13 research outputs found
O-GlcNAcase Fragment Discovery with Fluorescence Polarimetry
The
attachment of the sugar N-acetyl-D-glucosamine (GlcNAc) to
specific serine and threonine residues on proteins is referred to
as protein O-GlcNAcylation. O-GlcNAc transferase (OGT) is the enzyme
responsible for carrying out the modification, while O-GlcNAcase (OGA)
reverses it. Protein O-GlcNAcylation has been implicated in a wide
range of cellular processes including transcription, proteostasis,
and stress response. Dysregulation of O-GlcNAc has been linked to
diabetes, cancer, and neurodegenerative and cardiovascular disease.
OGA has been proposed to be a drug target for the treatment of Alzheimer’s
and cardiovascular disease given that increased O-GlcNAc levels appear
to exert a protective effect. The search for specific, potent, and
drug-like OGA inhibitors with bioavailability in the brain is therefore
a field of active research, requiring orthogonal high-throughput assay
platforms. Here, we describe the synthesis of a novel probe for use
in a fluorescence polarization based assay for the discovery of inhibitors
of OGA. We show that the probe is suitable for use with both human
OGA, as well as the orthologous bacterial counterpart from <i>Clostridium perfringens</i>, <i>Cp</i>OGA, and the
lysosomal hexosaminidases HexA/B. We structurally characterize <i>Cp</i>OGA in complex with a ligand identified from a fragment
library screen using this assay. The versatile synthesis procedure
could be adapted for making fluorescent probes for the assay of other
glycoside hydrolases
A mutant O-GlcNAcase enriches Drosophila developmental regulators
YesProtein O-GlcNAcylation is a reversible post-translational modification of serines/threonines on
nucleocytoplasmic proteins. It is cycled by the enzymes O-GlcNAc transferase (OGT) and O-GlcNAc hydrolase
(O-GlcNAcase or OGA). Genetic approaches in model organisms have revealed that protein O-GlcNAcylation is
essential for early embryogenesis. Drosophila melanogaster OGT/supersex combs (sxc) is a polycomb gene,
null mutants of which display homeotic transformations and die at the pharate adult stage. However, the identities
of the O-GlcNAcylated proteins involved, and the underlying mechanisms linking these phenotypes to embryonic
development, are poorly understood. Identification of O-GlcNAcylated proteins from biological samples is
hampered by the low stoichiometry of this modification and limited enrichment tools. Using a catalytically inactive
bacterial O-GlcNAcase mutant as a substrate trap, we have enriched the O-GlcNAc proteome of the developing
Drosophila embryo, identifying, amongst others, known regulators of Hox genes as candidate conveyors of OGT
function during embryonic development.Wellcome Trust Investigator Award (110061); MRC grant (MC_UU_12016/5); and Royal Society Research Grant
A mutant O-GlcNAcase as a probe to reveal global dynamics of protein O-GlcNAcylation during Drosophila embryonic development
Nucleocytoplasmic protein O-GlcNAcylation is essential for embryogenesis. The dynamics of the O-GlcNAc proteome and the underlying mechanistic biology linking it to embryonic development is not understood. Harnessing the unusual properties of an O-GlcNAcase mutant that binds O-GlcNAc sites with nanomolar affinity, we uncover changes in O-GlcNAc proteins as a function of Drosophila development
The early metazoan Trichoplax adhaerens possesses a functional O-GlcNAc system
Protein O-GlcNAcylation is a reversible post-translational signaling modification of nucleocytoplasmic proteins that is essential for embryonic development in bilateria. In a search for a reductionist model to study O-GlcNAc signaling, we discovered the presence of functional O-GlcNAc transferase (OGT), O-GlcNAcase (OGA), and nucleocytoplasmic protein O-GlcNAcylation in the most basal extant animal, the placozoan Trichoplax adhaerens. We show via enzymatic characterization of Trichoplax OGT/OGA and genetic rescue experiments in Drosophila melanogaster that these proteins possess activities/functions similar to their bilaterian counterparts. The acquisition of O-GlcNAc signaling by metazoa may have facilitated the rapid and complex signaling mechanisms required for the evolution of multicellular organisms