Post-translational Regulation of Glucokinase in Hypothalamic Neurons

Abstract

Glucose-sensing tissues utilize glucokinase (GCK), the activity of which is rate-limiting for glucose metabolism, to sense and, consequently, counteract deviations from glucose homeostasis. Post-translational regulation of GCK is well defined in the liver and the pancreas, and is critical for the maintenance of glucose homeostasis; yet, post- translational regulation of GCK in hypothalamic neurons, which play a central role in maintaining glucose homeostasis, remains relatively unexplored. Here, we use a hypothalamically-derived, glucose-sensing GT1-7 neuronal cell line to provide evidence of a receptor-driven, ER Ca2+-mediated S-nitrosylation and activation of GCK. Strategic pharmacological manipulations were paired with the assessment of GCK activity, done by either measuring NAD(P)H autofluorescence while raising extracellular glucose, or through expression of a homotransfer FRET GCK biosensor. Further, a biotin-switch assay was used to confirm the presence of GCK S-nitrosylation. This work illustrates a central mechanism of post-translational GCK regulation, which may underlie metabolic signal integration in the hypothalamus and may contribute to the pathology of diabetes.