Development of better anti Pneumocystis (Pc) drugs is needed. Humans and other mammals do not have the enzymes for producing C 24 alkylated or C 22 desaturated sterols, and when these compounds are present in the parasites, they represent putative """"""""metabolic sterols"""""""" and """"""""new"""""""" anti sterol drug targets. """"""""Metabolic sterols"""""""" are those that have the precise stereochemical structural features required for proper functioning of the organism's membranes, and are particularly relevant to the development of chemotherapeutic agents against parasitic infections. Pneumocystis carinii appears to de novo synthesize isoprenoids. HMG CoA reductase activity was detected, and radiolabeled precursors were incorporated into P. carinii sterols, ubiquinones and other products. Ergosterol (the dominant sterol of """"""""typical"""""""" fungi) was not detected in PC, but a number of delta 7C-24 alkylated sterols, similar to those found in some plants and in rust fungi, were identified. Pc was also found to have the ubiquinone (coenzyme Q) homologs, CoQ9and CoQ10; CoQ10was absent in the lung lipids of the rat host. Coenzyme Q is made of two parts, 1), the polyprenyl chain which varies in length, and is the basis for the designation of homologs, and 2) the aromatic moiety, which is made from dietary tyrosine in mammals, but is synthesized de novo in most plants, fungi and bacteria from chorismate, which is derived from the shikimate pathway (absent in mammals). The shikimate pathway leads to the formation of several other important metabolites, including aromatic amino acids, folate and Vitamin K. The project focuses on two novel targets, """"""""metabolic sterols"""""""" and ubiquinone, especially those compounds that are present in Pc but absent in mammals. Included are studies on structural analyses employing a variety of chromatographic and mass spectral analyses. Biosynthetic pathways will be examined by metabolism of radiolabeled precursors. Also, sterol inhibitors with known specificity for a reaction will be utilized at low concentrations to cause the accumulation of precursors of the blocked reaction. Identification of the precursors will allow the elucidation of the biosynthetic pathway(s) functional in the organism.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI038758-03
Application #
2653866
Study Section
AIDS and Related Research Study Section 4 (ARRD)
Project Start
1996-02-01
Project End
2000-01-31
Budget Start
1998-02-01
Budget End
2000-01-31
Support Year
3
Fiscal Year
1998
Total Cost
Indirect Cost
Name
University of Cincinnati
Department
Biology
Type
Schools of Arts and Sciences
DUNS #
City
Cincinnati
State
OH
Country
United States
Zip Code
45221
Giner, Jose-Luis; Zhao, Hui; Beach, David H et al. (2002) Comprehensive and definitive structural identities of Pneumocystis carinii sterols. J Lipid Res 43:1114-24
Kaneshiro, Edna S (2002) Is Pneumocystis a plant? J Eukaryot Microbiol 49:367-73
Kaneshiro, Edna S (2002) Sterol biosynthesis in Pneumocystis: unique steps that define unique targets. Drug Resist Updat 5:259-68
Kaneshiro, E S (2001) Are cytochrome b gene mutations the only cause of atovaquone resistance in Pneumocystis? Drug Resist Updat 4:322-9
Amit, Z; Kaneshiro, E S (2001) Heterogeneity of Pneumocystis sterol profiles of samples from different sites in the same pair of lungs suggests coinfection by distinct organism populations. J Clin Microbiol 39:1137-9
Kaneshiro, E S; Sul, D; Hazra, B (2000) Effects of atovaquone and diospyrin-based drugs on ubiquinone biosynthesis in Pneumocystis carinii organisms. Antimicrob Agents Chemother 44:14-8
Kaneshiro, E S; Wyder, M A (2000) C27 to C32 sterols found in Pneumocystis, an opportunistic pathogen of immunocompromised mammals. Lipids 35:317-24
Kaneshiro, E S; Collins, M S; Cushion, M T (2000) Inhibitors of sterol biosynthesis and amphotericin B reduce the viability of pneumocystis carinii f. sp. carinii. Antimicrob Agents Chemother 44:1630-8
Kaneshiro, E S; Collins, M; Cushion, M T (1999) Effects of sterol inhibitors on the ATP content of Pneumocystis carinii. J Eukaryot Microbiol 46:142S-143S
Kaneshiro, E S; Amit, Z; Swonger, M M et al. (1999) Pneumocysterol [(24Z)-ethylidenelanost-8-en-3beta-ol], a rare sterol detected in the opportunistic pathogen Pneumocystis carinii hominis: structural identity and chemical synthesis. Proc Natl Acad Sci U S A 96:97-102

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