OPPOSITE SORTING OF TISSUE FACTOR IN HUMAN UMBILICAL VEIN ENDOTHELIAL-CELLS AND MADIN-DARBY CANINE KIDNEY EPITHELIAL-CELLS

Tissue factor (TF) is a 48-kD transmembrane glycoprotein that triggers the extrinsic pathway of blood coagulation by interacting with the pl asma coagulation factor VII (FVII). TF is also a true receptor in that a cellular signal is generated when activated FVII (FVIIa) binds to T F. For both of these functions, the cellular surface distribution of T F is important, since FVII is primarily available on the apical side o f vascular endothelial cells and on the basolateral side of epithelial cells lining the internal and external surfaces. We show that in endo thelial cells, TF (both antigen and procoagulant activity) is sorted t o the apical surface, whereas in wild-type and stably transfected Madi n-Darby canine kidney epithelial cells (MDCK), which form tight juncti ons and express if constitutively, TF antigen is on the basolateral su rface. No significant clotting activity is detectable on this surface. Truncated TF (cytoplasmic tail residues 246 to 263 deleted) is sorted as wild-type in MDCK cells. (C) 1996 by The American Society of Hemat ology.