Isoprenoids are an extensive group of natural products with diverse structures consisting of various numbers of five carbon isopentenyl pyrophosphate (IPP) units. The isoprenoid pathway has been studied in mammalian cells where the enzyme farnesyl pyrophosphate synthase (FPPS) plays a central role by producing FPP, an important precursor of sterols, dolichols, ubiquinones, and prenylated proteins. FPP, a 15 C isoprenoid unit could further form GGPP, a 15 C isoprenoid unit by the enzyme geranylgeranyl pyrophosphate synthase (GGPPS). FPPS forms FPP by the sequential condensation of dimethylallylpyrophosphate (DMAPP) with two molecules of isopentenylpyrophosphate (IPP). Little is known about the isoprenoid pathway in Toxoplasma gondii. Taking into account the central role of FPPS, its understanding will reveal important information on this pathway in T. gondii. In addition, our preliminary results indicate that this enzyme is a valid target for drugs since bisphosphonates, which are specific FPPS inhibitors, inhibited parasite growth in vitro and in vivo. The gene for the T. gondii farnesyl pyrophosphate synthase (TgFFPS) was cloned, sequenced and characterized. This gene was present as a single copy in the tachyzoite haploid genome, although by RT-PCR two transcripts were found and named TgFPPSI and TgFPPSII. Both isoforms of TgFPPS were heterologously expressed in the Bac-to-Bac expression systems and the corresponding protein(s) purified for their biochemical characterization. Only isoform II had enzymatic activity and, interestingly, this enzyme was capable of forming both products, farnesyl pyrophosphate and geranyl geranyl pyrophosphate. This unique characteristic was previously found only in enzymes of the Archaea. Another interesting finding was the mitochondrial localization of this enzyme, which agrees with the presence of a mitochondrial-targeting signal in the protein sequence. This is also a unique feature of this protein since other FPPS are normally found in the cytosol. It has been demonstrated that the FPPS is the target for bisphosphonates, FDA-approved pyrophosphate analogs currently used in the treatment of bone resorption disorders. These compounds inhibited the proliferation of T. gondii in vitro and in vivo. Our preliminary results show that there was a significant difference between the sensitivity of the TgFPPS enzyme to bisphosphonates when compared with the human counterpart. Our hypothesis is that the isoprenoid pathway constitutes a major novel target for the treatment of toxoplasmosis. To test this hypothesis, our specific aims are:(1) To further investigate the TgFPPS by site-directed mutagenesis to understand its bifunctionality, to perform structural studies to facilitate drug design, and to investigate the importance of TgFPPS products in the parasite biology; (2) To investigate the effect of pyrophosphate analogs in vitro against T. gondii, and perform structure-activity relationship studies to facilitate drug design. ? ? ?

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Exploratory/Developmental Grants (R21)
Project #
1R21AI068467-01A1
Application #
7120703
Study Section
AIDS-associated Opportunistic Infections and Cancer Study Section (AOIC)
Program Officer
Coyne, Philip Edward
Project Start
2006-03-01
Project End
2008-02-28
Budget Start
2006-03-01
Budget End
2007-02-28
Support Year
1
Fiscal Year
2006
Total Cost
$221,250
Indirect Cost
Name
University of Georgia
Department
Type
Organized Research Units
DUNS #
004315578
City
Athens
State
GA
Country
United States
Zip Code
30602
Cai, Guobin; Deng, Lisheng; Xue, Jian et al. (2013) Expression, characterization and inhibition of Toxoplasma gondii 1-deoxy-D-xylulose-5-phosphate reductoisomerase. Bioorg Med Chem Lett 23:2158-61
Recher, Marion; Barboza, Alejandro P; Li, Zhu-Hong et al. (2013) Design, synthesis and biological evaluation of sulfur-containing 1,1-bisphosphonic acids as antiparasitic agents. Eur J Med Chem 60:431-40
Li, Zhu-Hong; CintrĂ³n, Roxana; Koon, Noah A et al. (2012) The N-terminus and the chain-length determination domain play a role in the length of the isoprenoid product of the bifunctional Toxoplasma gondii farnesyl diphosphate synthase. Biochemistry 51:7533-40
Szajnman, Sergio H; Rosso, Valeria S; Malayil, Leena et al. (2012) 1-(Fluoroalkylidene)-1,1-bisphosphonic acids are potent and selective inhibitors of the enzymatic activity of Toxoplasma gondii farnesyl pyrophosphate synthase. Org Biomol Chem 10:1424-33
Rosso, Valeria S; Szajnman, Sergio H; Malayil, Leena et al. (2011) Synthesis and biological evaluation of new 2-alkylaminoethyl-1,1-bisphosphonic acids against Trypanosoma cruzi and Toxoplasma gondii targeting farnesyl diphosphate synthase. Bioorg Med Chem 19:2211-7
Nair, Sethu C; Brooks, Carrie F; Goodman, Christopher D et al. (2011) Apicoplast isoprenoid precursor synthesis and the molecular basis of fosmidomycin resistance in Toxoplasma gondii. J Exp Med 208:1547-59
Moreno, Silvia N J; Docampo, Roberto (2009) The role of acidocalcisomes in parasitic protists. J Eukaryot Microbiol 56:208-13
Szajnman, Sergio H; Garcia Linares, Guadalupe E; Li, Zhu-Hong et al. (2008) Synthesis and biological evaluation of 2-alkylaminoethyl-1,1-bisphosphonic acids against Trypanosoma cruzi and Toxoplasma gondii targeting farnesyl diphosphate synthase. Bioorg Med Chem 16:3283-90
Docampo, Roberto; Moreno, Silvia N J (2008) The acidocalcisome as a target for chemotherapeutic agents in protozoan parasites. Curr Pharm Des 14:882-8
Nagamune, Kisaburo; Moreno, Silvia N; Chini, Eduardo N et al. (2008) Calcium regulation and signaling in apicomplexan parasites. Subcell Biochem 47:70-81

Showing the most recent 10 out of 13 publications