Fig. 6.

Matriptase activation is quickly followed by secretion. A: activation and HAI-1-mediated inhibition induced by exposure to a mildly acidic milieu. 184 A1N4 mammary epithelial cells were exposed to basal media or phosphate buffer, pH 6.0, for 20 min. Lysates from both treatments (lanes 1 for nonactivation control; lanes 2 for activation) were subjected to immunoblot analyses for total matriptase using the mAb M32 (left), activated matriptase using the mAb M69 (middle), or HAI-1 using the mAb M19 (right). B: kinetics of matriptase-HAI-1 complex shedding. Matriptase activation was induced by acid exposure, and the cells returned to the basal media for the indicated times. Cell lysates and conditioned media were harvested and analyzed by immunoblotting using the matriptase mAb M32, the activated matriptase mAb M69 (data not shown), and the HAI-1 mAb M19 (data not shown). Control cultures, not exposed to acid, were also examined with the same time course.