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Ceprian M, Juntas-Morales R, Campbell G, Walther-Louvier U, Rivier F, Camu W, Esselin F, Echaniz-Laguna A, Stojkovic T, Bouhour F, Latour P, Tricaud N. The Hexokinase 1 5'-UTR Mutation in Charcot-Marie-Tooth 4G Disease Alters Hexokinase 1 Binding to Voltage-Dependent Anion Channel-1 and Leads to Dysfunctional Mitochondrial Calcium Buffering. Int J Mol Sci 2024; 25:4364. [PMID: 38673950 PMCID: PMC11050395 DOI: 10.3390/ijms25084364] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2024] [Revised: 03/31/2024] [Accepted: 04/04/2024] [Indexed: 04/28/2024] Open
Abstract
Demyelinating Charcot-Marie-Tooth 4G (CMT4G) results from a recessive mutation in the 5'UTR region of the Hexokinase 1 (HK1) gene. HK participates in mitochondrial calcium homeostasis by binding to the Voltage-Dependent Anion Channel (VDAC), through its N-terminal porin-binding domain. Our hypothesis is that CMT4G mutation results in a broken interaction between mutant HK1 and VDAC, disturbing mitochondrial calcium homeostasis. We studied a cohort of 25 CMT4G patients recruited in the French gypsy population. The disease was characterized by a childhood onset, an intermediate demyelinating pattern, and a significant phenotype leading to becoming wheelchair-bound by the fifth decade of life. Co-IP and PLA studies indicated a strong decreased interaction between VDAC and HK1 in the patients' PBMCs and sural nerve. We observed that either wild-type HK1 expression or a peptide comprising the 15 aa of the N-terminal wild-type HK1 administration decreased mitochondrial calcium release in HEK293 cells. However, mutated CMT4G HK1 or the 15 aa of the mutated HK1 was unable to block mitochondrial calcium release. Taken together, these data show that the CMT4G-induced modification of the HK1 N-terminus disrupts HK1-VDAC interaction. This alters mitochondrial calcium buffering that has been shown to be critical for myelin sheath maintenance.
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Affiliation(s)
- Maria Ceprian
- Institute for Neuroscience of Montpellier (INM), University Montpellier, INSERM, 34091 Montpellier, France; (M.C.)
| | - Raul Juntas-Morales
- Clinique du Motoneurone, Explorations Fonctionnelles Neurologiques, Service de Neurologie, Hôpital Universitaire Gui de Chauliac, 34295 Montpellier, France; (R.J.-M.); (W.C.); (F.E.)
- Unidad Neuromuscular, Servicio de Neurologia, Hospital Universitario Vall d’Hebron, 08035 Barcelona, Spain
| | - Graham Campbell
- Institute for Neuroscience of Montpellier (INM), University Montpellier, INSERM, 34091 Montpellier, France; (M.C.)
| | - Ulrike Walther-Louvier
- Service de Neuropediatrie, Hôpital Universitaire Gui de Chauliac, 34295 Montpellier, France; (U.W.-L.); (F.R.)
| | - François Rivier
- Service de Neuropediatrie, Hôpital Universitaire Gui de Chauliac, 34295 Montpellier, France; (U.W.-L.); (F.R.)
| | - William Camu
- Clinique du Motoneurone, Explorations Fonctionnelles Neurologiques, Service de Neurologie, Hôpital Universitaire Gui de Chauliac, 34295 Montpellier, France; (R.J.-M.); (W.C.); (F.E.)
| | - Florence Esselin
- Clinique du Motoneurone, Explorations Fonctionnelles Neurologiques, Service de Neurologie, Hôpital Universitaire Gui de Chauliac, 34295 Montpellier, France; (R.J.-M.); (W.C.); (F.E.)
| | - Andoni Echaniz-Laguna
- AEL, Department of Neurology, Bicetre University Hospital, Paris Saclay University, 94270 Paris, France;
| | - Tanya Stojkovic
- Service de Neurologie, Hôpital Universitaire Pitié-Salpêtrière, 75013 Paris, France;
| | - Françoise Bouhour
- Service de Neurologie, Hôpital Universitaire Lyon, 69500 Lyon, France;
| | - Philippe Latour
- Centre de Biologie Est Biochimie et Biologie Moléculaire, Hospices Civils de Lyon, 69677 Bron, France;
| | - Nicolas Tricaud
- Institute for Neuroscience of Montpellier (INM), University Montpellier, INSERM, 34091 Montpellier, France; (M.C.)
- I-Stem, UEVE/UPS U861, INSERM, AFM, 91100 Corbeil-Essonnes, France
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Diet evolution of carnivorous and herbivorous mammals in Laurasiatheria. BMC Ecol Evol 2022; 22:82. [PMID: 35729512 PMCID: PMC9210794 DOI: 10.1186/s12862-022-02033-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Accepted: 12/09/2021] [Indexed: 11/15/2022] Open
Abstract
Background Laurasiatheria contains taxa with diverse diets, while the molecular basis and evolutionary history underlying their dietary diversification are less clear. Results In this study, we used the recently developed molecular phyloecological approach to examine the adaptive evolution of digestive system-related genes across both carnivorous and herbivorous mammals within Laurasiatheria. Our results show an intensified selection of fat and/or protein utilization across all examined carnivorous lineages, which is consistent with their high-protein and high-fat diets. Intriguingly, for herbivorous lineages (ungulates), which have a high-carbohydrate diet, they show a similar selection pattern as that of carnivorous lineages. Our results suggest that for the ungulates, which have a specialized digestive system, the selection intensity of their digestive system-related genes does not necessarily reflect loads of the nutrient components in their diets but appears to be positively related to the loads of the nutrient components that are capable of being directly utilized by the herbivores themselves. Based on these findings, we reconstructed the dietary evolution within Laurasiatheria, and our results reveal the dominant carnivory during the early diversification of Laurasiatheria. In particular, our results suggest that the ancestral bats and the common ancestor of ruminants and cetaceans may be carnivorous as well. We also found evidence of the convergent evolution of one fat utilization-related gene, APOB, across carnivorous taxa. Conclusions Our molecular phyloecological results suggest that digestive system-related genes can be used to determine the molecular basis of diet differentiations and to reconstruct ancestral diets. Supplementary Information The online version contains supplementary material available at 10.1186/s12862-022-02033-6.
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Dongerdiye R, Jagadeesh S, Suresh B, Rajendran A, Devendra R, Warang P, Kedar PS. Novel pathogenic variant c.2714C>A (p. Thr905Lys) in the HK1 gene causing severe haemolytic anaemia with developmental delay in an Indian family. J Clin Pathol 2020; 74:620-624. [PMID: 33361148 DOI: 10.1136/jclinpath-2020-206960] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Revised: 12/01/2020] [Accepted: 12/01/2020] [Indexed: 11/04/2022]
Abstract
Hexokinase (EC 2.7.1.1, Adenosine Tri Phosphate (ATP): D-hexose-6-phosphotransferase) is a crucial regulatory enzyme of the glycolytic pathway (Embden-Meyerhof pathway). Hexokinase deficiency is associated with chronic non-spherocytic haemolytic anaemia (HA) with some exceptional cases showing psychomotor/mental retardation and fetus death. The proband is a four-and-half-year-old female child born of a four-degree consanguineous marriage hailing from South India with autosomal recessive congenital HA associated with developmental delay. She was well till 3 months of her age post an episode of diarrhoea when she was noted to be severely anaemic and requiring regular transfusions. The common causes of HA, haemoglobinopathies, red cell membranopathies and common red cell enzymopathies (G6PD, GPI, PK and P5N) were ruled out. Targeted analysis of whole exome sequencing (WES) using an insilico gene panel for hereditary anaemia was performed to identify pathogenic variants in the patient. Next-generation sequencing revealed a novel homozygous variant in hexokinase gene c.2714C>A (p. Thr905Lys) in exon-18. The pathogenic nature of the variant p. Thr905Lys in the HK1 gene was confirmed collectively by biochemical and molecular studies. Insilico analysis (PolyPhen-2, Provean, Mutation Taster) predicted the variant to be severe disease causing. Multiple sequence alignment demonstrated the conservation of p. Thr905 across the species. The impact of the mutation on the protein structure was studied by PyMOL and Swiss Protein databank viewer.
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Affiliation(s)
- Rashmi Dongerdiye
- Hematogenetics, National Institute of Immunohaematology, Mumbai, Maharashtra, India
| | - Sujatha Jagadeesh
- Department of Clinical Genetics and Genetic Counseling Department, MediScan Systems, Chennai, Tamil Nadu, India
| | - Beena Suresh
- Department of Clinical Genetics and Genetic Counseling Department, MediScan Systems, Chennai, Tamil Nadu, India
| | - Aruna Rajendran
- Department of Hematology, Institute of Child Health and Hospital for Children, Chennai, Tamil Nadu, India
| | - Rati Devendra
- Hematogenetics, National Institute of Immunohaematology, Mumbai, Maharashtra, India
| | - Prashant Warang
- Hematogenetics, National Institute of Immunohaematology, Mumbai, Maharashtra, India
| | - Prabhakar S Kedar
- Hematogenetics, National Institute of Immunohaematology, Mumbai, Maharashtra, India
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Molecular characterization of six new cases of red blood cell hexokinase deficiency yields four novel mutations in HK1. Blood Cells Mol Dis 2016; 59:71-6. [DOI: 10.1016/j.bcmd.2016.04.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2016] [Revised: 04/08/2016] [Accepted: 04/10/2016] [Indexed: 11/19/2022]
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Krasnov GS, Dmitriev AA, Sadritdinova AF, Fedorova MS, Snezhkina AV, Melnikova NV, Poteryakhina AV, Nyushko KM, Belyakov MM, Kaprin AD, Zaretsky AR, Kudryavtseva AV. Evaluation of hexokinase gene expression in colorectal cancer using bioinformatics tools. Biophysics (Nagoya-shi) 2015. [DOI: 10.1134/s0006350915060172] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
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Hu CJ, Song G, Huang W, Liu GZ, Deng CW, Zeng HP, Wang L, Zhang FC, Zhang X, Jeong JS, Blackshaw S, Jiang LZ, Zhu H, Wu L, Li YZ. Identification of new autoantigens for primary biliary cirrhosis using human proteome microarrays. Mol Cell Proteomics 2012; 11:669-80. [PMID: 22647870 DOI: 10.1074/mcp.m111.015529] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Primary biliary cirrhosis (PBC) is a chronic cholestatic liver disease of unknown etiology and is considered to be an autoimmune disease. Autoantibodies are important tools for accurate diagnosis of PBC. Here, we employed serum profiling analysis using a human proteome microarray composed of about 17,000 full-length unique proteins and identified 23 proteins that correlated with PBC. To validate these results, we fabricated a PBC-focused microarray with 21 of these newly identified candidates and nine additional known PBC antigens. By screening the PBC microarrays with additional cohorts of 191 PBC patients and 321 controls (43 autoimmune hepatitis, 55 hepatitis B virus, 31 hepatitis C virus, 48 rheumatoid arthritis, 45 systematic lupus erythematosus, 49 systemic sclerosis, and 50 healthy), six proteins were confirmed as novel PBC autoantigens with high sensitivities and specificities, including hexokinase-1 (isoforms I and II), Kelch-like protein 7, Kelch-like protein 12, zinc finger and BTB domain-containing protein 2, and eukaryotic translation initiation factor 2C, subunit 1. To facilitate clinical diagnosis, we developed ELISA for Kelch-like protein 12 and zinc finger and BTB domain-containing protein 2 and tested large cohorts (297 PBC and 637 control sera) to confirm the sensitivities and specificities observed in the microarray-based assays. In conclusion, our research showed that a strategy using high content protein microarray combined with a smaller but more focused protein microarray can effectively identify and validate novel PBC-specific autoantigens and has the capacity to be translated to clinical diagnosis by means of an ELISA-based method.
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Affiliation(s)
- Chao-Jun Hu
- Department of Rheumatology and Clinical Immunology, Peking Union Medical College Hospital, Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing 100032, China
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Gjesing AP, Nielsen AA, Brandslund I, Christensen C, Sandbæk A, Jørgensen T, Witte D, Bonnefond A, Froguel P, Hansen T, Pedersen O. Studies of a genetic variant in HK1 in relation to quantitative metabolic traits and to the prevalence of type 2 diabetes. BMC MEDICAL GENETICS 2011; 12:99. [PMID: 21781351 PMCID: PMC3161933 DOI: 10.1186/1471-2350-12-99] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/18/2011] [Accepted: 07/25/2011] [Indexed: 11/10/2022]
Abstract
BACKGROUND Single nucleotide polymorphisms (SNPs) within the gene encoding Hexokinase 1 (HK1) are associated with changes in glycated haemoglobin (HbA1c) levels. Our aim was to investigate the effect of HK1 rs7072268 on measures of glucose- and lipid-metabolism in a Danish non-diabetic population and combine the outcome of these analyses in a meta-analysis with previously published results. Furthermore, our aim was to perform a type 2 diabetes case-control analysis and meta-analysis with two previous case-control studies. METHODS SNP rs7072268 was genotyped in 9,724 Danes. The quantitative trait study included 5,604 non-diabetic individuals from the Inter99 cohort. The case-control study included 4,449 glucose tolerant individuals and 3,398 patients with type 2 diabetes. Meta-analyses on quantitative traits included 24,560 Caucasian individuals and 30,802 individuals were included in the combined analysis of present and previous type 2 diabetes case-control studies. RESULTS Using an additive model, we confirmed that the T-allele of rs7072268 associates with increased HbA1c of 0.6% (CI: 0.4-0.9), p = 3*10-7 per allele. The same allele associated with an increased area under the curve (AUC) for glucose of 5.0 mmol/l*min (0.1-10.0), p = 0.045 following an oral glucose tolerance test (OGTT) and increased fasting levels of cholesterol of 0.06 mmol/l (0.03-1.0), p = 0.001 and triglycerides of 2.0% (0.2-3.8), p = 0.03 per allele in the same study sample of non-diabetic individuals from the Inter99 cohort. However, the T-allele did not show any association with estimates of insulin release or insulin sensitivity neither in Inter99 nor in combined analyses. The prevalence of type 2 diabetes was increased among carriers of the rs7072268 T-allele both in the Danish study-population with an OR of 1.11 (1.02-1.21) and in a meta-analysis including the two additional sample sets with an OR of 1.06 (1.02-1.11). However, after Bonferroni correction the T-allele only remained associated to HbA1c and fasting cholesterol. CONCLUSIONS The present study provides suggestive evidence of an association of the rs7072268 T-allele in HK1 with increased AUC glucose following an OGTT in non-diabetic individuals and a nominal association with type 2 diabetes prior to Bonferroni correction. The latter was confirmed in combined analyses involving 16,445 cases and 14,357 control subjects.
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Affiliation(s)
- Anette P Gjesing
- The Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health Sciences, University of Copenhagen, Universitetsparken 1-3, 2100 Copenhagen, Denmark
| | - Aneta A Nielsen
- Department of Clinical Biochemistry, Vejle Hospital, Kabbeltoft 25, 7100 Vejle, Denmark
| | - Ivan Brandslund
- Department of Clinical Biochemistry, Vejle Hospital, Kabbeltoft 25, 7100 Vejle, Denmark
- Institute of Regional Health Research, University of Southern Denmark, J.B. Winsloews Vej 9B, 5000 Odense, Denmark
| | - Cramer Christensen
- Department of Internal Medicine and Endocrinology, Vejle Hospital, Kabbeltoft 25, 7100 Vejle, Denmark
| | - Anneli Sandbæk
- Department of General Practice, University of Aarhus, Vennelyst Boulevard 6, 8000 Aarhus, Denmark
| | - Torben Jørgensen
- Research Centre for Prevention and Health, Glostrup University Hospital, Nordre Ringvej, 2600 Glostrup, Denmark
- Faculty of Health Science, University of Copenhagen, Blegdamsvej, 2200 Copenhagen, Denmark
| | - Daniel Witte
- Steno Diabetes Center, Niels Steensens Vej 2, 2800 Gentofte, Denmark
| | - Amélie Bonnefond
- CNRS-UMR-8199, Lille Pasteur Institute, Univ Lille Nord de France, rue du Pr. Calmette, 59000 Lille, France
| | - Phillippe Froguel
- CNRS-UMR-8199, Lille Pasteur Institute, Univ Lille Nord de France, rue du Pr. Calmette, 59000 Lille, France
- Department of Genomics of Common Disease, School of Public Health, Imperial College London, Hammersmith Hospital, Du Cane Rd., London W12 0NN, UK
| | - Torben Hansen
- The Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health Sciences, University of Copenhagen, Universitetsparken 1-3, 2100 Copenhagen, Denmark
- Faculty of Health Sciences, University of Southern Denmark, J.B. Winsloews Vej 19, 5000 Odense, Denmark
| | - Oluf Pedersen
- The Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health Sciences, University of Copenhagen, Universitetsparken 1-3, 2100 Copenhagen, Denmark
- Hagedorn Research Institute, Niels Steensens Vej 1, 2820 Gentofte, Denmark
- Institute of Biomedical Science, Faculty of Health Sciences, University of Copenhagen, Blegdamsvej 3, 2200 Copenhagen, Denmark
- Faculty of Health Sciences, University of Aarhus, Aarhus, Denmark
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Andreoni F, Serafini G, Laguardia ME, Magnani M. Bovine hexokinase type I: full-length cDNA sequence and characterisation of the recombinant enzyme. Mol Cell Biochem 2005; 268:9-18. [PMID: 15724432 DOI: 10.1007/s11010-005-1846-5] [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: 11/30/2022]
Abstract
This study reports the revised and full-length cDNA sequence of bovine hexokinase type I obtained from bovine brain. Since dissimilarities have been observed between the published bovine hexokinase type I coding sequence (GenBank accession no. M65140) (Genomics 11: 1014-1024, 1991) and an analysed portion of bovine hexokinase type I gene, the entire open reading frame was re-sequenced and the ends of cDNA isolated by rapid amplification of cDNA ends. The coding sequences, when compared with the published bovine hexokinase type I, contained a large number of mismatches that lead to changes in the resulting amino acid sequence. The revisions result in a hexokinase type I cDNA of 3619 bp that encodes a protein of 917 amino acids highly homologous to human hexokinase type I. The expression of the recombinant full-length enzyme demonstrated that it was a catalytically active hexokinase. When characterised for its kinetic and regulatory properties, it displayed the same affinity for glucose and MgATP as the human hexokinase type I and was inhibited by glucose 6-phosphate competitively versus MgATP. The production of the N- and C-terminal recombinant halves of the enzyme followed by comparison with the full-length hexokinase indicated that the catalytic activity is located in the C-terminal domain.
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Abstract
Hexokinase (HK) deficiency is a rare red cell enzyme deficiency associated with hereditary non-spherocytic haemolytic anaemia; to date, only 17 affected families have been reported. Human HK has four major isozymes, each of which is encoded by a separate gene. Recent studies have shown that both ubiquitously expressed type I HK (HK-I) and erythroid-specific HK-R are expressed in erythrocytes, and that these isozymes are encoded by the single HK-I gene. The human HK-I gene has 19 exons, the HK-I and HK-R transcripts being produced by using two distinct promoters. Thus, the first and second exons are specifically utilized for the erythroid-specific HK-R and ubiquitously expressed HK-I isozymes respectively. So far, only two HK variants have been analysed at the molecular level. Since the human HK-I crystal structure has recently been elucidated, the molecular analysis of the HK variants will be useful for discussing the structure-function relationship of the enzyme.
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Affiliation(s)
- H Kanno
- Department of Biochemistry, Nihon University School of Medicine, Tokyo, Japan
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Rosano C, Sabini E, Rizzi M, Deriu D, Murshudov G, Bianchi M, Serafini G, Magnani M, Bolognesi M. Binding of non-catalytic ATP to human hexokinase I highlights the structural components for enzyme-membrane association control. Structure 1999; 7:1427-37. [PMID: 10574795 DOI: 10.1016/s0969-2126(00)80032-5] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
BACKGROUND Hexokinase I sets the pace of glycolysis in the brain, catalyzing the ATP-dependent phosphorylation of glucose. The catalytic properties of hexokinase I are dependent on product inhibition as well as on the action of phosphate. In vivo, a large fraction of hexokinase I is bound to the mitochondrial outer membrane, where the enzyme adopts a tetrameric assembly. The mitochondrion-bound hexokinase I is believed to optimize the ATP/ADP exchange between glucose phosphorylation and the mitochondrial oxidative phosphorylation reactions. RESULTS The crystal structure of human hexokinase I has been determined at 2.25 A resolution. The overall structure of the enzyme is in keeping with the closed conformation previously observed in yeast hexokinase. One molecule of the ATP analogue AMP-PNP is bound to each N-terminal domain of the dimeric enzyme in a surface cleft, showing specific interactions with the nucleotide, and localized positive electrostatic potential. The molecular symmetry brings the two bound AMP-PNP molecules, at the centre of two extended surface regions, to a common side of the dimeric hexokinase I molecule. CONCLUSIONS The binding of AMP-PNP to a protein site separated from the catalytic centre of human hexokinase I can be related to the role played by some nucleotides in dissociating the enzyme from the mitochondrial membrane, and helps in defining the molecular regions of hexokinase I that are expected to be in contact with the mitochondrion. The structural information presented here is in keeping with monoclonal antibody mapping of the free and mitochondrion-bound forms of the enzyme, and with sequence analysis of hexokinases that differ in their mitochondria binding properties.
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Affiliation(s)
- C Rosano
- Dipartimento di Fisica - INFM, Centro Biotecnologie Avanzate - IST, Universita' di Genova, Genova, 10. I-16132, Italy
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Bianchi M, Serafini G, Bartolucci E, Giammarini C, Magnani M. Enzymatic properties of overexpressed human hexokinase fragments. Mol Cell Biochem 1998; 189:185-93. [PMID: 9879670 DOI: 10.1023/a:1006962217495] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Full-length hexokinase (HK; ATP: D-hexose 6-phosphotransferase, EC 2.7.1.1), a truncate form of the enzyme lacking the first 11 amino acids (HK-11aa) and the 50 kDa C-terminal half ('mini'-HK) containing the catalytic domain, were overexpressed and purified to homogeneity to investigate the influence of the N-terminal region of human hexokinase type I (HK) on its regulatory properties. All forms of the enzyme are catalytically active with the HK-11aa being the most active. All the forms of HK showed the same affinity for glucose and MgATP and were also inhibited by glucose 6-phosphate (Glc 6-P) competitively vs. MgATP with similar Kis (28.5-37 microM). Glucose 1,6-bisphosphate (Glc 1,6-P2) was also a strong inhibitor of all HKs without significant differences among the different truncate forms of the enzyme (Kis 49.5-59 microM). At low concentrations (0-3 mM), Pi was able to reverse the sugar phosphate inhibition of the full-length HK and HK-11aa but not of the 'mini'-HK. In contrast, at high concentrations Pi was an inhibitor of all the hexokinases investigated. These findings confirm that Pi has a low affinity binding site on the C-terminal of HK while counteracts glucose 6-phosphate inhibition by binding to or requiring the N-terminal half of the enzyme. The first 11 N-terminal amino acids influence the specific activity of HK but are unable to affect the kinetic properties investigated.
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Affiliation(s)
- M Bianchi
- Institute of Biological Chemistry G Fornaini, University of Urbino, Italy
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Bianchi M, Serafini G, Bartolucci E, Palma F, Magnani M. Expression, purification, and characterization of a recombinant erythroid-specific hexokinase isozyme. Blood Cells Mol Dis 1998; 24:401-11. [PMID: 9851893 DOI: 10.1006/bcmd.1998.0208] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Hexokinase type I (HK I; ATP: D-hexose 6-phosphotransferase, EC 2.7.1.1), the predominant glucose-phosphorylating enzyme in red blood cells, exists in human erythrocytes in multiple molecular forms that differ in isoelectric point and are separable by ion-exchange chromatography. The major forms, designated HK Ia, Ib and Ic, have similar kinetic properties but are characterized by different age-dependent decay and different intracellular distribution in reticulocytes. HK Ib, which elutes between HK I and HK II in the DEAE ion-exchange chromatography, appears to be unique to RBCs and different from any other hexokinase isozyme previously described. Indeed, Murakami and Piomelli recently reported the presence of a specific HK isozyme (named HKr) expressed in K562 cells and in human reticulocytes and, moreover, the resolution of the human HK I gene structure provided the direct evidence of an erythroid-specific exon 1. To further investigate the microheterogeneity of HK I in human RBCs we established a prokaryotic expression system for the HKr isozyme, using the pET plasmid, inducible with IPTG. The recombinant HKr, expressed in bacterial cells as a catalytically active enzyme, was purified to homogeneity by a combination of DEAE ionexchange chromatography followed by hydrophobic interaction chromatography and dye-ligand affinity chromatography. The kinetic and chromatographic properties of the homogeneous recombinant HKr suggest that this erythroid-specific HK isozyme in fact corresponds to the HK isoform previously described in human RBCs and referred to as HK Ib.
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Affiliation(s)
- M Bianchi
- Institute of Biological Chemistry "G. Fornaini", University of Urbino, Italy
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Mori C, Nakamura N, Welch JE, Gotoh H, Goulding EH, Fujioka M, Eddy EM. Mouse spermatogenic cell-specific type 1 hexokinase (mHk1-s) transcripts are expressed by alternative splicing from the mHk1 gene and the HK1-S protein is localized mainly in the sperm tail. Mol Reprod Dev 1998; 49:374-85. [PMID: 9508088 DOI: 10.1002/(sici)1098-2795(199804)49:4<374::aid-mrd4>3.0.co;2-k] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Unique type 1 hexokinase (HK1) mRNAs are present in mouse spermatogenic cells (mHk1-s). They encode a spermatogenic cell-specific sequence region (SSR) but not the porin-binding domain (PBD) necessary for HK1 binding to porin on the outer mitochondrial membrane. This study determined the origin of the multiple Hk1-s transcripts in mouse spermatogenic cells and verified that they are translated in mouse spermatogenic cells. It also showed that a single mHk1 gene encodes the mHk1 transcripts of somatic cells and the mHk1-sa and mHk1-sb transcripts of spermatogenic cells, that alternative exons are used during mHk1 gene expression in mouse spermatogenic cells, and that mHK1-S is translated in mouse spermatogenic cells and is localized mainly with the fibrous sheath in the tail region, not with the mitochondria in the midpiece of mouse sperm.
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Affiliation(s)
- C Mori
- Department of Anatomy and Developmental Biology, Faculty of Medicine, Kyoto University, Japan.
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