Intracellular localization of factor VIII-related antigen and fibronectin in cultured human endothelial cells: evidence for divergent routes of intracellular translocation.
Cultured human endothelial cells synthesize and secrete both fibronectin and factor VIII-related antigen (VIIIR:Ag). In immunofluorescence microscopy, intracellular fibronectin was seen diffusely perinuclearly whereas VIIIR:Ag was located both diffusely in the perinuclear cytoplasm and in distinct rod-shaped granules. These granules could, moreover, be visualized with fluorochrome-coupled Ricinus communis agglutinin I (RCA), which also stained the Golgi apparatus as a reticular juxtanuclear structure, and they were identified as Weibel-Palade bodies by immunoelectron microscopy. Puromycin treatment depleted intracellular fibronectin but did not affect the granular localization of VIIIR:Ag. A short exposure of the cells to monensin caused a juxtanuclear accumulation of fibronectin at the Golgi region whereas VIIIR:Ag only was seen in rounded cytoplasmic granules. A prolonged monensin treatment brought about a cytoplasmic accumulation of fibronectin-containing vesicles whereas VIIIR:Ag showed no accumulation and there was no codistribution between granules containing fibronectin or VIIIR:Ag. Type IV procollagen, on the other hand, was distinctly co-localized with fibronectin. In monensin-treated cells RCA mainly stained the VIIIR:Ag-containing vesicles whereas Concanavalin A (Con A) appeared to label the fibronectin-containing vesicles. Immunoelectron microscopy of these cells revealed VIIIR:Ag in some vacuolar structures and typical Weibel-Palade bodies could not be identified. Exposure of the cells to tunicamycin, on the other hand, caused a prominent cytoplasmic accumulation of VIIIR:Ag and, within 96 h, led to the disappearance of most of the VIIIR:Ag-positive granules but did not affect the intracellular distribution of fibronectin. These results, which show that metabolical inhibitors affect differently the intracellular compartmentalization of fibronectin and VIIIR:Ag, indicate, that the two glycoproteins have divergent intracellular pathways in cultured human endothelial cells.
D000941:Antigens / Q000032:analysis*; D001692:Biological Transport; D002451:Cell Compartmentation; D002478:Cells, Cultured; D004727:Endothelium / Q000378:metabolism / Q000648:ultrastructure; D005169:Factor VIII / Q000032:analysis / Q000276:immunology*; D005260:Female; D005353:Fibronectins / Q000378:metabolism*; D006056:Golgi Apparatus / Q000648:ultrastructure; D006801:Humans; D008856:Microscopy, Fluorescence; D008967:Molecular Biology; D011347:Procollagen / Q000378:metabolism; D014471:Umbilical Veins / Q000378:metabolism*; D014841:von Willebrand Factor
D000941:Antigens; D005353:Fibronectins; D011347:Procollagen; D014841:von Willebrand Factor; D005169:Factor VIII