Hedgehog antagonist cyclopamine isomerizes to less potent forms when acidified |
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Authors: | Steven Ray Wilson Martin Frank Strand Andreas Krapp Frode Rise Dirk Petersen Stefan Krauss |
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Affiliation: | 1. Department of Chemistry, University of Oslo, P.O. Box 1033, Blindern, NO-0315, Oslo, Norway;2. Section for Cellular and Genetic Therapy, Institute for Microbiology, University Hospital Oslo, NO-0027, Oslo, Norway;3. The Centre for Theoretical and Computational Chemistry (CTCC), P.O. Box 1033, Blindern, NO-0315, Oslo, Norway |
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Abstract: | The effect of acid treatment of cyclopamine, a natural antagonist of the hedgehog (Hh) signaling pathway and a potential anti-cancer drug, has been studied. Previous reports have shown that under acidic conditions, as in the stomach, cyclopamine is less effective. Also, it has been stated that cyclopamine converts to veratramine, which has side effects such as hemolysis. In this study, we examined in detail the influence of acidification on structure and activity of cyclopamine. We found that of acidified cyclopamine converts to two previously unreported isomers, which we have called cyclopamine (S) and cyclopamine (X). These have likely gone undetected because cyclopamine is often analyzed with fast and hence lower resolving chromatographic methods. Compared to natural cyclopamine, these cyclopamine isomers have a significantly reduced effect on the ciliary transport of the Hh receptor smoothened, and reduced inhibition on the Hedgehog signaling pathway. The side effects of these isomers are unknown. Our findings can partly explain a reduced efficiency of cyclopamine in a gastric environment, and may help with the rational design of more pH independent cyclopamine analogues. |
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Keywords: | Cyclopamine Hedgehog Isomerization NMR LC&ndash MS |
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