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Kimura T, Tomooka M, Yamano N, Murayama K, Matoba S, Umehara H, Kanai Y, Nakano T. AKT signaling promotes derivation of embryonic germ cells from primordial germ cells. Development 2008; 135:869-79. [PMID: 18216173 DOI: 10.1242/dev.013474] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Primordial germ cells (PGCs) are embryonic germ cell precursors. Although the developmental potency of PGCs is restricted to the germ lineage, PGCs can acquire pluripotency, as verified by the in vitro establishment of embryonic germ (EG) cells and the in vivo production of testicular teratomas. PGC-specific inactivation of PTEN, which is a lipid phosphatase antagonizing phosphoinositide-3 kinase (PI3K), enhances both EG cell production and testicular teratoma formation. Here, we analyzed the effect of the serine/threonine kinase AKT, one of the major downstream effectors of PI3K, on the developmental potency of PGCs. We used transgenic mice that expressed an AKT-MER fusion protein, the kinase activity of which could be regulated by the ligand of modified estrogen receptor (MER), 4-hydroxytamoxifen. We found that hyperactivation of AKT signaling in PGCs at the proliferative phase dramatically augmented the efficiency of EG cell establishment. Furthermore, AKT signaling activation substituted to some extent for the effects of bFGF, an essential growth factor for EG cell establishment. By contrast, AKT activation had no effect on germ cells that were in mitotic arrest or that began meiosis at a later embryonic stage. In the transgenic PGCs, AKT activation induced phosphorylation of GSK3, which inhibits its kinase activity; enhanced the stability and nuclear localization of MDM2; and suppressed p53 phosphorylation, which is required for its activation. The p53 deficiency, but not GSK3 inhibition, recapitulated the effects of AKT hyperactivation on EG cell derivation, suggesting that p53 is one of the crucial downstream targets of the PI3K/AKT signal and that GSK3 is not.
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Affiliation(s)
- Tohru Kimura
- Department of Pathology, Graduate School of Medicine, Osaka University, 2-2 Yamada-oka, Suita, Osaka, Japan
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Tsuruta H, Kishimoto H, Sasaki T, Horie Y, Natsui M, Shibata Y, Hamada K, Yajima N, Kawahara K, Sasaki M, Tsuchiya N, Enomoto K, Mak TW, Nakano T, Habuchi T, Suzuki A. Hyperplasia and carcinomas in Pten-deficient mice and reduced PTEN protein in human bladder cancer patients. Cancer Res 2007; 66:8389-96. [PMID: 16951148 DOI: 10.1158/0008-5472.can-05-4627] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
PTEN is a tumor suppressor gene mutated in many human cancers. We used the Cre-loxP system to generate an urothelium-specific null mutation of Pten in mice [FabpCrePten(flox/flox) (FPten(flox/flox)) mice]. Histologic examination revealed that all FPten(flox/flox) mice exhibited urothelial hyperplasia in which component cells showed enlarged nuclei and increased cell size. With time, 10% of FPten(flox/flox) mice spontaneously developed pedicellate papillary transitional cell carcinomas (TCC). This type of tumor also arose in FPten(flox/flox) mice treated with the chemical carcinogen N-butyl-N-(4-hydroxybutyl) nitrosamine. FPten(flox/flox) urothelial cells were hyperproliferative and showed increased activation of the survival signaling molecules Akt and extracellular signal-regulated kinase. In humans, 53% of primary bladder cancer patients exhibited decreased or absent expression of PTEN protein in either the cytoplasm or nucleus of tumor cells. In early bladder cancers, PTEN expression was repressed in 42% of superficial papillary TCC but in only 8% of cases of carcinoma in situ (CIS). In advanced bladder cancers, PTEN protein was significantly reduced (particularly in the nucleus) in 94% of cases, and this decrease in PTEN correlated with disease stage and grade. Thus, PTEN deficiency may contribute to bladder cancer both by initiating superficial papillary TCC and by promoting the progression of CIS to advanced invasive and metastatic forms.
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Affiliation(s)
- Hiroshi Tsuruta
- Department of Urology, Akita University School of Medicine, Akita, Japan
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Nurieva RI, Chuvpilo S, Wieder ED, Elkon KB, Locksley R, Serfling E, Dong C. A costimulation-initiated signaling pathway regulates NFATc1 transcription in T lymphocytes. THE JOURNAL OF IMMUNOLOGY 2007; 179:1096-103. [PMID: 17617602 DOI: 10.4049/jimmunol.179.2.1096] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
T cell activation and differentiation is accompanied and mediated by transcriptional reprogramming. The NFATc1 transcription factor is strongly induced upon T cell activation and controls numerous genes involved in the T cell effector function. However, its regulation by physiological stimuli in primary T cells has not been well understood. We previously found that ICOS synergizes with TCR and CD28 to greatly enhance NFATc1 expression in primary T cells. In this study, we have examined the signaling mechanisms whereby costimulation regulates NFATc1 expression. We found that CD28 and ICOS regulate sustained PI3K activity in primary T cells, which is required for NFATc1 up-regulation. CD28 and ICOS costimulation, possibly through Itk, a Tec kinase downstream of the PI3K, enhanced phosphorylation of phospholipase C gamma1 and increased and sustained Ca(2+) flux in T cells. Costimulation of T cells potentiated transcription of the Nfatc1 gene P1 promoter in a PI3K-dependent manner. This work demonstrates an important role for costimulatory receptors in sustaining T cell activation programs leading to Nfatc1 gene transcription and has implications in our understanding of the immune response and tolerance.
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Affiliation(s)
- Roza I Nurieva
- Department of Immunology, M.D. Anderson Cancer Center, Houston, TX 77030, USA
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Faucherre A, Taylor GS, Overvoorde J, Dixon JE, Hertog JD. Zebrafish pten genes have overlapping and non-redundant functions in tumorigenesis and embryonic development. Oncogene 2007; 27:1079-86. [PMID: 17704803 DOI: 10.1038/sj.onc.1210730] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
In human cancer, PTEN (Phosphatase and TENsin homolog on chromosome 10, also referred to as MMAC1 and TEP1) is a frequently mutated tumor suppressor gene. We have used the zebrafish as a model to investigate the role of Pten in embryonic development and tumorigenesis. The zebrafish genome encodes two pten genes, ptena and ptenb. Here, we report that both Pten gene products from zebrafish are functional. Target-selected inactivation of ptena and ptenb revealed that Ptena and Ptenb have redundant functions in embryonic development, in that ptena-/- and ptenb-/- mutants did not show embryonic phenotypes. Homozygous single mutants survived as adults and they were viable and fertile. Double homozygous ptena-/-ptenb-/- mutants died at 5 days post fertilization with pleiotropic defects. These defects were rescued by treatment with the phosphatidylinositol-3-kinase inhibitor, LY294002. Double homozygous embryos showed enhanced cellular proliferation. In addition, cell survival was dramatically enhanced in embryos that lack functional Pten upon gamma-irradiation. Surprisingly, adult ptenb-/- zebrafish developed ocular tumors later in life, despite the expression of ptena in adult eyes. We conclude that whereas Ptena and Ptenb have redundant functions in embryonic development, they apparently do not have completely overlapping functions later in life. These pten mutant zebrafish represent a unique model to screen for genetic and/or chemical suppressors of Pten loss-of-function.
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Affiliation(s)
- A Faucherre
- Hubrecht Institute, Utrecht, The Netherlands
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Ford-Hutchinson AF, Ali Z, Lines SE, Hallgrímsson B, Boyd SK, Jirik FR. Inactivation of Pten in osteo-chondroprogenitor cells leads to epiphyseal growth plate abnormalities and skeletal overgrowth. J Bone Miner Res 2007; 22:1245-59. [PMID: 17456009 DOI: 10.1359/jbmr.070420] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
UNLABELLED To study the role of the Pten tumor suppressor in skeletogenesis, we generated mice lacking this key phosphatidylinositol 3'-kinase pathway regulator in their osteo-chondroprogenitors. A phenotype of growth plate dysfunction and skeletal overgrowth was observed. INTRODUCTION Skeletogenesis is a complex process relying on a variety of ligands that activate a range of intracellular signal transduction pathways. Although many of these stimuli are known to activate phosphatidylinositol 3'-kinase (PI3K), the function of this pathway during cartilage development remains nebulous. To study the role of PI3K during skeletogenesis, we used mice deficient in a negative regulator of PI3K signaling, the tumor suppressor, Pten. MATERIALS AND METHODS Pten gene deletion in osteo-chondrodroprogenitors was obtained by interbreeding mice with loxP-flanked Pten exons with mice expressing the Cre recombinase under the control of the type II collagen gene promoter (Pten(flox/flox):Col2a1Cre mice). Phenotypic analyses included microcomputed tomography and immunohistochemistry techniques. RESULTS MicroCT revealed that Pten(flox/flox):Col2a1Cre mice exhibited both increased skeletal size, particularly of vertebrae, and massive trabeculation accompanied by increased cortical thickness. Primary spongiosa development and perichondrial bone collar formation were prominent in Pten(flox/flox):Col2a1Cre mice, and long bone growth plates were disorganized and showed both matrix overproduction and evidence of accelerated hypertrophic differentiation (indicated by an altered pattern of type X collagen and alkaline phosphatase expression). Consistent with increased PI3K signaling, Pten-deficient chondrocytes showed increased phospho-PKB/Akt and phospho-S6 immunostaining, reflective of increased mTOR and PDK1 activity. Interestingly, no significant change in growth plate proliferation was seen in Pten-deficient mice, and growth plate fusion was found at 6 months. CONCLUSIONS By virtue of its ability to modulate a key signal transduction pathway responsible for integrating multiple stimuli, Pten represents an important regulator of both skeletal size and bone architecture.
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Affiliation(s)
- Alice Fiona Ford-Hutchinson
- Department of Biochemistry and Molecular Biology, Alberta Bone and Joint Health Institute, University of Calgary, Calgary, Alberta, Canada
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Xie L, Jiang Y, Ouyang P, Chen J, Doan H, Herndon B, Sylvester JE, Zhang K, Molteni A, Reichle M, Zhang R, Haub MD, Baybutt RC, Wang W. Effects of dietary calorie restriction or exercise on the PI3K and Ras signaling pathways in the skin of mice. J Biol Chem 2007; 282:28025-35. [PMID: 17646168 DOI: 10.1074/jbc.m604857200] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Weight control by exercise and dietary calorie restriction (DCR) has been associated with reduced cancer risk, but the underlying mechanisms are not well understood. This study was designed to compare the effects of weight loss by increasing physical activity or decreasing calorie intake on tumor promoter-induced Ras-MAPK and PI3K-Akt pathways. SENCAR mice were randomly assigned to one of the following five groups: ad libitum-fed sedentary control, ad libitum-fed exercise (AL+Exe), exercise but pair-fed at the amount as controls (PF+Exe), 20% DCR, and 20% DCR plus exercise (DCR+Exe). After 10 weeks, body weight and body fat significantly decreased in the groups of DCR, DCR+Exe, and PF+Exe when compared with the controls. AL+Exe did not induce weight loss due to, at least in part, increased food intake. Plasma IGF-1 levels reduced significantly in DCR and DCR+Exe but not PF+Exe. The protein H-Ras and activated Ras-GTP significantly decreased in TPA-induced skin tissues of DCR-fed mice but not exercised mice. PI3K protein, phosphoserine Akt, and p42/p44-MAPK were reduced, however, in both DCR and PF+Exe groups. Immunohistochemistry demonstrated that the significantly reduced H-Ras occurred in subcutaneous fat cells, while the reduced PI3K and PCNA took place only in the epidermis. Plasma leptin decreased in PF+Exe, DCR, and DCR+Exe, while the caspase-3 activity increased in DCR+Exe only. Genomic microarray analysis further indicated that the expression of 34 genes relevant to PI3K and 31 genes to the MAPK pathway were significantly regulated by either DCR or PF+Exe treatments. The reduced PI3K in PF+Exe mice was partially reversed by IGF-1 treatment. The overall results of this study demonstrated that DCR abrogated both Ras and PI3K signaling, which might inhibit TPA-induced proliferation and anti-apoptosis. Selective inhibition of PI3K by PF+Exe but not AL+Exe seems more attributable to the magnitude of the caloric deficit and/or body fat loss than diet versus exercise comparison.
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Affiliation(s)
- Linglin Xie
- Department of Human Nutrition and Statistics, Kansas State University, Manhattan, Kansas 66506, USA
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Murayama K, Kimura T, Tarutani M, Tomooka M, Hayashi R, Okabe M, Nishida K, Itami S, Katayama I, Nakano T. Akt activation induces epidermal hyperplasia and proliferation of epidermal progenitors. Oncogene 2007; 26:4882-8. [PMID: 17297448 DOI: 10.1038/sj.onc.1210274] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Various common signaling pathways maintain tissue stem cells, including Notch and Wnt/beta-catenin signals. Phosphoinositide-3 kinase (PI3K)/Akt signaling regulates the 'stemness' of several stem cells in culture, specifically in maintaining embryonic stem and neural stem cells, and in deriving embryonic germ cells from primordial germ cells. We examined the effect of Akt signaling in epidermal cells in transgenic mice expressing an Akt-Mer fusion protein whose kinase activity was conditionally activated by treatment with 4-hydroxytamoxifen (4OHT). The topical application of 4OHT to adult skin of the transgenic mice induced new hair growth in resting phase follicles. In addition, the mice showed hyperplasia in interfollicular epidermis (IFE) and hair follicles, which was presumably caused by the extensive proliferation of keratinocytes in basal layer of IFE and outer root sheath of hair follicles, respectively. The progenitor cell population increased consistently in 4OHT-treated transgenic mice. Our results show that PI3K/Akt signaling induces epidermal hyperplasia and proliferation of epidermal progenitors.
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Affiliation(s)
- K Murayama
- Department of Pathology, Graduate School of Medicine, Osaka University, Suita, Osaka, Japan
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58
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Pinzone JJ, Eng C, Paik J, Brindle KA, Ringel MD, Katz JD. A novelPTEN mutation in Cowden syndrome is associated with a mixed degenerative-erosive arthritic process: Potential molecular pathogenic mechanisms. Am J Med Genet A 2007; 143A:1522-7. [PMID: 17568419 DOI: 10.1002/ajmg.a.31786] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Joseph J Pinzone
- Department of Internal Medicine, The Ohio State University Medical Center, 1581 Dodd Drive, Columbus, OH 43210, USA.
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Matoba R, Niwa H, Masui S, Ohtsuka S, Carter MG, Sharov AA, Ko MS. Dissecting Oct3/4-regulated gene networks in embryonic stem cells by expression profiling. PLoS One 2006; 1:e26. [PMID: 17183653 PMCID: PMC1762406 DOI: 10.1371/journal.pone.0000026] [Citation(s) in RCA: 142] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2006] [Accepted: 10/03/2006] [Indexed: 12/11/2022] Open
Abstract
POU transcription factor Pou5f1 (Oct3/4) is required to maintain ES cells in an undifferentiated state. Here we show that global expression profiling of Oct3/4-manipulated ES cells delineates the downstream target genes of Oct3/4. Combined with data from genome-wide chromatin-immunoprecipitation (ChIP) assays, this analysis identifies not only primary downstream targets of Oct3/4, but also secondary or tertiary targets. Furthermore, the analysis also reveals that downstream target genes are regulated either positively or negatively by Oct3/4. Identification of a group of genes that show both activation and repression depending on Oct3/4 expression levels provides a possible mechanism for the requirement of appropriate Oct3/4 expression to maintain undifferentiated ES cells. As a proof-of-principle study, one of the downstream genes, Tcl1, has been analyzed in detail. We show that Oct3/4 binds to the promoter region of Tcl1 and activates its transcription. We also show that Tcl1 is involved in the regulation of proliferation, but not differentiation, in ES cells. These findings suggest that the global expression profiling of gene-manipulated ES cells can help to delineate the structure and dynamics of gene regulatory networks.
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Affiliation(s)
- Ryo Matoba
- Developmental Genomics and Aging Section, Laboratory of Genetics, National Institute on Aging, National Institutes of HealthBaltimore, Maryland, United States of America
| | - Hitoshi Niwa
- Laboratory of Pluripotent Cell Studies, RIKEN Center for Developmental BiologyKobe, Japan
| | - Shinji Masui
- Laboratory of Pluripotent Cell Studies, RIKEN Center for Developmental BiologyKobe, Japan
| | - Satoshi Ohtsuka
- Laboratory of Pluripotent Cell Studies, RIKEN Center for Developmental BiologyKobe, Japan
| | - Mark G. Carter
- Developmental Genomics and Aging Section, Laboratory of Genetics, National Institute on Aging, National Institutes of HealthBaltimore, Maryland, United States of America
| | - Alexei A. Sharov
- Developmental Genomics and Aging Section, Laboratory of Genetics, National Institute on Aging, National Institutes of HealthBaltimore, Maryland, United States of America
| | - Minoru S.H. Ko
- Developmental Genomics and Aging Section, Laboratory of Genetics, National Institute on Aging, National Institutes of HealthBaltimore, Maryland, United States of America
- * To whom correspondence should be addressed. E-mail:
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Schick V, Majores M, Engels G, Spitoni S, Koch A, Elger CE, Simon M, Knobbe C, Blümcke I, Becker AJ. Activation of Akt independent of PTEN and CTMP tumor-suppressor gene mutations in epilepsy-associated Taylor-type focal cortical dysplasias. Acta Neuropathol 2006; 112:715-25. [PMID: 17013611 DOI: 10.1007/s00401-006-0128-y] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2006] [Revised: 07/28/2006] [Accepted: 07/28/2006] [Indexed: 01/18/2023]
Abstract
Focal cortical dysplasias (FCD) with Taylor-type balloon cells (FCD(IIb)) are frequently observed in biopsy specimens of patients with pharmacoresistant focal epilepsies. The molecular pathogenesis of FCD(IIb), which lack familial inheritance, is only poorly understood. Due to their highly differentiated, malformative nature and glioneuronal phenotype, FCD(IIb) share neuropathological characteristics with lesions observed in familial disorders such as cortical tubers present in patients with autosomal dominant tuberous sclerosis complex (TSC), related to mutations in the TSC1 or TSC2 genes, and dysplastic gangliocytomas of the cerebellum found in Cowden disease. Current data have indicated distinct allelic variants of TSC1 to accumulate in FCD(IIb). TSC1 represents a tumor suppressor operating in the phosphatidylinositol 3-kinase (PI3K)/insulin pathway. The tumor-suppressor gene PTEN is mutated in Cowden disease. Like PTEN, also carboxyl-terminal modulator protein (CTMP) modulates PI3K-pathway signaling, both via inhibition of Akt/PKB, a kinase inactivating the TSC1/TSC2 complex. Here, we have analyzed alterations of Akt, PTEN and CTMP relevant for insulin signaling upstream of TSC1/TSC2 in FCD(IIb). Immunohistochemistry with antibodies against phosphorylated Akt (phospho-Akt; Ser 473) in FCD(IIb) (n=23) showed strong phospho-Akt expression in dysplastic FCD(IIb) components. We have further studied sequence alterations of PTEN (n=34 FCD(IIb)) and CTMP (n=20 FCD(IIb)) by laser microdissection/single-strand conformation polymorphism analysis. We observed a somatic mutation in an FCD(IIb), i.e., amino-acid exchange at nucleotide position 834 (PTEN cDNA, GenBank AH007803.1) in exon 8 with replacement of phenylalanine by leucine (F278L). We also found several silent polymorphisms of PTEN in exon 2 and exon 8 as well as silent and coding polymorphisms but no mutations in CTMP. No loss of heterozygosity in FCD(IIb) (n=6) at 10q23 was observed. To our knowledge, we here report on the first somatic mutation of a tumor-suppressor gene, i.e., PTEN, in FCD(IIb). However, our study also demonstrates that mutational alterations of PTEN and CTMP do not play major pathogenetic roles for activation of Akt in FCD(IIb). Future studies need to determine the origin of insulin pathway activation upstream of TSC1/TSC2 in FCD(IIb).
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Affiliation(s)
- Volker Schick
- Department of Neuropathology, University of Bonn Medical Center, Sigmund-Freud-Str. 25, 53105, Bonn, Germany
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Baron V, Adamson ED, Calogero A, Ragona G, Mercola D. The transcription factor Egr1 is a direct regulator of multiple tumor suppressors including TGFbeta1, PTEN, p53, and fibronectin. Cancer Gene Ther 2006; 13:115-24. [PMID: 16138117 PMCID: PMC2455793 DOI: 10.1038/sj.cgt.7700896] [Citation(s) in RCA: 279] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Recent studies are reviewed indicating that the transcription factor early growth response-1 (Egr1) is a direct regulator of multiple tumor suppressors including TGFbeta1, PTEN, p53, and fibronectin. The downstream pathways of these factors display multiple nodes of interaction with each other, suggesting the existence of a functional network of suppressor factors that serve to maintain normal growth regulation and resist the emergence of transformed variants. Paradoxically, Egr1 is oncogenic in prostate cancer. In the majority of these cancers, PTEN or p53 is inactive. It is suggested that these defects in the suppressor network allow for the unopposed induction of TGFbeta1 and fibronectin, which favor transformation and survival of prostate tumor epithelial cells, and explain the role of Egr1 in prostate cancer. Egr1 is a novel and logical target for intervention by gene therapy methods, and targeting methods are discussed.
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Affiliation(s)
| | | | | | | | - Dan Mercola
- The Burnham Institute, La Jolla, CA 92037
- The Rebecca and John Moores Cancer Center, University of California at San Diego, La Jolla, CA 92093
- The Department of Pathology, University of California at Irvine, Irvine, CA 92697
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Croushore JA, Blasiole B, Riddle RC, Thisse C, Thisse B, Canfield VA, Robertson GP, Cheng K, Levenson R. Ptena and ptenb genes play distinct roles in zebrafish embryogenesis. Dev Dyn 2006; 234:911-21. [PMID: 16193492 PMCID: PMC2611959 DOI: 10.1002/dvdy.20576] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
PTEN is a tumor suppressor gene associated with multiple tumor types. PTEN function is essential for early embryonic development and is involved in the regulation of cell size, number, and survival. By dephosphorylating PIP(3), PTEN normally acts to inhibit the PI3-Kinase/AKT pathway. Here we have identified two zebrafish orthologs, ptena and ptenb, of the single mammalian PTEN gene and analyzed the role of these genes in zebrafish development. Ptena transcripts were expressed throughout the embryo at early somitogenesis. By 24 hpf, expression was predominant in the central nervous system, axial vasculature, retina, branchial arches, ear, lateral line primordium, and pectoral fin bud. Ptenb was also ubiquitously expressed early in somitogenesis, but transcripts became more restricted to the somites and central nervous system as development progressed. By 48 hpf, ptena and ptenb were expressed predominantly in the central nervous system, branchial arches, pectoral fins, and eye. Antisense morpholinos were used to knock down translation of ptena and ptenb mRNA in zebrafish embryos. Knockdown of either pten gene caused increased levels of phosphorylated Akt in morphant embryos, indicating that Ptena and Ptenb each possess PIP(3) lipid phosphatase activity. Ptena morphants had irregularities in notochord shape (73%), vasculogenesis (83%), head shape (72%), and inner ear development (59%). The most noticeable defects in ptenb morphants were upward hooked tails (73%), domed heads (83%), and reduced yolk extensions (90%). These results indicate that ptena and ptenb encode functional enzymes and that each pten gene plays a distinct role during zebrafish embryogenesis.
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Affiliation(s)
- Jessica A. Croushore
- Department of Pharmacology, Penn State University College of Medicine, Hershey, PA 17033
| | - Brian Blasiole
- Department of Pharmacology, Penn State University College of Medicine, Hershey, PA 17033
| | - Ryan C. Riddle
- Division of Musculoskeletal Sciences, Department of Orthopaedics and Rehabilitation, Penn State University College of Medicine, Hershey, PA 17033
| | - Christine Thisse
- Institute de Genetique et de Biologie Moleculaire et Cellulaire, CNRS/INSERM/ULP, CU de Strasbourg, Strasbourg, France
| | - Bernard Thisse
- Institute de Genetique et de Biologie Moleculaire et Cellulaire, CNRS/INSERM/ULP, CU de Strasbourg, Strasbourg, France
| | - Victor A. Canfield
- Department of Pharmacology, Penn State University College of Medicine, Hershey, PA 17033
| | - Gavin P. Robertson
- Department of Pharmacology, Penn State University College of Medicine, Hershey, PA 17033
| | - Keith Cheng
- Pathology and Jake Gittlen Cancer Research Institute, Penn State University College of Medicine, Hershey, PA 17033
| | - Robert Levenson
- Department of Pharmacology, Penn State University College of Medicine, Hershey, PA 17033
- Corresponding Author, Department of Pharmacology, H078, Hershey, PA 17033, Tel. (717) 531-4545, Fax: (717) 531-5013,
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Mahimainathan L, Das F, Venkatesan B, Choudhury GG. Mesangial cell hypertrophy by high glucose is mediated by downregulation of the tumor suppressor PTEN. Diabetes 2006; 55:2115-25. [PMID: 16804083 DOI: 10.2337/db05-1326] [Citation(s) in RCA: 125] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Diabetic nephropathy is characterized early in its course by glomerular hypertrophy and, importantly, mesangial hypertrophy, which correlate with eventual glomerulosclerosis. The mechanism of hypertrophy, however, is not known. Gene disruption of the tumor suppressor PTEN, a negative regulator of the phosphatidylinositol 3-kinase/Akt pathway, in fruit flies and mice demonstrated its role in size control in a cell-specific manner. Here, we investigated the mechanism of mesangial hypertrophy in response to high extracellular glucose. We link early renal hypertrophy with significant reduction in PTEN expression in the streptozotocin-induced diabetic kidney cortex and glomeruli, concomitant with activation of Akt. Similarly, exposure of mesangial cells to high concentrations of glucose also decreased PTEN expression and its phosphatase activity, resulting in increased Akt activity. Expression of PTEN inhibited high-glucose-induced mesangial cell hypertrophy, and expression of dominant-negative PTEN was sufficient to induce hypertrophy. In diabetic nephropathy, the hypertrophic effect of hyperglycemia is thought to be mediated by transforming growth factor-beta (TGF-beta). TGF-beta significantly reduced PTEN expression in mesangial cells, with a reduction in its phosphatase activity and an increase in Akt activation. PTEN and dominant-negative Akt attenuated TGF-beta-induced hypertrophy of mesangial cells. Finally, we show that inhibition of TGF-beta signal transduction blocks the effect of high glucose on PTEN downregulation. These data identify a novel mechanism placing PTEN as a key regulator of diabetic mesangial hypertrophy involving TGF-beta signaling.
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Affiliation(s)
- Lenin Mahimainathan
- Department of Medicine, Mail Code 7882, 7703 Floyd Curl Dr., San Antonio, Texas 78229-3900, USA
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Chalhoub N, Kozma SC, Baker SJ. S6k1 is not required for Pten-deficient neuronal hypertrophy. Brain Res 2006; 1100:32-41. [PMID: 16777079 DOI: 10.1016/j.brainres.2006.05.013] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2006] [Revised: 05/02/2006] [Accepted: 05/04/2006] [Indexed: 10/24/2022]
Abstract
The tumor suppressor PTEN (phosphatase and tensin homolog) plays a critical role in the development and maintenance of the mammalian nervous system. Effects of inherited mutation of PTEN are highly variable and include macrocephaly, Lhermitte-Duclos disease (LDD) caused by a hamartomatous enlargement of the cerebellum, ataxia, seizures and autism, in addition to cancer predisposition. In the mouse, selective inactivation of Pten in post-mitotic granule neurons of the cerebellum and dentate gyrus showed that Pten was required for proper regulation of neuronal nuclear and soma size. Hypertrophy of Pten-deficient neurons required the activity of the serine-threonine kinase mTor. mTor is a master regulator of cell and organ growth which can trigger a cascade of downstream signaling pathways involving, in part, components of the translational machinery, including S6k1 and its substrate the ribosomal protein S6. Deletion of S6k1 in mice results in decreased size. Therefore, to determine the relative contribution of S6k1 to Pten-deficient neuronal hypertrophy in vivo, we crossed Pten brain-conditional knockouts with S6k1 null mice. Double mutant mice show no reversion or improvement in their Pten-related size and neurological defects including enlarged cerebella and dentate gyri with increased size of neuronal nuclei and somata, ataxia, and premature death. The hypertrophic Pten/S6k1-deficient neurons contained high levels of phosphorylated S6, similar to Pten-deficient neurons, suggesting that the mTor/S6k/S6 branch of the pathway was still active. Thus, we conclude that S6k1 is not required to cause hypertrophy of Pten-deficient neurons. This study reveals a cell type-dependent role for S6k1 in PI3K-dependent hypertrophy.
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Affiliation(s)
- Nader Chalhoub
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, 332 North Lauderdale, Memphis, TN 38105, USA
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65
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Ueno S, Kono R, Iwao Y. PTEN is required for the normal progression of gastrulation by repressing cell proliferation after MBT in Xenopus embryos. Dev Biol 2006; 297:274-83. [PMID: 16919259 DOI: 10.1016/j.ydbio.2006.06.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2006] [Revised: 05/30/2006] [Accepted: 06/01/2006] [Indexed: 11/16/2022]
Abstract
PTEN phosphatase mediates several developmental cues involving cell proliferation, growth, death, and migration. We investigated the function of the PTEN gene at the transition from the cell proliferation state to morphogenesis around the midblastula transition (MBT) and gastrulation in Xenopus embryos. An immunoblotting analysis indicated that PTEN expresses constantly through embryogenesis. By up- or down-regulating PTEN activity using overexpression of the active form or C terminus of PTEN before MBT, we induced elongation of the cell cycle time just before MBT or maintained its speed even after MBT, respectively. The disruption of the cell cycle time by changing the activity of PTEN delayed gastrulation after MBT. In addition, PTEN began to localize to the plasma membranes and nuclei at MBT. Overexpression of a membrane-localizing mutant of PTEN caused dephosphorylation of Akt, whereas overexpression of the C terminus of PTEN caused phosphorylation of Akt and inhibited the localization of EGFP-PTEN to the plasma membranes and nuclei. These results indicate that an appropriate PTEN activity, probably regulated by its differential localization, is necessary for coordinating cell proliferation and early morphogenesis.
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Affiliation(s)
- Shuichi Ueno
- Department of Biological Science, Faculty of Science, Yamaguchi University, 753-8512 Yamaguchi, Japan.
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66
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Gustin JA, Korgaonkar CK, Pincheira R, Li Q, Donner DB. Akt regulates basal and induced processing of NF-kappaB2 (p100) to p52. J Biol Chem 2006; 281:16473-81. [PMID: 16613850 DOI: 10.1074/jbc.m507373200] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
NF-kappaB is a family of transcription factors important for innate and adaptive immunity. NF-kappaB is restricted to the cytoplasm by inhibitory proteins that are degraded when specifically phosphorylated, permitting NF-kappaB to enter the nucleus and activate target genes. Phosphorylation of the inhibitory proteins is mediated by an IkappaB kinase (IKK) complex, which can be composed of two subunits with enzymatic activity, IKKalpha and IKKbeta. The preferred substrate for IKKbeta is IkappaBalpha, degradation of which liberates p65 (RelA) to enter the nucleus where it induces genes important to innate immunity. IKKalpha activates a non-canonical NF-kappaB pathway in which p100 (NF-kappaB2) is processed to p52. Once produced, p52 can enter the nucleus and induce genes important to adaptive immunity. This study shows that Akt binds to and increases the activity of IKKalpha and thereby increases p52 production in cells. Constitutively active Akt augments non-canonical NF-kappaB activity, whereas kinase dead Akt or inhibition of phosphatidylinositol 3-kinase have the opposite effect. Basal and ligand-induced p52 production is reduced in mouse embryo fibroblasts deficient in Akt1 and Akt2 compared with parental cells. These observations show that Akt plays a role in activation of basal and induced non-canonical NF-kappaB activity.
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Affiliation(s)
- Jason A Gustin
- Department of Microbiology and Immunology and Walther Oncology Center, Indiana University School of Medicine, Indianapolis, IN 46202, USA
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67
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Abstract
Mutations of the tumour suppressor PTEN (phosphatase and tensin homolog deleted on chromosome 10) are seen in many human cancers. However, dysregulation of PTEN may be involved in other disease states such as Parkinson's disease. This minireview describes recent work examining PTEN regulation and its implications for the development of both cancer and neurodegenerative disease.
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Affiliation(s)
- R H Kim
- Campbell Family Institute for Breast Cancer Research, Toronto, Ontario M5G 2C1, Canada
- Ontario Cancer Institute, Toronto, Ontario M5G 2C1, Canada
- Department of Medical Biophysics, University of Toronto, Toronto, Ontario M5G 2C1, Canada
| | - T W Mak
- Campbell Family Institute for Breast Cancer Research, Toronto, Ontario M5G 2C1, Canada
- Ontario Cancer Institute, Toronto, Ontario M5G 2C1, Canada
- Department of Medical Biophysics, University of Toronto, Toronto, Ontario M5G 2C1, Canada
- Campbell Family Institute for Breast Cancer Research, 620 University Avenue, Toronto, Ontario M5G 2C1, Canada; E-mail:
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68
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Boiani M, Schöler HR. Regulatory networks in embryo-derived pluripotent stem cells. Nat Rev Mol Cell Biol 2005; 6:872-84. [PMID: 16227977 DOI: 10.1038/nrm1744] [Citation(s) in RCA: 494] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Mammalian development requires the specification of over 200 cell types from a single totipotent cell. Investigation of the regulatory networks that are responsible for pluripotency in embryo-derived stem cells is fundamental to understanding mammalian development and realizing therapeutic potential. Extracellular signals and second messengers modulate cell-autonomous regulators such as OCT4, SOX2 and Nanog in a combinatorial complexity. Knowledge of this circuitry might reveal how to achieve phenotypic changes without the genetic manipulation of Oct4, Nanog and other toti/pluripotency-associated genes.
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Affiliation(s)
- Michele Boiani
- Max-Planck Institute for Molecular Biomedicine, Department of Cell and Developmental Biology, Mendelstrasse 7/Von-Esmarch Strasse 56, 48149 Münster, Germany
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Fukuda RI, Hayashi A, Utsunomiya A, Nukada Y, Fukui R, Itoh K, Tezuka K, Ohashi K, Mizuno K, Sakamoto M, Hamanoue M, Tsuji T. Alteration of phosphatidylinositol 3-kinase cascade in the multilobulated nuclear formation of adult T cell leukemia/lymphoma (ATLL). Proc Natl Acad Sci U S A 2005; 102:15213-8. [PMID: 16217039 PMCID: PMC1257720 DOI: 10.1073/pnas.0507184102] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Adult T cell leukemia/lymphoma (ATLL) has been characterized as one of the most aggressive human neoplasias and its incidence is thought to be caused by both genetic and epigenetic alterations to the host cellular genes of T cells infected with human T cell leukemia virus type I (HTLV-I). A multilobulated nuclear appearance is an important diagnostic marker of ATLL, and we have now identified that the molecular mechanisms underlying these formations occur through microtubule rearrangement via phosphatidylinositol 3-kinase (PI3-kinase) activation by AILIM/ICOS signaling. We also show that PTEN and/or SHIP-1, which are PIP3 inositol phosphatases that inhibit the activation of downstream effectors of the PI3-kinase cascade, are disrupted in both ATLL neoplasias and in multilobulated nuclei-forming Jurkat cells. This down-regulation of PTEN was found to be essential for the formation of ATLL-type nuclear lobules. Furthermore, PI3-kinase and PTEN activities were observed to be closely associated with cellular proliferation. Thus, our results suggest that alteration of PI3-kinase signaling cascades, as a result of the down-regulation of inositol phosphatases, induces ATLL-type multilobulated nuclear formation and is also associated with the cellular proliferation of malignant T cell leukemias/lymphomas.
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Affiliation(s)
- Ryu-ichi Fukuda
- Department of Biological Science and Technology, Faculty of Industrial Science and Technology, Tokyo University of Science, Noda, Chiba 278-8510, Japan
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70
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Ma X, Ziel-van der Made AC, Autar B, van der Korput HA, Vermeij M, van Duijn P, Cleutjens KB, de Krijger R, Krimpenfort P, Berns A, van der Kwast TH, Trapman J. Targeted biallelic inactivation of Pten in the mouse prostate leads to prostate cancer accompanied by increased epithelial cell proliferation but not by reduced apoptosis. Cancer Res 2005; 65:5730-9. [PMID: 15994948 DOI: 10.1158/0008-5472.can-04-4519] [Citation(s) in RCA: 143] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The PTEN tumor suppressor gene is frequently inactivated in human tumors, including prostate cancer. Based on the Cre/loxP system, we generated a novel mouse prostate cancer model by targeted inactivation of the Pten gene. In this model, Cre recombinase was expressed under the control of the prostate-specific antigen (PSA) promoter. Conditional biallelic and monoallelic Pten knock-out mice were viable and Pten recombination was prostate-specific. Mouse cohorts were systematically characterized at 4 to 5, 7 to 9, and 10 to 14 months. A slightly increased proliferation rate of epithelial cells was observed in all prostate lobes of monoallelic Pten knock-out mice (PSA-Cre;Pten-loxP/+), but minimal pathologic changes were detected. All homozygous knock-out mice (PSA-Cre;Pten-loxP/loxP) showed an increased size of the luminal epithelial cells, large areas of hyperplasia, focal prostate intraepithelial neoplasia lesions and an increased prostate weight at 4 to 5 months. More extensive prostate intraepithelial neoplasia and focal microinvasion occurred at 7 to 9 months; invasive prostate carcinoma was detected in all male PSA-Cre;Pten-loxP/loxP mice at 10 to 14 months. At 15 to 16 months, a rare lymph node metastasis was found. In hyperplastic cells and in tumor cells, the expression of phospho-AKT was up-regulated. In hyperplastic and tumor cells, expression of luminal epithelial cell cytokeratins was up-regulated; tumor cells were negative for basal epithelial cell cytokeratins. Androgen receptor expression remained detectable at all stages of tumor development. The up-regulation of phospho-AKT correlated with an increased proliferation rate of the epithelial cells, but not with a reduced apoptosis.
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Affiliation(s)
- Xiaoqian Ma
- Department of Pathology, Josephine Nefkens Institute, Erasmus Medical Center, Rotterdam, Netherlands
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71
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Zhang J, Mruk DD, Cheng CY. Myotubularin phosphoinositide phosphatases, protein phosphatases, and kinases: their roles in junction dynamics and spermatogenesis. J Cell Physiol 2005; 204:470-83. [PMID: 15690393 DOI: 10.1002/jcp.20303] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Spermatogenesis in the seminiferous epithelium of the mammalian testis is a dynamic cellular event. It involves extensive restructuring at the Sertoli-germ cell interface, permitting germ cells to traverse the epithelium from basal to adluminal compartment. As such, Sertoli-germ cell actin-based adherens junctions (AJ), such as ectoplasmic specializations (ES), must disassemble and reassemble to facilitate this event. Recent studies have shown that AJ dynamics are regulated by intricate interactions between AJ integral membrane proteins (e.g., cadherins, alpha6beta1 integrins and nectins), phosphatases, kinases, adaptors, and the underlying cytoskeleton network. For instance, the myotubularin (MTM) phosphoinositide (PI) phosphatases, such as MTM related protein 2 (MTMR2), can form a functional complex with c-Src (a non-receptor protein tyrosine kinase). In turn, this phosphatase/kinase complex associates with beta-catenin, a constituent of the N-cadherin/beta-catenin functional unit at the AJ site. This MTMR2-c-Src-beta-catenin complex apparently regulates the phosphorylation status of beta-catenin, which determines cell adhesive function conferred by the cadherin-catenin protein complex in the seminiferous epithelium. In this review, we discuss the current status of research on selected phosphatases and kinases, and how these proteins potentially interact with adaptors at AJ in the seminiferous epithelium to regulate cell adhesion in the testis. Specific research areas that are open for further investigation are also highlighted.
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Affiliation(s)
- Jiayi Zhang
- Population Council, Center for Biomedical Research, New York, New York, USA
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72
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Doxey BW, Kuwada SK, Burt RW. Inherited polyposis syndromes: molecular mechanisms, clinicopathology, and genetic testing. Clin Gastroenterol Hepatol 2005; 3:633-41. [PMID: 16206494 DOI: 10.1016/s1542-3565(05)00370-8] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The inherited polyposis syndromes are a group of conditions in which multiple gastrointestinal polyps occur in the lumen of the gastrointestinal tract, most exhibit an increased risk of colon cancer. Benign and malignant extraintestinal tumors might also be observed. Recent elucidation of the underlying gene mutations has contributed to our understanding of the cell biology and molecular mechanisms associated with gastrointestinal tumorigenesis. Developments have also allowed genetic testing to become an integral component in accurate diagnosis, categorization, and management of inherited polyposis syndromes. In this review, we will focus on familial adenomatous polyposis, mutY human homologue-associated polyposis, Peutz-Jeghers syndrome, juvenile polyposis, and Cowden syndrome. It is essential that both physician and patient understand the benefits and limitations of genetic testing before submission of samples to the laboratory. There are many issues accompanying molecular diagnosis of cancer syndromes, and genetic counseling is an essential prelude to genetic testing.
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Affiliation(s)
- Brett W Doxey
- Division of Gastroenterology, University of Utah Health Sciences Center, USA
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73
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Abstract
The phosphoinositide 3-kinase (PI3K)/Akt signaling axis plays an important role in cellular proliferation and growth signaling. With respect to the immune system, a growing body of data is helping to elucidate the role of this pathway in lymphocyte development, as well as to show how perturbations that lead to unregulated activation in this pathway may produce systemic autoimmunity or malignancy. Various knockout and transgenic murine models have been described for key mediators of this signaling pathway. Many of these models resulting in the activation of this pathway demonstrate features of systemic autoimmunity, linking this pathway to autoimmune disease. Here, we review recently described murine models that exhibit activated PI3K/Akt signaling and the potential role this pathway in autoimmune disease, and also discuss the therapeutic implications of these findings.
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Affiliation(s)
- Rahul K Patel
- Department of Rheumatology, UT Southwestern Medical Center at Dallas, Dallas, TX 75390-8884, USA
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74
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Wijesekara N, Konrad D, Eweida M, Jefferies C, Liadis N, Giacca A, Crackower M, Suzuki A, Mak TW, Kahn CR, Klip A, Woo M. Muscle-specific Pten deletion protects against insulin resistance and diabetes. Mol Cell Biol 2005; 25:1135-45. [PMID: 15657439 PMCID: PMC544010 DOI: 10.1128/mcb.25.3.1135-1145.2005] [Citation(s) in RCA: 192] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Pten (phosphatase with tensin homology), a dual-specificity phosphatase, is a negative regulator of the phosphoinositide 3-kinase (PI3K)/Akt signaling pathway. Pten regulates a vast array of biological functions including growth, metabolism, and longevity. Although the PI3K/Akt pathway is a key determinant of the insulin-dependent increase in glucose uptake into muscle and adipose cells, the contribution of this pathway in muscle to whole-body glucose homeostasis is unclear. Here we show that muscle-specific deletion of Pten protected mice from insulin resistance and diabetes caused by high-fat feeding. Deletion of muscle Pten resulted in enhanced insulin-stimulated 2-deoxyglucose uptake and Akt phosphorylation in soleus but, surprisingly, not in extensor digitorum longus muscle compared to littermate controls upon high-fat feeding, and these mice were spared from developing hyperinsulinemia and islet hyperplasia. Muscle Pten may be a potential target for treatment or prevention of insulin resistance and diabetes.
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Affiliation(s)
- Nadeeja Wijesekara
- Programme in Cell Biology, The Hospital for Sick Children, Toronto, Ontario, Canada M5G 2N9
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75
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Puc J, Keniry M, Li HS, Pandita TK, Choudhury AD, Memeo L, Mansukhani M, Murty VVVS, Gaciong Z, Meek SEM, Piwnica-Worms H, Hibshoosh H, Parsons R. Lack of PTEN sequesters CHK1 and initiates genetic instability. Cancer Cell 2005; 7:193-204. [PMID: 15710331 DOI: 10.1016/j.ccr.2005.01.009] [Citation(s) in RCA: 264] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/26/2004] [Revised: 01/18/2005] [Accepted: 01/19/2005] [Indexed: 11/20/2022]
Abstract
Pten-/- cells display a partially defective checkpoint in response to ionizing radiation (IR). The checkpoint defect was traced to the ability of AKT to phosphorylate CHK1 at serine 280, since a nonphosphorylated mutant of CHK1 (S280A) complemented the checkpoint defect and restored CDC25A degradation. CHK1 phosphorylation at serine 280 led to covalent binding of 1 to 2 molecules of ubiquitin and cytoplasmic CHK1 localization. Primary breast carcinomas lacking PTEN expression and having elevated AKT phosphorylation had increased cytoplasmic CHK1 and displayed aneuploidy (p <0.005). We conclude that loss of PTEN and subsequent activation of AKT impair CHK1 through phosphorylation, ubiquitination, and reduced nuclear localization to promote genomic instability in tumor cells.
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Affiliation(s)
- Janusz Puc
- Institute for Cancer Genetics, Columbia University, New York, New York 10032, USA
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76
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Abstract
Phosphoinositide 3-kinase (PI3K) activation is essential for lymphocyte proliferation driven by receptors for antigen, costimulatory ligands and cytokines. The lipid products of PI3K contribute to the assembly of membrane-associated signaling complexes by promoting recruitment of selected proteins from the cytoplasm. Many proteins possess domains that are able to bind selectively to PI3K products. Different 'PI3K effector' proteins are coupled to distinct biological responses, depending on cell type and on the receptor that is engaged. In B cells and T cells, Tec-family tyrosine kinases and Akt serine/threonine kinases are emerging as crucial mediators of proliferation and survival signals downstream of PI3K. Of particular interest is recent evidence that PI3K signaling controls increases in lymphocyte size and metabolic activity that accompany cell cycle progression.
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Affiliation(s)
- David A Fruman
- University of California, Irvine, Department of Molecular Biology and Biochemistry, 3242 McGaugh Hall, Irvine, California 92697-3900, USA.
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77
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Santos NC, Martins-Silva J, Saldanha C. PTEN "meets" DMSO. Leuk Res 2005; 29:361-2. [PMID: 15725467 DOI: 10.1016/j.leukres.2004.09.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2004] [Accepted: 09/30/2004] [Indexed: 12/26/2022]
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78
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Kimura T, Murayama K, Nakamura T, Watanabe S, Umehara H, Tomooka M, Nakano T. Testicular teratomas: back to pluripotent stem cells. PROGRESS IN MOLECULAR AND SUBCELLULAR BIOLOGY 2005; 40:133-50. [PMID: 17153483 DOI: 10.1007/3-540-27671-8_6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Affiliation(s)
- Tohru Kimura
- Department of Pathology, Osaka University Medical School, Japan
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79
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Cully M, Elia A, Ong SH, Stambolic V, Pawson T, Tsao MS, Mak TW. grb2 heterozygosity rescues embryonic lethality but not tumorigenesis in pten+/- mice. Proc Natl Acad Sci U S A 2004; 101:15358-63. [PMID: 15492213 PMCID: PMC524460 DOI: 10.1073/pnas.0406613101] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
PTEN is a tumor suppressor gene implicated in both sporadic cancers and inherited tumor-prone syndromes. Here we show that pten+/- mice display a partially penetrant embryonic lethality. This lethality is associated with defects in both neural and placental development. Notably, this lethality is completely rescued by grb2 haploinsufficiency. In contrast, grb2 heterozygosity did not alter tumorigenesis in either pten+/- or T cell-specific pten-/- mice. grb2-/hypomorph murine embryonic fibroblasts (MEFs) show decreased activation of both PKB and Erk upon stimulation with epidermal growth factor, whereas grb2-/hypomorph; pten+/- MEFs activate PKB but not Erk normally. Similarly, grb2-/hypomorph fibroblasts die in low serum, and this phenotype is rescued by pten haploinsufficiency. Activation of both PKB and Erk as well as survival in low serum-containing media are all rescued by reexpression of Grb2 containing mutations within the N-terminal Src homology 3 (SH3) domain, but not by C-terminal SH3 domain mutants. The N-terminal SH3 domain mutants fail to bind to Sos, whereas the C-terminal SH3 domain mutants fail to bind to Gab1, suggesting that Erk and PKB activation in fibroblasts in response to epidermal growth factor depends on Gab1 or other C-terminal SH3 domain-interacting proteins, but not on Sos. Thus, PTEN/phosphatidylinositol 3' kinase signaling requires Grb2 during both embryonic development and fibroblast survival, but Grb2 heterozygosity does not effect tumorigenesis in pten-deficient mice. In fibroblasts, survival signals emanating from the epidermal growth factor receptor appear to be PKB-dependent, and this activation depends on the C-terminal SH3 domain of Grb2, likely through the interaction of Grb2 with Gab1.
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Affiliation(s)
- Megan Cully
- Department of Medical Biophysics, University of Toronto, Ontario Cancer Institute, Princess Margaret Hospital, 610 University Avenue, Room 7-411, Toronto, ON, Canada M5G 2M9
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80
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Donahue AC, Fruman DA. PI3K signaling controls cell fate at many points in B lymphocyte development and activation. Semin Cell Dev Biol 2004; 15:183-97. [PMID: 15209378 DOI: 10.1016/j.semcdb.2003.12.024] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Many receptors on diverse cell types activate phosphoinositide 3-kinase (PI3K). The lipid products of PI3K, termed 3-phosphoinositides, regulate numerous cellular processes by recruiting specific proteins to membrane signaling complexes. In the B lymphocyte lineage, PI3K activation is a critical control point at various stages of development, proliferation and differentiation. PI3K signaling is promoted by stimulatory receptors such as surface immunoglobulin, CD40, Toll-like receptors and cytokine receptors, and opposed by the inhibitory receptor FcgammaRIIB1. Genetic dissection of the PI3K pathway in mice has indicated that certain B cell functions are regulated by a limited set of PI3K isoforms and downstream effectors. Here we review our current understanding of how signals are relayed to and from PI3K in B cells.
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Affiliation(s)
- Amber C Donahue
- Department of Molecular Biology and Biochemistry, University of California, Irvine, 3242 McGaugh Hall, Irvine, CA 92697-3900, USA.
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81
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Stiles B, Groszer M, Wang S, Jiao J, Wu H. PTENless means more. Dev Biol 2004; 273:175-84. [PMID: 15328005 DOI: 10.1016/j.ydbio.2004.06.008] [Citation(s) in RCA: 184] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2003] [Revised: 06/11/2004] [Accepted: 06/11/2004] [Indexed: 12/31/2022]
Abstract
Recent studies indicate that certain key molecules that are vital for various developmental processes, such as Wnt, Shh, and Notch, cause cancer when dysregulated. PTEN, a tumor suppressor that antagonizes the PI3 kinase pathway, is the newest one on the list. The biological function of PTEN is evolutionarily conserved from C. elegans to humans, and the PTEN-controlled signaling pathway regulates cellular processes crucial for normal development, including cell proliferation, soma growth, cell death, and cell migration. In this review, we will focus on the function of PTEN in murine development and its role in regulating stem cell self-renewal and proliferation. We will summarize the organomegaly phenotypes associated with Pten tissue-specific deletion and discuss how PTEN controls organ size, a fundamental aspect of development. Last, we will review the role of PTEN in hormone-dependent, adult-onset mammary and prostate gland development.
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Affiliation(s)
- Bangyan Stiles
- Department of Molecular and Medical Pharmacology, UCLA David Geffen School of Medicine, CHS23-234, Los Angeles, CA 90095, USA
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82
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Abstract
Cells of the immune system carry out diverse functions that are controlled by surface receptors for antigen, costimulatory molecules, cytokines, chemokines, and other ligands. A shared feature of signal transduction downstream of most receptors on immune cells, as in nonhematopoietic cell types, is the activation of phosphoinositide 3-kinase (PI3K). The mechanism by which this common signaling event is elicited by distinct receptors and contributes to unique functional outcomes is an intriguing puzzle. Understanding how specificity is achieved in PI3K signaling is of particular significance because altered regulation of this pathway is observed in many disease states, including leukemia and lymphoma. Here we review recent advances in the understanding of PI3K signaling mechanisms in different immune cells and receptor systems. We emphasize the concept that PI3K and its products are components of complex networks of interacting proteins and second messengers, rather than simple links in linear signaling cascades.
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Affiliation(s)
- Jonathan A Deane
- Department of Molecular Biology and Biochemistry, University of California, Irvine, 92697, USA.
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83
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Markadieu N, Blero D, Boom A, Erneux C, Beauwens R. Phosphatidylinositol 3,4,5-trisphosphate: an early mediator of insulin-stimulated sodium transport in A6 cells. Am J Physiol Renal Physiol 2004; 287:F319-28. [PMID: 15100098 DOI: 10.1152/ajprenal.00314.2003] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Insulin stimulates sodium transport across A6 epithelial cell monolayers. Activation of phosphatidylinositol 3-kinase (PI 3-kinase) was suggested as an early step in the insulin-stimulated sodium reabsorption (Ref. 35). To establish that the stimulation of the PI 3-kinase signaling cascade is causing stimulation of apical epithelial Na channel, we added permeant forms of phosphatidylinositol (PI) phosphate (P) derivatives complexed with a histone carrier to A6 epithelium. Only PIP3and PI( 3 , 4 )P2but not PI( 4 , 5 )P2stimulated sodium transport, although each of them penetrated into A6 cell monolayers as assessed using fluorescent permeant phosphoinositides derivatives. By Western blot analysis of A6 cell extracts, the inositol 3-phosphatase PTEN and the protein kinase B PKB were both detected. To further establish that the stimulation of sodium transport induced by insulin is related to PIP3levels, we transfected A6 cells with human PTEN cDNA and observed a 30% decrease in the natriferic effect of insulin. Similarly, the increase in sodium transport observed by addition of permeant PIP3was also reduced by 30% in PTEN-overexpressing cells. PKB, a main downstream effector of PI 3-kinase, was phosphorylated at both Thr 308 and Ser 473 residues upon insulin stimulation of the A6 cell monolayer. PKB phosphorylation in response to insulin stimulation was reduced in PTEN-overexpressing cells. Permeant PIP3also increased PKB phosphorylation. Taken together, the present results establish that the d-3-phosphorylated phosphoinositides PIP3and PI( 3 , 4 )P2mediate the effect of insulin on sodium transport across A6 cell monolayers.
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Affiliation(s)
- Nicolas Markadieu
- Deptartment of Cell Physiology, Université Libre de Bruxelles, Campus Erasme, 1070 Brussels, Belgium
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84
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Horie Y, Suzuki A, Kataoka E, Sasaki T, Hamada K, Sasaki J, Mizuno K, Hasegawa G, Kishimoto H, Iizuka M, Naito M, Enomoto K, Watanabe S, Mak TW, Nakano T. Hepatocyte-specific Pten deficiency results in steatohepatitis and hepatocellular carcinomas. J Clin Invest 2004. [PMID: 15199412 DOI: 10.1172/jci200420513] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
PTEN is a tumor suppressor gene mutated in many human cancers, and its expression is reduced or absent in almost half of hepatoma patients. We used the Cre-loxP system to generate a hepatocyte-specific null mutation of Pten in mice (AlbCrePten(flox/flox) mice). AlbCrePten(flox/flox) mice showed massive hepatomegaly and steatohepatitis with triglyceride accumulation, a phenotype similar to human nonalcoholic steatohepatitis. Adipocyte-specific genes were induced in mutant hepatocytes, implying adipogenic-like transformation of these cells. Genes involved in lipogenesis and beta-oxidation were also induced, possibly as a result of elevated levels of the transactivating factors PPARgamma and SREBP1c. Importantly, the loss of Pten function in the liver led to tumorigenesis, with 47% of AlbCrePten(flox/flox) livers developing liver cell adenomas by 44 weeks of age. By 74-78 weeks of age, 100% of AlbCrePten(flox/flox) livers showed adenomas and 66% had hepatocellular carcinomas. AlbCrePten(flox/flox) mice also showed insulin hypersensitivity. In vitro, AlbCrePten(flox/flox) hepatocytes were hyperproliferative and showed increased hyperoxidation with abnormal activation of protein kinase B and MAPK. Pten is thus an important regulator of lipogenesis, glucose metabolism, hepatocyte homeostasis, and tumorigenesis in the liver.
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Affiliation(s)
- Yasuo Horie
- Department of Gastroenterology, Akita University School of Medicine, Akita, Japan
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85
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Horie Y, Suzuki A, Kataoka E, Sasaki T, Hamada K, Sasaki J, Mizuno K, Hasegawa G, Kishimoto H, Iizuka M, Naito M, Enomoto K, Watanabe S, Mak TW, Nakano T. Hepatocyte-specific Pten deficiency results in steatohepatitis and hepatocellular carcinomas. J Clin Invest 2004; 113:1774-83. [PMID: 15199412 PMCID: PMC420505 DOI: 10.1172/jci20513] [Citation(s) in RCA: 504] [Impact Index Per Article: 25.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2003] [Accepted: 04/27/2004] [Indexed: 12/13/2022] Open
Abstract
PTEN is a tumor suppressor gene mutated in many human cancers, and its expression is reduced or absent in almost half of hepatoma patients. We used the Cre-loxP system to generate a hepatocyte-specific null mutation of Pten in mice (AlbCrePten(flox/flox) mice). AlbCrePten(flox/flox) mice showed massive hepatomegaly and steatohepatitis with triglyceride accumulation, a phenotype similar to human nonalcoholic steatohepatitis. Adipocyte-specific genes were induced in mutant hepatocytes, implying adipogenic-like transformation of these cells. Genes involved in lipogenesis and beta-oxidation were also induced, possibly as a result of elevated levels of the transactivating factors PPARgamma and SREBP1c. Importantly, the loss of Pten function in the liver led to tumorigenesis, with 47% of AlbCrePten(flox/flox) livers developing liver cell adenomas by 44 weeks of age. By 74-78 weeks of age, 100% of AlbCrePten(flox/flox) livers showed adenomas and 66% had hepatocellular carcinomas. AlbCrePten(flox/flox) mice also showed insulin hypersensitivity. In vitro, AlbCrePten(flox/flox) hepatocytes were hyperproliferative and showed increased hyperoxidation with abnormal activation of protein kinase B and MAPK. Pten is thus an important regulator of lipogenesis, glucose metabolism, hepatocyte homeostasis, and tumorigenesis in the liver.
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Affiliation(s)
- Yasuo Horie
- Department of Gastroenterology, Akita University School of Medicine, Akita, Japan
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86
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Sly LM, Rauh MJ, Kalesnikoff J, Büchse T, Krystal G. SHIP, SHIP2, and PTEN activities are regulated in vivo by modulation of their protein levels: SHIP is up-regulated in macrophages and mast cells by lipopolysaccharide. Exp Hematol 2004; 31:1170-81. [PMID: 14662322 DOI: 10.1016/j.exphem.2003.09.011] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The phosphatidylinositol-3 kinase (PI3K) pathway plays a central role in regulating numerous biologic processes, including survival, adhesion, migration, metabolic activity, proliferation, differentiation, and end cell activation through the generation of the potent second messenger PI-3,4,5-trisphosphate (PI-3,4,5-P(3)). To ensure that activation of this pathway is appropriately suppressed/terminated, the ubiquitously expressed 54-kDa tumor suppressor PTEN hydrolyzes PI-3,4,5-P(3) to PI-4,5-P(2), whereas the 145-kDa hematopoietic-restricted SH2-containing inositol 5'-phosphatase SHIP (also known as SHIP1), the 104-kDa stem cell-restricted SHIP sSHIP, and the more widely expressed 150-kDa SHIP2 break it down to PI-3,4-P(2). In this review, we focus on the properties of these phospholipid phosphatases and summarize recent data showing that the activities of these negative regulators often are modulated by simply altering their protein levels. We also highlight the critical role that SHIP plays in lipopolysaccharide-induced macrophage activation and in endotoxin tolerance.
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Affiliation(s)
- Laura M Sly
- The Terry Fox Laboratory, British Columbia Cancer Agency, 601 West 10th Avenue, Vancouver, BC, V5Z 1L3, Canada
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Goberdhan DCI, Wilson C. PTEN: tumour suppressor, multifunctional growth regulator and more. Hum Mol Genet 2003; 12 Spec No 2:R239-48. [PMID: 12928488 DOI: 10.1093/hmg/ddg288] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The tumour suppressor gene PTEN is mutated in a wide range of human cancers at a frequency roughly comparable with p53. In addition, germline PTEN mutations are associated with several dominant growth disorders. The molecular and cellular basis of these disorders has been elucidated by detailed in vivo genetic analysis in model organisms, in particular the fruit fly and mouse. Studies in the fly have shown that PTEN's growth regulatory functions are primarily mediated via its lipid phosphatase activity, which specifically reduces the cellular levels of phosphatidylinositol 3,4,5-trisphosphate. This activity antagonizes the effects of activated PI3-kinase in the nutritionally controlled insulin receptor pathway, thereby reducing protein synthesis and restraining cell and organismal growth, while also regulating other biological processes, such as fertility and ageing. Remarkably, this range of functions appears to be conserved in all higher organisms. PTEN also plays a role as a specialized cytoskeletal regulator, which, for example, is involved in directional movement of some migratory cells and may be important in metastasis. Furthermore, conditional knockouts in the mouse have recently revealed functions for PTEN in other processes, such as cell type specification and cardiac muscle contractility. Genetic approaches have therefore revealed a surprising diversity of global and cell type-specific PTEN-regulated functions that appear to be primarily controlled by modulation of a single phosphoinositide. Together with evidence from studies in cell culture that suggests links between PTEN and other growth regulatory genes such as p53, these studies provide new insights into PTEN-linked disorders and are beginning to suggest potential clinical strategies to combat these and other diseases.
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Affiliation(s)
- Ji Luo
- Howard Hughes Medical Institute, USA
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