Tissue factor apoprotein: intracellular transport and expression in shed membrane vesicles

We have studied the synthesis and subcellular distribution of the glycosylated membrane protein tissue factor (TF) in human blood monocytes and the inducible monocyte like cell line, HL-60. Following induction with endotoxin or the phorbol ester, TPA, tissue factor specific activity was measured in intact cells, sonicated cells, isolated plasma membranes and shed vesicles. We have shown that TF is transported over time from the cytoplasm to the plasma membrane and finally to shed membrane vesicles. Optimal transport of TF to the plasma membrane and shedding in membrane vesicles required glycosylation as judged by partial inhibition of this process by the tunicamycin homologues B2 and C2.