Figure 1.

E peptide inhibits stimulated release of ³⁵S-labeled secretogranin from permeabilized PC12 cells. Cells in 24-well plates were labeled overnight with [³⁵S]sulfate, chased, and permeabilized with SLO. They were then equilibrated 30 min on ice with or without (control) EGTA-buffered Ca²⁺ (10 μM) and with or without E peptide. Secretion of ³⁵S-labeled SG was evaluated as in MATERIALS AND METHODS. (A) E peptides from normal SCAMP2, normal SCAMP1, and structural variants of SCAMP2 in which residues 1, and 2 and 3 together, were changed from C to A and WY to AA, respectively, were compared at a concentration of 100 μM. Stimulated secretion of ³⁵S-labeled secretogranin ranged from 35 to 45% of total above an unstimulated secretion of 1–2% of total. The inset presents a sample autoradiograph that demonstrates clearly the effects of the peptide on secretion. (B) Dose-response curve for inhibition of secretion by E peptide of SCAMP2. The results shown are normalized to stimulated secretion from peptide-free samples from three independent experiments and are plotted as mean ± SEM.