Differential regulation of endothelial exocytosis of P-selectin and von Willebrand factor by protease-activated receptors and cAMP.
Thrombin-mediated endothelial-cell release of von Willebrand factor (VWF) and P-selectin functionally links protease-activated receptors (PARs) to thrombosis and inflammation. VWF release can be stimulated by both Ca2+ and cAMP, and, although both VWF and P-selectin are found in Weibel-Palade bodies (WPBs), we found that their release could be differentially regulated. In these studies, human umbilical vein endothelial cells stimulated with cAMP or PAR2-AP led to a delayed release of VWF and significantly less P-selectin release compared with histamine, thrombin, or PAR1-AP. Dose-response studies revealed that PAR2-AP was significantly less efficacious in promoting the release of P-selectin compared with VWF. PAR2-AP-induced robust stimulation of intracellular Ca2+ coupled with a significantly greater inhibitory effect of calcium chelation on release of VWF compared with cell-surface expression of P-selectin, suggests an additional Ca2+-independent pathway involved in release of P-selectin. PAR2-AP failed to increase global cAMP levels; however, inhibition of protein kinase A led to a significant attenuation of PAR2-AP-mediated release of VWF. Confocal microscopy studies revealed that PAR2 and forskolin caused preferential release of a population of Weibel-Palade bodies (WPBs) consisting of only VWF. Thus, WPBs are pharmacologically and morphologically heterogeneous, and distinct granule populations are susceptible to differential regulation.
Cleator
John H
JH
Department of Pharmacology, Vanderbilt University Medical Center, 442 Robinson Research Bldg, 23rd Ave South @ Pierce, Nashville, TN 37232-6600, USA.
Zhu
Wen Qin
WQ
Vaughan
Douglas E
DE
Hamm
Heidi E
HE
D020013:Calcium Signaling / Q000502:physiology*; D002460:Cell Line; D000242:Cyclic AMP / Q000502:physiology*; D004730:Endothelium, Vascular / Q000166:cytology / Q000502:physiology*; D005089:Exocytosis; D006801:Humans; D007700:Kinetics; D019007:P-Selectin / Q000378:metabolism*; D010447:Peptide Hydrolases / Q000378:metabolism*; D021381:Protein Transport; D044463:Receptor, PAR-1 / Q000378:metabolism*; D044464:Receptor, PAR-2 / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*; D013917:Thrombin / Q000494:pharmacology; D014471:Umbilical Veins; D014841:von Willebrand Factor / Q000378:metabolism*
D019007:P-Selectin; D044463:Receptor, PAR-1; D044464:Receptor, PAR-2; D011956:Receptors, Cell Surface; D014841:von Willebrand Factor; D000242:Cyclic AMP; D010447:Peptide Hydrolases; D013917:Thrombin