Small-molecule inhibitors of protein function are powerful tools for biological analysis1 and can lead to the development of new drugs. However, a major bottleneck in generating useful small-molecule tools is target identification. Here we show that Caenorhabditis elegans can provide a platform for both the discovery of new bioactive compounds and target identification. We screened 14,100 small molecules for bioactivity in wild-type worms and identified 308 compounds that induce a variety of phenotypes. One compound that we named nemadipine-A induces marked defects in morphology and egg-laying. Nemadipine-A resembles a class of widely prescribed anti-hypertension drugs called the 1,4-dihydropyridines (DHPs) that antagonize the α1-subunit of L-type calcium channels2,3. Through a genetic suppressor screen, we identified egl-19 as the sole candidate target of nemadipine-A, a conclusion that is supported by several additional lines of evidence. egl-19 encodes the only L-type calcium channel α1-subunit in the C. elegans genome4,5. We show that nemadipine-A can also antagonize vertebrate L-type calcium channels, demonstrating that worms and vertebrates share the orthologous protein target. Conversely, FDA-approved DHPs fail to elicit robust phenotypes, making nemadipine-A a unique tool to screen for genetic interactions with this important class of drugs. Finally, we demonstrate the utility of nemadipine-A by using it to reveal redundancy among three calcium channels in the egg-laying circuit. Our study demonstrates that C. elegans enables rapid identification of new small-molecule tools and their targets.
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We thank J. Turnbull, S. Ito and H. Cheung for technical assistance, S. Dixon, C. Boone and B. Andrews for advice on the manuscript, and A. Spence for sharing equipment. We thank the C. elegans Genetic Center, which is funded by the NIH National Center for Research Resources, for sending us worm strains. E.F.S., P.M., S.R.C. and P.J.R. are Canadian Research Chairs in brain and behaviour, plant molecular biology, plant genomics, and molecular neurobiology, respectively. This work was supported by an NSERC Industrial Grant to P.M., a CIHR Grant to E.F.S., a CIHR CGS to A.W.C., and a Premier's Research Excellence Award and awards from the Canadian Foundation for Innovation and Ontario Innovation Trust to P.J.R. Author Contributions R.F. discovered that nemadipine-A induces the Vab phenotype, T.C.Y.K. and P.J.R. did the worm genetics and pharmacological analysis, P.M., R.F., A.B. and P.J.R. did the small-molecule screen, A.W.C. and E.F.S. did the electrophysiology, and S.R.C. did the HPLC analysis. N.R. provided technical assistance throughout. With critical input from S.R.C., P.J.R. led the project and wrote the paper.
This file contains Supplementary Methods, Supplementary Figure Legends and additional references.