title: Inhibition of cathepsin activity in a cell-based assay by a light-activated ruthenium compound.
abstract: Light-activated inhibition of cathepsin activity was demonstrated in a cell-based assay. Inhibitors of cathepsin K, Cbz-Leu-NHCH2 CN (2) and Cbz-Leu-Ser(OBn)-CN (3), were caged within the complexes cis-[Ru(bpy)2 (2)2 ]Cl2 (4) and cis-[Ru(bpy)2 (3)2 ](BF4 )2 (5) (bpy=2,2'-bipyridine) as 1:1 mixtures of Δ and Λ stereoisomers. Complexes 4 and 5 were characterized by (1) H NMR, IR, and UV/Vis spectroscopies and electrospray mass spectrometry. Photochemical experiments confirm that 4 releases two molecules of 2 upon exposure to visible light for 15 min, whereas release of 3 by 5 requires longer irradiation times. IC50 determinations against purified cathepsin K under light and dark conditions with 4 and 5 confirm that inhibition is enhanced from 35- to 88-fold, respectively, upon irradiation with visible light. No apparent toxicity was observed for 4 in the absence or presence of irradiation in bone marrow macrophage (BMM) or PC3 cells, as determined by MTT assays, at concentrations up to 10 μM. Compound 5 is well tolerated at lower concentrations (<1 μM), but does show growth-inhibitory effects at higher concentrations. Confocal microscopy experiments show that 4 decreases intracellular cathepsin activity in osteoclasts with light activation. These results support the further development of caged nitrile-based inhibitors as chemical tools for investigating spatial aspects of proteolysis within living systems.
authors.affiliation: Department of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit, MI 48202 (USA).
authors.forename: Tomasz
authors.initials: T
authors.lastname: Respondek
authors.forename: Rajgopal
authors.initials: R
authors.lastname: Sharma
authors.forename: Mackenzie K
authors.initials: MK
authors.lastname: Herroon
authors.forename: Robert N
authors.initials: RN
authors.lastname: Garner
authors.forename: Jessica D
authors.initials: JD
authors.lastname: Knoll
authors.forename: Eric
authors.initials: E
authors.lastname: Cueny
authors.forename: Claudia
authors.initials: C
authors.lastname: Turro
authors.forename: Izabela
authors.initials: I
authors.lastname: Podgorski
authors.forename: Jeremy J
authors.initials: JJ
authors.lastname: Kodanko
mesh_terms: D015082:2,2'-Dipyridyl / Q000737:chemistry; D000818:Animals; D002401:Cathepsin B / Q000037:antagonists & inhibitors / Q000378:metabolism; D056657:Cathepsin K / Q000037:antagonists & inhibitors* / Q000378:metabolism; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D056831:Coordination Complexes / Q000138:chemical synthesis / Q000737:chemistry* / Q000633:toxicity; D004791:Enzyme Inhibitors / Q000138:chemical synthesis / Q000737:chemistry* / Q000633:toxicity; D008027:Light; D051379:Mice; D018613:Microscopy, Confocal; D012428:Ruthenium / Q000737:chemistry*
chemical_list: D056831:Coordination Complexes; D004791:Enzyme Inhibitors; D015082:2,2'-Dipyridyl; D012428:Ruthenium; D002401:Cathepsin B; D056657:Cathepsin K
keywords: cathepsins; enzymes; inhibitors; photochemistry; ruthenium
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