Metabolism
The Conserved Rieske Oxygenase DAF-36/Neverland Is a Novel Cholesterol-metabolizing Enzyme*

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Steroid hormones play essential roles in a wide variety of biological processes in multicellular organisms. The principal steroid hormones in nematodes and arthropods are dafachronic acids and ecdysteroids, respectively, both of which are synthesized from cholesterol as an indispensable precursor. The first critical catalytic step in the biosynthesis of these ecdysozoan steroids is the conversion of cholesterol to 7-dehydrocholesterol. However, the enzymes responsible for cholesterol 7,8-dehydrogenation remain unclear at the molecular level. Here we report that the Rieske oxygenase DAF-36/Neverland (Nvd) is a cholesterol 7,8-dehydrogenase. The daf-36/nvd genes are evolutionarily conserved, not only in nematodes and insects but also in deuterostome species that do not produce dafachronic acids or ecdysteroids, including the sea urchin Hemicentrotus pulcherrimus, the sea squirt Ciona intestinalis, the fish Danio rerio, and the frog Xenopus laevis. An in vitro enzymatic assay system reveals that all DAF-36/Nvd proteins cloned so far have the ability to convert cholesterol to 7-dehydrocholesterol. Moreover, the lethality of loss of nvd function in the fruit fly Drosophila melanogaster is rescued by the expression of daf-36/nvd genes from the nematode Caenorhabditis elegans, the insect Bombyx mori, or the vertebrates D. rerio and X. laevis. These data suggest that daf-36/nvd genes are functionally orthologous across the bilaterian phylogeny. We propose that the daf-36/nvd family of proteins is a novel conserved player in cholesterol metabolism across the animal phyla.

Cholesterol Metabolism
Development
Drosophila Genetics
Enzymes
Evolution
Steroid Hormone
DAF-36/Neverland
Rieske

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The nucleotide sequence(s) reported in this paper has been submitted to the GenBankTM/EBI Data Bank with accession number(s) AB607950AB607954.

*

This work was supported in part by the Special Coordination Funds for Promoting Science and Technology of the Ministry of Education, Culture, Sports, Science, and Technology of the Japanese Government; by grants from the Agricultural Chemical Research Foundation and the Japan Association for Marine Biology (to R. N.); and by Grant-in-Aid for Scientific Research 19380034 from the Japan Society for the Promotion of Science (JSPS) and a grant from the Program for Promotion of Basic Research Activities for Innovative Biosciences (to H. K.).

The on-line version of this article (available at http://www.jbc.org) contains supplemental Experimental Procedures, Tables S1 and S2, and Figs. S1–S4.

1

Both authors contributed equally to this work.

2

Recipient of a fellowship from JSPS.