title: Glucokinase expression is regulated by glucose through O-GlcNAc glycosylation.
abstract: Blood glucose fluctuates with the fasting-feeding cycle. One of the liver's functions is to maintain blood glucose concentrations within a physiological range. Glucokinase (GCK) or hexokinase IV, is the main enzyme that regulates the flux and the use of glucose in the liver leading to a compensation of hyperglycemia. In hepatocytes, GCK catalyzes the phosphorylation of glucose into glucose-6-phosphate. This critical enzymatic reaction is determinant for the metabolism of glucose in the liver which includes glycogen synthesis, glycolysis, lipogenesis and gluconeogenesis. In liver, simultaneous increase of glucose and insulin enhances GCK activity and gene expression, changes its subcellular location and interaction with regulatory proteins. The post-translational O-linked β-N-acetylglucosaminylation (O-GlcNAcylation) acts as a glucose-sensitive modification and is believed to take part in hepatic glucose sensing by modifying key regulatory proteins. Therefore, we aimed to determine whether GCK is modified by O-GlcNAcylation in the liver of mice and investigated the role that this modification plays in regulating GCK protein expression. We demonstrated that endogenous GCK expression correlated with O-GlcNAc levels in the pathophysiological model ob/ob mice. More specifically, in response to the pharmacological inhibition of O-GlcNAcase (OGA) contents of GCK increased. Using the GlcNAc specific lectin succinylated-WGA and click chemistry labeling approaches, we demonstrated that GCK is modified by O-GlcNAcylation. Further, we demonstrated that siRNA-mediated Ogt knock-down not only decreases O-GlcNAc content but also GCK protein level. Altogether, our in vivo and in vitro results demonstrate that GCK expression is regulated by nutrient-sensing O-GlcNAc cycling in liver.
authors: Univ. Lille, CNRS, UMR 8576- UGSF- Unité de Glycobiologie Structurale et Fonctionnelle, F 59000, Lille, France.
authors: Steffi F
authors: SF
authors: Baldini
authors: Univ. Lille, CNRS, UMR 8576- UGSF- Unité de Glycobiologie Structurale et Fonctionnelle, F 59000, Lille, France.
authors: Agata
authors: A
authors: Steenackers
authors: Univ. Lille, CNRS, UMR 8576- UGSF- Unité de Glycobiologie Structurale et Fonctionnelle, F 59000, Lille, France.
authors: Stéphanie
authors: S
authors: Olivier-Van Stichelen
authors: Univ. Lille, CNRS, UMR 8576- UGSF- Unité de Glycobiologie Structurale et Fonctionnelle, F 59000, Lille, France.
authors: Anne-Marie
authors: AM
authors: Mir
authors: Univ. Lille, CNRS, UMR 8576- UGSF- Unité de Glycobiologie Structurale et Fonctionnelle, F 59000, Lille, France.
authors: Marlène
authors: M
authors: Mortuaire
authors: Univ. Lille, CNRS, UMR 8576- UGSF- Unité de Glycobiologie Structurale et Fonctionnelle, F 59000, Lille, France.
authors: Tony
authors: T
authors: Lefebvre
authors: Univ. Lille, CNRS, UMR 8576- UGSF- Unité de Glycobiologie Structurale et Fonctionnelle, F 59000, Lille, France. Electronic address: celine.guinez@univ-lille1.fr.
authors: Céline
authors: C
authors: Guinez
mesh_terms: D000117:Acetylglucosamine / Q000378:metabolism*; D000818:Animals; D004795:Enzyme Stability; D005215:Fasting; D005941:Glucokinase / Q000378:metabolism*; D005947:Glucose / Q000494:pharmacology*; D006031:Glycosylation / Q000187:drug effects; D056945:Hep G2 Cells; D006801:Humans; D008099:Liver / Q000201:enzymology; D008297:Male; D008810:Mice, Inbred C57BL; D008820:Mice, Obese; D008954:Models, Biological; D017351:N-Acetylglucosaminyltransferases / Q000378:metabolism; D001619:beta-N-Acetylhexosaminidases / Q000378:metabolism
chemical_list: D017351:N-Acetylglucosaminyltransferases; D005941:Glucokinase; C110628:hexosaminidase C; D001619:beta-N-Acetylhexosaminidases; D005947:Glucose; D000117:Acetylglucosamine
keywords: Glucokinase; Glucose metabolism; Liver; Mouse; O-GlcNAcylation; siOGT