title: The high molecular weight form of endothelial cell von Willebrand factor is released by the regulated pathway.
abstract: We have previously reported that two forms of von Willebrand factor (vWf) exist in cultured human umbilical vein endothelial cells: a high molecular weight (HMW) form that is released and can be proteolytically cleaved into a series of plasma-like multimers, and a non-secreted low molecular weight (LMW) form. In this study, the mode of vWf release and the relationship between the two forms were examined. As determined by two-dimensional analysis as well as by immunoreactivity with an antibody to the propolypeptide, the LMW form of endothelial cell vWf consisted of a 260 kD pro-vWf polypeptide, while the HMW form consisted of a 225 kD mature polypeptide. Only the 260 kD polypeptide was susceptible to digestion with endoglycosidase H. Release of the HMW form into the culture media was accompanied by a decrease in cellular vWf. Treatment of endothelial cells with cycloheximide or tunicamycin caused a decrease in the LMW form but did not affect the secretion of the HMW form. These results suggest that two pools of vWf exist in endothelial cells--a LMW form of pro-vWf in the endoplasmic reticulum and a HMW form of mature vWf in the storage compartment. Released vWf derives only from the storage pool.
authors.affiliation: Division of Hematology, Montefiore Medical Center/Albert Einstein College of Medicine, Bronx, New York 10467.
authors.forename: H M
authors.initials: HM
authors.lastname: Tsai
authors.forename: R L
authors.initials: RL
authors.lastname: Nagel
authors.forename: V B
authors.initials: VB
authors.lastname: Hatcher
authors.forename: A C
authors.initials: AC
authors.lastname: Seaton
authors.forename: I I
authors.initials: II
authors.lastname: Sussman
mesh_terms: D002478:Cells, Cultured; D003513:Cycloheximide / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D046911:Macromolecular Substances; D008970:Molecular Weight; D010455:Peptides / Q000032:analysis; D014415:Tunicamycin / Q000494:pharmacology; D014841:von Willebrand Factor / Q000737:chemistry / Q000378:metabolism*
chemical_list: D046911:Macromolecular Substances; D010455:Peptides; D014841:von Willebrand Factor; D014415:Tunicamycin; D003513:Cycloheximide