The Experts below are selected from a list of 147 Experts worldwide ranked by ideXlab platform
Markku Laakso - One of the best experts on this subject based on the ideXlab platform.
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Hexokinase 2 is required for tumor initiation and maintenance and its systemic deletion is therapeutic in mouse models of cancer
Cancer Cell, 2013Co-Authors: Krushna C Patra, Markku Laakso, Qi Wang, Prashanth T Bhaskar, Luke Miller, Zebin Wang, Will Wheaton, Navdeep S Chandel, William J Muller, Eric L AllenAbstract:Summary Accelerated glucose metabolism is a common feature of cancer cells. Hexokinases catalyze the first committed step of glucose metabolism. Hexokinase 2 (HK2) is expressed at high level in cancer cells, but only in a limited number of normal adult tissues. Using Hk2 conditional knockout mice, we showed that HK2 is required for tumor initiation and maintenance in mouse models of KRas-driven lung cancer, and ErbB2-driven breast cancer, despite continued HK1 expression. Similarly, HK2 ablation inhibits the neoplastic phenotype of human lung and breast cancer cells in vitro and in vivo. Systemic Hk2 deletion is therapeutic in mice bearing lung tumors without adverse physiological consequences. Hk2 deletion in lung cancer cells suppressed glucose-derived ribonucleotides and impaired glutamine-derived carbon utilization in anaplerosis.
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disruption of Hexokinase ii mitochondrial binding blocks ischemic preconditioning and causes rapid cardiac necrosis
Circulation Research, 2011Co-Authors: Kirsten M. Smeele, Richard Southworth, Rongxue Wu, Rianne Nederlof, Alice Warley, Jessica K Nelson, Pepijn Van Horssen, Jeroen P H M Van Den Wijngaard, Sami Heikkinen, Markku LaaksoAbstract:Rationale:Isoforms I and II of the glycolytic enzyme Hexokinase (HKI and HKII) are known to associate with mitochondria. It is unknown whether mitochondria-bound Hexokinase is mandatory for ischemic preconditioning and normal functioning of the intact, beating heart. Objective:We hypothesized that reducing mitochondrial Hexokinase would abrogate ischemic preconditioning and disrupt myocardial function. Methods and Results:Ex vivo perfused HKII+/− hearts exhibited increased cell death after ischemia and reperfusion injury compared with wild-type hearts; however, ischemic preconditioning was unaffected. To investigate acute reductions in mitochondrial HKII levels, wild-type hearts were treated with a TAT control peptide or a TAT-HK peptide that contained the binding motif of HKII to mitochondria, thereby disrupting the mitochondrial HKII association. Mitochondrial Hexokinase was determined by HKI and HKII immunogold labeling and electron microscopy analysis. Low-dose (200 nmol/L) TAT-HK treatment significan...
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Human Hexokinase II: Sequence and Homology to Other Hexokinases
Biochemical and Biophysical Research Communications, 1993Co-Authors: Samir S. Deeb, Mari Malkki, Markku LaaksoAbstract:Abstract The amino acid sequence of human Hexokinase II was deduced from the sequence of cDNA clones isolated from a skeletal muscle library. An open reading frame of 2751 bases encodes a protein of 917 amino acids. The deduced amino acid sequence has 94% identity with rat Hexokinase II but only 72% identity with human Hexokinase type I. In addition to Hexokinase II clones, the human skeletal muscle cDNA library contained at least an equal number of clones of Hexokinase I, the isoform reported to be typically found in kidney and brain. Genetic variation in Hexokinase II could underlie insulin resistance in peripheral tissues and cause non-insulin-dependent diabetes mellitus. The availability of this sequence would facilitate investigating the role of mutations in the HKII gene in the etiology of this disease.
Peter L. Pedersen - One of the best experts on this subject based on the ideXlab platform.
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glucose catabolism in cancer cells amplification of the gene encoding type ii Hexokinase
Cancer Research, 1996Co-Authors: Annette Rempel, Saroj P Mathupala, Constance A Griffin, Anita L Hawkins, Peter L. PedersenAbstract:Hexokinase type II is highly overexpressed in many cancer cells, where it plays a pivotal role in the high glycolytic phenotype. Here we demonstrate by Southern blot analysis and fluorescence in situ hybridization (FISH) that in the rapidly growing rat AS-30D hepatoma cell line, enhanced Hexokinase activity is associated with at least a 5-fold amplification of the type II gene relative to normal hepatocytes. This amplification is located chromosomally, extends to the whole gene, and most likely occurs at the site of the resident gene. No rearrangement of the gene could be detected. Therefore, overexpression of Hexokinase type II in AS-30D hepatoma cells may be based, at least in part, on a stable gene amplification. This is the first report describing the amplification of a Hexokinase gene in a tumor cell line expressing the high glycolytic phenotype.
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Glucose catabolism in brain. Intracellular localization of Hexokinase.
Journal of Biological Chemistry, 1990Co-Authors: David M. Parry, Peter L. PedersenAbstract:Abstract A major energy source in brain is glucose, which is committed to metabolism by Hexokinase (Type I isozyme), an enzyme usually considered to be bound to the outer mitochondrial membrane. In this study, the subcellular location of Hexokinase in brain has been rigorously investigated. Mitochondrial fractions containing Hexokinase (greater than 500 milliunits/mg protein) were prepared by two different procedures, and then subjected to density gradient centrifugation before and after loading with barium phosphate, a technique designed to increase the density of the mitochondria. The gradient distribution patterns of both unloaded and loaded preparations show that brain Hexokinase does not distribute exclusively with mitochondrial marker enzymes. This is particularly evident in the loaded preparations where there is a clear distinction between the peak activities of Hexokinase and mitochondrial markers. The same observation was made when the mitochondrial fraction of either untreated or barium phosphate-loaded mitochondria was subjected to titration with digitonin. In fact, at concentrations of digitonin, which almost completely solubilize marker enzymes for both the inner and outer mitochondrial membranes, a significant fraction of the total Hexokinase remains particulate bound. Electron microscopy confirmed that particulate material is still present under these conditions. Significantly, Hexokinase is released from particulate material only at high concentrations of digitonin which solubilize the associated microsomal marker NADPH-cytochrome c reductase. Glucose 6-phosphate, which is known to release Hexokinase from the brain "mitochondrial fraction" also releases Hexokinase from this unidentified particulate component. These results on brain, a normal glucose utilizing tissue, differ from those obtained previously on highly glycolytic tumor cells where identical subfractionation procedures revealed a strictly outer mitochondrial membrane location for particulate Hexokinase (Parry, D. M., and Pedersen, P. L. (1983) J. Biol. Chem. 258, 10904-10912). It is concluded that in brain, Hexokinase has a greater propensity to localize at nonmitochondrial receptor sites than to those known to be associated with the outer mitochondrial membrane.
Igor Polikarpov - One of the best experts on this subject based on the ideXlab platform.
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Crystal structure of yeast Hexokinase PI in complex with glucose: A classical "induced fit" example revised
Proteins: Structure Function and Genetics, 2008Co-Authors: Paula Kuser, Fabio Cupri, Lucas Bleicher, Igor PolikarpovAbstract:Hexokinase is the first enzyme in the glycolytic pathway that catalyzes the transfer of a phosphoryl group from ATP to glucose to form glucose-6-phosphate and ADP. Two yeast Hexokinase isozymes are known, namely PI and PII. Here we redetermined the crystal structure of yeast Hexokinase PI from Saccharomyces cerevisiae as a complex with its substrate, glucose, and refined it at 2.95 A resolution. Comparison of the holo-PI yeast Hexokinase and apo-Hexokinase structures shows in detail the rigid body domain closure and specific loop movements as glucose binds and sheds more light on structural basis of the "induced fit" mechanism of reaction in the HK enzymatic action. We also performed statistical coupling analysis of the Hexokinase family, which reveals two co-evolved continuous clusters of amino acid residues and shows that the evolutionary coupled amino acid residues are mostly confined to the active site and the hinge region, further supporting the importance of these parts of the protein for the enzymatic catalysis.
Jongseong Jeon - One of the best experts on this subject based on the ideXlab platform.
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structure expression and functional analysis of the Hexokinase gene family in rice oryza sativa l
Planta, 2006Co-Authors: Nayeon Ryoo, Seho Ko, Kihong Jung, Seong Hee Bhoo, Joris Winderickx, Gynheung An, Taeryong Hahn, Jongseong JeonAbstract:Hexokinase (HXK) is a dual-function enzyme that both phosphorylates hexose to form hexose 6−phosphate and plays an important role in sugar sensing and signaling. To investigate the roles of Hexokinases in rice growth and development, we analyzed rice sequence databases and isolated ten rice Hexokinase cDNAs, OsHXK1 (Oryza sativa Hexokinase 1) through OsHXK10. With the exception of the single-exon gene OsHXK1, the OsHXKs all have a highly conserved genomic structure consisting of nine exons and eight introns. Gene expression profiling revealed that OsHXK2 through OsHXK9 are expressed ubiquitously in various organs, whereas OsHXK10 expression is pollen-specific. Sugars induced the expression of three OsHXKs, OsHXK2, OsHXK5, and OsHXK6, in excised leaves, while suppressing OsHXK7 expression in excised leaves and immature seeds. The Hexokinase activity of the OsHXKs was confirmed by functional complementation of the Hexokinase-deficient yeast strain YSH7.4-3C (hxk1, hxk2, glk1). OsHXK4 was able to complement this mutant only after the chloroplast-transit peptide was removed. The subcellular localization of OsHXK4 and OsHXK7, observed with green fluorescent protein (GFP) fusion constructs, indicated that OsHXK4 is a plastid-stroma-targeted Hexokinase while OsHXK7 localizes to the cytosol.
Paula Kuser - One of the best experts on this subject based on the ideXlab platform.
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Crystal structure of yeast Hexokinase PI in complex with glucose: A classical "induced fit" example revised
Proteins: Structure Function and Genetics, 2008Co-Authors: Paula Kuser, Fabio Cupri, Lucas Bleicher, Igor PolikarpovAbstract:Hexokinase is the first enzyme in the glycolytic pathway that catalyzes the transfer of a phosphoryl group from ATP to glucose to form glucose-6-phosphate and ADP. Two yeast Hexokinase isozymes are known, namely PI and PII. Here we redetermined the crystal structure of yeast Hexokinase PI from Saccharomyces cerevisiae as a complex with its substrate, glucose, and refined it at 2.95 A resolution. Comparison of the holo-PI yeast Hexokinase and apo-Hexokinase structures shows in detail the rigid body domain closure and specific loop movements as glucose binds and sheds more light on structural basis of the "induced fit" mechanism of reaction in the HK enzymatic action. We also performed statistical coupling analysis of the Hexokinase family, which reveals two co-evolved continuous clusters of amino acid residues and shows that the evolutionary coupled amino acid residues are mostly confined to the active site and the hinge region, further supporting the importance of these parts of the protein for the enzymatic catalysis.