Rational Design of Calpain Inhibitors Based on Calpastatin Peptidomimetics

摘要

Our previously reported structures of calpain bound to its endogenous inhibitor calpastatin have motivated the use of aziridine aldehyde-mediated peptide macrocyclization toward the design of cyclic peptides and peptidomimetics as calpain inhibitors. Inspired by nature's hint that a beta-turn loop within calpastatin forms abroad interaction around calpain's active site cysteine, we have constructed and tested a library of 45 peptidic compounds based on this loop sequence: Four molecules have shown reproducibly low micromolar inhibition of calpain-2. Further systematic sequence changes led to the development of probes that displayed increased potency and specificity of inhibition against calpain over other cysteine proteases. Calculated K-i values were in the low micromolar range, rivaling other peptidomimetic calpain inhibitors and presenting an improved selectivity profile against other therapeutically relevant proteases. Competitive and Mixed inhibition against calpain-2 was observed, and an allosteric inhibition site on the enzyme was identified for a noncompetitive inhibitor.