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Lin CH, Liao CC, Chen MY, Chou TY. Feedback Regulation of O-GlcNAc Transferase through Translation Control to Maintain Intracellular O-GlcNAc Homeostasis. Int J Mol Sci 2021; 22:ijms22073463. [PMID: 33801653 PMCID: PMC8037101 DOI: 10.3390/ijms22073463] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2021] [Revised: 03/23/2021] [Accepted: 03/24/2021] [Indexed: 12/14/2022] Open
Abstract
Protein O-GlcNAcylation is a dynamic post-translational modification involving the attachment of N-acetylglucosamine (GlcNAc) to the hydroxyl groups of Ser/Thr residues on numerous nucleocytoplasmic proteins. Two enzymes are responsible for O-GlcNAc cycling on substrate proteins: O-GlcNAc transferase (OGT) catalyzes the addition while O-GlcNAcase (OGA) helps the removal of GlcNAc. O-GlcNAcylation modifies protein functions; therefore, dysregulation of O-GlcNAcylation affects cell physiology and contributes to pathogenesis. To maintain homeostasis of cellular O-GlcNAcylation, there exists feedback regulation of OGT and OGA expression responding to fluctuations of O-GlcNAc levels; yet, little is known about the molecular mechanisms involved. In this study, we investigated the O-GlcNAc-feedback regulation of OGT and OGA expression in lung cancer cells. Results suggest that, upon alterations in O-GlcNAcylation, the regulation of OGA expression occurs at the mRNA level and likely involves epigenetic mechanisms, while modulation of OGT expression is through translation control. Further analyses revealed that the eukaryotic translation initiation factor 4E-binding protein 1 (4E-BP1) contributes to the downregulation of OGT induced by hyper-O-GlcNAcylation; the S5A/S6A O-GlcNAcylation-site mutant of 4E-BP1 cannot support this regulation, suggesting an important role of O-GlcNAcylation. The results provide additional insight into the molecular mechanisms through which cells may fine-tune intracellular O-GlcNAc levels to maintain homeostasis.
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Affiliation(s)
- Chia-Hung Lin
- Division of Molecular Pathology, Department of Pathology and Laboratory Medicine, Taipei Veterans General Hospital, Taipei 11217, Taiwan;
| | - Chen-Chung Liao
- Metabolomics-Proteomics Research Center, National Yang-Ming University, Taipei 11221, Taiwan;
- Metabolomics-Proteomics Research Center, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan
| | - Mei-Yu Chen
- Faculty of Medicine, School of Medicine, National Yang-Ming University, Taipei 11221, Taiwan
- Faculty of Medicine, School of Medicine, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan
- Institute of Biochemistry and Molecular Biology, National Yang-Ming University, Taipei 11221, Taiwan
- Institute of Biochemistry and Molecular Biology, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan
- Cancer Progression Research Center, National Yang-Ming University, Taipei 11221, Taiwan
- Cancer Progression Research Center, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan
- Correspondence: (M.-Y.C.); (T.-Y.C.); Tel.: +886-2-2826-7269 (M.-Y.C.); +886-2-2875-7022 (T.-Y.C.)
| | - Teh-Ying Chou
- Division of Molecular Pathology, Department of Pathology and Laboratory Medicine, Taipei Veterans General Hospital, Taipei 11217, Taiwan;
- Cancer Progression Research Center, National Yang-Ming University, Taipei 11221, Taiwan
- Cancer Progression Research Center, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan
- Institute of Clinical Medicine, National Yang-Ming University, Taipei 11221, Taiwan
- Institute of Clinical Medicine, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan
- Correspondence: (M.-Y.C.); (T.-Y.C.); Tel.: +886-2-2826-7269 (M.-Y.C.); +886-2-2875-7022 (T.-Y.C.)
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Sun R, Cheng E, Velásquez C, Chang Y, Moore PS. Mitosis-related phosphorylation of the eukaryotic translation suppressor 4E-BP1 and its interaction with eukaryotic translation initiation factor 4E (eIF4E). J Biol Chem 2019; 294:11840-11852. [PMID: 31201269 PMCID: PMC6682726 DOI: 10.1074/jbc.ra119.008512] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Revised: 06/10/2019] [Indexed: 11/22/2022] Open
Abstract
Eukaryotic translation initiation factor 4E (eIF4E)–binding protein 1 (4E-BP1) inhibits cap-dependent translation in eukaryotes by competing with eIF4G for an interaction with eIF4E. Phosphorylation at Ser-83 of 4E-BP1 occurs during mitosis through the activity of cyclin-dependent kinase 1 (CDK1)/cyclin B rather than through canonical mTOR kinase activity. Here, we investigated the interaction of eIF4E with 4E-BP1 or eIF4G during interphase and mitosis. We observed that 4E-BP1 and eIF4G bind eIF4E at similar levels during interphase and mitosis. The most highly phosphorylated mitotic 4E-BP1 isoform (δ) did not interact with eIF4E, whereas a distinct 4E-BP1 phospho-isoform, EB-γ, phosphorylated at Thr-70, Ser-83, and Ser-101, bound to eIF4E during mitosis. Two-dimensional gel electrophoretic analysis corroborated the identity of the phosphorylation marks on the eIF4E-bound 4E-BP1 isoforms and uncovered a population of phosphorylated 4E-BP1 molecules lacking Thr-37/Thr-46–priming phosphorylation. Moreover, proximity ligation assays for phospho-4E-BP1 and eIF4E revealed different in situ interactions during interphase and mitosis. The eIF4E:eIF4G interaction was not inhibited but rather increased in mitotic cells, consistent with active translation initiation during mitosis. Phosphodefective substitution of 4E-BP1 at Ser-83 did not change global translation or individual mRNA translation profiles as measured by single-cell nascent protein synthesis and eIF4G RNA immunoprecipitation sequencing. Mitotic 5′-terminal oligopyrimidine RNA translation was active and, unlike interphase translation, resistant to mTOR inhibition. Our findings reveal the phosphorylation profiles of 4E-BP1 isoforms and their interactions with eIF4E throughout the cell cycle and indicate that 4E-BP1 does not specifically inhibit translation initiation during mitosis.
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Affiliation(s)
- Rui Sun
- Department of Microbiology and Molecular Genetics, University of Pittsburgh, Pittsburgh, Pennsylvania 15213.,Cancer Virology Program, UPMC Hillman Cancer Center, Pittsburgh, Pennsylvania 15213
| | - Erdong Cheng
- Department of Microbiology and Molecular Genetics, University of Pittsburgh, Pittsburgh, Pennsylvania 15213.,Cancer Virology Program, UPMC Hillman Cancer Center, Pittsburgh, Pennsylvania 15213
| | - Celestino Velásquez
- Department of Microbiology and Molecular Genetics, University of Pittsburgh, Pittsburgh, Pennsylvania 15213.,Cancer Virology Program, UPMC Hillman Cancer Center, Pittsburgh, Pennsylvania 15213
| | - Yuan Chang
- Cancer Virology Program, UPMC Hillman Cancer Center, Pittsburgh, Pennsylvania 15213 .,Department of Pathology, University of Pittsburgh, Pittsburgh, Pennsylvania 15213
| | - Patrick S Moore
- Department of Microbiology and Molecular Genetics, University of Pittsburgh, Pittsburgh, Pennsylvania 15213 .,Cancer Virology Program, UPMC Hillman Cancer Center, Pittsburgh, Pennsylvania 15213
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Dierschke SK, Miller WP, Favate JS, Shah P, Imamura Kawasawa Y, Salzberg AC, Kimball SR, Jefferson LS, Dennis MD. O-GlcNAcylation alters the selection of mRNAs for translation and promotes 4E-BP1-dependent mitochondrial dysfunction in the retina. J Biol Chem 2019; 294:5508-5520. [PMID: 30733333 PMCID: PMC6462503 DOI: 10.1074/jbc.ra119.007494] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Revised: 01/31/2019] [Indexed: 02/05/2023] Open
Abstract
Diabetes promotes the posttranslational modification of proteins by O-linked addition of GlcNAc (O-GlcNAcylation) to Ser/Thr residues of proteins and thereby contributes to diabetic complications. In the retina of diabetic mice, the repressor of mRNA translation, eIF4E-binding protein 1 (4E-BP1), is O-GlcNAcylated, and sequestration of the cap-binding protein eukaryotic translation initiation factor (eIF4E) is enhanced. O-GlcNAcylation has also been detected on several eukaryotic translation initiation factors and ribosomal proteins. However, the functional consequence of this modification is unknown. Here, using ribosome profiling, we evaluated the effect of enhanced O-GlcNAcylation on retinal gene expression. Mice receiving thiamet G (TMG), an inhibitor of the O-GlcNAc hydrolase O-GlcNAcase, exhibited enhanced retinal protein O-GlcNAcylation. The principal effect of TMG on retinal gene expression was observed in ribosome-associated mRNAs (i.e. mRNAs undergoing translation), as less than 1% of mRNAs exhibited changes in abundance. Remarkably, ∼19% of the transcriptome exhibited TMG-induced changes in ribosome occupancy, with 1912 mRNAs having reduced and 1683 mRNAs having increased translational rates. In the retina, the effect of O-GlcNAcase inhibition on translation of specific mitochondrial proteins, including superoxide dismutase 2 (SOD2), depended on 4E-BP1/2. O-GlcNAcylation enhanced cellular respiration and promoted mitochondrial superoxide levels in WT cells, and 4E-BP1/2 deletion prevented O-GlcNAcylation-induced mitochondrial superoxide in cells in culture and in the retina. The retina of diabetic WT mice exhibited increased reactive oxygen species levels, an effect not observed in diabetic 4E-BP1/2-deficient mice. These findings provide evidence for a mechanism whereby diabetes-induced O-GlcNAcylation promotes oxidative stress in the retina by altering the selection of mRNAs for translation.
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Affiliation(s)
- Sadie K Dierschke
- From the Department of Cellular and Molecular Physiology, Penn State College of Medicine, Hershey, Pennsylvania 17033
| | - William P Miller
- From the Department of Cellular and Molecular Physiology, Penn State College of Medicine, Hershey, Pennsylvania 17033
| | - John S Favate
- the Department of Genetics, Rutgers University, Piscataway, New Jersey 08854
| | - Premal Shah
- the Department of Genetics, Rutgers University, Piscataway, New Jersey 08854
| | - Yuka Imamura Kawasawa
- the Department of Pharmacology, Penn State College of Medicine, Hershey, Pennsylvania 17033, and
| | - Anna C Salzberg
- the Department of Biochemistry and Molecular Biology, Institute for Personalized Medicine, Penn State College of Medicine, Hershey, Pennsylvania 17033
| | - Scot R Kimball
- From the Department of Cellular and Molecular Physiology, Penn State College of Medicine, Hershey, Pennsylvania 17033
| | - Leonard S Jefferson
- From the Department of Cellular and Molecular Physiology, Penn State College of Medicine, Hershey, Pennsylvania 17033
| | - Michael D Dennis
- From the Department of Cellular and Molecular Physiology, Penn State College of Medicine, Hershey, Pennsylvania 17033,
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Coffey RT, Shi Y, Long MJC, Marr MT, Hedstrom L. Ubiquilin-mediated Small Molecule Inhibition of Mammalian Target of Rapamycin Complex 1 (mTORC1) Signaling. J Biol Chem 2016; 291:5221-33. [PMID: 26740621 DOI: 10.1074/jbc.m115.691584] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Indexed: 12/14/2022] Open
Abstract
Mammalian target of rapamycin complex 1 (mTORC1) is a master regulator of cellular metabolism, growth, and proliferation. mTORC1 has been implicated in many diseases such as cancer, diabetes, and neurodegeneration, and is a target to prolong lifespan. Here we report a small molecule inhibitor (Cbz-B3A) of mTORC1 signaling. Cbz-B3A inhibits the phosphorylation of eIF4E-binding protein 1 (4EBP1) and blocks 68% of translation. In contrast, rapamycin preferentially inhibits the phosphorylation of p70(S6k) and blocks 35% of translation. Cbz-B3A does not appear to bind directly to mTORC1, but instead binds to ubiquilins 1, 2, and 4. Knockdown of ubiquilin 2, but not ubiquilins 1 and 4, decreases the phosphorylation of 4EBP1, suggesting that ubiquilin 2 activates mTORC1. The knockdown of ubiquilins 2 and 4 decreases the effect of Cbz-B3A on 4EBP1 phosphorylation. Cbz-B3A slows cellular growth of some human leukemia cell lines, but is not cytotoxic. Thus Cbz-B3A exemplifies a novel strategy to inhibit mTORC1 signaling that might be exploited for treating many human diseases. We propose that Cbz-B3A reveals a previously unappreciated regulatory pathway coordinating cytosolic protein quality control and mTORC1 signaling.
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Affiliation(s)
- Rory T Coffey
- From the Graduate Program in Molecular and Cellular Biology, MS008
| | - Yuntao Shi
- the Graduate Program in Chemistry, MS015
| | | | - Michael T Marr
- the Department of Biology, MS009 and Rosenstiel Basic Medical Sciences Research Center, MS029, and
| | - Lizbeth Hedstrom
- the Department of Biology, MS009 and the Department of Chemistry, Brandeis University, Waltham, Massachusetts 02453-9110
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