title: Off-target effects of the septin drug forchlorfenuron on nonplant eukaryotes.
abstract: The septins are a family of GTP-binding proteins that form cytoskeletal filaments. Septins are highly conserved and evolutionarily ancient but are absent from land plants. The synthetic plant cytokinin forchlorfenuron (FCF) was shown previously to inhibit budding yeast cell division and induce ectopic septin structures (M. Iwase, S. Okada, T. Oguchi, and A. Toh-e, Genes Genet. Syst. 79:199-206, 2004, http://dx.doi.org/10.1266/ggs.79.199). Subsequent studies in a wide range of eukaryotes have concluded that FCF exclusively inhibits septin function, yet the mechanism of FCF action in nonplant cells remains poorly understood. Here, we report that the cellular effects of FCF are far more complex than previously described. The reported growth arrest of budding yeast cells treated with 1 mM FCF partly reflects sensitization caused by a bud4 mutation present in the W303 strain background. In wild-type (BUD4(+)) budding yeast, growth was inhibited at FCF concentrations that had no detectable effect on septin structure or function. Moreover, FCF severely inhibited the proliferation of fission yeast cells, in which septin function is nonessential. FCF induced fragmentation of budding yeast mitochondrial reticula and the loss of mitochondrial membrane potential. Mitochondria also fragmented in cultured mammalian cells treated with concentrations of FCF that previously were assumed to target septins only. Finally, FCF potently inhibited ciliation and motility and induced mitochondrial disorganization in Tetrahymena thermophila without apparent alterations in septin structure. None of these effects was consistent with the inhibition of septin function. Our findings point to nonseptin targets as major concerns when using FCF.
authors.affiliation: Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA.
authors.forename: Lydia R
authors.initials: LR
authors.lastname: Heasley
authors.affiliation: Department of Biochemistry and Biophysics, University of California, San Francisco, California, USA.
authors.forename: Galo
authors.initials: G
authors.lastname: Garcia
authors.affiliation: Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA michael.mcmurray@ucdenver.edu.
authors.forename: Michael A
authors.initials: MA
authors.lastname: McMurray
mesh_terms: D018797:Cell Cycle Proteins / Q000235:genetics; D002460:Cell Line; D002465:Cell Movement / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D003599:Cytoskeleton / Q000187:drug effects; D004847:Epithelial Cells / Q000187:drug effects; D019204:GTP-Binding Proteins / Q000235:genetics; D006801:Humans; D025301:Hyphae / Q000254:growth & development; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects*; D008928:Mitochondria / Q000378:metabolism / Q000473:pathology; D010671:Phenylurea Compounds / Q000494:pharmacology*; D011725:Pyridines / Q000494:pharmacology*; D012441:Saccharomyces cerevisiae / Q000254:growth & development*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics; D012568:Schizosaccharomyces / Q000254:growth & development*; D058112:Septins / Q000037:antagonists & inhibitors*; D016808:Tetrahymena thermophila / Q000187:drug effects / Q000254:growth & development
chemical_list: C100763:BUD4 protein, S cerevisiae; D018797:Cell Cycle Proteins; D010671:Phenylurea Compounds; D011725:Pyridines; D029701:Saccharomyces cerevisiae Proteins; D019204:GTP-Binding Proteins; D058112:Septins; C116093:N-(2-chloro-4-pyridyl)-N'-phenylurea