Functional Organization of Glycolytic Metabolon on Mitochondria

Abstract

Glucose, the primary cellular energy source, is metabolized through glycolysis initiated by the rate-limiting enzyme Hexokinase (HK). In energy-demanding tissues like the brain, HK1 is the dominant isoform, primarily localized on mitochondria, crucial for efficient glycolysis-oxidative phosphorylation coupling and optimal energy generation. This study unveils a unique mechanism regulating HK1 activity, glycolysis, and the dynamics of mitochondrial coupling, mediated by the metabolic sensor enzyme O-GlcNAc transferase (OGT). OGT catalyzes reversible O-GlcNAcylation, a post-translational modification, influenced by glucose flux. Elevated OGT activity induces dynamic O-GlcNAcylation of HK1's regulatory domain, subsequently promoting the assembly of the glycolytic metabolon on the outer mitochondrial membrane. This modification enhances HK1's mitochondrial association, orchestrating glycolytic and mitochondrial ATP production. Mutations in HK1's O-GlcNAcylation site reduce ATP generation, affecting synaptic functions in neurons. The study uncovers a novel pathway that bridges neuronal metabolism and mitochondrial function via OGT and the formation of the glycolytic metabolon, offering new prospects for tackling metabolic and neurological disorders.

FluxNorm: Toolbox for metabolic flux assay normalization byin situcell counting

“…Ara-C-containing medium was replaced with fresh neuron maintenance medium at 5 DIV. The primary neuron cultures were maintained for 12-15 days in vitro by replacing one-third of the culture medium with a fresh medium every three days 14,15 . For respirometry measurements, the neuronal maintenance medium was exchanged with XF DMEM Base Medium (pH 7.4) with no phenol red (Agilent) supplemented with 5 mM glucose and 1 mM pyruvate.…”

Roles of O-GlcNAcylation in Mitochondrial Homeostasis and Cardiovascular Diseases

“…This modification enhances the mitochondrial binding of HK1, coordinating glycolysis and mitochondrial ATP production. Mutations in the O-GlcNAcylation site of HK1 reduce ATP production [10]. He et al reported that the IDH2 protein was highly expressed in colorectal cancer tissues (CRC) and correlated with poor survival in CRC patients.…”

“…The adaptive regulation of energy disturbances in the O-GlcNAc cycle has been shown to be crucial for maintaining mitochondrial homeostasis [5,6]. The imbalance of O-GlcNAcylation in mitochondria is related to various mitochondrial dysfunctions, such as abnormal mitochondrial dynamics, decreased mitochondrial biosynthesis, disruption of electron transport chains (ECTs), oxidative stress and the calcium paradox and mitophagy, as well as the activation of mitochondrial apoptosis pathways [10][11][12][13].…”