O-GlcNAcylation links TxNIP to inflammasome activation in pancreatic β cells

Thioredoxin interacting protein( TxNIP), which strongly responds to glucose, has emerged as a central mediator of glucotoxicity in pancreatic β cells. TxNIPis a scaffold proteininteracting with target proteinsto inhibit or stimulate their activity. Recent studies reported that high glucose stimulates the interaction of TxNIPwith the inflammasomeprotein NLRP3 (NLR family, pyrin domaincontaining 3) to increase interleukin-1 β (IL1β) secretion by pancreatic β cells. To better understand the regulation of TxNIPby glucose in pancreatic β cells, we investigated the implication of O-linked β- N-acetylglucosamine(O-GlcNAcylation) in regulating TxNIPat the posttranslational level. O-GlcNAcylation of proteins is controlled by two enzymes: the O-GlcNAc transferase(OGT), which transfers a monosaccharide to serine/threonine residues on target proteins, and the O-GlcNAcase(OGA), which removes it. Our study shows that TxNIPis subjected to O-GlcNAcylation in response to high glucose concentrations in β cell lines. Modification of the O-GlcNAcylation pathway through manipulation of OGT or OGA expression or activity significantly modulates TxNIPO-GlcNAcylation in INS1 832/13 cells. Interestingly, expression and O-GlcNAcylation of TxNIPappeared to be increased in islets of diabetic rodents. At the mechanistic level, the induction of the O-GlcNAcylation pathway in human and rat islets promotes inflammasomeactivation as evidenced by enhanced cleaved IL1β. Overexpression of OGT in HEK293 or INS1 832/13 cells stimulates TxNIPand NLRP3 interaction, while reducing TxNIPO-GlcNAcylation through OGA overexpression destabilizes this interaction. Altogether, our study reveals that O-GlcNAcylation represents an important regulatory mechanism for TxNIPactivity in β cells.