P. R. China
| | - Chenhui Yao
- Tianjin Key Laboratory of Molecular, Design and Drug Discovery, Tianjin Institute of Pharmaceutical Research, Tianjin 300301, P. R. China
| | - Qian Shang
- Tianjin Key Laboratory of Molecular, Design and Drug Discovery, Tianjin Institute of Pharmaceutical Research, Tianjin 300301, P. R. China
| | - Yuqiang Liu
- Tianjin Key Laboratory of Molecular, Design and Drug Discovery, Tianjin Institute of Pharmaceutical Research, Tianjin 300301, P. R. China
| | - Changying Liu
- Tianjin Key Laboratory of Molecular, Design and Drug Discovery, Tianjin Institute of Pharmaceutical Research, Tianjin 300301, P. R. China
| | - Fancui Meng
- Tianjin Key Laboratory of Molecular, Design and Drug Discovery, Tianjin Institute of Pharmaceutical Research, Tianjin 300301, P. R. China
- State Key Laboratory of Drug Delivery Technology and Pharmacokinetics, Tianjin Institute of Pharmaceutical Research, Tianjin 300301, P. R. China
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5
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Sternisha SM, Whittington AC, Martinez Fiesco JA, Porter C, McCray MM, Logan T, Olivieri C, Veglia G, Steinbach PJ, Miller BG. Nanosecond-Timescale Dynamics and Conformational Heterogeneity in Human GCK Regulation and Disease. Biophys J 2020; 118:1109-1118. [PMID: 32023434 DOI: 10.1016/j.bpj.2019.12.036] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Revised: 12/11/2019] [Accepted: 12/19/2019] [Indexed: 11/25/2022] Open
Abstract
Human glucokinase (GCK) is the prototypic example of an emerging class of proteins with allosteric-like behavior that originates from intrinsic polypeptide dynamics. High-resolution NMR investigations of GCK have elucidated millisecond-timescale dynamics underlying allostery. In contrast, faster motions have remained underexplored, hindering the development of a comprehensive model of cooperativity. Here, we map nanosecond-timescale dynamics and structural heterogeneity in GCK using a combination of unnatural amino acid incorporation, time-resolved fluorescence, and 19F nuclear magnetic resonance spectroscopy. We find that a probe inserted within the enzyme's intrinsically disordered loop samples multiple conformations in the unliganded state. Glucose binding and disease-associated mutations that suppress cooperativity alter the number and/or relative population of these states. Together, the nanosecond kinetics characterized here and the millisecond motions known to be essential for cooperativity provide a dynamical framework with which we address the origins of cooperativity and the mechanism of activated, hyperinsulinemia-associated, noncooperative variants.
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Affiliation(s)
- Shawn M Sternisha
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida
| | - A Carl Whittington
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida; Department of Biological Science, Florida State University, Tallahassee, Florida
| | | | - Carol Porter
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida
| | - Malcolm M McCray
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida
| | - Timothy Logan
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida; Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida
| | - Cristina Olivieri
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota
| | - Gianluigi Veglia
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota; Department of Chemistry, University of Minnesota, Minneapolis, Minnesota
| | - Peter J Steinbach
- Center for Molecular Modeling, Center for Information Technology, National Institutes of Health, Bethesda, Maryland.
| | - Brian G Miller
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida.
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6
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Ermakova E, Kurbanov R. Molecular insight into conformational transformation of human glucokinase: conventional and targeted molecular dynamics. J Biomol Struct Dyn 2019; 38:3035-3045. [PMID: 31379266 DOI: 10.1080/07391102.2019.1652689] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Glucokinase (GK) plays a key role in the regulation of hepatic glucose metabolism. An unusual mechanism of positive cooperativity of monomeric GK containing only a single binding site for glucose is very interesting and still unclear. The activation process of GK is associated with a large-scale conformational change from the inactive to the active state. Here, conventional and targeted molecular dynamics simulations were used to study the conformational dynamics of GK in the stable configurations and in the transition from active to inactive state. Three phases of the structural reorganization of GK were detected. The first step is a transformation of GK from the active state to the intermediate structure, where the cleft between the domains is open, but alpha helix 13 is still inside the small domain. From this point, there are two alternative paths. One path leads to the inactive state through the release of helix 13 from the inside of small domain to the outside. Other path goes back to the active state. Simulation results reveal the critical role of helix 13 in the transformation of GK from the open state to inactive one and the influence of the loop 2 on the protein transformation between the open and the closed active states. Principal component analysis and covariance matrix analysis were carried out to analyze the dynamics of protein. Importance of hydrogen bonds in the stability of the closed conformation is shown. Overall, our simulations provide new information about the dynamics of GK and its structural transformation.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Elena Ermakova
- Kazan Institute of Biochemistry and Biophysics, FRC Kazan Scientific Center of RAS, Kazan, Russia
| | - Rauf Kurbanov
- Kazan Institute of Biochemistry and Biophysics, FRC Kazan Scientific Center of RAS, Kazan, Russia
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7
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Langer S, Hofmeister-Brix A, Waterstradt R, Baltrusch S. 6-Phosphofructo-2-kinase/fructose-2,6-bisphosphatase and small chemical activators affect enzyme activity of activating glucokinase mutants by distinct mechanisms. Biochem Pharmacol 2019; 168:149-161. [PMID: 31254492 DOI: 10.1016/j.bcp.2019.06.024] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Accepted: 06/24/2019] [Indexed: 11/17/2022]
Abstract
Glucokinase (GK), a monomeric glucose-phosphorylating enzyme characterised by high structural flexibility, acts as a glucose sensor in pancreatic beta cells and liver. Pharmaceutical efforts to control the enzyme are hampered by an incomplete understanding of GK regulation. We investigated GK characteristics of wild-type and activating S64Y and G68V mutant proteins in the presence of various combinations of the synthetic activators RO-28-1675 and compound A, the endogenous activator fructose-2,6-bisphosphatase (FBPase-2), and the inhibitor mannoheptulose. S64Y impedes formation of a turn structure that is characteristic for the inactive enzyme conformation, and complex formation with compound A induces collision with the large domain. G68V evokes close contact of connecting region I and helix α13 with RO-28-1675 and compound A. Both mutants showed higher activity than the wild-type at low glucose and were susceptible to further activation by FBPase-2 and RO-28-1675, alone and additively. G68V was less active than S64Y, but was activatable by compound A. In contrast, compound A inhibited S64Y, and this effect was even more pronounced in combination with mannoheptulose. Mutant and wild-type GK showed comparable thermal stability and intracellular lifetimes. A GK-6-phosphofructo-2-kinase (PFK-2)/FBPase-2 complex predicted by in silico protein-protein docking demonstrated possible binding of the FBPase-2 domain near the active site of GK. In summary, activating mutations within the allosteric site of GK do not preclude binding of chemical activators (GKAs), but can alter their action into inhibition. Our postulated GK-PFK-2/FBPase-2 complex represents the endogenous principle of activation by substrate channelling which permits binding of other small molecules and proteins.
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Affiliation(s)
- Sara Langer
- Institute of Medical Biochemistry and Molecular Biology, University Medicine, University of Rostock, 18057 Rostock, Germany
| | - Anke Hofmeister-Brix
- Institute of Medical Biochemistry and Molecular Biology, University Medicine, University of Rostock, 18057 Rostock, Germany; Institute of Clinical Biochemistry, Hannover Medical School, 30623 Hannover, Germany
| | - Rica Waterstradt
- Institute of Medical Biochemistry and Molecular Biology, University Medicine, University of Rostock, 18057 Rostock, Germany
| | - Simone Baltrusch
- Institute of Medical Biochemistry and Molecular Biology, University Medicine, University of Rostock, 18057 Rostock, Germany; Department Life, Light & Matter, University of Rostock, Germany.
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8
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Zelent B, Bialas C, Gryczynski I, Chen P, Chib R, Lewerissa K, Corradini MG, Ludescher RD, Vanderkooi JM, Matschinsky FM. Tryptophan Fluorescence Yields and Lifetimes as a Probe of Conformational Changes in Human Glucokinase. J Fluoresc 2017; 27:1621-1631. [PMID: 28432632 PMCID: PMC6025808 DOI: 10.1007/s10895-017-2099-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2017] [Accepted: 04/04/2017] [Indexed: 10/19/2022]
Abstract
Five variants of glucokinase (ATP-D-hexose-6-phosphotransferase, EC 2.7.1.1) including wild type and single Trp mutants with the Trp residue at positions 65, 99, 167 and 257 were prepared. The fluorescence of Trp in all locations studied showed intensity changes when glucose bound, indicating that conformational change occurs globally over the entire protein. While the fluorescence quantum yield changes upon glucose binding, the enzyme's absorption spectra, emission spectra and fluorescence lifetimes change very little. These results are consistent with the existence of a dark complex for excited state Trp. Addition of glycerol, L-glucose, sucrose, or trehalose increases the binding affinity of glucose to the enzyme and increases fluorescence intensity. The effect of these osmolytes is thought to shift the protein conformation to a condensed, high affinity form. Based upon these results, we consider the nature of quenching of the Trp excited state. Amide groups are known to quench indole fluorescence and amides of the polypeptide chain make interact with excited state Trp in the relatively unstructured, glucose-free enzyme. Also, removal of water around the aromatic ring by addition of glucose substrate or osmolyte may reduce the quenching.
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Affiliation(s)
- Bogumil Zelent
- Department of Biochemistry and Biophysics and Diabetes Research Center, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA.
- Department of Food Science, Rutgers, The State University of New Jersey, New Brunswick, NJ, USA.
| | - Chris Bialas
- Johnson Research Foundation, Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Ignacy Gryczynski
- Department of Cell Biology and Immunology, Center for Fluorescence Technologies and Nanomedicine, University of North Texas Health Science Center, Fort Worth, TX, USA
| | - Pan Chen
- Department of Biochemistry and Biophysics and Diabetes Research Center, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Rahul Chib
- Department of Food Science, Rutgers, The State University of New Jersey, New Brunswick, NJ, USA
| | - Karina Lewerissa
- Department of Food Science, Rutgers, The State University of New Jersey, New Brunswick, NJ, USA
| | - Maria G Corradini
- Department of Food Science, Rutgers, The State University of New Jersey, New Brunswick, NJ, USA
- Department of Food Science, University of Massachusetts Amherst, Massachusetts, MA, USA
| | - Richard D Ludescher
- Department of Food Science, Rutgers, The State University of New Jersey, New Brunswick, NJ, USA
| | - Jane M Vanderkooi
- Johnson Research Foundation, Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Franz M Matschinsky
- Department of Biochemistry and Biophysics and Diabetes Research Center, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA.
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9
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Chaudhury S, Bag S, Bose M, Das AK, Ghosh AK, Dasgupta S. Protection of human γB-crystallin from UV-induced damage by epigallocatechin gallate: spectroscopic and docking studies. MOLECULAR BIOSYSTEMS 2017; 12:2901-9. [PMID: 27410057 DOI: 10.1039/c6mb00256k] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The transparency of the human eye lens depends on the solubility and stability of the structural proteins of the eye lens, the crystallins. Although the mechanism of cataract formation is still unclear, it is believed to involve protein misfolding and/or aggregation of proteins due to the influence of several external factors such as ultraviolet (UV) radiation, low pH, temperature and exposure to chemical agents. In this article, we report the study of UV induced photo-damage (under oxidative stress) of recombinant human γB-crystallin in vitro in the presence of the major green tea polyphenol, (-)-epigallocatechin gallate (EGCG). We have shown that EGCG has the ability to protect human γB-crystallin from oxidative stress-induced photo-damage.
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Affiliation(s)
| | - Sudipta Bag
- Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur 721302, India.
| | - Madhuparna Bose
- Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur 721302, India
| | - Amit Kumar Das
- Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur 721302, India
| | - Ananta Kumar Ghosh
- Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur 721302, India
| | - Swagata Dasgupta
- Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur 721302, India.
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10
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Martínez R, Gutierrez-Nogués Á, Fernández-Ramos C, Velayos T, Vela A, Navas MÁ, Castaño L. Heterogeneity in phenotype of hyperinsulinism caused by activating glucokinase mutations: a novel mutation and its functional characterization. Clin Endocrinol (Oxf) 2017; 86:778-783. [PMID: 28247534 DOI: 10.1111/cen.13318] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Revised: 12/12/2016] [Accepted: 02/23/2017] [Indexed: 12/11/2022]
Abstract
BACKGROUND Mutations in the GCK gene lead to different forms of glucokinase (GCK)-disease, activating mutations cause hyperinsulinaemic hypoglycaemia while inactivating mutations cause monogenic diabetes. Hyperinsulinism (HI) is a heterogeneous condition with a significant genetic component. The major causes are channelopathies, the other forms are rare and being caused by mutations in genes such as GCK. OBJECTIVE To describe the clinical and genetic presentation of four families with activating GCK mutations, and to explore the pathogenicity of the novel mutation identified through functional studies. RESULTS Four cases of HI with mutations in GCK were identified. These include one novel mutation (p.Trp99Cys). Functional analysis of the purified mutant fusion protein glutathione-S-transferase (GST)-GCK-p.Trp99Cys demonstrated that p.Trp99Cys is an activating mutation as it induces a higher affinity for glucose and increases the relative activity index more than 11 times. Moreover, the thermal stability of the mutant protein was similar to that of its wild type. All patients were responsive to diazoxide treatment. One of the mutations arose de novo, and two were dominantly inherited, although only one of them from an HI affected parent. The age of presentation in our cases varied widely from the neonatal period to adulthood. CONCLUSION The clinical phenotype of the GCK activating mutation carriers was heterogeneous, the severity of symptoms and age at presentation varied markedly between affected individuals, even within the same family. The novel activating GCK mutation (p.Trp99Cys) has a strong activating effect in vitro although it has been identified in one case of a milder and late-onset form of HI.
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Affiliation(s)
- Rosa Martínez
- Endocrinology and Diabetes Research Group, BioCruces Health Research Institute, UPV-EHU, CIBERDEM, CIBERER, Cruces University Hospital, Barakaldo, Spain
| | - Ángel Gutierrez-Nogués
- Department of Biochemistry and Molecular Biology III, Faculty of Medicine, CIBERDEM and Hospital Clínico San Carlos Health Research Institute, Complutense University of Madrid, Madrid, Spain
| | - Concepción Fernández-Ramos
- Pediatric Endocrinology Section, BioCruces Health Research Institute, UPV/EHU, Basurto University Hospital, Bilbao, Spain
| | - Teresa Velayos
- Endocrinology and Diabetes Research Group, BioCruces Health Research Institute, UPV-EHU, CIBERDEM, CIBERER, Cruces University Hospital, Barakaldo, Spain
| | - Amaia Vela
- Pediatric Endocrinology Section, BioCruces Health Research Institute, UPV/EHU, Cruces University Hospital, CIBERDEM, CIBERER, Barakaldo, Bizkaia, Spain
| | - María-Ángeles Navas
- Department of Biochemistry and Molecular Biology III, Faculty of Medicine, CIBERDEM and Hospital Clínico San Carlos Health Research Institute, Complutense University of Madrid, Madrid, Spain
| | - Luis Castaño
- Endocrinology and Diabetes Research Group, BioCruces Health Research Institute, UPV-EHU, CIBERDEM, CIBERER, Cruces University Hospital, Barakaldo, Spain
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11
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19F nuclear magnetic resonance screening of glucokinase activators. Anal Biochem 2015; 477:62-8. [DOI: 10.1016/j.ab.2015.02.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2014] [Revised: 01/29/2015] [Accepted: 02/04/2015] [Indexed: 11/20/2022]
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12
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Analysis of the co-operative interaction between the allosterically regulated proteins GK and GKRP using tryptophan fluorescence. Biochem J 2014; 459:551-64. [PMID: 24568320 PMCID: PMC4109836 DOI: 10.1042/bj20131363] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Hepatic glucose phosphorylation by GK (glucokinase) is regulated by GKRP (GK regulatory protein). GKRP forms a cytosolic complex with GK followed by nuclear import and storage, leading to inhibition of GK activity. This process is initiated by low glucose, but reversed nutritionally by high glucose and fructose or pharmacologically by GKAs (GK activators) and GKRPIs (GKRP inhibitors). To study the regulation of this process by glucose, fructose-phosphate esters and a GKA, we measured the TF (tryptophan fluorescence) of human WT (wild-type) and GKRP-P446L (a mutation associated with high serum triacylglycerol) in the presence of non-fluorescent GK with its tryptophan residues mutated. Titration of GKRP-WT by GK resulted in a sigmoidal increase in TF, suggesting co-operative PPIs (protein-protein interactions) perhaps due to the hysteretic nature of GK. The affinity of GK for GKRP was decreased and binding co-operativity increased by glucose, fructose 1-phosphate and GKA, reflecting disruption of the GK-GKRP complex. Similar studies with GKRP-P446L showed significantly different results compared with GKRP-WT, suggesting impairment of complex formation and nuclear storage. The results of the present TF-based biophysical analysis of PPIs between GK and GKRP suggest that hepatic glucose metabolism is regulated by a metabolite-sensitive drug-responsive co-operative molecular switch, involving complex formation between these two allosterically regulated proteins.
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13
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Conformational transition pathway in the activation process of allosteric glucokinase. PLoS One 2013; 8:e55857. [PMID: 23409066 PMCID: PMC3567010 DOI: 10.1371/journal.pone.0055857] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2012] [Accepted: 01/03/2013] [Indexed: 12/11/2022] Open
Abstract
Glucokinase (GK) is a glycolytic enzyme that plays an important role in regulating blood glucose level, thus acting as a potentially attractive target for drug discovery in the treatment of diabetes of the young type 2 and persistent hyperinsulinemic hypoglycemia of infancy. To characterize the activation mechanism of GK from the super-open state (inactive state) to the closed state (active state), a series of conventional molecular dynamics (MD) and targeted MD (TMD) simulations were performed on this enzyme. Conventional MD simulation showed a specific conformational ensemble of GK when the enzyme is inactive. Seven TMD simulations depicted a reliably conformational transition pathway of GK from the inactive state to the active state, and the components important to the conformational change of GK were identified by analyzing the detailed structures of the TMD trajectories. In combination with the inactivation process, our findings showed that the whole conformational pathway for the activation-inactivation-activation of GK is a one-direction circulation, and the active state is less stable than the inactive state in the circulation. Additionally, glucose was demonstrated to gradually modulate its binding pose with the help of residues in the large domain and connecting region of GK during the activation process. Furthermore, the obtained energy barriers were used to explain the preexisting equilibrium and the slow binding kinetic process of the substrate by GK. The simulated results are in accordance with the recent findings from the mutagenesis experiments and kinetic analyses. Our observations reveal a complicated conformational process in the allosteric protein, resulting in new knowledge about the delicate mechanisms for allosteric biological macromolecules that will be useful in drug design for targeting allosteric proteins.
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14
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Matschinsky FM. GKAs for diabetes therapy: why no clinically useful drug after two decades of trying? Trends Pharmacol Sci 2013; 34:90-9. [PMID: 23305809 DOI: 10.1016/j.tips.2012.11.007] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2012] [Revised: 11/29/2012] [Accepted: 11/30/2012] [Indexed: 12/17/2022]
Abstract
Results of basic biochemical and physiological research, strongly endorsed by findings in human pathophysiology and genetics, had characterized the glucose phosphorylating enzyme glucokinase as a critical player in normal glucose homeostasis, diabetes mellitus, and hyperinsulinemic hypoglycemia, and identified the enzyme as a promising new drug target. R&D initiated in the early 1990s and directed at this target discovered glucokinase activators (GKAs) as a new class of potentially antidiabetic drugs. GKAs were characterized as nonessential allosteric activators that increase glucose affinity and V(max) of the enzyme, thus stimulating glucose metabolism in glucokinase expressing tissue, of foremost functional significance in the insulin producing pancreatic beta cells and the liver. The results of preclinical testing of GKAs by many pharmaceutical companies demonstrated uniformly high hypoglycemic efficacy in normal and diabetic animals. GKAs were also highly effective in Phase I trials in patients with type 2 diabetes mellitus (T2DM). However, results of a recent Phase II trial were less encouraging because patients developed hyperlipidemia and vascular hypertension, and the drug lost efficacy within several months. This outcome is prompting a reappraisal of the GKA strategy. In this opinion article, the 'pros and cons' of the strategy to use these compounds in diabetes management are critically reexamined and suggestions are made that might facilitate progress of GKA R&D that could still result in a novel antidiabetic medicine.
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Affiliation(s)
- Franz M Matschinsky
- Department of Biochemistry and Biophysics, Institute for Diabetes, Obesity, and Metabolism, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-5160, USA.
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15
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Markwardt ML, Nkobena A, Ding SY, Rizzo MA. Association with nitric oxide synthase on insulin secretory granules regulates glucokinase protein levels. Mol Endocrinol 2012; 26:1617-29. [PMID: 22771492 PMCID: PMC3434526 DOI: 10.1210/me.2012-1183] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2012] [Accepted: 06/19/2012] [Indexed: 11/19/2022] Open
Abstract
Glucokinase (GCK) association with insulin-secretory granules is controlled by interaction with nitric oxide synthase (NOS) and is reversed by GCK S-nitrosylation. Nonetheless, the function of GCK sequestration on secretory granules is unknown. Here we report that the S-nitrosylation blocking V367M mutation prevents GCK accumulation on secretory granules by inhibiting association with NOS. Expression of this mutant is reduced compared with a second S-nitrosylation blocking GCK mutant (C371S) that accumulates to secretory granules and is expressed at levels greater than wild type. Even so, the rate of degradation for wild type and mutant GCK proteins were not significantly different from one another, and neither mutation disrupted the ability of GCK to be ubiquitinated. Furthermore, gene silencing of NOS reduced endogenous GCK content but did not affect β-actin content. Treatment of GCK(C371S) expressing cells with short interfering RNA specific for NOS also blocked accumulation of this protein to secretory granules and reduced expression levels to that of GCK(V367M). Conversely, cotransfection of catalytically inactive NOS increased GCK-mCherry levels. Expression of GCK(C371S) in βTC3 cells enhanced glucose metabolism compared with untransfected cells and cells expressing wild type GCK, even though this mutant has slightly reduced enzymatic activity in vitro. Finally, molecular dynamics simulations revealed that V367M induces conformational changes in GCK that are similar to S-nitrosylated GCK, thereby suggesting a mechanism for V367M-inhibition of NOS association. Our findings suggest that sequestration of GCK on secretory granules regulates cellular GCK protein content, and thus cellular GCK activity, by acting as a storage pool for GCK proteins.
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Affiliation(s)
- Michele L Markwardt
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA
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16
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Negahdar M, Aukrust I, Johansson BB, Molnes J, Molven A, Matschinsky FM, Søvik O, Kulkarni RN, Flatmark T, Njølstad PR, Bjørkhaug L. GCK-MODY diabetes associated with protein misfolding, cellular self-association and degradation. Biochim Biophys Acta Mol Basis Dis 2012; 1822:1705-15. [PMID: 22820548 DOI: 10.1016/j.bbadis.2012.07.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2012] [Revised: 06/17/2012] [Accepted: 07/12/2012] [Indexed: 12/31/2022]
Abstract
GCK-MODY, dominantly inherited mild fasting hyperglycemia, has been associated with >600 different mutations in the glucokinase (GK)-encoding gene (GCK). When expressed as recombinant pancreatic proteins, some mutations result in enzymes with normal/near-normal catalytic properties. The molecular mechanism(s) of GCK-MODY due to these mutations has remained elusive. Here, we aimed to explore the molecular mechanisms for two such catalytically 'normal' GCK mutations (S263P and G264S) in the F260-L270 loop of GK. When stably overexpressed in HEK293 cells and MIN6 β-cells, the S263P- and G264S-encoded mutations generated misfolded proteins with an increased rate of degradation (S263P>G264S) by the protein quality control machinery, and a propensity to self-associate (G264S>S263P) and form dimers (SDS resistant) and aggregates (partly Triton X-100 insoluble), as determined by pulse-chase experiments and subcellular fractionation. Thus, the GCK-MODY mutations S263P and G264S lead to protein misfolding causing destabilization, cellular dimerization/aggregation and enhanced rate of degradation. In silico predicted conformational changes of the F260-L270 loop structure are considered to mediate the dimerization of both mutant proteins by a domain swapping mechanism. Thus, similar properties may represent the molecular mechanisms for additional unexplained GCK-MODY mutations, and may also contribute to the disease mechanism in other previously characterized GCK-MODY inactivating mutations.
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Affiliation(s)
- Maria Negahdar
- Department of Clinical Medicine, University of Bergen, N-5020 Bergen, Norway
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17
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Zelent B, Buettger C, Grimsby J, Sarabu R, Vanderkooi JM, Wand AJ, Matschinsky FM. Thermal stability of glucokinase (GK) as influenced by the substrate glucose, an allosteric glucokinase activator drug (GKA) and the osmolytes glycerol and urea. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2012; 1824:769-84. [PMID: 22446163 DOI: 10.1016/j.bbapap.2012.03.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2011] [Revised: 02/15/2012] [Accepted: 03/05/2012] [Indexed: 11/27/2022]
Abstract
We investigated how glycerol, urea, glucose and a GKA influence kinetics and stability of wild-type and mutant GK. Glycerol and glucose stabilized GK additively. Glycerol barely affected the TF spectra of all GKs but decreased k(cat), glucose S(0.5) and K(D) values and ATP K(M) while leaving cooperativity unchanged. Glycerol sensitized all GKs to GKA as shown by TF. Glucose increased TF of GKs without influence of glycerol on the effect. Glycerol and GKA affected kinetics and binding additively. The activation energies for thermal denaturation of GK were a function of glucose with K(D)s of 3 and 1mM without and with glycerol, respectively. High urea denatured wild type GK reversibly at 20 and 60°C and urea treatment of irreversibly heat denatured GK allowed refolding as demonstrated by TF including glucose response. We concluded: Glycerol stabilizes GK indirectly without changing the folding structure of the apoenzyme, by restructuring the surface water of the protein, whereas glucose stabilizes GK directly by binding to its substrate site and inducing a compact conformation. Glucose or glycerol (alone or combined) is unable to prevent irreversible heat denaturation above 40°C. However, urea denatures GK reversibly even at 60°C by binding to the protein backbone and directly interacting with hydrophobic side chains. It prevents irreversible aggregation allowing complete refolding when urea is removed. This study establishes the foundation for exploring numerous instability mutants among the more than 600 variant GKs causing diabetes in animals and humans.
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Affiliation(s)
- B Zelent
- Department of Biochemistry and Biophysics and Diabetes Research Center, University of Pennsylvania, Philadelphia, PA 19104, USA
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18
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Larion M, Miller BG. Homotropic allosteric regulation in monomeric mammalian glucokinase. Arch Biochem Biophys 2012; 519:103-11. [PMID: 22107947 PMCID: PMC3294010 DOI: 10.1016/j.abb.2011.11.007] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2011] [Revised: 11/03/2011] [Accepted: 11/04/2011] [Indexed: 11/30/2022]
Abstract
Glucokinase catalyzes the ATP-dependent phosphorylation of glucose, a chemical transformation that represents the rate-limiting step of glycolytic metabolism in the liver and pancreas. Glucokinase is a central regulator of glucose homeostasis as evidenced by its association with two disease states, maturity onset diabetes of the young (MODY) and persistent hyperinsulinemia of infancy (PHHI). Mammalian glucokinase is subject to homotropic allosteric regulation by glucose-the steady-state velocity of glucose-6-phosphate production is not hyperbolic, but instead displays a sigmoidal response to increasing glucose concentrations. The positive cooperativity displayed by glucokinase is intriguing since the enzyme functions as a monomer under physiological conditions and contains only a single binding site for glucose. Despite the existence of several models of kinetic cooperativity in monomeric enzymes, a consensus has yet to be reached regarding the mechanism of allosteric regulation in glucokinase. Experimental evidence collected over the last 45 years by a number of investigators supports a link between cooperativity and slow conformational reorganizations of the glucokinase scaffold. In this review, we summarize advances in our understanding of glucokinase allosteric regulation resulting from recent X-ray crystallographic, pre-equilibrium kinetic and high-resolution nuclear magnetic resonance investigations. We conclude with a brief discussion of unanswered questions regarding the mechanistic basis of kinetic cooperativity in mammalian glucokinase.
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Affiliation(s)
- Mioara Larion
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306-4390, USA
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19
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Abstract
GK (glucokinase) is activated by glucose binding to its substrate site, is inhibited by GKRP (GK regulatory protein) and stimulated by GKAs (GK activator drugs). To explore further the mechanisms of these processes we studied pure recombinant human GK (normal enzyme and a selection of 31 mutants) using steady-state kinetics of the enzyme and TF (tryptophan fluorescence). TF studies of the normal binary GK-glucose complex corroborate recent crystallography studies showing that it exists in a closed conformation greatly different from the open conformation of the ligand-free structure, but indistinguishable from the ternary GK-glucose-GKA complex. GKAs did activate and GKRP did inhibit normal GK, whereas its TF was doubled by glucose saturation. However, the enzyme kinetics, GKRP inhibition, TF enhancement by glucose and responsiveness to GKA of the selected mutants varied greatly. Two predominant response patterns were identified accounting for nearly all mutants: (i) GK mutants with a normal or close to normal response to GKA, normally low basal TF (indicating an open conformation), some variability of kinetic parameters (k(cat), glucose S(0.5), h and ATP K(m)), but usually strong GKRP inhibition (13/31); and (ii) GK mutants that are refractory to GKAs, exhibit relatively high basal TF (indicating structural compaction and partial closure), usually show strongly enhanced catalytic activity primarily due to lowering of the glucose S(0.5), but with reduced or no GKRP inhibition in most cases (14/31). These results and those of previous studies are best explained by envisioning a common allosteric regulator region with spatially non-overlapping GKRP- and GKA-binding sites.
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20
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Pavlov N, Gilles P, Didierjean C, Wenger E, Naydenova E, Martinez J, Calmès M. Asymmetric Synthesis of β2-Tryptophan Analogues via Friedel–Crafts Alkylation of Indoles with a Chiral Nitroacrylate. J Org Chem 2011; 76:6116-24. [DOI: 10.1021/jo200733t] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Nikola Pavlov
- Institut des Biomolécules
Max Mousseron (IBMM) UMR 5247 CNRS-Université Montpellier 1
et Université Montpellier 2, Bâtiment Chimie (17), Université Montpellier 2, place E. Bataillon,
34095 Montpellier cedex 5, France
- Department of Organic Chemistry, University of Chemical Technology and Metallurgy, 8
Kliment Ohridski blvd., Sofia 1756, Bulgaria
| | - Pierre Gilles
- Institut des Biomolécules
Max Mousseron (IBMM) UMR 5247 CNRS-Université Montpellier 1
et Université Montpellier 2, Bâtiment Chimie (17), Université Montpellier 2, place E. Bataillon,
34095 Montpellier cedex 5, France
| | - Claude Didierjean
- Laboratoire de Crystallographie,
Résonance Magnétique et Modélisation, Nancy Université, UMR7036 CNRS-UHP, Boulevard
des Aiguillettes, BPP239, 54506 Vandoeuvre-Lès-Nancy Cedex,
France
| | - Emmanuel Wenger
- Laboratoire de Crystallographie,
Résonance Magnétique et Modélisation, Nancy Université, UMR7036 CNRS-UHP, Boulevard
des Aiguillettes, BPP239, 54506 Vandoeuvre-Lès-Nancy Cedex,
France
| | - Emilia Naydenova
- Department of Organic Chemistry, University of Chemical Technology and Metallurgy, 8
Kliment Ohridski blvd., Sofia 1756, Bulgaria
| | - Jean Martinez
- Institut des Biomolécules
Max Mousseron (IBMM) UMR 5247 CNRS-Université Montpellier 1
et Université Montpellier 2, Bâtiment Chimie (17), Université Montpellier 2, place E. Bataillon,
34095 Montpellier cedex 5, France
| | - Monique Calmès
- Institut des Biomolécules
Max Mousseron (IBMM) UMR 5247 CNRS-Université Montpellier 1
et Université Montpellier 2, Bâtiment Chimie (17), Université Montpellier 2, place E. Bataillon,
34095 Montpellier cedex 5, France
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Matschinsky FM, Zelent B, Doliba N, Li C, Vanderkooi JM, Naji A, Sarabu R, Grimsby J. Glucokinase activators for diabetes therapy: May 2010 status report. Diabetes Care 2011; 34 Suppl 2:S236-43. [PMID: 21525462 PMCID: PMC3632186 DOI: 10.2337/dc11-s236] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- Franz M Matschinsky
- Department of Biochemistry and Biophysics and Diabetes Research Center, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
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Matschinsky FM, Zelent B, Doliba NM, Kaestner KH, Vanderkooi JM, Grimsby J, Berthel SJ, Sarabu R. Research and development of glucokinase activators for diabetes therapy: theoretical and practical aspects. Handb Exp Pharmacol 2011:357-401. [PMID: 21484579 DOI: 10.1007/978-3-642-17214-4_15] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Glucokinase Glucokinase (GK GK ; EC 2.7.1.1.) phosphorylates and regulates glucose metabolism in insulin-producing pancreatic beta-cells, hepatocytes, and certain cells of the endocrine and nervous systems allowing it to play a central role in glucose homeostasis glucose homeostasis . Most importantly, it serves as glucose sensor glucose sensor in pancreatic beta-cells mediating glucose-stimulated insulin biosynthesis and release and it governs the capacity of the liver to convert glucose to glycogen. Activating and inactivating mutations of the glucokinase gene cause autosomal dominant hyperinsulinemic hypoglycemia and hypoinsulinemic hyperglycemia in humans, respectively, illustrating the preeminent role of glucokinase in the regulation of blood glucose and also identifying the enzyme as a potential target for developing antidiabetic drugs antidiabetic drugs . Small molecules called glucokinase activators (GKAs) glucokinase activators (GKAs) which bind to an allosteric activator allosteric activator site of the enzyme have indeed been discovered and hold great promise as new antidiabetic agents. GKAs increase the enzyme's affinity for glucose and also its maximal catalytic rate. Consequently, they stimulate insulin biosynthesis and secretion, enhance hepatic glucose uptake, and augment glucose metabolism and related processes in other glucokinase-expressing cells. Manifestations of these effects, most prominently a lowering of blood glucose, are observed in normal laboratory animals and man but also in animal models of diabetes and patients with type 2 diabetes mellitus (T2DM T2DM ) type 2 diabetes mellitus (T2DM) . These compelling concepts and results sustain a strong R&D effort by many pharmaceutical companies to generate GKAs with characteristics allowing for a novel drug treatment of T2DM.
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Affiliation(s)
- Franz M Matschinsky
- Department of Biochemistry and Biophysics, University of Pennsylvania, Institute for Diabetes, Obesity and Metabolism, 415 Curie Blvd, 605 CRB, Philadelphia, PA 19104, USA.
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23
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Osbak KK, Colclough K, Saint-Martin C, Beer NL, Bellanné-Chantelot C, Ellard S, Gloyn AL. Update on mutations in glucokinase (GCK), which cause maturity-onset diabetes of the young, permanent neonatal diabetes, and hyperinsulinemic hypoglycemia. Hum Mutat 2010; 30:1512-26. [PMID: 19790256 DOI: 10.1002/humu.21110] [Citation(s) in RCA: 339] [Impact Index Per Article: 24.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Glucokinase is a key regulatory enzyme in the pancreatic beta-cell. It plays a crucial role in the regulation of insulin secretion and has been termed the glucose sensor in pancreatic beta-cells. Given its central role in the regulation of insulin release it is understandable that mutations in the gene encoding glucokinase (GCK) can cause both hyper- and hypoglycemia. Heterozygous inactivating mutations in GCK cause maturity-onset diabetes of the young (MODY) subtype glucokinase (GCK), characterized by mild fasting hyperglycemia, which is present at birth but often only detected later in life during screening for other purposes. Homozygous inactivating GCK mutations result in a more severe phenotype presenting at birth as permanent neonatal diabetes mellitus (PNDM). A growing number of heterozygous activating GCK mutations that cause hypoglycemia have also been reported. A total of 620 mutations in the GCK gene have been described in a total of 1,441 families. There are no common mutations, and the mutations are distributed throughout the gene. The majority of activating mutations cluster in a discrete region of the protein termed the allosteric activator site. The identification of a GCK mutation in patients with both hyper- and hypoglycemia has implications for the clinical course and clinical management of their disorder.
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Affiliation(s)
- Kara K Osbak
- Diabetes Research Laboratories, Oxford Centre for Diabetes Endocrinology & Metabolism, University of Oxford, United Kingdom
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24
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Larion M, Miller BG. 23-Residue C-terminal alpha-helix governs kinetic cooperativity in monomeric human glucokinase. Biochemistry 2009; 48:6157-65. [PMID: 19473033 DOI: 10.1021/bi9007534] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Human glucokinase is a monomeric enzyme that displays a sigmoidal steady-state kinetic response toward increasing glucose concentrations. The allosteric regulation produced by glucose is postulated to arise from the slow interconversion of multiple enzyme conformations during the course of catalysis. Crystallographic data suggest that structural rearrangements linked to glucokinase cooperativity involve a substrate-induced repositioning of an alpha-helix (alpha13) located at the C-terminus of the polypeptide. Here, we show that removal of helix alpha13 abolishes cooperativity and restores Michaelis-Menten kinetics, while reducing the k(cat) value of the wild-type enzyme by 160-fold. The impaired catalytic activity of the truncated enzyme is not rescued by the trans addition of a synthetic alpha13 peptide. Unexpectedly, the K(m glucose) value of a glucokinase variant lacking alpha13 is equivalent to the K(0.5 glucose) value of the full-length enzyme. Glucokinase steady-state kinetics is unaffected by the elongation of alpha13 via the addition of a C-terminal polyalanine tail. To explore the link between cooperativity and the primary sequence of alpha13, we randomized seven residues within the helix core. Genetic selection experiments in a glucokinase-deficient bacterium identified a variety of hyperactive alpha13 variants that display lower K(0.5 glucose) values, Hill coefficients near unity, and enhanced equilibrium binding affinities for glucose. The present results demonstrate that alpha13 plays an essential role in facilitating cooperativity. Our findings also establish a link between the primary amino acid sequence of helix alpha13 and the functional dynamics of the glucokinase scaffold that are required for allostery.
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Affiliation(s)
- Mioara Larion
- Department of Chemistry and Biochemistry, The Florida State University, Tallahassee, Florida 32306-4390, USA
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Lys169 of human glucokinase is a determinant for glucose phosphorylation: implication for the atomic mechanism of glucokinase catalysis. PLoS One 2009; 4:e6304. [PMID: 19617908 PMCID: PMC2706991 DOI: 10.1371/journal.pone.0006304] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2009] [Accepted: 06/04/2009] [Indexed: 12/03/2022] Open
Abstract
Glucokinase (GK), a glucose sensor, maintains plasma glucose homeostasis via phosphorylation of glucose and is a potential therapeutic target for treating maturity-onset diabetes of the young (MODY) and persistent hyperinsulinemic hypoglycemia of infancy (PHHI). To characterize the catalytic mechanism of glucose phosphorylation by GK, we combined molecular modeling, molecular dynamics (MD) simulations, quantum mechanics/molecular mechanics (QM/MM) calculations, experimental mutagenesis and enzymatic kinetic analysis on both wild-type and mutated GK. Our three-dimensional (3D) model of the GK-Mg2+-ATP-glucose (GMAG) complex, is in agreement with a large number of mutagenesis data, and elucidates atomic information of the catalytic site in GK for glucose phosphorylation. A 10-ns MD simulation of the GMAG complex revealed that Lys169 plays a dominant role in glucose phosphorylation. This prediction was verified by experimental mutagenesis of GK (K169A) and enzymatic kinetic analyses of glucose phosphorylation. QM/MM calculations were further used to study the role of Lys169 in the catalytic mechanism of the glucose phosphorylation and we found that Lys169 enhances the binding of GK with both ATP and glucose by serving as a bridge between ATP and glucose. More importantly, Lys169 directly participates in the glucose phosphorylation as a general acid catalyst. Our findings provide mechanistic details of glucose phorphorylation catalyzed by GK, and are important for understanding the pathogenic mechanism of MODY.
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Sayed S, Langdon DR, Odili S, Chen P, Buettger C, Schiffman AB, Suchi M, Taub R, Grimsby J, Matschinsky FM, Stanley CA. Extremes of clinical and enzymatic phenotypes in children with hyperinsulinism caused by glucokinase activating mutations. Diabetes 2009; 58:1419-27. [PMID: 19336674 PMCID: PMC2682682 DOI: 10.2337/db08-1792] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
OBJECTIVE Heterozygous activating mutations of glucokinase have been reported to cause hypoglycemia attributable to hyperinsulinism in a limited number of families. We report three children with de novo glucokinase hyperinsulinism mutations who displayed a spectrum of clinical phenotypes corresponding to marked differences in enzyme kinetics. RESEARCH DESIGN AND METHODS Mutations were directly sequenced, and mutants were expressed as glutathionyl S-transferase-glucokinase fusion proteins. Kinetic analysis of the enzymes included determinations of stability, activity index, the response to glucokinase activator drug, and the effect of glucokinase regulatory protein. RESULTS Child 1 had an ins454A mutation, child 2 a W99L mutation, and child 3 an M197I mutation. Diazoxide treatment was effective in child 3 but ineffective in child 1 and only partially effective in child 2. Expression of the mutant glucokinase ins454A, W99L, and M197I enzymes revealed a continuum of high relative activity indexes in the three children (26, 8.9, and 3.1, respectively; wild type = 1.0). Allosteric responses to inhibition by glucokinase regulatory protein and activation by the drug RO0281675 were impaired by the ins454A but unaffected by the M197I mutation. Estimated thresholds for glucose-stimulated insulin release were more severely reduced by the ins454A than the M197I mutation and intermediate in the W99L mutation (1.1, 3.5, and 2.2 mmol/l, respectively; wild type = 5.0 mmol/l). CONCLUSIONS These results confirm the potency of glucokinase as the pancreatic beta-cell glucose sensor, and they demonstrate that responsiveness to diazoxide varies with genotype in glucokinase hyperinsulinism resulting in hypoglycemia, which can be more difficult to control than previously believed.
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Affiliation(s)
- Samir Sayed
- Clinical Translational Research Center, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - David R. Langdon
- Division of Endocrinology and Diabetes, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - Stella Odili
- Diabetes and Endocrinology Research Center, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania
| | - Pan Chen
- Division of Endocrinology and Diabetes, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - Carol Buettger
- Diabetes and Endocrinology Research Center, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania
| | - Alisa B. Schiffman
- Division of Endocrinology and Diabetes, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - Mariko Suchi
- Department of Pathology, Medical College of Wisconsin, Milwaukee, Wisconsin
- Department of Pathology, Children's Hospital of Wisconsin, Milwaukee, Wisconsin
| | - Rebecca Taub
- Department of Metabolic Diseases, Roche, Nutley, New Jersey
| | - Joseph Grimsby
- Department of Metabolic Diseases, Roche, Nutley, New Jersey
| | - Franz M. Matschinsky
- Diabetes and Endocrinology Research Center, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania
- Department of Biochemistry and Biophysics, the University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania
| | - Charles A. Stanley
- Clinical Translational Research Center, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania
- Division of Endocrinology and Diabetes, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania
- Corresponding author: Charles A. Stanley,
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Antoine M, Boutin JA, Ferry G. Binding Kinetics of Glucose and Allosteric Activators to Human Glucokinase Reveal Multiple Conformational States. Biochemistry 2009; 48:5466-82. [DOI: 10.1021/bi900374c] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Mathias Antoine
- Division de Pharmacologie Moléculaire et Cellulaire, Institut de Recherches Servier, 125 Chemin de Ronde, 78290 Croissy-sur-Seine, France
| | - Jean A. Boutin
- Division de Pharmacologie Moléculaire et Cellulaire, Institut de Recherches Servier, 125 Chemin de Ronde, 78290 Croissy-sur-Seine, France
| | - Gilles Ferry
- Division de Pharmacologie Moléculaire et Cellulaire, Institut de Recherches Servier, 125 Chemin de Ronde, 78290 Croissy-sur-Seine, France
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Abstract
Glucokinase, a unique isoform of the hexokinase enzymes, which are known to phosphorylate D-glucose and other hexoses, was identified during the past three to four decades as a new, promising drug target for type 2 diabetes. Glucokinase serves as a glucose sensor of the insulin-producing pancreatic islet beta-cells, controls the conversion of glucose to glycogen in the liver and regulates hepatic glucose production. Guided by this fundamental knowledge, several glucokinase activators are now being developed, and have so far been shown to lower blood glucose in several animal models of type 2 diabetes and in initial trials in humans with the disease. Here, the scientific basis and current status of this new approach to diabetes therapy are discussed.
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