Direct targeting of rab-GTPase-effector interactions

Small GTPases are molecular switches using GDP/GTP alternation to control numerous vital cellular processes. Although aberrant function and regulation of GTPases are implicated in various human diseases, direct targeting of this class of proteins has proven difficult, as GTPase signaling and regulation is mediated by extensive and shallow protein interfaces. Here we report the development of inhibitors of protein-protein interactions involving Rab proteins, a subfamily of GTPases, which are key regulators of vesicular transport. Hydrocarbon-stapled peptides were designed based on crystal structures of Rab proteins bound to their interaction partners. These modified peptides exhibit significantly increased affinities and include a stapled peptide (StRIP3) that selectively binds to activated Rab8a and inhibits a Rab8a-effector interaction in vitro. Targeting small GTPases: A library of hydrocarbon-stapled peptides was designed to target Rab GTPases and yielded peptides with significantly increased target affinity. One peptide demonstrates selective binding of activated Rab8a and inhibition of a Rab8a-effector interaction. This work suggests that peptide stapling may enable the development of inhibitors for other small GTPases.