Metabolic Inhibitors of O‐GlcNAc Transferase That Act In Vivo Implicate Decreased O‐GlcNAc Levels in Leptin‐Mediated Nutrient Sensing

Abstract

O‐Linked glycosylation of serine and threonine residues of nucleocytoplasmic proteins with N‐acetylglucosamine (O‐GlcNAc) residues is catalyzed by O‐GlcNAc transferase (OGT). O‐GlcNAc is conserved within mammals and is implicated in a wide range of physiological processes. Herein, we describe metabolic precursor inhibitors of OGT suitable for use both in cells and in vivo in mice. These 5‐thiosugar analogues of N‐acetylglucosamine are assimilated through a convergent metabolic pathway, most likely involving N‐acetylglucosamine‐6‐phosphate de‐N‐acetylase (NAGA), to generate a common OGT inhibitor within cells. We show that of these inhibitors, 2‐deoxy‐2‐N‐hexanamide‐5‐thio‐d‐glucopyranoside (5SGlcNHex) acts in vivo to induce dose‐ and time‐dependent decreases in O‐GlcNAc levels in various tissues. Decreased O‐GlcNAc correlates, both in vitro within adipocytes and in vivo within mice, with lower levels of the transcription factor Sp1 and the satiety‐inducing hormone leptin, thus revealing a link between decreased O‐GlcNAc levels and nutrient sensing in peripheral tissues of mammals.

O-GlcNAcylation and its role in the immune system

“…The development of potent and selective OGT or OGA inhibitors may thus possess potential for the treatment of diseases that show abnormal O-GlcNAcylation. Indeed, several OGT or OGA inhibitors have been developed [103,[160][161][162]. OGA inhibitors have recently entered early clinical trials for the treatment of Progressive Supranuclear Palsy [163] as O-GlcNAcylation of Tau blocks the pathological effects of phosphorylation and aggregation of Tau [76].…”

Energetic adaptations: Metabolic control of endocytic membrane traffic

“…The modification of proteins with O‐GlcNAc is thus limited by UDP‐GlcNAc availability and occurs in a specific manner on serine or threonine residues of nearly 4000 proteins, thus modulating protein‐protein interactions, phosphorylation and enzymatic stability . In this manner, protein modification by O‐GlcNAc controls a wide range of processes including signaling networks, transcription, cell metabolism, amino acid and nucleotide metabolism, nutrient sensing and the cell stress response . Within this broad control of cell physiology, it is emerging that O‐GlcNAc modification also controls specific aspects of endocytic membrane traffic, including that of proteins that regulate membrane transport of metabolites, ions and proteins, although much remains to be understood about this phenomenon.…”

O‐GlcNAc Transferase: Structural Characteristics, Catalytic Mechanism and Small‐Molecule Inhibitors

“…[44] 5SGlcNHex inhibits OGT and decreases O-GlcNAc levels in cells and in vivo. [44] 5SGlcNHex is a substrate for GlcNAc kinase (GNK) and for Nacetyl-glucosamine-6-phosphate de-N-acetylase (NAGA). It, however, is not a substrate for phosphoglucosamine mutase (AGM) which catalyzes a transfer of phosphate group from C6 position to the anomeric carbon (C1).…”

“…[43] 5SGlcNHex metabolic precursor: 2-Deoxy-2-N-hexanamide-5-thio-d-glucopyranose (5SGlcNHex) has been developed as an in vivo OGT inhibitor by addressing the inherent low aqueoussolubility problem of Ac 4 -5SGlcNAc. [44] This inhibitor properly balances between its lipophilicity and hydrophilicity rendering it to diffuse into cells yet to be water-soluble. Its hydrophilic property is conferred from several unprotected hydroxyl groups whereas its lipophilic property is arisen from the attached hydrophobic N-hexanoyl substituent at C2.…”