Investigation on Cellular Uptake and Pharmacodynamics of Dock2-Inhibitory Peptides Conjugated with Cell-Penetrating Peptides

Protein–protein interaction between dedicator of cytokinesis 2 (DOCK2) and Ras-related C3 botulinum toxin substrate 1 (Rac1) is an attractive intracellular target for transplant rejection and inflammatory diseases. Recently, DOCK2-selective inhibitory peptides have been discovered, and conjugation with oligoarginine cell-penetrating peptide (CPP) improved inhibitory activity in a cell migration assay. Although a number of CPPs have been reported, oligoarginine was only one example introduced to the inhibitory peptides. In this study, we aimed to confirm the feasibility of CPP-conjugation approach for DOCK2-inhibitory peptides, and select preferable sequences as CPP moiety. First, we evaluated cell permeability of thirteen known CPPs and partial sequences of influenza A viral protein PB1-F2 using an internalization assay system based on luciferin–luciferase reaction, and then selected four CPPs with efficient cellular uptake. Among four conjugates of these CPPs and a DOCK2-inhibitory peptide, the inhibitory activity of a novel CPP, PB1-F2 fragment 5 (PF5), conjugate was comparable to oligoarginine conjugate and higher than that of the non-conjugated peptide. Finally, internalization assay revealed that oligoarginine and PF5 increased the cellular uptake of inhibitory peptides to the same extent. Hence, we demonstrated that CPP-conjugation approach is applicable to the development of novel anti-inflammatory drugs based on DOCK2 inhibition by investigating both cellular uptake and bioactivity.