title: Rational Design of Calpain Inhibitors Based on Calpastatin Peptidomimetics.
abstract: 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 β-turn loop within calpastatin forms a broad 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 Ki 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.
authors.affiliation: Department of Biomedical and Molecular Sciences, Queen's University , Kingston, Ontario K7L 3N6, Canada.
authors.forename: Kristin E
authors.initials: KE
authors.lastname: Low
authors.affiliation: Department of Chemistry, University of Toronto , Toronto, Ontario M5S 3H6, Canada.
authors.forename: Spencer
authors.initials: S
authors.lastname: Ler
authors.affiliation: Department of Biomedical and Molecular Sciences, Queen's University , Kingston, Ontario K7L 3N6, Canada.
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Chen
authors.affiliation: Department of Biomedical and Molecular Sciences, Queen's University , Kingston, Ontario K7L 3N6, Canada.
authors.forename: Robert L
authors.initials: RL
authors.lastname: Campbell
authors.affiliation: Encycle Therapeutics Inc. , 101 College Street, Suite 314, Toronto, Ontario M5G 1L7, Canada.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Hickey
authors.affiliation: Department of Chemistry, University of Toronto , Toronto, Ontario M5S 3H6, Canada.
authors.forename: Joanne
authors.initials: J
authors.lastname: Tan
authors.affiliation: Department of Chemistry, University of Toronto , Toronto, Ontario M5S 3H6, Canada.
authors.forename: Conor C G
authors.initials: CC
authors.lastname: Scully
authors.affiliation: Department of Biomedical and Molecular Sciences, Queen's University , Kingston, Ontario K7L 3N6, Canada.
authors.forename: Peter L
authors.initials: PL
authors.lastname: Davies
authors.affiliation: Department of Chemistry, University of Toronto , Toronto, Ontario M5S 3H6, Canada.
authors.forename: Andrei K
authors.initials: AK
authors.lastname: Yudin
authors.affiliation: Department of Chemistry, University of Toronto , Toronto, Ontario M5S 3H6, Canada.
authors.forename: Serge
authors.initials: S
authors.lastname: Zaretsky
mesh_terms: D000818:Animals; D002154:Calpain / Q000037:antagonists & inhibitors*; D004305:Dose-Response Relationship, Drug; D015195:Drug Design; D006023:Glycoproteins / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D006801:Humans; D008958:Models, Molecular; D008968:Molecular Conformation; D010456:Peptides, Cyclic / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D057786:Peptidomimetics / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D051381:Rats; D013329:Structure-Activity Relationship
chemical_list: D006023:Glycoproteins; D010456:Peptides, Cyclic; D057786:Peptidomimetics; C039304:calpain inhibitors; D002154:Calpain; C569870:CAPN2 protein, human