Cyclic polyarginine peptides inhibit cellular convertase activity.

(a) CHO cells were incubated with each compound at 1 μM for 24 h at 37°C, and cell viability was monitored by incubation for 4 h with WST-1. (b) CHO-GRAPfurin cells, expressing secreted alkaline phosphatase tethered to Golgi membranes by a transmembrane domain interrupted by a furin cleavage site, was incubated with 1 μM of each cyclic peptide for 20–24 h at 37 °C. Secreted alkaline phosphatase activity was measured in the medium. Results represent the mean ± S.D., N = 3.