title: Proteomic screen identifies IGFBP7 as a novel component of endothelial cell-specific Weibel-Palade bodies.
abstract: Vascular endothelial cells contain unique storage organelles, designated Weibel-Palade bodies (WPBs), that deliver inflammatory and hemostatic mediators to the vascular lumen in response to agonists like thrombin and vasopressin. The main component of WPBs is von Willebrand factor (VWF), a multimeric glycoprotein crucial for platelet plug formation. In addition to VWF, several other components are known to be stored in WPBs, like osteoprotegerin, monocyte chemoattractant protein-1 and angiopoetin-2 (Ang-2). Here, we used an unbiased proteomics approach to identify additional residents of WPBs. Mass spectrometry analysis of purified WPBs revealed the presence of several known components such as VWF, Ang-2, and P-selectin. Thirty-five novel candidate WPB residents were identified that included insulin-like growth factor binding protein-7 (IGFBP7), which has been proposed to regulate angiogenesis. Immunocytochemistry revealed that IGFBP7 is a bona fide WPB component. Cotransfection studies showed that IGFBP7 trafficked to pseudo-WPB in HEK293 cells. Using a series of deletion variants of VWF, we showed that targeting of IGFBP7 to pseudo-WPBs was dependent on the carboxy-terminal D4-C1-C2-C3-CK domains of VWF. IGFBP7 remained attached to ultralarge VWF strings released upon exocytosis of WPBs under flow. The presence of IGFBP7 in WPBs highlights the role of this subcellular compartment in regulation of angiogenesis.
authors.affiliation: Department of Plasma Proteins, Sanquin-AMC Landsteiner Laboratory, Amsterdam, The Netherlands.
authors.forename: Dorothee
authors.initials: D
authors.lastname: van Breevoort
authors.forename: Ellen L
authors.initials: EL
authors.lastname: van Agtmaal
authors.forename: Bieuwke S
authors.initials: BS
authors.lastname: Dragt
authors.forename: Jacqueline Klein
authors.initials: JK
authors.lastname: Gebbinck
authors.forename: Ilze
authors.initials: I
authors.lastname: Dienava-Verdoold
authors.forename: Astrid
authors.initials: A
authors.lastname: Kragt
authors.forename: Ruben
authors.initials: R
authors.lastname: Bierings
authors.forename: Anton J G
authors.initials: AJ
authors.lastname: Horrevoets
authors.forename: Karine M
authors.initials: KM
authors.lastname: Valentijn
authors.forename: Jeroen C
authors.initials: JC
authors.lastname: Eikenboom
authors.forename: Mar
authors.initials: M
authors.lastname: Fernandez-Borja
authors.forename: Alexander B
authors.initials: AB
authors.lastname: Meijer
authors.forename: Jan
authors.initials: J
authors.lastname: Voorberg
mesh_terms: D042783:Endothelial Cells / Q000737:chemistry* / Q000502:physiology; D005089:Exocytosis; D005822:Genetic Vectors; D057809:HEK293 Cells; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D007150:Immunohistochemistry; D018969:Insulin-Like Growth Factor Binding Proteins / Q000737:chemistry*; D013058:Mass Spectrometry; D018919:Neovascularization, Physiologic; D019007:P-Selectin / Q000737:chemistry; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D040901:Proteomics / Q000379:methods*; D014162:Transfection; D020302:Weibel-Palade Bodies / Q000737:chemistry* / Q000502:physiology; D014841:von Willebrand Factor / Q000737:chemistry
chemical_list: D018969:Insulin-Like Growth Factor Binding Proteins; D019007:P-Selectin; C546937:SELP protein, human; C102529:insulin-like growth factor binding protein-related protein 1; D014841:von Willebrand Factor