251
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Goto M, Iwase A, Ando H, Kurotsuchi S, Harata T, Kikkawa F. PTEN and Akt expression during growth of human ovarian follicles. J Assist Reprod Genet 2007; 24:541-6. [PMID: 17999178 DOI: 10.1007/s10815-007-9156-3] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2007] [Accepted: 05/31/2007] [Indexed: 11/27/2022] Open
Abstract
PURPOSE To assess the expression of PTEN and total and phosphorylated Akt in human ovarian follicles during follicular growth. METHODS Immunohistochemistry of ovarian tissues and Western blotting and immunofluorescence of primary cultured luteinized granulosa cells for PTEN and Akt. RESULTS Immunoreactivity of Akt was found in the oocytes, granulosa cells and theca cells in primordial follicles, follicles at each growing stage and luteal cells. As the follicles grew, staining for PTEN became intense in the granulosa cells, whereas the intensity of phospho-Akt became weak. Western blotting and immunofluorescence analysis using primary cultured granulosa-lutein cells showed Akt and PTEN expression, and phosphorylation of Akt in vitro. CONCLUSIONS PTEN and Akt are present in the granulosa cells during folliculogenesis. An increase in PTEN may lead to changes in proliferation and/or differentiation of granulosa cells during follicular growth via regulation of Akt phosphorylation.
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Affiliation(s)
- Maki Goto
- Department of Obstetrics and Gynecology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, Japan
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252
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Abstract
Forkhead box (Fox) proteins are a superfamily of evolutionarily conserved transcriptional regulators, which control a wide spectrum of biological processes. As a consequence, a loss or gain of Fox function can alter cell fate and promote tumorigenesis as well as cancer progression. Here we discuss the evidence that the deregulation of Fox family transcription factors has a crucial role in the development and progression of cancer, and evaluate the emerging role of Fox proteins as direct and indirect targets for therapeutic intervention, as well as biomarkers for predicting and monitoring treatment responses.
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Affiliation(s)
- Stephen S Myatt
- Cancer Research UK laboratories, Department of Oncology, MRC Cyclotron Building, Imperial College London, Hammersmith Hospital Campus, Du Cane Road, London W12 0NN, UK
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253
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Engelbrecht AM, Mattheyse M, Ellis B, Loos B, Thomas M, Smith R, Peters S, Smith C, Myburgh K. Proanthocyanidin from grape seeds inactivates the PI3-kinase/PKB pathway and induces apoptosis in a colon cancer cell line. Cancer Lett 2007; 258:144-53. [PMID: 17923279 DOI: 10.1016/j.canlet.2007.08.020] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2007] [Revised: 08/22/2007] [Accepted: 08/31/2007] [Indexed: 01/06/2023]
Abstract
The aim of this investigation was to evaluate the chemopreventative/antiproliferative potential of a grape seed proanthocyanidin extract (GSPE) against colon cancer cells (CaCo2 cells) and to investigate its mechanism of action. GSPE (10-100 microg/ml) significantly inhibited cell viability and increased apoptosis in CaCo2 cells, but did not alter viability in the normal colon cell line (NCM460). The increased apoptosis observed in GSPE-treated CaCo2 cells correlated with an attenuation of PI3-kinase (p110 and p85 subunits) and decreased PKB Ser(473) phosphorylation. GSPE might thus exert its beneficial effects by means of increased apoptosis and suppression of the important PI3-kinase survival-related pathway.
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Affiliation(s)
- A-M Engelbrecht
- Department of Physiological Sciences, Stellenbosch University, Stellenbosch, South Africa.
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254
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Abstract
The tumor suppressor phosphatase and tensin homolog (PTEN) functions as a phosphoinositide 3-phosphatase, that antagonizes phosphatidylinositol 3-kinase action, and negatively regulates cell proliferation and survival signals. Inactivation of PTEN by loss-of-function mutations gives rise to deregulated hyperproliferation of cells, leading to oncogenic transformation. Recent studies have identified a number of upstream regulatory factors for PTEN and unveiled that the impairment in the PTEN regulatory system potentially becomes a causal factor for oncogenic transformation of cells. This article will review the PTEN inactivation mechanism which is linked to human tumorigenesis, particularly focusing on recent research progress in PTEN regulators.
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Affiliation(s)
- Tomohiko Maehama
- Department of Biochemistry and Cell Biology, National Institute of Infectious Diseases, Shinjuku-ku, Tokyo 162-8640, Japan.
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255
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Pérez-Tenorio G, Alkhori L, Olsson B, Waltersson MA, Nordenskjöld B, Rutqvist LE, Skoog L, Stål O. PIK3CA mutations and PTEN loss correlate with similar prognostic factors and are not mutually exclusive in breast cancer. Clin Cancer Res 2007; 13:3577-84. [PMID: 17575221 DOI: 10.1158/1078-0432.ccr-06-1609] [Citation(s) in RCA: 235] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
PURPOSE The phosphatidylinositol 3'-kinase/Akt pathway is frequently altered in breast cancer. PTEN, a phosphatase that opposes the effect of phosphatidylinositol 3'-kinase, can be mutated or lost, whereas the PIK3CA gene is mutated. These have been proposed as alternative mechanisms, and their clinicalpathology significance is under discussion. In this study, we aimed to explore whether PIK3CA mutations and PTEN loss are mutually exclusive mechanisms, correlate with other known clinicopathologic markers, or have clinical implication in breast cancer. EXPERIMENTAL DESIGN Exons 9 and 20 of the PIK3CA gene were analyzed in 270 breast tumors, and mutations were detected by single-stranded conformational analysis followed by sequencing. The expression of PTEN was evaluated by immunohistochemistry in 201 tumors. RESULTS PIK3CA mutations were found in 24% of the tumors and associated with estrogen receptor(+) status, small size, negative HER2 status, high Akt1, and high cyclin D1 protein expression. PTEN was negative in 37% of the cases and PTEN loss was associated with PIK3CA mutations (P = 0.0024). Tumors presenting PTEN loss or both alterations were often estrogen receptor(+), small in size, and HER2(-). PIK3CA mutations predicted for longer local recurrence-free survival. Moreover, PTEN loss by itself or combined with mutated PIK3CA tended to confer radiosensitivity. In addition, the patients with high S-phase fraction had longer recurrence-free survival if they carried mutations in the PIK3CA gene and/or had lost PTEN, whereas the same alterations were associated with shorter recurrence-free survival among patients with low S-phase fraction. CONCLUSIONS PIK3CA mutations and PTEN loss were not mutually exclusive events and associated with similar prognostic factors.
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Affiliation(s)
- Gizeh Pérez-Tenorio
- Department of Biomedicine and Surgery, Division of Oncology, Faculty of Health Sciences, Linköping University, Linköping, Sweden.
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256
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Zhang J, Liu Z, Rasschaert J, Blero D, Deneubourg L, Schurmans S, Erneux C, Pesesse X. SHIP2 controls PtdIns(3,4,5)P3 levels and PKB activity in response to oxidative stress. Cell Signal 2007; 19:2194-200. [PMID: 17643961 DOI: 10.1016/j.cellsig.2007.06.022] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2007] [Accepted: 06/21/2007] [Indexed: 01/01/2023]
Abstract
Reactive oxygen species (ROS) are known to be involved in redox signalling pathways that may contribute to normal cell function as well as disease progression. The tumour suppressor PTEN and the inositol 5-phosphatase SHIP2 are critical enzymes in the control of PtdIns(3,4,5)P(3) level. It has been reported that oxidants, including those produced in cells such as macrophages, can activate downstream signalling via the inactivation of PTEN. The present study evaluates the potential impact of SHIP2 on phosphoinositides in cells exposed to sodium peroxide. We used a model of SHIP2 deficient mouse embryonic fibroblasts (MEFs) stimulated by H(2)O(2): at 15 min, PtdIns(3,4,5)P(3) was markedly increased in SHIP2 -/- cells as compared to +/+ cells. In contrast, no significant increase in PtdIns(3,4)P(2) could be detected at 15 or 120 min incubation of the cells with H(2)O(2) (0.6 mM). PKB activity was also upregulated in SHIP2 -/- cells as compared to +/+ cells in response to H(2)O(2). SHIP2 add back experiments in SHIP2 -/- cells confirm its critical role as a lipid phosphatase in the control of PtdIns(3,4,5)P(3) level in response to H(2)O(2). We conclude that SHIP2 lipid phosphatase activity plays an important role in the metabolism PtdIns(3,4,5)P(3) which is demonstrated in oxygen stressed cells.
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Affiliation(s)
- Jing Zhang
- Institut de Recherche Interdisciplinaire (IRIBHM), Université Libre de Bruxelles, Campus Erasme, 808 Route de Lennik, 1070 Brussels, Belgium
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257
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Leary A, Johnston SRD. Small molecule signal transduction inhibitors for the treatment of solid tumors. Cancer Invest 2007; 25:347-65. [PMID: 17661211 DOI: 10.1080/07357900701259694] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
A greater understanding of the pathogenesis of malignancy has led to the development of novel therapies designed to target aberrant molecular pathways that characterize and distinguish cancer cells from normal tissue. Small molecules are being designed to interfere with specific steps along the deregulated signaling cascade from the cytoplasmic membrane to the nucleus. Viable targets include growth factor receptors and their downstream second messengers, modulators of the cell cycle or apoptosis, regulators of protein trafficking and degradation, and transcription regulators. This review will discuss the small molecule signal transduction inhibitors in various stages of development and address the strategic issues relating to clinical trial design with these novel targeted agents.
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258
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Prasad NK, Tandon M, Badve S, Snyder PW, Nakshatri H. Phosphoinositol phosphatase SHIP2 promotes cancer development and metastasis coupled with alterations in EGF receptor turnover. Carcinogenesis 2007; 29:25-34. [PMID: 17893231 DOI: 10.1093/carcin/bgm213] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Phosphoinositol phosphatases are important regulators of signaling pathways relevant to both diabetes and cancer. A 3'-phosphoinositol phosphatase, phosphatase homologous to tensin (PTEN), is both a tumor suppressor and a negative regulator of insulin action. A 5'-phosphoinositol phosphatase, SH2-containing 5'-inositol phosphatase (SHIP2), regulates insulin signaling and its genetic knockout prevents high-fat diet-induced obesity in mice. SHIP2 also regulates cytoskeleton remodeling and receptor endocytosis. This and the fact that both PTEN and SHIP2 act on the same substrate suggest a potential role for SHIP2 in cancer. Here we report that, in direct contrast to PTEN, SHIP2 protein expression is elevated in a number of breast cancer cell lines. RNA interference-mediated silencing of SHIP2 in MDA-231 cells suppresses epidermal growth factor receptor (EGFR) levels by means of enhanced receptor degradation. Furthermore, endogenous SHIP2 in MDA-231 breast cancer cells supports in vitro cell proliferation, increases cellular sensitivity to drugs targeting the EGFR and supports cancer development and metastasis in nude mice. In addition, significantly high proportions (44%; P = 0.0001) of clinical specimens of breast cancer tissues in comparison with non-cancerous breast tissues contain elevated expression of SHIP2 protein. Taken together, our results demonstrate that SHIP2 is a clinically relevant novel anticancer target that links perturbed metabolism to cancer development.
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Affiliation(s)
- Nagendra K Prasad
- Department of Basic Medical Sciences and Purdue Cancer Center, Purdue University, LYNN Hall, 625 Harrison Street, West Lafayette, IN 47907, USA
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259
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Mandl A, Sarkes D, Carricaburu V, Jung V, Rameh L. Serum withdrawal-induced accumulation of phosphoinositide 3-kinase lipids in differentiating 3T3-L6 myoblasts: distinct roles for Ship2 and PTEN. Mol Cell Biol 2007; 27:8098-112. [PMID: 17893321 PMCID: PMC2169165 DOI: 10.1128/mcb.00756-07] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Phosphoinositide 3-kinase (PI3K) activation and synthesis of phosphatidylinositol-3,4-bisphosphate (PI-3,4-P2) and phosphatidylinositol-3,4,5-trisphosphate (PI-3,4,5-P3) lipids mediate growth factor signaling that leads to cell proliferation, migration, and survival. PI3K-dependent activation of Akt is critical for myoblast differentiation induced by serum withdrawal, suggesting that in these cells PI3K signaling is activated in an unconventional manner. Here we investigate the mechanisms by which PI3K signaling and Akt are regulated during myogenesis. We report that PI-3,4-P2 and PI-3,4,5-P3 accumulated in the plasma membranes of serum-starved 3T3-L6 myoblasts due to de novo synthesis and increased lipid stability. Surprisingly, only newly synthesized lipids were capable of activating Akt. Knockdown of the lipid phosphatase PTEN moderately increased PI3K lipids but significantly increased Akt phosphorylation and promoted myoblast differentiation. Knockdown of the lipid phosphatase Ship2, on the other hand, dramatically increased the steady-state levels of PI-3,4,5-P3 but did not affect Akt phosphorylation and increased apoptotic cell death. Together, these results reveal the existence of two distinct pools of PI3K lipids in differentiating 3T3-L6 myoblasts: a pool of nascent lipids that is mainly dephosphorylated by PTEN and is capable of activating Akt and promoting myoblast differentiation and a stable pool that is dephosphorylated by Ship2 and is unable to activate Akt.
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Affiliation(s)
- Adel Mandl
- Boston Biomedical Research Institute, 64 Grove Street, Watertown, MA 02472, USA
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260
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Choi DS, Kim JH, Ryu HS, Kim HC, Han JH, Lee JS, Min CK. Syndecan-1, a key regulator of cell viability in endometrial cancer. Int J Cancer 2007; 121:741-50. [PMID: 17455248 DOI: 10.1002/ijc.22713] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Syndecan-1 is one of the major proteoglycans on cell surfaces involved in major biological processes. Although loss of syndecan-1 correlates well with the gain of cancerous characteristics in a wide range of cancers, increased expression of syndecan-1 also coincides with adverse outcomes in some cancers, including breast, ovarian and pancreatic cancers. For this Janus-faced attitude of syndecan-1, we sought to examine expression patterns of syndecan-1 in endometrial carcinoma (EC) and gain insight into the roles of syndecan-1. Immunohistochemical examinations of 109 endometrial tissue samples from myoma, hyperplasia and EC uteri revealed that syndecan-1 expression was significantly upregulated in EC compared with hyperplasia (p < 0.001). To evaluate pathophysiological functions of syndecan-1, its expression level was altered, and subsequent outcomes were examined using human endometrial cancer cell lines such as HEC-1A, AN3CA and KLE cells. Overexpression of syndecan-1 increased the growth of HEC-1A cells regardless of anchorage dependence while silencing syndecan-1 by antisense RNAs caused apoptotic cell death. Consistent with decreased viability, the loss of syndecan-1 was also accompanied by a decrease in the activation of Erk and Akt and a concomitant decrease in the phosphorylation of PTEN and PDK1, which are known as negative and positive regulators of Akt activation, respectively. These down-regulatory effects were reversed upon overexpression of syndecan-1. Collectively together, the aforementioned findings lend support to the notion that upregulation of syndecan-1 may be a critical element for endometrial cancers in maintaining their viability and thus can serve as a cancer specific therapeutic and diagnostic marker.
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Affiliation(s)
- Dong Soon Choi
- Department of Molecular Science and Technology, Ajou University, Suwon, South Korea
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261
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Carver DJ, Gaston B, Deronde K, Palmer LA. Akt-mediated activation of HIF-1 in pulmonary vascular endothelial cells by S-nitrosoglutathione. Am J Respir Cell Mol Biol 2007; 37:255-63. [PMID: 17541013 PMCID: PMC1994227 DOI: 10.1165/rcmb.2006-0289sm] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2006] [Accepted: 05/04/2007] [Indexed: 12/19/2022] Open
Abstract
S-nitrosoglutathione (GSNO) stabilizes the alpha-subunit of hypoxia inducible factor-1 (HIF-1) in normoxic cells, but not in the presence of PI3K inhibitors. In this report, the biochemical pathway by which GSNO alters PI3K/Akt activity to modify HIF-1 expression was characterized in Cos cells and primary pulmonary vascular endothelial cells. GSNO increased Akt kinase activity--and downstream HIF-1alpha protein accumulation and DNA-binding activity--in a dose- and time-dependent manner. The PI3K inhibitors, wortmannin and LY294002, blocked these responses. Neither glutathione nor 8-bromo-cyclic GMP mimicked the GSNO-induced increases in Akt kinase activity. GSNO-induced Akt kinase activity and downstream HIF-1alpha stabilization were blocked by acivicin, an inhibitor of gamma-glutamyl transpeptidase (gammaGT), a transmembrane protein that can translate extracellular GSNO to intracellular S-nitrosocysteinylglycine. Dithiothreitol blocked GSNO-induced Akt kinase activity and HIF-1alpha stabilization. Moreover, the 3'-phosphatase of phosphoinositides, PTEN (phosphatase and tensin homolog deleted on chromosome ten) was S-nitrosylated by GSNO in pulmonary arterial endothelial cells, which was reversed by dithiothreitol and ultraviolet light. Interestingly, the abundance of S-nitrosylated PTEN also correlated inversely with PTEN activity. Taken together, these results suggest that GSNO induction of Akt appears to be mediated by S-nitrosylation chemistry rather than classic NO signaling through guanylate cyclase/cGMP. We speculate that gammaGT-dependent activation of Akt and subsequent activation of HIF-1 in vascular beds may be relevant to the regulation of HIF-1-dependent gene expression in conditions associated with oxyhemoglobin deoxygenation, as opposed to profoundly low Po(2), in the pulmonary vasculature.
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Affiliation(s)
- D Jeannean Carver
- Department of Pediatrics, Divisions of Critical Care and Respiratory Medicine, University of Virginia School of Medicine, P.O. Box 801366, Charlottesville, VA 22908, USA
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262
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Abraham RT, Gibbons JJ. The mammalian target of rapamycin signaling pathway: twists and turns in the road to cancer therapy. Clin Cancer Res 2007; 13:3109-14. [PMID: 17545512 DOI: 10.1158/1078-0432.ccr-06-2798] [Citation(s) in RCA: 196] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The immunosuppressive drug rapamycin played a key role in the functional characterization of mammalian target of rapamycin (mTOR), an unusual protein kinase that coordinates growth factor and nutrient availability with cell growth and proliferation. Several rapamycin-related compounds are now in various stages of clinical development as anticancer agents. This article highlights recent advances in our understanding of the mTOR signaling pathway and the implications of these findings for the clinical application of mTOR inhibitors in cancer patients.
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Affiliation(s)
- Robert T Abraham
- Department of Oncology Discovery, Wyeth, Pearl River, New York 10960, USA.
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263
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Maccario H, Perera N, Davidson L, Downes C, Leslie N. PTEN is destabilized by phosphorylation on Thr366. Biochem J 2007; 405:439-44. [PMID: 17444818 PMCID: PMC2267318 DOI: 10.1042/bj20061837] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Although PTEN (phosphatase and tensin homologue deleted on chromosome 10) is one of the most commonly mutated tumour suppressors in human cancers, loss of PTEN expression in the absence of mutation appears to occur in an even greater number of tumours. PTEN is phosphorylated in vitro on Thr366 and Ser370 by GSK3 (glycogen synthase kinase 3) and CK2 (casein kinase 2) respectively, and specific inhibitors of these kinases block these phosphorylation events in cultured cells. Although mutation of these phosphorylation sites did not alter the phosphatase activity of PTEN in vitro or in cells, blocking phosphorylation of Thr366 by either mutation or GSK3 inhibition in glioblastoma cell lines led to a stabilization of the PTEN protein. Our data support a model in which the phosphorylation of Thr366 plays a role in destabilizing the PTEN protein.
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Affiliation(s)
- Helene Maccario
- Division of Molecular Physiology, School of Life Sciences, University of Dundee, Dundee DD1 5EH, U.K
| | - Nevin M. Perera
- Division of Molecular Physiology, School of Life Sciences, University of Dundee, Dundee DD1 5EH, U.K
| | - Lindsay Davidson
- Division of Molecular Physiology, School of Life Sciences, University of Dundee, Dundee DD1 5EH, U.K
| | - C. Peter Downes
- Division of Molecular Physiology, School of Life Sciences, University of Dundee, Dundee DD1 5EH, U.K
| | - Nick R. Leslie
- Division of Molecular Physiology, School of Life Sciences, University of Dundee, Dundee DD1 5EH, U.K
- To whom correspondence should be addressed (email )
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264
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Odriozola L, Singh G, Hoang T, Chan AM. Regulation of PTEN Activity by Its Carboxyl-terminal Autoinhibitory Domain. J Biol Chem 2007; 282:23306-15. [PMID: 17565999 DOI: 10.1074/jbc.m611240200] [Citation(s) in RCA: 137] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The regulation of PTEN intrinsic biochemical properties has not been fully elucidated. In this report, we investigated the role of the PTEN carboxyl-terminal tail domain in regulating its membrane targeting and catalytic functions. Characterization of a panel of PTEN phosphorylation site mutants revealed that mutating Ser-385 to alanine (S385A) promoted membrane localization in vivo and phosphatase activity in vitro. Furthermore, S385A mutation was associated with a substantial reduction in the phosphorylation of the Ser-380/Thr-382/Thr-383 cluster. Therefore, Ser-385 could prime additional dephosphorylation events to regulate PTEN catalytic activity. Moreover, substituting Ser-380/Thr-382/Thr-383 to phosphomimic residues reversed the phosphatase activity of the S385A mutation. Next, we further defined the underlying mechanisms responsible for the COOH-terminal tail region in modulating PTEN biological activity. We have identified an interaction between the 71-amino acid carboxyl-terminal tail region and the CBRIII motif of the C2 domain, which has been implicated in membrane binding. In addition, a synthetic phosphomimic peptide encompassing the phosphorylation site cluster between amino acids 368 and 390 within the tail region mediated the suppression of PTEN catalytic activity in vitro. This same peptide when expressed in cultured cells also impeded PTEN membrane localization and enhanced phospho-Akt levels. Thus, our data suggest that the COOH-terminal tail can act as an autoinhibitory domain to control both PTEN membrane recruitment and phosphatase activity.
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Affiliation(s)
- Leticia Odriozola
- Department of Oncological Sciences, Mount Sinai School of Medicine, New York, New York, 10029, USA
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265
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Davis AR, Lotocki G, Marcillo AE, Dietrich WD, Keane RW. FasL, Fas, and death-inducing signaling complex (DISC) proteins are recruited to membrane rafts after spinal cord injury. J Neurotrauma 2007; 24:823-34. [PMID: 17518537 DOI: 10.1089/neu.2006.0227] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The Fas/CD95 receptor-ligand system plays an essential role in apoptosis that contributes to secondary damage after spinal cord injury (SCI), but the mechanism regulating the efficiency of FasL/Fas signaling in the central nervous system (CNS) is unknown. Here, FasL/Fas signaling complexes in membrane rafts were investigated in the spinal cord of adult female Fischer rats subjected to moderate cervical SCI and sham operation controls. In sham-operated animals, a portion of FasL, but not Fas was present in membrane rafts. SCI resulted in FasL and Fas translocation into membrane raft microdomains where Fas associates with the adaptor proteins Fas-associated death domain (FADD), caspase-8, cellular FLIP long form (cFLIPL ), and caspase-3, forming a death-inducing signaling complex (DISC). Moreover, SCI induced expression of Fas in clusters around the nucleus in both neurons and astrocytes. The formation of the DISC signaling platform leads to rapid activation of initiator caspase-8 and effector caspase-3, and the modification of signaling intermediates such as FADD and cFLIP(L) . Thus, FasL/Fas-mediated signaling after SCI is similar to Fas expressing Type I cell apoptosis.
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Affiliation(s)
- Angela R Davis
- Department of Physiology and Biophysics, University of Miami Miller School of Medicine, Miami, Florida 33136, USA
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266
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Leslie NR, Yang X, Downes CP, Weijer CJ. PtdIns(3,4,5)P(3)-dependent and -independent roles for PTEN in the control of cell migration. Curr Biol 2007; 17:115-25. [PMID: 17240336 PMCID: PMC1885949 DOI: 10.1016/j.cub.2006.12.026] [Citation(s) in RCA: 144] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2006] [Revised: 12/01/2006] [Accepted: 12/01/2006] [Indexed: 11/26/2022]
Abstract
BACKGROUND Phosphatase and tensin homolog (PTEN) mediates many of its effects on proliferation, growth, survival, and migration through its PtdIns(3,4,5)P(3) lipid phosphatase activity, suppressing phosphoinositide 3-kinase (PI3K)-dependent signaling pathways. PTEN also possesses a protein phosphatase activity, the role of which is less well characterized. RESULTS We have investigated the role of PTEN in the control of cell migration of mesoderm cells ingressing through the primitive streak in the chick embryo. Overexpression of PTEN strongly inhibits the epithelial-to-mesenchymal transition (EMT) of mesoderm cells ingressing through the anterior and middle primitive streak, but it does not affect EMT of cells located in the posterior streak. The inhibitory activity on EMT is completely dependent on targeting PTEN through its C-terminal PDZ binding site, but can be achieved by a PTEN mutant (PTEN G129E) with only protein phosphatase activity. Expression either of PTEN lacking the PDZ binding site or of the PTEN C2 domain, or inhibition of PI3K through specific inhibitors, does not inhibit EMT, but results in a loss of both cell polarity and directional migration of mesoderm cells. The PTEN-related protein TPTE, which normally lacks any detectable lipid and protein phosphatase activity, can be reactivated through mutation, and only this reactivated mutant leads to nondirectional migration of these cells in vivo. CONCLUSIONS PTEN modulates cell migration of mesoderm cells in the chick embryo through at least two distinct mechanisms: controlling EMT, which involves its protein phosphatase activity; and controlling the directional motility of mesoderm cells, through its lipid phosphatase activity.
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Affiliation(s)
- Nick R Leslie
- Division of Molecular Physiology, University of Dundee, Dundee, DD1 5EH, Scotland, United Kingdom.
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267
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Ross SH, Lindsay Y, Safrany ST, Lorenzo O, Villa F, Toth R, Clague MJ, Downes CP, Leslie NR. Differential redox regulation within the PTP superfamily. Cell Signal 2007; 19:1521-30. [PMID: 17346927 DOI: 10.1016/j.cellsig.2007.01.026] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2007] [Revised: 01/26/2007] [Accepted: 01/26/2007] [Indexed: 11/18/2022]
Abstract
The Protein Tyrosine Phosphatase (PTP) family comprises a large and diverse group of enzymes, regulating a range of biological processes through de-phosphorylation of many proteins and lipids. These enzymes share a catalytic mechanism that requires a reduced and reactive cysteine nucleophile, making them potentially sensitive to inactivation and regulation by oxidation. Analysis of ten PTPs identified substantial differences in the sensitivity of these enzymes to oxidation in vitro. More detailed experiments confirmed the following rank order of sensitivity: PTEN and Sac1>PTPL1/FAP-1>>myotubularins. When the apparent sensitivity to oxidation of these PTPs in cells treated with hydrogen peroxide was analysed, this correlated well with the observed sensitivities to oxidation in vitro. These data suggested that different PTPs may fall into at least three different classes with respect to mechanisms of cellular redox regulation. 1. PTEN and Sac1 were readily and reversibly oxidised in vitro and in cells treated with hydrogen peroxide 2. PTPL1 appeared to be resistant to oxidation in cells, correlating with its sensitivity to reduction by glutathione in vitro 3. The myotubularin family of lipid phosphatases was almost completely resistant to oxidation in vitro and in cells. Our results show that sensitivity to reversible oxidation is not a necessary characteristic of the PTPs and imply that such sensitivity has evolved as a regulatory mechanism for some of this large family, but not others.
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Affiliation(s)
- Sarah H Ross
- Division of Molecular Physiology, College of Life Sciences, University of Dundee, Dundee, UK
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268
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Blero D, Payrastre B, Schurmans S, Erneux C. Phosphoinositide phosphatases in a network of signalling reactions. Pflugers Arch 2007; 455:31-44. [PMID: 17605038 DOI: 10.1007/s00424-007-0304-5] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2007] [Revised: 05/18/2007] [Accepted: 05/29/2007] [Indexed: 12/18/2022]
Abstract
Phosphoinositide phosphatases dephosphorylate the three positions (D-3, 4 and 5) of the inositol ring of the poly-phosphoinositides. They belong to different families of enzymes. The PtdIns(3,4)P(2) 4-phosphatase family, the tumour suppressor phosphatase and tensin homolog deleted on chromosome 10 (PTEN), SAC1 domain phosphatases and myotubularins belong to the tyrosine protein phosphatases superfamily. They share the presence of a conserved cysteine residue in the consensus CX(5)RT/S. Another family consists of the inositol polyphosphate 5-phosphatase isoenzymes. The importance of these phosphoinositide phosphatases in cell regulation is illustrated by multiple examples of their implications in human diseases such as Lowe syndrome, X-linked myotubular myopathy, cancer, diabetes or bacterial infection.
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Affiliation(s)
- Daniel Blero
- Interdisciplinary Research Institute (IRIBHM), Université Libre de Bruxelles, Campus Erasme, Bldg C, 808 Route de Lennik, 1070, Brussels, Belgium
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269
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Papakonstanti EA, Ridley AJ, Vanhaesebroeck B. The p110delta isoform of PI 3-kinase negatively controls RhoA and PTEN. EMBO J 2007; 26:3050-61. [PMID: 17581634 PMCID: PMC1914109 DOI: 10.1038/sj.emboj.7601763] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2007] [Accepted: 05/23/2007] [Indexed: 01/22/2023] Open
Abstract
Inactivation of PI 3-kinase (PI3K) signalling is critical for tumour suppression by PTEN. This is thought to be a unidirectional relationship in which PTEN degrades the lipids produced by PI3K, thus controlling cell proliferation, survival and migration. We now show that this relationship is in fact bidirectional, whereby PI3K reciprocally controls PTEN. We report that the p110delta PI3K negatively regulates PTEN, through a pathway involving inhibition of RhoA. Inactivation of p110delta in macrophages led to reduced Akt and Rac1 activation, but paradoxically to increased RhoA and PTEN activity. Partial inactivation of p190RhoGAP and a reduced binding of cytoplasmic RhoA to the cyclin-dependent kinase inhibitor p27 both contributed to the increased RhoA-GTP levels upon p110delta inactivation. Pharmacological inhibition of ROCK, a downstream effector kinase of RhoA, restored all signalling and functional defects of p110delta inactivation, including Akt phosphorylation, chemotaxis and proliferation. This work identifies the RhoA/ROCK pathway as a major target of p110delta-mediated PI3K signalling, and establishes for the first time that PI3K controls itself, via a feedback loop involving PTEN.
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Affiliation(s)
| | - Anne J Ridley
- Ludwig Institute for Cancer Research, London, UK
- Department of Biochemistry and Molecular Biology, University College London, London, UK
| | - Bart Vanhaesebroeck
- Ludwig Institute for Cancer Research, London, UK
- Department of Biochemistry and Molecular Biology, University College London, London, UK
- Ludwig Institute for Cancer Research, 91 Riding House Street, London W1W 7BS, UK. Tel.: +44 207 878 4066; Fax: +44 207 878 4040; E-mail:
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270
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Ballou LM, Selinger ES, Choi JY, Drueckhammer DG, Lin RZ. Inhibition of mammalian target of rapamycin signaling by 2-(morpholin-1-yl)pyrimido[2,1-alpha]isoquinolin-4-one. J Biol Chem 2007; 282:24463-70. [PMID: 17562705 DOI: 10.1074/jbc.m704741200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Signaling through the mammalian target of rapamycin (mTOR) is hyperactivated in many human tumors, including hamartomas associated with tuberous sclerosis complex (TSC). Several small molecules such as LY294002 inhibit mTOR kinase activity, but they also inhibit phosphatidylinositol 3-kinase (PI3K) at similar concentrations. Compound 401 is a synthetic inhibitor of DNA-dependent protein kinase (DNA-PK) that also targets mTOR but not PI3K in vitro (Griffin, R. J., Fontana, G., Golding, B. T., Guiard, S., Hardcastle, I. R., Leahy, J. J., Martin, N., Richardson, C., Rigoreau, L., Stockley, M., and Smith, G. C. (2005) J. Med. Chem. 48, 569-585). We used 401 to test the cellular effect of mTOR inhibition without the complicating side effects on PI3K. Treatment of cells with 401 blocked the phosphorylation of sites modified by mTOR-Raptor and mTOR-Rictor complexes (ribosomal protein S6 kinase 1 Thr(389) and Akt Ser(473), respectively). By contrast, there was no direct inhibition of Akt Thr(308) phosphorylation, which is dependent on PI3K. Similar effects were also observed in cells that lack DNA-PK. The proliferation of TSC1-/- fibroblasts was inhibited in the presence of 401, but TSC1+/+ cells were resistant. In contrast to rapamycin, long-term treatment of TSC1-/- cells with 401 did not up-regulate phospho-Akt Ser(473). Because increased Akt activity promotes survival, this may explain why the level of apoptosis was increased in the presence of 401 but not rapamycin. These results suggest that mTOR kinase inhibitors might be more effective than rapamycins in controlling the growth of TSC hamartomas and other tumors that depend on elevated mTOR activity.
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Affiliation(s)
- Lisa M Ballou
- Department of Medicine, Stony Brook University, Stony Brook, New York 11794, USA.
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271
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Lindsay Y, McCoull D, Davidson L, Leslie NR, Fairservice A, Gray A, Lucocq J, Downes CP. Localization of agonist-sensitive PtdIns(3,4,5)P3 reveals a nuclear pool that is insensitive to PTEN expression. J Cell Sci 2007; 119:5160-8. [PMID: 17158918 DOI: 10.1242/jcs.000133] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Phosphatidylinositol (3,4,5) trisphosphate [PtdIns(3,4,5)P3] is a lipid second messenger, produced by Type I phosphoinositide 3-kinases (PI 3-kinases), which mediates intracellular responses to many growth factors. Although PI 3-kinases are implicated in events at both the plasma membrane and intracellular sites, including the nucleus, direct evidence for the occurrence of PtdIns(3,4,5)P3 at non-plasma membrane locations is limited. We made use of the pleckstrin homology (PH) domain of general receptor for phosphoinositides (Grp1) to detect PtdIns(3,4,5)P3 in an on-section labeling approach by quantitative immunogold electron microscopy. Swiss 3T3 cells contained low levels of PtdIns(3,4,5)P3 that increased up to 15-fold upon stimulation with platelet-derived growth factor (PDGF). The signal was sensitive to PI 3-kinase inhibitors and present mainly at plasma membranes, including lamellipodia, and in a surprisingly large pool within the nuclear matrix. Comparatively little labeling was observed in endomembranes. A similar distribution of PtdIns(3,4,5)P3 was observed in U87MG cells, which lack the PtdIns(3,4,5)P3 phosphatase, PTEN. Re-expression of PTEN into U87MG cells ablated plasma membrane PtdIns(3,4,5)P3, but not the nuclear pool of this lipid even when PTEN was targeted to nuclei. These data have important implications for the versatility of PI 3-kinase signaling and for the proposed functions of PTEN in the nucleus.
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Affiliation(s)
- Yvonne Lindsay
- Division of Molecular Physiology, College of Life Sciences, University of Dundee, Dundee, DD1 5EH, UK
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272
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Lim S, Clément MV. Phosphorylation of the survival kinase Akt by superoxide is dependent on an ascorbate-reversible oxidation of PTEN. Free Radic Biol Med 2007; 42:1178-92. [PMID: 17382199 DOI: 10.1016/j.freeradbiomed.2007.01.013] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/26/2006] [Revised: 12/13/2006] [Accepted: 01/08/2007] [Indexed: 10/23/2022]
Abstract
In this report, we demonstrate that in serum-deprived mouse embryonic fibroblasts an increase in intracellular level of superoxide through pharmacological inhibition of the Cu/ZnSOD protein or the down-regulation of its expression using specific siRNA mimics growth factor-induced phosphorylation of Akt. Using the PI3K inhibitor LY294002 and PTEN knockout mouse embryonic fibroblasts, we show that phosphorylation of Akt by superoxide requires the production of PIP3 and that the target for the induction of Akt phosphorylation by O2.- is the phosphatase PTEN. Interestingly, the inhibition of PTEN involves an O2.--mediated oxidation of the phosphatase rather than regulation of its phosphorylation or decreased protein expression. Moreover, using differential reduction of oxidized protein by DTT and ascorbate, O2.--dependent oxidation of PTEN is shown to be due to S-nitrosylation of the protein. Finally, exposure of serum-deprived mouse embryonic fibroblasts to fetal bovine serum leads to a rapid and strong phosphorylation of Akt that is dependent on an ascorbate-reversible O2.--mediated oxidation of PTEN. These results support O2.- as a physiologically relevant second messenger for Akt activation through S-nitrosylation of PTEN and offer a mechanistic explanation for the mitogenic and prosurvival activities of O2.-.
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Affiliation(s)
- Sharon Lim
- Yong Loo Lin School of Medicine, Department of Biochemistry, National University of Singapore, Singapore 119260, Singapore
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273
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Downes CP, Leslie NR, Batty IH, van der Kaay J. Metabolic switching of PI3K-dependent lipid signals. Biochem Soc Trans 2007; 35:188-92. [PMID: 17371235 DOI: 10.1042/bst0350188] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The lipid phosphatase, PTEN (phosphatase and tensin homologue deleted on chromosome 10), is the product of a major tumour suppressor gene that antagonizes PI3K (phosphoinositide 3-kinase) signalling by dephosphorylating the 3-position of the inositol ring of PtdIns(3,4,5)P3. PtdIns(3,4,5)P3 is also metabolized by removal of the 5-phosphate catalysed by a distinct family of enzymes exemplified by SHIP1 [SH2 (Src homology 2)-containing inositol phosphatase 1] and SHIP2. Mouse knockout studies, however, suggest that PTEN and SHIP2 have profoundly different biological functions. One important reason for this is likely to be that SHIP2 exists in a relatively inactive state until cells are exposed to growth factors or other stimuli. Hence, regulation of SHIP2 is geared towards stimulus dependent antagonism of PI3K signalling. PTEN, on the other hand, appears to be active in unstimulated cells and functions to maintain basal PtdIns(3,4,5)P3 levels below the critical signalling threshold. We suggest that concomitant inhibition of cysteine-dependent phosphatases, such as PTEN, with activation of SHIP2 functions as a metabolic switch to regulate independently the relative levels of PtdIns(3,4,5)P3 and PtdIns(3,4)P2.
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Affiliation(s)
- C P Downes
- Division of Molecular Physiology, James Black Centre, College of Life Sciences, University of Dundee, Dundee, UK.
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274
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Nakajima H, Sakaguchi K, Fujiwara I, Mizuta M, Tsuruga M, Magae J, Mizuta N. Apoptosis and inactivation of the PI3-kinase pathway by tetrocarcin A in breast cancers. Biochem Biophys Res Commun 2007; 356:260-5. [PMID: 17350598 DOI: 10.1016/j.bbrc.2007.02.136] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2007] [Accepted: 02/22/2007] [Indexed: 11/16/2022]
Abstract
A survival kinase, Akt, is a downstream factor in the phosphatidylinositide-3'-kinase-dependent pathway, which mediates many biological responses including glucose uptake, protein synthesis and the regulation of proliferation and apoptosis, which is assumed to contribute to acquisition of malignant properties of human cancers. Here we find that an anti-tumor antibiotic, tetrocarcin A, directly induces apoptosis of human breast cancer cells. The apoptosis is accompanied by the activation of a proteolytic cascade of caspases including caspase-3 and -9, and concomitantly decreases phosphorylation of Akt, PDK1, and PTEN, a tumor suppressor that regulates the activity of Akt through the dephosphorylation of polyphosphoinositides. Tetrocarcin A affected neither expression of Akt, PDK1, or PTEN, nor did it affect the expression of Bcl family members including Bcl-2, Bcl-X(L), and Bax. These results suggest that tetrocarcin A could be a potent chemotherapeutic agent for human breast cancer targeting the phosphatidylinositide-3'-kinase/Akt signaling pathway.
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Affiliation(s)
- Hiroo Nakajima
- Department of Endocrine and Breast Surgery, Kyoto Prefectural University of Medicine, Kawaramachi, Hirokoji, Kamikyo-ku, Kyoto 602-0841, Japan
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275
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Görner K, Holtorf E, Waak J, Pham TT, Vogt-Weisenhorn DM, Wurst W, Haass C, Kahle PJ. Structural determinants of the C-terminal helix-kink-helix motif essential for protein stability and survival promoting activity of DJ-1. J Biol Chem 2007; 282:13680-91. [PMID: 17331951 DOI: 10.1074/jbc.m609821200] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Mutations in the PARK7 gene encoding DJ-1 cause autosomal recessive Parkinson disease. The most deleterious point mutation is the L166P substitution, which resides in a structure motif comprising two alpha-helices (G and H) separated by a kink. Here we subjected the C-terminal helix-kink-helix motif to systematic site-directed mutagenesis, introducing helix-incompatible proline residues as well as conservative substitutions into the helical interface. Furthermore, we generated deletion mutants lacking the H-helix, the kink, and the entire C terminus. When transfected into neural and nonneural cell lines, steady-state levels of G-helix breaking and kink deletion mutants were dramatically lower than wild-type DJ-1. The effects of H-helix breakers were comparably smaller, and the non-helix breaking mutants only slightly destabilized DJ-1. The decreased steady-state levels were due to accelerated protein degradation involving in part the proteasome. G-helix breaking DJ-1 mutations abolished dimer formation. These structural perturbations had functional consequences on the cytoprotective activities of DJ-1. The destabilizing mutations conferred reduced cytoprotection against H(2)O(2) in transiently retransfected DJ-1 knock-out mouse embryonic fibroblasts. The loss of survival promoting activity of the DJ-1 mutants with destabilizing C-terminal mutations correlated with impaired anti-apoptotic signaling. We found that wild-type, but not mutant DJ-1 facilitated the Akt pathway and simultaneously blocked the apoptosis signal-regulating kinase 1, with which DJ-1 interacted in a redox-dependent manner. Thus, the G-helix and kink are critical determinants of the C-terminal helix-kink-helix motif, which is absolutely required for stability and the regulation of survival-promoting redox signaling of the Parkinson disease-associated protein DJ-1.
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Affiliation(s)
- Karin Görner
- Laboratory of Alzheimer's and Parkinson's Disease Research, Department of Biochemistry, Ludwig Maximilians University of Munich, 80336 Munich, Germany
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276
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Mocanu MM, Yellon DM. PTEN, the Achilles' heel of myocardial ischaemia/reperfusion injury? Br J Pharmacol 2007; 150:833-8. [PMID: 17293884 PMCID: PMC2013879 DOI: 10.1038/sj.bjp.0707155] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Myocardial ischaemia/reperfusion injury leading to myocardial infarction is one of the most frequent causes of debilitation and death in man. Considerable research has been undertaken to investigate the possibility of reducing myocardial infarction and increasing cell survival by activating certain endogenous prosurvival signaling pathways. Thus, it has been established that the activation of the PI3K (Phosphoinositide-3 kinase)/Akt (Protein kinase B, PKB) signaling pathway is essential for protection against ischaemia/reperfusion injury. This pathway has been shown to be activated by mechanical procedures (e.g. pre and post conditioning) as well as by a number of pharmacological agents. Although the activation of this prosurvival signaling pathway induces the phosphorylation of a large number of substrates implicated in increased cell survival, when activated over a prolonged period this pathway can have detrimental consequences by facilitating unwanted growth and malignancies. Importantly PTEN (phosphatase and tensin homolog deleted on chromosome ten), is the main phosphatase which negatively regulates the PI3K/Akt pathway. In this review we discuss: a) the significance and the limitations of inhibiting PTEN in myocardial ischaemia/reperfusion injury; b) PTEN and its relationship to ischaemic preconditioning, c) the role of PTEN in the development of tolerance to chronic administration of drugs known to limit infarction by activating PI3K/Akt pathway when given acutely, and d) the possible role of PTEN in the ischaemic/reperfused diabetic heart. The experimental evidence discussed in this review illustrates the importance of PTEN inhibition in the protection of the heart against ischaemia/reperfusion injury.
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Affiliation(s)
- M M Mocanu
- The Hatter Cardiovascular Institute, Department of Medicine, UCL Chenies Mews, London, UK
| | - D M Yellon
- The Hatter Cardiovascular Institute, Department of Medicine, UCL Chenies Mews, London, UK
- Author for correspondence:
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277
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Wang X, Trotman L, Koppie T, Alimonti A, Gao Z, Wang J, Erdjument-Bromage H, Tempst P, Cordon-Cardo C, Pandolfi PP, Jiang X. NEDD4-1 is a proto-oncogenic ubiquitin ligase for PTEN. Cell 2007; 128:129-39. [PMID: 17218260 PMCID: PMC1828909 DOI: 10.1016/j.cell.2006.11.039] [Citation(s) in RCA: 548] [Impact Index Per Article: 32.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2006] [Revised: 08/08/2006] [Accepted: 11/01/2006] [Indexed: 12/17/2022]
Abstract
The tumor suppressor PTEN, a critical regulator for multiple cellular processes, is mutated or deleted frequently in various human cancers. Subtle reductions in PTEN expression levels have profound impacts on carcinogenesis. Here we show that PTEN level is regulated by ubiquitin-mediated proteasomal degradation, and purified its ubiquitin ligase as HECT-domain protein NEDD4-1. In cells NEDD4-1 negatively regulates PTEN stability by catalyzing PTEN polyubiquitination. Consistent with the tumor-suppressive role of PTEN, overexpression of NEDD4-1 potentiated cellular transformation. Strikingly, in a mouse cancer model and multiple human cancer samples where the genetic background of PTEN was normal but its protein levels were low, NEDD4-1 was highly expressed, suggesting that aberrant upregulation of NEDD4-1 can posttranslationally suppress PTEN in cancers. Elimination of NEDD4-1 expression inhibited xenotransplanted tumor growth in a PTEN-dependent manner. Therefore, NEDD4-1 is a potential proto-oncogene that negatively regulates PTEN via ubiquitination, a paradigm analogous to that of Mdm2 and p53.
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Affiliation(s)
- Xinjiang Wang
- Cell Biology Program, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, Box 522, New York, NY 10021
| | - Lloyd Trotman
- Cancer Biology and Genetics Program, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, Box 522, New York, NY 10021
- Department of Pathology, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, Box 522, New York, NY 10021
| | - Theresa Koppie
- Department of Pathology, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, Box 522, New York, NY 10021
| | - Andrea Alimonti
- Cancer Biology and Genetics Program, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, Box 522, New York, NY 10021
- Department of Pathology, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, Box 522, New York, NY 10021
| | - Zhonghua Gao
- Cell Biology Program, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, Box 522, New York, NY 10021
| | - Junru Wang
- Cell Biology Program, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, Box 522, New York, NY 10021
| | - Hediye Erdjument-Bromage
- Molecular Biology Program, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, Box 522, New York, NY 10021
| | - Paul Tempst
- Molecular Biology Program, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, Box 522, New York, NY 10021
| | - Carlos Cordon-Cardo
- Department of Pathology, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, Box 522, New York, NY 10021
| | - Pier Paolo Pandolfi
- Cancer Biology and Genetics Program, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, Box 522, New York, NY 10021
- Department of Pathology, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, Box 522, New York, NY 10021
| | - Xuejun Jiang
- Cell Biology Program, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, Box 522, New York, NY 10021
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278
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Wang R, He G, Nelman-Gonzalez M, Ashorn CL, Gallick GE, Stukenberg PT, Kirschner MW, Kuang J. NEDD4-1 is a proto-oncogenic ubiquitin ligase for PTEN. Cell 2007; 128:1119-32. [PMID: 17382881 DOI: 10.1016/j.cell.2006.11.053] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2006] [Revised: 08/31/2006] [Accepted: 11/21/2006] [Indexed: 02/08/2023]
Abstract
The tumor suppressor PTEN, a critical regulator for multiple cellular processes, is mutated or deleted frequently in various human cancers. Subtle reductions in PTEN expression levels have profound impacts on carcinogenesis. Here we show that PTEN level is regulated by ubiquitin-mediated proteasomal degradation, and purified its ubiquitin ligase as HECT-domain protein NEDD4-1. In cells NEDD4-1 negatively regulates PTEN stability by catalyzing PTEN polyubiquitination. Consistent with the tumor-suppressive role of PTEN, overexpression of NEDD4-1 potentiated cellular transformation. Strikingly, in a mouse cancer model and multiple human cancer samples where the genetic background of PTEN was normal but its protein levels were low, NEDD4-1 was highly expressed, suggesting that aberrant upregulation of NEDD4-1 can posttranslationally suppress PTEN in cancers. Elimination of NEDD4-1 expression inhibited xenotransplanted tumor growth in a PTEN-dependent manner. Therefore, NEDD4-1 is a potential proto-oncogene that negatively regulates PTEN via ubiquitination, a paradigm analogous to that of Mdm2 and p53.
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Affiliation(s)
- Ruoning Wang
- Department of Experimental Therapeutics, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA
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279
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Trotman LC, Wang X, Alimonti A, Chen Z, Teruya-Feldstein J, Yang H, Pavletich NP, Carver BS, Cordon-Cardo C, Erdjument-Bromage H, Tempst P, Chi SG, Kim HJ, Misteli T, Jiang X, Pandolfi PP. Ubiquitination regulates PTEN nuclear import and tumor suppression. Cell 2007; 128:141-56. [PMID: 17218261 PMCID: PMC1855245 DOI: 10.1016/j.cell.2006.11.040] [Citation(s) in RCA: 591] [Impact Index Per Article: 34.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2006] [Revised: 07/02/2006] [Accepted: 11/01/2006] [Indexed: 12/13/2022]
Abstract
The PTEN tumor suppressor is frequently affected in cancer cells, and inherited PTEN mutation causes cancer-susceptibility conditions such as Cowden syndrome. PTEN acts as a plasma-membrane lipid-phosphatase antagonizing the phosphoinositide 3-kinase/AKT cell survival pathway. However, PTEN is also found in cell nuclei, but mechanism, function, and relevance of nuclear localization remain unclear. We show that nuclear PTEN is essential for tumor suppression and that PTEN nuclear import is mediated by its monoubiquitination. A lysine mutant of PTEN, K289E associated with Cowden syndrome, retains catalytic activity but fails to accumulate in nuclei of patient tissue due to an import defect. We identify this and another lysine residue as major monoubiquitination sites essential for PTEN import. While nuclear PTEN is stable, polyubiquitination leads to its degradation in the cytoplasm. Thus, we identify cancer-associated mutations of PTEN that target its posttranslational modification and demonstrate how a discrete molecular mechanism dictates tumor progression by differentiating between degradation and protection of PTEN.
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Affiliation(s)
- Lloyd C Trotman
- Cancer Biology and Genetics Program, Sloan-Kettering Institute, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA
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280
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Wong JT, Kim PTW, Peacock JW, Yau TY, Mui ALF, Chung SW, Sossi V, Doudet D, Green D, Ruth TJ, Parsons R, Verchere CB, Ong CJ. Pten (phosphatase and tensin homologue gene) haploinsufficiency promotes insulin hypersensitivity. Diabetologia 2007; 50:395-403. [PMID: 17195063 PMCID: PMC1781097 DOI: 10.1007/s00125-006-0531-x] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/09/2006] [Accepted: 09/18/2006] [Indexed: 01/24/2023]
Abstract
AIMS/HYPOTHESIS Insulin controls glucose metabolism via multiple signalling pathways, including the phosphatidylinositol 3-kinase (PI3K) pathway in muscle and adipose tissue. The protein/lipid phosphatase Pten (phosphatase and tensin homologue deleted on chromosome 10) attenuates PI3K signalling by dephosphorylating the phosphatidylinositol 3,4,5-trisphosphate generated by PI3K. The current study was aimed at investigating the effect of haploinsufficiency for Pten on insulin-stimulated glucose uptake. MATERIALS AND METHODS Insulin sensitivity in Pten heterozygous (Pten(+/-)) mice was investigated in i.p. insulin challenge and glucose tolerance tests. Glucose uptake was monitored in vitro in primary cultures of myocytes from Pten(+/-) mice, and in vivo by positron emission tomography. The phosphorylation status of protein kinase B (PKB/Akt), a downstream signalling protein in the PI3K pathway, and glycogen synthase kinase 3beta (GSK3beta), a substrate of PKB/Akt, was determined by western immunoblotting. RESULTS Following i.p. insulin challenge, blood glucose levels in Pten(+/-) mice remained depressed for up to 120 min, whereas glucose levels in wild-type mice began to recover after approximately 30 min. After glucose challenge, blood glucose returned to normal about twice as rapidly in Pten(+/-) mice. Enhanced glucose uptake was observed both in Pten(+/-) myocytes and in skeletal muscle of Pten(+/-) mice by PET. PKB and GSK3beta phosphorylation was enhanced and prolonged in Pten(+/-) myocytes. CONCLUSIONS/INTERPRETATION Pten is a key negative regulator of insulin-stimulated glucose uptake in vitro and in vivo. The partial reduction of Pten due to Pten haploinsufficiency is enough to elicit enhanced insulin sensitivity and glucose tolerance in Pten(+/-) mice.
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Affiliation(s)
- J. T. Wong
- The Prostate Centre at Vancouver General Hospital, Vancouver Coastal Health Research Institute, 2660 Oak Street, Vancouver, BC, Canada V6H 3Z6
- Department of Surgery, University of British Columbia, Vancouver, BC Canada
| | - P. T. W. Kim
- Department of Surgery, University of British Columbia, Vancouver, BC Canada
| | - J. W. Peacock
- The Prostate Centre at Vancouver General Hospital, Vancouver Coastal Health Research Institute, 2660 Oak Street, Vancouver, BC, Canada V6H 3Z6
- Department of Surgery, University of British Columbia, Vancouver, BC Canada
| | - T. Y. Yau
- The Prostate Centre at Vancouver General Hospital, Vancouver Coastal Health Research Institute, 2660 Oak Street, Vancouver, BC, Canada V6H 3Z6
- Department of Surgery, University of British Columbia, Vancouver, BC Canada
| | - A. L.-F. Mui
- Department of Surgery, University of British Columbia, Vancouver, BC Canada
| | - S. W. Chung
- Department of Surgery, University of British Columbia, Vancouver, BC Canada
| | - V. Sossi
- Department of Physics, University of British Columbia, Vancouver, BC Canada
| | | | - D. Green
- British Columbia Cancer Research Institute, Vancouver, BC Canada
| | | | - R. Parsons
- Institute of Cancer Genetics, College of Physicians and Surgeons, Columbia University, New York, NY USA
| | - C. B. Verchere
- Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC Canada
| | - C. J. Ong
- The Prostate Centre at Vancouver General Hospital, Vancouver Coastal Health Research Institute, 2660 Oak Street, Vancouver, BC, Canada V6H 3Z6
- Department of Surgery, University of British Columbia, Vancouver, BC Canada
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281
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Rogers SJ, Box C, Harrington KJ, Nutting C, Rhys-Evans P, Eccles SA. The phosphoinositide 3-kinase signalling pathway as a therapeutic target in squamous cell carcinoma of the head and neck. Expert Opin Ther Targets 2007; 9:769-90. [PMID: 16083342 DOI: 10.1517/14728222.9.4.769] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Squamous cell carcinoma of the head and neck (SCCHN) is associated with high morbidity and mortality. Despite significant surgical advances and refinement in the delivery of chemotherapy and radiotherapy, prognosis has improved little in recent decades. Better local control has led to the late presentation of distant metastases and novel therapeutic agents are urgently required to prevent relapse, control disseminated disease and thus improve survival. PIK3CA encodes the p110alpha isoform of phosphoinositide 3-kinase (PI3-K) and is important in SCCHN, aberrations in its activity occurring early in the oncogenic process. PI3-K signalling promotes cell survival, proliferation, invasion and angiogenesis, all contributing to tumour progression. Activation of the PI3-K pathway may also mediate resistance to chemotherapy, radiotherapy and novel therapeutic agents such as epidermal growth factor receptor inhibitors. Elements of this signalling matrix, therefore, offer attractive therapeutic targets in SCCHN as inhibition of many malignant characteristics, as well as sensitisation to multiple treatment modalities, could be anticipated.
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Affiliation(s)
- Susanne J Rogers
- Cancer Research UK Centre for Cancer Therapeutics, Tumour Biology and Metastasis Team, Institute of Cancer Research, McElwain Laboratories, Cotswold Rd, Belmont, Sutton, Surrey, SM2 5NG, UK
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282
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Denning G, Jean-Joseph B, Prince C, Durden DL, Vogt PK. A short N-terminal sequence of PTEN controls cytoplasmic localization and is required for suppression of cell growth. Oncogene 2007; 26:3930-40. [PMID: 17213812 DOI: 10.1038/sj.onc.1210175] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) is an important negative regulator of cell growth and a tumor suppressor. Its growth-attenuating activity is based on the dephosphorylation of phosphatidylinositol 3,4,5-trisphosphate (PIP3), an essential second messenger for the phosphoinositide 3-kinase/Akt signaling pathway. This activity may require localization of PTEN to cytoplasmic membranes. Yet PTEN can also localize to the cell nucleus where its functions remain unclear. Here we present data that define a short sequence in the N-terminal region of PTEN required for cytoplasmic localization. We will refer to this sequence as cytoplasmic localization signal (CLS). It could function as a non-canonical signal for nuclear export or as a cytoplasmic retention signal of PTEN. Mutations within the CLS induce nuclear localization and impair growth suppressive activities of PTEN while preserving lipid phosphatase activity. We propose that nuclear localization of PTEN is not compatible with plasma membrane-targeted growth suppressive functions of PTEN.
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Affiliation(s)
- G Denning
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA, USA.
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283
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Burkholder TJ. Mechanotransduction in skeletal muscle. FRONTIERS IN BIOSCIENCE : A JOURNAL AND VIRTUAL LIBRARY 2007; 12:174-91. [PMID: 17127292 PMCID: PMC2043154 DOI: 10.2741/2057] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Mechanical signals are critical to the development and maintenance of skeletal muscle, but the mechanisms that convert these shape changes to biochemical signals is not known. When a deformation is imposed on a muscle, changes in cellular and molecular conformations link the mechanical forces with biochemical signals, and the close integration of mechanical signals with electrical, metabolic, and hormonal signaling may disguise the aspect of the response that is specific to the mechanical forces. The mechanically induced conformational change may directly activate downstream signaling and may trigger messenger systems to activate signaling indirectly. Major effectors of mechanotransduction include the ubiquitous mitogen activated protein kinase (MAP) and phosphatidylinositol-3' kinase (PI-3K), which have well described receptor dependent cascades, but the chain of events leading from mechanical stimulation to biochemical cascade is not clear. This review will discuss the mechanics of biological deformation, loading of cellular and molecular structures, and some of the principal signaling mechanisms associated with mechanotransduction.
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Affiliation(s)
- Thomas J Burkholder
- School of Applied Physiology, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
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284
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Nakamura H, Dan S, Akashi T, Unno M, Yamori T. Absolute Quantification of Four Isoforms of the Class I Phosphoinositide-3-kinase Catalytic Subunit by Real-Time RT-PCR. Biol Pharm Bull 2007; 30:1181-4. [PMID: 17541179 DOI: 10.1248/bpb.30.1181] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Class I phosphoinositide-3-kinase (PI3K) consists of four isoforms of the catalytic subunit, p110alpha, -beta, -delta and -gamma, generated from the genes PIK3CA, -B, -D and -G, respectively. These isoforms show different tissue distribution and some specific and indispensable functions in various biological pathways such as development, inflammation, autoimmunity and malignancy. In human cancers, frequent genomic amplification and gain-of-function mutations of PIK3CA were reported, which suggests an oncogenic potential. However, the role played by the other three isoforms in human cancer remains to be determined. We wanted to investigate the relationship between all the isoforms in human cancers. Here, we have established a system for the simultaneous absolute-quantification of all four isoforms by real-time reverse transcription polymerase chain reaction (RT-PCR). The reliability of this system was confirmed using three main criteria: (i) good correlation of each standard curve, (ii) high specificity of the PCR reactions and (iii) excellent reproducibility. Using this system, we investigated human monocytic leukemia cells (U937) to analyze expression of all four isoforms. The biological implications of the expression level of the four isoforms of class I PI3K catalytic subunit are discussed.
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285
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Sørensen KD, Borre M, Ørntoft TF, Dyrskjøt L, Tørring N. Chromosomal deletion, promoter hypermethylation and downregulation ofFYN in prostate cancer. Int J Cancer 2007; 122:509-19. [DOI: 10.1002/ijc.23136] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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286
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Downes CP, Ross S, Maccario H, Perera N, Davidson L, Leslie NR. Stimulation of PI 3-kinase signaling via inhibition of the tumor suppressor phosphatase, PTEN. ACTA ACUST UNITED AC 2006; 47:184-94. [PMID: 17343901 DOI: 10.1016/j.advenzreg.2006.12.018] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- C Peter Downes
- Division of Molecular Physiology, Faculty of Life Sciences, University of Dundee, Dundee, DD1 5EH, UK.
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287
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Affiliation(s)
- A Gil
- Centro de Investigación Príncipe Felipe, Valencia, Spain
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288
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Festjens N, Cornelis S, Lamkanfi M, Vandenabeele P. Caspase-containing complexes in the regulation of cell death and inflammation. Biol Chem 2006; 387:1005-16. [PMID: 16895469 DOI: 10.1515/bc.2006.124] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Caspases are a family of cysteine proteases that are essential in the initiation and execution of apoptosis and the proteolytic maturation of inflammatory cytokines such as IL-1beta and IL-18. Caspases can be subdivided into those that have a large prodomain and those that have not. In general, apoptotic and inflammatory signalling pathways are initiated when large-prodomain caspases are recruited to large protein complexes via homotypic interactions involving death domain folds. The formation of these specialised multimeric platforms involves three major functions: (1) the sensing of cellular stress, damage, infection or inflammation; (2) multimerisation of the platform; and (3) recruitment and conformational activation of caspases. In this overview we discuss the complexes implicated in the regulation of cell death and inflammatory processes such as the death-inducing signalling complex (DISC), the apoptosome, the inflammasomes and the PIDDosome. We describe their sensing functions, compositions and functional outcomes. Inhibitory protein families such as FLIPs and CARD-only proteins prevent the recruitment of caspases in these sensing complexes, avoiding inappropriate initiation of cell death or inflammation.
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Affiliation(s)
- Nele Festjens
- Molecular Signalling and Cell Death Unit, Department for Molecular Biomedical Research, VIB and Ghent University, Fiers-Schell-Van Montagu Building, Technologiepark 927, B-9052 Ghent, Belgium
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289
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Tokunaga E, Oki E, Kimura Y, Yamanaka T, Egashira A, Nishida K, Koga T, Morita M, Kakeji Y, Maehara Y. Coexistence of the loss of heterozygosity at the PTEN locus and HER2 overexpression enhances the Akt activity thus leading to a negative progesterone receptor expression in breast carcinoma. Breast Cancer Res Treat 2006; 101:249-57. [PMID: 17006756 DOI: 10.1007/s10549-006-9295-8] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2006] [Accepted: 05/31/2006] [Indexed: 11/29/2022]
Abstract
Serine/threonine kinase Akt/PKB is known to regulate divergent cellular processes, including apoptosis, proliferation, differentiation, and metabolism. Akt is activated by a variety of stimuli, through such growth factor receptors as HER2, in phosphoinositide-3-OH kinase (PI3K)-dependent manner. A loss of phosphatase and tensin homolog deleted on chromosome 10 (PTEN) function also activates Akt. It has recently been shown that Akt activation is associated with a worse outcome among endocrine treated breast cancer patients and that it also inhibits the progesterone receptor (PR) expression via the PI3K/Akt pathway in breast cancer cells. Therefore, the PI3K/Akt signaling pathway has recently attracted considerable attention as a new target for effective therapeutic strategies. In the present study, we investigated the relationship between Akt activation and either HER2 overexpression or PTEN gene alteration, as well as the PR expression. We analyzed the incidence of LOH at the PTEN locus in 138 breast cancer patients, using our new system for microsatellite analysis, called high-resolution fluorescent microsatellite analysis (HRFMA). We showed Akt activation to significantly correlate with HER2 overexpression or LOH at the PTEN gene locus while inversely correlating with the PR expression. In addition, when LOH at the PTEN gene locus and HER2 overexpression occurred simultaneously, the incidence of Akt activation and reduced PR expression was significant. The association between Akt activation and PR negative expression was observed even in the ER-positive cases. Our results suggest that simultaneous PTEN LOH and HER2 overexpression enhances Akt activation and may thus lead to a negative PR expression.
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Affiliation(s)
- Eriko Tokunaga
- Department of Surgery and Science, Graduate School of Medical Sciences, Kyushu University, Maidashi 3-1-1, Fukuoka 812-8582, Japan.
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290
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Abstract
Cytokinesis is a sequential process that occurs in three phases: assembly of the cytokinetic apparatus, furrow progression and fission (abscission) of the newly formed daughter cells. The ingression of the cleavage furrow is dependent on the constriction of an equatorial actomyosin ring in many cell types. Recent studies have demonstrated that this structure is highly dynamic and undergoes active polymerization and depolymerization throughout the furrowing process. Despite much progress in the identification of contractile ring components, little is known regarding the mechanism of its assembly and structural rearrangements. PIP2 (phosphatidylinositol 4,5-bisphosphate) is a critical regulator of actin dynamics and plays an essential role in cell motility and adhesion. Recent studies have indicated that an elevation of PIP2 at the cleavage furrow is a critical event for furrow stability. In this review we discuss the role of PIP2-mediated signalling in the structural maintenance of the contractile ring and furrow progression. In addition, we address the role of other phosphoinositides, PI(4)P (phosphatidylinositol 4-phosphate) and PIP3 (phosphatidylinositol 3,4,5-triphosphate) in these processes.
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Affiliation(s)
- Michael R Logan
- Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec, Canada H3A 2B2
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291
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Okahara F, Itoh K, Nakagawara A, Murakami M, Kanaho Y, Maehama T. Critical role of PICT-1, a tumor suppressor candidate, in phosphatidylinositol 3,4,5-trisphosphate signals and tumorigenic transformation. Mol Biol Cell 2006; 17:4888-95. [PMID: 16971513 PMCID: PMC1635402 DOI: 10.1091/mbc.e06-04-0301] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
The tumor suppressor phosphatase and tensin homolog deleted on chromosome 10 (PTEN) regulates diverse cellular functions by dephosphorylating the lipid second messenger, phosphatidylinositol 3,4,5-trisphosphate (PIP(3)). Recent study revealed that PICT-1/GLTSCR2 bound to and stabilized PTEN protein in cells, implicating its roles in PTEN-governed PIP(3) signals. In this study, we demonstrate that RNA interference-mediated knockdown of PICT-1 in HeLa cells down-regulated endogenous PTEN and resulted in the activation of PIP(3) downstream effectors, such as protein kinase B/Akt. Furthermore, the PICT-1 knockdown promoted HeLa cell proliferation; however the proliferation of PTEN-null cells was not altered by the PICT-1 knockdown, suggesting its dependency on PTEN status. In addition, apoptosis of HeLa cells induced by staurosporine or serum-depletion was alleviated by the PICT-1 knockdown in the similar PTEN-dependent manner. Most strikingly, the PICT-1 knockdown in HeLa and NIH3T3 cells promoted anchorage-independent growth, a hallmark of tumorigenic transformation. Furthermore, PICT-1 was aberrantly expressed in 18 (41%) of 44 human neuroblastoma specimens, and the PICT-1 loss was associated with reduced PTEN protein expression in spite of the existence of PTEN mRNA. Collectively, these results suggest that PICT-1 plays a role in PIP(3) signals through controlling PTEN protein stability and the impairment in the PICT-1-PTEN regulatory unit may become a causative factor in human tumor(s).
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Affiliation(s)
- Fumiaki Okahara
- *Biomembrane Signaling Project, Tokyo Metropolitan Institute of Medical Science, Tokyo 113-8613, Japan
- Department of Physiological Chemistry, Graduate School of Comprehensive Human Sciences and Institute of Basic Medical Sciences, University of Tsukuba, Tsukuba 305-8575, Japan
| | - Kouichi Itoh
- Laboratory of Molecular Pharmacology, Department of Pharmaceutical Technology, Faculty of Pharmaceutical Sciences at Kagawa Campus, Tokushima Bunri University, Kagawa 769-2193, Japan
| | - Akira Nakagawara
- Division of Biochemistry, Chiba Cancer Center Research Institute, Chiba 260-8717, Japan; and
| | - Makoto Murakami
- *Biomembrane Signaling Project, Tokyo Metropolitan Institute of Medical Science, Tokyo 113-8613, Japan
- PRESTO, Japan Science and Technology Corporation, Saitama 332-0012, Japan
| | - Yasunori Kanaho
- Department of Physiological Chemistry, Graduate School of Comprehensive Human Sciences and Institute of Basic Medical Sciences, University of Tsukuba, Tsukuba 305-8575, Japan
| | - Tomohiko Maehama
- *Biomembrane Signaling Project, Tokyo Metropolitan Institute of Medical Science, Tokyo 113-8613, Japan
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292
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Kelloff GJ, Lippman SM, Dannenberg AJ, Sigman CC, Pearce HL, Reid BJ, Szabo E, Jordan VC, Spitz MR, Mills GB, Papadimitrakopoulou VA, Lotan R, Aggarwal BB, Bresalier RS, Kim J, Arun B, Lu KH, Thomas ME, Rhodes HE, Brewer MA, Follen M, Shin DM, Parnes HL, Siegfried JM, Evans AA, Blot WJ, Chow WH, Blount PL, Maley CC, Wang KK, Lam S, Lee JJ, Dubinett SM, Engstrom PF, Meyskens FL, O'Shaughnessy J, Hawk ET, Levin B, Nelson WG, Hong WK. Progress in chemoprevention drug development: the promise of molecular biomarkers for prevention of intraepithelial neoplasia and cancer--a plan to move forward. Clin Cancer Res 2006; 12:3661-97. [PMID: 16778094 DOI: 10.1158/1078-0432.ccr-06-1104] [Citation(s) in RCA: 218] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
This article reviews progress in chemopreventive drug development, especially data and concepts that are new since the 2002 AACR report on treatment and prevention of intraepithelial neoplasia. Molecular biomarker expressions involved in mechanisms of carcinogenesis and genetic progression models of intraepithelial neoplasia are discussed and analyzed for how they can inform mechanism-based, molecularly targeted drug development as well as risk stratification, cohort selection, and end-point selection for clinical trials. We outline the concept of augmenting the risk, mechanistic, and disease data from histopathologic intraepithelial neoplasia assessments with molecular biomarker data. Updates of work in 10 clinical target organ sites include new data on molecular progression, significant completed trials, new agents of interest, and promising directions for future clinical studies. This overview concludes with strategies for accelerating chemopreventive drug development, such as integrating the best science into chemopreventive strategies and regulatory policy, providing incentives for industry to accelerate preventive drugs, fostering multisector cooperation in sharing clinical samples and data, and creating public-private partnerships to foster new regulatory policies and public education.
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Affiliation(s)
- Gary J Kelloff
- National Cancer Institute, Bethesda, Maryland 20852, USA.
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293
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Cao Y, Adhikari S, Ang AD, Moore PK, Bhatia M. Mechanism of induction of pancreatic acinar cell apoptosis by hydrogen sulfide. Am J Physiol Cell Physiol 2006; 291:C503-10. [PMID: 16597918 DOI: 10.1152/ajpcell.00547.2005] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The present study investigated the mechanism of mouse pancreatic acinar cell apoptosis induced by H2S in an in vitro system, using isolated pancreatic acini. Treatment of pancreatic acini with 10 μM NaHS (a donor of H2S) for 3 h caused phosphatidylserine externalization as shown by annexin V binding, an indicator of early stages of apoptosis. This treatment also resulted in the activation of the caspase cascade and major changes at the mitochondrial level. Caspase-3, -8, and -9 activities were stimulated by H2S treatment. Treatment with inhibitors of caspase-3, -8, and -9 significantly inhibited H2S-induced phosphatidylserine externalization as shown by reduced annexin V staining. The mitochondrial membrane potential was collapsed in H2S-treated acini as evidenced by fluorescence microscopy and quantitative analysis. Furthermore, the treatment of acini with H2S caused the release of cytochrome c by the mitochondria. To investigate the mechanism underlying pancreatic acinar cell apoptosis, we also characterized the protein expression of a range of molecules that are each known to influence the apoptotic pathway. Among proapoptotic proteins, Bax expression was activated in H2S-treated cells but not Bid, and the antiapoptotic proteins Bcl-XL and Bcl-2 did not show any activation in pancreatic acinar cell apoptosis. The death effector domain-containing protein Flip is downregulated in H2S-treated acini. These results demonstrate the induction of pancreatic acinar cell apoptosis in vitro by H2S and the involvement of both mitochondrial and death receptor pathways in the process of apoptosis.
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Affiliation(s)
- Yang Cao
- Department of Pharmacology, National University of Singapore, Yong Loo Lin School of Medicine, Bldg. MD2, 18 Medical Drive, Singapore 117597
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294
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MacGlashan D, Vilariño N. Nonspecific desensitization, functional memory, and the characteristics of SHIP phosphorylation following IgE-mediated stimulation of human basophils. THE JOURNAL OF IMMUNOLOGY 2006; 177:1040-51. [PMID: 16818760 DOI: 10.4049/jimmunol.177.2.1040] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Previous studies of secretion from basophils have demonstrated the phenomenon called nonspecific desensitization, the ability of one IgE-mediated stimulus to alter the cell's response to other non-cross-reacting IgE-mediated stimuli, and a process that would modify phosphatidylinositol 3,4,5-phosphate levels was speculated to be responsible for nonspecific desensitization. The current studies examined the changes and characteristics of SHIP1 phosphorylation as a measure of SHIP1 participation in the reaction. Based on the earlier studies, two predictions were made that were not observed. First, the kinetics of SHIP1 phosphorylation were similar to reaction kinetics of other early signals and returned to resting levels while nonspecific desensitization remained. Second, in contrast to an expected exaggerated SHIP phosphorylation, cells in a state of nonspecific desensitization showed reduced SHIP phosphorylation (compared with cells not previously exposed to a non-cross-reacting Ag). Discordant with expectations concerning partial recovery from nonspecific desensitization, treatment of cells with DNP-lysine to dissociate bound DNP-HSA, either enhanced or had no effect on SHIP phosphorylation following a second Ag. These experiments also showed a form of desensitization that persisted despite dissociation of the desensitizing Ag. Recent studies and the results of these studies suggest that loss of early signaling components like syk kinase may account for some of the effects of nonspecific desensitization and result in a form of immunological memory of prior stimulation. Taken together, the various characteristics of SHIP phosphorylation were not consistent with expectations for a signaling element involved in nonspecific desensitization, but instead one which itself undergoes nonspecific desensitization.
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Affiliation(s)
- Donald MacGlashan
- Johns Hopkins Asthma and Allergy Center, 5501 Hopkins Bayview Center, Baltimore, MD 21224, USA.
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295
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Vaudin P, Dupont J, Duchêne S, Audouin E, Crochet S, Berri C, Tesseraud S. Phosphatase PTEN in chicken muscle is regulated during ontogenesis. Domest Anim Endocrinol 2006; 31:123-40. [PMID: 16307863 DOI: 10.1016/j.domaniend.2005.09.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/28/2005] [Revised: 09/30/2005] [Accepted: 09/30/2005] [Indexed: 11/17/2022]
Abstract
The phosphatase and TENsin homolog deleted on chromosome 10 (PTEN) is a lipid and protein phosphatase able to inhibit significant actors of cell signaling (i.e. phosphatidylinositol-3'kinase and mitogen-activated protein kinase pathways). The aim of this study was to characterize PTEN and to investigate its regulation during ontogenesis in chicken muscle. Pectoralis major muscle was sampled on day 18 of the embryonic period (E18), at hatching (d0) and in fed chickens at 2, 7 and 43 days after hatching (d2, d7 and d43). We first cloned the totality of chicken PTEN cDNA; its translation into a putative protein showed more than 95% sequence identity with that characterized in mammals (humans, mice). PTEN was expressed under two major transcripts in the majority of tissues, including muscles where the expression of PTEN mRNA increased with age (P < 0.05). Surprisingly, the protein levels of PTEN (protein characterized with an apparent molecular weight of 55kDa) and its activity were considerably decreased between the E18 and d43 stages (approximately 8-10-fold reduction, P < 0.001). An association between these decreases and higher phosphorylation levels of two potential indirect downstream targets of phosphatase (i.e. AKT and ERK) was observed only in the early growth phases. It was concluded that phosphatase PTEN was expressed in chicken muscle and that its expression was regulated during ontogenesis.
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Affiliation(s)
- Pascal Vaudin
- Recherches Avicoles, Institut National de la Recherche Agronomique, 37380 Nouzilly, France
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296
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Krueger KE, Srivastava S. Posttranslational protein modifications: current implications for cancer detection, prevention, and therapeutics. Mol Cell Proteomics 2006; 5:1799-810. [PMID: 16844681 DOI: 10.1074/mcp.r600009-mcp200] [Citation(s) in RCA: 167] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Affiliation(s)
- Karl E Krueger
- Cancer Biomarkers Research Group, Division of Cancer Prevention, NCI, National Institutes of Health, Bethesda, Maryland 20892-7362, USA
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297
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Abstract
For decades anatomic imaging with computed tomography or magnetic resonance imaging has facilitated drug development in medical oncology by providing quantifiable and objective evidence of response to cancer therapy. In recent years metabolic imaging with [18F]fluorodeoxyglucose–positron emission tomography has added an important component to the oncologist's armamentarium for earlier detection of response that is now widely used and appreciated. These modalities along with ultrasound and optical imaging (bioluminescence, fluorescence, near-infrared imaging, multispectral imaging) have become used increasingly in preclinical studies in animal models to document the effects of genetic alterations on cancer progression or metastases, the detection of minimal residual disease, and response to various therapeutics including radiation, chemotherapy, or biologic agents. The field of molecular imaging offers potential to deliver a variety of probes that can image noninvasively drug targets, drug distribution, cancer gene expression, cell surface receptor or oncoprotein levels, and biomarker predictors of prognosis, therapeutic response, or failure. Some applications are best suited to accelerate preclinical anticancer drug development, whereas other technologies may be directly transferable to the clinic. Efforts are underway to apply noninvasive in vivo imaging to specific preclinical or clinical problems to accelerate progress in the field. Because resources are limited, and patient suffering from failed or ineffective therapy continues, a concerted effort is being made to address these issues. Many simultaneous activities involving academia; the pharmaceutical, device, and biotechnology industries; US Food and Drug Administration; National Cancer Institute; Centers for Medicare and Medicaid Services; and specialized networks sponsored by the National Institutes of Health are beginning to address these issues to develop consensus recommendations and progress in this important area.
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Affiliation(s)
- Wafik S El-Deiry
- Department of Medicine (Hematology/Oncology), the Abramson Comprehensive Cancer Center, and the Institute for Translational Medicine and Therapeutics, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.
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298
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Pettitt TR, Dove SK, Lubben A, Calaminus SDJ, Wakelam MJO. Analysis of intact phosphoinositides in biological samples. J Lipid Res 2006; 47:1588-96. [PMID: 16632799 DOI: 10.1194/jlr.d600004-jlr200] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
It is now apparent that each of the known, naturally occurring polyphosphoinositides, the phosphatidylinositol monophosphates (PtdIns3P, PtdIns4P, PtdIns5P), phosphatidylinositol bisphosphates [PtdIns(3,4)P(2), PtdIns(3,5)P(2), PtdIns(4,5)P(2)], and phosphatidylinositol trisphosphate [PtdIns(3,4,5)P(3)], have distinct roles in regulating many cellular events, including intracellular signaling, migration, and vesicular trafficking. Traditional identification techniques require [(32)P]inorganic phosphate or [(3)H]inositol radiolabeling, acidified lipid extraction, deacylation, and ion-exchange head group separation, which are time-consuming and not suitable for samples in which radiolabeling is impractical, thus greatly restricting the study of these lipids in many physiologically relevant systems. Thus, we have developed a novel, high-efficiency, buffered citrate extraction methodology to minimize acid-induced phosphoinositide degradation, together with a high-sensitivity liquid chromatography-mass spectrometry (LC-MS) protocol using an acetonitrile-chloroform-methanol-water-ethylamine gradient with a microbore silica column that enables the identification and quantification of all phosphoinositides in a sample. The liquid chromatograph is sufficient to resolve PtdInsP(3) and PtdInsP(2) regioisomers; however, the PtdInsP regioisomers require a combination of LC and diagnostic fragmentation to MS(3). Data are presented using this approach for the analysis of phosphoinositides in human platelet and yeast samples.
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Affiliation(s)
- Trevor R Pettitt
- Cancer Research UK Institute for Cancer Studies, University of Birmingham, Birmingham B15 2TH, UK
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299
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Gil A, Andrés-Pons A, Fernández E, Valiente M, Torres J, Cervera J, Pulido R. Nuclear localization of PTEN by a Ran-dependent mechanism enhances apoptosis: Involvement of an N-terminal nuclear localization domain and multiple nuclear exclusion motifs. Mol Biol Cell 2006; 17:4002-13. [PMID: 16807353 PMCID: PMC1556382 DOI: 10.1091/mbc.e06-05-0380] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The targeting of the tumor suppressor PTEN protein to distinct subcellular compartments is a major regulatory mechanism of PTEN function, by controlling its access to substrates and effector proteins. Here, we investigated the molecular basis and functional consequences of PTEN nuclear/cytoplasmic distribution. PTEN accumulated in the nucleus of cells treated with apoptotic stimuli. Nuclear accumulation of PTEN was enhanced by mutations targeting motifs in distinct PTEN domains, and it was dependent on an N-terminal nuclear localization domain. Coexpression of a dominant negative Ran GTPase protein blocked PTEN accumulation in the nucleus, which was also affected by coexpression of importin alpha proteins. The lipid- and protein-phosphatase activity of PTEN differentially modulated PTEN nuclear accumulation. Furthermore, catalytically active nuclear PTEN enhanced cell apoptotic responses. Our findings indicate that multiple nuclear exclusion motifs and a nuclear localization domain control PTEN nuclear localization by a Ran-dependent mechanism and suggest a proapoptotic role for PTEN in the cell nucleus.
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Affiliation(s)
- Anabel Gil
- Centro de Investigación Príncipe Felipe, Valencia 46013, Spain
| | | | - Elena Fernández
- Centro de Investigación Príncipe Felipe, Valencia 46013, Spain
| | - Miguel Valiente
- Centro de Investigación Príncipe Felipe, Valencia 46013, Spain
| | - Josema Torres
- Centro de Investigación Príncipe Felipe, Valencia 46013, Spain
| | - Javier Cervera
- Centro de Investigación Príncipe Felipe, Valencia 46013, Spain
| | - Rafael Pulido
- Centro de Investigación Príncipe Felipe, Valencia 46013, Spain
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300
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Bayascas JR, Leslie NR, Parsons R, Fleming S, Alessi DR. Hypomorphic mutation of PDK1 suppresses tumorigenesis in PTEN(+/-) mice. Curr Biol 2006; 15:1839-46. [PMID: 16243031 DOI: 10.1016/j.cub.2005.08.066] [Citation(s) in RCA: 118] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2005] [Revised: 08/27/2005] [Accepted: 08/30/2005] [Indexed: 01/06/2023]
Abstract
Many cancers possess elevated levels of PtdIns(3,4,5)P(3), the second messenger that induces activation of the protein kinases PKB/Akt and S6K and thereby stimulates cell proliferation, growth, and survival. The importance of this pathway in tumorigenesis has been highlighted by the finding that PTEN, the lipid phosphatase that breaks down PtdIns(3,4,5)P(3) to PtdIns(4,5)P(2), is frequently mutated in human cancer. Cells lacking PTEN possess elevated levels of PtdIns(3,4,5)P(3), PKB, and S6K activity and heterozygous PTEN(+/-) mice develop a variety of tumors. Knockout of PKBalpha in PTEN-deficient cells reduces aggressive growth and promotes apoptosis, whereas treatment of PTEN(+/-) mice with rapamycin, an inhibitor of the activation of S6K, reduces neoplasia. We explored the importance of PDK1, the protein kinase that activates PKB and S6K, in mediating tumorigenesis caused by the deletion of PTEN. We demonstrate that reducing the expression of PDK1 in PTEN(+/-) mice, markedly protects these animals from developing a wide range of tumors. Our findings provide genetic evidence that PDK1 is a key effector in mediating neoplasia resulting from loss of PTEN and also validate PDK1 as a promising anticancer target for the prevention of tumors that possess elevated PKB and S6K activity.
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Affiliation(s)
- Jose R Bayascas
- MRC Protein Phosphorylation Unit, School of Life Sciences, University of Dundee, Dundee DD1 5EH, United Kingdom.
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