Neuronal activity-driven O-GlcNAcylation promotes mitochondrial plasticity

Abstract

Neuronal activity is an energy-intensive process that is largely sustained by instantaneous fuel utilization and ATP synthesis. However, how neurons couple ATP synthesis rate to fuel availability is largely unknown. Here, we demonstrate that the metabolic sensor enzyme O-GlcNAc transferase regulates neuronal activity-driven mitochondrial bioenergetics. We show that neuronal activity upregulates O-GlcNAcylation mainly in mitochondria. Mitochondrial O-GlcNAcylation is promoted by activity-driven fuel consumption, which allows neurons to compensate for high energy expenditure based on fuel availability. To determine the proteins that are responsible for these adjustments, we mapped the mitochondrial O-GlcNAcome of neurons. Finally, we determine that neurons fail to meet activity-driven metabolic demand when O-GlcNAcylation dynamics are prevented. Our findings suggest that O-GlcNAcylation provides a fuel-dependent feedforward control mechanism in neurons to optimize mitochondrial performance based on neuronal activity. This mechanism thereby couples neuronal metabolism to mitochondrial bioenergetics and plays a key role in sustaining energy homeostasis.

Mitochondrial Ca2+efflux controls neuronal metabolism and long-term memory across species

“…During neuronal activity, synapses synthesize the exact levels of energy that are consumed during each firing event, without under or overproducing ATP. However, while work of several laboratories has identified how mitochondrial metabolism is upregulated on demand in firing neurons to preserve the metabolic integrity of synapses 6,10,24,28,55,80 , the importance and the molecular identity of mechanisms slowing down mitochondrial metabolism after firing have remained elusive.…”

Functional Organization of Glycolytic Metabolon on Mitochondria

“…In response to periods of high activity neurons increase in both surface glucose transporter levels and glucose uptake—aligning with the intensified demand for ATP 32,33 . This dynamic is underscored by findings that synaptic activity boosts glucose consumption by a median of 1.9-fold 56 , also promotes O-GlcNAcylation 40 . Intriguingly, a study indicates that in a resting adult mouse brain, hexokinase operates at a mere 3% of its maximum potential, suggesting an available 33-fold upswing in activity 36 .…”

“…ATP production rates was calculated according to protocol provided by Agilent. Basal and maximal respiration (OCR) as well glycolytic capacity (ECAR) values were plotted after cell count normalization with FluxNorm Normalization with cell count was done by FluxNorm 40 .…”

“…Within this complex regulatory landscape, O-GlcNAcylation emerges as a crucial modulator 34 . In contrast to other forms of protein glycosylation, certain O-GlcNAcylation sites are dynamically regulated, undergoing rapid addition or removal in response to changes in the cellular state, such as excitatory neuronal stimuli 39,40 . Conversely, others sites primarily fulfill structural roles and exhibit slower turnover 41 .…”

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.…”