Endothelial cell confluence regulates Weibel-Palade body formation.
Secretory granules called Weibel-Palade bodies (WPBs) containing Von Willebrand factor (VWF) are characteristic of the mammalian endothelium. We hypothesized that vascular-specific antigens such as VWF are linked to endothelial identity and proliferation in vitro. To test this idea, the cellular accumulation of VWF in WPBs was monitored as a function of cell proliferation, confluence and passage number in human umbilical vein endothelial cells (HUVECs). We found that as passage number increased the percentage of cells containing VWF in WPBs was reduced significantly, whilst the protein was still detected within the secretory pathway at all times. However, the endothelial-specific marker protein, PECAM-1, is present on all cells even when WPBs are absent, indicating partial maintenance of endothelial identity. Biochemical studies show that a significant pool of immature pro-VWF can be detected in sub-confluent HUVECs; however, a larger pool of mature, processed VWF is detected in confluent cells. Newly synthesized VWF must thus be differentially sorted and packaged along the secretory pathway in semi-confluent versus confluent endothelial cells. Our studies thus show that WPB formation is linked to the formation of a confluent endothelial monolayer.
Howell
Gareth J
GJ
School of Biochemistry and Microbiology, University of Leeds, Leeds LS2 9JT, UK.
Herbert
Shane P
SP
Smith
Jennifer M
JM
Mittar
Shweta
S
Ewan
Lorna C
LC
Mohammed
Mudassir
M
Hunter
Alison R
AR
Simpson
Nigel
N
Turner
Anthony J
AJ
Zachary
Ian
I
Walker
John H
JH
Ponnambalam
Sreenivasan
S
D049109:Cell Proliferation; D002478:Cells, Cultured; D004721:Endoplasmic Reticulum / Q000378:metabolism; D042783:Endothelial Cells / Q000166:cytology* / Q000378:metabolism*; D006801:Humans; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D013997:Time Factors; D014470:Umbilical Cord / Q000166:cytology; D020302:Weibel-Palade Bodies / Q000378:metabolism*; D014841:von Willebrand Factor / Q000235:genetics / Q000378:metabolism
D019408:Platelet Endothelial Cell Adhesion Molecule-1; D014841:von Willebrand Factor