Pathophysiological interplay between O-GlcNAc transferase and the Machado-Joseph disease protein ataxin-3


Aberrant O-GlcNAcylation, a protein posttranslational modification defined by the O-linked attachment of the monosaccharide N-acetylglucosamine (O-GlcNAc), has been implicated in neurodegenerative diseases. However, although many neuronal proteins are substrates for O-GlcNAcylation, this process has not been extensively investigated in polyglutamine disorders. We aimed to evaluate the enzyme O-GlcNAc transferase (OGT), which attaches O-GlcNAc to target proteins, in Machado-Joseph disease (MJD). MJD is a neurodegenerative condition characterized by ataxia and caused by the expansion of a polyglutamine stretch within the deubiquitinase ataxin-3, which then present increased propensity to aggregate. By analyzing MJD cell and animal models, we provide evidence that OGT is dysregulated in MJD, therefore compromising the O-GlcNAc cycle. Moreover, we demonstrate that wild-type ataxin-3 modulates OGT protein levels in a proteasome-dependent manner, and we present OGT as a substrate for ataxin-3. Targeting OGT levels and activity reduced ataxin-3 aggregates, improved protein clearance and cell viability, and alleviated motor impairment reminiscent of ataxia of MJD patients in zebrafish model of the disease. Taken together, our results point to a direct interaction between OGT and ataxin-3 in health and disease and propose the O-GlcNAc cycle as a promising target for the development of therapeutics in the yet incurable MJD.

Authors Pereira Sena P, Weber JJ, Watchon M, Robinson KJ, Wassouf Z, Hauser S, Helm J, Abeditashi M, Schmidt J, Hübener-Schmid J, Schöls L, Laird AS, Riess O, Schmidt T
Journal Proceedings of the National Academy of Sciences of the United States of America
Publication Date 2021 Nov 23;118(47)
PubMed 34785590
PubMed Central PMC8617493
DOI 10.1073/pnas.2025810118

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