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Glucokinase expression is regulated by glucose through O-GlcNAc glycosylation. Biochem Biophys Res Commun 2016 09 16;478(2):942-8

Date

08/16/2016

Pubmed ID

27520373

DOI

10.1016/j.bbrc.2016.08.056

Scopus ID

2-s2.0-84995554965   17 Citations

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 I?-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 inA vivo and inA vitro results demonstrate that GCK expression is regulated by nutrient-sensing O-GlcNAc cycling in liver.

Author List

Baldini SF, Steenackers A, Olivier-Van Stichelen S, Mir AM, Mortuaire M, Lefebvre T, Guinez C

Author

Stephanie Olivier-Van Stichelen PhD Assistant Professor in the Biochemistry department at Medical College of Wisconsin




MESH terms used to index this publication - Major topics in bold

Acetylglucosamine
Animals
Enzyme Stability
Fasting
Glucokinase
Glucose
Glycosylation
Hep G2 Cells
Humans
Liver
Male
Mice, Inbred C57BL
Mice, Obese
Models, Biological
N-Acetylglucosaminyltransferases
beta-N-Acetylhexosaminidases