Intracellular distribution of chimeric vWF species.

AtT-20 cells were transiently transfected with chimeric vWF constructs, immunostained, and examined by confocal laser scanning microscopy for intracellular distribution of vW AgII and vWF. (A-C) Cells stained for vW AgII. (D-F) vWF staining. The human propeptide expressed intrans with canine mature vWF resulted in granular storage of both human vW AgII and canine vWF (A and D). In contrast, expression of canine propeptide in trans with human mature vWF resulted in granular storage of only canine vW AgII (B). Canine vW AgII did not traffick human mature vWF to granular storage; only a cytoplasmic staining pattern was observed (E). This indicates that canine vW AgII does not have the necessary signal or conformation required for interaction with human mature vWF to sort it to storage. Similar results were obtained when canine vW AgII was expressed incis with human mature vWF, K9/Hu-vWF, as seen in C and F. The canine vW AgII was sorted to granular storage, whereas the human vWF displayed only a cytoplasmic staining pattern. This indicates that propeptide cleavage occurs before the formation of storage granules. Total magnification, 1410×.