Chemical validation of GPI biosynthesis as a drug target against African sleeping sickness

Abstract

It has been suggested that compounds affecting glycosylphosphatidylinositol (GPI) biosynthesis in bloodstream form Trypanosoma brucei should be trypanocidal. We describe cell-permeable analogues of a GPI intermediate that are toxic to this parasite but not to human cells. These analogues are metabolized by the T. brucei GPI pathway, but not by the human pathway. Closely related nonmetabolizable analogues have no trypanocidal activity. This represents the first direct chemical validation of the GPI biosynthetic pathway as a drug target against African human sleeping sickness. The results should stimulate further inhibitor design and synthesis and encourage the search for inhibitors in natural product and synthetic compound libraries.

Structural insight into the glycosylphosphatidylinositol transamidase subunits PIG-K and PIG-S from yeast

“…The GPI lipid anchor is a complex organic structure made up of an inositol phospholipid, a tetrasaccharide with variable elaborations and phosphoethanolamine subunits (Paulick and Bertozzi, 2008). Although the general outline of the GPI lipid anchor biosynthesis pathway is common among eukaryotes, there are distinctive taxon-specific differences that might be useful for species-specific inhibitor design (Izquierdo et al, 2009;Smith et al, 2004;Urbaniak et al, 2008).…”

Glycosyltransferases and their Assays

“…[61] Intact GPI anchors are essential for the viability of bloodstream T. brucei, and their biosynthesis has been validated chemically and genetically as a target for the development of novel, antitrypanosomal drugs. [62,63] GPI-anchor biosynthesis [64] involves several mannosyltransferases (ManT), which use dolicholphosphate mannose (DPM) as their donor [65] (Scheme 4). DPM formation in turn is catalysed by the GDPMan-dependent ManT, dolicholphosphate mannose synthase (DPMS) that acts as a "gatekeeper enzyme" for GPI-anchor biosynthesis.…”

The synthesis of some deoxygenated analogues of early intermediates in the biosynthesis of glycosylphosphatidylinositol (GPI) membrane anchors

“…4 Thus there is a fundamental difference between the trypanosomal and mammalian biosynthetic pathways with respect to the timing of inositol 2-acylation that might be exploited in the development of parasite-specific therapeutic agents. A synthetic analogue displaying parasite-specific inhibition is a-D D -GlcpN-2-O-hexadecyl-PI (4), which inhibits trypanosomal MT-1 in a cell-free system but is not a substrate for HeLa MT-1 despite being a close analogue of the proven substrate a-D DGlcpN-2-O-hexadecanoyl-PI (5). 5 To date we have described the synthesis of substrate analogues of the developing GPI anchors 1 and 2 having structural modifications to the phospholipid, a-D D -glucosamine and D D -myo-inositol components.…”

“…A synthetic analogue displaying parasite-specific inhibition is a-D D -GlcpN-2-O-hexadecyl-PI (4), which inhibits trypanosomal MT-1 in a cell-free system but is not a substrate for HeLa MT-1 despite being a close analogue of the proven substrate a-D DGlcpN-2-O-hexadecanoyl-PI (5). 5 To date we have described the synthesis of substrate analogues of the developing GPI anchors 1 and 2 having structural modifications to the phospholipid, a-D D -glucosamine and D D -myo-inositol components. [6][7][8][9] Attention herein focuses on further modifications to the a-D D -glucosamine residue of compounds 1 and 2, which has been deoxygenated at each of positions 3, 4 and 6 with the intent of establishing which of these OH groups are involved in essential hydrogen bonding in the active site of the respective enzymes.…”