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Vinces TC, de Souza AS, Carvalho CF, Visnardi AB, Teixeira RD, Llontop EE, Bismara BAP, Vicente EJ, Pereira JO, de Souza RF, Yonamine M, Marana SR, Farah CS, Guzzo CR. Monomeric Esterase: Insights into Cooperative Behavior, Hysteresis/Allokairy. Biochemistry 2024; 63:1178-1193. [PMID: 38669355 DOI: 10.1021/acs.biochem.3c00668] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/28/2024]
Abstract
Herein, we present a novel esterase enzyme, Ade1, isolated from a metagenomic library of Amazonian dark earths soils, demonstrating its broad substrate promiscuity by hydrolyzing ester bonds linked to aliphatic groups. The three-dimensional structure of the enzyme was solved in the presence and absence of substrate (tributyrin), revealing its classification within the α/β-hydrolase superfamily. Despite being a monomeric enzyme, enzymatic assays reveal a cooperative behavior with a sigmoidal profile (initial velocities vs substrate concentrations). Our investigation brings to light the allokairy/hysteresis behavior of Ade1, as evidenced by a transient burst profile during the hydrolysis of substrates such as p-nitrophenyl butyrate and p-nitrophenyl octanoate. Crystal structures of Ade1, coupled with molecular dynamics simulations, unveil the existence of multiple conformational structures within a single molecular state (E̅1). Notably, substrate binding induces a loop closure that traps the substrate in the catalytic site. Upon product release, the cap domain opens simultaneously with structural changes, transitioning the enzyme to a new molecular state (E̅2). This study advances our understanding of hysteresis/allokairy mechanisms, a temporal regulation that appears more pervasive than previously acknowledged and extends its presence to metabolic enzymes. These findings also hold potential implications for addressing human diseases associated with metabolic dysregulation.
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Affiliation(s)
- Tania Churasacari Vinces
- Department of Microbiology, Institute of Biomedical Sciences, University of São Paulo, São Paulo CEP 05508-000, Brazil
| | - Anacleto Silva de Souza
- Department of Microbiology, Institute of Biomedical Sciences, University of São Paulo, São Paulo CEP 05508-000, Brazil
| | - Cecília F Carvalho
- Department of Microbiology, Institute of Biomedical Sciences, University of São Paulo, São Paulo CEP 05508-000, Brazil
| | - Aline Biazola Visnardi
- Department of Microbiology, Institute of Biomedical Sciences, University of São Paulo, São Paulo CEP 05508-000, Brazil
| | - Raphael D Teixeira
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo CEP 05508-000, Brazil
| | - Edgar E Llontop
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo CEP 05508-000, Brazil
| | - Beatriz Aparecida Passos Bismara
- Department of Clinical and Toxicological Analyses, School of Pharmaceutical Sciences, University of São Paulo, São Paulo CEP 05508-000, Brazil
| | - Elisabete J Vicente
- Department of Microbiology, Institute of Biomedical Sciences, University of São Paulo, São Paulo CEP 05508-000, Brazil
| | - José O Pereira
- Biotechnology Group, Federal University of Amazonas, Amazonas CEP 69077-000, Brazil
| | - Robson Francisco de Souza
- Department of Microbiology, Institute of Biomedical Sciences, University of São Paulo, São Paulo CEP 05508-000, Brazil
| | - Mauricio Yonamine
- Department of Clinical and Toxicological Analyses, School of Pharmaceutical Sciences, University of São Paulo, São Paulo CEP 05508-000, Brazil
| | - Sandro Roberto Marana
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo CEP 05508-000, Brazil
| | - Chuck Shaker Farah
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo CEP 05508-000, Brazil
| | - Cristiane R Guzzo
- Department of Microbiology, Institute of Biomedical Sciences, University of São Paulo, São Paulo CEP 05508-000, Brazil
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2
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Li C, Juliana CA, Yuan Y, Li M, Lu M, Chen P, Boodhansingh KE, Doliba NM, Bhatti TR, Adzick NS, Stanley CA, De León DD. Phenotypic Characterization of Congenital Hyperinsulinism Due to Novel Activating Glucokinase Mutations. Diabetes 2023; 72:1809-1819. [PMID: 37725835 PMCID: PMC10658072 DOI: 10.2337/db23-0465] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/12/2023] [Accepted: 09/10/2023] [Indexed: 09/21/2023]
Abstract
The importance of glucokinase (GK) in the regulation of insulin secretion has been highlighted by the phenotypes of individuals with activating and inactivating mutations in the glucokinase gene (GCK). Here we report 10 individuals with congenital hyperinsulinism (HI) caused by eight unique activating mutations of GCK. Six are novel and located near previously identified activating mutations sites. The first recognized episode of hypoglycemia in these patients occurred between birth and 24 years, and the severity of the phenotype was also variable. Mutant enzymes were expressed and purified for enzyme kinetics in vitro. Mutant enzymes had low glucose half-saturation concentration values and an increased enzyme activity index compared with wild-type GK. We performed functional evaluation of islets from the pancreata of three children with GCK-HI who required pancreatectomy. Basal insulin secretion in perifused GCK-HI islets was normal, and the response to glyburide was preserved. However, the threshold for glucose-stimulated insulin secretion in perifused glucokinase hyperinsulinism (GCK-HI) islets was decreased, and glucagon secretion was greatly suppressed. Our evaluation of novel GCK disease-associated mutations revealed that the detrimental effects of these mutations on glucose homeostasis can be attributed not only to a lowering of the glucose threshold of insulin secretion but also to a decreased counterregulatory glucagon secretory response. ARTICLE HIGHLIGHTS Our evaluation of six novel and two previously published activating GCK mutations revealed that the detrimental effects of these mutations on glucose homeostasis can be attributed not only to a lowering of the glucose threshold of insulin secretion but also to a decreased counterregulatory glucagon secretory response. These studies provide insights into the pathophysiology of GCK-hyperinsulinism and the dual role of glucokinase in β-cells and α-cells to regulate glucose homeostasis.
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Affiliation(s)
- Changhong Li
- Division of Endocrinology and Diabetes, The Children’s Hospital of Philadelphia, Philadelphia, PA
- Department of Pediatrics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA
- Nanjing AscendRare Pharmaceutical Technology Co., Nanjing, China
| | - Christine A. Juliana
- Division of Endocrinology and Diabetes, The Children’s Hospital of Philadelphia, Philadelphia, PA
| | - Yue Yuan
- Nanjing AscendRare Pharmaceutical Technology Co., Nanjing, China
| | - Ming Li
- Department of Endocrinology, National Health Commission (NHC) Key Laboratory of Endocrinology, Peking Union Medical College Hospital, Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing, China
| | - Ming Lu
- Division of Endocrinology and Diabetes, The Children’s Hospital of Philadelphia, Philadelphia, PA
| | - Pan Chen
- Division of Endocrinology and Diabetes, The Children’s Hospital of Philadelphia, Philadelphia, PA
| | - Kara E. Boodhansingh
- Division of Endocrinology and Diabetes, The Children’s Hospital of Philadelphia, Philadelphia, PA
| | - Nicolai M. Doliba
- Institute of Diabetes, Obesity and Metabolism, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA
| | - Tricia R. Bhatti
- Department of Pathology, The Children’s Hospital of Philadelphia, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA
| | - N. Scott Adzick
- Department of Surgery, The Children’s Hospital of Philadelphia, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA
| | - Charles A. Stanley
- Division of Endocrinology and Diabetes, The Children’s Hospital of Philadelphia, Philadelphia, PA
- Department of Pediatrics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA
| | - Diva D. De León
- Division of Endocrinology and Diabetes, The Children’s Hospital of Philadelphia, Philadelphia, PA
- Department of Pediatrics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA
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3
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Lee CT, Tsai WH, Chang CC, Chen PC, Fann CSJ, Chang HK, Liu SY, Wu MZ, Chiu PC, Hsu WM, Yang WS, Lai LP, Tsai WY, Yang SB, Chen PL. Genotype-phenotype correlation in Taiwanese children with diazoxide-unresponsive congenital hyperinsulinism. Front Endocrinol (Lausanne) 2023; 14:1283907. [PMID: 38033998 PMCID: PMC10687152 DOI: 10.3389/fendo.2023.1283907] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/27/2023] [Accepted: 10/23/2023] [Indexed: 12/02/2023] Open
Abstract
Objective Congenital hyperinsulinism (CHI) is a group of clinically and genetically heterogeneous disorders characterized by dysregulated insulin secretion. The aim of the study was to elucidate genetic etiologies of Taiwanese children with the most severe diazoxide-unresponsive CHI and analyze their genotype-phenotype correlations. Methods We combined Sanger with whole exome sequencing (WES) to analyze CHI-related genes. The allele frequency of the most common variant was estimated by single-nucleotide polymorphism haplotype analysis. The functional effects of the ATP-sensitive potassium (KATP) channel variants were assessed using patch clamp recording and Western blot. Results Nine of 13 (69%) patients with ten different pathogenic variants (7 in ABCC8, 2 in KCNJ11 and 1 in GCK) were identified by the combined sequencing. The variant ABCC8 p.T1042QfsX75 identified in three probands was located in a specific haplotype. Functional study revealed the human SUR1 (hSUR1)-L366F KATP channels failed to respond to intracellular MgADP and diazoxide while hSUR1-R797Q and hSUR1-R1393C KATP channels were defective in trafficking. One patient had a de novo dominant mutation in the GCK gene (p.I211F), and WES revealed mosaicism of this variant from another patient. Conclusion Pathogenic variants in KATP channels are the most common underlying cause of diazoxide-unresponsive CHI in the Taiwanese cohort. The p.T1042QfsX75 variant in the ABCC8 gene is highly suggestive of a founder effect. The I211F mutation in the GCK gene and three rare SUR1 variants associated with defective gating (p.L366F) or traffic (p.R797Q and p.R1393C) KATP channels are also associated with the diazoxide-unresponsive phenotype.
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Affiliation(s)
- Cheng-Ting Lee
- Department of Pediatrics, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan
- Graduate Institute of Clinical Medicine, National Taiwan University College of Medicine, Taipei, Taiwan
| | - Wen-Hao Tsai
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | | | - Pei-Chun Chen
- Department of Physiology, National Cheng-Kung University, Tainan, Taiwan
| | | | - Hsueh-Kai Chang
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Shih-Yao Liu
- Department of Pediatrics, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan
| | - Mu-Zon Wu
- Department of Pathology, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan
| | - Pao-Chin Chiu
- Department of Pediatrics, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan
| | - Wen-Ming Hsu
- Department of Surgery, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan
| | - Wei-Shiung Yang
- Graduate Institute of Clinical Medicine, National Taiwan University College of Medicine, Taipei, Taiwan
- Department of Internal Medicine, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan
- Graduate Institute of Medical Genomics and Proteomics, National Taiwan University College of Medicine, Taipei, Taiwan
| | - Ling-Ping Lai
- Department of Internal Medicine, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan
| | - Wen-Yu Tsai
- Department of Pediatrics, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan
| | - Shi-Bing Yang
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Pei-Lung Chen
- Department of Internal Medicine, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan
- Graduate Institute of Medical Genomics and Proteomics, National Taiwan University College of Medicine, Taipei, Taiwan
- Department of Medical Genetics, National Taiwan University Hospital, Taipei, Taiwan
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Gordon BH, Liu P, Whittington AC, Silvers R, Miller BG. Biochemical methods to map and quantify allosteric motions in human glucokinase. Methods Enzymol 2023; 685:433-459. [PMID: 37245911 PMCID: PMC10308428 DOI: 10.1016/bs.mie.2023.03.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Allosteric regulation of protein function is ubiquitous in biology. Allostery originates from ligand-mediated alterations in polypeptide structure and/or dynamics, which produce a cooperative kinetic or thermodynamic response to changing ligand concentrations. Establishing a mechanistic description of individual allosteric events requires both mapping the relevant changes in protein structure and quantifying the rates of differential conformational dynamics in the absence and presence of effectors. In this chapter, we describe three biochemical approaches to understand the dynamic and structural signatures of protein allostery using the well-established cooperative enzyme glucokinase as a case study. The combined application of pulsed proteolysis, biomolecular nuclear magnetic resonance spectroscopy and hydrogen-deuterium exchange mass spectrometry offers complementary information that can used to establish molecular models for allosteric proteins, especially when differential protein dynamics are involved.
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Affiliation(s)
- Blaine H Gordon
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL, United States; Institute of Molecular Biophysics, Florida State University, Tallahassee, FL, United States
| | - Peilu Liu
- Protein Analytical Chemistry, Genentech Inc., South San Francisco, CA, United States
| | - A Carl Whittington
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL, United States; Department of Biological Science, Florida State University, Tallahassee, FL, United States
| | - Robert Silvers
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL, United States; Institute of Molecular Biophysics, Florida State University, Tallahassee, FL, United States
| | - Brian G Miller
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL, United States.
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5
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Boodhansingh KE, Yang Z, Li C, Chen P, Lord K, Becker SA, States LJ, Adzick NS, Bhatti T, Shyng SL, Ganguly A, Stanley CA, De Leon DD. Localized islet nuclear enlargement hyperinsulinism (LINE-HI) due to ABCC8 and GCK mosaic mutations. Eur J Endocrinol 2022; 187:301-313. [PMID: 35674212 PMCID: PMC9339501 DOI: 10.1530/eje-21-1095] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Accepted: 06/07/2022] [Indexed: 11/08/2022]
Abstract
OBJECTIVE Congenital hyperinsulinism (HI) is the most common cause of persistent hypoglycemia in children. In addition to typical focal or diffuse HI, some cases with diazoxide-unresponsive congenital HI have atypical pancreatic histology termed Localized Islet Nuclear Enlargement (LINE) or mosaic HI, characterized by histologic features similar to diffuse HI, but confined to only a region of pancreas. Our objective was to characterize the phenotype and genotype of children with LINE-HI. DESIGN The phenotype and genotype features of 12 children with pancreatic histology consistent with LINE-HI were examined. METHODS We compiled clinical features of 12 children with LINE-HI and performed next-generation sequencing on specimens of pancreas from eight of these children to look for mosaic mutations in genes known to be associated with diazoxide-unresponsive HI (ABCC8, KCNJ11, and GCK). RESULTS Children with LINE-HI had lower birth weights and later ages of presentation compared to children with typical focal or diffuse HI. Partial pancreatectomy in LINE-HI cases resulted in euglycemia in 75% of cases; no cases have developed diabetes. Low-level mosaic mutations were identified in the pancreas of six cases with LINE-HI (three in ABCC8, three in GCK). Expression studies confirmed that all novel mutations were pathogenic. CONCLUSION These results indicate that post-zygotic low-level mosaic mutations of known HI genes are responsible for some cases of LINE-HI that lack an identifiable germ-line mutation and that partial pancreatectomy may be curative for these cases.
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Affiliation(s)
- Kara E. Boodhansingh
- Division of Endocrinology and Diabetes, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - Zhongying Yang
- Department of Chemical Physiology and Biochemistry, Oregon Health & Science University, Portland, Oregon
| | - Changhong Li
- Division of Endocrinology and Diabetes, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - Pan Chen
- Division of Endocrinology and Diabetes, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - Katherine Lord
- Division of Endocrinology and Diabetes, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania
- Department of Pediatrics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania
| | - Susan A. Becker
- Department of Radiology, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - Lisa J. States
- Department of Radiology, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania
- Department of Radiology, The Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania
| | - N. Scott Adzick
- Department of Surgery, The Children’s Hospital of Philadelphia, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104
| | - Tricia Bhatti
- Department of Pathology, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania
- Department of Pathology, The Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania
| | - Show-Ling Shyng
- Department of Chemical Physiology and Biochemistry, Oregon Health & Science University, Portland, Oregon
| | - Arupa Ganguly
- Department of Genetics, The Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania
| | - Charles A. Stanley
- Division of Endocrinology and Diabetes, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania
- Department of Pediatrics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania
| | - Diva D. De Leon
- Division of Endocrinology and Diabetes, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania
- Department of Pediatrics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania
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6
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Langer S, Waterstradt R, Hillebrand G, Santer R, Baltrusch S. The novel GCK variant p.Val455Leu associated with hyperinsulinism is susceptible to allosteric activation and is conducive to weight gain and the development of diabetes. Diabetologia 2021; 64:2687-2700. [PMID: 34532767 PMCID: PMC8563668 DOI: 10.1007/s00125-021-05553-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Accepted: 06/21/2021] [Indexed: 11/26/2022]
Abstract
AIMS/HYPOTHESIS The mammalian enzyme glucokinase (GK), expressed predominantly in liver and pancreas, plays an essential role in carbohydrate metabolism. Monogenic GK disorders emphasise the role of GK in determining the blood glucose set point. METHODS A family with congenital hyperinsulinism (CHI) was examined for GCK gene variants by Sanger sequencing. A combined approach, involving kinetic analysis (also using GK activators and inhibitors), intracellular translocation assays, insulin secretion measurements and structural modelling, was used to investigate the novel variant compared with known variants. RESULTS We report on the novel gain-of-function GCK variant p.Val455Leu (V455L), inherited as an autosomal dominant trait in a German family with CHI and concomitant obesity (fasting blood glucose 2.1 mmol/l, BMI 45.0 kg/m2, HOMA-IR 1.5 in an adult female family member); one male family member developed type 2 diabetes until age 35 years (with fasting glucose 2.8-3.7 mmol/l, BMI 38.9 kg/m2, HOMA-IR 4.6). Kinetic characterisation of the V455L variant revealed a significant increase in glucose affinity (glucose concentration at which reaction rate is half its maximum rate [S0.5]: mutant 2.4 ± 0.3 mmol/l vs wild-type 7.6 ± 1.0 mmol/l), accompanied by a distinct additive susceptibility to both the endogenous activator fructose 2,6-bisphosphatase and the synthetic allosteric activator RO-28-1675. The effect of RO-28-1675 was more pronounced when compared with the previously known GK variants V455M and V455E. Binding to the inhibitor glucokinase regulatory protein was unimpaired for V455L and V455E but was reduced for V455M, whereas mannoheptulose inhibited all GK variants and the wild-type enzyme. Structural analyses suggested a role for residue 455 in rearrangements between the inactive and active conformations of GK and also in allosteric activation. Comparison with V455M and V455E and an overview of activating GK variants provided a context for the novel sequence aberration in terms of altered GK enzyme characteristics caused by single amino acid changes. CONCLUSION/INTERPRETATION We provide new knowledge on the structure-function relationship of GK, with special emphasis on enzyme activation, potentially yielding fresh strategic insights into breaking the vicious circle of fluctuating blood glucose levels and the attendant risk of long-lasting metabolic changes in both CHI and type 2 diabetes.
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Affiliation(s)
- Sara Langer
- Institute of Medical Biochemistry and Molecular Biology, University Medicine Rostock, Rostock, Germany
| | - Rica Waterstradt
- Institute of Medical Biochemistry and Molecular Biology, University Medicine Rostock, Rostock, Germany
| | - Georg Hillebrand
- Department of Pediatrics, University Medical Center Eppendorf, Hamburg, Germany
- Department of Pediatrics, Medical Center Itzehoe, Itzehoe, Germany
| | - René Santer
- Department of Pediatrics, University Medical Center Eppendorf, Hamburg, Germany
| | - Simone Baltrusch
- Institute of Medical Biochemistry and Molecular Biology, University Medicine Rostock, Rostock, Germany.
- Department Life, Light & Matter, University of Rostock, Rostock, Germany.
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7
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Peng Y, Li H, Liu Z, Zhang C, Li K, Gong Y, Geng L, Su J, Guan X, Liu L, Zhou R, Zhao Z, Guo J, Liang Q, Li X. Chromosome-level genome assembly of the Arctic fox (Vulpes lagopus) using PacBio sequencing and Hi-C technology. Mol Ecol Resour 2021; 21:2093-2108. [PMID: 33829635 DOI: 10.1111/1755-0998.13397] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Revised: 03/28/2021] [Accepted: 03/30/2021] [Indexed: 10/21/2022]
Abstract
The Arctic fox (Vulpes lagopus) is the only fox species occurring in the Arctic and has adapted to its extreme climatic conditions. Currently, the molecular basis of its adaptation to the extreme climate has not been characterized. Here, we applied PacBio sequencing and chromosome structure capture technique to assemble the first V. lagopus genome assembly, which is assembled into chromosome fragments. The genome assembly has a total length of 2.345 Gb with a contig N50 of 31.848 Mb and a scaffold N50 of 131.537 Mb, consisting of 25 pseudochromosomal scaffolds. The V. lagopus genome had approximately 32.33% repeat sequences. In total, 21,278 protein-coding genes were predicted, of which 99.14% were functionally annotated. Compared with 12 other mammals, V. lagopus was most closely related to V. Vulpes with an estimated divergence time of ~7.1 Ma. The expanded gene families and positively selected genes potentially play roles in the adaptation of V. lagopus to Arctic extreme environment. This high-quality assembled genome will not only promote future studies of genetic diversity and evolution in foxes and other canids but also provide important resources for conservation of Arctic species.
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Affiliation(s)
- Yongdong Peng
- Hebei Key Laboratory of Specialty Animal Germplasm Resources Exploration and Innovation (Under Planning), College of Animal Science and Technology, Hebei Normal University of Science and Technology, Qinhuangdao, China
| | - Hong Li
- Novogene Bioinformatics Institute, Beijing, China
| | - Zhengzhu Liu
- Hebei Key Laboratory of Specialty Animal Germplasm Resources Exploration and Innovation (Under Planning), College of Animal Science and Technology, Hebei Normal University of Science and Technology, Qinhuangdao, China
| | - Chuansheng Zhang
- Hebei Key Laboratory of Specialty Animal Germplasm Resources Exploration and Innovation (Under Planning), College of Animal Science and Technology, Hebei Normal University of Science and Technology, Qinhuangdao, China
| | - Keqiang Li
- Hebei Key Laboratory of Specialty Animal Germplasm Resources Exploration and Innovation (Under Planning), College of Mathematics and Information Science, Hebei Normal University of Science and Technology, Qinhuangdao, China
| | - Yuanfang Gong
- Hebei Key Laboratory of Specialty Animal Germplasm Resources Exploration and Innovation (Under Planning), College of Animal Science and Technology, Hebei Normal University of Science and Technology, Qinhuangdao, China
| | - Liying Geng
- Hebei Key Laboratory of Specialty Animal Germplasm Resources Exploration and Innovation (Under Planning), College of Agronomy and Biotechnology, Hebei Normal University of Science and Technology, Qinhuangdao, China
| | - Jingjing Su
- Hebei Key Laboratory of Applied Chemistry, School of Environmental and Chemical Engineering, Yanshan University, Qinhuangdao, China
| | - Xuemin Guan
- Hebei Key Laboratory of Specialty Animal Germplasm Resources Exploration and Innovation (Under Planning), College of Agronomy and Biotechnology, Hebei Normal University of Science and Technology, Qinhuangdao, China
| | - Lei Liu
- College of Animal Science and Technology, Shandong Agricultural University, Tai-an, China
| | - Ruihong Zhou
- Hebei Key Laboratory of Specialty Animal Germplasm Resources Exploration and Innovation (Under Planning), College of Animal Science and Technology, Hebei Normal University of Science and Technology, Qinhuangdao, China
| | - Ziya Zhao
- Hebei Key Laboratory of Specialty Animal Germplasm Resources Exploration and Innovation (Under Planning), College of Animal Science and Technology, Hebei Normal University of Science and Technology, Qinhuangdao, China
| | - Jianxu Guo
- Hebei Key Laboratory of Specialty Animal Germplasm Resources Exploration and Innovation (Under Planning), College of Animal Science and Technology, Hebei Normal University of Science and Technology, Qinhuangdao, China
| | - Qiqi Liang
- Novogene Bioinformatics Institute, Beijing, China
| | - Xianglong Li
- Hebei Key Laboratory of Specialty Animal Germplasm Resources Exploration and Innovation (Under Planning), College of Animal Science and Technology, Hebei Normal University of Science and Technology, Qinhuangdao, China
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8
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Sternisha SM, Miller BG. Molecular and cellular regulation of human glucokinase. Arch Biochem Biophys 2019; 663:199-213. [PMID: 30641049 DOI: 10.1016/j.abb.2019.01.011] [Citation(s) in RCA: 73] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2018] [Revised: 01/09/2019] [Accepted: 01/10/2019] [Indexed: 01/23/2023]
Abstract
Glucose metabolism in humans is tightly controlled by the activity of glucokinase (GCK). GCK is predominantly produced in the pancreas, where it catalyzes the rate-limiting step of insulin secretion, and in the liver, where it participates in glycogen synthesis. A multitude of disease-causing mutations within the gck gene have been identified. Activating mutations manifest themselves in the clinic as congenital hyperinsulinism, while loss-of-function mutations produce several diabetic conditions. Indeed, pharmaceutical companies have shown great interest in developing GCK-associated treatments for diabetic patients. Due to its essential role in maintaining whole-body glucose homeostasis, GCK activity is extensively regulated at multiple levels. GCK possesses a unique ability to self-regulate its own activity via slow conformational dynamics, which allows for a cooperative response to glucose. GCK is also subject to a number of protein-protein interactions and post-translational modification events that produce a broad range of physiological consequences. While significant advances in our understanding of these individual regulatory mechanisms have been recently achieved, how these strategies are integrated and coordinated within the cell is less clear. This review serves to synthesize the relevant findings and offer insights into the connections between molecular and cellular control of GCK.
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Affiliation(s)
- Shawn M Sternisha
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL, 32306, USA
| | - Brian G Miller
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL, 32306, USA.
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9
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First evidence of changes in enzyme kinetics and stability of glucokinase affected by somatic cancer-associated variations. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2018; 1867:213-218. [PMID: 30590153 DOI: 10.1016/j.bbapap.2018.12.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Revised: 12/07/2018] [Accepted: 12/20/2018] [Indexed: 12/27/2022]
Abstract
Recent investigation of somatic variations of allosterically regulated proteins in cancer genomes suggested that variations in glucokinase (GCK) might play a role in tumorigenesis. We hypothesized that somatic cancer-associated GCK variations include in part those with activating and/or stabilizing effects. We analyzed the enzyme kinetics and thermostability of recombinant proteins possessing the likely activating variations and the variations present in the connecting loop I and provided the first experimental evidence of the effects of somatic cancer-associated GCK variations. Activating and/or stabilizing variations were common among the analyzed cancer-associated variations, which was in strong contrast to their low frequency among germinal variations. The activating and stabilizing variations displayed focal distribution with respect to the tertiary structure, and were present in the surroundings of the heterotropic allosteric activator site, including but not limited to the connecting loop I and in the active site region subject to extensive rearrangements upon glucose binding. Activating somatic cancer-associated variations induced a reduction of GCK's cooperativity and an increase in the affinity to glucose (a decline in the S0.5 values). The hotspot-associated variations, which decreased cooperativity, also increased the half-maximal inhibitory concentrations of the competitive GCK inhibitor, N-acetylglucosamine. Concluded, we have provided the first convincing biochemical evidence establishing GCK as a previously unrecognized enzyme that contributes to the reprogramming of energy metabolism in cancer cells. Activating GCK variations substantially increase affinity of GCK to glucose, disrupt the otherwise characteristic sigmoidal response to glucose and/or prolong the enzyme half-life. This, combined, facilitates glucose phosphorylation, thus supporting glycolysis and associated pathways.
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Sternisha SM, Liu P, Marshall AG, Miller BG. Mechanistic Origins of Enzyme Activation in Human Glucokinase Variants Associated with Congenital Hyperinsulinism. Biochemistry 2018; 57:1632-1639. [PMID: 29425029 DOI: 10.1021/acs.biochem.8b00022] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Human glucokinase (GCK) acts as the body's primary glucose sensor and plays a critical role in glucose homeostatic maintenance. Gain-of-function mutations in gck produce hyperactive enzyme variants that cause congenital hyperinsulinism. Prior biochemical and biophysical studies suggest that activated disease variants can be segregated into two mechanistically distinct classes, termed α-type and β-type. Steady-state viscosity variation studies indicate that the kcat values of wild-type GCK and an α-type variant are partially diffusion-limited, whereas the kcat value of a β-type variant is viscosity-independent. Transient-state chemical quench-flow analyses demonstrate that wild-type GCK and the α-type variant display burst kinetics, whereas the β-type variant lacks a burst phase. Comparative hydrogen-deuterium exchange mass spectrometry of unliganded enzymes demonstrates that a disordered active site loop, which folds upon binding of glucose, is protected from exchange in the α-type variant. The α-type variant also displays an increased level of exchange within a β-strand located near the enzyme's hinge region, which becomes more solvent-exposed upon glucose binding. In contrast, β-type activation causes no substantial difference in global or local exchange relative to that of unliganded, wild-type GCK. Together, these results demonstrate that α-type activation results from a shift in the conformational ensemble of unliganded GCK toward a state resembling the glucose-bound conformation, whereas β-type activation is attributable to an accelerated rate of product release. This work elucidates the molecular basis of naturally occurring, activated GCK disease variants and provides insight into the structural and dynamic origins of GCK's unique kinetic cooperativity.
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Affiliation(s)
- Shawn M Sternisha
- Department of Chemistry and Biochemistry , Florida State University , Tallahassee , Florida 32306 , United States
| | - Peilu Liu
- Department of Chemistry and Biochemistry , Florida State University , Tallahassee , Florida 32306 , United States
| | - Alan G Marshall
- Department of Chemistry and Biochemistry , Florida State University , Tallahassee , Florida 32306 , United States.,Ion Cyclotron Resonance Program , The National High Magnetic Field Laboratory , Tallahassee , Florida 32310 , United States
| | - Brian G Miller
- Department of Chemistry and Biochemistry , Florida State University , Tallahassee , Florida 32306 , United States
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11
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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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12
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Rexford A, Zorio DAR, Miller BG. Biochemical and biophysical investigations of the interaction between human glucokinase and pro-apoptotic BAD. PLoS One 2017; 12:e0171587. [PMID: 28182770 PMCID: PMC5300155 DOI: 10.1371/journal.pone.0171587] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Accepted: 01/23/2017] [Indexed: 11/28/2022] Open
Abstract
The glycolytic enzyme glucokinase (GCK) and the pro-apoptotic protein BAD reportedly reside within a five-membered complex that localizes to the mitochondria of mammalian hepatocytes and pancreatic β-cells. Photochemical crosslinking studies using a synthetic analog of BAD’s BH3 domain and in vitro transcription/translation experiments support a direct interaction between BAD and GCK. To investigate the biochemical and biophysical consequences of the BAD:GCK interaction, we developed a method for the production of recombinant human BAD. Consistent with published reports, recombinant BAD displays high affinity for Bcl-xL (KD = 7 nM), and phosphorylation of BAD at S118, within the BH3 domain, abolishes this interaction. Unexpectedly, we do not detect association of recombinant, full-length BAD with recombinant human pancreatic GCK over a range of protein concentrations using various biochemical methods including size-exclusion chromatography, chemical cross-linking, analytical ultracentrifugation, and isothermal titration calorimetry. Furthermore, fluorescence polarization assays and isothermal titration calorimetry detect no direct interaction between GCK and BAD BH3 peptides. Kinetic characterization of GCK in the presence of high concentrations of recombinant BAD show modest (<15%) increases in GCK activity, observable only at glucose concentrations well below the K0.5 value. GCK activity is unaffected by BAD BH3 peptides. These results raise questions as to the mechanism of action of stapled peptide analogs modeled after the BAD BH3 domain, which reportedly enhance the Vmax value of GCK and stimulate insulin release in BAD-deficient islets. Based on our results, we postulate that the BAD:GCK interaction, and any resultant regulatory effect(s) upon GCK activity, requires the participation of additional members of the mitochondrial complex.
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Affiliation(s)
- Alix Rexford
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida, United States of America
| | - Diego A. R. Zorio
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida, United States of America
| | - Brian G. Miller
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida, United States of America
- * E-mail:
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13
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Abstract
Cooperativity in human glucokinase (GCK), the body's primary glucose sensor and a major determinant of glucose homeostatic diseases, is fundamentally different from textbook models of allostery because GCK is monomeric and contains only one glucose-binding site. Prior work has demonstrated that millisecond timescale order-disorder transitions within the enzyme's small domain govern cooperativity. Here, using limited proteolysis, we map the site of disorder in unliganded GCK to a 30-residue active-site loop that closes upon glucose binding. Positional randomization of the loop, coupled with genetic selection in a glucokinase-deficient bacterium, uncovers a hyperactive GCK variant with substantially reduced cooperativity. Biochemical and structural analysis of this loop variant and GCK variants associated with hyperinsulinemic hypoglycemia reveal two distinct mechanisms of enzyme activation. In α-type activation, glucose affinity is increased, the proteolytic susceptibility of the active site loop is suppressed and the (1)H-(13)C heteronuclear multiple quantum coherence (HMQC) spectrum of (13)C-Ile-labeled enzyme resembles the glucose-bound state. In β-type activation, glucose affinity is largely unchanged, proteolytic susceptibility of the loop is enhanced, and the (1)H-(13)C HMQC spectrum reveals no perturbation in ensemble structure. Leveraging both activation mechanisms, we engineer a fully noncooperative GCK variant, whose functional properties are indistinguishable from other hexokinase isozymes, and which displays a 100-fold increase in catalytic efficiency over wild-type GCK. This work elucidates specific structural features responsible for generating allostery in a monomeric enzyme and suggests a general strategy for engineering cooperativity into proteins that lack the structural framework typical of traditional allosteric systems.
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14
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Martinez JA, Larion M, Conejo MS, Porter CM, Miller BG. Role of connecting loop I in catalysis and allosteric regulation of human glucokinase. Protein Sci 2014; 23:915-22. [PMID: 24723372 DOI: 10.1002/pro.2473] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Revised: 04/07/2014] [Accepted: 04/07/2014] [Indexed: 11/09/2022]
Abstract
Glucokinase (GCK, hexokinase IV) is a monomeric enzyme with a single glucose binding site that displays steady-state kinetic cooperativity, a functional characteristic that affords allosteric regulation of GCK activity. Structural evidence suggests that connecting loop I, comprised of residues 47-71, facilitates cooperativity by dictating the rate and scope of motions between the large and small domains of GCK. Here we investigate the impact of varying the length and amino acid sequence of connecting loop I upon GCK cooperativity. We find that sequential, single amino acid deletions from the C-terminus of connecting loop I cause systematic decreases in cooperativity. Deleting up to two loop residues leaves the kcat value unchanged; however, removing three or more residues reduces kcat by 1000-fold. In contrast, the glucose K0.5 and KD values are unaffected by shortening the connecting loop by up to six residues. Substituting alanine or glycine for proline-66, which adopts a cis conformation in some GCK crystal structures, does not alter cooperativity, indicating that cis/trans isomerization of this loop residue does not govern slow conformational reorganizations linked to hysteresis. Replacing connecting loop I with the corresponding loop sequence from the catalytic domain of the noncooperative isozyme human hexokinase I (HK-I) eliminates cooperativity without impacting the kcat and glucose K0.5 values. Our results indicate that catalytic turnover requires a minimal length of connecting loop I, whereas the loop has little impact upon the binding affinity of GCK for glucose. We propose a model in which the primary structure of connecting loop I affects cooperativity by influencing conformational dynamics, without altering the equilibrium distribution of GCK conformations.
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Affiliation(s)
- Juliana A Martinez
- Department of Chemistry and Biochemistry, 4005 Chemical Sciences Laboratory, Florida State University, Tallahassee, Florida, 32306-4390
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15
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Bowler JM, Hervert KL, Kearley ML, Miller BG. Small-Molecule Allosteric Activation of Human Glucokinase in the Absence of Glucose. ACS Med Chem Lett 2013; 4. [PMID: 24294411 DOI: 10.1021/ml400061x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Synthetic allosteric activators of human glucokinase are receiving considerable attention as potential diabetes therapeutic agents. Although their mechanism of action is not fully understood, structural studies suggest that activator association requires prior formation of a binary enzyme-glucose complex. Here, we demonstrate that three previously described activators associate with glucokinase in a glucose-independent fashion. Transient-state kinetic assays reveal a lag in enzyme progress curves that is systematically reduced when the enzyme is preincubated with activators. Isothermal titration calorimetry demonstrates that activator binding is enthalpically driven for all three compounds, whereas the entropic changes accompanying activator binding can be favorable or unfavorable. Viscosity variation experiments indicate that the kcat value of glucokinase is almost fully limited by product release, both in the presence and absence of activators, suggesting that activators impact a step preceding product release. The observation of glucose-independent allosteric activation of glucokinase has important implications for the refinement of future diabetes therapeutics and for the mechanism of kinetic cooperativity of mammalian glucokinase.
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Affiliation(s)
- Joseph M. Bowler
- Department of Chemistry and
Biochemistry, Florida State University,
Tallahassee, Florida 32306, United States
| | - Katherine L. Hervert
- Department of Chemistry, Ohio Wesleyan University, Delaware, Ohio 43015, United
States
| | - Mark L. Kearley
- Department of Chemistry and
Biochemistry, Florida State University,
Tallahassee, Florida 32306, United States
| | - Brian G. Miller
- Department of Chemistry and
Biochemistry, Florida State University,
Tallahassee, Florida 32306, United States
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16
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Beck T, Miller BG. Structural basis for regulation of human glucokinase by glucokinase regulatory protein. Biochemistry 2013; 52:6232-9. [PMID: 23957911 DOI: 10.1021/bi400838t] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Glucokinase (GCK) is responsible for maintaining glucose homeostasis in the human body. Dysfunction or misregulation of GCK causes hyperinsulinemia, hypertriglyceridemia, and type 2 diabetes. In the liver, GCK is regulated by interaction with the glucokinase regulatory protein (GKRP), a 68 kDa polypeptide that functions as a competitive inhibitor of glucose binding to GCK. Formation of the mammalian GCK-GKRP complex is stimulated by fructose 6-phosphate and antagonized by fructose 1-phosphate. Here we report the crystal structure of the mammalian GCK-GKRP complex in the presence of fructose 6-phosphate at a resolution of 3.50 Å. The interaction interface, which totals 2060 Å(2) of buried surface area, is characterized by a small number of polar contacts and substantial hydrophobic interactions. The structure of the complex reveals the molecular basis of disease states associated with impaired regulation of GCK by GKRP. It also offers insight into the modulation of complex stability by sugar phosphates. The atomic description of the mammalian GCK-GKRP complex provides a framework for the development of novel diabetes therapeutic agents that disrupt this critical macromolecular regulatory unit.
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Affiliation(s)
- Tobias Beck
- Laboratory of Organic Chemistry, ETH Zürich , Zürich CH-8093, Switzerland
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17
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Henquin JC, Sempoux C, Marchandise J, Godecharles S, Guiot Y, Nenquin M, Rahier J. Congenital hyperinsulinism caused by hexokinase I expression or glucokinase-activating mutation in a subset of β-cells. Diabetes 2013; 62:1689-96. [PMID: 23274908 PMCID: PMC3636634 DOI: 10.2337/db12-1414] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Congenital hyperinsulinism causes persistent hypoglycemia in neonates and infants. Most often, uncontrolled insulin secretion (IS) results from a lack of functional K(ATP) channels in all β-cells or only in β-cells within a resectable focal lesion. In more rare cases, without K(ATP) channel mutations, hyperfunctional islets are confined within few lobules, whereas hypofunctional islets are present throughout the pancreas. They also can be cured by selective partial pancreatectomy; however, unlike those with a K(ATP) focal lesion, they show clinical sensitivity to diazoxide. Here, we characterized in vitro IS by fragments of pathological and adjacent normal pancreas from six such cases. Responses of normal pancreas were unremarkable. In pathological region, IS was elevated at 1 mmol/L and was further increased by 15 mmol/L glucose. Diazoxide suppressed IS and tolbutamide antagonized the inhibition. The most conspicuous anomaly was a large stimulation of IS by 1 mmol/L glucose. In five of six cases, immunohistochemistry revealed undue presence of low-K(m) hexokinase-I in β-cells of hyperfunctional islets only. In one case, an activating mutation of glucokinase (I211F) was found in pathological islets only. Both abnormalities, attributed to somatic genetic events, may account for inappropriate IS at low glucose levels by a subset of β-cells. They represent a novel cause of focal congenital hyperinsulinism.
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Affiliation(s)
- Jean-Claude Henquin
- Unit of Endocrinology and Metabolism, University of Louvain, Faculty of Medicine, Brussels, Belgium.
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18
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Larion M, Salinas RK, Bruschweiler-Li L, Miller BG, Brüschweiler R. Order-disorder transitions govern kinetic cooperativity and allostery of monomeric human glucokinase. PLoS Biol 2012; 10:e1001452. [PMID: 23271955 PMCID: PMC3525530 DOI: 10.1371/journal.pbio.1001452] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2012] [Accepted: 11/07/2012] [Indexed: 11/18/2022] Open
Abstract
Analysis of the functional dynamics of human glucokinase reveals that a slow order-disorder transition governs monomeric kinetic cooperativity in response to glucose concentrations. Glucokinase (GCK) catalyzes the rate-limiting step of glucose catabolism in the pancreas, where it functions as the body's principal glucose sensor. GCK dysfunction leads to several potentially fatal diseases including maturity–onset diabetes of the young type II (MODY-II) and persistent hypoglycemic hyperinsulinemia of infancy (PHHI). GCK maintains glucose homeostasis by displaying a sigmoidal kinetic response to increasing blood glucose levels. This positive cooperativity is unique because the enzyme functions exclusively as a monomer and possesses only a single glucose binding site. Despite nearly a half century of research, the mechanistic basis for GCK's homotropic allostery remains unresolved. Here we explain GCK cooperativity in terms of large-scale, glucose-mediated disorder–order transitions using 17 isotopically labeled isoleucine methyl groups and three tryptophan side chains as sensitive nuclear magnetic resonance (NMR) probes. We find that the small domain of unliganded GCK is intrinsically disordered and samples a broad conformational ensemble. We also demonstrate that small-molecule diabetes therapeutic agents and hyperinsulinemia-associated GCK mutations share a strikingly similar activation mechanism, characterized by a population shift toward a more narrow, well-ordered ensemble resembling the glucose-bound conformation. Our results support a model in which GCK generates its cooperative kinetic response at low glucose concentrations by using a millisecond disorder–order cycle of the small domain as a “time-delay loop,” which is bypassed at high glucose concentrations, providing a unique mechanism to allosterically regulate the activity of human GCK under physiological conditions. Glucokinase is a key metabolic enzyme that functions as the body's principal glucose sensor. Glucokinase regulates the rate at which insulin is secreted by the pancreas by using a unique but poorly understood cooperative kinetic response to increasing glucose concentrations. The physiological importance of this enzyme is underlined by the fact that mutations in the glucokinase gene lead to maturity-onset diabetes of the young type II (MODY II), permanent neonatal diabetes mellitus (PNDM), and hypoglycemic hyperinsulinemia of infancy (HI). In this study, we use cutting-edge high-resolution nuclear magnetic resonance methods to understand how the kinetic properties of glucokinase contribute to glucose homeostasis. We also seek to understand how a class of recently discovered small-molecule drugs, which hold promise as therapeutics for type 2 diabetes, function to enhance glucokinase activity. Our results suggest that glucokinase samples a range of conformational states in the absence of glucose. However, in the presence of glucose or a small-molecule activator, the enzyme population shifts towards a more narrow, well-structured ensemble of states. Our findings provide a new model for glucokinase cooperative kinetics, which relies on a slow order–disorder transition in response to glucose concentrations. These results also reveal a universal mechanism of glucokinase activation, which may inform the development of new antidiabetic agents.
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Affiliation(s)
- Mioara Larion
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida, United States of America
| | - Roberto Kopke Salinas
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida, United States of America
- Institute of Chemistry, University of São Paulo, São Paulo, Brazil
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida, United States of America
| | - Lei Bruschweiler-Li
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida, United States of America
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida, United States of America
| | - Brian G. Miller
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida, United States of America
- * E-mail: (BGM); (RB)
| | - Rafael Brüschweiler
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida, United States of America
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida, United States of America
- * E-mail: (BGM); (RB)
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19
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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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20
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Beer NL, van de Bunt M, Colclough K, Lukacs C, Arundel P, Chik CL, Grimsby J, Ellard S, Gloyn AL. Discovery of a novel site regulating glucokinase activity following characterization of a new mutation causing hyperinsulinemic hypoglycemia in humans. J Biol Chem 2011; 286:19118-26. [PMID: 21454522 DOI: 10.1074/jbc.m111.223362] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Type 2 diabetes is a global problem, and current ineffective therapeutic strategies pave the way for novel treatments like small molecular activators targeting glucokinase (GCK). GCK activity is fundamental to beta cell and hepatocyte glucose metabolism, and heterozygous activating and inactivating GCK mutations cause hyperinsulinemic hypoglycemia (HH) and maturity onset diabetes of the young (MODY) respectively. Over 600 naturally occurring inactivating mutations have been reported, whereas only 13 activating mutations are documented to date. We report two novel GCK HH mutations (V389L and T103S) at residues where MODY mutations also occur (V389D and T103I). Using recombinant proteins with in vitro assays, we demonstrated that both HH mutants had a greater relative activity index than wild type (6.0 for V389L, 8.4 for T103S, and 1.0 for wild type). This was driven by an increased affinity for glucose (S(0.5), 3.3 ± 0.1 and 3.5 ± 0.1 mm, respectively) versus wild type (7.5 ± 0.1 mm). Correspondingly, the V389D and T103I MODY mutants had markedly reduced relative activity indexes (<0.1). T103I had an altered affinity for glucose (S(0.5), 24.9 ± 0.6 mm), whereas V389D also exhibited a reduced affinity for ATP and decreased catalysis rate (S(0.5), 78.6 ± 4.5 mm; ATP(K(m)), 1.5 ± 0.1 mm; K(cat), 10.3 ± 1.1s(-1)) compared with wild type (ATP(K(m)), 0.4 ± <0.1; K(cat), 62.9 ± 1.2). Both Thr-103 mutants showed reduced inhibition by the endogenous hepatic inhibitor glucokinase regulatory protein. Molecular modeling demonstrated that Thr-103 maps to the allosteric activator site, whereas Val-389 is located remotely to this position and all other previously reported activating mutations, highlighting α-helix 11 as a novel region regulating GCK activity. Our data suggest that pharmacological manipulation of GCK activity at locations distal from the allosteric activator site is possible.
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Affiliation(s)
- Nicola L Beer
- Oxford Centre for Diabetes Endocrinology and Metabolism, University of Oxford, Oxford OX3 7LJ, United Kingdom
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Hussain K. Mutations in pancreatic ß-cell Glucokinase as a cause of hyperinsulinaemic hypoglycaemia and neonatal diabetes mellitus. Rev Endocr Metab Disord 2010; 11:179-83. [PMID: 20878480 DOI: 10.1007/s11154-010-9147-z] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Glucokinase is a key enzyme involved in regulating insulin secretion from the pancreatic ß-cell. The unique role of glucokinase in human glucose physiology is illustrated by the fact that genetic mutations in glucokinase can either cause hyperglycaemia or hypoglycaemia. Heterozygous inactivating mutations in glucokinase cause maturity-onset diabetes of the young (MODY), homozygous inactivating in glucokinase mutations result in permanent neonatal diabetes whereas heterozygous activating glucokinase mutations cause hyperinsulinaemic hypoglycaemia.
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Affiliation(s)
- Khalid Hussain
- Clinical and Molecular Genetics Unit, The Developmental Endocrinology Research Group, Institute of Child Health, Hospital for Children NHS Trust, University College London, Great Ormond Street, London, UK.
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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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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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