O‐GlcNAcylation of TDP‐43 suppresses proteinopathies and promotes TDP‐43’s mRNA splicing activity

Abstract

Pathological TDP-43 aggregation is characteristic of several neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD-TDP); however, how TDP-43 aggregation and function are regulated remain poorly understood. Here, we show that O-GlcNAc transferase OGT-mediated O-GlcNAcylation of TDP-43 suppresses ALS-associated proteinopathies and promotes TDP-43's splicing function. Biochemical and cell-based assays indicate that OGT's catalytic activity suppresses TDP-43 aggregation and hyperphosphorylation, whereas abolishment of TDP-43 O-GlcNAcylation impairs its RNA splicing activity. We further show that TDP-43 mutations in the O-GlcNAcylation sites improve locomotion defects of larvae and adult flies and extend adult life spans, following TDP-43 overexpression in Drosophila motor neurons. We finally demonstrate that O-GlcNAcylation of TDP-43 promotes proper splicing of many mRNAs, including STMN2, which is required for normal axonal outgrowth and regeneration. Our findings suggest that O-GlcNAcylation might be a target for the treatment of TDP-43-linked pathogenesis.

Bicyclic Picomolar OGA Inhibitors Enable Chemoproteomic Mapping of Its Endogenous Post-translational Modifications

“…We next used DNJNAc-6S-NBn-Biotin to precipitate OGA from bovine brain tissue (bOGA). We selected bovine brain because OGA was first isolated from this tissue, where the enzyme is particularly abundant, in view of the therapeutic potential of OGA inhibition in various neurodegenerative diseases. − We used DNJNAc-6S-NBn-Biotin concentrations that would be maximized but not exceed available sites of streptavidin on a convenient volume of beads (100 μL). Following the precipitation experiment, for which we performed a parallel control involving blocking of bOGA binding by adding the potent inhibitor Thiamet-G, analysis of the OGA immunoreactivity by immunoblot (Figure D) showed that DTT elution resulted in release of OGA from the resin.…”

“…In accord with its biochemical and physiological roles, enhancing O-GlcNAc levels has been shown to be protective in various animal models of disease. Within the brain in particular, increased O-GlcNAc levels are protective against ischemic injuries , and various neurodegenerative disorders. − …”

Combining Selective Enrichment and a Boosting Approach to Globally and Site-Specifically Characterize Protein Co-translational O-GlcNAcylation

“…48 Additionally, O-GlcNAcylation of TDP-43 can promote its RNA splicing function. 49 Conversely, the OGT expression is regulated by intron retention, which dynamically responds to the overall O-GlcNAcylation level in cells. 50 Three proteins in the nuclear pore complex (NPC) were modified with co-translational O-GlcNAcylation (NUP214, NUP153, and RANBP2).…”

Regulation of Cellular Ribonucleoprotein Granules: From Assembly to Degradation via Post-translational Modification

“…The phosphorylation of TDP-43 could induce or reduce aggregation in a context-dependent manner [122]. Intriguingly, the O-GlcNAcylation of TDP-43 inhibits its hyperphosphorylation, resulting in the suppression of TDP-43 aggregates [123]. Additionally, phosphorylation can induce the ubiquitination of RBPs within aggregates and promote proteasomal or autophagic degradation, showing that PTMs can promote other PTMs.…”