FIGURE 1.

Cell-free versus intact cell matriptase activation. The insoluble fractions of cell homogenates (Cell-free, lanes 2) or intact cells (Intact cell, lanes 4) were exposed to pH 6.0 citric acid-phosphate buffer at room temperature for 20 min to induce matriptase activation. The non-activation control for the cell-free system was incubated at 4 °C (lanes 1) and the intact cell system was incubated in basal media (lanes 3). Lysates prepared from these samples were analyzed by immunoblotting for total matriptase using mAb M32, for activated matriptase using mAb M69, and for HAI-1 using mAb M19, as indicated.