Post-translationalO-GlcNAcylation is essential for nuclear pore integrity and maintenance of the pore selectivity filter

Abstract

O-glycosylation of the nuclear pore complex (NPC) by O-linked N-acetylglucosamine (O-GlcNAc) is conserved within metazoans. Many nucleoporins (Nups) comprising the NPC are constitutively O-GlcNAcylated, but the functional role of this modification remains enigmatic. We show that loss of O-GlcNAc, induced by either inhibition of O-GlcNAc transferase (OGT) or deletion of the gene encoding OGT, leads to decreased cellular levels of a number of natively O-GlcNAcylated Nups. Loss of O-GlcNAc enables increased ubiquitination of these Nups and their increased proteasomal degradation. The decreased half-life of these deglycosylated Nups manifests in their gradual loss from the NPC and a downstream malfunction of the nuclear pore selective permeability barrier in both dividing and post-mitotic cells. These findings define a critical role of O-GlcNAc modification of the NPC in maintaining its composition and the function of the selectivity filter. The results implicate NPC glycosylation as a regulator of NPC function and reveal the role of conserved glycosylation of the NPC among metazoans.

Mapping and Quantification of Over 2000 O-linked Glycopeptides in Activated Human T Cells with Isotope-Targeted Glycoproteomics (Isotag)

“…OGlcNAcylation of nuclear pore proteins has been proposed to regulate their stability, and in addition, their permissiveness to nucleocytoplasmic transport (22,60). Specific O-GlcNAc sites (e.g., on NUP98) are significantly upregulated during T cell activation, as shown in Figure 4A.…”

“…However, the relationship between O-GlcNAc and phosphorylation is not simply reciprocal antagonism, as the two modifications may also regulate each other even when they target different sites (15)(16)(17)(18)(19)(20). Similar to other types of PTMs (e.g., phosphorylation), O-GlcNAc has been demonstrated to influence the activity of many proteins, including transcription factors (15), kinases (21), and nuclear pore proteins (22). Owing to its regulatory importance, it is not surprising then that abnormal levels of O-GlcNAc have been linked to several diseases, including diabetes (23), cancer (24, 25), and neurodegeneration (26,27).…”

Global Analysis of O-GlcNAc Glycoproteins in Activated Human T Cells

“…2), the O-GlcNAc modification likely holds functional importance. Indeed, recent studies showed that O-GlcNAc glycosylation of nuclear pore proteins prevents their proteasomal degradation (85) and facilitates the transport of protein cargo (86). Interestingly, phosphorylation of nuclear pore proteins, including NUP214, also increases after T cell activation (83), which raises the possibility of multiple posttranslational modifications working synergistically to regulate nuclear pore function in activated T cells.…”

“…3A, 3B). The transcription factor c-myc is clearly essential for increased O-GlcNAc levels in activated T cells (85), probably due, in part, to its role in driving expression of nutrient transporters (75). At the same time, OGT activity is critical for stabilizing c-myc expression (35,87).…”

A Sweet Embrace: Control of Protein–Protein Interactions by O-Linked β-N-Acetylglucosamine

“…57 The authors showed that pharmacological inhibition or genetic deletion of OGT eliminated Nup glycosylation, enhanced Nup ubiquitination, and shortened Nup protein half-lives. 57 As a result, the nuclear pore selective permeability barrier, which gates nuclear–cytoplasmic trafficking, collapsed in both mitotic and non-dividing cells. 57 Taken together, these results suggest that O-GlcNAc-mediated protein–protein interactions among Nups are required for their stability, and for pore structure and function, at least in vertebrate cells.…”