Fig. 4. Functional involvement of the Rab27B–Slac2-c complex in amylase release from SLO-permeabilized parotid acinar cells. (A) Inhibition of amylase release by SHD, a specific Rab27 binding domain, in SLO-permeabilized parotid acinar cells. GST-SHD, but not GST alone, inhibited amylase release in a dose-dependent manner. (B) Inhibition of amylase release by ABD, an actin binding domain of Slac2-c, in SLO-permeabilized parotid acinar cells. GST-ABD, but not GST-ABD(RA) lacking actin binding capacity, inhibited amylase release in a dose-dependent manner. (C) Inhibition of amylase release by anti-Rab27B and anti-Slac2-c specific antibodies. Both anti-Rab27B and Slac2-c IgGs inhibited amylase release in a dose-dependent manner. By contrast, control IgG (up to 100 µg/ml) had no significant effect on amylase release. IPR-stimulated amylase release from SLO-permeabilized parotid acinar cells was measured as described in the Materials and Methods. The released amylase activity is expressed as a percentage of the IPR-stimulated release without rabbit IgG or GST fusion proteins. Bars indicate the mean±s.e.m. of 3-5 independent experiments, performed in triplicate. ^*P<0.01, Student's t-test.