Morbidity and mortality due to infections with Toxoplasma gondii is an increasing problem in the HIV infected population. Management of toxoplasmosis in these patients is complicated by a high incidence of side effects with the most commonly used compounds and the inactivity of these compounds against the latent stage of the parasite. Hence, there is a continuing need to define novel therapeutic targets and develop new therapeutic agents for this pathogen. One feature of the basic metabolism of these organisms which has not been fully exploited for chemotherapy is the characteristics of their adenosine kinase and its unique specificity in the activation of """"""""subversive"""""""" substrates"""""""". Results from our laboratory indicate that the parasite, but not the host, adenosine kinase can uniquely phosphorylate certain 6-substituted purine nucleosides as """"""""subversive"""""""" substrates and thereby selectively kill T. gondii in vitro and extend the life span of infected mice. Therefore, T. gondii adenosine kinase was cloned, overexpressed and purified. Structure activity relationships as well as comparative metabolic and molecular studies indicate that T. gondii adenosine kinase is indeed substantially different from that of the host in substrate specificity, structure and other characteristics. The purpose of this application is to extend our studies to further characterize the T. gondii adenosine kinase and to use the information gained to develop potent and selective subversive substrates as potential anti-toxoplasmic agents. This approach may well apply to other opportunistic infections which share with toxoplasma this unique feature of purine analogue metabolism.
The Specific Aims are:
Aim 1 : Detailed studies of the cloned T. gondii adenosine kinase.
Aim 2 : Crystallization and resolution of the three dimensional structures of the enzyme with bound 6-substituted subversive substrates.
Aim 3. Molecular modeling studies for the rational design of 6-substituted subversive substrates.
Aim 4 : Chemical synthesis and enzymatic evaluation of rationally designed 6-substituted subversive substrates.
Aim 5 : Evaluate promising rationally designed 6-substituted subversive substrates as potential anti-toxoplasmosis agents in vitro and in vivo.
Aim : 6. Determine the mechanism of selective toxicity of active compounds. These studies will utilize the complementary strengths of the investigators in a collaborative, integrated effort to achieve these goals. ? ?

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI052838-04
Application #
7257861
Study Section
Special Emphasis Panel (ZRG1-AARR-E (04))
Program Officer
Rogers, Martin J
Project Start
2004-07-01
Project End
2009-06-30
Budget Start
2007-07-01
Budget End
2009-06-30
Support Year
4
Fiscal Year
2007
Total Cost
$498,669
Indirect Cost
Name
University of Alabama Birmingham
Department
Pharmacology
Type
Schools of Medicine
DUNS #
063690705
City
Birmingham
State
AL
Country
United States
Zip Code
35294
El Kouni, Mahmoud H (2017) Pyrimidine metabolism in schistosomes: A comparison with other parasites and the search for potential chemotherapeutic targets. Comp Biochem Physiol B Biochem Mol Biol 213:55-80
Naguib, Fardos N M; Rais, Reem H; Al Safarjalani, Omar N et al. (2015) Kinetic mechanism of Toxoplasma gondii adenosine kinase and the highly efficient utilization of adenosine. Comp Biochem Physiol B Biochem Mol Biol 188:63-9
Kim, Young Ah; Rawal, Ravindra K; Yoo, Jakyung et al. (2010) Structure-activity relationships of carbocyclic 6-benzylthioinosine analogues as subversive substrates of Toxoplasma gondii adenosine kinase. Bioorg Med Chem 18:3403-12
Al Safarjalani, Omar N; Rais, Reem H; Kim, Young Ah et al. (2010) Carbocyclic 6-benzylthioinosine analogues as subversive substrates of Toxoplasma gondii adenosine kinase: biological activities and selective toxicities. Biochem Pharmacol 80:955-63
Al Safarjalani, Omar N; Rais, Reem H; Kim, Young Ah et al. (2008) 7-Deaza-6-benzylthioinosine analogues as subversive substrate of Toxoplasma gondii adenosine kinase: activities and selective toxicities. Biochem Pharmacol 76:958-66
Kim, Young Ah; Sharon, Ashoke; Chu, Chung K et al. (2008) Structure-activity relationships of 7-deaza-6-benzylthioinosine analogues as ligands of Toxoplasma gondii adenosine kinase. J Med Chem 51:3934-45
Kim, Young Ah; Sharon, Ashoke; Chu, Chung K et al. (2007) Synthesis, biological evaluation and molecular modeling studies of N6-benzyladenosine analogues as potential anti-toxoplasma agents. Biochem Pharmacol 73:1558-72
Zhang, Yan; El Kouni, Mahmoud H; Ealick, Steven E (2007) Substrate analogs induce an intermediate conformational change in Toxoplasma gondii adenosine kinase. Acta Crystallogr D Biol Crystallogr 63:126-34
Zhang, Yan; El Kouni, Mahmoud H; Ealick, Steven E (2006) Structure of Toxoplasma gondii adenosine kinase in complex with an ATP analog at 1.1 angstroms resolution. Acta Crystallogr D Biol Crystallogr 62:140-5
Rais, Reem H; Al Safarjalani, Omar N; Yadav, Vikas et al. (2005) 6-Benzylthioinosine analogues as subversive substrate of Toxoplasma gondii adenosine kinase: activities and selective toxicities. Biochem Pharmacol 69:1409-19

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