Thrombin-promoted release of UDP-glucose from human astrocytoma cells
Article first published online: 29 JAN 2009
2008 British Pharmacological Society
British Journal of Pharmacology
Volume 153, Issue 7, pages 1528–1537, April 2008
How to Cite
Kreda, S. M., Seminario-Vidal, L., van Heusden, C. and Lazarowski, E. R. (2008), Thrombin-promoted release of UDP-glucose from human astrocytoma cells. British Journal of Pharmacology, 153: 1528–1537. doi: 10.1038/sj.bjp.0707692
- Issue published online: 29 JAN 2009
- Article first published online: 29 JAN 2009
- (Received September 21, 2007, Revised December 3, 2007, Accepted December 12, 2007)
- nucleotide release;
- 1321N1 human astrocytoma cells;
- P2Y14 receptor
Background and purpose:
The P2Y14 receptor is activated by UDP-sugars, most potently by UDP-glucose, but not by free nucleotides, suggesting that UDP-glucose is the cognate agonist for this receptor. However, evidence for regulated release of UDP-glucose is scarce. In the present study, the occurrence of receptor-promoted release of UDP-glucose was investigated, using 1321N1 human astrocytoma cells.
UDP-glucose release and hydrolysis were measured using HPLC-based techniques. Phospholipase C activation and actin cytoskeleton reorganization were assessed by measuring inositol phosphate formation and fluorescence confocal microscopy, respectively.
Thrombin and the protease-activating receptor-1 (PAR1) peptide TFLLRNPNDK (PAR1-AP) evoked the release of UDP-glucose and ATP, which was accompanied by enhanced inositol phosphate formation. Although carbachol promoted fourfold greater inositol phosphate formation than thrombin, it failed to promote nucleotide release. Thrombin-promoted nucleotide release was inhibited by BAPTA-AM, brefeldin A and cytochalasin D, and was insensitive to Pertussis toxin and PI3-kinase inhibitors. Thrombin, but not carbachol, induced actin cytoskeleton reorganization, a hallmark of Rho activation in 1321N1 cells. However, PAR-promoted UDP-glucose release was not affected by Rho kinase inhibition.
Conclusions and implications:
PAR1-evoked UDP-glucose release reflected a Ca2+-dependent mechanism, engaging additional signalling independently of Gi and Rho kinase activation and requiring a functional actin cytoskeleton and Golgi structures. Our study demonstrates the occurrence of Ca2+-dependent release of UDP-glucose from astrocytoma cells in response to a physiologically relevant stimulus, that is, a G-protein-coupled receptor agonist. Given the presence of P2Y14 receptors in astrocytes, UDP-glucose may have important autocrine/paracrine functions in the brain.
British Journal of Pharmacology (2008) 153, 1528–1537; doi:10.1038/sj.bjp.0707692; published online 21 January 2008