Selective inhibitors of the glycosylphosphatidylinositol biosynthetic pathway of Trypanosoma brucei.
Synthetic analogues of D-GlcNalpha1-6D-myo-inositol-1-HPO(4)-3(sn-1, 2-diacylglycerol) (GlcN-PI), with the 2-position of the inositol residue substituted with an O-octyl ether [D-GlcNalpha1-6D-(2-O-octyl)myo-inositol-1-HPO(4)-3-sn-1, 2-dipalmitoylglycerol; GlcN-(2-O-octyl) PI] or O-hexadecyl ether [D-GlcNalpha1-6D-(2-O-hexadecyl)myo-inositol-1-HPO(4)-3-sn-1, 2-dipalmitoylglycerol; GlcN-(2-O-hexadecyl)PI], were tested as substrates or inhibitors of glycosylphosphatidylinositol (GPI) biosynthetic pathways using cell-free systems of the protozoan parasite Trypanosoma brucei (the causative agent of human African sleeping sickness) and human HeLa cells. Neither these compounds nor their N-acetyl derivatives are substrates or inhibitors of GPI biosynthetic enzymes in the HeLa cell-free system but are potent inhibitors of GPI biosynthesis in the T.brucei cell-free system. GlcN-(2-O-hexadecyl)PI was shown to inhibit the first alpha-mannosyltransferase of the trypanosomal GPI pathway. The N-acetylated derivative GlcNAc-(2-O-octyl)PI is a substrate for the trypanosomal GlcNAc-PI de-N-acetylase and this compound, like GlcN-(2-O-octyl)PI, is processed predominantly to Man(2)GlcN-(2-O-octyl)PI by the T.brucei cell-free system. Both GlcN-(2-O-octyl)PI and GlcNAc(2-O-octyl)PI also inhibit inositol acylation of Man(1-3)GlcN-PI and, consequently, the addition of the ethanolamine phosphate bridge in the T.brucei cell-free system. The data establish these substrate analogues as the first generation of in vitro parasite GPI pathway-specific inhibitors.
Smith
T K
TK
Division of Molecular Parasitology & Biological Chemistry, Department of Biochemistry, University of Dundee, Scotland.
Sharma
D K
DK
Crossman
A
A
Brimacombe
J S
JS
Ferguson
M A
MA
D000215:Acylation / Q000187:drug effects; D000818:Animals; D003902:Detergents / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D004987:Ethers / Q000494:pharmacology; D006017:Glycolipids / Q000032:analysis; D017261:Glycosylphosphatidylinositols / Q000096:biosynthesis*; D006367:HeLa Cells; D006801:Humans; D008364:Mannosyltransferases / Q000378:metabolism; D015394:Molecular Structure; D010716:Phosphatidylinositols / Q000494:pharmacology; D013379:Substrate Specificity; D014346:Trypanosoma brucei brucei / Q000201:enzymology*
D003902:Detergents; D004791:Enzyme Inhibitors; D004987:Ethers; D006017:Glycolipids; D017261:Glycosylphosphatidylinositols; D010716:Phosphatidylinositols; D008364:Mannosyltransferases