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Siddika T, Shao R, Heinemann IU, O'Donoghue P. Delivery of AKT1 phospho-forms to human cells reveals differential substrate selectivity. IUBMB Life 2024. [PMID: 38738523 DOI: 10.1002/iub.2826] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2024] [Accepted: 03/25/2024] [Indexed: 05/14/2024]
Abstract
Protein kinase B (AKT1) is a serine/threonine kinase that regulates fundamental cellular processes, including cell survival, proliferation, and metabolism. AKT1 activity is controlled by two regulatory phosphorylation sites (Thr308, Ser473) that stimulate a downstream signaling cascade through phosphorylation of many target proteins. At either or both regulatory sites, hyperphosphorylation is associated with poor survival outcomes in many human cancers. Our previous biochemical and chemoproteomic studies showed that the phosphorylated forms of AKT1 have differential selectivity toward peptide substrates. Here, we investigated AKT1-dependent activity in human cells, using a cell-penetrating peptide (transactivator of transcription, TAT) to deliver inactive AKT1 or active phospho-variants to cells. We used enzyme engineering and genetic code expansion relying on a phosphoseryl-transfer RNA (tRNA) synthetase (SepRS) and tRNASep pair to produce TAT-tagged AKT1 with programmed phosphorylation at one or both key regulatory sites. We found that all TAT-tagged AKT1 variants were efficiently delivered into human embryonic kidney (HEK 293T) cells and that only the phosphorylated AKT1 (pAKT1) variants stimulated downstream signaling. All TAT-pAKT1 variants induced glycogen synthase kinase (GSK)-3α phosphorylation, as well as phosphorylation of ribosomal protein S6 at Ser240/244, demonstrating stimulation of downstream AKT1 signaling. Fascinatingly, only the AKT1 variants phosphorylated at S473 (TAT-pAKT1S473 or TAT-pAKT1T308,S473) were able to increase phospho-GSK-3β levels. Although each TAT-pAKT1 variant significantly stimulated cell proliferation, cells transduced with TAT-pAKT1T308 grew significantly faster than with the other pAKT1 variants. The data demonstrate differential activity of the AKT1 phospho-forms in modulating downstream signaling and proliferation in human cells.
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Affiliation(s)
- Tarana Siddika
- Department of Biochemistry, The University of Western Ontario, London, Ontario, Canada
| | - Richard Shao
- Department of Biochemistry, The University of Western Ontario, London, Ontario, Canada
| | - Ilka U Heinemann
- Department of Biochemistry, The University of Western Ontario, London, Ontario, Canada
| | - Patrick O'Donoghue
- Department of Biochemistry, The University of Western Ontario, London, Ontario, Canada
- Department of Chemistry, The University of Western Ontario, London, Ontario, Canada
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Dasgupta A, Urquidi Camacho RA, Enganti R, Cho SK, Tucker LL, Torreverde JS, Abraham PE, von Arnim AG. A phosphorylation-deficient ribosomal protein eS6 is largely functional in Arabidopsis thaliana, rescuing mutant defects from global translation and gene expression to photosynthesis and growth. PLANT DIRECT 2024; 8:e566. [PMID: 38250458 PMCID: PMC10799217 DOI: 10.1002/pld3.566] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Revised: 11/04/2023] [Accepted: 12/20/2023] [Indexed: 01/23/2024]
Abstract
The eukaryote-specific ribosomal protein of the small subunit eS6 is phosphorylated through the target of rapamycin (TOR) kinase pathway. Although this phosphorylation event responds dynamically to environmental conditions and has been studied for over 50 years, its biochemical and physiological significance remains controversial and poorly understood. Here, we report data from Arabidopsis thaliana, which indicate that plants expressing only a phospho-deficient isoform of eS6 grow essentially normally under laboratory conditions. The eS6z (RPS6A) paralog of eS6 functionally rescued a double mutant in both rps6a and rps6b genes when expressed at approximately twice the wild-type dosage. A mutant isoform of eS6z lacking the major six phosphorylatable serine and threonine residues in its carboxyl-terminal tail also rescued the lethality, rosette growth, and polyribosome loading of the double mutant. This isoform also complemented many mutant phenotypes of rps6 that were newly characterized here, including photosynthetic efficiency, and most of the gene expression defects that were measured by transcriptomics and proteomics. However, compared with plants rescued with a phospho-enabled version of eS6z, the phospho-deficient seedlings retained a mild pointed-leaf phenotype, root growth was reduced, and certain cell cycle-related mRNAs and ribosome biogenesis proteins were misexpressed. The residual defects of the phospho-deficient seedlings could be understood as an incomplete rescue of the rps6 mutant defects. There was little or no evidence for gain-of-function defects. As previously published, the phospho-deficient eS6z also rescued the rps6a and rps6b single mutants; however, phosphorylation of the eS6y (RPS6B) paralog remained lower than predicted, further underscoring that plants can tolerate phospho-deficiency of eS6 well. Our data also yield new insights into how plants cope with mutations in essential, duplicated ribosomal protein isoforms.
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Affiliation(s)
- Anwesha Dasgupta
- Department of Biochemistry & Cellular and Molecular BiologyThe University of TennesseeKnoxvilleTennesseeUSA
| | | | - Ramya Enganti
- Department of Biochemistry & Cellular and Molecular BiologyThe University of TennesseeKnoxvilleTennesseeUSA
| | - Sung Ki Cho
- Department of Biochemistry & Cellular and Molecular BiologyThe University of TennesseeKnoxvilleTennesseeUSA
| | - Lindsey L. Tucker
- Department of Biochemistry & Cellular and Molecular BiologyThe University of TennesseeKnoxvilleTennesseeUSA
| | - John S. Torreverde
- Department of Biochemistry & Cellular and Molecular BiologyThe University of TennesseeKnoxvilleTennesseeUSA
| | - Paul E. Abraham
- Graduate School of Genome Science and TechnologyThe University of TennesseeKnoxvilleTennesseeUSA
- Biosciences DivisionOak Ridge National LaboratoryOak RidgeTennesseeUSA
| | - Albrecht G. von Arnim
- Department of Biochemistry & Cellular and Molecular BiologyThe University of TennesseeKnoxvilleTennesseeUSA
- Graduate School of Genome Science and TechnologyThe University of TennesseeKnoxvilleTennesseeUSA
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3
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Comerford SA, Hinnant EA, Chen Y, Hammer RE. Hepatic ribosomal protein S6 (Rps6) insufficiency results in failed bile duct development and loss of hepatocyte viability; a ribosomopathy-like phenotype that is partially p53-dependent. PLoS Genet 2023; 19:e1010595. [PMID: 36656901 PMCID: PMC9888725 DOI: 10.1371/journal.pgen.1010595] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Revised: 01/31/2023] [Accepted: 12/26/2022] [Indexed: 01/20/2023] Open
Abstract
Defective ribosome biogenesis (RiBi) underlies a group of clinically diverse human diseases collectively known as the ribosomopathies, core manifestations of which include cytopenias and developmental abnormalities that are believed to stem primarily from an inability to synthesize adequate numbers of ribosomes and concomitant activation of p53. The importance of a correctly functioning RiBi machinery for maintaining tissue homeostasis is illustrated by the observation that, despite having a paucity of certain cell types in early life, ribosomopathy patients have an increased risk for developing cancer later in life. This suggests that hypoproliferative states trigger adaptive responses that can, over time, become maladaptive and inadvertently drive unchecked hyperproliferation and predispose to cancer. Here we describe an experimentally induced ribosomopathy in the mouse and show that a normal level of hepatic ribosomal protein S6 (Rps6) is required for proper bile duct development and preservation of hepatocyte viability and that its insufficiency later promotes overgrowth and predisposes to liver cancer which is accelerated in the absence of the tumor-suppressor PTEN. We also show that the overexpression of c-Myc in the liver ameliorates, while expression of a mutant hyperstable form of p53 partially recapitulates specific aspects of the hepatopathies induced by Rps6 deletion. Surprisingly, co-deletion of p53 in the Rps6-deficient background fails to restore biliary development or significantly improve hepatic function. This study not only reveals a previously unappreciated dependence of the developing liver on adequate levels of Rps6 and exquisitely controlled p53 signaling, but suggests that the increased cancer risk in ribosomopathy patients may, in part, stem from an inability to preserve normal tissue homeostasis in the face of chronic injury and regeneration.
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Affiliation(s)
- Sarah A. Comerford
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - Elizabeth A. Hinnant
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - Yidong Chen
- Department of Population Health Sciences, University of Texas Health San Antonio, San Antonio, Texas, United States of America
- Greehey Children’s Cancer Research Institute, University of Texas Health San Antonio, San Antonio, Texas. United States of America
| | - Robert E. Hammer
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
- * E-mail:
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4
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Tang Y, Luo J, Zhou Y, Zang H, Yang Y, Liu S, Zheng H, Ma J, Fan S, Wen Q. Overexpressed p-S6 associates with lymph node metastasis and predicts poor prognosis in non-small cell lung cancer. BMC Cancer 2022; 22:564. [PMID: 35596155 PMCID: PMC9123697 DOI: 10.1186/s12885-022-09664-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2021] [Accepted: 05/10/2022] [Indexed: 12/25/2022] Open
Abstract
Background Ribosomal protein S6 (S6), a downstream effect media of the AKT/mTOR pathway, not only is a part of 40S small subunit of eukaryotic ribosome, but also involves in protein synthesis and cell proliferation during cancer development. Methods In present study, we explore the association between phosphorylated S6 (p-S6) protein expression and clinicopathological features as well as prognostic implications in NSCLC. P-S6 was detected in tissue microarrays (TMAs) containing 350 NSCLC, 53 non-cancerous lung tissues (Non-CLT), and 88 cases of matched metastatic lymph node lesions via immunohistochemistry (IHC). Transwell assays and wound healing assay were used to assess the effects of p-S6 inhibition on NSCLC cell metastasis. Results The p-S6 expression in NSCLC was more evident than that in Non-CLT (p < 0.05). Compared to NSCLC patients who have no lymph node metastasis (LNM), those with LNM had higher p-S6 expression (p = 0.001). Regardless of lung squamous cell carcinoma (SCC) or adenocarcinoma (ADC), p-S6 was increased obviously in metastatic lymph nodes compared with matched primary cancers (p = 0.001, p = 0.022, respectively). Inhibition of p-S6 decreased the metastasis ability of NSCLC cells. In addition, p-S6 was an independent predicted marker for LNM in patients with NSCLC (p < 0.001). According to survival analysis, patients with highly expressed p-S6 had a lower survival rate compared with that with lower expression (p = 0.013). P-S6 is an unfavorable independent prognostic factor for NSCLC patients (p = 0.011). Conclusion Increased expression of p-S6 is not only a novel predictive biomarker of LNM but also poor prognosis in NSCLC. Supplementary Information The online version contains supplementary material available at 10.1186/s12885-022-09664-4.
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Affiliation(s)
- Yaoxiang Tang
- Department of Pathology, The Second Xiangya Hospital, Central South University, Changsha, 410011, Hunan, China
| | - Jiadi Luo
- Department of Pathology, The Second Xiangya Hospital, Central South University, Changsha, 410011, Hunan, China
| | - Ying Zhou
- Department of Pathology, The Second Xiangya Hospital, Central South University, Changsha, 410011, Hunan, China
| | - Hongjing Zang
- Department of Pathology, The Second Xiangya Hospital, Central South University, Changsha, 410011, Hunan, China
| | - Yang Yang
- Department of Pathology, The Second Xiangya Hospital, Central South University, Changsha, 410011, Hunan, China
| | - Sile Liu
- Department of Pathology, The Second Xiangya Hospital, Central South University, Changsha, 410011, Hunan, China
| | - Hongmei Zheng
- Department of Pathology, The Second Xiangya Hospital, Central South University, Changsha, 410011, Hunan, China
| | - Jian Ma
- Cancer Research Institute of Central South University, Hunan Key Laboratory of Nonresolving Inflammation and Cancer, Central South University, Changsha, 410011, Hunan, China
| | - Songqing Fan
- Department of Pathology, The Second Xiangya Hospital, Central South University, Changsha, 410011, Hunan, China
| | - Qiuyuan Wen
- Department of Pathology, The Second Xiangya Hospital, Central South University, Changsha, 410011, Hunan, China.
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Yi YW, You KS, Park JS, Lee SG, Seong YS. Ribosomal Protein S6: A Potential Therapeutic Target against Cancer? Int J Mol Sci 2021; 23:ijms23010048. [PMID: 35008473 PMCID: PMC8744729 DOI: 10.3390/ijms23010048] [Citation(s) in RCA: 38] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2021] [Revised: 12/19/2021] [Accepted: 12/20/2021] [Indexed: 12/12/2022] Open
Abstract
Ribosomal protein S6 (RPS6) is a component of the 40S small ribosomal subunit and participates in the control of mRNA translation. Additionally, phospho (p)-RPS6 has been recognized as a surrogate marker for the activated PI3K/AKT/mTORC1 pathway, which occurs in many cancer types. However, downstream mechanisms regulated by RPS6 or p-RPS remains elusive, and the therapeutic implication of RPS6 is underappreciated despite an approximately half a century history of research on this protein. In addition, substantial evidence from RPS6 knockdown experiments suggests the potential role of RPS6 in maintaining cancer cell proliferation. This motivates us to investigate the current knowledge of RPS6 functions in cancer. In this review article, we reviewed the current information about the transcriptional regulation, upstream regulators, and extra-ribosomal roles of RPS6, with a focus on its involvement in cancer. We also discussed the therapeutic potential of RPS6 in cancer.
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Affiliation(s)
- Yong Weon Yi
- Department of Biochemistry, College of Medicine, Dankook University, Cheonan 31116, Chungcheongnam-do, Korea; (Y.W.Y.); (K.S.Y.); (J.-S.P.)
- Department of Nanobiomedical Science, Dankook University, Cheonan 31116, Chungcheongnam-do, Korea
| | - Kyu Sic You
- Department of Biochemistry, College of Medicine, Dankook University, Cheonan 31116, Chungcheongnam-do, Korea; (Y.W.Y.); (K.S.Y.); (J.-S.P.)
- Graduate School of Convergence Medical Science, Dankook University, Cheonan 31116, Chungcheongnam-do, Korea
| | - Jeong-Soo Park
- Department of Biochemistry, College of Medicine, Dankook University, Cheonan 31116, Chungcheongnam-do, Korea; (Y.W.Y.); (K.S.Y.); (J.-S.P.)
| | - Seok-Geun Lee
- Graduate School, Kyung Hee University, Seoul 02447, Korea
- Correspondence: (S.-G.L.); (Y.-S.S.); Tel.: +82-2-961-2355 (S.-G.L.); +82-41-550-3875 (Y.-S.S.); Fax: +82-2-961-9623 (S.-G.L.)
| | - Yeon-Sun Seong
- Department of Biochemistry, College of Medicine, Dankook University, Cheonan 31116, Chungcheongnam-do, Korea; (Y.W.Y.); (K.S.Y.); (J.-S.P.)
- Graduate School of Convergence Medical Science, Dankook University, Cheonan 31116, Chungcheongnam-do, Korea
- Correspondence: (S.-G.L.); (Y.-S.S.); Tel.: +82-2-961-2355 (S.-G.L.); +82-41-550-3875 (Y.-S.S.); Fax: +82-2-961-9623 (S.-G.L.)
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6
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Serra-Navarro B, Fernandez-Ruiz R, García-Alamán A, Pradas-Juni M, Fernandez-Rebollo E, Esteban Y, Mir-Coll J, Mathieu J, Dalle S, Hahn M, Ahlgren U, Weinstein LS, Vidal J, Gomis R, Gasa R. Gsα-dependent signaling is required for postnatal establishment of a functional β-cell mass. Mol Metab 2021; 53:101264. [PMID: 34091063 PMCID: PMC8239471 DOI: 10.1016/j.molmet.2021.101264] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/18/2021] [Revised: 05/17/2021] [Accepted: 05/30/2021] [Indexed: 12/01/2022] Open
Abstract
OBJECTIVE Early postnatal life is a critical period for the establishment of the functional β-cell mass that will sustain whole-body glucose homeostasis during the lifetime. β cells are formed from progenitors during embryonic development but undergo significant expansion in quantity and attain functional maturity after birth. The signals and pathways involved in these processes are not fully elucidated. Cyclic adenosine monophosphate (cAMP) is an intracellular signaling molecule that is known to regulate insulin secretion, gene expression, proliferation, and survival of adult β cells. The heterotrimeric G protein Gs stimulates the cAMP-dependent pathway by activating adenylyl cyclase. In this study, we sought to explore the role of Gs-dependent signaling in postnatal β-cell development. METHODS To study Gs-dependent signaling, we generated conditional knockout mice in which the α subunit of the Gs protein (Gsα) was ablated from β-cells using the Cre deleter line Ins1Cre. Mice were characterized in terms of glucose homeostasis, including in vivo glucose tolerance, glucose-induced insulin secretion, and insulin sensitivity. β-cell mass was studied using histomorphometric analysis and optical projection tomography. β-cell proliferation was studied by ki67 and phospho-histone H3 immunostatining, and apoptosis was assessed by TUNEL assay. Gene expression was determined in isolated islets and sorted β cells by qPCR. Intracellular cAMP was studied in isolated islets using HTRF-based technology. The activation status of the cAMP and insulin-signaling pathways was determined by immunoblot analysis of the relevant components of these pathways in isolated islets. In vitro proliferation of dissociated islet cells was assessed by BrdU incorporation. RESULTS Elimination of Gsα in β cells led to reduced β-cell mass, deficient insulin secretion, and severe glucose intolerance. These defects were evident by weaning and were associated with decreased proliferation and inadequate expression of key β-cell identity and maturation genes in postnatal β-cells. Additionally, loss of Gsα caused a broad multilevel disruption of the insulin transduction pathway that resulted in the specific abrogation of the islet proliferative response to insulin. CONCLUSION We conclude that Gsα is required for β-cell growth and maturation in the early postnatal stage and propose that this is partly mediated via its crosstalk with insulin signaling. Our findings disclose a tight connection between these two pathways in postnatal β cells, which may have implications for using cAMP-raising agents to promote β-cell regeneration and maturation in diabetes.
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Affiliation(s)
- Berta Serra-Navarro
- Diabetes and Obesity Research Laboratory, August Pi i Sunyer Biomedical Research Institute (IDIBAPS), Rosselló 149-153, 08036, Barcelona, Spain; University of Barcelona, Barcelona, Spain
| | - Rebeca Fernandez-Ruiz
- Diabetes and Obesity Research Laboratory, August Pi i Sunyer Biomedical Research Institute (IDIBAPS), Rosselló 149-153, 08036, Barcelona, Spain; University of Barcelona, Barcelona, Spain; Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Spain
| | - Ainhoa García-Alamán
- Diabetes and Obesity Research Laboratory, August Pi i Sunyer Biomedical Research Institute (IDIBAPS), Rosselló 149-153, 08036, Barcelona, Spain; Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Spain
| | - Marta Pradas-Juni
- Diabetes and Obesity Research Laboratory, August Pi i Sunyer Biomedical Research Institute (IDIBAPS), Rosselló 149-153, 08036, Barcelona, Spain; University of Barcelona, Barcelona, Spain
| | - Eduardo Fernandez-Rebollo
- Diabetes and Obesity Research Laboratory, August Pi i Sunyer Biomedical Research Institute (IDIBAPS), Rosselló 149-153, 08036, Barcelona, Spain; Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Spain
| | - Yaiza Esteban
- Diabetes and Obesity Research Laboratory, August Pi i Sunyer Biomedical Research Institute (IDIBAPS), Rosselló 149-153, 08036, Barcelona, Spain; Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Spain
| | - Joan Mir-Coll
- Diabetes and Obesity Research Laboratory, August Pi i Sunyer Biomedical Research Institute (IDIBAPS), Rosselló 149-153, 08036, Barcelona, Spain; University of Barcelona, Barcelona, Spain
| | - Julia Mathieu
- CHU Montpellier, Laboratory of Cell Therapy for Diabetes (LTCD), Hospital St-Eloi, Montpellier, France
| | - Stephane Dalle
- CHU Montpellier, Laboratory of Cell Therapy for Diabetes (LTCD), Hospital St-Eloi, Montpellier, France
| | - Max Hahn
- Umeå Centre for Molecular Medicine (UCMM), Umeå, Sweden
| | - Ulf Ahlgren
- Umeå Centre for Molecular Medicine (UCMM), Umeå, Sweden
| | - Lee S Weinstein
- Metabolic Diseases Branch, National Institute of Diabetes, Digestive, and Kidney Diseases, NIH, Bethesda, MD, USA
| | - Josep Vidal
- Diabetes and Obesity Research Laboratory, August Pi i Sunyer Biomedical Research Institute (IDIBAPS), Rosselló 149-153, 08036, Barcelona, Spain; University of Barcelona, Barcelona, Spain; Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Spain; Department of Endocrinology and Nutrition, Hospital Clinic of Barcelona, Barcelona, Spain
| | - Ramon Gomis
- Diabetes and Obesity Research Laboratory, August Pi i Sunyer Biomedical Research Institute (IDIBAPS), Rosselló 149-153, 08036, Barcelona, Spain; University of Barcelona, Barcelona, Spain; Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Spain; Universitat Oberta de Catalunya (UOC), Barcelona, Spain
| | - Rosa Gasa
- Diabetes and Obesity Research Laboratory, August Pi i Sunyer Biomedical Research Institute (IDIBAPS), Rosselló 149-153, 08036, Barcelona, Spain; Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Spain.
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7
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Pungsrinont T, Kallenbach J, Baniahmad A. Role of PI3K-AKT-mTOR Pathway as a Pro-Survival Signaling and Resistance-Mediating Mechanism to Therapy of Prostate Cancer. Int J Mol Sci 2021; 22:11088. [PMID: 34681745 PMCID: PMC8538152 DOI: 10.3390/ijms222011088] [Citation(s) in RCA: 77] [Impact Index Per Article: 25.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Revised: 09/27/2021] [Accepted: 10/11/2021] [Indexed: 12/12/2022] Open
Abstract
Androgen deprivation therapy (ADT) and androgen receptor (AR)-targeted therapy are the gold standard options for treating prostate cancer (PCa). These are initially effective, as localized and the early stage of metastatic disease are androgen- and castration-sensitive. The tumor strongly relies on systemic/circulating androgens for activating AR signaling to stimulate growth and progression. However, after a certain point, the tumor will eventually develop a resistant stage, where ADT and AR antagonists are no longer effective. Mechanistically, it seems that the tumor becomes more aggressive through adaptive responses, relies more on alternative activated pathways, and is less dependent on AR signaling. This includes hyperactivation of PI3K-AKT-mTOR pathway, which is a central signal that regulates cell pro-survival/anti-apoptotic pathways, thus, compensating the blockade of AR signaling. The PI3K-AKT-mTOR pathway is well-documented for its crosstalk between genomic and non-genomic AR signaling, as well as other signaling cascades. Such a reciprocal feedback loop makes it more complicated to target individual factor/signaling for treating PCa. Here, we highlight the role of PI3K-AKT-mTOR signaling as a resistance mechanism for PCa therapy and illustrate the transition of prostate tumor from AR signaling-dependent to PI3K-AKT-mTOR pathway-dependent. Moreover, therapeutic strategies with inhibitors targeting the PI3K-AKT-mTOR signal used in clinic and ongoing clinical trials are discussed.
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Affiliation(s)
| | | | - Aria Baniahmad
- Institute of Human Genetics, Jena University Hospital, 07747 Jena, Germany; (T.P.); (J.K.)
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8
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Kokal M, Mirzakhani K, Pungsrinont T, Baniahmad A. Mechanisms of Androgen Receptor Agonist- and Antagonist-Mediated Cellular Senescence in Prostate Cancer. Cancers (Basel) 2020; 12:cancers12071833. [PMID: 32650419 PMCID: PMC7408918 DOI: 10.3390/cancers12071833] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Revised: 06/30/2020] [Accepted: 07/03/2020] [Indexed: 02/06/2023] Open
Abstract
The androgen receptor (AR) plays a leading role in the control of prostate cancer (PCa) growth. Interestingly, structurally different AR antagonists with distinct mechanisms of antagonism induce cell senescence, a mechanism that inhibits cell cycle progression, and thus seems to be a key cellular response for the treatment of PCa. Surprisingly, while physiological levels of androgens promote growth, supraphysiological androgen levels (SAL) inhibit PCa growth in an AR-dependent manner by inducing cell senescence in cancer cells. Thus, oppositional acting ligands, AR antagonists, and agonists are able to induce cellular senescence in PCa cells, as shown in cell culture model as well as ex vivo in patient tumor samples. This suggests a dual AR-signaling dependent on androgen levels that leads to the paradox of the rational to keep the AR constantly inactivated in order to treat PCa. These observations however opened the option to treat PCa patients with AR antagonists and/or with androgens at supraphysiological levels. The latter is currently used in clinical trials in so-called bipolar androgen therapy (BAT). Notably, cellular senescence is induced by AR antagonists or agonist in both androgen-dependent and castration-resistant PCa (CRPC). Pathway analysis suggests a crosstalk between AR and the non-receptor tyrosine kinase Src-Akt/PKB and the PI3K-mTOR-autophagy signaling in mediating AR-induced cellular senescence in PCa. In this review, we summarize the current knowledge of therapeutic induction and intracellular pathways of AR-mediated cellular senescence.
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Affiliation(s)
| | | | | | - Aria Baniahmad
- Correspondence: ; Tel.: +49-3641-9396820; Fax: +49-3641-99396822
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9
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Glennon EKK, Austin LS, Arang N, Kain HS, Mast FD, Vijayan K, Aitchison JD, Kappe SHI, Kaushansky A. Alterations in Phosphorylation of Hepatocyte Ribosomal Protein S6 Control Plasmodium Liver Stage Infection. Cell Rep 2020; 26:3391-3399.e4. [PMID: 30893610 DOI: 10.1016/j.celrep.2019.02.085] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Revised: 10/11/2018] [Accepted: 02/21/2019] [Indexed: 12/11/2022] Open
Abstract
Plasmodium parasites are highly selective when infecting hepatocytes and induce many changes within the host cell upon infection. While several host cell factors have been identified that are important for liver infection, our understanding of what facilitates the maintenance of infection remains incomplete. Here, we describe a role for phosphorylated ribosomal protein S6 (Ser235/236) (p-RPS6) in Plasmodium yoelii-infected hepatocytes. Blocking RPS6 phosphorylation prior to infection decreases the number of liver stage parasites within 24 h. Infected hepatocytes exhibit elevated levels of p-RPS6 while simultaneously abrogating the induction of phosphorylation of RPS6 in response to insulin stimulation. This is in contrast with the regulation of p-RPS6 by Toxoplasma gondii, which elevates levels of p-RPS6 after infection but does not alter the response to insulin. Our data support a model in which RPS6 phosphorylation is uncoupled from canonical regulators in Plasmodium-infected hepatocytes and is relied on by the parasite to maintain infection.
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Affiliation(s)
- Elizabeth K K Glennon
- Center for Infectious Disease Research, Seattle, WA 98109, USA; Seattle Children's Research Institute, Seattle, WA 98109, USA; Department of Global Health, University of Washington, Seattle, WA 98109, USA
| | - Laura S Austin
- Center for Infectious Disease Research, Seattle, WA 98109, USA
| | - Nadia Arang
- Center for Infectious Disease Research, Seattle, WA 98109, USA
| | - Heather S Kain
- Center for Infectious Disease Research, Seattle, WA 98109, USA
| | - Fred D Mast
- Center for Infectious Disease Research, Seattle, WA 98109, USA; Seattle Children's Research Institute, Seattle, WA 98109, USA; Institute for Systems Biology, Seattle, WA 98109, USA
| | - Kamalakannan Vijayan
- Center for Infectious Disease Research, Seattle, WA 98109, USA; Seattle Children's Research Institute, Seattle, WA 98109, USA
| | - John D Aitchison
- Center for Infectious Disease Research, Seattle, WA 98109, USA; Seattle Children's Research Institute, Seattle, WA 98109, USA; Institute for Systems Biology, Seattle, WA 98109, USA
| | - Stefan H I Kappe
- Center for Infectious Disease Research, Seattle, WA 98109, USA; Seattle Children's Research Institute, Seattle, WA 98109, USA; Department of Global Health, University of Washington, Seattle, WA 98109, USA
| | - Alexis Kaushansky
- Center for Infectious Disease Research, Seattle, WA 98109, USA; Seattle Children's Research Institute, Seattle, WA 98109, USA; Department of Global Health, University of Washington, Seattle, WA 98109, USA.
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Pungsrinont T, Sutter MF, Ertingshausen MCCM, Lakshmana G, Kokal M, Khan AS, Baniahmad A. Senolytic compounds control a distinct fate of androgen receptor agonist- and antagonist-induced cellular senescent LNCaP prostate cancer cells. Cell Biosci 2020; 10:59. [PMID: 32351687 PMCID: PMC7183592 DOI: 10.1186/s13578-020-00422-2] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Accepted: 04/17/2020] [Indexed: 12/11/2022] Open
Abstract
Background The benefit of inducing cellular senescence as a tumor suppressive strategy remains questionable due to the senescence-associated secretory phenotype. Hence, studies and development of senolytic compounds that induce cell death in senescent cells have recently emerged. Senescent cells are hypothesized to exhibit different upregulated pro-survival/anti-apoptotic networks depending on the senescent inducers. This might limit the effect of a particular senolytic compound that targets rather only a specific pathway. Interestingly, cellular senescence in prostate cancer (PCa) cells can be induced by either androgen receptor (AR) agonists at supraphysiological androgen level (SAL) used in bipolar androgen therapy or by AR antagonists. This challenges to define ligand-specific senolytic compounds. Results Here, we first induced cellular senescence by treating androgen-sensitive PCa LNCaP cells with either SAL or the AR antagonist Enzalutamide (ENZ). Subsequently, cells were incubated with the HSP90 inhibitor Ganetespib (GT), the Bcl-2 family inhibitor ABT263, or the Akt inhibitor MK2206 to analyze senolysis. GT and ABT263 are known senolytic compounds. We observed that GT exhibits senolytic activity specifically in SAL-pretreated PCa cells. Mechanistically, GT treatment results in reduction of AR, Akt, and phospho-S6 (p-S6) protein levels. Surprisingly, ABT263 lacks senolytic effect in both AR agonist- and antagonist-pretreated cells. ABT263 treatment does not affect AR, Akt, or S6 protein levels. Treatment with MK2206 does not reduce AR protein level and, as expected, potently inhibits Akt phosphorylation. However, ENZ-induced cellular senescent cells undergo apoptosis by MK2206, whereas SAL-treated cells are resistant. In line with this, we reveal that the pro-survival p-S6 level is higher in SAL-induced cellular senescent PCa cells compared to ENZ-treated cells. These data indicate a difference in the agonist- or antagonist-induced cellular senescence and suggest a novel role of MK2206 as a senolytic agent preferentially for AR antagonist-treated cells. Conclusion Taken together, our data suggest that both AR agonist and antagonist induce cellular senescence but differentially upregulate a pro-survival signaling which preferentially sensitize androgen-sensitive PCa LNCaP cells to a specific senolytic compound.
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Affiliation(s)
- Thanakorn Pungsrinont
- 1Institute of Human Genetics, Jena University Hospital, Am Klinikum 1, 07740 Jena, Germany
| | - Malika Franziska Sutter
- 1Institute of Human Genetics, Jena University Hospital, Am Klinikum 1, 07740 Jena, Germany.,2Department of Hematology and Medical Oncology, Jena University Hospital, Jena, Germany
| | | | - Gopinath Lakshmana
- 1Institute of Human Genetics, Jena University Hospital, Am Klinikum 1, 07740 Jena, Germany
| | - Miriam Kokal
- 1Institute of Human Genetics, Jena University Hospital, Am Klinikum 1, 07740 Jena, Germany
| | - Amir Saeed Khan
- 1Institute of Human Genetics, Jena University Hospital, Am Klinikum 1, 07740 Jena, Germany.,3Laboratory for Experimental Immunology of the Eye, Department of Ophthalmology, University Hospital Cologne, Cologne, Germany
| | - Aria Baniahmad
- 1Institute of Human Genetics, Jena University Hospital, Am Klinikum 1, 07740 Jena, Germany
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11
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Chatterjee N, Pazarentzos E, Mayekar MK, Gui P, Allegakoen DV, Hrustanovic G, Olivas V, Lin L, Verschueren E, Johnson JR, Hofree M, Yan JJ, Newton BW, Dollen JV, Earnshaw CH, Flanagan J, Chan E, Asthana S, Ideker T, Wu W, Suzuki J, Barad BA, Kirichok Y, Fraser JS, Weiss WA, Krogan NJ, Tulpule A, Sabnis AJ, Bivona TG. Synthetic Essentiality of Metabolic Regulator PDHK1 in PTEN-Deficient Cells and Cancers. Cell Rep 2019; 28:2317-2330.e8. [PMID: 31461649 PMCID: PMC6728083 DOI: 10.1016/j.celrep.2019.07.063] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Revised: 06/19/2019] [Accepted: 07/18/2019] [Indexed: 12/17/2022] Open
Abstract
Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) is a tumor suppressor and bi-functional lipid and protein phosphatase. We report that the metabolic regulator pyruvate dehydrogenase kinase1 (PDHK1) is a synthetic-essential gene in PTEN-deficient cancer and normal cells. The PTEN protein phosphatase dephosphorylates nuclear factor κB (NF-κB)-activating protein (NKAP) and limits NFκB activation to suppress expression of PDHK1, a NF-κB target gene. Loss of the PTEN protein phosphatase upregulates PDHK1 to induce aerobic glycolysis and PDHK1 cellular dependence. PTEN-deficient human tumors harbor increased PDHK1, a biomarker of decreased patient survival. This study uncovers a PTEN-regulated signaling pathway and reveals PDHK1 as a potential target in PTEN-deficient cancers.
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Affiliation(s)
- Nilanjana Chatterjee
- Department of Medicine, University of California, San Francisco, San Francisco, CA 94158, USA; Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA 94158, USA.
| | - Evangelos Pazarentzos
- Department of Medicine, University of California, San Francisco, San Francisco, CA 94158, USA; Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Manasi K Mayekar
- Department of Medicine, University of California, San Francisco, San Francisco, CA 94158, USA; Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Philippe Gui
- Department of Medicine, University of California, San Francisco, San Francisco, CA 94158, USA; Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA 94158, USA
| | - David V Allegakoen
- Department of Medicine, University of California, San Francisco, San Francisco, CA 94158, USA; Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Gorjan Hrustanovic
- Department of Medicine, University of California, San Francisco, San Francisco, CA 94158, USA; Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Victor Olivas
- Department of Medicine, University of California, San Francisco, San Francisco, CA 94158, USA; Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Luping Lin
- Department of Medicine, University of California, San Francisco, San Francisco, CA 94158, USA; Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Erik Verschueren
- J. David Gladstone Institutes, San Francisco, CA 94158, USA; Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158, USA; QB3, California Institute for Quantitative Biosciences, San Francisco, CA 94158, USA
| | - Jeffrey R Johnson
- J. David Gladstone Institutes, San Francisco, CA 94158, USA; Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158, USA; QB3, California Institute for Quantitative Biosciences, San Francisco, CA 94158, USA
| | - Matan Hofree
- Department of Bioengineering, University of California, San Diego, San Diego, CA 92093, USA
| | - Jenny J Yan
- Department of Medicine, University of California, San Francisco, San Francisco, CA 94158, USA; Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Billy W Newton
- J. David Gladstone Institutes, San Francisco, CA 94158, USA; Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158, USA; QB3, California Institute for Quantitative Biosciences, San Francisco, CA 94158, USA
| | - John V Dollen
- J. David Gladstone Institutes, San Francisco, CA 94158, USA; Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158, USA; QB3, California Institute for Quantitative Biosciences, San Francisco, CA 94158, USA
| | - Charles H Earnshaw
- Department of Medicine, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Jennifer Flanagan
- Department of Medicine, University of California, San Francisco, San Francisco, CA 94158, USA; Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Elton Chan
- Department of Medicine, University of California, San Francisco, San Francisco, CA 94158, USA; Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Saurabh Asthana
- Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Trey Ideker
- Department of Bioengineering, University of California, San Diego, San Diego, CA 92093, USA
| | - Wei Wu
- Department of Medicine, University of California, San Francisco, San Francisco, CA 94158, USA; Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Junji Suzuki
- Department of Physiology, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Benjamin A Barad
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Yuriy Kirichok
- Department of Physiology, University of California, San Francisco, San Francisco, CA 94158, USA
| | - James S Fraser
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, San Francisco, CA 94158, USA
| | - William A Weiss
- Department of Neurology, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Nevan J Krogan
- J. David Gladstone Institutes, San Francisco, CA 94158, USA; Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158, USA; QB3, California Institute for Quantitative Biosciences, San Francisco, CA 94158, USA
| | - Asmin Tulpule
- Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Amit J Sabnis
- Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Trever G Bivona
- Department of Medicine, University of California, San Francisco, San Francisco, CA 94158, USA; Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA 94158, USA; Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158, USA; QB3, California Institute for Quantitative Biosciences, San Francisco, CA 94158, USA.
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12
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Jaafar R, Tran S, Shah AN, Sun G, Valdearcos M, Marchetti P, Masini M, Swisa A, Giacometti S, Bernal-Mizrachi E, Matveyenko A, Hebrok M, Dor Y, Rutter GA, Koliwad SK, Bhushan A. mTORC1 to AMPK switching underlies β-cell metabolic plasticity during maturation and diabetes. J Clin Invest 2019; 129:4124-4137. [PMID: 31265435 PMCID: PMC6763225 DOI: 10.1172/jci127021] [Citation(s) in RCA: 78] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Accepted: 06/24/2019] [Indexed: 12/28/2022] Open
Abstract
Pancreatic beta cells (β-cells) differentiate during fetal life, but only postnatally acquire the capacity for glucose-stimulated insulin secretion (GSIS). How this happens is not clear. In exploring what molecular mechanisms drive the maturation of β-cell function, we found that the control of cellular signaling in β-cells fundamentally switched from the nutrient sensor target of rapamycin (mTORC1) to the energy sensor 5'-adenosine monophosphate-activated protein kinase (AMPK), and that this was critical for functional maturation. Moreover, AMPK was activated by the dietary transition taking place during weaning, and this in turn inhibited mTORC1 activity to drive the adult β-cell phenotype. While forcing constitutive mTORC1 signaling in adult β-cells relegated them to a functionally immature phenotype with characteristic transcriptional and metabolic profiles, engineering the switch from mTORC1 to AMPK signaling was sufficient to promote β-cell mitochondrial biogenesis, a shift to oxidative metabolism, and functional maturation. We also found that type 2 diabetes, a condition marked by both mitochondrial degeneration and dysregulated GSIS, was associated with a remarkable reversion of the normal AMPK-dependent adult β-cell signature to a more neonatal one characterized by mTORC1 activation. Manipulating the way in which cellular nutrient signaling pathways regulate β-cell metabolism may thus offer new targets to improve β-cell function in diabetes.
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Affiliation(s)
- Rami Jaafar
- The Diabetes Center, UCSF, San Francisco, California, USA
| | - Stella Tran
- The Diabetes Center, UCSF, San Francisco, California, USA
| | - Ajit N. Shah
- The Diabetes Center, UCSF, San Francisco, California, USA
| | - Gao Sun
- Section of Cell Biology and Functional Genomics, Department of Medicine, Imperial College London, Hammersmith Hospital London, United Kingdom
| | | | - Piero Marchetti
- Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy
| | - Matilde Masini
- Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy
| | - Avital Swisa
- Department of Developmental Biology and Cancer Research, Institute for Medical Research Israel-Canada, Hebrew University-Hadassah Medical School, Jerusalem, Israel
| | | | - Ernesto Bernal-Mizrachi
- Division of Endocrinology, Diabetes and Metabolism, University of Miami, Miller School of Medicine, Miami, Florida, USA
| | - Aleksey Matveyenko
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
| | | | - Yuval Dor
- Department of Developmental Biology and Cancer Research, Institute for Medical Research Israel-Canada, Hebrew University-Hadassah Medical School, Jerusalem, Israel
| | - Guy A. Rutter
- Section of Cell Biology and Functional Genomics, Department of Medicine, Imperial College London, Hammersmith Hospital London, United Kingdom
| | | | - Anil Bhushan
- The Diabetes Center, UCSF, San Francisco, California, USA
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13
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Proud CG. Phosphorylation and Signal Transduction Pathways in Translational Control. Cold Spring Harb Perspect Biol 2019; 11:cshperspect.a033050. [PMID: 29959191 DOI: 10.1101/cshperspect.a033050] [Citation(s) in RCA: 70] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Protein synthesis, including the translation of specific messenger RNAs (mRNAs), is regulated by extracellular stimuli such as hormones and by the levels of certain nutrients within cells. This control involves several well-understood signaling pathways and protein kinases, which regulate the phosphorylation of proteins that control the translational machinery. These pathways include the mechanistic target of rapamycin complex 1 (mTORC1), its downstream effectors, and the mitogen-activated protein (MAP) kinase (extracellular ligand-regulated kinase [ERK]) signaling pathway. This review describes the regulatory mechanisms that control translation initiation and elongation factors, in particular the effects of phosphorylation on their interactions or activities. It also discusses current knowledge concerning the impact of these control systems on the translation of specific mRNAs or subsets of mRNAs, both in physiological processes and in diseases such as cancer.
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Affiliation(s)
- Christopher G Proud
- Nutrition & Metabolism, South Australian Health & Medical Research Institute, North Terrace, Adelaide SA5000, Australia; and School of Biological Sciences, University of Adelaide, Adelaide SA5000, Australia
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14
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Novel AU-rich proximal UTR sequences (APS) enhance CXCL8 synthesis upon the induction of rpS6 phosphorylation. PLoS Genet 2019; 15:e1008077. [PMID: 30969964 PMCID: PMC6476525 DOI: 10.1371/journal.pgen.1008077] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2018] [Revised: 04/22/2019] [Accepted: 03/09/2019] [Indexed: 11/19/2022] Open
Abstract
The role of ribosomal protein S6 (rpS6) phosphorylation in mRNA translation remains poorly understood. Here, we reveal a potential role in modulating the translation rate of chemokine (C-X-C motif) ligand 8 (CXCL8 or Interleukin 8, IL8). We observed that more CXCL8 protein was being secreted from less CXCL8 mRNA in primary macrophages and macrophage-like HL-60 cells relative to other cell types. This correlated with an increase in CXCL8 polyribosome association, suggesting an increase in the rate of CXCL8 translation in macrophages. The cell type-specific expression levels were replicated by a CXCL8- UTR-reporter (Nanoluc reporter flanked by the 5' and 3' UTR of CXCL8). Mutations of the CXCL8-UTR-reporter revealed that cell type-specific expression required: 1) a 3' UTR of at least three hundred bases; and 2) an AU base content that exceeds fifty percent in the first hundred bases of the 3' UTR immediately after the stop codon, which we dub AU-rich proximal UTR sequences (APS). The 5' UTR of CXCL8 enhanced expression at the protein level and conferred cell type-specific expression when paired with a 3' UTR. A search for other APS-positive mRNAs uncovered TNF alpha induced protein 6 (TNFAIP6), another mRNA that was translationally upregulated in macrophages. The elevated translation of APS-positive mRNAs in macrophages coincided with elevated rpS6 S235/236 phosphorylation. Both were attenuated by the ERK1/2 signaling inhibitors, U0126 and AZD6244. In A549 cells, rpS6 S235/236 phosphorylation was induced by TAK1, Akt or PKA signaling. This enhanced the translation of the CXCL8-UTR-reporters. Thus, we propose that the induction of rpS6 S235/236 phosphorylation enhances the translation of mRNAs that contain APS motifs, such as CXCL8 and TNFAIP6. This may contribute to the role of macrophages as the primary producer of CXCL8, a cytokine that is essential for immune cell recruitment and activation.
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15
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Sironi J, Aranda E, Nordstrøm LU, Schwartz EL. Lysosome Membrane Permeabilization and Disruption of the Molecular Target of Rapamycin (mTOR)-Lysosome Interaction Are Associated with the Inhibition of Lung Cancer Cell Proliferation by a Chloroquinoline Analog. Mol Pharmacol 2018; 95:127-138. [PMID: 30409790 DOI: 10.1124/mol.118.113118] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Accepted: 10/31/2018] [Indexed: 01/07/2023] Open
Abstract
Lysosomes degrade cellular proteins and organelles and regulate cell signaling by providing a surface for the formation of critical protein complexes, notably molecular target of rapamycin (mTOR) complex 1 (mTORC1). Striking differences in the lysosomes of cancer versus normal cells suggest that they could be targets for drug development. Although the lysomotropic drugs chloroquine (CQ) and hydroxychloroquine (HCQ) have been widely investigated, studies have focused on their ability to inhibit autophagy. We synthesized a novel compound, called EAD1, which is structurally related to CQ but is a 14-fold more potent inhibitor of cell proliferation. Here we find that EAD1 causes rapid relocation, membrane permeabilization (LMP), and deacidification of lysosomes, and it induces apoptosis and irreversibly blocks proliferation of human lung cancer H460, H520, H1299, HCC827, and H1703 cells. EAD1 causes dissociation of mTOR from lysosomes and increases mTOR's perinuclear versus cytoplasmic localization, changes previously shown to inactivate mTORC1. The effect on mTOR was not seen with HCQ, even at >10-fold greater concentrations. Phosphorylation of a downstream target of mTORC1, ribosomal protein S6, was inhibited by EAD1. Although EAD1 also inhibited autophagy, it retained full antiproliferative activity in autophagy-deficient H1650 lung cancer cells, which have a biallelic deletion of Atg7, and in H460 Atg7-knockout cells. As Atg7 is critical for the canonical autophagy pathway, it is likely that inhibition of autophagy is not how EAD1 inhibits cell proliferation. Further studies are needed to determine the relationship of LMP to mTORC1 disruption and their relative contributions to drug-induced cell death. These studies support the lysosome as an underexplored target for new drug development.
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Affiliation(s)
- Juan Sironi
- Departments of Medicine (Oncology) (J.S., E.A., E.L.S.) and Biochemistry (L.U.N.), Albert Einstein College of Medicine and the Einstein Cancer Center, Bronx, New York
| | - Evelyn Aranda
- Departments of Medicine (Oncology) (J.S., E.A., E.L.S.) and Biochemistry (L.U.N.), Albert Einstein College of Medicine and the Einstein Cancer Center, Bronx, New York
| | - Lars Ulrik Nordstrøm
- Departments of Medicine (Oncology) (J.S., E.A., E.L.S.) and Biochemistry (L.U.N.), Albert Einstein College of Medicine and the Einstein Cancer Center, Bronx, New York
| | - Edward L Schwartz
- Departments of Medicine (Oncology) (J.S., E.A., E.L.S.) and Biochemistry (L.U.N.), Albert Einstein College of Medicine and the Einstein Cancer Center, Bronx, New York
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16
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Sun J, Mao L, Yang H, Ren D. Critical role for the Tsc1-mTORC1 pathway in β-cell mass in Pdx1-deficient mice. J Endocrinol 2018; 238:151-163. [PMID: 29875165 PMCID: PMC6030447 DOI: 10.1530/joe-18-0015] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Accepted: 06/05/2018] [Indexed: 01/25/2023]
Abstract
Mutations in the pancreatic duodenal homeobox (PDX1) gene are associated with diabetes in humans. Pdx1-haploinsufficient mice also develop diabetes, but the molecular mechanism is unknown. To this end, we knocked down Pdx1 gene expression in mouse MIN6 insulinoma cells. Pdx1 suppression not only increased apoptotic cell death but also decreased cell proliferation, which was associated with a decrease in activity of mechanistic target of rapamycin complex 1 (mTORC1). We found that in Pdx1-deficient mice, tuberous sclerosis 1 (Tsc1) ablation in pancreatic β-cells restores β-cell mass, increases β-cell proliferation and size, decreases the number of TUNEL-positive cells and restores glucose tolerance after glucose challenge. In addition, Tsc1 ablation in pancreatic β-cells increases phosphorylation of initiation factor 4E-binding protein 1 (4E-BP1) phosphorylation and 40S ribosomal protein S6, two downstream targets of mTORC1 indicating that Tsc1 mediates mTORC1 downregulation induced by Pdx1 suppression. These results suggest that the Tsc1-mTORC1 pathway plays an important role in mediating the decrease in β-cell proliferation and growth and the reduction in β-cell mass that occurs in Pdx1-deficient diabetes. Thus, mTORC1 may be target for therapeutic interventions in diabetes associated with reductions in β-cell mass.
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Affiliation(s)
- Juan Sun
- Department of MedicineThe University of Chicago, Chicago, Illinois, USA
| | - Liqun Mao
- Department of MedicineThe University of Chicago, Chicago, Illinois, USA
| | - Hongyan Yang
- Department of GynecologyKey Research Laboratory of Gynecology, Guangzhou University of Traditional Chinese Medicine, Guangzhou, Guangdong, China
| | - Decheng Ren
- Department of MedicineThe University of Chicago, Chicago, Illinois, USA
- Department of GynecologyKey Research Laboratory of Gynecology, Guangzhou University of Traditional Chinese Medicine, Guangzhou, Guangdong, China
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17
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Shirokikh NE, Preiss T. Translation initiation by cap-dependent ribosome recruitment: Recent insights and open questions. WILEY INTERDISCIPLINARY REVIEWS-RNA 2018; 9:e1473. [PMID: 29624880 DOI: 10.1002/wrna.1473] [Citation(s) in RCA: 91] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Revised: 02/02/2018] [Accepted: 02/14/2018] [Indexed: 12/14/2022]
Abstract
Gene expression universally relies on protein synthesis, where ribosomes recognize and decode the messenger RNA template by cycling through translation initiation, elongation, and termination phases. All aspects of translation have been studied for decades using the tools of biochemistry and molecular biology available at the time. Here, we focus on the mechanism of translation initiation in eukaryotes, which is remarkably more complex than prokaryotic initiation and is the target of multiple types of regulatory intervention. The "consensus" model, featuring cap-dependent ribosome entry and scanning of mRNA leader sequences, represents the predominantly utilized initiation pathway across eukaryotes, although several variations of the model and alternative initiation mechanisms are also known. Recent advances in structural biology techniques have enabled remarkable molecular-level insights into the functional states of eukaryotic ribosomes, including a range of ribosomal complexes with different combinations of translation initiation factors that are thought to represent bona fide intermediates of the initiation process. Similarly, high-throughput sequencing-based ribosome profiling or "footprinting" approaches have allowed much progress in understanding the elongation phase of translation, and variants of them are beginning to reveal the remaining mysteries of initiation, as well as aspects of translation termination and ribosomal recycling. A current view on the eukaryotic initiation mechanism is presented here with an emphasis on how recent structural and footprinting results underpin axioms of the consensus model. Along the way, we further outline some contested mechanistic issues and major open questions still to be addressed. This article is categorized under: Translation > Translation Mechanisms Translation > Translation Regulation RNA Interactions with Proteins and Other Molecules > Protein-RNA Interactions: Functional Implications.
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Affiliation(s)
- Nikolay E Shirokikh
- EMBL-Australia Collaborating Group, Department of Genome Sciences, The John Curtin School of Medical Research, The Australian National University, Canberra, Australia
- Victor Chang Cardiac Research Institute, Darlinghurst, Australia
| | - Thomas Preiss
- EMBL-Australia Collaborating Group, Department of Genome Sciences, The John Curtin School of Medical Research, The Australian National University, Canberra, Australia
- Victor Chang Cardiac Research Institute, Darlinghurst, Australia
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18
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Enganti R, Cho SK, Toperzer JD, Urquidi-Camacho RA, Cakir OS, Ray AP, Abraham PE, Hettich RL, von Arnim AG. Phosphorylation of Ribosomal Protein RPS6 Integrates Light Signals and Circadian Clock Signals. FRONTIERS IN PLANT SCIENCE 2017; 8:2210. [PMID: 29403507 PMCID: PMC5780430 DOI: 10.3389/fpls.2017.02210] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2017] [Accepted: 12/15/2017] [Indexed: 05/20/2023]
Abstract
The translation of mRNA into protein is tightly regulated by the light environment as well as by the circadian clock. Although changes in translational efficiency have been well documented at the level of mRNA-ribosome loading, the underlying mechanisms are unclear. The reversible phosphorylation of RIBOSOMAL PROTEIN OF THE SMALL SUBUNIT 6 (RPS6) has been known for 40 years, but the biochemical significance of this event remains unclear to this day. Here, we confirm using a clock-deficient strain of Arabidopsis thaliana that RPS6 phosphorylation (RPS6-P) is controlled by the diel light-dark cycle with a peak during the day. Strikingly, when wild-type, clock-enabled, seedlings that have been entrained to a light-dark cycle are placed under free-running conditions, the circadian clock drives a cycle of RPS6-P with an opposite phase, peaking during the subjective night. We show that in wild-type seedlings under a light-dark cycle, the incoherent light and clock signals are integrated by the plant to cause an oscillation in RPS6-P with a reduced amplitude with a peak during the day. Sucrose can stimulate RPS6-P, as seen when sucrose in the medium masks the light response of etiolated seedlings. However, the diel cycles of RPS6-P are observed in the presence of 1% sucrose and in its absence. Sucrose at a high concentration of 3% appears to interfere with the robust integration of light and clock signals at the level of RPS6-P. Finally, we addressed whether RPS6-P occurs uniformly in polysomes, non-polysomal ribosomes and their subunits, and non-ribosomal protein. It is the polysomal RPS6 whose phosphorylation is most highly stimulated by light and repressed by darkness. These data exemplify a striking case of contrasting biochemical regulation between clock signals and light signals. Although the physiological significance of RPS6-P remains unknown, our data provide a mechanistic basis for the future understanding of this enigmatic event.
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Affiliation(s)
- Ramya Enganti
- Department of Biochemistry, Cellular and Molecular Biology, The University of Tennessee, Knoxville, TN, United States
| | - Sung Ki Cho
- Department of Biochemistry, Cellular and Molecular Biology, The University of Tennessee, Knoxville, TN, United States
| | - Jody D. Toperzer
- Department of Biochemistry, Cellular and Molecular Biology, The University of Tennessee, Knoxville, TN, United States
| | - Ricardo A. Urquidi-Camacho
- Graduate School of Genome Science and Technology, The University of Tennessee, Knoxville, TN, United States
| | - Ozkan S. Cakir
- Department of Biochemistry, Cellular and Molecular Biology, The University of Tennessee, Knoxville, TN, United States
| | - Alexandria P. Ray
- Department of Biochemistry, Cellular and Molecular Biology, The University of Tennessee, Knoxville, TN, United States
| | - Paul E. Abraham
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, United States
| | - Robert L. Hettich
- Graduate School of Genome Science and Technology, The University of Tennessee, Knoxville, TN, United States
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, United States
| | - Albrecht G. von Arnim
- Department of Biochemistry, Cellular and Molecular Biology, The University of Tennessee, Knoxville, TN, United States
- Graduate School of Genome Science and Technology, The University of Tennessee, Knoxville, TN, United States
- *Correspondence: Albrecht G. von Arnim,
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Correction: Phosphorylated Ribosomal Protein S6 Is Required for Akt-Driven Hyperplasia and Malignant Transformation, but Not for Hypertrophy, Aneuploidy and Hyperfunction of Pancreatic β-Cells. PLoS One 2016; 11:e0155281. [PMID: 27145125 PMCID: PMC4856372 DOI: 10.1371/journal.pone.0155281] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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