Quantitative regulation of nuclear pore complex proteins by O-GlcNAcylation

The nuclear pore complex (NPC) is a macromolecular assembly consisting of approximately 30 different proteins called nucleoporins. Several nucleoporins are O-GlcNAcylated, which is a post-translational modification in which the monosaccharide β-N-acetylglucosamine (GlcNAc) is attached to serine or threonine residues within proteins. However, the biological significance of this modification on nucleoporins remains obscure. Here we found that Nup62 and Nup88 protein levels were significantly decreased upon knockdown of O-GlcNAc transferase (OGT), which catalyzes the O-GlcNAcylation of intracellular proteins. Although Nup88, unlike Nup62, was not recognized by an anti-O-GlcNAc antibody or WGA–HRP, knockdown of Nup62 caused a reduction in Nup88 protein levels, suggesting that the observed decrease in Nup88 in OGT knocked-down cells is due to a decrease in Nup62. Furthermore, we found that Nup88 was preferentially associated with O-GlcNAcylated Nup62 compared with non-O-GlcNAcylated Nup62. These results indicate that Nup62 protein levels are primarily maintained by O-GlcNAcylation and that Nup88 is quantitatively regulated through its interaction with O-GlcNAcylated Nup62.