Separation of induction and expression of tight junction formation mediated by proteinases

The formation of tight junctions can be induced in the human adenocarcinoma cell line HT 29 by treatment with trypsin at 37 degrees C. In contrast, after treatment of the cells with trypsin at low temperature (3 degrees C), no tight junctions were observed. However, abundant formation of tight junctions occurred when cells were treated with trypsin at 3 degrees C, washed with soybean trypsin inhibitor, and subsequently incubated at 37 degrees C. Thus, this protocol allows for the first time the temporal separation of the induction and assembly of tight junctions.