title: Sterol 24-C-methyltransferase: an enzymatic target for the disruption of ergosterol biosynthesis and homeostasis in Cryptococcus neoformans.
abstract: Growth of Cryptococcus neoformans was inhibited by nine nitrogen and sulfur-containing sterols with a heteroatom positioned at C3, C7, C24, C25 or C32 in the lanostane frame. Analysis of the sterol composition of control and treated cells by GC-MS and (1)H NMR has proven that the C-methylation reaction catalyzed by the sterol 24-C-methyltransferase (24-SMT) is the crucial first step in a kinetically favored pathway that fails to include obtusifoliol or zymosterol as intermediates. Cultures fed [methyl-(2)H(3)]methionine led to two deuterium atoms into each of the newly biosynthesized sterols forming a route lanosterol, eburicol (24(28)-methylene-24,25-dihydrolanosterol), 32-noreburicol and ergost-7-enol to ergosterol. Examination of the substrate specificity of a soluble 24-SMT from C. neoformans showed lanosterol to be the optimal acceptor molecule. Incubation with the test compounds generated induced amounts of lanosterol, eburicol or 32-noreburicol concurrent with a decrease of ergosterol. Among them 24(R,S),25-epiminolanosterol (inhibitor of 24-SMT) showed the most potent in vitro antifungal activity comparable to those of itraconazole (inhibitor of the 14-demethylase). Taken together, these data indicate that treatment with substrate-based inhibitors of 24-SMT, a catalyst not found in humans, can disrupt ergosterol homeostasis involved with fungal growth and therefore these compounds can provide leads for rational drug design of opportunistic pathogens.
authors.affiliation: Department of Chemistry and Biochemistry, Texas Tech University, P.O. Box 1061, Lubbock, TX 79409-1061, USA. wdavid.nes@ttu.edu
authors.forename: W David
authors.initials: WD
authors.lastname: Nes
authors.forename: Wenxu
authors.initials: W
authors.lastname: Zhou
authors.forename: Kulothungan
authors.initials: K
authors.lastname: Ganapathy
authors.forename: JiaLin
authors.initials: J
authors.lastname: Liu
authors.forename: Rit
authors.initials: R
authors.lastname: Vatsyayan
authors.forename: Swetha
authors.initials: S
authors.lastname: Chamala
authors.forename: Keven
authors.initials: K
authors.lastname: Hernandez
authors.forename: Mayra
authors.initials: M
authors.lastname: Miranda
mesh_terms: D002784:Cholesterol / Q000378:metabolism; D002849:Chromatography, Gas; D002851:Chromatography, High Pressure Liquid; D003455:Cryptococcus neoformans / Q000201:enzymology*; D004875:Ergosterol / Q000096:biosynthesis* / Q000494:pharmacology*; D005656:Fungal Proteins / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism*; D006706:Homeostasis; D007700:Kinetics; D007810:Lanosterol / Q000031:analogs & derivatives* / Q000494:pharmacology; D008715:Methionine / Q000494:pharmacology*; D008780:Methyltransferases / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism*; D008861:Microsomes / Q000201:enzymology; D013261:Sterols / Q000378:metabolism*
chemical_list: D005656:Fungal Proteins; D013261:Sterols; D007810:Lanosterol; C014520:ebericol; D002784:Cholesterol; D008715:Methionine; D008780:Methyltransferases; C022670:delta 24-sterol methyltransferase; D004875:Ergosterol