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The Intracellular Target for the Antiresorptive Aminobisphosphonate Drugs in Dictyostelium discoideum Is the Enzyme Farnesyl Diphosphate Synthase
Author(s) -
Grove Joanna E.,
Brown Richard J.,
Watts Donald J.
Publication year - 2000
Publication title -
journal of bone and mineral research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.882
H-Index - 241
eISSN - 1523-4681
pISSN - 0884-0431
DOI - 10.1359/jbmr.2000.15.5.971
Subject(s) - dictyostelium discoideum , atp synthase , squalene , farnesyl diphosphate synthase , enzyme , cyclase , intracellular , biochemistry , farnesyl diphosphate farnesyltransferase , isomerase , chemistry , mutant , dictyostelium , adenylate kinase , ic50 , biology , prenylation , in vitro , gene , farnesyltransferase
Aminobisphosphonate (aBP) drugs inhibit osteoclast‐mediated bone resorption and also growth of amoebas of Dictyostelium discoideum apparently by interaction with the same intracellular target. Identification of the target in Dictyostelium therefore could also identify the target in osteoclasts. The aBPs (100 μM alendronate and 30 μM YM‐175) inhibited conversion of [ 14 C]mevalonate into sterols by cultures of Dictyostelium amoebas. One of three enzymes (isopentenyl diphosphate [IDP] isomerase, farnesyl diphosphate [FDP] synthase, and squalene synthase) appeared to be the target for this inhibition because conversion of [ 14 C]IDP into squalene, the immediate precursor for sterol biosynthesis, was inhibited in extracts of wild‐type amoebas by alendronate (IC 50 = 75 nM) or risedronate (IC 50 = 30 nM) whereas, when the extract had been prepared from amoebas of strains selected for having partial resistance to the growth‐inhibitory effects of alendronate (strain MR102) or risedronate (strain RB101), the values of IC 50 were increased to 700 nM for alendronate (MR102 extract) or 130 nM for risedronate (RB101 extract). Neither IDP isomerase nor squalene synthase was inhibited significantly by alendronate or risedronate but both of these aBP drugs, and all others tested, inhibited FDP synthase. Determination of the nucleotide sequences of complementary DNAs (cDNAs) encoding FDP synthase in the wild‐type and aBP‐resistant strains of Dictyostelium indicated that there had been no changes in the amino acid sequence of the enzyme in the mutant strains. However, both mutant strains overproduce FDP synthase. It is concluded that FDP synthase is the intracellular target for the aBP drugs. (J Bone Miner Res 2000;15:971–981)