International Journal of Molecular Sciences

Editorial

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5 pages, 218 KiB

Open AccessEditorial

GSK3 as a Master Regulator of Cellular Processes

by Ralf Lichtinghagen and René Huber

Int. J. Mol. Sci. 2023, 24(21), 15503; https://doi.org/10.3390/ijms242115503 - 24 Oct 2023

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Abstract

Since its initial purification and characterization as an enzyme negatively regulating glycogen synthase activity [...] Full article

(This article belongs to the Special Issue GSK3 as a Master Regulator of Cellular Processes)

Research

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18 pages, 2000 KiB

Open AccessArticle

GSK3α Regulates Temporally Dynamic Changes in Ribosomal Proteins upon Amino Acid Starvation in Cancer Cells

by Lorent Loxha, Nurul Khalida Ibrahim, Anna Sophie Stasche, Büsra Cinar, Tim Dolgner, Julia Niessen, Sabine Schreek, Beate Fehlhaber, Michael Forster, Martin Stanulla and Laura Hinze

Int. J. Mol. Sci. 2023, 24(17), 13260; https://doi.org/10.3390/ijms241713260 - 26 Aug 2023

Cited by 2 | Viewed by 1427

Abstract

Amino acid availability is crucial for cancer cells’ survivability. Leukemia and colorectal cancer cells have been shown to resist asparagine depletion by utilizing GSK3-dependent proteasomal degradation, termed the Wnt-dependent stabilization of proteins (Wnt/STOP), to replenish their amino acid pool. The inhibition of GSK3α [...] Read more.

Amino acid availability is crucial for cancer cells’ survivability. Leukemia and colorectal cancer cells have been shown to resist asparagine depletion by utilizing GSK3-dependent proteasomal degradation, termed the Wnt-dependent stabilization of proteins (Wnt/STOP), to replenish their amino acid pool. The inhibition of GSK3α halts the sourcing of amino acids, which subsequently leads to cancer cell vulnerability toward asparaginase therapy. However, resistance toward GSK3α-mediated protein breakdown can occur, whose underlying mechanism is poorly understood. Here, we set out to define the mechanisms driving dependence toward this degradation machinery upon asparagine starvation in cancer cells. We show the independence of known stress response pathways including the integrated stress response mediated with GCN2. Additionally, we demonstrate the independence of changes in cell cycle progression and expression levels of the asparagine-synthesizing enzyme ASNS. Instead, RNA sequencing revealed that GSK3α inhibition and asparagine starvation leads to the temporally dynamic downregulation of distinct ribosomal proteins, which have been shown to display anti-proliferative functions. Using a CRISPR/Cas9 viability screen, we demonstrate that the downregulation of these specific ribosomal proteins can rescue cell death upon GSK3α inhibition and asparagine starvation. Thus, our findings suggest the vital role of the previously unrecognized regulation of ribosomal proteins in bridging GSK3α activity and tolerance of asparagine starvation. Full article

(This article belongs to the Special Issue GSK3 as a Master Regulator of Cellular Processes)

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8 pages, 2278 KiB

Open AccessCommunication

GSK3β Inhibition Ameliorates Atherosclerotic Calcification

by Xinjiang Cai, Yan Zhao, Yang Yang, Xiuju Wu, Li Zhang, Jocelyn A. Ma, Jaden Ji, Kristina I. Boström and Yucheng Yao

Int. J. Mol. Sci. 2023, 24(14), 11638; https://doi.org/10.3390/ijms241411638 - 19 Jul 2023

Cited by 3 | Viewed by 1084

Abstract

Endothelial-mesenchymal transition (EndMT) drives endothelium to contribute to atherosclerotic calcification. In a previous study, we showed that glycogen synthase kinase-3β (GSK3β) inhibition induced β-catenin and reduced mothers against DPP homolog 1 (SMAD1) in order to redirect osteoblast-like cells towards endothelial lineage, thereby reducing [...] Read more.

Endothelial-mesenchymal transition (EndMT) drives endothelium to contribute to atherosclerotic calcification. In a previous study, we showed that glycogen synthase kinase-3β (GSK3β) inhibition induced β-catenin and reduced mothers against DPP homolog 1 (SMAD1) in order to redirect osteoblast-like cells towards endothelial lineage, thereby reducing vascular calcification in Matrix Gla Protein (Mgp) deficiency and diabetic Ins2^Akita/wt mice. Here, we report that GSK3β inhibition or endothelial-specific deletion of GSK3β reduces atherosclerotic calcification. We also find that alterations in β-catenin and SMAD1 induced by GSK3β inhibition in the aortas of Apoe^−/− mice are similar to Mgp^−/− mice. Together, our results suggest that GSK3β inhibition reduces vascular calcification in atherosclerotic lesions through a similar mechanism to that in Mgp^−/− mice. Full article

(This article belongs to the Special Issue GSK3 as a Master Regulator of Cellular Processes)

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17 pages, 2357 KiB

Open AccessArticle

GSK3β Inhibition by Phosphorylation at Ser³⁸⁹ Controls Neuroinflammation

by Belen Calvo, Miriam Fernandez, Mercedes Rincon and Pedro Tranque

Int. J. Mol. Sci. 2023, 24(1), 337; https://doi.org/10.3390/ijms24010337 - 25 Dec 2022

Cited by 4 | Viewed by 1760

Abstract

The inhibition of Glycogen Synthase Kinase 3 β (GSK3β) by Ser⁹ phosphorylation affects many physiological processes, including the immune response. However, the consequences of GSK3β inhibition by alternative Ser³⁸⁹ phosphorylation remain poorly characterized. Here we have examined neuroinflammation in GSK3β Ser [...] Read more.

The inhibition of Glycogen Synthase Kinase 3 β (GSK3β) by Ser⁹ phosphorylation affects many physiological processes, including the immune response. However, the consequences of GSK3β inhibition by alternative Ser³⁸⁹ phosphorylation remain poorly characterized. Here we have examined neuroinflammation in GSK3β Ser³⁸⁹ knock-in (KI) mice, in which the phosphorylation of Ser³⁸⁹ GSK3β is impaired. The number of activated microglia/infiltrated macrophages, astrocytes, and infiltrated neutrophils was significantly higher in these animals compared to C57BL/6J wild-type (WT) counterparts, which suggests that the failure to inactivate GSK3β by Ser³⁸⁹ phosphorylation results in sustained low-grade neuroinflammation. Moreover, glial cell activation and brain infiltration of immune cells in response to lipopolysaccharide (LPS) failed in GSK3β Ser³⁸⁹ KI mice. Such effects were brain-specific, as peripheral immunity was not similarly affected. Additionally, phosphorylation of the IkB kinase complex (IKK) in response to LPS failed in GSK3β Ser³⁸⁹ KI mice, while STAT3 phosphorylation was fully conserved, suggesting that the NF-κB signaling pathway is specifically affected by this GSK3β regulatory pathway. Overall, our findings indicate that GSK3β inactivation by Ser³⁸⁹ phosphorylation controls the brain inflammatory response, raising the need to evaluate its role in the progression of neuroinflammatory pathologies. Full article

(This article belongs to the Special Issue GSK3 as a Master Regulator of Cellular Processes)

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14 pages, 2432 KiB

Open AccessArticle

Glycogen Synthase Kinase 3β Is a Key Regulator in the Inhibitory Effects of Accumbal Cocaine- and Amphetamine-Regulated Transcript Peptide 55–102 on Amphetamine-Induced Locomotor Activity

by Bo Ram Cho, Wha Young Kim, Ju Kyong Jang, Jung Won Lee and Jeong-Hoon Kim

Int. J. Mol. Sci. 2022, 23(24), 15633; https://doi.org/10.3390/ijms232415633 - 9 Dec 2022

Cited by 1 | Viewed by 1366

Abstract

Microinjection of cocaine- and amphetamine-regulated transcript (CART) peptide 55–102 into the nucleus accumbens (NAcc) core significantly attenuates psychostimulant-induced locomotor activity. However, the molecular mechanism remains poorly understood. We examined the phosphorylation levels of Akt, glycogen synthase kinase 3β (GSK3β), and glutamate receptor 1 [...] Read more.

Microinjection of cocaine- and amphetamine-regulated transcript (CART) peptide 55–102 into the nucleus accumbens (NAcc) core significantly attenuates psychostimulant-induced locomotor activity. However, the molecular mechanism remains poorly understood. We examined the phosphorylation levels of Akt, glycogen synthase kinase 3β (GSK3β), and glutamate receptor 1 (GluA1) in NAcc core tissues obtained 60 min after microinjection of CART peptide 55–102 into this site, followed by systemic injection of amphetamine (AMPH). Phosphorylation levels of Akt at Thr308 and GSK3β at Ser9 were decreased, while those of GluA1 at Ser845 were increased, by AMPH treatment. These effects returned to basal levels following treatment with CART peptide 55–102. Furthermore, the negative regulatory effects of the CART peptide on AMPH-induced changes in phosphorylation levels and locomotor activity were all abolished by pretreatment with the S9 peptide, an artificially synthesized indirect GSK3β activator. These results suggest that the CART peptide 55–102 in the NAcc core plays a negative regulatory role in AMPH-induced locomotor activity by normalizing the changes in phosphorylation levels of Akt-GSK3β, and subsequently GluA1 modified by AMPH at this site. The present findings are the first to reveal GSK3β as a key regulator of the inhibitory role of the CART peptide in psychomotor stimulant-induced locomotor activity. Full article

(This article belongs to the Special Issue GSK3 as a Master Regulator of Cellular Processes)

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15 pages, 2373 KiB

Open AccessArticle

Investigating the Role of Endothelial Glycogen Synthase Kinase3α/β in Atherogenesis in Low Density Lipoprotein Receptor Knockout Mice

by Lauren Mastrogiacomo and Geoff H. Werstuck

Int. J. Mol. Sci. 2022, 23(23), 14780; https://doi.org/10.3390/ijms232314780 - 26 Nov 2022

Cited by 2 | Viewed by 1146

Abstract

Risk factors for developing cardiovascular disease (CVD) are associated with inflammation and endothelial activation. Activated endothelial cells (ECs) express adhesion proteins that recruit monocytes to the subendothelial layer initiating plaque development. Understanding the mechanism(s) by which ECs increase adhesion protein expression will facilitate [...] Read more.

Risk factors for developing cardiovascular disease (CVD) are associated with inflammation and endothelial activation. Activated endothelial cells (ECs) express adhesion proteins that recruit monocytes to the subendothelial layer initiating plaque development. Understanding the mechanism(s) by which ECs increase adhesion protein expression will facilitate the development of therapies aimed at preventing CVD progression and mortality. Glycogen synthase kinase (GSK)3α/β are constitutively active kinases which have been associated with many cellular pathways regulating cell viability and metabolism. While roles for myeloid GSK3α/β in the development of atherosclerosis have been established, there is limited knowledge on the potential roles of endothelial GSK3α/β. With the use of Cre recombinase technology, GSK3α/β was knocked out of both ECs and macrophages (Tie2Cre GSK3α/β^fl/fl LDLR^−/−). A bone marrow transplant was used to replenish GSK3α/β in the myeloid lineage allowing the assessment of an endothelial-selective GSK3α/β knockout (BMT Tie2Cre GSK3α/β^fl/fl LDLR^−/−). In both models, adhesion protein expression, macrophage recruitment and plaque volume were reduced in GSK3α knockout mice. GSK3β knockout had no significant effect. Results from this study are the first to suggest a pro-atherogenic role of endothelial GSK3α and support existing evidence for targeting GSK3α in the treatment of atherosclerotic CVD. Full article

(This article belongs to the Special Issue GSK3 as a Master Regulator of Cellular Processes)

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17 pages, 4348 KiB

Open AccessArticle

Aggregatibacter actinomycetemcomitans Cytolethal Distending Toxin-Induces Cell Cycle Arrest in a Glycogen Synthase Kinase (GSK)-3-Dependent Manner in Oral Keratinocytes

by Bruce J. Shenker, Lisa P. Walker, Ali Zekavat, Jonathon Korostoff and Kathleen Boesze-Battaglia

Int. J. Mol. Sci. 2022, 23(19), 11831; https://doi.org/10.3390/ijms231911831 - 5 Oct 2022

Cited by 3 | Viewed by 1510

Abstract

Cytolethal distending toxins (Cdt) are produced by a diverse group of pathogens. One Cdt-producing organism, Aggregatibacter actinomycetemcomitans, plays a critical role in the pathogenesis of a unique form of periodontitis, formerly referred to as localized aggressive periodontitis. The active Cdt subunit, CdtB, [...] Read more.

Cytolethal distending toxins (Cdt) are produced by a diverse group of pathogens. One Cdt-producing organism, Aggregatibacter actinomycetemcomitans, plays a critical role in the pathogenesis of a unique form of periodontitis, formerly referred to as localized aggressive periodontitis. The active Cdt subunit, CdtB, is a potent phosphatidylinositol (PI) 3,4,5-triphosphate phosphatase capable of inducing PI-3-kinase signaling blockade, a requisite for Cdt-induced toxicity in lymphocytes. In this study, we extended our observations to include the oral keratinocyte response to AaCdt using cell lines and primary gingival keratinocytes. All three exhibited G2/M arrest when exposed to AaCdt toxin within 24 h. Toxin-treated cells exhibited reduced levels of pAkt and pGSK3β within 6 h. Pre-treatment with GSK3β kinase inhibitors, LY2090314, CHIR99021 and Tideglusib, abrogated Cdt-induced G2/M arrest. None of the oral epithelial cells exhibited evidence of apoptosis. Cells remained arrested in the G2/M phase for at least 72 h without evidence of DNA damage response activation (H2AX phosphorylation). Cdt-treated cells displayed increased phosphorylation of the cyclin dependent kinase 1 (CDK1); moreover, the GSK3 inhibitors blocked this increase and reduced total CDK1 levels. This study further clarifies the potential mechanism(s) contributing to Cdt toxicity and toxin-mediated pathogenesis. Full article

(This article belongs to the Special Issue GSK3 as a Master Regulator of Cellular Processes)

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20 pages, 7632 KiB

Open AccessArticle

Silencing of Glycogen Synthase Kinase 3 Significantly Inhibits Chitin and Fatty Acid Metabolism in Asian Citrus Psyllid, Diaphorina citri

by Jin-Bo Zhang, Zhan-Jun Lu and Hai-Zhong Yu

Int. J. Mol. Sci. 2022, 23(17), 9654; https://doi.org/10.3390/ijms23179654 - 25 Aug 2022

Cited by 3 | Viewed by 1721

Abstract

Glycogen is a predominant carbohydrate reserve in various organisms, which provides energy for different life activities. Glycogen synthase kinase 3 (GSK3) is a central player that catalyzes glucose and converts it into glycogen. In this study, a GSK3 gene was identified from the [...] Read more.

Glycogen is a predominant carbohydrate reserve in various organisms, which provides energy for different life activities. Glycogen synthase kinase 3 (GSK3) is a central player that catalyzes glucose and converts it into glycogen. In this study, a GSK3 gene was identified from the D. citri genome database and named DcGSK3. A reverse transcription quantitative PCR (RT-qPCR) analysis showed that DcGSK3 was expressed at a high level in the head and egg. The silencing of DcGSK3 by RNA interference (RNAi) led to a loss-of-function phenotype. In addition, DcGSK3 knockdown decreased trehalase activity, glycogen, trehalose, glucose and free fatty acid content. Moreover, the expression levels of the genes associated with chitin and fatty acid synthesis were significantly downregulated after the silencing of DcGSK3. According to a comparative transcriptomics analysis, 991 differentially expressed genes (DEGs) were identified in dsDcGSK3 groups compared with dsGFP groups. A KEGG enrichment analysis suggested that these DEGs were primarily involved in carbon and fatty acid metabolism. The clustering analysis of DEGs further confirmed that chitin and fatty acid metabolism-related DEGs were upregulated at 24 h and were downregulated at 48 h. Our results suggest that DcGSK3 plays an important role in regulating the chitin and fatty acid metabolism of D. citri. Full article

(This article belongs to the Special Issue GSK3 as a Master Regulator of Cellular Processes)

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