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.

Insulin-Like Growth Factor–Binding Protein-7 as a Biomarker of Diastolic Dysfunction and Functional Capacity in Heart Failure With Preserved Ejection Fraction

“…Higher levels of IGFBP7 may therefore accelerate cellular senescence, potentially contributing to aging of the myocardium (20). IGFBP7 has been localized to the Weibel-Palade bodies (storage organelles) of endothelial cells (21). Furthermore, IGFBP7 has also been associated with collagen deposition (22) and may therefore also be linked with myocardial fibrosis.…”

STXBP1 promotes Weibel-Palade body exocytosis through its interaction with the Rab27A effector Slp4-a

“…10 The presence of angiopoietin-2 and insulin-like growth factor-binding protein 7 in WPBs points toward a critical role for the organelle in regulation of angiogenesis. [11][12][13] The precise composition of mediators stored in WPBs depends crucially on the physical, mechanical, and chemical signals in the local microenvironment; for example, targeting of eotaxin-3, IL-8, and IL-6 has been observed in response to pro-inflammatory mediators such as IL-1b or IL-4, 5,7,14,15 whereas the inclusion of angiopoietin-2 is modulated under conditions that mimic shear stress. 16 Exocytosis of WPBs is triggered by a wide range of physiological secretagogues that trigger Ca 21 -and cyclic adenosine monophosphate (cAMP)-dependent signaling pathways, such as histamine and thrombin or vasopressin and epinephrine, respectively.…”

von Willebrand factor biosynthesis, secretion, and clearance: connecting the far ends

“…on May 9, 2018. by guest www.bloodjournal.org From subset of endothelial cells also FVIII. [47][48][49] Incorporation of some of these residents (like interleukin-8 and tissue-type plasminogen activator) results from a random inclusion process. 50 In contrast, other coresidents like P-selectin, galectins, and osteoprotegerin have been shown to directly interact with VWF, which may facilitate their targeting to the WPBs.…”