title: Identification and validation of cryptochrome inhibitors that modulate the molecular circadian clock.
abstract: Circadian rhythms, biological oscillations with a period of about 24 h, are maintained by a genetically determined innate time-keeping system called the molecular circadian clockwork. Despite the physiological and clinical importance of the circadian clock, the development of small molecule modulators that directly target the core clock machinery has only been recently initiated. In the present study, we aimed to identify novel small molecule modulators influencing the molecular feedback loop of the circadian clock by applying our two-step cell-based screening strategy based on E-box-mediated transcriptional activity to test more than 1000 drug-like compounds. A derivative of 2-ethoxypropanoic acid designated as compound 15 was selected as the most promising candidate in terms of both efficacy and potency. We then performed pull-down assays with the biotinylated compound and find out that both cryptochrome (CRY)1 and 2 (CRY1/2), key negative components of the mammalian circadian clock, as molecular targets of compound 15. In accordance with the binding property, compound 15 enhanced E-box-mediated transcription in a CRY1/2-dependent manner, and more importantly, it attenuated the circadian oscillation of Per2-Luc and Bmal1-dLuc activities in cultured fibroblasts, indicating that compound 15 can functionally inhibit the effects of CRY1/2 in the molecular circadian clockwork. In conclusion, the present study describes the first novel chemical inhibitor of CRY1/2 that inhibits the repressive function of CRY1/2, thereby activating CLOCK-BMAL1-evoked E-box-mediated transcription. Further optimizations and subsequent functional studies of this compound may lead to development of efficient therapeutic strategies for a variety of physiological and metabolic disorders with circadian natures.
authors.affiliation: Department of Biological Sciences, Seoul National University , 1 Gwanak-ro, Gwanak-gu, Seoul 151-742, Korea.
authors.forename: Sung Kook
authors.initials: SK
authors.lastname: Chun
authors.forename: Jaebong
authors.initials: J
authors.lastname: Jang
authors.forename: Sooyoung
authors.initials: S
authors.lastname: Chung
authors.forename: Hwayoung
authors.initials: H
authors.lastname: Yun
authors.forename: Nam-Jung
authors.initials: NJ
authors.lastname: Kim
authors.forename: Jong-Wha
authors.initials: JW
authors.lastname: Jung
authors.forename: Gi Hoon
authors.initials: GH
authors.lastname: Son
authors.forename: Young-Ger
authors.initials: YG
authors.lastname: Suh
authors.forename: Kyungjin
authors.initials: K
authors.lastname: Kim
mesh_terms: D000818:Animals; D057906:Circadian Clocks / Q000187:drug effects*; D056931:Cryptochromes / Q000037:antagonists & inhibitors* / Q000235:genetics; D004305:Dose-Response Relationship, Drug; D024721:E-Box Elements / Q000235:genetics; D025461:Feedback, Physiological / Q000187:drug effects; D005347:Fibroblasts / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D008156:Luciferases / Q000235:genetics; D008163:Luminescent Measurements; D051379:Mice; D015394:Molecular Structure; D041681:NIH 3T3 Cells; D011485:Protein Binding; D054852:Small Molecule Libraries / Q000737:chemistry / Q000494:pharmacology*; D014162:Transfection
chemical_list: D056931:Cryptochromes; D054852:Small Molecule Libraries; D008156:Luciferases