Synthesis of Galactosylated Glycosylphosphatidylinositol Derivatives from Trypanosoma brucei.

Trypanosoma brucei uses variant surface glycoproteins (VSGs) to evade the host immune system and ensure parasitic longevity in animals and humans. VSGs are attached to the cell membrane by complex glycosylphosphatidylinositol anchors (GPI). Distinguishing structural feature of VSG GPIs are multiple α- and ß-galactosides attached to the conserved GPI core structure. T. brucei GPIs have been associated with macrophage activation and alleviation of parasitemia during infection, acting as disease onset delaying antigens. Literature reports that link structural modifications in the GPIs to changes in biological activity are contradictory. We have established a synthetic route to prepare structurally overlapping GPI derivatives bearing different T. brucei characteristic structural modifications. The GPI collection will be used to assess the effect of galactosylation and phosphorylation on T. brucei GPI immunomodulatory activity, and to perform an epitope mapping of this complex glycolipid as potential diagnostic marker for Trypanosomiasis. A strategy for the synthesis of a complete α-tetragalactoside using the 2-naphthylmethyl protecting group and for subsequent attachment of GPI fragments to peptides is presented.

Small-molecule activation of OGG1 increases oxidative DNA damage repair by gaining a new function.

Oxidative DNA damage is recognized by 8-oxoguanine (8-oxoG) DNA glycosylase 1 (OGG1), which excises 8-oxoG, leaving a substrate for apurinic endonuclease 1 (APE1) and initiating repair. Here, we describe a small molecule (TH10785) that interacts with the phenylalanine-319 and glycine-42 amino acids of OGG1, increases the enzyme activity 10-fold, and generates a previously undescribed ß,δ-lyase enzymatic function. TH10785 controls the catalytic activity mediated by a nitrogen base within its molecular structure. In cells, TH10785 increases OGG1 recruitment to and repair of oxidative DNA damage. This alters the repair process, which no longer requires APE1 but instead is dependent on polynucleotide kinase phosphatase (PNKP1) activity. The increased repair of oxidative DNA lesions with a small molecule may have therapeutic applications in various diseases and aging.

Design, synthesis, inhibition studies, and molecular modeling of pepstatin analogues addressing different secreted aspartic proteinases of Candida albicans.

The family of secreted aspartic proteinases is known as an important virulence factor of yeast infections by Candida albicans in particular, which is the most common fungal pathogen for humans with respect to systemic disease. Due to the continuing increase of drug resistant strains, these proteinases are currently considered as promising drug target candidates. Based on the known Sap2-substrate specificity data and X-ray analyses of Sap/inhibitor complexes, three libraries of inhibitors were designed and synthesized by modifying the structure of pepstatin A, a common non-selective aspartic proteinase inhibitor, at the P3, P2, or P2' position. These novel inhibitors showed high inhibitory potencies for the isoenzymes Sap1, Sap3, Sap5 and Sap6. Then, the affinity and selectivity of the peptide ligands were investigated by molecular modeling, highlighting new key structural information for the design of potent and selective anti-virulence agents targeting Candida albicans.