title: Inhibition of calpain in intact platelets by the thiol protease inhibitor E-64d.
abstract: E-64d, a membrane permeant derivative of E-64c, a thiol protease inhibitor (Tamai et al. (1986) J. Pharmacobio-Dyn. 9, 672-677), was tested for ability to inhibit calpain activity in intact platelets. Calpain activity was measured by proteolysis of actin-binding protein and talin, two known substrates of calpain. Incubation of platelets with E-64c (not permeant) or E-64d before lysis prevented proteolysis after lysis. When the platelets were incubated with E-64c or E-64d and then washed to remove the drugs before lysis, only E-64d inhibited proteolysis. When platelets were incubated with E-64c or E-64d and then activated with A23187 plus calcium, a treatment that activates intraplatelet calpain, only E-64d inhibited proteolysis. These results indicate that E-64d can enter the intact cell and inhibit calpain.
authors.affiliation: Department of Biochemistry, SUNY Health Science Center, Brooklyn 11203.
authors.forename: E B
authors.initials: EB
authors.lastname: McGowan
authors.forename: E
authors.initials: E
authors.lastname: Becker
authors.forename: T C
authors.initials: TC
authors.lastname: Detwiler
mesh_terms: D001792:Blood Platelets / Q000201:enzymology*; D000001:Calcimycin / Q000494:pharmacology; D002154:Calpain / Q000037:antagonists & inhibitors*; D002463:Cell Membrane Permeability; D003598:Cytoskeletal Proteins / Q000378:metabolism; D007930:Leucine / Q000031:analogs & derivatives* / Q000494:pharmacology; D008840:Microfilament Proteins / Q000378:metabolism; D011480:Protease Inhibitors / Q000494:pharmacology*; D016608:Talin
chemical_list: D003598:Cytoskeletal Proteins; D008840:Microfilament Proteins; D011480:Protease Inhibitors; D016608:Talin; D000001:Calcimycin; D002154:Calpain; D007930:Leucine; C108192:aloxistatin