β4GalT1 Mediates PPARγ N-Glycosylation to Attenuate Microglia Inflammatory Activation

The inflammatory activation of microglia has double-edged effects in central nervous system (CNS) diseases. The ligand-activated transcriptional factor peroxisome proliferator-activated receptor γ (PPARγ) inhibits the inflammatory response. β-1,4-Galactosyltransferase Ι (β1, 4GalT1) mediates N-glycosylation. In this study, the N-glycosylation of PPARγ, as well as two N-linked glycosylation sites in its DNA binding domain (DBD), was identified. Disruption of both sites by site-directed mutagenesis completely abrogated the N-glycosylation of PPARγ. PPAR wild-type (WT) transfection inhibited the inflammatory activation of microglia, while the anti-inflammatory function of unglycosylated PPARγ was down-regulated. In addition, β1, 4GalT1 was shown to interact with PPARγ and to mediate PPARγ glycosylation. β1, 4GalT1 promoted PPARγ's anti-transcription and anti-inflammatory functions. Collectively, our findings define that β-1, 4GalT1 mediated PPARγ glycosylation to attenuate the inflammatory activation of microglia, which has implications for potential therapies for CNS inflammatory diseases.