Feature article: Discovery of vascular Rho kinase (ROCK) inhibitory peptides

Rho-activated kinases (ROCKs) regulate many cellular functions such as proliferation, migration, and smooth muscle contractility, but they are also associated with pathogenesis of many human diseases such as heart failure and hypertension. We used phage display libraries to identify inhibitory polypeptides that bind to the ROCK1 catalytic domain, but do not compete with the ATP-binding pocket, by screening in the presence of high ATP concentrations (1 mM). Peptide7, a promising ROCK inhibitory peptide for both ROCK isoforms, measured at 1.45 ± 0.28 µM for ROCK1 (1–553) and 5.15 ± 1.15 µM for ROCK2. Peptide7 reduced cellular migration in wound healing assays. The binding epitope on ROCK1 was mapped to the flexible activation loop within the catalytic domain. Peptide alanine scanning mutants helped identify critical amino acids to generate optimized Peptide22. This compact ROCK inhibitor facilitated vascular relaxation, blocked neovascularization of endothelial cells, and inhibited MLC phosphatase phosphorylation. Our novel ROCK peptide inhibitors may provide potential treatment of hypertension and PAH progression.