Glucose-1,6-bisphosphate: A new gatekeeper of cerebral mitochondrial pyruvate uptake

• Main Authors: Motahareh Solina Safari (Author), Priska Woerl (Author), Carolin Garmsiri (Author), Dido Weber (Author), Marcel Kwiatkowski (Author), Madlen Hotze (Author), Louisa Kuenkel (Author), Luisa Lang (Author), Matthias Erlacher (Author), Ellen Gelpi (Author), Johannes A. Hainfellner (Author), Gottfried Baier (Author), Gabriele Baier-Bitterlich (Author), Stephanie zur Nedden (Author)
• Format: Book
• Published: Elsevier, 2024-10-01T00:00:00Z.
• Subjects: article
• Online Access: Connect to this object online.

Summary

Objective: Glucose-1,6-bisphosphate (G-1,6-BP), a byproduct of glycolysis that is synthesized by phosphoglucomutase 2 like 1 (PGM2L1), is particularly abundant in neurons. G-1,6-BP is sensitive to the glycolytic flux, due to its dependence on 1,3-bisphosphoglycerate as phosphate donor, and the energy state, due to its degradation by inosine monophosphate-activated phosphomannomutase 1. Since the exact role of this metabolite remains unclear, our aim was to elucidate the specific function of G-1,6-BP in the brain. Methods: The effect of PGM2L1 on neuronal post-ischemic viability was assessed by siRNA-mediated knockdown of PGM2L1 in primary mouse neurons. Acute mouse brain slices were used to correlate the reduction in G-1,6-BP upon ischemia to changes in carbon metabolism by 13C6-glucose tracing. A drug affinity responsive target stability assay was used to test if G-1,6-BP interacts with the mitochondrial pyruvate carrier (MPC) subunits in mouse brain protein extracts. Human embryonic kidney cells expressing a MPC bioluminescence resonance energy transfer sensor were used to analyze how PGM2L1 overexpression affects MPC activity. The effect of G-1,6-BP on mitochondrial pyruvate uptake and oxygen consumption rates was analyzed in isolated mouse brain mitochondria. PGM2L1 and a predicted upstream kinase were overexpressed in a human neuroblastoma cell line and G-1,6-BP levels were measured. Results: We found that G-1,6-BP in mouse brain slices was quickly degraded upon ischemia and reperfusion. Knockdown of PGM2L1 in mouse neurons reduced post-ischemic viability, indicating that PGM2L1 plays a neuroprotective role. The reduction in G-1,6-BP upon ischemia was not accompanied by alterations in glycolytic rates but we did see a reduced 13C6-glucose incorporation into citrate, suggesting a potential role in mitochondrial pyruvate uptake or metabolism. Indeed, G-1,6-BP interacted with both MPC subunits and overexpression of PGM2L1 increased MPC activity. G-1,6-BP, at concentrations found in the brain, enhanced mitochondrial pyruvate uptake and pyruvate-induced oxygen consumption rates. Overexpression of a predicted upstream kinase inhibited PGM2L1 activity, showing that besides metabolism, also signaling pathways can regulate G-1,6-BP levels. Conclusions: We provide evidence that G-1,6-BP positively regulates mitochondrial pyruvate uptake and post-ischemic neuronal viability. These compelling data reveal a novel mechanism by which neurons can couple glycolysis-derived pyruvate to the tricarboxylic acid cycle. This process is sensitive to the glycolytic flux, the cell's energetic state, and upstream signaling cascades, offering many regulatory means to fine-tune this critical metabolic step.

Item Description

2212-8778
10.1016/j.molmet.2024.102018