1
|
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.
Collapse
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.
| |
Collapse
|
2
|
Kip AM, Valverde JM, Altelaar M, Heeren RMA, Hundscheid IHR, Dejong CHC, Olde Damink SWM, Balluff B, Lenaerts K. Combined Quantitative (Phospho)proteomics and Mass Spectrometry Imaging Reveal Temporal and Spatial Protein Changes in Human Intestinal Ischemia-Reperfusion. J Proteome Res 2021; 21:49-66. [PMID: 34874173 PMCID: PMC8750167 DOI: 10.1021/acs.jproteome.1c00447] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
![]()
Intestinal ischemia–reperfusion
(IR) injury is a severe
clinical condition, and unraveling its pathophysiology is crucial
to improve therapeutic strategies and reduce the high morbidity and
mortality rates. Here, we studied the dynamic proteome and phosphoproteome
in the human intestine during ischemia and reperfusion, using liquid
chromatography-tandem mass spectrometry (LC-MS/MS) analysis to gain
quantitative information of thousands of proteins and phosphorylation
sites, as well as mass spectrometry imaging (MSI) to obtain spatial
information. We identified a significant decrease in abundance of
proteins related to intestinal absorption, microvillus, and cell junction,
whereas proteins involved in innate immunity, in particular the complement
cascade, and extracellular matrix organization increased in abundance
after IR. Differentially phosphorylated proteins were involved in
RNA splicing events and cytoskeletal and cell junction organization.
In addition, our analysis points to mitogen-activated protein kinase
(MAPK) and cyclin-dependent kinase (CDK) families to be active kinases
during IR. Finally, matrix-assisted laser desorption ionization time-of-flight
(MALDI-TOF) MSI presented peptide alterations in abundance and distribution,
which resulted, in combination with Fourier-transform ion cyclotron
resonance (FTICR) MSI and LC-MS/MS, in the annotation of proteins
related to RNA splicing, the complement cascade, and extracellular
matrix organization. This study expanded our understanding of the
molecular changes that occur during IR in the human intestine and
highlights the value of the complementary use of different MS-based
methodologies.
Collapse
Affiliation(s)
- Anna M Kip
- Department of Surgery, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University, P.O. Box 616, 6200 MD Maastricht, The Netherlands
| | - Juan Manuel Valverde
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Padualaan 8, Utrecht 3584 CH, The Netherlands
| | - Maarten Altelaar
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Padualaan 8, Utrecht 3584 CH, The Netherlands
| | - Ron M A Heeren
- Maastricht Multimodal Molecular Imaging Institute (M4i), Maastricht University, 6200 MD Maastricht, The Netherlands
| | - Inca H R Hundscheid
- Department of Surgery, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University, P.O. Box 616, 6200 MD Maastricht, The Netherlands
| | - Cornelis H C Dejong
- Department of Surgery, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University, P.O. Box 616, 6200 MD Maastricht, The Netherlands.,Department of General, Visceral- and Transplantation Surgery, RWTH Aachen University Hospital, Pauwelsstraße 30, 52074 Aachen, Germany
| | - Steven W M Olde Damink
- Department of Surgery, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University, P.O. Box 616, 6200 MD Maastricht, The Netherlands.,Department of General, Visceral- and Transplantation Surgery, RWTH Aachen University Hospital, Pauwelsstraße 30, 52074 Aachen, Germany
| | - Benjamin Balluff
- Maastricht Multimodal Molecular Imaging Institute (M4i), Maastricht University, 6200 MD Maastricht, The Netherlands
| | - Kaatje Lenaerts
- Department of Surgery, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University, P.O. Box 616, 6200 MD Maastricht, The Netherlands
| |
Collapse
|
3
|
Enhanced phosphorylation of S6 protein in mouse cortical layer V and subplate neurons. Neuroreport 2021; 31:762-769. [PMID: 32453020 DOI: 10.1097/wnr.0000000000001479] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The mammalian neocortex is composed of six major layers of neurons. Each group of neurons in the cortical layers has distinct characteristics based on the expression of specific genes and connectivity patterns of neural circuits. Neuronal subtype transition and regional identity acquisition are established by temporal cues and interaction between several transcription factors during neurogenesis. The impairment of cortical lamination or neural circuits results in a wide range of neurodevelopmental disorders such as autism, schizophrenia, and certain forms of childhood epilepsy. Despite continuous efforts to classify neurons with the aid of genetic and epigenetic analyses, the neuron-specific properties associated with post-transcriptional modification remain unclear. In the present study, the distribution of phosphorylated S6-positive layers across the neocortex was examined using several layer markers. The development of pS6 S235/236 layers in layer V and the subplate was spatiotemporally regulated in the mouse brain. In addition, enhanced phosphorylation of ribosomal protein S6 in Ctip2-positive layer V neurons in vivo was sustained under in-vitro conditions using a culture of primary cortical neurons.
Collapse
|
4
|
Smith EM, Benbahouche N, Morris K, Wilczynska A, Gillen S, Schmidt T, Meijer H, Jukes-Jones R, Cain K, Jones C, Stoneley M, Waldron J, Bell C, Fonseca B, Blagden S, Willis A, Bushell M. The mTOR regulated RNA-binding protein LARP1 requires PABPC1 for guided mRNA interaction. Nucleic Acids Res 2021; 49:458-478. [PMID: 33332560 PMCID: PMC7797073 DOI: 10.1093/nar/gkaa1189] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Revised: 11/16/2020] [Accepted: 12/11/2020] [Indexed: 12/16/2022] Open
Abstract
The mammalian target of rapamycin (mTOR) is a critical regulator of cell growth, integrating multiple signalling cues and pathways. Key among the downstream activities of mTOR is the control of the protein synthesis machinery. This is achieved, in part, via the co-ordinated regulation of mRNAs that contain a terminal oligopyrimidine tract (TOP) at their 5'ends, although the mechanisms by which this occurs downstream of mTOR signalling are still unclear. We used RNA-binding protein (RBP) capture to identify changes in the protein-RNA interaction landscape following mTOR inhibition. Upon mTOR inhibition, the binding of LARP1 to a number of mRNAs, including TOP-containing mRNAs, increased. Importantly, non-TOP-containing mRNAs bound by LARP1 are in a translationally-repressed state, even under control conditions. The mRNA interactome of the LARP1-associated protein PABPC1 was found to have a high degree of overlap with that of LARP1 and our data show that PABPC1 is required for the association of LARP1 with its specific mRNA targets. Finally, we demonstrate that mRNAs, including those encoding proteins critical for cell growth and survival, are translationally repressed when bound by both LARP1 and PABPC1.
Collapse
Affiliation(s)
- Ewan M Smith
- Cancer Research UK Beatson Institute, Garscube Estate, Switchback Road, Bearsden, Glasgow G61 1BD, UK
| | - Nour El Houda Benbahouche
- Cancer Research UK Beatson Institute, Garscube Estate, Switchback Road, Bearsden, Glasgow G61 1BD, UK
| | - Katherine Morris
- MRC Toxicology Unit, University of Cambridge, Leicester LE1 9HN, UK
| | - Ania Wilczynska
- Cancer Research UK Beatson Institute, Garscube Estate, Switchback Road, Bearsden, Glasgow G61 1BD, UK
- Institute of Cancer Sciences, University of Glasgow, Garscube Estate, Switchback Road, Bearsden, Glasgow G61 1QH, UK
| | - Sarah Gillen
- Cancer Research UK Beatson Institute, Garscube Estate, Switchback Road, Bearsden, Glasgow G61 1BD, UK
| | - Tobias Schmidt
- Cancer Research UK Beatson Institute, Garscube Estate, Switchback Road, Bearsden, Glasgow G61 1BD, UK
| | - Hedda A Meijer
- Division of Cell and Developmental Biology, School of Life Sciences, University of Dundee, Dundee DD1 5EH, UK
| | | | - Kelvin Cain
- MRC Toxicology Unit, University of Cambridge, Leicester LE1 9HN, UK
| | - Carolyn Jones
- MRC Toxicology Unit, University of Cambridge, Leicester LE1 9HN, UK
| | - Mark Stoneley
- MRC Toxicology Unit, University of Cambridge, Leicester LE1 9HN, UK
| | - Joseph A Waldron
- Cancer Research UK Beatson Institute, Garscube Estate, Switchback Road, Bearsden, Glasgow G61 1BD, UK
| | - Cameron Bell
- Cancer Research UK Therapeutic Discovery Laboratories, London Bioscience Innovation Centre, 2 Royal College Street, London NW1 0NH, UK
| | | | - Sarah Blagden
- Department of Oncology, University of Oxford, Oxford, OX3 7LE, UK
| | - Anne E Willis
- MRC Toxicology Unit, University of Cambridge, Leicester LE1 9HN, UK
| | - Martin Bushell
- Cancer Research UK Beatson Institute, Garscube Estate, Switchback Road, Bearsden, Glasgow G61 1BD, UK
- Institute of Cancer Sciences, University of Glasgow, Garscube Estate, Switchback Road, Bearsden, Glasgow G61 1QH, UK
| |
Collapse
|
5
|
Pszczolkowski VL, Zhang J, Pignato KA, Meyer EJ, Kurth MM, Lin A, Arriola Apelo SI. Insulin potentiates essential amino acids effects on mechanistic target of rapamycin complex 1 signaling in MAC-T cells. J Dairy Sci 2020; 103:11988-12002. [PMID: 33222863 DOI: 10.3168/jds.2020-18920] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Accepted: 08/06/2020] [Indexed: 01/05/2023]
Abstract
Different models of lactation offer conflicting evidence as to whether insulin signaling is required for AA to stimulate mechanistic target of rapamycin complex 1 (mTORC1) activity. We hypothesized that insulin potentiates essential AA stimulation of mTORC1 activity in the MAC-T mammary epithelial cell line. Here, our objective was to assess mTORC1 signaling activity in response to insulin and individual or grouped essential AA. Insulin and essential AA concentrations in the treatment medium ranged from normo- to supraphysiological, with insulin at 0, 1, 10, or 100 nmol/L and essential AA at approximately 0, 0.01, 0.05, 0.1, 1, or 3× reference plasma levels. Effects and interaction of insulin and total essential AA were tested in a 3 × 5 factorial design (n = 3 replicates/treatment); insulin and the individual AA Leu, Met, Ile, and Arg were likewise tested in 3 × 4 factorials (n = 4). As the remaining individual AA His, Lys, Phe, Thr, Trp, and Val were expected to not affect mTORC1, these were tested only at the highest insulin level, 100 nmol/L (n = 4). For all of these, linear and quadratic effects of total and individual AA were evaluated. Essential AA were subsequently grouped by their positive (Leu, Met, Ile, Arg, and Thr; TOR-AA) or absent-to-negative effects (His, Lys, Phe, Trp, and Val; NTOR-AA), and tested for interaction in a 2 × 2 factorial design (n = 4), with each AA at its respective 1× plasma level, and insulin held at 100 nmol/L. All experiments consisted of 1 h treatment incubation, followed by Western blotting of cell lysates to measure phosphorylation and abundance of the mTORC1 pathway proteins Akt (Ser473); ribosomal protein S6 kinase p70 (S6K1, Thr389); eukaryotic translation initiation factor 4E-binding protein 1 (4E-BP1, Ser65); and ribosomal protein S6 (S6, Ser240/244). The Akt phosphorylation was overall increased by insulin, with a possible negative interaction with both total essential AA and the individual AA Leu. Total essential AA also increased S6K1 and 4E-BP1 phosphorylation in an insulin-dependent manner. The individual AA Leu, Met, Ile, and Arg increased S6K1 phosphorylation in an insulin-dependent manner. Similarly, Met and Arg increased 4E-BP1 phosphorylation in an insulin-dependent manner. Histidine, Lys, Trp, and Val did not affect S6K1 phosphorylation. However, S6K1 phosphorylation was linearly increased by Thr and quadratically decreased by Phe. Relative to the phosphorylation of S6K1 when cells were incubated with no essential AA, the NTOR-AA group had no effect, whereas the TOR-AA increased phosphorylation to the same degree observed with all 10 essential AA. Overall, we have found that insulin is required for essential AA to stimulate mTORC1 activity in MAC-T cells. In addition, the AA responsible for the bulk of mTORC1 activation in MAC-T are limited to Leu, Met, Ile, Arg, and Thr.
Collapse
Affiliation(s)
- Virginia L Pszczolkowski
- Department of Animal and Dairy Sciences, University of Wisconsin-Madison, 53706; Endocrinology and Reproductive Physiology Graduate Training Program, University of Wisconsin-Madison, 53706
| | - Jun Zhang
- Department of Animal and Dairy Sciences, University of Wisconsin-Madison, 53706; State Key Laboratory of Animal Nutrition, College of Animal Science and Technology, China Agricultural University, Beijing, China 100083
| | - Kayleigh A Pignato
- Department of Animal and Dairy Sciences, University of Wisconsin-Madison, 53706
| | - Emma J Meyer
- Department of Animal and Dairy Sciences, University of Wisconsin-Madison, 53706
| | - Madison M Kurth
- Department of Animal and Dairy Sciences, University of Wisconsin-Madison, 53706
| | - Amy Lin
- Department of Animal and Dairy Sciences, University of Wisconsin-Madison, 53706
| | - Sebastian I Arriola Apelo
- Department of Animal and Dairy Sciences, University of Wisconsin-Madison, 53706; Endocrinology and Reproductive Physiology Graduate Training Program, University of Wisconsin-Madison, 53706.
| |
Collapse
|
6
|
Abstract
The emergence of genome-wide analyses to interrogate cellular DNA, RNA, and protein content has revolutionized the study of control networks that mediate cellular homeostasis. mRNA translation represents the last step of genetic flow and primarily defines the proteome. Translational regulation is thus critical for gene expression, in particular under nutrient excess or deficiency. Until recently, it was unclear how the global effects of translational control are orchestrated by nutrient signaling pathways. An emerging concept of translational reprogramming addresses how to maintain the expression of specific proteins during nutrient stress by translation of selective mRNAs. In this review, we describe recent advances in our understanding of translational control principles; nutrient-sensing mechanisms; and their dysregulation in human diseases such as diabetes, cancer, and aging. The mechanistic understanding of translational regulation in response to different nutrient conditions may help identify potential dietary and therapeutic targets to improve human health.
Collapse
Affiliation(s)
- Xin Erica Shu
- Division of Nutritional Sciences, Cornell University, Ithaca, New York 14853, USA
| | - Robert V. Swanda
- Graduate Field of Biomedical and Biological Sciences, Cornell University, Ithaca, New York 14853, USA
| | - Shu-Bing Qian
- Division of Nutritional Sciences, Cornell University, Ithaca, New York 14853, USA
- Graduate Field of Biomedical and Biological Sciences, Cornell University, Ithaca, New York 14853, USA
| |
Collapse
|
7
|
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.
Collapse
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.
| |
Collapse
|
8
|
TOR and RPS6 transmit light signals to enhance protein translation in deetiolating Arabidopsis seedlings. Proc Natl Acad Sci U S A 2018; 115:12823-12828. [PMID: 30482859 PMCID: PMC6294885 DOI: 10.1073/pnas.1809526115] [Citation(s) in RCA: 66] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Light enhances the translation efficiency of thousands of mRNAs during photomorphogenic development in Arabidopsis, but the underlying molecular mechanism remains elusive. Here we show that light activates the auxin-target of rapamycin (TOR)-ribosome protein S6 (RPS6) pathway to enhance translation in deetiolating Arabidopsis. We discovered that CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1) represses TOR activity in dark-grown seedlings. The perception of far-red and blue light by photoreceptors inactivates COP1, which leads to the derepression of the auxin-TOR-RPS6 pathway and enhanced de novo protein synthesis. Our study revealed a light-triggered signaling pathway for translational regulation. This sophisticated regulation also functions to ensure that young seedlings have strict skotomorphogenic development in the dark and a timely switch to photomorphogenic development. Deetiolation is an essential developmental process transforming young plant seedlings into the vegetative phase with photosynthetic activities. Light signals initiate this important developmental process by triggering massive reprogramming of the transcriptome and translatome. Compared with the wealth of knowledge of transcriptional regulation, the molecular mechanism underlying this light-triggered translational enhancement remains unclear. Here we show that light-enhanced translation is orchestrated by a light perception and signaling pathway composed of photoreceptors, CONSTITUTIVE PHOTOMORPHOGENESIS 1 (COP1), the phytohormone auxin, target of rapamycin (TOR), and ribosomal protein S6 (RPS6). In deetiolating Arabidopsis seedlings, photoreceptors, including phytochrome A and cryptochromes, perceive far-red and blue light to inactivate the negative regulator COP1, which leads to activation of the auxin pathway for TOR-dependent phosphorylation of RPS6. Arabidopsis mutants defective in TOR, RPS6A, or RPS6B exhibited delayed cotyledon opening, a characteristic of the deetiolating process to ensure timely vegetative development of a young seedling. This study provides a mechanistic view of light-triggered translational enhancement in deetiolating Arabidopsis.
Collapse
|
9
|
Grundy M, Jones T, Elmi L, Hall M, Graham A, Russell N, Pallis M. Early changes in rpS6 phosphorylation and BH3 profiling predict response to chemotherapy in AML cells. PLoS One 2018; 13:e0196805. [PMID: 29723246 PMCID: PMC5933738 DOI: 10.1371/journal.pone.0196805] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Accepted: 04/19/2018] [Indexed: 11/19/2022] Open
Abstract
Blasts from different patients with acute myeloid leukemia (AML) vary in the agent(s) to which they are most responsive. With a myriad of novel agents to evaluate, there is a lack of predictive biomarkers to precisely assign targeted therapies to individual patients. Primary AML cells often survive poorly in vitro, thus confounding conventional cytotoxicity assays. The purpose of this work was to assess the potential of two same-day functional predictive assays in AML cell lines to predict long-term response to chemotherapy. (i) Ribosomal protein S6 (rpS6) is a downstream substrate of PI3K/akt/mTOR/ kinase and MAPK kinase pathways and its dephosphorylation is also triggered by DNA double strand breaks. Phospho-rpS6 is reliably measurable by flow cytometry and thus has the potential to function as a biomarker of responsiveness to several therapeutic agents. (ii) A cell's propensity for apoptosis can be interrogated via a functional assay termed "Dynamic BH3 Profiling" in which mitochondrial outer membrane permeabilization in drug-treated cells can be driven by pro-apoptotic BH3 domain peptides such as PUMA-BH3. The extent to which a particular cell is primed for apoptosis by the drug can be determined by measuring the amount of cytochrome C released on addition of BH3 peptide. We demonstrate that phospho-rpS6 expression and PUMA-BH3 peptide-induced cytochrome C release after 4 hours both predict long term chemoresponsiveness to tyrosine kinase inhibitors and DNA double strand break inducers in AML cell lines. We also describe changes in expression levels of the prosurvival BCL-2 family member Mcl-1 and the pro-apoptotic protein BIM after short term drug culture.
Collapse
Affiliation(s)
- Martin Grundy
- Clinical Haematology, Nottingham University Hospitals, Nottingham, United Kingdom
- * E-mail:
| | - Thomas Jones
- Department of Haematology, Division of Cancer and Stem Cells, University of Nottingham, Nottingham, United Kingdom
| | - Liban Elmi
- Department of Haematology, Division of Cancer and Stem Cells, University of Nottingham, Nottingham, United Kingdom
| | - Michael Hall
- Department of Haematology, Division of Cancer and Stem Cells, University of Nottingham, Nottingham, United Kingdom
| | - Adam Graham
- Department of Haematology, Division of Cancer and Stem Cells, University of Nottingham, Nottingham, United Kingdom
| | - Nigel Russell
- Clinical Haematology, Nottingham University Hospitals, Nottingham, United Kingdom
- Department of Haematology, Division of Cancer and Stem Cells, University of Nottingham, Nottingham, United Kingdom
| | - Monica Pallis
- Clinical Haematology, Nottingham University Hospitals, Nottingham, United Kingdom
| |
Collapse
|
10
|
Puighermanal E, Biever A, Pascoli V, Melser S, Pratlong M, Cutando L, Rialle S, Severac D, Boubaker-Vitre J, Meyuhas O, Marsicano G, Lüscher C, Valjent E. Ribosomal Protein S6 Phosphorylation Is Involved in Novelty-Induced Locomotion, Synaptic Plasticity and mRNA Translation. Front Mol Neurosci 2017; 10:419. [PMID: 29311811 PMCID: PMC5742586 DOI: 10.3389/fnmol.2017.00419] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Accepted: 12/01/2017] [Indexed: 11/29/2022] Open
Abstract
The phosphorylation of the ribosomal protein S6 (rpS6) is widely used to track neuronal activity. Although it is generally assumed that rpS6 phosphorylation has a stimulatory effect on global protein synthesis in neurons, its exact biological function remains unknown. By using a phospho-deficient rpS6 knockin mouse model, we directly tested the role of phospho-rpS6 in mRNA translation, plasticity and behavior. The analysis of multiple brain areas shows for the first time that, in neurons, phospho-rpS6 is dispensable for overall protein synthesis. Instead, we found that phospho-rpS6 controls the translation of a subset of mRNAs in a specific brain region, the nucleus accumbens (Acb), but not in the dorsal striatum. We further show that rpS6 phospho-mutant mice display altered long-term potentiation (LTP) in the Acb and enhanced novelty-induced locomotion. Collectively, our findings suggest a previously unappreciated role of phospho-rpS6 in the physiology of the Acb, through the translation of a selective subclass of mRNAs, rather than the regulation of general protein synthesis.
Collapse
Affiliation(s)
| | - Anne Biever
- IGF, CNRS, INSERM, University of Montpellier, Montpellier, France
| | - Vincent Pascoli
- Department of Basic Neurosciences, Medical Faculty, University of Geneva, Geneva, Switzerland
| | - Su Melser
- INSERM U1215, Université de Bordeaux, NeuroCentre Magendie, Bordeaux, France
| | - Marine Pratlong
- Montpellier GenomiX, BioCampus Montpellier, CNRS, INSERM, University of Montpellier, Montpellier, France
| | - Laura Cutando
- IGF, CNRS, INSERM, University of Montpellier, Montpellier, France
| | - Stephanie Rialle
- Montpellier GenomiX, BioCampus Montpellier, CNRS, INSERM, University of Montpellier, Montpellier, France
| | - Dany Severac
- Montpellier GenomiX, BioCampus Montpellier, CNRS, INSERM, University of Montpellier, Montpellier, France
| | | | - Oded Meyuhas
- Department of Biochemistry and Molecular Biology, IMRIC, The Hebrew University-Hadassah Medical School, Jerusalem, Israel
| | - Giovanni Marsicano
- INSERM U1215, Université de Bordeaux, NeuroCentre Magendie, Bordeaux, France
| | - Christian Lüscher
- Department of Basic Neurosciences, Medical Faculty, University of Geneva, Geneva, Switzerland.,Clinic of Neurology, Department of Clinical Neurosciences, Geneva University Hospital, Geneva, Switzerland
| | - Emmanuel Valjent
- IGF, CNRS, INSERM, University of Montpellier, Montpellier, France
| |
Collapse
|
11
|
Esnault S, Shen ZJ, Malter JS. Protein Translation and Signaling in Human Eosinophils. Front Med (Lausanne) 2017; 4:150. [PMID: 28971096 PMCID: PMC5609579 DOI: 10.3389/fmed.2017.00150] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2017] [Accepted: 09/01/2017] [Indexed: 01/01/2023] Open
Abstract
We have recently reported that, unlike IL-5 and GM-CSF, IL-3 induces increased translation of a subset of mRNAs. In addition, we have demonstrated that Pin1 controls the activity of mRNA binding proteins, leading to enhanced mRNA stability, GM-CSF protein production and prolonged eosinophil (EOS) survival. In this review, discussion will include an overview of cap-dependent protein translation and its regulation by intracellular signaling pathways. We will address the more general process of mRNA post-transcriptional regulation, especially regarding mRNA binding proteins, which are critical effectors of protein translation. Furthermore, we will focus on (1) the roles of IL-3-driven sustained signaling on enhanced protein translation in EOS, (2) the mechanisms regulating mRNA binding proteins activity in EOS, and (3) the potential targeting of IL-3 signaling and the signaling leading to mRNA binding activity changes to identify therapeutic targets to treat EOS-associated diseases.
Collapse
Affiliation(s)
- Stephane Esnault
- Department of Medicine, Allergy, Pulmonary, and Critical Care Medicine Division, University of Wisconsin-Madison School of Medicine and Public Health, Madison, WI, United States
| | - Zhong-Jian Shen
- Department of Pathology, University of Texas Southwestern Medical Center, Dallas, TX, United States
| | - James S Malter
- Department of Pathology, University of Texas Southwestern Medical Center, Dallas, TX, United States
| |
Collapse
|
12
|
de Vicente JC, Peña I, Rodrigo JP, Rodríguez-Santamarta T, Lequerica-Fernández P, Suárez-Fernández L, Allonca E, García-Pedrero JM. Phosphorylated ribosomal protein S6 correlation with p21 expression and inverse association with tumor size in oral squamous cell carcinoma. Head Neck 2017; 39:1876-1887. [PMID: 28675642 DOI: 10.1002/hed.24854] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2016] [Revised: 03/01/2017] [Accepted: 05/01/2017] [Indexed: 12/23/2022] Open
Abstract
BACKGROUND The purpose of this study was to investigate the clinical relevance of phosphorylated ribosomal protein S6 (p-S6), a surrogate marker of mammalian target of rapamycin (mTOR) activation, and p21 in a series of 125 patients with oral squamous cell carcinomas (OSCCs). METHODS Immunohistochemical analysis was performed to ascertain the phosphorylation status of p-S6 at Ser235/236 and Ser240/244, p21, and p53 protein expression. RESULTS Expression of phosphorylated S6 protein on either serine 235/236 or serine 240/244 was detected in 83% and 88% tumors, respectively, and both of them were inversely and significantly correlated with the tumor size and local infiltration. Positive p21 expression was found in 91.5% of the cases, and was inversely correlated with tumor size. In OSCC, p21 expression correlates with p-S6 levels, a surrogate marker of mTOR activation, independently of p53 status. CONCLUSION Expression of both p21 and p-S6 was found to inversely associate with tumor size but not survival outcomes in patients with OSCC.
Collapse
Affiliation(s)
- Juan C de Vicente
- Department of Oral and Maxillofacial Surgery, Hospital Universitario Central de Asturias (HUCA), Oviedo, Asturias, Spain.,Instituto Universitario de Oncología del Principado de Asturias (IUOPA), Hospital Universitario Central de Asturias, Oviedo, Asturias, CIBERONC ISCIII Spain
| | - Ignacio Peña
- Department of Oral and Maxillofacial Surgery, Hospital Universitario Central de Asturias (HUCA), Oviedo, Asturias, Spain
| | - Juan P Rodrigo
- Department of Otolaryngology, Hospital Universitario Central de Asturias (HUCA), Oviedo, Asturias, Spain.,Instituto Universitario de Oncología del Principado de Asturias (IUOPA), Hospital Universitario Central de Asturias, Oviedo, Asturias, CIBERONC ISCIII Spain
| | - Tania Rodríguez-Santamarta
- Department of Oral and Maxillofacial Surgery, Hospital Universitario Central de Asturias (HUCA), Oviedo, Asturias, Spain
| | | | - Laura Suárez-Fernández
- Department of Otolaryngology, Hospital Universitario Central de Asturias (HUCA), Oviedo, Asturias, Spain
| | - Eva Allonca
- Department of Otolaryngology, Hospital Universitario Central de Asturias (HUCA), Oviedo, Asturias, Spain
| | - Juana M García-Pedrero
- Department of Otolaryngology, Hospital Universitario Central de Asturias (HUCA), Oviedo, Asturias, Spain.,Instituto Universitario de Oncología del Principado de Asturias (IUOPA), Hospital Universitario Central de Asturias, Oviedo, Asturias, CIBERONC ISCIII Spain
| |
Collapse
|
13
|
Cargnello M, Tcherkezian J, Roux PP. The expanding role of mTOR in cancer cell growth and proliferation. Mutagenesis 2015; 30:169-76. [PMID: 25688110 DOI: 10.1093/mutage/geu045] [Citation(s) in RCA: 117] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The mechanistic/mammalian target of rapamycin (mTOR) is a conserved protein kinase that controls several anabolic processes required for cell growth and proliferation. As such, mTOR has been implicated in an increasing number of pathological conditions, including cancer, obesity, type 2 diabetes and neurodegeneration. As part of the mTOR complex 1 (mTORC1), mTOR regulates cell growth by promoting the biosynthesis of proteins, lipids and nucleic acids. Several mTORC1 substrates have been shown to regulate protein synthesis, including the eukaryotic initiation factor 4E (eIF4E)-binding proteins (4E-BPs) and the ribosomal S6 kinases (S6Ks) 1 and 2. In this work, we focus on the signalling pathways that lie both upstream and downstream of mTORC1, as well as their relevance to human pathologies. We further discuss pharmacological approaches that target mTOR and their applications for the treatment of cancer.
Collapse
Affiliation(s)
- Marie Cargnello
- Institute for Research in Immunology and Cancer (IRIC), Université de Montréal, Montréal, Québec, Canada
| | - Joseph Tcherkezian
- Laboratory for Therapeutic Development, McGill University, Montréal, Québec, Canada and
| | - Philippe P Roux
- Institute for Research in Immunology and Cancer (IRIC), Université de Montréal, Montréal, Québec, Canada, Department of Pathology and Cell Biology, Faculty of Medicine, Université de Montréal, Montréal, Québec, Canada
| |
Collapse
|
14
|
Biever A, Valjent E, Puighermanal E. Ribosomal Protein S6 Phosphorylation in the Nervous System: From Regulation to Function. Front Mol Neurosci 2015; 8:75. [PMID: 26733799 PMCID: PMC4679984 DOI: 10.3389/fnmol.2015.00075] [Citation(s) in RCA: 139] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Accepted: 11/23/2015] [Indexed: 01/31/2023] Open
Abstract
Since the discovery of the phosphorylation of the 40S ribosomal protein S6 (rpS6) about four decades ago, much effort has been made to uncover the molecular mechanisms underlying the regulation of this post-translational modification. In the field of neuroscience, rpS6 phosphorylation is commonly used as a readout of the mammalian target of rapamycin complex 1 signaling activation or as a marker for neuronal activity. Nevertheless, its biological role in neurons still remains puzzling. Here we review the pharmacological and physiological stimuli regulating this modification in the nervous system as well as the pathways that transduce these signals into rpS6 phosphorylation. Altered rpS6 phosphorylation observed in various genetic and pathophysiological mouse models is also discussed. Finally, we examine the current state of knowledge on the physiological role of this post-translational modification and highlight the questions that remain to be addressed.
Collapse
Affiliation(s)
- Anne Biever
- Centre National de la Recherche Scientifique, UMR5203, Institut de Génomique FonctionnelleMontpellier, France; Institut National de la Santé et de la Recherche Médicale, U1191Montpellier, France; Université de Montpellier, UMR-5203Montpellier, France
| | - Emmanuel Valjent
- Centre National de la Recherche Scientifique, UMR5203, Institut de Génomique FonctionnelleMontpellier, France; Institut National de la Santé et de la Recherche Médicale, U1191Montpellier, France; Université de Montpellier, UMR-5203Montpellier, France
| | - Emma Puighermanal
- Centre National de la Recherche Scientifique, UMR5203, Institut de Génomique FonctionnelleMontpellier, France; Institut National de la Santé et de la Recherche Médicale, U1191Montpellier, France; Université de Montpellier, UMR-5203Montpellier, France
| |
Collapse
|
15
|
Chang HH, Young SH, Sinnett-Smith J, Chou CEN, Moro A, Hertzer KM, Hines OJ, Rozengurt E, Eibl G. Prostaglandin E2 activates the mTORC1 pathway through an EP4/cAMP/PKA- and EP1/Ca2+-mediated mechanism in the human pancreatic carcinoma cell line PANC-1. Am J Physiol Cell Physiol 2015; 309:C639-49. [PMID: 26310818 DOI: 10.1152/ajpcell.00417.2014] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2014] [Accepted: 08/14/2015] [Indexed: 02/07/2023]
Abstract
Obesity, a known risk factor for pancreatic cancer, is associated with inflammation and insulin resistance. Proinflammatory prostaglandin E2 (PGE2) and elevated insulin-like growth factor type 1 (IGF-1), related to insulin resistance, are shown to play critical roles in pancreatic cancer progression. We aimed to explore a potential cross talk between PGE2 signaling and the IGF-1/Akt/mammalian target of rapamycin complex 1 (mTORC1) pathway in pancreatic cancer, which may be a key to unraveling the obesity-cancer link. In PANC-1 human pancreatic cancer cells, we showed that PGE2 stimulated mTORC1 activity independently of Akt, as evaluated by downstream signaling events. Subsequently, using pharmacological and genetic approaches, we demonstrated that PGE2-induced mTORC1 activation is mediated by the EP4/cAMP/PKA pathway, as well as an EP1/Ca(2+)-dependent pathway. The cooperative roles of the two pathways were supported by the maximal inhibition achieved with the combined pharmacological blockade, and the coexistence of highly expressed EP1 (mediating the Ca(2+) response) and EP2 or EP4 (mediating the cAMP/PKA pathway) in PANC-1 cells and in the prostate cancer line PC-3, which also robustly exhibited PGE2-induced mTORC1 activation, as identified from a screen in various cancer cell lines. Importantly, we showed a reinforcing interaction between PGE2 and IGF-1 on mTORC1 signaling, with an increase in IL-23 production as a cellular outcome. Our data reveal a previously unrecognized mechanism of PGE2-stimulated mTORC1 activation mediated by EP4/cAMP/PKA and EP1/Ca(2+) signaling, which may be of great importance in elucidating the promoting effects of obesity in pancreatic cancer. Ultimately, a precise understanding of these molecular links may provide novel targets for efficacious interventions devoid of adverse effects.
Collapse
Affiliation(s)
- Hui-Hua Chang
- Department of Surgery, David Geffen School of Medicine at UCLA, Los Angeles, California; and
| | - Steven H Young
- Department of Medicine, David Geffen School of Medicine at UCLA, Los Angeles, California
| | - James Sinnett-Smith
- Department of Medicine, David Geffen School of Medicine at UCLA, Los Angeles, California
| | - Caroline Ei Ne Chou
- Department of Surgery, David Geffen School of Medicine at UCLA, Los Angeles, California; and
| | - Aune Moro
- Department of Surgery, David Geffen School of Medicine at UCLA, Los Angeles, California; and
| | - Kathleen M Hertzer
- Department of Surgery, David Geffen School of Medicine at UCLA, Los Angeles, California; and
| | - Oscar Joe Hines
- Department of Surgery, David Geffen School of Medicine at UCLA, Los Angeles, California; and
| | - Enrique Rozengurt
- Department of Medicine, David Geffen School of Medicine at UCLA, Los Angeles, California
| | - Guido Eibl
- Department of Surgery, David Geffen School of Medicine at UCLA, Los Angeles, California; and
| |
Collapse
|
16
|
Esnault S, Kelly EAB, Shen ZJ, Johansson MW, Malter JS, Jarjour NN. IL-3 Maintains Activation of the p90S6K/RPS6 Pathway and Increases Translation in Human Eosinophils. THE JOURNAL OF IMMUNOLOGY 2015; 195:2529-39. [PMID: 26276876 DOI: 10.4049/jimmunol.1500871] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 04/14/2015] [Accepted: 07/15/2015] [Indexed: 12/12/2022]
Abstract
IL-5 is a major therapeutic target to reduce eosinophilia. However, all of the eosinophil-activating cytokines, such as IL-5, IL-3, and GM-CSF, are typically present in atopic diseases, including allergic asthma. As a result of the functional redundancy of these three cytokines on eosinophils and the loss of IL-5R on airway eosinophils, it is important to take IL-3 and GM-CSF into account to efficiently reduce tissue eosinophil functions. Moreover, these three cytokines signal through a common β-chain receptor but yet differentially affect protein production in eosinophils. Notably, the increased ability of IL-3 to induce the production of proteins, such as semaphorin-7A, without affecting mRNA levels suggests a unique influence of IL-3 on translation. The purpose of this study was to identify the mechanisms by which IL-3 distinctively affects eosinophil function compared with IL-5 and GM-CSF, with a focus on protein translation. Peripheral blood eosinophils were used to study intracellular signaling and protein translation in cells activated with IL-3, GM-CSF, or IL-5. We establish that, unlike GM-CSF or IL-5, IL-3 triggers prolonged signaling through activation of ribosomal protein S6 (RPS6) and the upstream kinase 90-kDa ribosomal S6 kinase (p90S6K). Blockade of p90S6K activation inhibited phosphorylation of RPS6 and IL-3-enhanced semaphorin-7A translation. Furthermore, in an allergen-challenged environment, in vivo phosphorylation of RPS6 and p90S6K was enhanced in human airway compared with circulating eosinophils. Our findings provide new insights into the mechanisms underlying differential activation of eosinophils by IL-3, GM-CSF, and IL-5. These observations identify IL-3 and its downstream intracellular signals as novel targets that should be considered to modulate eosinophil functions.
Collapse
Affiliation(s)
- Stephane Esnault
- Division of Allergy, Pulmonary, and Critical Care Medicine, Department of Medicine, University of Wisconsin School of Medicine and Public Health, Madison, WI 53792;
| | - Elizabeth A B Kelly
- Division of Allergy, Pulmonary, and Critical Care Medicine, Department of Medicine, University of Wisconsin School of Medicine and Public Health, Madison, WI 53792
| | - Zhong-Jian Shen
- Department of Pathology, University of Texas Southwestern Medical Center, Dallas, TX 75390; and
| | - Mats W Johansson
- Department of Biomolecular Chemistry, University of Wisconsin School of Medicine and Public Health, Madison, WI 53792
| | - James S Malter
- Department of Pathology, University of Texas Southwestern Medical Center, Dallas, TX 75390; and
| | - Nizar N Jarjour
- Division of Allergy, Pulmonary, and Critical Care Medicine, Department of Medicine, University of Wisconsin School of Medicine and Public Health, Madison, WI 53792
| |
Collapse
|
17
|
Ribosomal Protein S6 Phosphorylation: Four Decades of Research. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2015; 320:41-73. [PMID: 26614871 DOI: 10.1016/bs.ircmb.2015.07.006] [Citation(s) in RCA: 182] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The phosphorylation of ribosomal protein S6 (rpS6) has been described for the first time about four decades ago. Since then, numerous studies have shown that this modification occurs in response to a wide variety of stimuli on five evolutionarily conserved serine residues. However, despite a large body of information on the respective kinases and the signal transduction pathways, the physiological role of rpS6 phosphorylation remained obscure until genetic manipulations were applied in both yeast and mammals in an attempt to block this modification. Thus, studies based on both mice and cultured cells subjected to disruption of the genes encoding rpS6 and the respective kinases, as well as the substitution of the phosphorylatable serine residues in rpS6, have laid the ground for the elucidation of the multiple roles of this protein and its posttranslational modification. This review focuses primarily on newly identified kinases that phosphorylate rpS6, pathways that transduce various signals into rpS6 phosphorylation, and the recently established physiological functions of this modification. It should be noted, however, that despite the significant progress made in the last decade, the molecular mechanism(s) underlying the diverse effects of rpS6 phosphorylation on cellular and organismal physiology are still poorly understood.
Collapse
|
18
|
Ming M, Sinnett-Smith J, Wang J, Soares HP, Young SH, Eibl G, Rozengurt E. Dose-Dependent AMPK-Dependent and Independent Mechanisms of Berberine and Metformin Inhibition of mTORC1, ERK, DNA Synthesis and Proliferation in Pancreatic Cancer Cells. PLoS One 2014; 9:e114573. [PMID: 25493642 PMCID: PMC4262417 DOI: 10.1371/journal.pone.0114573] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Accepted: 11/11/2014] [Indexed: 12/13/2022] Open
Abstract
Natural products represent a rich reservoir of potential small chemical molecules exhibiting anti-proliferative and chemopreventive properties. Here, we show that treatment of pancreatic ductal adenocarcinoma (PDAC) cells (PANC-1, MiaPaCa-2) with the isoquinoline alkaloid berberine (0.3-6 µM) inhibited DNA synthesis and proliferation of these cells and delay the progression of their cell cycle in G1. Berberine treatment also reduced (by 70%) the growth of MiaPaCa-2 cell growth when implanted into the flanks of nu/nu mice. Mechanistic studies revealed that berberine decreased mitochondrial membrane potential and intracellular ATP levels and induced potent AMPK activation, as shown by phosphorylation of AMPK α subunit at Thr-172 and acetyl-CoA carboxylase (ACC) at Ser79. Furthermore, berberine dose-dependently inhibited mTORC1 (phosphorylation of S6K at Thr389 and S6 at Ser240/244) and ERK activation in PDAC cells stimulated by insulin and neurotensin or fetal bovine serum. Knockdown of α1 and α2 catalytic subunit expression of AMPK reversed the inhibitory effect produced by treatment with low concentrations of berberine on mTORC1, ERK and DNA synthesis in PDAC cells. However, at higher concentrations, berberine inhibited mitogenic signaling (mTORC1 and ERK) and DNA synthesis through an AMPK-independent mechanism. Similar results were obtained with metformin used at doses that induced either modest or pronounced reductions in intracellular ATP levels, which were virtually identical to the decreases in ATP levels obtained in response to berberine. We propose that berberine and metformin inhibit mitogenic signaling in PDAC cells through dose-dependent AMPK-dependent and independent pathways.
Collapse
Affiliation(s)
- Ming Ming
- Division of Digestive Diseases, Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - James Sinnett-Smith
- Division of Digestive Diseases, Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
- CURE: Digestive Diseases Research Center, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Jia Wang
- Division of Digestive Diseases, Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Heloisa P. Soares
- Division of Hematology-Oncology, Department of Medicine David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Steven H. Young
- Division of Digestive Diseases, Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
- CURE: Digestive Diseases Research Center, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Guido Eibl
- Department of Surgery, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
- CURE: Digestive Diseases Research Center, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Enrique Rozengurt
- Division of Digestive Diseases, Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
- CURE: Digestive Diseases Research Center, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
- Molecular Biology Institute, University of California Los Angeles, Los Angeles, California, United States of America
- * E-mail:
| |
Collapse
|
19
|
Tape CJ, Norrie IC, Worboys JD, Lim L, Lauffenburger DA, Jørgensen C. Cell-specific labeling enzymes for analysis of cell-cell communication in continuous co-culture. Mol Cell Proteomics 2014; 13:1866-76. [PMID: 24820872 DOI: 10.1074/mcp.o113.037119] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We report the orthologous screening, engineering, and optimization of amino acid conversion enzymes for cell-specific proteomic labeling. Intracellular endoplasmic-reticulum-anchored Mycobacterium tuberculosis diaminopimelate decarboxylase (DDC(M.tub-KDEL)) confers cell-specific meso-2,6-diaminopimelate-dependent proliferation to multiple eukaryotic cell types. Optimized lysine racemase (Lyr(M37-KDEL)) supports D-lysine specific proliferation and efficient cell-specific isotopic labeling. When ectopically expressed in discrete cell types, these enzymes confer 90% cell-specific isotopic labeling efficiency after 10 days of co-culture. Moreover, DDC(M.tub-KDEL) and Lyr(M37-KDEL) facilitate equally high cell-specific labeling fidelity without daily media exchange. Consequently, the reported novel enzyme pairing can be used to study cell-specific signaling in uninterrupted, continuous co-cultures. Demonstrating the importance of increased labeling stability for addressing novel biological questions, we compare the cell-specific phosphoproteome of fibroblasts in direct co-culture with epithelial tumor cells in both interrupted (daily media exchange) and continuous (no media exchange) co-cultures. This analysis identified multiple cell-specific phosphorylation sites specifically regulated in the continuous co-culture. Given their applicability to multiple cell types, continuous co-culture labeling fidelity, and suitability for long-term cell-cell phospho-signaling experiments, we propose DDC(M.tub-KDEL) and Lyr(M37-KDEL) as excellent enzymes for cell-specific labeling with amino acid precursors.
Collapse
Affiliation(s)
- Christopher J Tape
- From the ‡Division of Cancer Biology, The Institute of Cancer Research, 237 Fulham Road, London, SW3 6JB, UK; §Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Ida C Norrie
- From the ‡Division of Cancer Biology, The Institute of Cancer Research, 237 Fulham Road, London, SW3 6JB, UK
| | - Jonathan D Worboys
- From the ‡Division of Cancer Biology, The Institute of Cancer Research, 237 Fulham Road, London, SW3 6JB, UK
| | - Lindsay Lim
- From the ‡Division of Cancer Biology, The Institute of Cancer Research, 237 Fulham Road, London, SW3 6JB, UK
| | - Douglas A Lauffenburger
- §Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Claus Jørgensen
- From the ‡Division of Cancer Biology, The Institute of Cancer Research, 237 Fulham Road, London, SW3 6JB, UK;
| |
Collapse
|
20
|
Mok KW, Mruk DD, Cheng CY. Regulation of blood-testis barrier (BTB) dynamics during spermatogenesis via the "Yin" and "Yang" effects of mammalian target of rapamycin complex 1 (mTORC1) and mTORC2. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2013; 301:291-358. [PMID: 23317821 DOI: 10.1016/b978-0-12-407704-1.00006-3] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
In mammalian testes, haploid spermatozoa are formed from diploid spermatogonia during spermatogenesis, which is a complicated cellular process. While these cellular events were reported in the 1960s and 1970s, the underlying molecular mechanism(s) that regulates these events remained unexplored until the past ∼10 years. For instance, adhesion proteins were shown to be integrated components at the Sertoli cell-cell interface and/or the Sertoli-spermatid interface in the late 1980s. But only until recently, studies have demonstrated that some of the adhesion proteins serve as the platform for signal transduction that regulates cell adhesion. In this chapter, a brief summary and critical discussion are provided on the latest findings regarding these cell-adhesion proteins in the testis and their relationship to spermatogenesis. Moreover, antagonistic effects of two mammalian target of rapamycin (mTOR) complexes, known as mTORC1 and mTORC2, on cell-adhesion function in the testis are discussed. Finally, a hypothetic model is presented to depict how these two mTOR-signaling complexes having the "yin" and "yang" antagonistic effects on the Sertoli cell tight junction (TJ)-permeability barrier can maintain the blood-testis barrier (BTB) integrity during the epithelial cycle while preleptotene spermatocytes are crossing the BTB.
Collapse
Affiliation(s)
- Ka Wai Mok
- Mary M. Wohlford Laboratory for Male Contraceptive Research, Center for Biomedical Research, Population Council, New York, USA
| | | | | |
Collapse
|
21
|
Kim SH, Jang YH, Chau GC, Pyo S, Um SH. Prognostic significance and function of phosphorylated ribosomal protein S6 in esophageal squamous cell carcinoma. Mod Pathol 2013; 26:327-35. [PMID: 22996377 DOI: 10.1038/modpathol.2012.161] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Ribosomal protein S6 is a key regulator of 40S ribosome biogenesis, and its phosphorylation is closely related to cell growth capacity. However, as a downstream target of S6 kinases, the clinical significance and the roles of S6 and S6 phosphorylation in cell viability and motility of esophageal squamous cell carcinoma remain unclear. Here, we show that high level of phosphorylated-ribosomal protein S6 (p-S6) (immunohistochemistry score ≥5) and an increased ratio of p-S6/S6 (immunohistochemistry score ≥0.75) were significantly associated with shortened disease-free survival in patients with esophageal squamous cell carcinoma in univariate analysis (P=0.049 and P<0.001, respectively). After adjusting for age, tumor-nodes-metastasis stage, chemotherapy, and radiation therapy in multivariate analysis, both p-S6 (hazard ratio 2.21, P=0.005) and p-S6/S6 (hazard ratio 2.40, P<0.001) remained independent adverse prognostic factors. In addition, S6 and S6 kinase 1 knockdown resulted in attenuation of viability by suppressing cyclin D1 expression in esophageal cancer cells. Furthermore, depletion of S6 and S6 kinase 1 resulted in a reduction in esophageal cancer cell migration and invasion. This was paralleled by a reduction in focal adhesion and by suppression of extracellular signal-regulated kinase and c-jun N-terminal kinase phosphorylation, which control cell motility. Collectively, these findings suggest that p-S6 and the ratio of p-S6/S6 are closely relevant to tumor progression and have prognostic significance in esophageal squamous cell carcinoma.
Collapse
Affiliation(s)
- Seok-Hyung Kim
- Department of Pathology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | | | | | | | | |
Collapse
|
22
|
Palaniappan M, Menon B, Menon KMJ. Stimulatory effect of insulin on theca-interstitial cell proliferation and cell cycle regulatory proteins through MTORC1 dependent pathway. Mol Cell Endocrinol 2013; 366:81-9. [PMID: 23261705 PMCID: PMC3552006 DOI: 10.1016/j.mce.2012.12.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/09/2012] [Revised: 11/22/2012] [Accepted: 12/05/2012] [Indexed: 11/25/2022]
Abstract
The present study examined the effect of insulin-mediated activation of the mammalian target of rapamycin complex 1 (MTORC1) signaling network on the proliferation of primary culture of theca-interstitial (T-I) cells. Our results show that insulin treatment increased proliferation of the T-I cells through the MTORC1-dependent signaling pathway by increasing cell cycle regulatory proteins. Inhibition of ERK1/2 signaling caused partial reduction of insulin-induced phosphorylation of RPS6KB1 and RPS6 whereas inhibition of PI3-kinase signaling completely blocked the insulin response. Pharmacological inhibition of MTORC1 with rapamycin abrogated the insulin-induced phosphorylation of EIF4EBP1, RPS6KB1 and its downstream effector, RPS6. These results were further confirmed by demonstrating that knockdown of Mtor using siRNA reduced the insulin-stimulated MTORC1 signaling. Furthermore, insulin-stimulated T-I cell proliferation and the expression of cell cycle regulatory proteins CDK4, CCND3 and PCNA were also blocked by rapamycin. Taken together, the present studies show that insulin stimulates cell proliferation and cell cycle regulatory proteins in T-I cells via activation of the MTORC1 signaling pathway.
Collapse
Affiliation(s)
- Murugesan Palaniappan
- Department of Obstetrics and Gynecology, University of Michigan Medical School, Ann Arbor, MI 48109, United States
| | | | | |
Collapse
|
23
|
The role of mTORC1 in regulating protein synthesis and skeletal muscle mass in response to various mechanical stimuli. Rev Physiol Biochem Pharmacol 2013; 166:43-95. [PMID: 24442322 DOI: 10.1007/112_2013_17] [Citation(s) in RCA: 91] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Skeletal muscle plays a fundamental role in mobility, disease prevention, and quality of life. Skeletal muscle mass is, in part, determined by the rates of protein synthesis, and mechanical loading is a major regulator of protein synthesis and skeletal muscle mass. The mammalian/mechanistic target of rapamycin (mTOR), found in the multi-protein complex, mTORC1, is proposed to play an essential role in the regulation of protein synthesis and skeletal muscle mass. The purpose of this review is to examine the function of mTORC1 in relation to protein synthesis and cell growth, the current evidence from rodent and human studies for the activation of mTORC1 signaling by different types of mechanical stimuli, whether mTORC1 signaling is necessary for changes in protein synthesis and skeletal muscle mass that occur in response to different types of mechanical stimuli, and the proposed molecular signaling mechanisms that may be responsible for the mechanical activation of mTORC1 signaling.
Collapse
|
24
|
Oubrahim H, Wong A, Wilson BA, Chock PB. Mammalian target of rapamycin complex 1 (mTORC1) plays a role in Pasteurella multocida toxin (PMT)-induced protein synthesis and proliferation in Swiss 3T3 cells. J Biol Chem 2012; 288:2805-15. [PMID: 23223576 DOI: 10.1074/jbc.m112.427351] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Pasteurella multocida toxin (PMT) is a potent mitogen known to activate several signaling pathways via deamidation of a conserved glutamine residue in the α subunit of heterotrimeric G-proteins. However, the detailed mechanism behind mitogenic properties of PMT is unknown. Herein, we show that PMT induces protein synthesis, cell migration, and proliferation in serum-starved Swiss 3T3 cells. Concomitantly PMT induces phosphorylation of ribosomal S6 kinase (S6K1) and its substrate, ribosomal S6 protein (rpS6), in quiescent 3T3 cells. The extent of the phosphorylation is time and PMT concentration dependent, and is inhibited by rapamycin and Torin1, the two specific inhibitors of the mammalian target of rapamycin complex 1 (mTORC1). Interestingly, PMT-mediated mTOR signaling activation was observed in MEF WT but not in Gα(q/11) knock-out cells. These observations are consistent with the data indicating that PMT-induced mTORC1 activation proceeds via the deamidation of Gα(q/11), which leads to the activation of PLCβ to generate diacylglycerol and inositol trisphosphate, two known activators of the PKC pathway. Exogenously added diacylglycerol or phorbol 12-myristate 13-acetate, known activators of PKC, leads to rpS6 phosphorylation in a rapamycin-dependent manner. Furthermore, PMT-induced rpS6 phosphorylation is inhibited by PKC inhibitor, Gö6976. Although PMT induces epidermal growth factor receptor activation, it exerts no effect on PMT-induced rpS6 phosphorylation. Together, our findings reveal for the first time that PMT activates mTORC1 through the Gα(q/11)/PLCβ/PKC pathway. The fact that PMT-induced protein synthesis and cell migration is partially inhibited by rapamycin indicates that these processes are in part mediated by the mTORC1 pathway.
Collapse
Affiliation(s)
- Hammou Oubrahim
- Laboratory of Biochemistry, NHLBI, National Institutes of Health, Bethesda, Maryland 20892-8012, USA.
| | | | | | | |
Collapse
|
25
|
Abstract
Mammalian target of rapamycin (mTOR) is a giant protein kinase that controls cell proliferation, growth, and metabolism. mTOR is regulated by nutrient availability, by mitogens, and by stress, and operates through two independently regulated hetero-oligomeric complexes. We have attempted to identify the cellular components necessary to maintain the activity of mTOR complex 1 (mTORC1), the amino acid-dependent, rapamycin-inhibitable complex, using a whole genome approach involving RNAi-induced depletion of cellular polypeptides. We have used a pancreatic ductal adenocarcinoma (PDAC) cell line, Mia-PaCa for this screen; as with many pancreatic cancers, these cells exhibit constitutive activation of mTORC1. PDAC is the most common form of pancreatic cancer and the 5-year survival rate remains 3-5% despite current nonspecific and targeted therapies. Although rapamycin-related mTOR inhibitors have yet to demonstrate encouraging clinical responses, it is now evident that this class of compounds is capable of only partial mTORC1 inhibition. Identifying previously unappreciated proteins needed for maintenance of mTORC1 activity may provide new targets and lead to the development of beneficial therapies for pancreatic cancer.
Collapse
|
26
|
Haloperidol regulates the state of phosphorylation of ribosomal protein S6 via activation of PKA and phosphorylation of DARPP-32. Neuropsychopharmacology 2011; 36:2561-70. [PMID: 21814187 PMCID: PMC3194082 DOI: 10.1038/npp.2011.144] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Administration of typical antipsychotic drugs, such as haloperidol, promotes cAMP-dependent signaling in the medium spiny neurons (MSNs) of the striatum. In this study, we have examined the effect of haloperidol on the state of phosphorylation of the ribosomal protein S6 (rpS6), a component of the small 40S ribosomal subunit. We found that haloperidol increases the phosphorylation of rpS6 at the dual site Ser235/236, which is involved in the regulation of mRNA translation. This effect was exerted in the MSNs of the indirect pathway, which express specifically dopamine D2 receptors (D2Rs) and adenosine A2 receptors (A2ARs). The effect of haloperidol was decreased by blockade of A2ARs or by genetic attenuation of the Gα(olf) protein, which couples A2ARs to activation of adenylyl cyclase. Moreover, stimulation of cAMP-dependent protein kinase A (PKA) increased Ser235/236 phosphorylation in cultured striatal neurons. The ability of haloperidol to promote rpS6 phosphorylation was abolished in knock-in mice deficient for PKA activation of the protein phosphatase-1 inhibitor, dopamine- and cAMP-regulated phosphoprotein of 32 kDa. In contrast, pharmacological or genetic inactivation of p70 rpS6 kinase 1, or extracellular signal-regulated kinases did not affect haloperidol-induced rpS6 phosphorylation. These results identify PKA as a major rpS6 kinase in neuronal cells and suggest that regulation of protein synthesis through rpS6 may be a potential target of antipsychotic drugs.
Collapse
|
27
|
Lee RS, House CM, Cristiano BE, Hannan RD, Pearson RB, Hannan KM. Relative Expression Levels Rather Than Specific Activity Plays the Major Role in Determining In Vivo AKT Isoform Substrate Specificity. Enzyme Res 2011; 2011:720985. [PMID: 21869924 PMCID: PMC3160084 DOI: 10.4061/2011/720985] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2011] [Revised: 06/08/2011] [Accepted: 06/09/2011] [Indexed: 12/18/2022] Open
Abstract
The AKT protooncogene mediates many cellular processes involved in normal development and disease states such as cancer. The three structurally similar isoforms: AKT1, AKT2, and AKT3 exhibit both functional redundancy and isoform-specific functions; however the basis for their differential signalling remains unclear. Here we show that in vitro, purified AKT3 is ∼47-fold more active than AKT1 at phosphorylating peptide and protein substrates. Despite these marked variations in specific activity between the individual isoforms, a comprehensive analysis of phosphorylation of validated AKT substrates indicated only subtle differences in signalling via individual isoforms in vivo. Therefore, we hypothesise, at least in this model system, that relative tissue/cellular abundance, rather than specific activity, plays the dominant role in determining AKT substrate specificity in situ.
Collapse
Affiliation(s)
- Rachel S Lee
- Growth Control and Differentiation Program, Trescowthick Research Laboratories, Peter MacCallum Cancer Centre, Melbourne, VIC 8006, Australia
| | | | | | | | | | | |
Collapse
|
28
|
Fenton TR, Gout IT. Functions and regulation of the 70kDa ribosomal S6 kinases. Int J Biochem Cell Biol 2010; 43:47-59. [PMID: 20932932 DOI: 10.1016/j.biocel.2010.09.018] [Citation(s) in RCA: 250] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2010] [Revised: 09/17/2010] [Accepted: 09/23/2010] [Indexed: 01/01/2023]
Abstract
The 70kDa ribosomal protein S6 kinases, S6K1 and S6K2 are two highly homologous serine/threonine kinases that are activated in response to growth factors, cytokines and nutrients. The S6 kinases have been linked to diverse cellular processes, including protein synthesis, mRNA processing, glucose homeostasis, cell growth and survival. Studies in model organisms have highlighted the roles that S6K activity plays in a number of pathologies, including obesity, diabetes, ageing and cancer. The importance of S6K function in human diseases has led to the development of S6K-specific inhibitors by a number of companies, offering the promise of improved tools with which to study these enzymes and potentially the effective targeting of deregulated S6K signalling in patients. Here we review the current literature on the role of S6Ks in the regulation of cell growth, survival and proliferation downstream of various signalling pathways and how their dysregulation contributes to the pathogenesis of human diseases.
Collapse
Affiliation(s)
- Tim R Fenton
- Ludwig Institute for Cancer Research, University of California San Diego, 9500 Gilman Dr, La Jolla, CA 92093-0660, USA
| | | |
Collapse
|
29
|
Palaniappan M, Menon KMJ. Human chorionic gonadotropin stimulates theca-interstitial cell proliferation and cell cycle regulatory proteins by a cAMP-dependent activation of AKT/mTORC1 signaling pathway. Mol Endocrinol 2010; 24:1782-93. [PMID: 20660299 DOI: 10.1210/me.2010-0044] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
In addition to playing a cardinal role in androgen production, LH also regulates growth and proliferation of theca-interstitial (T-I) cells. Here, we show for the first time that LH/human chorionic gonadotropin (hCG) regulates T-I cell proliferation via the mammalian target of rapamycin complex 1 (mTORC1) signaling network. LH/hCG treatment showed a time-dependent stimulation of T-I cell proliferation and phosphorylation of protein kinase B (AKT), ERK1/2, and ribosomal protein (rp)S6 kinase 1 (S6K1), and its downstream effector, rpS6. Pharmacological inhibition of ERK1/2 signaling did not block the hCG-induced phosphorylation of tuberin, the upstream regulator of mTORC1 or S6K1, the downstream target of mTORC1. However, inhibition of AKT signaling completely blocked the hCG response. Furthermore, the AKT-specific inhibitor abolished forskolin (FSK)-stimulated phosphorylation of AKT, tuberin, S6K1, and rpS6. Human CG and FSK-mediated phosphorylation of AKT and downstream targets of mTORC1 were attenuated by inhibition of adenylyl cyclase. Pharmacologic targeting of mTORC1 with rapamycin also abrogated hCG or FSK-induced phosphorylation of S6K1, rpS6, and eukaryotic initiation factor 4E binding protein 1. In addition, hCG or FSK-mediated up-regulation of the cell cycle regulatory proteins cyclin-dependent kinase 4, cyclin D3, and proliferating cell nuclear antigen was blocked by rapamycin. These results were further confirmed by demonstrating that knockdown of mTORC1 using small interfering RNA abolished hCG-mediated increases in cell proliferation and the expression of cyclin D3 and proliferating cell nuclear antigen. Taken together, the present studies show a novel intracellular signaling pathway for T-I cell proliferation involving LH/hCG-mediated activation of the AKT/mTORC1 signaling cascade.
Collapse
Affiliation(s)
- Murugesan Palaniappan
- Department of Obstetrics, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | | |
Collapse
|
30
|
Moore CEJ, Xie J, Gomez E, Herbert TP. Identification of cAMP-dependent kinase as a third in vivo ribosomal protein S6 kinase in pancreatic beta-cells. J Mol Biol 2009; 389:480-94. [PMID: 19376132 DOI: 10.1016/j.jmb.2009.04.020] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2009] [Revised: 04/06/2009] [Accepted: 04/09/2009] [Indexed: 01/17/2023]
Abstract
Ribosomal protein S6 (rpS6) is phosphorylated in vivo by isoforms of p70 S6 protein kinase and p90 ribosomal S6 kinase, and there is good evidence that it plays a positive role in controlling pancreatic beta-cell size and function. In this report, we demonstrate in the pancreatic beta-cell line MIN6 (mouse insulinoma cell line 6) and islets of Langerhans that agents which stimulate increases in cAMP, such as glucagon-like peptide-1 and forskolin, lead to the phosphorylation of rpS6 at Ser235/Ser236 independently of the activation of the currently known in vivo rpS6 kinases via a pathway that is sensitive to inhibitors of cAMP-dependent protein kinase [protein kinase A (PKA)]. This cAMP-dependent rpS6 kinase activity is also sensitive to PKI in vitro, and PKA exclusively phosphorylates recombinant rpS6 on Ser235/Ser236 in vitro. With these data taken together, we conclude that PKA can phosphorylate rpS6 exclusively at Ser235/Ser236 in vivo in pancreatic beta-cells, thus providing a potentially important link between cAMP signalling and the regulation of protein synthesis. Lastly, we provide evidence that PKA is also likely to phosphorylate rpS6 on Ser235/Ser236 in vivo in a number of other mammalian cell types.
Collapse
Affiliation(s)
- Claire E J Moore
- Department of Cell Physiology and Pharmacology, Faculty of Medicine and Biological Sciences, University of Leicester, The Henry Wellcome Building, University Road, Leicester LE1 9HN, UK
| | | | | | | |
Collapse
|
31
|
Abstract
The activation of PI3K (phosphoinositide 3-kinase) family members is a universal event in response to virtually all cytokines, growth factors and hormones. As a result of formation of PtdIns with an added phosphate at the 3 position of the inositol ring, activation of the protein kinases PDK1 (phosphoinositide-dependent kinase 1) and PKB (protein kinase B)/Akt occurs. The PI3K/PKB pathway impinges upon a remarkable array of intracellular events that influence either directly or indirectly whether or not a cell will undergo apoptosis. In this review, the many ways in which PI3K/PKB can control these processes are summarized. Not all of the events described will necessarily play a role in any one cell type, but a subset of these events is probably essential for the survival of every cell.
Collapse
|
32
|
Meyuhas O. Physiological roles of ribosomal protein S6: one of its kind. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2008; 268:1-37. [PMID: 18703402 DOI: 10.1016/s1937-6448(08)00801-0] [Citation(s) in RCA: 168] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The phosphorylation of ribosomal protein S6 (rpS6), which occurs in response to a wide variety of stimuli on five evolutionarily conserved serine residues, has attracted much attention since its discovery more than three decades ago. However, despite a large body of information on the respective kinases and the signal transduction pathways, the role of this phosphorylation remained obscure. It is only recent that targeting the genes encoding rpS6, the phosphorylatable serine residues or the respective kinases that the unique role of rpS6 and its posttranslational modification have started to be elucidated. This review focuses primarily on the critical role of rpS6 for mouse development, the pathways that transduce various signals into rpS6 phosphorylation, and the physiological functions of this modification. The mechanism(s) underlying the diverse effects of rpS6 phosphorylation on cellular and organismal physiology has yet to be determined. However, a model emerging from the currently available data suggests that rpS6 phosphorylation operates, at least partly, by counteracting positive signals simultaneously induced by rpS6 kinase, and thus might be involved in fine-tuning of the cellular response to these signals.
Collapse
Affiliation(s)
- Oded Meyuhas
- Department of Biochemistry, Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel
| |
Collapse
|
33
|
Schnoke M, Midura RJ. Pulsed electromagnetic fields rapidly modulate intracellular signaling events in osteoblastic cells: comparison to parathyroid hormone and insulin. J Orthop Res 2007; 25:933-40. [PMID: 17427956 DOI: 10.1002/jor.20373] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Pulsed electromagnetic field (PEMF) devices are approved for the healing of bone nonunions, but there is a lack of understanding as to their mechanism of action at the cell and molecular level. Intermittent parathyroid hormone (PTH) therapy is currently utilized for treatment of osteoporosis, and is also being investigated for the purpose of augmenting fracture healing. Insulin and IGF-1 are also thought to play important anabolic roles in osteogenesis. In this report, signaling pathways activated by acute PTH or insulin treatments were compared to those activated by PEMF treatment in osteoblast-like cells. Some signaling molecules like the extracellular response kinases 1/2 (Erk1/2) and the cAMP response element binding protein (CREB) were activated by insulin and PTH, respectively, but not by PEMF treatment. Other signaling molecules like the insulin receptor substrate-1 (IRS-1), the S6 ribosomal subunit kinase, and the endothelial nitric oxide synthase (eNOS) were phosphorylated by PTH, insulin, and PEMF to the same relative extent and within the same time frame. IRS-1, eNOS, and S6 have been implicated in bone anabolism, and our results suggest that the anabolic effects of PEMF may be mediated, in part, through the activation of these proteins.
Collapse
Affiliation(s)
- Matthew Schnoke
- Department of Biomedical Engineering and The Orthopaedic Research Center, Lerner Research Institute, ND20, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, Ohio 44195, USA
| | | |
Collapse
|
34
|
Roux PP, Shahbazian D, Vu H, Holz MK, Cohen MS, Taunton J, Sonenberg N, Blenis J. RAS/ERK signaling promotes site-specific ribosomal protein S6 phosphorylation via RSK and stimulates cap-dependent translation. J Biol Chem 2007; 282:14056-64. [PMID: 17360704 PMCID: PMC3618456 DOI: 10.1074/jbc.m700906200] [Citation(s) in RCA: 572] [Impact Index Per Article: 33.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Converging signals from the mammalian target of rapamycin (mTOR) and phosphoinositide 3-kinase (PI3K) pathways are well established to modulate translation initiation. Less is known regarding the molecular basis of protein synthesis regulated by other inputs, such as agonists of the Ras/extracellular signal-regulated kinase (ERK) signaling cascade. Ribosomal protein (rp) S6 is a component of the 40S ribosomal subunit that becomes phosphorylated at several serine residues upon mitogen stimulation, but the exact molecular mechanisms regulating its phosphorylation and the function of phosphorylated rpS6 is poorly understood. Here, we provide evidence that activation of the p90 ribosomal S6 kinases (RSKs) by serum, growth factors, tumor promoting phorbol esters, and oncogenic Ras is required for rpS6 phosphorylation downstream of the Ras/ERK signaling cascade. We demonstrate that while ribosomal S6 kinase 1 (S6K1) phosphorylates rpS6 at all sites, RSK exclusively phosphorylates rpS6 at Ser(235/236) in vitro and in vivo using an mTOR-independent mechanism. Mutation of rpS6 at Ser(235/236) reveals that phosphorylation of these sites promotes its recruitment to the 7-methylguanosine cap complex, suggesting that Ras/ERK signaling regulates assembly of the translation preinitiation complex. These data demonstrate that RSK provides an mTOR-independent pathway linking the Ras/ERK signaling cascade to the translational machinery.
Collapse
Affiliation(s)
- Philippe P Roux
- Department of Pathology and Cell Biology, Institut de Recherche en Immunologie et en Cancérologie (IRIC), Université de Montréal, Montréal, Québec, Canada.
| | | | | | | | | | | | | | | |
Collapse
|
35
|
Ohji G, Hidayat S, Nakashima A, Tokunaga C, Oshiro N, Yoshino KI, Yokono K, Kikkawa U, Yonezawa K. Suppression of the mTOR-raptor signaling pathway by the inhibitor of heat shock protein 90 geldanamycin. J Biochem 2007; 139:129-35. [PMID: 16428328 DOI: 10.1093/jb/mvj008] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Heat shock protein 90 (Hsp90) was co-immunoprecipitated with raptor, the binding partner of the mammalian target of rapamycin (mTOR) from HEK293 cells. Hsp90 was detected in the anti-raptor antibody immunoprecipitates prepared from the cell extract by immunoblot analysis using the anti-Hsp90 antibody, and the association of these two proteins was confirmed by immunoprecipitation from the cells co-expressing Hsp90 and raptor as epitope-tagged molecules. Geldanamycin, a potent inhibitor of Hsp90, disrupted the in vivo binding of Hsp90 to raptor without affecting the association of raptor and mTOR, and suppressed the phosphorylation by mTOR of the downstream translational regulators p70 S6 kinase (S6K) and eukaryotic initiation factor 4E-binding protein 1 (4E-BP1). The protein kinase activity of S6K as well as the phosphorylation of the substrate, 40S ribosomal protein S6, were lowered in the geldanamycin-treated cells. These results indicate that Hsp90 is involved in the regulation of protein translation by facilitating the phosphorylation reaction of 4E-BP1 and S6K catalyzed by the mTOR/raptor complex through the association with raptor, and that the mTOR signaling pathway is a novel target of geldanamycin.
Collapse
Affiliation(s)
- Goh Ohji
- Biosignal Research Center, Kobe University, Kobe 657-8501
| | | | | | | | | | | | | | | | | |
Collapse
|
36
|
Schumacher AM, Velentza AV, Watterson DM, Dresios J. Death-associated protein kinase phosphorylates mammalian ribosomal protein S6 and reduces protein synthesis. Biochemistry 2007; 45:13614-21. [PMID: 17087515 PMCID: PMC4404312 DOI: 10.1021/bi060413y] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Death-associated protein kinase (DAPK) is a pro-apoptotic, calcium/calmodulin-regulated protein kinase that is a drug discovery target for neurodegenerative disorders. Despite the potential profound physiological role of DAPK in neuronal function and pathophysiology, the endogenous substrate(s) of this kinase and the mechanisms via which DAPK elicits its biological action remain largely unknown. We report here that the mammalian 40S ribosomal protein S6 is a DAPK substrate. Results from immunoprecipitation experiments are consistent with endogenous DAPK being associated with endogenous S6 in rat brain. When S6 is a component of the 40S ribosomal subunit complex, DAPK selectively phosphorylates it at serine 235, one of the five sites in S6 that are phosphorylated by the S6 kinase family of proteins. The amino acid sequence flanking serine 235 matches the established pattern for DAPK peptide and protein substrates. Kinetic analyses using purified 40S subunits revealed a K(m) value of 9 microM, consistent with S6 being a potential physiological substrate of DAPK. This enzyme-substrate relationship has functional significance. DAPK suppresses translation in rabbit reticulocyte lysate, and treatment of neuroblastoma cells with a stimulator of DAPK reduces protein synthesis. In both cases, suppression of translation correlates with increased phosphorylation of S6 at serine 235. These results demonstrate that DAPK is a S6 kinase and provide evidence for a novel role of DAPK in the regulation of translation.
Collapse
Affiliation(s)
- Andrew M. Schumacher
- Center for Drug Discovery and Chemical Biology, Northwestern University, 303 E. Chicago Avenue, W-896, Chicago, IL 60611
| | - Anastasia V. Velentza
- Center for Drug Discovery and Chemical Biology, Northwestern University, 303 E. Chicago Avenue, W-896, Chicago, IL 60611
| | - D. Martin Watterson
- Center for Drug Discovery and Chemical Biology, Northwestern University, 303 E. Chicago Avenue, W-896, Chicago, IL 60611
| | - John Dresios
- The Scripps Research Institute, Department of Neurobiology, 10550 N. Torrey Pines Road, La Jolla, CA 92037
- To whom correspondence should be addressed: The Scripps Research Institute, Department of Neurobiology, 10550 N. Torrey Pines Road, La Jolla, CA 92037, Tel: 858-784-2636; Fax: 858-784-2646;
| |
Collapse
|
37
|
Roberts NA, Marber MS, Avkiran M. Specificity of action of bisindolylmaleimide protein kinase C inhibitors: do they inhibit the 70kDa ribosomal S6 kinase in cardiac myocytes? Biochem Pharmacol 2005; 68:1923-8. [PMID: 15476663 DOI: 10.1016/j.bcp.2004.07.040] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2004] [Accepted: 07/28/2004] [Indexed: 11/20/2022]
Abstract
Bisindolylmaleimide protein kinase C (PKC) inhibitors, such as GF109203X and Ro31-8220, are used as pharmacological tools in many cellular systems. However, in vitro, GF109203X and Ro31-8220 also inhibit the 70kDa ribosomal S6 kinase (p70(S6K)) with similar potency. We determined whether GF109203X and Ro31-8220 inhibit p70(S6K) activity in intact adult rat ventricular myocytes (ARVM). First, we confirmed that increased phosphorylation of the 40S ribosomal S6 protein (a cellular substrate for both p70(S6K) and the 90 kDa ribosomal S6 kinase) in response to stimulation of ARVM by insulin-like growth factor-1 (300 ng/mL; 10 min) occurs specifically through rapamycin-sensitive activation of p70(S6K). Then, using this response as the index of cellular p70(S6K) activity, we determined the effects of GF109203X and Ro31-8220 (1, 3 or 10 microM) on such activity. At these concentrations, neither GF109203X nor Ro31-8220 inhibited cellular p70(S6K) activity. In contrast, even at 1 microM, cellular PKC activity (stimulated by a 3 min exposure to 30 nM phorbol 12-myristate 13-acetate) was significantly inhibited by each agent. We conclude that; (1) data obtained in vitro may not necessarily be extrapolated to intact cells and (2) inhibition of p70(S6K) is unlikely to contribute to the actions of GF109203X and Ro31-8220 in ARVM.
Collapse
Affiliation(s)
- Neil A Roberts
- Cardiovascular Division, King's College London, The Rayne Institute, St Thomas' Hospital, London SE17EH, UK
| | | | | |
Collapse
|
38
|
Pende M, Um SH, Mieulet V, Sticker M, Goss VL, Mestan J, Mueller M, Fumagalli S, Kozma SC, Thomas G. S6K1(-/-)/S6K2(-/-) mice exhibit perinatal lethality and rapamycin-sensitive 5'-terminal oligopyrimidine mRNA translation and reveal a mitogen-activated protein kinase-dependent S6 kinase pathway. Mol Cell Biol 2004; 24:3112-24. [PMID: 15060135 PMCID: PMC381608 DOI: 10.1128/mcb.24.8.3112-3124.2004] [Citation(s) in RCA: 619] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2003] [Revised: 09/18/2003] [Accepted: 01/14/2004] [Indexed: 11/20/2022] Open
Abstract
Activation of 40S ribosomal protein S6 kinases (S6Ks) is mediated by anabolic signals triggered by hormones, growth factors, and nutrients. Stimulation by any of these agents is inhibited by the bacterial macrolide rapamycin, which binds to and inactivates the mammalian target of rapamycin, an S6K kinase. In mammals, two genes encoding homologous S6Ks, S6K1 and S6K2, have been identified. Here we show that mice deficient for S6K1 or S6K2 are born at the expected Mendelian ratio. Compared to wild-type mice, S6K1(-/-) mice are significantly smaller, whereas S6K2(-/-) mice tend to be slightly larger. However, mice lacking both genes showed a sharp reduction in viability due to perinatal lethality. Analysis of S6 phosphorylation in the cytoplasm and nucleoli of cells derived from the distinct S6K genotypes suggests that both kinases are required for full S6 phosphorylation but that S6K2 may be more prevalent in contributing to this response. Despite the impairment of S6 phosphorylation in cells from S6K1(-/-)/S6K2(-/-) mice, cell cycle progression and the translation of 5'-terminal oligopyrimidine mRNAs were still modulated by mitogens in a rapamycin-dependent manner. Thus, the absence of S6K1 and S6K2 profoundly impairs animal viability but does not seem to affect the proliferative responses of these cell types. Unexpectedly, in S6K1(-/-)/S6K2(-/-) cells, S6 phosphorylation persisted at serines 235 and 236, the first two sites phosphorylated in response to mitogens. In these cells, as well as in rapamycin-treated wild-type, S6K1(-/-), and S6K2(-/-) cells, this step was catalyzed by a mitogen-activated protein kinase (MAPK)-dependent kinase, most likely p90rsk. These data reveal a redundancy between the S6K and the MAPK pathways in mediating early S6 phosphorylation in response to mitogens.
Collapse
Affiliation(s)
- Mario Pende
- Friedrich Miescher Institute for Biomedical Research, 4058 Basel, Switzerland
| | | | | | | | | | | | | | | | | | | |
Collapse
|
39
|
Stover DR, Caldwell J, Marto J, Root K, Mestan J, Stumm M, Ornatsky O, Orsi C, Radosevic N, Liao L, Fabbro D, Moran MF. Differential phosphoprofiles of EGF and EGFR kinase inhibitor-treated human tumor cells and mouse xenografts. Clin Proteomics 2004. [DOI: 10.1385/cp:1:1:069] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
|
40
|
Suh JM, Song JH, Kim DW, Kim H, Chung HK, Hwang JH, Kim JM, Hwang ES, Chung J, Han JH, Cho BY, Ro HK, Shong M. Regulation of the phosphatidylinositol 3-kinase, Akt/protein kinase B, FRAP/mammalian target of rapamycin, and ribosomal S6 kinase 1 signaling pathways by thyroid-stimulating hormone (TSH) and stimulating type TSH receptor antibodies in the thyroid gland. J Biol Chem 2003; 278:21960-71. [PMID: 12668683 DOI: 10.1074/jbc.m300805200] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Thyroid-stimulating hormone (TSH) regulates the growth and differentiation of thyrocytes by activating the TSH receptor (TSHR). This study investigated the roles of the phosphatidylinositol 3-kinase (PI3K), PDK1, FRAP/mammalian target of rapamycin, and ribosomal S6 kinase 1 (S6K1) signaling mechanism by which TSH and the stimulating type TSHR antibodies regulate thyrocyte proliferation and the follicle activities in vitro and in vivo. The TSHR immunoprecipitates exhibited PI3K activity, which was higher in the cells treated with either TSH or 8-bromo-cAMP. TSH and cAMP increased the tyrosine phosphorylation of TSHR and the association between TSHR and the p85alpha regulatory subunit of PI3K. TSH induced a redistribution of PDK1 from the cytoplasm to the plasma membrane in the cells in a PI3K- and protein kinase A-dependent manner. TSH induced the PDK1-dependent phosphorylation of S6K1 but did not induce Akt/protein kinase B phosphorylation. The TSH-induced S6K1 phosphorylation was inhibited by a dominant negative p85alpha regulatory subunit or by the PI3K inhibitors wortmannin and LY294002. Rapamycin inhibited the phosphorylation of S6K1 in the cells treated with either TSH or 8-bromo-cAMP. The stimulating type TSHR antibodies from patients with Graves disease also induced S6K1 activation, whereas the blocking type TSHR antibodies from patients with primary myxedema inhibited TSH- but not the insulin-induced phosphorylation of S6K1. In addition, rapamycin treatment in vivo inhibited the TSH-stimulated thyroid follicle hyperplasia and follicle activity. These findings suggest an interaction between TSHR and PI3K, which is stimulated by TSH and cAMP and might involve the downstream S6K1 but not Akt/protein kinase B. This pathway may play a role in the TSH/stimulating type TSH receptor antibody-mediated thyrocyte proliferation in vitro and in the response to TSH in vivo.
Collapse
MESH Headings
- 8-Bromo Cyclic Adenosine Monophosphate/metabolism
- Androstadienes/pharmacology
- Animals
- Blotting, Western
- Cell Division
- Cells, Cultured
- Chromones/pharmacology
- Dose-Response Relationship, Drug
- Flow Cytometry
- Gene Expression Regulation, Enzymologic
- Humans
- Immunoglobulin G/metabolism
- Immunohistochemistry
- Microscopy, Confocal
- Microscopy, Fluorescence
- Models, Biological
- Morpholines/pharmacology
- Phosphatidylinositol 3-Kinases/biosynthesis
- Phosphatidylinositol 3-Kinases/genetics
- Phosphatidylinositol 3-Kinases/metabolism
- Phosphorylation
- Precipitin Tests
- Protein Binding
- Protein Isoforms
- Protein Kinases/biosynthesis
- Protein Kinases/genetics
- Protein Serine-Threonine Kinases
- Protein Structure, Tertiary
- Proto-Oncogene Proteins/biosynthesis
- Proto-Oncogene Proteins/genetics
- Proto-Oncogene Proteins/metabolism
- Proto-Oncogene Proteins c-akt
- Rats
- Rats, Sprague-Dawley
- Ribosomal Protein S6 Kinases/metabolism
- Ribosomal Protein S6 Kinases, 90-kDa/biosynthesis
- Ribosomal Protein S6 Kinases, 90-kDa/genetics
- Signal Transduction
- Sirolimus/pharmacology
- Spectrometry, Fluorescence
- TOR Serine-Threonine Kinases
- Thymidine/metabolism
- Thyroid Gland/cytology
- Thyroid Gland/metabolism
- Thyrotropin/metabolism
- Time Factors
- Transfection
- Wortmannin
Collapse
Affiliation(s)
- Jae Mi Suh
- Laboratory of Endocrine Cell Biology, Department of Internal Medicine, Chungnam National University School of Medicine, 640 Daesadong Chungku, Taejon 301-040, Korea
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
41
|
Avruch J, Belham C, Weng Q, Hara K, Yonezawa K. The p70 S6 kinase integrates nutrient and growth signals to control translational capacity. PROGRESS IN MOLECULAR AND SUBCELLULAR BIOLOGY 2002; 26:115-54. [PMID: 11575164 DOI: 10.1007/978-3-642-56688-2_5] [Citation(s) in RCA: 136] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- J Avruch
- Diabetes Unit and Medical Services, Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts 02114, USA
| | | | | | | | | |
Collapse
|
42
|
Volarević S, Thomas G. Role of S6 phosphorylation and S6 kinase in cell growth. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 2000; 65:101-27. [PMID: 11008486 DOI: 10.1016/s0079-6603(00)65003-1] [Citation(s) in RCA: 149] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
This article reviews our current knowledge of the role of ribosomal protein S6 phosphorylation and the S6 kinase (S6K) signaling pathway in the regulation of cell growth and proliferation. Although 40S ribosomal protein S6 phosphorylation was first described 25 years ago, it only recently has been implicated in the translational up-regulation of mRNAs coding for the components of protein synthetic apparatus. These mRNAs contain an oligopyrimidine tract at their 5' transcriptional start site, termed a 5'TOP, which has been shown to be essential for their regulation at the translational level. In parallel, a great deal of information has accumulated concerning the identification of the signaling pathway and the regulatory phosphorylation sites involved in controlling S6K activation. Despite this knowledge we are only beginning to identify the direct upstream elements involved in growth factor-induced kinase activation. Use of the immunosupressant rapamycin, a bacterial macrolide, in conjunction with dominant interfering and activated forms of S6K1 has helped to establish the role of this signaling cascade in the regulation of growth and proliferation. In addition, current studies employing the mouse as well as Drosophila melanogaster have provided new insights into physiological function of S6K in the animal. Deletion of the S6K1 gene in mouse cells led to an animal of reduced size and the identification of the S6K1 homolog, S6K2, whereas loss of dS6K function in Drosophila demonstrated its paramount importance in development and growth control.
Collapse
Affiliation(s)
- S Volarević
- Friedrich Miescher Institute, Basel, Switzerland
| | | |
Collapse
|
43
|
Charlton LA, Sayed M, Clark-Lewis I, Aebersold R, Pelech SL. Characterization of an activated ribosomal S6 kinase variant from maturing sea star oocytes: Association with phosphatase 2A and substrate specificity. J Cell Biochem 1999. [DOI: 10.1002/(sici)1097-4644(19991101)75:2<310::aid-jcb13>3.0.co;2-t] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
|
44
|
Schwab MS, Kim SH, Terada N, Edfjäll C, Kozma SC, Thomas G, Maller JL. p70(S6K) controls selective mRNA translation during oocyte maturation and early embryogenesis in Xenopus laevis. Mol Cell Biol 1999; 19:2485-94. [PMID: 10082514 PMCID: PMC84041 DOI: 10.1128/mcb.19.4.2485] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/1998] [Accepted: 12/28/1998] [Indexed: 11/20/2022] Open
Abstract
In mammalian cells, p70(S6K) plays a key role in translational control of cell proliferation in response to growth factors. Because of the reliance on translational control in early vertebrate development, we cloned a Xenopus homolog of p70(S6K) and investigated the activity profile of p70(S6K) during Xenopus oocyte maturation and early embryogenesis. p70(S6K) activity is high in resting oocytes and decreases to background levels upon stimulation of maturation with progesterone. During embryonic development, three peaks of activity were observed: immediately after fertilization, shortly before the midblastula transition, and during gastrulation. Rapamycin, an inhibitor of p70(S6K) activation, caused oocytes to undergo germinal vesicle breakdown earlier than control oocytes, and sensitivity to progesterone was increased. Injection of a rapamycin-insensitive, constitutively active mutant of p70(S6K) reversed the effects of rapamycin. However, increases in S6 phosphorylation were not significantly affected by rapamycin during maturation. mos mRNA, which does not contain a 5'-terminal oligopyrimidine tract (5'-TOP), was translated earlier, and a larger amount of Mos protein was produced in rapamycin-treated oocytes. In fertilized eggs rapamycin treatment increased the translation of the Cdc25A phosphatase, which lacks a 5'-TOP. Translation assays in vivo using both DNA and RNA reporter constructs with the 5'-TOP from elongation factor 2 showed decreased translational activity with rapamycin, whereas constructs without a 5'-TOP or with an internal ribosome entry site were translated more efficiently upon rapamycin treatment. These results suggest that changes in p70(S6K) activity during oocyte maturation and early embryogenesis selectively alter the translational capacity available for mRNAs lacking a 5'-TOP region.
Collapse
Affiliation(s)
- M S Schwab
- Howard Hughes Medical Institute and Department of Pharmacology, University of Colorado School of Medicine, Denver, Colorado 80262, USA
| | | | | | | | | | | | | |
Collapse
|
45
|
Iiboshi Y, Papst PJ, Kawasome H, Hosoi H, Abraham RT, Houghton PJ, Terada N. Amino acid-dependent control of p70(s6k). Involvement of tRNA aminoacylation in the regulation. J Biol Chem 1999; 274:1092-9. [PMID: 9873056 DOI: 10.1074/jbc.274.2.1092] [Citation(s) in RCA: 176] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In human T-lymphoblastoid cells, downstream signaling events of mammalian target of rapamycin (mTOR), including the activity of p70(s6k) and phosphorylation of eukaryotic initiation factor 4E-binding protein 1, were dependent on amino acid concentration in the culture media, whereas other growth-related protein kinases were not. Amino acid-induced p70(s6k) activation was completely inhibited by rapamycin but only partially inhibited by wortmannin. Moreover, amino acid concentration similarly affected the p70(s6k) activity, which was dependent on a rapamycin-resistant mutant (S2035I) of mTOR. These data indicate that mTOR is required for amino acid-dependent activation of p70(s6k). The mechanism by which amino acids regulate p70(s6k) activity was further explored: 1) amino acid alcohols, which inhibit aminoacylation of tRNA by their competitive binding to tRNA synthetases, suppressed p70(s6k) activity; 2) suppression of p70(s6k) by amino acid depletion was blocked by cycloheximide or puromycin, which inhibit utilization of aminoacylated tRNA in cells; and 3) in cells having a temperature-sensitive mutant of histidyl tRNA synthetase, p70(s6k) was suppressed by a transition of cells to a nonpermissible temperature, which was partially restored by addition of high concentrations of histidine. These results indicate that suppression of tRNA aminoacylation is able to inhibit p70(s6k) activity. Deacylated tRNA may be a factor negatively regulating p70(s6k).
Collapse
Affiliation(s)
- Y Iiboshi
- Department of Pediatrics, Division of Basic Sciences, National Jewish Medical and Research Center, Denver, Colorado 80206, USA
| | | | | | | | | | | | | |
Collapse
|
46
|
Gonzalez-Aseguinolaza G, Taladriz S, Marquet A, Larraga V. Cloning and structural analysis of the gene encoding the ribosomal protein S6 from the parasite Leishmania infantum. Biochem Biophys Res Commun 1998; 248:464-8. [PMID: 9703947 DOI: 10.1006/bbrc.1998.8927] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have cloned the S6 ribosomal protein encoding gene from a Leishmania infantum cDNA library. This parasite protozoon, responsible for leishmaniasis in Europe, is able to undergo developmental changes in vitro and results a good model to study cell differentiation processes. The LiS6 protein sequence indicates its pertinence to the S6 protein family, related to the early mechanisms of cell division, differentiation and activation, and shows an intermediate position between the yeasts and higher eukaryotes. Thus, LiS6 protein has the same amino acid length as that of the higher eukaryotes and certain common features such nucleus entrance sequences and several kinase phosphorylation sites. However, the key functional protein kinase C phosphorylation sites are at different locations and present several threonine instead of the usual serine residues. The gene structural analysis suggest the presence of three different encoding genes that do not present remarkable changes along the different phases of the parasite.
Collapse
|
47
|
Papst PJ, Sugiyama H, Nagasawa M, Lucas JJ, Maller JL, Terada N. Cdc2-cyclin B phosphorylates p70 S6 kinase on Ser411 at mitosis. J Biol Chem 1998; 273:15077-84. [PMID: 9614117 DOI: 10.1074/jbc.273.24.15077] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The carboxyl terminus of p70 S6 kinase (p70(s6k)) has a set of Ser and Thr residues (Ser411, Ser418, Ser424, and Thr421) phosphorylated in vivo by an unidentified kinase(s). These Ser/Thr sites are immediately followed by proline, a motif that is commonly seen in the substrates of cyclin-dependent kinases (Cdk) and mitogen-activated protein kinases. A previous study has shown that Cdc2 (Cdk1) indeed phosphorylates these p70(s6k) Ser/Thr residues in vitro. Here, we demonstrate that Cdc2-cyclin B complex phosphorylates Ser411 in the KIRSPRR sequence, whereas other Cdk-cyclin complexes including those containing Cdk2, Cdk4, or Cdk6 do not. Additionally, Ser411 phosphorylation in vivo was increased at mitosis in parallel with Cdc2 activation, and it was suppressed by a dominant negative form of Cdc2. These data indicate that p70(s6k) is a physiological substrate of Cdc2-cyclin B in mitosis. Since the activity of p70(s6k) is low during mitosis, Cdc2-cyclin B may play a role in inactivating p70(s6k) during mitosis, where protein synthesis is suppressed.
Collapse
Affiliation(s)
- P J Papst
- Division of Basic Sciences, Department of Pediatrics, National Jewish Medical and Research Center, Denver, Colorado 80206, USA
| | | | | | | | | | | |
Collapse
|
48
|
Gilbert LI, Song Q, Rybczynski R. Control of ecdysteroidogenesis: activation and inhibition of prothoracic gland activity. INVERTEBRATE NEUROSCIENCE : IN 1997; 3:205-16. [PMID: 9783446 DOI: 10.1007/bf02480376] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The ecdysteroid hormones, mainly 20-hydroxyecdysone (20E), play a pivotal role in insect development by controlling gene expression involved in molting and metamorphosis. In the model insect Manduca sexta the production of ecdysteroids by the prothoracic gland is acutely controlled by a brain neurohormone, prothoracicotropic hormone (PTTH). PTTH initiates a cascade of events that progresses from the influx of Ca2+ and cAMP generation through phosphorylation of the ribosomal protein S6 and S6-dependent protein synthesis, and concludes with an increase in the synthesis and export of ecdysteroids from the gland. Recent studies indicate that S6 phosphorylation probably controls the steroidogenic effect of PTTH by gating the translation of selected mRNAs whose protein products are required for increased ecdysteroid synthesis. Inhibition of S6 phosphorylation prevents an increase in PTTH-stimulated protein synthesis and subsequent ecdysteroid synthesis. Two of the proteins whose translations are specifically stimulated by PTTH have been identified, one being a beta tubulin and the other a heat shock protein 70 family member. Current data suggest that these two proteins could be involved in supporting microtubule-dependent protein synthesis and ecdysone receptor assembly and/or function. Recent data also indicate that the 20E produced by the prothoracic gland feeds back upon the gland by increasing expression and phosphorylation of a specific USP isoform that is a constituent of the functional ecdysone receptor. Changes in the concentration and composition of the ecdysone receptor complex of the prothoracic gland could modulate the gland's potential for ecdysteroid synthesis (e.g. feedback inhibition) by controlling the levels of enzymes or other proteins in the ecdysteroid biosynthetic pathway.
Collapse
Affiliation(s)
- L I Gilbert
- Department of Biology, University of North Carolina at Chapel Hill 27599-3280, USA.
| | | | | |
Collapse
|
49
|
Song Q, Gilbert LI. Molecular cloning, developmental expression, and phosphorylation of ribosomal protein S6 in the endocrine gland responsible for insect molting. J Biol Chem 1997; 272:4429-35. [PMID: 9020166 DOI: 10.1074/jbc.272.7.4429] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Phosphorylation of ribosomal protein S6 is requisite for prothoracicotropic hormone (PTTH)-stimulated specific protein synthesis and subsequent ecdysteroidogenesis in the prothoracic glands of the tobacco hornworm, Manduca sexta. To better understand the role of S6 in regulating ecdysteroidogenesis, S6 cDNA was isolated from a Manduca prothoracic gland cDNA library and sequenced. The deduced protein is comprised of 253 amino acids, has a molecular weight of 29,038, and contains four copies of a 10-amino acid motif defining potential DNA-binding sites. This Manduca S6 possesses a consensus recognition sequence for the p70(s6k) binding domain as well as six seryl residues at the carboxyl-terminal sequence of 17 amino acids. Phosphoamino acid analysis revealed that the phosphorylation of Manduca prothoracic gland S6 is limited exclusively to serine residues. Although alterations in the quantity of S6 mRNA throughout the last larval instar and early pupal-adult development were not well correlated with the hemolymph ecdysteroid titer, developmental expression and phosphorylation of S6 were temporally correlated with PTTH release and the hemolymph ecdysteroid titer. These data provide additional evidence that S6 phosphorylation is a critical element in the transduction pathway leading to PTTH-stimulated ecdysteroidogenesis.
Collapse
Affiliation(s)
- Q Song
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina 27599-3280, USA
| | | |
Collapse
|
50
|
|