title: Intracellular trafficking of factor VIII to von Willebrand factor storage granules.
abstract: In plasma, von Willebrand factor (vWf) associates with Factor VIII (FVIII); however, the site at which these proteins first interact has not been defined. Administration of 1-desamino-8-D-arginine vasopressin (DDAVP) causes a rapid, concomitant elevation in plasma levels of both vWf and FVIII, suggesting the existence of a DDAVP-releasable storage pool for both proteins. To determine whether vWf and FVIII can associate intracellularly and colocalize to storage vesicles, we transfected AtT-20 cells with vWf and FVIII expression plasmids. FVIII alone was not detectable within storage granules; however, transfection of vWf cDNA into the same cell caused FVIII to alter its intracellular trafficking and to undergo granular storage, colocalizing to the vWf-containing granules. In contrast, colocalization of FVIII was not observed when these cells were transfected with plasmids encoding defective FVIII-binding vWf mutants. Transfection of bovine endothelial cells with FVIII further demonstrated vesicular storage of FVIII with vWf in Weibel-Palade bodies. Since gene therapy of hemophilia A may ultimately target endothelium or hematopoietic stem cells, the interaction between vWf and FVIII within a secretory cell is important. Thus, vWf can alter the intracellular trafficking of FVIII from a constitutive to a regulated secretory pathway, thereby producing an intracellular storage pool of both proteins.
authors.affiliation: Blood Research Institute, The Blood Center of Southeastern Wisconsin, Milwaukee, Wisconsin 53201-2178, USA.
authors.forename: J B
authors.initials: JB
authors.lastname: Rosenberg
authors.forename: P A
authors.initials: PA
authors.lastname: Foster
authors.forename: R J
authors.initials: RJ
authors.lastname: Kaufman
authors.forename: E A
authors.initials: EA
authors.lastname: Vokac
authors.forename: M
authors.initials: M
authors.lastname: Moussalli
authors.forename: P A
authors.initials: PA
authors.lastname: Kroner
authors.forename: R R
authors.initials: RR
authors.lastname: Montgomery
mesh_terms: D000818:Animals; D016466:CHO Cells; D019556:COS Cells; D002417:Cattle; D002478:Cells, Cultured; D006224:Cricetinae; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism; D005169:Factor VIII / Q000235:genetics / Q000378:metabolism*; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D007424:Intracellular Fluid / Q000378:metabolism; D051379:Mice; D018832:Molecular Chaperones; D011499:Protein Processing, Post-Translational; D014407:Tumor Cells, Cultured; D014841:von Willebrand Factor / Q000235:genetics / Q000378:metabolism*
chemical_list: D018832:Molecular Chaperones; D014841:von Willebrand Factor; D005169:Factor VIII