HUVECs or CHO-tie cells were treated with 10 ng/mL TNFα or PMA for 1 hour before preparation of cell lysates containing the cell-associated C-terminal tie-1 fragment. The C-terminal fragment was isolated by antibody affinity chromatography and subjected to N-terminal microsequencing analysis as described in Materials and Methods The cleavage point between amino acids E⁷⁴⁹ and S⁷⁵⁰ is indicated by a backslash.