This Article Full Text Full Text (PDF) Data Supplement Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by de Leeuw, H. P. J. C. Articles by Voorberg, J. Search for Related Content PubMed PubMed Citation Articles by de Leeuw, H. P. J. C. Articles by Voorberg, J. Pubmed/NCBI databases Substance via MeSH Related Collections Cell biology/structural biology Cell signalling/signal transduction Signal transduction Endothelium/vascular type/nitric oxide

(Arteriosclerosis, Thrombosis, and Vascular Biology. 2001;21:899.)
© 2001 American Heart Association, Inc.

Vascular Biology

Small GTP-Binding Protein Ral Modulates Regulated Exocytosis of von Willebrand Factor by Endothelial Cells

Hubert P. J. C. de Leeuw; Mar Fernandez-Borja; Eric A. J. Reits; Thalia Romani de Wit; Pauline M. Wijers-Koster; Peter L. Hordijk; Jacques Neefjes; Jan A. van Mourik; Jan Voorberg

From the Departments of Plasma Proteins and Blood Coagulation (H.P.J.C.d.L., T.R.d.W., P.M.W.-K., J.A.v.M., J.V.) and the Department of Experimental Immunohaematology (P.L.H.), CLB; the Division of Tumor Biology (M.F.-B., E.A.J.R., J.N.), The Netherlands Cancer Institute; and the Department of Vascular Medicine (J.A.v.M.), Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands.

Correspondence to Jan Voorberg, PhD, Department of Plasma Proteins, CLB, Plesmanlaan 125, 1066 CX Amsterdam, Netherlands. E-mail J_Voorberg{at}clb.nl

Abstract—Weibel-Palade bodies are endothelial cell–specific organelles, which contain von Willebrand factor (vWF), P-selectin, and several other proteins. Recently, we found that the small GTP-binding protein Ral is present in a subcellular fraction containing Weibel-Palade bodies. In the present study, we investigated whether Ral is involved in the regulated exocytosis of Weibel-Palade bodies. Activation of endothelial cells by thrombin resulted in transient cycling of Ral from its inactive GDP-bound to its active GTP-bound state, which coincided with release of vWF. Ral activation and exocytosis of Weibel-Palade bodies were inhibited by incubation with trifluoperazine, an inhibitor of calmodulin, before thrombin stimulation. Functional involvement of Ral in exocytosis was further investigated by the expression of constitutively active and dominant-negative Ral variants in primary endothelial cells. Introduction of active Ral G23V resulted in the disappearance of Weibel-Palade bodies from endothelial cells. In contrast, the expression of the dominant-negative Ral S28N did not affect the amount of Weibel-Palade bodies in transfected cells. These results indicate that Ral is involved in regulated exocytosis of Weibel-Palade bodies by endothelial cells.

Key Words: von Willebrand factor • Weibel-Palade bodies • Ral • GTP-binding protein • endothelial cells

This article has been cited by other articles:

				M. G. Rondaij, R. Bierings, E. L. van Agtmaal, K. A. Gijzen, E. Sellink, A. Kragt, S. S. G. Ferguson, K. Mertens, M. J. Hannah, J. A. van Mourik, et al. Guanine exchange factor RalGDS mediates exocytosis of Weibel-Palade bodies from endothelial cells Blood, July 1, 2008; 112(1): 56 - 63. [Abstract] [Full Text] [PDF]

				M. G. Rondaij, R. Bierings, A. Kragt, J. A. van Mourik, and J. Voorberg Dynamics and Plasticity of Weibel-Palade Bodies in Endothelial Cells Arterioscler Thromb Vasc Biol, May 1, 2006; 26(5): 1002 - 1007. [Abstract] [Full Text] [PDF]

				I. Oynebraten, N. Barois, K. Hagelsteen, F.-E. Johansen, O. Bakke, and G. Haraldsen Characterization of a Novel Chemokine-Containing Storage Granule in Endothelial Cells: Evidence for Preferential Exocytosis Mediated by Protein Kinase A and Diacylglycerol J. Immunol., October 15, 2005; 175(8): 5358 - 5369. [Abstract] [Full Text] [PDF]

				M. G. Rondaij, E. Sellink, K. A. Gijzen, J. P. ten Klooster, P. L. Hordijk, J. A. van Mourik, and J. Voorberg Small GTP-Binding Protein Ral Is Involved in cAMP-Mediated Release of von Willebrand Factor From Endothelial Cells Arterioscler Thromb Vasc Biol, July 1, 2004; 24(7): 1315 - 1320. [Abstract] [Full Text] [PDF]

				T. Minami, A. Sugiyama, S.-Q. Wu, R. Abid, T. Kodama, and W. C. Aird Thrombin and Phenotypic Modulation of the Endothelium Arterioscler Thromb Vasc Biol, January 1, 2004; 24(1): 41 - 53. [Abstract] [Full Text] [PDF]

				L. H. K. Lim and E. M. Wagner Airway Distension Promotes Leukocyte Recruitment in Rat Tracheal Circulation Am. J. Respir. Crit. Care Med., November 1, 2003; 168(9): 1068 - 1074. [Abstract] [Full Text] [PDF]

				T. Romani de Wit, M. G. Rondaij, P. L. Hordijk, J. Voorberg, and J. A. van Mourik Real-Time Imaging of the Dynamics and Secretory Behavior of Weibel-Palade Bodies Arterioscler Thromb Vasc Biol, May 1, 2003; 23(5): 755 - 761. [Abstract] [Full Text] [PDF]