Spatiotemporal gating of SIRT1 functions by O-GlcNAcylation is essential for liver metabolic switching and prevents hyperglycemia
Inefficient physiological transitions are known to cause metabolic disorders. Therefore, investigating mechanisms that constitute molecular switches in a central metabolic organ like the liver becomes crucial. Specifically, upstream mechanisms that control temporal engagement of transcription factor...
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| Published in: | Proceedings of the National Academy of Sciences - PNAS Vol. 117; no. 12; pp. 6890 - 6900 |
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| Main Authors: | , , , , , , , , , |
| Format: | Journal Article |
| Language: | English |
| Published: |
United States
National Academy of Sciences
24-03-2020
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| Series: | PNAS Plus |
| Subjects: | |
| Online Access: | Get full text |
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| Summary: | Inefficient physiological transitions are known to cause metabolic disorders. Therefore, investigating mechanisms that constitute molecular switches in a central metabolic organ like the liver becomes crucial. Specifically, upstream mechanisms that control temporal engagement of transcription factors, which are essential to mediate physiological fed–fast–refed transitions are less understood. SIRT1, a NAD⁺-dependent deacetylase, is pivotal in regulating hepatic gene expression and has emerged as a key therapeutic target. Despite this, if/how nutrient inputs regulate SIRT1 interactions, stability, and therefore downstream functions are still unknown. Here, we establish nutrient-dependent O-GlcNAcylation of SIRT1, within its N-terminal domain, as a crucial determinant of hepatic functions. Our findings demonstrate that during a fastedto- refed transition, glycosylation of SIRT1 modulates its interactions with various transcription factors and a nodal cytosolic kinase involved in insulin signaling. Moreover, sustained glycosylation in the fed state causes nuclear exclusion and cytosolic ubiquitin-mediated degradation of SIRT1. This mechanism exerts spatiotemporal control over SIRT1 functions by constituting a previously unknown molecular relay. Of note, loss of SIRT1 glycosylation discomposed these interactions resulting in aberrant gene expression, mitochondrial dysfunctions, and enhanced hepatic gluconeogenesis. Expression of nonglycosylatable SIRT1 in the liver abrogated metabolic flexibility, resulting in systemic insulin resistance, hyperglycemia, and hepatic inflammation, highlighting the physiological costs associated with its overactivation. Conversely, our study also reveals that hyperglycosylation of SIRT1 is associated with aging and high-fat– induced obesity. Thus, we establish that nutrient-dependent glycosylation of SIRT1 is essential to gate its functions and maintain physiological fitness. |
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| Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 Edited by Marc Montminy, The Salk Institute for Biological Studies, La Jolla, CA, and approved February 13, 2020 (received for review June 10, 2019) 1Present address: Division of Cell Biology and Molecular Medicine, Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Brisbane, QLD 4072, Australia. Author contributions: T.C. and U.K.-S. designed research; T.C., B.M., H.P.B., A.C., N.S., S.B., A.R., S.S.K., and U.K.-S. performed research; T.C., B.M., A.C., and A.S. contributed new reagents/analytic tools; T.C., B.M., H.P.B., A.C., N.S., S.B., A.R., S.S.K., and U.K.-S. analyzed data; and T.C., B.M., S.B., and U.K.-S. wrote the paper. |
| ISSN: | 0027-8424 1091-6490 |
| DOI: | 10.1073/pnas.1909943117 |