Dynamic glucose uptake, storage, and release by human microvascular endothelial cells
We followed radioactive and fluorescent glucose derivatives in human microvascular endothelial cells (HAMEC). [3H]-2-DG entered via GLUT1/3 and 20% incorporated into glycogen. Glycogenolysis and 2-DG-6-phosphate provided glucose that exited cells via GLUT3. 2-NBDG revealed a parallel endocytic proce...
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Veröffentlicht in: | Molecular biology of the cell 2022-10, Vol.33 (12), p.1 |
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Sprache: | eng |
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Zusammenfassung: | We followed radioactive and fluorescent glucose derivatives in human microvascular endothelial cells (HAMEC). [3H]-2-DG entered via GLUT1/3 and 20% incorporated into glycogen. Glycogenolysis and 2-DG-6-phosphate provided glucose that exited cells via GLUT3. 2-NBDG revealed a parallel endocytic process evincing complex glucose handling by HAMEC.
Endothelia determine blood-to-tissue solute delivery, yet glucose transit is poorly understood. To illuminate mechanisms, we tracked [
3
H]-2-deoxyglucose (2-DG) in human adipose-tissue microvascular endothelial cells. 2-DG uptake was largely facilitated by the glucose transporters GLUT1 and GLUT3. Once in the cytosol, >80% of 2-DG became phosphorylated and ∼20% incorporated into glycogen, suggesting that transported glucose is readily accessible to cytosolic enzymes. Interestingly, a fraction of intracellular 2-DG was released over time (15–20% over 30 min) with slower kinetics than for uptake, involving GLUT3. In contrast to intracellular 2-DG, the released 2-DG was largely unphosphorylated. Glucose release involved endoplasmic reticulum–resident translocases/phosphatases and was stimulated by adrenaline, consistent with participation of glycogenolysis and glucose dephosphorylation. Surprisingly, the fluorescent glucose derivative 2-NBD-glucose (2-NBDG) entered cells largely via fluid phase endocytosis and exited by recycling. 2-NBDG uptake was insensitive to GLUT1/GLUT3 inhibition, suggesting poor influx across membranes. 2-NBDG recycling, but not 2-DG efflux, was sensitive to N-ethyl maleimide. In sum, by utilizing radioactive and fluorescent glucose derivatives, we identified two parallel routes of entry: uptake into the cytosol through dedicated glucose transporters and endocytosis. This reveals the complex glucose handling by endothelial cells that may contribute to glucose delivery to tissues. |
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ISSN: | 1059-1524 1939-4586 |
DOI: | 10.1091/mbc.E22-04-0146 |