title: Fluoxetine-resistance genes in Caenorhabditis elegans function in the intestine and may act in drug transport.
abstract: Fluoxetine (Prozac) is one of the most widely prescribed pharmaceuticals, yet important aspects of its mechanism of action remain unknown. We previously reported that fluoxetine and related antidepressants induce nose muscle contraction of C. elegans. We also reported the identification and initial characterization of mutations in seven C. elegans genes that cause defects in this response (Nrf, nose resistant to fluoxetine). Here we present genetic evidence that the known nrf genes can be divided into two subgroups that confer sensitivity to fluoxetine-induced nose contraction by distinct pathways. Using both tissue-specific promoters and genetic mosaic analysis, we show that a gene from one of these classes, nrf-6, functions in the intestine to confer fluoxetine sensitivity. Finally, we molecularly identify nrf-5, another gene in the same class. The NRF-5 protein is homologous to a family of secreted lipid-binding proteins with broad ligand specificity. NRF-5 is expressed in the intestine and is likely secreted into the pseudocoelomic fluid, where it could function to transport fluoxetine. One model that explains these findings is that NRF-5 binds fluoxetine and influences its presentation or availability to in vivo targets.
authors.affiliation: Department of Genome Sciences, University of Washington, Seattle, Washington 98195, USA.
authors.forename: Robert K M
authors.initials: RK
authors.lastname: Choy
authors.forename: John M
authors.initials: JM
authors.lastname: Kemner
authors.forename: James H
authors.initials: JH
authors.lastname: Thomas
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001693:Biological Transport, Active / Q000235:genetics; D017173:Caenorhabditis elegans / Q000235:genetics* / Q000378:metabolism; D029742:Caenorhabditis elegans Proteins / Q000235:genetics* / Q000502:physiology; D002352:Carrier Proteins / Q000235:genetics* / Q000502:physiology; D004351:Drug Resistance / Q000235:genetics*; D005473:Fluoxetine / Q000493:pharmacokinetics*; D017238:Genes, Helminth; D007413:Intestinal Mucosa / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics* / Q000502:physiology; D008969:Molecular Sequence Data; D009030:Mosaicism; D009119:Muscle Contraction / Q000235:genetics; D009297:Nasal Mucosa / Q000378:metabolism; D009666:Nose / Q000502:physiology
chemical_list: D029742:Caenorhabditis elegans Proteins; D002352:Carrier Proteins; D008565:Membrane Proteins; C576460:NRF-5 protein, C elegans; C499577:ndg-4 protein, C elegans; C121507:nrf-6 protein, C elegans; D005473:Fluoxetine