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Visnjić D, Curić J, Crljen V, Batinić D, Volinia S, Banfić H. Nuclear phosphoinositide 3-kinase C2beta activation during G2/M phase of the cell cycle in HL-60 cells. BIOCHIMICA ET BIOPHYSICA ACTA 2003; 1631:61-71. [PMID: 12573450 DOI: 10.1016/s1388-1981(02)00356-6] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The activity of nuclear phosphoinositide 3-kinase C2beta (PI3K-C2beta) was investigated in HL-60 cells blocked by aphidicolin at G(1)/S boundary and allowed to progress synchronously through the cell cycle. The activity of immunoprecipitated PI3K-C2beta in the nuclei and nuclear envelopes showed peak activity at 8 h after release from the G(1)/S block, which correlates with G(2)/M phase of the cell cycle. In the nuclei and nuclear envelopes isolated from HL-60 cells at 8 h after release from G(1)/S block, a significant increase in the level of incorporation of radiolabeled phosphate into phosphatidylinositol 3-phosphate (PtdIns(3)P) was observed with no change in the level of radiolabeled PtdIns(4)P, PtdIns(4,5)P(2) and PtdIns(3,4,5)P(3). On Western blots, PI3K-C2beta revealed a single immunoreactive band of 180 kDa, whereas in the nuclei and nuclear envelopes isolated at 8 h after release, the gel shift of 18 kDa was observed. When nuclear envelopes were treated for 20 min with mu-calpain in vitro, the similar gel shift and increase in PI3K-C2beta activity was observed which was completely inhibited by pretreatment with calpain inhibitor calpeptin. The presence of PI3K inhibitor LY 294002 completely abolished the calpain-mediated increase in the activity of PI3K-C2beta but did not prevent the gel shift. When HL-60 cells were released from G(1)/S block in the presence of either calpeptin or LY 294002, the activation of nuclear PI3K-C2beta was completely inhibited. These results demonstrate the calpain-mediated activation of the nuclear PI3K-C2beta during G(2)/M phase of the cell cycle in HL-60 cells.
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Affiliation(s)
- Dora Visnjić
- Department of Physiology and Croatian Institute for Brain Research, School of Medicine, University of Zagreb, Salata 3, 10 000, Zagreb, Croatia
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102
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Barker CJ, Leibiger IB, Leibiger B, Berggren PO. Phosphorylated inositol compounds in beta -cell stimulus-response coupling. Am J Physiol Endocrinol Metab 2002; 283:E1113-22. [PMID: 12424101 DOI: 10.1152/ajpendo.00088.2002] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Pancreatic beta-cell function is essential for the regulation of glucose homeostasis in humans, and its impairment leads to the development of type 2 diabetes. Inputs from glucose and cell surface receptors act together to initiate the beta-cell stimulus-response coupling that ultimately leads to the release of insulin. Phosphorylated inositol compounds have recently emerged as key players at all levels of the stimulus-secretion coupling process. In this current review, we seek to highlight recent advances in beta-cell phosphoinositide research by dividing our examination into two sections. The first involves the events that lead to insulin secretion. This includes both new roles for inositol polyphosphates, particularly inositol hexakisphosphate, and both conventional and 3-phosphorylated inositol lipids. In the second section, we deal with the more novel concept of the autocrine role of insulin. Here, released insulin initiates signal transduction cascades, principally through the activity of phosphatidylinositol 3-kinase. This new round of signal transduction has been established to activate key beta-cell genes, particularly the insulin gene itself. More controversially, this insulin feedback has also been suggested to either terminate or enhance insulin secretion events.
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Affiliation(s)
- Christopher J Barker
- Department of Molecular Medicine, The Rolf Luft Center for Diabetes Research, Karolinska Institutet, S-171 76 Stockholm, Sweden
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103
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Visnjić D, Crljen V, Curić J, Batinić D, Volinia S, Banfić H. The activation of nuclear phosphoinositide 3-kinase C2beta in all-trans-retinoic acid-differentiated HL-60 cells. FEBS Lett 2002; 529:268-74. [PMID: 12372612 DOI: 10.1016/s0014-5793(02)03357-4] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The activity of nuclear phosphoinositide 3-kinase C2beta (PI3K-C2beta) was investigated in HL-60 cells induced to differentiate along granulocytic or monocytic lineages. A significant increase in the activity of immunoprecipitated PI3K-C2beta was observed in the nuclei and nuclear envelopes isolated from all-trans-retinoic acid (ATRA)-differentiated cells which was inhibited by the presence of PI3K inhibitor LY 294002. High-performance liquid chromatography analysis of inositol lipids showed an increased incorporation of radiolabelled phosphate in both PtdIns(3)P and PtdIns(3,4,5)P(3) with no changes in the levels of PtdIns(4)P, PtdIns(3,4)P(2) and PtdIns(4,5)P(2). Western blot analysis of the PI3K-C2beta immunoprecipitates with anti-P-Tyr antibody revealed a significant increase in the level of the immunoreactive band corresponding to PI3K-C2beta in the nuclei and nuclear envelopes isolated from ATRA-differentiated cells.
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Affiliation(s)
- Dora Visnjić
- Department of Physiology and Croatian Institute for Brain Research, School of Medicine, University of Zagreb, Salata 3, 10000 Zagreb, Croatia
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104
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Arcaro A, Khanzada UK, Vanhaesebroeck B, Tetley TD, Waterfield MD, Seckl MJ. Two distinct phosphoinositide 3-kinases mediate polypeptide growth factor-stimulated PKB activation. EMBO J 2002; 21:5097-108. [PMID: 12356726 PMCID: PMC129034 DOI: 10.1093/emboj/cdf512] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Eight human isoforms of phosphoinositide 3-kinases (PI3Ks) exist, but their individual functions remain poorly understood. Here, we show that different human small cell lung carcinoma (SCLC) cell lines overexpress distinct subsets of class I(A) and II PI3Ks, which results in striking differences in the signalling cascades activated by stem cell factor (SCF). Over expression of class I(A) p85/p110alpha in SCLC cells increased SCF-stimulated protein kinase B (PKB) activation and cell growth, but did not affect extracellular signal-regulated kinase (Erk) or glycogen synthase kinase-3 (GSK-3). This effect was selective, since it was not observed in SCLC cell lines overexpressing p85/p110beta or p85/p110delta. The SCF receptor associated with both class I(A) p85 and class II PI3KC2beta, and both enzymes contributed to SCF-stimulated PKB activity. A dominant-negative PI3KC2beta blocked both PKB activation and SCLC cell growth in response to SCF. Together our data provide novel insights into the specificity and functional significance of PI3K signalling in human cancer.
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Affiliation(s)
- Alexandre Arcaro
- Lung Cancer Biology Group, Division of Medicine, Imperial College Faculty of Medicine, Du Cane Road, London W12 0NN,
Ludwig Institute for Cancer Research, Royal Free and University College Medical School, Riding House Street, London W1W 7BS, Department of Biochemistry and Molecular Biology, Gower Street, London WC1E 6BT and Lung Cell Biology, National Heart and Lung Institute, Imperial College Faculty of Medicine, Dovehouse Street, London SW3 6LY, UK Corresponding author e-mail:
| | | | - Bart Vanhaesebroeck
- Lung Cancer Biology Group, Division of Medicine, Imperial College Faculty of Medicine, Du Cane Road, London W12 0NN,
Ludwig Institute for Cancer Research, Royal Free and University College Medical School, Riding House Street, London W1W 7BS, Department of Biochemistry and Molecular Biology, Gower Street, London WC1E 6BT and Lung Cell Biology, National Heart and Lung Institute, Imperial College Faculty of Medicine, Dovehouse Street, London SW3 6LY, UK Corresponding author e-mail:
| | - Teresa D. Tetley
- Lung Cancer Biology Group, Division of Medicine, Imperial College Faculty of Medicine, Du Cane Road, London W12 0NN,
Ludwig Institute for Cancer Research, Royal Free and University College Medical School, Riding House Street, London W1W 7BS, Department of Biochemistry and Molecular Biology, Gower Street, London WC1E 6BT and Lung Cell Biology, National Heart and Lung Institute, Imperial College Faculty of Medicine, Dovehouse Street, London SW3 6LY, UK Corresponding author e-mail:
| | - Michael D. Waterfield
- Lung Cancer Biology Group, Division of Medicine, Imperial College Faculty of Medicine, Du Cane Road, London W12 0NN,
Ludwig Institute for Cancer Research, Royal Free and University College Medical School, Riding House Street, London W1W 7BS, Department of Biochemistry and Molecular Biology, Gower Street, London WC1E 6BT and Lung Cell Biology, National Heart and Lung Institute, Imperial College Faculty of Medicine, Dovehouse Street, London SW3 6LY, UK Corresponding author e-mail:
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105
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Paulhe F, Perret B, Chap H, Iberg N, Morand O, Racaud-Sultan C. Phosphoinositide 3-kinase C2alpha is activated upon smooth muscle cell migration and regulated by alpha(v)beta(3) integrin engagement. Biochem Biophys Res Commun 2002; 297:261-6. [PMID: 12237112 DOI: 10.1016/s0006-291x(02)02065-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The involvement of phosphoinositide 3-kinase C2alpha in vascular smooth muscle cell migration was investigated. Products of phosphoinositide 3-kinase, phosphatidylinositol-3-phosphate, and phosphatidylinositol-3,4-bis-phosphate were increased upon smooth muscle cell migration but their synthesis was affected only partially by phosphoinositide 3-kinase inhibitors, wortmannin and LY-294002. Using specific antibody, we showed that the wortmannin/LY-294002 poorly sensitive phosphoinositide 3-kinase C2alpha is expressed in smooth muscle cells. Measurement of phosphoinositide 3-kinase C2alpha activity in vitro, after immunoprecipitation, clearly demonstrated its activation upon smooth muscle cell migration. Moreover, for the first time, phosphoinositide 3-kinase C2alpha was found to be differentially regulated by alpha(v)beta(3) and alpha(v)beta(5) integrin engagement. Finally, we have identified two new potential phosphoinositide 3-kinase C2alpha-binding proteins, p70 and p110, which both may be tyrosine phosphorylated. Thus, phosphoinositide 3-kinase C2alpha might represent a new regulatory pathway of cell migration downstream of integrin engagement.
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MESH Headings
- Androstadienes/pharmacology
- Animals
- Aorta/cytology
- Cell Movement/physiology
- Cells, Cultured
- Chromones/pharmacology
- Enzyme Activation
- Humans
- Inositol 1,4,5-Trisphosphate/metabolism
- Integrin alphaVbeta3/metabolism
- Integrins/metabolism
- Isoenzymes
- Morpholines/pharmacology
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/physiology
- Phosphatidylinositol 3-Kinases/metabolism
- Phosphatidylinositol Phosphates/metabolism
- Phosphoinositide-3 Kinase Inhibitors
- Phosphorylation
- Receptors, Vitronectin/metabolism
- Signal Transduction/physiology
- Swine
- Tyrosine/metabolism
- Wortmannin
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Affiliation(s)
- Frédérique Paulhe
- Institut Fédératif de Recherche Claude de Préval, INSERM, Unité 563, Hôpital Purpan, Toulouse Cedex F31059, France
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106
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Sawano A, Takayama S, Matsuda M, Miyawaki A. Lateral propagation of EGF signaling after local stimulation is dependent on receptor density. Dev Cell 2002; 3:245-57. [PMID: 12194855 DOI: 10.1016/s1534-5807(02)00224-1] [Citation(s) in RCA: 147] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
We analyzed lateral propagation of epidermal growth factor (EGF) signaling in single live COS cells following local stimulation, achieved by the use of laminar flows containing rhodamine-labeled EGF. The spatiotemporal pattern of EGF signaling was visualized by fluorescent indicators for Ras activation and tyrosine phosphorylation. Contrary to the findings in previous reports, both signals were localized to the stimulated regions in control COS cells expressing EGF receptor at the basal level. However, the signals spread over the entire cell when EGF receptors were overexpressed or when receptor/ligand endocytosis was blocked. We thus present evidence that ligand-independent propagation of EGF signaling occurs only when the receptor density on the plasma membrane is high, such as in carcinoma cells.
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Affiliation(s)
- Asako Sawano
- Laboratory for Cell Function and Dynamics, Advanced Technology Development Center, Brain Science Institute, RIKEN, 2-1 Hirosawa, Wako-city, Saitama 351-0198, Japan
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107
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Crljen V, Volinia S, Banfic H. Hepatocyte growth factor activates phosphoinositide 3-kinase C2 beta in renal brush-border plasma membranes. Biochem J 2002; 365:791-9. [PMID: 11931646 PMCID: PMC1222704 DOI: 10.1042/bj20020316] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2002] [Revised: 03/27/2002] [Accepted: 04/03/2002] [Indexed: 01/29/2023]
Abstract
Upon stimulation of renal cortical slices with hepatocyte growth factor (HGF), inositol lipid metabolism was studied in basal-lateral plasma membranes (BLM) and brush-border plasma membranes (BBM). Whereas in BLM rapid increases in 1,2-diacylglycerol, PtdIns(3,4,5)P(3) and PtdIns(3,4)P(2) were observed, suggesting that in BLM HGF activates both phospholipase C (PLC) and phosphoinositide 3-kinase (PI3K), in BBM only HGF-induced transient accumulation of PtdIns3P was seen, which was temporarily delayed from signalling events in BLM and could be blocked by the PtdIns-specific-PLC inhibitor ET-18-OCH(3) and the calpain inhibitor calpeptin, suggesting that 3-kinase activation in BBM lies downstream of PLC activation in BLM and is a calpain-mediated event. Moreover, the increase in immunoprecipitable PI3K-C2 beta activity, which is sensitive to wortmannin (10 nM) and shows strong preference for PtdIns over PtdIns4P as a substrate, was observed only in BBM upon stimulation of renal cortical slices with HGF and could be mimicked by the Ca(2+) ionophore A23187 and blocked by the cell-penetrant Ca(2+) chelator BAPTA-AM [1,2-bis-(2-aminophenoxy)ethane-N,N,N',N'-tetra-acetic acid tetrakis(acetoxymethyl ester)]. On Western blots PI3K-C2 beta revealed a single immunoreactive band of 180 kDa in BLM and BBM, while after stimulation with HGF a gel shift of 18 kDa was noticed only in BBM, suggesting that the observed enzyme activation is achieved by proteolysis. When BBM were subjected to short-term (15 min) exposure to mu-calpain, a similar gel shift together with an increase in PI3K-C2 beta activity was observed, when compared with the BBM harvested after HGF stimulation. The above-mentioned gel shift and increase in PI3K-C2 beta activity could be prevented by the calpain inhibitor calpeptin. The data presented in this report show that in renal cells there is a spatial separation of the inositol lipid signalling system between BLM and BBM, and that HGF causes activation of PLC and PI3K primarily in BLM, which leads to calpain-mediated activation of PI3K-C2 beta in BBM with a concomitant increase in PtdIns3P.
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Affiliation(s)
- Vladiana Crljen
- Department of Physiology and Croatian Institute for Brain Research, School of Medicine, University of Zagreb, Salata 3, 10000 Zagreb, Croatia
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108
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Djordjevic S, Driscoll PC. Structural insight into substrate specificity and regulatory mechanisms of phosphoinositide 3-kinases. Trends Biochem Sci 2002; 27:426-32. [PMID: 12151228 DOI: 10.1016/s0968-0004(02)02136-9] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Phosphoinositide 3-kinases (PI3Ks) are implicated in a variety of fundamental cellular processes. These enzymes catalyse phosphorylation of the 3'-OH position of myo-inositol lipids that serve as secondary messengers. The catalytic subunit for one of the family members, PI3K gamma, has been structurally characterized, independently, in complexes with kinase inhibitors and with the p21(Ras) GTPase. These atomic structures provide a basis for the rationalization of some PI3K substrate specificities and regulatory mechanisms, establishing links to functional and cellular data. Ongoing comprehensive structural and functional studies are essential to realize the promise of PI3K isozyme-specific therapeutic agents.
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Affiliation(s)
- Snezana Djordjevic
- Bloomsbury Centre for Structural Biology and Department of Biochemistry and Molecular Biology, University College London, London, UK WC1E 6BT.
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109
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Brar BK, Stephanou A, Knight R, Latchman DS. Activation of protein kinase B/Akt by urocortin is essential for its ability to protect cardiac cells against hypoxia/reoxygenation-induced cell death. J Mol Cell Cardiol 2002; 34:483-92. [PMID: 11991736 DOI: 10.1006/jmcc.2002.1529] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Urocortin (Ucn), is a peptide related to hypothalamic corticotrophin-releasing factor (CRF) and binds with a high affinity to the CRF-R2 beta receptor which is expressed in the heart. Ucn promotes cardiac myocyte survival against hypoxia reoxygenation (HR) injury and this involves activation of the mitogen activated protein kinase pathway (MEK1/2 p42/44 MAPK). In this study we report that Ucn stimulates the phosphorylation of protein kinase B (PKB/Akt) via phosphatidylinositol (PI) 3-OH kinase (PI-3 kinase). To investigate the signalling pathways that mediate the anti-apoptotic and cell survival effect of Ucn in hypoxia reoxygenation (HR), gene based inhibitors of MEK1/2, PI-3 kinase and Akt were over-expressed in rat neonatal cardiac myocytes and cell survival effects against HR were assessed. The dominant negative mutants of the MEK1/2, PI-3 kinase and Akt inhibited Ucn mediated cardioprotection in HR and active PI-3 kinase was itself cardioprotective. In addition, chemical inhibitors of the PI-3 kinase pathway, wortmannin and LY294002 inhibit Ucn mediated cardioprotection in HR in both neonatal and adult cardiac myocytes. Hence the PI-3 kinase/Akt pathway is required in addition to MEK1/2 to mediate Ucn cardioprotection in HR. To our knowledge this is the first report of the activation of the PI-3 kinase/Akt pathway by a member of the CRF family of peptides.
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Affiliation(s)
- Bhawanjit K Brar
- Medical Molecular Biology Unit, Institute of Child Health, 30 Guilford Street, London, WC1N 1EH, UK
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110
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Vanhaesebroeck B, Leevers SJ, Ahmadi K, Timms J, Katso R, Driscoll PC, Woscholski R, Parker PJ, Waterfield MD. Synthesis and function of 3-phosphorylated inositol lipids. Annu Rev Biochem 2002; 70:535-602. [PMID: 11395417 DOI: 10.1146/annurev.biochem.70.1.535] [Citation(s) in RCA: 1211] [Impact Index Per Article: 55.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The 3-phosphorylated inositol lipids fulfill roles as second messengers by interacting with the lipid binding domains of a variety of cellular proteins. Such interactions can affect the subcellular localization and aggregation of target proteins, and through allosteric effects, their activity. Generation of 3-phosphoinositides has been documented to influence diverse cellular pathways and hence alter a spectrum of fundamental cellular activities. This review is focused on the 3-phosphoinositide lipids, the synthesis of which is acutely triggered by extracellular stimuli, the enzymes responsible for their synthesis and metabolism, and their cell biological roles. Much knowledge has recently been gained through structural insights into the lipid kinases, their interaction with inhibitors, and the way their 3-phosphoinositide products interact with protein targets. This field is now moving toward a genetic dissection of 3-phosphoinositide action in a variety of model organisms. Such approaches will reveal the true role of the 3-phosphoinositides at the organismal level in health and disease.
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Affiliation(s)
- B Vanhaesebroeck
- Ludwig Institute for Cancer Research, Riding House Street, London W1W 7BS.
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111
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Katso R, Okkenhaug K, Ahmadi K, White S, Timms J, Waterfield MD. Cellular function of phosphoinositide 3-kinases: implications for development, homeostasis, and cancer. Annu Rev Cell Dev Biol 2002; 17:615-75. [PMID: 11687500 DOI: 10.1146/annurev.cellbio.17.1.615] [Citation(s) in RCA: 929] [Impact Index Per Article: 42.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The phosphoinositide 3-kinase (PI3K) family of enzymes is recruited upon growth factor receptor activation and produces 3' phosphoinositide lipids. The lipid products of PI3K act as second messengers by binding to and activating diverse cellular target proteins. These events constitute the start of a complex signaling cascade, which ultimately results in the mediation of cellular activities such as proliferation, differentiation, chemotaxis, survival, trafficking, and glucose homeostasis. Therefore, PI3Ks play a central role in many cellular functions. The factors that determine which cellular function is mediated are complex and may be partly attributed to the diversity that exists at each level of the PI3K signaling cascade, such as the type of stimulus, the isoform of PI3K, or the nature of the second messenger lipids. Numerous studies have helped to elucidate some of the key factors that determine cell fate in the context of PI3K signaling. For example, the past two years has seen the publication of many transgenic and knockout mouse studies where either PI3K or its signaling components are deregulated. These models have helped to build a picture of the role of PI3K in physiology and indeed there have been a number of surprises. This review uses such models as a framework to build a profile of PI3K function within both the cell and the organism and focuses, in particular, on the role of PI3K in cell regulation, immunity, and development. The evidence for the role of deregulated PI3K signaling in diseases such as cancer and diabetes is reviewed.
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Affiliation(s)
- R Katso
- Ludwig Institute for Cancer Research, 91 Riding House Street, London, W1W 7BS, England.
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112
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Didichenko SA, Thelen M. Phosphatidylinositol 3-kinase c2alpha contains a nuclear localization sequence and associates with nuclear speckles. J Biol Chem 2001; 276:48135-42. [PMID: 11606566 DOI: 10.1074/jbc.m104610200] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Phosphoinositide 3-kinase C2alpha (PI3K-C2alpha) belongs to the class II phosphatidylinositol 3-kinases, which are defined by their in vitro usage of phosphatidylinositol and phosphatidylinositol 4-phosphate as substrates. All type II phosphatidylinositol 3-kinases contain at their C terminus a C2-like domain. Here we demonstrate that Homo sapiens phosphoinositide 3-kinase C2alpha (HsPI3K-C2alpha) has dual cellular localization present in the cytoplasm and in the nucleus. A distinct nuclear localization signal sequence was identified by expressing HsPI3K-C2alpha-green fluorescent protein fusion proteins in HeLa cells. The nuclear localization signal was mapped to a stretch of 11 amino acids (KRKTKISRKTR) located within C2-like domain of the kinase. In the cytoplasm and the nucleus HsPI3K-C2alpha associates with macromolecular complexes that are resistant to detergent extraction. Indirect immunofluorescence reveals that in the nucleus HsPI3K-C2alpha is enriched at distinct subnuclear domains known as nuclear speckles, which contain pre-mRNA processing factors and are functionally connected to RNA metabolism. Phosphorylation of HsPI3K-C2alpha is induced by inhibition of RNA polymerase II-dependent transcription and coincides with enlargement and rounding up of the nuclear speckles. The results suggest that phosphorylation of HsPI3K-C2alpha is inversely linked to mRNA transcription and supports the importance of phosphoinositides for nuclear activity.
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Affiliation(s)
- S A Didichenko
- Institute for Research in Biomedicine, Via Vincenzo Vela 6, CH 6500 Bellinzona, Switzerland
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113
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Sato TK, Overduin M, Emr SD. Location, location, location: membrane targeting directed by PX domains. Science 2001; 294:1881-5. [PMID: 11729306 DOI: 10.1126/science.1065763] [Citation(s) in RCA: 181] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Phosphoinositide (PI)-binding domains play critical roles in the intracellular localization of a variety of cell-signaling proteins. The 120-amino acid Phox homology (PX) domain targets proteins to organelle membranes through interactions between two conserved basic motifs within the PX domain and specific PIs. The combination of protein-lipid and protein-protein interactions ensures the proper localization and regulation of PX domain-containing proteins. Upon proper localization, PX domain-containing proteins can then bind to additional proteins and execute their functions in a diverse set of biological pathways, including intracellular protein transport, cell growth and survival, cytoskeletal organization, and neutrophil defense.
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Affiliation(s)
- T K Sato
- Department of Cellular and Molecular Medicine and Howard Hughes Medical Institute, University of California at San Diego School of Medicine, La Jolla, CA 92093-0668, USA
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114
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Wheeler M, Domin J. Recruitment of the class II phosphoinositide 3-kinase C2beta to the epidermal growth factor receptor: role of Grb2. Mol Cell Biol 2001; 21:6660-7. [PMID: 11533253 PMCID: PMC99811 DOI: 10.1128/mcb.21.19.6660-6667.2001] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Previously we demonstrated that the class II phosphoinositide 3-kinase C2beta (PI3K-C2beta) is rapidly recruited to a phosphotyrosine signaling complex containing the activated receptor for epidermal growth factor (EGF). Although this association was shown to be dependent upon specific phosphotyrosine residues present on the EGF receptor, the underlying mechanism remained unclear. In this study the interaction between PI3K-C2beta and the EGF receptor is competitively attenuated by synthetic peptides derived from each of three proline-rich motifs present within the N-terminal region of the PI3K. Further, a series of N-terminal PI3K-C2beta fragments, truncated prior to each proline-rich region, bound the receptor with decreased efficiency. A single proline-rich region was unable to mediate receptor association. Finally, an equivalent N-terminal fragment of PI3K-C2alpha that lacks similar proline-rich motifs was unable to affinity purify the activated EGF receptor from cell lysates. Since these findings revealed that the interaction between the EGF receptor and PI3K-C2beta is indirect, we sought to identify an adaptor molecule that could mediate their association. In addition to the EGF receptor, PI3K-C2beta(2-298) also isolated both Shc and Grb2 from A431 cell lysates. Recombinant Grb2 directly bound PI3K-C2beta in vitro, and this effect was reproduced using either SH3 domain expressed as a glutathione S-transferase (GST) fusion. Interaction with Grb2 dramatically increased the catalytic activity of this PI3K. The relevance of this association was confirmed when PI3K-C2beta was isolated by coimmunoprecipitation with anti-Grb2 antibody from numerous cell lines. Using immobilized, phosphorylated EGF receptor, recombinant PI3K-C2beta was only purified in the presence of Grb2. We conclude that proline-rich motifs within the N terminus of PI3K-C2beta mediate the association of this enzyme with activated EGF receptor and that this interaction involves the Grb2 adaptor.
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Affiliation(s)
- M Wheeler
- Division of Medicine, Imperial College School of Medicine, London W12 0NN, United Kingdom
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115
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Abstract
Phosphoinositides serve as intrinsic membrane signals that regulate intracellular membrane trafficking. Recently, phosphoinositides have been found to direct the localization and activity of effector proteins containing consensus sequence motifs such as FYVE, PH and ENTH domains. In addition, recent results show that regulated synthesis and turnover of phosphoinositides by membrane-associated phosphoinoside kinases and phosphatases spatially restrict the location of effectors critical for cellular transport processes, such as clathrin-mediated endocytosis, autophagy, phagocytosis, macropinocytosis and biosynthetic trafficking.
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Affiliation(s)
- A Simonsen
- Department of Biochemistry, Institute for Cancer Research, the Norwegian Radium Hospital, Montebello, N-0310, Oslo, Norway
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116
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Stoll SW, Kansra S, Peshick S, Fry DW, Leopold WR, Wiesen JF, Sibilia M, Zhang T, Werb Z, Derynck R, Wagner EF, Elder JT. Differential utilization and localization of ErbB receptor tyrosine kinases in skin compared to normal and malignant keratinocytes. Neoplasia 2001; 3:339-50. [PMID: 11571634 PMCID: PMC1505868 DOI: 10.1038/sj.neo.7900170] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2001] [Indexed: 11/08/2022] Open
Abstract
Induction of heparin-binding epidermal growth factor-like growth factor (HB-EGF) mRNA in mouse skin organ culture was blocked by two pan-ErbB receptor tyrosine kinase (RTK) inhibitors but not by genetic ablation of ErbB1, suggesting involvement of multiple ErbB species in skin physiology. Human skin, cultured normal keratinocytes, and A431 skin carcinoma cells expressed ErbB1, ErbB2, and ErbB3, but not ErbB4. Skin and A431 cells expressed more ErbB3 than did keratinocytes. Despite strong expression of ErbB2 and ErbB3, heregulin was inactive in stimulating tyrosine phosphorylation in A431 cells. In contrast, it was highly active in MDA-MB-453 breast carcinoma cells. ErbB2 displayed punctate cytoplasmic staining in A431 and keratinocytes, compared to strong cell surface staining in MDA-MB-453. In skin, ErbB2 was cytoplasmic in basal keratinocytes, assuming a cell surface pattern in the upper suprabasal layers. In contrast, ErbB1 retained a cell surface distribution in all epidermal layers. Keratinocyte proliferation in culture was found to be ErbB1-RTK-dependent, using a selective inhibitor. These results suggest that in skin keratinocytes, ErbB2 transduces ligand-dependent differentiation signals, whereas ErbB1 transduces ligand-dependent proliferation/survival signals. Intracellular sequestration of ErbB2 may contribute to the malignant phenotype of A431 cells, by allowing them to respond to ErbB1-dependent growth/survival signals, while evading ErbB2-dependent differentiation signals.
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MESH Headings
- Animals
- Blotting, Northern
- Enzyme Inhibitors/pharmacology
- ErbB Receptors/antagonists & inhibitors
- ErbB Receptors/metabolism
- Fluorescent Antibody Technique
- Heparin/metabolism
- Humans
- Keratinocytes/drug effects
- Keratinocytes/metabolism
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Organ Culture Techniques
- Quinazolines/pharmacology
- RNA/metabolism
- Receptor, ErbB-2/antagonists & inhibitors
- Receptor, ErbB-2/metabolism
- Receptor, ErbB-3/antagonists & inhibitors
- Receptor, ErbB-3/metabolism
- Receptor, ErbB-4
- Signal Transduction
- Skin Neoplasms/metabolism
- Tumor Cells, Cultured/drug effects
- Tumor Cells, Cultured/metabolism
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Affiliation(s)
- S W Stoll
- Department of Dermatology, University of Michigan Medical Center, 1500 East Medical CenterDrive, Ann Arbor, MI 48109, USA
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117
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Abstract
Over the past ten years, our knowledge of the integral role that the phospho-inositide 3-kinases (PI3Ks) and their 3'-phosphorylated lipid products (3'-phosphorylated phosphoinositides; 3P-PIs) play in the mediation of signal transduction, cytoskeletal rearrangements and membrane trafficking has expanded considerably. They are now known to be involved in the regulation of cell growth, differentiation, mobility, proliferation and survival and hence they have become a potential target for the control of the growth and spread of cancer cells. More recently, the correlation of the multiplicity of isomers (both catalytic and regulatory) within the different classes of the PI3Ks with their functional relevance has become possible. This, combined with our further understanding of the protein recognition patterns for their different 3P-PIs and the newly-described pathways in the control of the levels of these by dephosphorylation, has provided new aspects and areas for interference in these multiple PI3K signalling pathways. However, in the search for effective, non-toxic, drugs for use in the treatment of cancers, these individual targets for PI3K inhibition need to be further correlated with the specific in vivo effects on cell survival, invasivity and metastatic potential. Here, the range of PI3K inhibition targets are discussed in the light of recent experimental findings, with a view to the exploitation of their specificities in new approaches to effective cancer treatments based on PI3K activity inhibition.
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Affiliation(s)
- C P Berrie
- Department of Cell Biology and Oncology, Istituto di Ricerche Farmacologiche Mario Negri, Consorzio Mrio Negri Sud, Santa Maria Imbaro, Chieti, Italy.
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118
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Lu Z, Jiang G, Blume-Jensen P, Hunter T. Epidermal growth factor-induced tumor cell invasion and metastasis initiated by dephosphorylation and downregulation of focal adhesion kinase. Mol Cell Biol 2001; 21:4016-31. [PMID: 11359909 PMCID: PMC87064 DOI: 10.1128/mcb.21.12.4016-4031.2001] [Citation(s) in RCA: 258] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2000] [Accepted: 03/13/2001] [Indexed: 12/24/2022] Open
Abstract
Upregulated epidermal growth factor (EGF) receptor (EGFR) expression and EGFR-induced signaling have been correlated with progression to invasion and metastasis in a wide variety of carcinomas, but the mechanism behind this is not well understood. We show here that, in various human carcinoma cells that overexpress EGFR, EGF treatment induced rapid tyrosine dephosphorylation of focal adhesion kinase (FAK) associated with downregulation of its kinase activity. The downregulation of FAK activity was both required and sufficient for EGF-induced refractile morphological changes, detachment of cells from the extracellular matrix, and increased tumor cell motility, invasion, and metastasis. Tumor cells with downregulated FAK activity became less adherent to the extracellular matrix. However, once cells started reattaching, FAK activity was restored by activated integrin signaling. Moreover, this process of readhesion and spreading could not be abrogated by further EGF stimulation. Interruption of transforming growth factor alpha-EGFR autocrine regulation with an EGFR tyrosine kinase inhibitor led to a substantial increase in FAK tyrosine phosphorylation and inhibition of tumor cell invasion in vitro. Consistent with this, FAK tyrosine phosphorylation was reduced in cells from tumors growing in transplanted, athymic, nude mice, which have an intact autocrine regulation of the EGFR. We suggest that the dynamic regulation of FAK activity, initiated by EGF-induced downregulation of FAK leading to cell detachment and increased motility and invasion, followed by integrin-dependent reactivation during readhesion, plays a role in EGF-associated tumor invasion and metastasis.
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Affiliation(s)
- Z Lu
- Molecular and Cell Biology Laboratory, Salk Institute for Biological Studies, La Jolla, California 92037, USA
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119
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Sindić A, Aleksandrova A, Fields AP, Volinia S, Banfić H. Presence and activation of nuclear phosphoinositide 3-kinase C2beta during compensatory liver growth. J Biol Chem 2001; 276:17754-61. [PMID: 11278304 DOI: 10.1074/jbc.m006533200] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Highly purified liver nuclei incorporated radiolabeled phosphate into phosphatidylinositol 4-phosphate (PtdIns(4)P), PtdIns(4,5)P(2), and PtdIns(3,4,5)P(3). When nuclei were depleted of their membrane, no radiolabeling of PtdIns(3,4,5)P(3) could be detected showing that within the intranuclear region there are no class I phosphoinositide 3-kinases (PI3K)s. In membrane-depleted nuclei harvested 20 h after partial hepatectomy, the incorporation of radiolabel into PtdIns(3)P was observed together with an increase in immunoprecipitable PI3K-C2beta activity, which is sensitive to wortmannin (10 nm) and shows strong preference for PtdIns over PtdIns(4)P as a substrate. On Western blots PI3K-C2beta revealed a single immunoreactive band of 180 kDa, whereas 20 h after partial hepatectomy gel shift of 18 kDa was noticed, suggesting that observed activation of enzyme is achieved by proteolysis. When intact membrane-depleted nuclei were subjected to short term (20 min) exposure to micro-calpain, similar gel shift together with an increase in PI3K-C2beta activity was observed, when compared with the nuclei harvested 20 h after partial hepatectomy. Moreover, the above-mentioned gel shift and increase in PI3K-C2beta activity could be prevented by the calpain inhibitor calpeptin. The data presented in this report show that, in the membrane-depleted nuclei during the compensatory liver growth, there is an increase in PtdIns(3)P formation as a result of PI3K-C2beta activation, which may be a calpain-mediated event.
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Affiliation(s)
- A Sindić
- Department of Physiology and Croatian Institute for Brain Research, School of Medicine, University of Zagreb, Salata 3, Zagreb 10,000, Croatia
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120
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Hintermann E, Bilban M, Sharabi A, Quaranta V. Inhibitory role of alpha 6 beta 4-associated erbB-2 and phosphoinositide 3-kinase in keratinocyte haptotactic migration dependent on alpha 3 beta 1 integrin. J Cell Biol 2001; 153:465-78. [PMID: 11331299 PMCID: PMC2190561 DOI: 10.1083/jcb.153.3.465] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2000] [Accepted: 03/19/2001] [Indexed: 01/13/2023] Open
Abstract
Keratinocytes and other epithelial cells express two receptors for the basement membrane (BM) extracellular matrix component laminin-5 (Ln-5), integrins alpha 3 beta 1 and alpha 6 beta 4. While alpha 3 beta 1 mediates adhesion, spreading, and migration (Kreidberg, J.A. 2000. Curr. Opin. Cell Biol. 12:548--553), alpha 6 beta 4 is involved in BM anchorage via hemidesmosomes (Borradori, L., and A. Sonnenberg. 1999. J. Invest. Dermatol. 112:411--418). We investigated a possible regulatory interplay between alpha 3 beta 1 and alpha 6 beta 4 in cell motility using HaCaT keratinocytes as a model. We found that alpha 6 beta 4 antibodies inhibit alpha 3 beta 1-mediated migration on Ln-5, but only when migration is haptotactic (i.e., spontaneous or stimulated by alpha 3 beta 1 activation), and not when chemotactic (i.e., triggered by epidermal growth factor receptor). Inhibition of migration by alpha 6 beta 4 depends upon phosphoinositide 3-kinase (PI3-K) since it is abolished by PI3-K blockers and by dominant-negative PI3-K, and constitutively active PI3-K prevents haptotaxis. In HaCaT cells incubated with anti-alpha 6 beta 4 antibodies, activation of PI3-K is mediated by alpha 6 beta 4-associated erbB-2, as indicated by erbB-2 autophosphorylation and erbB-2/p85 PI3-K coprecipitation. Furthermore, dominant-negative erbB-2 abolishes inhibition of haptotaxis by anti-alpha 6 beta 4 antibodies. These results support a model whereby (a) haptotactic cell migration on Ln-5 is regulated by concerted action of alpha 3beta 1 and alpha 6 beta 4 integrins, (b) alpha 6 beta 4-associated erbB-2 and PI3-K negatively affect haptotaxis, and (c) chemotaxis on Ln-5 is not affected by alpha 6 beta 4 antibodies and may require PI3-K activity. This model could be of general relevance to motility of epithelial cells in contact with BM.
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Affiliation(s)
- Edith Hintermann
- Department of Cell Biology, The Scripps Research Institute, La Jolla, California 92037
| | - Martin Bilban
- Department of Cell Biology, The Scripps Research Institute, La Jolla, California 92037
| | - Andrew Sharabi
- Department of Cell Biology, The Scripps Research Institute, La Jolla, California 92037
| | - Vito Quaranta
- Department of Cell Biology, The Scripps Research Institute, La Jolla, California 92037
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121
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Gaidarov I, Smith ME, Domin J, Keen JH. The class II phosphoinositide 3-kinase C2alpha is activated by clathrin and regulates clathrin-mediated membrane trafficking. Mol Cell 2001; 7:443-9. [PMID: 11239472 DOI: 10.1016/s1097-2765(01)00191-5] [Citation(s) in RCA: 200] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Phosphoinositides play key regulatory roles in vesicular transport pathways in eukaryotic cells. Clathrin-mediated membrane trafficking has been shown to require phosphoinositides, but little is known about the enzyme(s) responsible for their formation. Here we report that clathrin functions as an adaptor for the class II PI 3-kinase C2alpha (PI3K-C2alpha), binding to its N-terminal region and stimulating its catalytic activity, especially toward phosphorylated inositide substrates. Further, we show that endogenous PI3K-C2alpha is localized in coated pits and that exogenous expression affects clathrin-mediated endocytosis and sorting in the trans-Golgi network. These findings provide a mechanistic basis for localized inositide generation at sites of clathrin-coated bud formation, which, with recruitment of inositide binding proteins and subsequent synaptojanin-mediated phosphoinositide hydrolysis, may regulate coated vesicle formation and uncoating.
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Affiliation(s)
- I Gaidarov
- Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA 19107, USA
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122
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Carballada R, Yasuo H, Lemaire P. Phosphatidylinositol-3 kinase acts in parallel to the ERK MAP kinase in the FGF pathway during Xenopus mesoderm induction. Development 2001; 128:35-44. [PMID: 11092809 DOI: 10.1242/dev.128.1.35] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Phosphoinositide 3-kinases (PI3Ks) are lipid kinases that can phosphorylate phosphaditylinositides leading to the cell type-specific regulation of intracellular protein kinases. PI3Ks are involved in a wide variety of cellular events including mitogenic signalling, regulation of growth and survival, vesicular trafficking, and control of the cytoskeleton. Some of these enzymes also act downstream of receptor tyrosine kinases or G-protein-coupled receptors. Using two strategies to inhibit PI3K signalling in embryos, we have analysed the role of PI3Ks during early Xenopus development. We find that a class 1A PI3K catalytic activity is required for the definition of trunk mesoderm during the blastula stages, but is less important for endoderm and prechordal plate mesoderm induction or for organiser formation. It is required in the FGF signalling pathway downstream of Ras and in parallel to the extracellular signal-regulated kinase (ERK) MAP kinases. In addition, our results show that ERKs and PI3Ks can synergise to convert ectoderm into mesoderm. These data provide the first evidence that class 1 PI3Ks are required for a specific set of patterning events in vertebrate embryos. Furthermore, they bring new insight into the FGF signalling cascade in Xenopus.
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Affiliation(s)
- R Carballada
- Laboratoire de Génétique et Physiologie du Développement, Institut de Biologie du Développement de Marseille, CNRS-INSERM-Université de la Méditerrannée-AP de Marseille, Campus de Luminy Case 907, F-13288 Marseille Cedex 9, France
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123
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Fry MJ. Phosphoinositide 3-kinase signalling in breast cancer: how big a role might it play? Breast Cancer Res 2001; 3:304-12. [PMID: 11597319 PMCID: PMC138693 DOI: 10.1186/bcr312] [Citation(s) in RCA: 116] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2001] [Revised: 05/22/2001] [Accepted: 06/04/2001] [Indexed: 11/10/2022] Open
Abstract
Phosphoinositide 3-kinase (PI3K) was first identified as a lipid kinase activity associated with the products of viral oncogenes and with activated protein-tyrosine kinases. Since those early studies, the PI3K superfamily has grown to embrace at least 12 structurally and functionally related enzymes present in the human genome, some of which have protein kinase activity but not lipid kinase activity. Evidence is emerging that PI3K superfamily members, and components of PI3K signalling, play a role in the development of many human cancers. In this review, the PI3K family of enzymes and their signalling is reviewed, with particular reference to possible involvement in breast cancer.
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Affiliation(s)
- M J Fry
- School of Animal and Microbial Sciences, University of Reading, Reading, UK.
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124
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Stein RC, Waterfield MD. PI3-kinase inhibition: a target for drug development? MOLECULAR MEDICINE TODAY 2000; 6:347-57. [PMID: 10954868 DOI: 10.1016/s1357-4310(00)01770-6] [Citation(s) in RCA: 163] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The phosphoinositide 3-kinases (PI3-kinases) are a ubiquitously expressed enzyme family that, through the generation of phospholipid second messengers, play a key role in the regulation of many cellular processes. These include motility, proliferation and survival, and carbohydrate metabolism. Members of the PI3-kinase family and related kinases, their mechanism of activation and the cellular events that they influence are described in this review. As knowledge of their involvement in disease processes increases, the PI3-kinases appear to be an increasingly attractive target for drug development, particularly in the fields of cancer and other proliferative diseases, and in the treatment of inflammatory and immunological conditions. Evidence of the functional specialization of PI3-kinase isoforms suggests that selective inhibition with acceptable toxicity might be possible.
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Affiliation(s)
- R C Stein
- The Ludwig Institute for Cancer Research and Department of Oncology, Royal Free and University College London Medical School, 91 Riding House Street, London, UK W1W 7BS.
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