1
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El Motiam A, de la Cruz-Herrera CF, Vidal S, Seoane R, Baz-Martínez M, Bouzaher YH, Lecona E, Esteban M, Rodríguez MS, Vidal A, Collado M, Rivas C. SUMOylation modulates the stability and function of PI3K-p110β. Cell Mol Life Sci 2021; 78:4053-4065. [PMID: 33834259 PMCID: PMC11073289 DOI: 10.1007/s00018-021-03826-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2020] [Revised: 02/14/2021] [Accepted: 03/27/2021] [Indexed: 12/19/2022]
Abstract
Class I PI3K are heterodimers composed of a p85 regulatory subunit and a p110 catalytic subunit involved in multiple cellular functions. Recently, the catalytic subunit p110β has emerged as a class I PI3K isoform playing a major role in tumorigenesis. Understanding its regulation is crucial for the control of the PI3K pathway in p110β-driven cancers. Here we sought to evaluate the putative regulation of p110β by SUMO. Our data show that p110β can be modified by SUMO1 and SUMO2 in vitro, in transfected cells and under completely endogenous conditions, supporting the physiological relevance of p110β SUMOylation. We identify lysine residue 952, located at the activation loop of p110β, as essential for SUMOylation. SUMOylation of p110β stabilizes the protein increasing its activation of AKT which promotes cell growth and oncogenic transformation. Finally, we show that the regulatory subunit p85β counteracts the conjugation of SUMO to p110β. In summary, our data reveal that SUMO is a novel p110β interacting partner with a positive effect on the activation of the PI3K pathway.
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Affiliation(s)
- Ahmed El Motiam
- Centro de Investigación en Medicina Molecular (CIMUS), CIMUS, P2L7, Universidade de Santiago de Compostela and Instituto de Investigaciones Sanitarias (IDIS), Avda Barcelona, 15706, Santiago de Compostela, Spain
| | | | - Santiago Vidal
- Centro de Investigación en Medicina Molecular (CIMUS), CIMUS, P2L7, Universidade de Santiago de Compostela and Instituto de Investigaciones Sanitarias (IDIS), Avda Barcelona, 15706, Santiago de Compostela, Spain
| | - Rocío Seoane
- Centro de Investigación en Medicina Molecular (CIMUS), CIMUS, P2L7, Universidade de Santiago de Compostela and Instituto de Investigaciones Sanitarias (IDIS), Avda Barcelona, 15706, Santiago de Compostela, Spain
| | - Maite Baz-Martínez
- Centro de Investigación en Medicina Molecular (CIMUS), CIMUS, P2L7, Universidade de Santiago de Compostela and Instituto de Investigaciones Sanitarias (IDIS), Avda Barcelona, 15706, Santiago de Compostela, Spain
| | - Yanis H Bouzaher
- Centro de Investigación en Medicina Molecular (CIMUS), CIMUS, P2L7, Universidade de Santiago de Compostela and Instituto de Investigaciones Sanitarias (IDIS), Avda Barcelona, 15706, Santiago de Compostela, Spain
| | - Emilio Lecona
- Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Universidad Autónoma de Madrid, Cantoblanco, 28049, Madrid, Spain
| | - Mariano Esteban
- Departamento de Biología Molecular y Celular, Centro Nacional de Biotecnología (CNB), CSIC, Darwin 3, 28049, Madrid, Spain
| | - Manuel S Rodríguez
- Laboratoire de Chimie de Coordination LCC-UPR 8241-CNRS, Toulouse, France
- IPBS-University of Toulouse III-Paul Sabatier, Toulouse, France
| | - Anxo Vidal
- Centro de Investigación en Medicina Molecular (CIMUS), CIMUS, P2L7, Universidade de Santiago de Compostela and Instituto de Investigaciones Sanitarias (IDIS), Avda Barcelona, 15706, Santiago de Compostela, Spain
| | - Manuel Collado
- Instituto de Investigación Sanitaria de Santiago de Compostela (IDIS), Complexo Hospitalario Universitario de Santiago de Compostela (CHUS), SERGAS, 15706, Santiago de Compostela, Spain
| | - Carmen Rivas
- Centro de Investigación en Medicina Molecular (CIMUS), CIMUS, P2L7, Universidade de Santiago de Compostela and Instituto de Investigaciones Sanitarias (IDIS), Avda Barcelona, 15706, Santiago de Compostela, Spain.
- Departamento de Biología Molecular y Celular, Centro Nacional de Biotecnología (CNB), CSIC, Darwin 3, 28049, Madrid, Spain.
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2
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Salloum G, Jakubik CT, Erami Z, Heitz SD, Bresnick AR, Backer JM. PI3Kβ is selectively required for growth factor-stimulated macropinocytosis. J Cell Sci 2019; 132:jcs.231639. [PMID: 31409694 DOI: 10.1242/jcs.231639] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Accepted: 07/16/2019] [Indexed: 12/16/2022] Open
Abstract
Macropinocytosis is an actin-dependent but clathrin-independent endocytic process by which cells nonselectively take up large aliquots of extracellular material. Macropinocytosis is used for immune surveillance by dendritic cells, as a route of infection by viruses and protozoa, and as a nutrient uptake pathway in tumor cells. In this study, we explore the role of class I phosphoinositide 3-kinases (PI3Ks) during ligand-stimulated macropinocytosis. We find that macropinocytosis in response to receptor tyrosine kinase activation is strikingly dependent on a single class I PI3K isoform, namely PI3Kβ (containing the p110β catalytic subunit encoded by PIK3CB). Loss of PI3Kβ expression or activity blocks macropinocytosis at early steps, before the formation of circular dorsal ruffles, but also plays a role in later steps, downstream from Rac1 activation. PI3Kβ is also required for the elevated levels of constitutive macropinocytosis found in tumor cells that are defective for the PTEN tumor suppressor. Our data shed new light on PI3K signaling during macropinocytosis, and suggest new therapeutic uses for pharmacological inhibitors of PI3Kβ.
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Affiliation(s)
- Gilbert Salloum
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Charles T Jakubik
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Zahra Erami
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Samantha D Heitz
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Anne R Bresnick
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Jonathan M Backer
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY 10461, USA .,Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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3
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Bresnick AR, Backer JM. PI3Kβ-A Versatile Transducer for GPCR, RTK, and Small GTPase Signaling. Endocrinology 2019; 160:536-555. [PMID: 30601996 PMCID: PMC6375709 DOI: 10.1210/en.2018-00843] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/25/2018] [Accepted: 12/20/2018] [Indexed: 12/17/2022]
Abstract
The phosphoinositide 3-kinase (PI3K) family includes eight distinct catalytic subunits and seven regulatory subunits. Only two PI3Ks are directly regulated downstream from G protein-coupled receptors (GPCRs): the class I enzymes PI3Kβ and PI3Kγ. Both enzymes produce phosphatidylinositol 3,4,5-trisposphate in vivo and are regulated by both heterotrimeric G proteins and small GTPases from the Ras or Rho families. However, PI3Kβ is also regulated by direct interactions with receptor tyrosine kinases (RTKs) and their tyrosine phosphorylated substrates, and similar to the class II and III PI3Ks, it binds activated Rab5. The unusually complex regulation of PI3Kβ by small and trimeric G proteins and RTKs leads to a rich landscape of signaling responses at the cellular and organismic levels. This review focuses first on the regulation of PI3Kβ activity in vitro and in cells, and then summarizes the biology of PI3Kβ signaling in distinct tissues and in human disease.
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Affiliation(s)
- Anne R Bresnick
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York
| | - Jonathan M Backer
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York
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4
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Nobs SP, Schneider C, Heer AK, Huotari J, Helenius A, Kopf M. PI3Kγ Is Critical for Dendritic Cell-Mediated CD8+ T Cell Priming and Viral Clearance during Influenza Virus Infection. PLoS Pathog 2016; 12:e1005508. [PMID: 27030971 PMCID: PMC4816423 DOI: 10.1371/journal.ppat.1005508] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Accepted: 02/25/2016] [Indexed: 12/20/2022] Open
Abstract
Phosphoinositide-3-kinases have been shown to be involved in influenza virus pathogenesis. They are targeted directly by virus proteins and are essential for efficient viral replication in infected lung epithelial cells. However, to date the role of PI3K signaling in influenza infection in vivo has not been thoroughly addressed. Here we show that one of the PI3K subunits, p110γ, is in fact critically required for mediating the host’s antiviral response. PI3Kγ deficient animals exhibit a delayed viral clearance and increased morbidity during respiratory infection with influenza virus. We demonstrate that p110γ is required for the generation and maintenance of potent antiviral CD8+ T cell responses through the developmental regulation of pulmonary cross-presenting CD103+ dendritic cells under homeostatic and inflammatory conditions. The defect in lung dendritic cells leads to deficient CD8+ T cell priming, which is associated with higher viral titers and more severe disease course during the infection. We thus identify PI3Kγ as a novel key host protective factor in influenza virus infection and shed light on an unappreciated layer of complexity concerning the role of PI3K signaling in this context. Acute respiratory viral infections like influenza virus can cause life-threatening disease in infected individuals. Phosphoinositide-3-kinases have been suggested to be important factors used by the virus to infect and replicate in host cells, and thereby cause viral pneumonia. However, to date the role of these signaling molecules has not been thoroughly addressed in the context of an infection in whole animals, rather than just cell culture systems. Here we show that one of the PI3K subunits, PI3Kγ, is in fact critically required for the clearance of the infection. This is because PI3Kγ regulates the immune response against the virus through the generation and maintenance of antiviral CD8+ T cell responses. We show that in the absence of PI3Kγ a specialized dendritic cell subset in the lung is deficient and this leads to a strongly impaired immune response against influenza virus. We thus identify PI3Kγ as a novel host molecule that is important for the immune defense against influenza virus infection
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Affiliation(s)
- Samuel Philip Nobs
- Molecular Biomedicine, Institute of Molecular Health Sciences, Department of Biology, ETH Zurich, Zurich, Switzerland
| | - Christoph Schneider
- Molecular Biomedicine, Institute of Molecular Health Sciences, Department of Biology, ETH Zurich, Zurich, Switzerland
| | - Alex Kaspar Heer
- Molecular Biomedicine, Institute of Molecular Health Sciences, Department of Biology, ETH Zurich, Zurich, Switzerland
| | - Jatta Huotari
- Institute of Biochemistry, ETH Zürich, Zurich, Switzerland
| | - Ari Helenius
- Institute of Biochemistry, ETH Zürich, Zurich, Switzerland
| | - Manfred Kopf
- Molecular Biomedicine, Institute of Molecular Health Sciences, Department of Biology, ETH Zurich, Zurich, Switzerland
- * E-mail:
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5
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Abstract
Phosphoinositide 3-kinases (PI3Ks) are central regulators of cellular responses to extracellular stimuli, and are involved in growth, proliferation, migration, and metabolism. The Class I PI3Ks are activated by Receptor Tyrosine Kinases (RTKs) or G Protein-Coupled Receptors (GPCRs), and their signaling is commonly deregulated in disease conditions. Among the class I PI3Ks, the p110β isoform is unique in being activated by both RTKs and GPCRs, and its ability to bind Rho-GTPases and Rab5. Recent studies have characterized these p110β interacting partners, defining the binding mechanisms and regulation, and thus provide insight into the function of this kinase in physiology and disease. This review summarizes the developments in p110β research, focusing on the interacting partners and their role in p110β-mediated signaling.
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Affiliation(s)
- Hashem A Dbouk
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390
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6
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Tzenaki N, Papakonstanti EA. p110δ PI3 kinase pathway: emerging roles in cancer. Front Oncol 2013; 3:40. [PMID: 23459844 PMCID: PMC3585436 DOI: 10.3389/fonc.2013.00040] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2012] [Accepted: 02/12/2013] [Indexed: 12/11/2022] Open
Abstract
Class IA PI3Ks consists of three isoforms of the p110 catalytic subunit designated p110α, p110β, and p110δ which are encoded by three separate genes. Gain-of-function mutations on PIK3CA gene encoding for p110α isoform have been detected in a wide variety of human cancers whereas no somatic mutations of genes encoding for p110β or p110δ have been reported. Unlike p110α and p110β which are ubiquitously expressed, p110δ is highly enriched in leukocytes and thus the p110δ PI3K pathway has attracted more attention for its involvement in immune disorders. However, findings have been accumulated showing that the p110δ PI3K plays a seminal role in the development and progression of some hematologic malignancies. A wealth of knowledge has come from studies showing the central role of p110δ PI3K in B-cell functions and B-cell malignancies. Further data have documented that wild-type p110δ becomes oncogenic when overexpressed in cell culture models and that p110δ is the predominant isoform expressed in some human solid tumor cells playing a prominent role in these cells. Genetic inactivation of p110δ in mice models and highly-selective inhibitors of p110δ have demonstrated an important role of this isoform in differentiation, growth, survival, motility, and morphology with the inositol phosphatase PTEN to play a critical role in p110δ signaling. In this review, we summarize our understanding of the p110δ PI3K signaling pathway in hematopoietic cells and malignancies, we highlight the evidence showing the oncogenic potential of p110δ in cells of non-hematopoietic origin and we discuss perspectives for potential novel roles of p110δ PI3K in cancer.
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Affiliation(s)
- Niki Tzenaki
- Department of Biochemistry, School of Medicine, University of Crete Heraklion, Greece
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7
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Ali AY, Farrand L, Kim JY, Byun S, Suh JY, Lee HJ, Tsang BK. Molecular determinants of ovarian cancer chemoresistance: new insights into an old conundrum. Ann N Y Acad Sci 2013; 1271:58-67. [PMID: 23050965 PMCID: PMC3499654 DOI: 10.1111/j.1749-6632.2012.06734.x] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Ovarian cancer is the most lethal gynecological malignancy. Cisplatin and its derivatives are first-line chemotherapeutics, and their resistance is a major hurdle in successful ovarian cancer treatment. Understanding the molecular dysregulation underlying chemoresistance is important for enhancing therapeutic outcome. Here, we review two established pathways in cancer chemoresistance. p53 is a major tumor suppressor regulating proliferation and apoptosis, and its mutation is a frequent event in human malignancies. The PI3K/Akt axis is a key oncogenic pathway regulating survival and tumorigenesis by controlling several tumor suppressors, including p53. The interplay between these pathways is well established, although the oncogenic phosphatase PPM1D adds a new layer to this intricate relationship and provides new insights into the processes determining cell fate. Inhibition of the PI3K/Akt pathway by functional food compounds as an adjunct to chemotherapeutics may tip the balance in favor of apoptosis rather than survival, enhancing therapeutic efficacy, and reducing side effects.
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Affiliation(s)
- Ahmed Y Ali
- Department of Cellular Medicine, University of Ottawa, Ottawa, Ontario, Canada
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8
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Redondo-Muñoz J, Rodríguez MJ, Silió V, Pérez-García V, Valpuesta JM, Carrera AC. Phosphoinositide 3-kinase beta controls replication factor C assembly and function. Nucleic Acids Res 2012; 41:855-68. [PMID: 23175608 PMCID: PMC3553946 DOI: 10.1093/nar/gks1095] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Genomic integrity is preserved by the action of protein complexes that control DNA homeostasis. These include the sliding clamps, trimeric protein rings that are arranged around DNA by clamp loaders. Replication factor C (RFC) is the clamp loader for proliferating cell nuclear antigen, which acts on DNA replication. Other processes that require mobile contact of proteins with DNA use alternative RFC complexes that exchange RFC1 for CTF18 or RAD17. Phosphoinositide 3-kinases (PI3K) are lipid kinases that generate 3-poly-phosphorylated-phosphoinositides at the plasma membrane following receptor stimulation. The two ubiquitous isoforms, PI3Kalpha and PI3Kbeta, have been extensively studied due to their involvement in cancer and nuclear PI3Kbeta has been found to regulate DNA replication and repair, processes controlled by molecular clamps. We studied here whether PI3Kbeta directly controls the process of molecular clamps loading. We show that PI3Kbeta associated with RFC1 and RFC1-like subunits. Only when in complex with PI3Kbeta, RFC1 bound to Ran GTPase and localized to the nucleus, suggesting that PI3Kbeta regulates RFC1 nuclear import. PI3Kbeta controlled not only RFC1- and RFC-RAD17 complexes, but also RFC-CTF18, in turn affecting CTF18-mediated chromatid cohesion. PI3Kbeta thus has a general function in genomic stability by controlling the localization and function of RFC complexes.
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Affiliation(s)
- Javier Redondo-Muñoz
- Department of Immunology and Oncology, Centro Nacional de Biotecnología (CNB-CSIC), Darwin 3, Campus de Cantoblanco, Madrid E-28049, Spain
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9
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Abstract
The PI3K pathway plays an important role in key cellular functions such as cell growth, proliferation and survival. Genetic and epigenetic alterations in different pathway components lead to aberrant pathway activation and have been observed in high frequencies in various tumor types. Consequently, significant effort has been made to develop antineoplastic agents targeting different nodes in this pathway. Additionally, PI3K pathway status may have predictive and prognostic implications, and may contribute to drug resistance in tumor cells. This article provides an overview of our current knowledge of the PI3K pathway with an emphasis on its application in cancer treatment.
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Affiliation(s)
- Navid Sadeghi
- Division of Hematology & Oncology, Harold C Simmons Cancer Center, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - David E Gerber
- Division of Hematology & Oncology, Harold C Simmons Cancer Center, University of Texas Southwestern Medical Center, Dallas, TX, USA
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10
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Nuclear but not cytosolic phosphoinositide 3-kinase beta has an essential function in cell survival. Mol Cell Biol 2011; 31:2122-33. [PMID: 21383062 DOI: 10.1128/mcb.01313-10] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Class I(A) phosphoinositide 3-kinases (PI3Ks) are heterodimeric enzymes composed of a p85 regulatory and a p110 catalytic subunit that induce the formation of 3-polyphosphoinositides, which mediate cell survival, division, and migration. There are two ubiquitous PI3K isoforms p110α and p110β that have nonredundant functions in embryonic development and cell division. However, whereas p110α concentrates in the cytoplasm, p110β localizes to the nucleus and modulates nuclear processes such as DNA replication and repair. At present, the structural features that determine p110β nuclear localization remain unknown. We describe here that association with the p85β regulatory subunit controls p110β nuclear localization. We identified a nuclear localization signal (NLS) in p110β C2 domain that mediates its nuclear entry, as well as a nuclear export sequence (NES) in p85β. Deletion of p110β induced apoptosis, and complementation with the cytoplasmic C2-NLS p110β mutant was unable to restore cell survival. These studies show that p110β NLS and p85β NES regulate p85β/p110β nuclear localization, supporting the idea that nuclear, but not cytoplasmic, p110β controls cell survival.
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11
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Backer JM. The regulation of class IA PI 3-kinases by inter-subunit interactions. Curr Top Microbiol Immunol 2011; 346:87-114. [PMID: 20544340 DOI: 10.1007/82_2010_52] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Phosphoinositide 3-kinases (PI 3-kinases) are activated by growth factor and hormone receptors, and regulate cell growth, survival, motility, and responses to changes in nutritional conditions (Engelman et al. 2006). PI 3-kinases have been classified according to their subunit composition and their substrate specificity for phosphoinositides (Vanhaesebroeck et al. 2001). The class IA PI 3-kinase is a heterodimer consisting of one regulatory subunit (p85α, p85β, p55α, p50α, or p55γ) and one 110-kDa catalytic subunit (p110α, β or δ). The Class IB PI 3-kinase is also a dimer, composed of one regulatory subunit (p101 or p87) and one catalytic subunit (p110γ) (Wymann et al. 2003). Class I enzymes will utilize PI, PI[4]P, or PI[4,5]P2 as substrates in vitro, but are thought to primarily produce PI[3,4,5]P3 in cells.The crystal structure of the Class IB PI 3-kinase catalytic subunit p110γ was solved in 1999 (Walker et al. 1999), and crystal or NMR structures of the Class IA p110α catalytic subunit and all of the individual domains of the Class IA p85α regulatory subunit have been solved (Booker et al. 1992; Günther et al. 1996; Hoedemaeker et al. 1999; Huang et al. 2007; Koyama et al. 1993; Miled et al. 2007; Musacchio et al. 1996; Nolte et al. 1996; Siegal et al. 1998). However, a structure of an intact PI 3-kinase enzyme has remained elusive. In spite of this, studies over the past 10 years have lead to important insights into how the enzyme is regulated under physiological conditions. This chapter will specifically discuss the regulation of Class IA PI 3-kinase enzymatic activity, focusing on regulatory interactions between the p85 and p110 subunits and the modulation of these interactions by physiological activators and oncogenic mutations. The complex web of signaling downstream from Class IA PI 3-kinases will be discussed in other chapters in this volume.
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Affiliation(s)
- Jonathan M Backer
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY, 10461, USA.
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12
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Zhao L, Vogt PK. Hot-spot mutations in p110alpha of phosphatidylinositol 3-kinase (pI3K): differential interactions with the regulatory subunit p85 and with RAS. Cell Cycle 2010; 9:596-600. [PMID: 20009532 DOI: 10.4161/cc.9.3.10599] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The phosphatidylinositol 3-kinase (pI3K) signaling pathway is frequently upregulated in cancer. PIK3CA, the gene coding for the catalytic subunit p110alpha of PI3K, is mutated in about 12% of all human cancers. Most of these mutants are single amino acid substitutions that map to three positions (hot spots) in the helical or kinase domains of the enzyme. The mutant proteins show gain of enzymatic function, constitutively activate AKT signaling and induce oncogenic transformation in vitro and in animal model systems. We have shown previously that hot-spot mutations in the helical domain and kinase domain of the avian p110alpha have different requirements for interaction with the regulatory subunit p85 and with RAS-GTP. Here, we have carried out a genetic and biochemical analysis of these "hot-spot" mutations in human p110alpha. The present studies add support to the proposal that helical and kinase domain mutations in p110alpha trigger a gain of function by different molecular mechanisms. The gain of function induced by helical domain mutations requires interaction with RAS-Gtp. In contrast, the kinase domain mutation is active in the absence of RAS-Gtp binding, but depends on the interaction with p85.
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Affiliation(s)
- Li Zhao
- Department of Molecular and Experimental Medicine, The Scripps Research Institute; La Jolla, CA. USA.
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13
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Abstract
The phosphoinositide (PI) cycle, discovered over 50 years ago by Mabel and Lowell Hokin, describes a series of biochemical reactions that occur on the inner leaflet of the plasma membrane of cells in response to receptor activation by extracellular stimuli. Studies from our laboratory have shown that the retina and rod outer segments (ROSs) have active PI metabolism. Biochemical studies revealed that the ROSs contain the enzymes necessary for phosphorylation of phosphoinositides. We showed that light stimulates various components of the PI cycle in the vertebrate ROS, including diacylglycerol kinase, PI synthetase, phosphatidylinositol phosphate kinase, phospholipase C, and phosphoinositide 3-kinase (PI3K). This article describes recent studies on the PI3K-generated PI lipid second messengers in the control and regulation of PI-binding proteins in the vertebrate retina.
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Affiliation(s)
- Raju V S Rajala
- Departments of Ophthalmology and Cell Biology, and Dean A. McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA. r
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14
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Jaiswal BS, Janakiraman V, Kljavin NM, Chaudhuri S, Stern HM, Wang W, Kan Z, Dbouk HA, Peters BA, Waring P, Vega TD, Kenski DM, Bowman K, Lorenzo M, Li H, Wu J, Modrusan Z, Stinson J, Eby M, Yue P, Kaminker J, de Sauvage FJ, Backer JM, Seshagiri S. Somatic mutations in p85alpha promote tumorigenesis through class IA PI3K activation. Cancer Cell 2009; 16:463-74. [PMID: 19962665 PMCID: PMC2804903 DOI: 10.1016/j.ccr.2009.10.016] [Citation(s) in RCA: 245] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/28/2009] [Revised: 08/18/2009] [Accepted: 10/19/2009] [Indexed: 12/19/2022]
Abstract
Members of the mammalian phosphoinositide-3-OH kinase (PI3K) family of proteins are critical regulators of various cellular process including cell survival, growth, proliferation, and motility. Oncogenic activating mutations in the p110alpha catalytic subunit of the heterodimeric p110/p85 PI3K enzyme are frequent in human cancers. Here we show the presence of frequent mutations in p85alpha in colon cancer, a majority of which occurs in the inter-Src homology-2 (iSH2) domain. These mutations uncouple and retain p85alpha's p110-stabilizing activity, while abrogating its p110-inhibitory activity. The p85alpha mutants promote cell survival, AKT activation, anchorage-independent cell growth, and oncogenesis in a p110-dependent manner.
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Affiliation(s)
- Bijay S. Jaiswal
- Department of Molecular Biology, Genentech Inc., 1 DNA WAY, South San Francisco, CA 94080
| | | | - Noelyn M. Kljavin
- Department of Molecular Biology, Genentech Inc., 1 DNA WAY, South San Francisco, CA 94080
| | - Subhra Chaudhuri
- Department of Molecular Biology, Genentech Inc., 1 DNA WAY, South San Francisco, CA 94080
| | - Howard M. Stern
- Department of Pathology, Genentech Inc., 1 DNA WAY, South San Francisco, CA 94080
| | - Weiru Wang
- Department of Protein Engineering, Genentech Inc., 1 DNA WAY, South San Francisco, CA 94080
| | - Zhengyan Kan
- Department of Molecular Biology, Genentech Inc., 1 DNA WAY, South San Francisco, CA 94080
| | - Hashem A. Dbouk
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Brock A. Peters
- Department of Molecular Biology, Genentech Inc., 1 DNA WAY, South San Francisco, CA 94080
| | - Paul Waring
- Department of Pathology, Genentech Inc., 1 DNA WAY, South San Francisco, CA 94080
| | - Trisha Dela Vega
- Department of Protein Engineering, Genentech Inc., 1 DNA WAY, South San Francisco, CA 94080
| | - Denise M. Kenski
- Department of Molecular Biology, Genentech Inc., 1 DNA WAY, South San Francisco, CA 94080
| | - Krista Bowman
- Department of Protein Engineering, Genentech Inc., 1 DNA WAY, South San Francisco, CA 94080
| | - Maria Lorenzo
- Department of Protein Chemistry, Genentech Inc., 1 DNA WAY, South San Francisco, CA 94080
| | - Hong Li
- Department of Protein Chemistry, Genentech Inc., 1 DNA WAY, South San Francisco, CA 94080
| | - Jiansheng Wu
- Department of Protein Chemistry, Genentech Inc., 1 DNA WAY, South San Francisco, CA 94080
| | - Zora Modrusan
- Department of Molecular Biology, Genentech Inc., 1 DNA WAY, South San Francisco, CA 94080
| | - Jeremy Stinson
- Department of Molecular Biology, Genentech Inc., 1 DNA WAY, South San Francisco, CA 94080
| | - Michael Eby
- Department of Translational Oncology, Genentech Inc., 1 DNA WAY, South San Francisco, CA 94080
| | - Peng Yue
- Department of Bioinformatics, Genentech Inc., 1 DNA WAY, South San Francisco, CA 94080
| | - Josh Kaminker
- Department of Bioinformatics, Genentech Inc., 1 DNA WAY, South San Francisco, CA 94080
| | - Frederic J. de Sauvage
- Department of Molecular Biology, Genentech Inc., 1 DNA WAY, South San Francisco, CA 94080
| | - Jonathan M. Backer
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Somasekar Seshagiri
- Department of Molecular Biology, Genentech Inc., 1 DNA WAY, South San Francisco, CA 94080
- Correspondence: ; phone: 650-225-1000; fax: 650-225-1762
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15
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Regulation of Class IA PI 3-kinases: C2 domain-iSH2 domain contacts inhibit p85/p110alpha and are disrupted in oncogenic p85 mutants. Proc Natl Acad Sci U S A 2009; 106:20258-63. [PMID: 19915146 DOI: 10.1073/pnas.0902369106] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
We previously proposed a model of Class IA PI3K regulation in which p85 inhibition of p110alpha requires (i) an inhibitory contact between the p85 nSH2 domain and the p110alpha helical domain, and (ii) a contact between the p85 nSH2 and iSH2 domains that orients the nSH2 so as to inhibit p110alpha. We proposed that oncogenic truncations of p85 fail to inhibit p110 due to a loss of the iSH2-nSH2 contact. However, we now find that within the context of a minimal regulatory fragment of p85 (the nSH2-iSH2 fragment, termed p85ni), the nSH2 domain rotates much more freely (tau(c) approximately 12.7 ns) than it could if it were interacting rigidly with the iSH2 domain. These data are not compatible with our previous model. We therefore tested an alternative model in which oncogenic p85 truncations destabilize an interface between the p110alpha C2 domain (residue N345) and the p85 iSH2 domain (residues D560 and N564). p85ni-D560K/N564K shows reduced inhibition of p110alpha, similar to the truncated p85ni-572(STOP). Conversely, wild-type p85ni poorly inhibits p110alphaN345K. Strikingly, the p110alphaN345K mutant is inhibited to the same extent by the wild-type or truncated p85ni, suggesting that mutation of p110alpha-N345 is not additive with the p85ni-572(STOP) mutation. Similarly, the D560K/N564K mutation is not additive with the p85ni-572(STOP) mutant for downstream signaling or cellular transformation. Thus, our data suggests that mutations at the C2-iSH2 domain contact and truncations of the iSH2 domain, which are found in human tumors, both act by disrupting the C2-iSH2 domain interface.
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Hill JW, Xu Y, Preitner F, Fukuda M, Cho YR, Luo J, Balthasar N, Coppari R, Cantley LC, Kahn BB, Zhao JJ, Elmquist JK. Phosphatidyl inositol 3-kinase signaling in hypothalamic proopiomelanocortin neurons contributes to the regulation of glucose homeostasis. Endocrinology 2009; 150:4874-82. [PMID: 19819947 PMCID: PMC2775989 DOI: 10.1210/en.2009-0454] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Recent studies demonstrated a role for hypothalamic insulin and leptin action in the regulation of glucose homeostasis. This regulation involves proopiomelanocortin (POMC) neurons because suppression of phosphatidyl inositol 3-kinase (PI3K) signaling in these neurons blunts the acute effects of insulin and leptin on POMC neuronal activity. In the current study, we investigated whether disruption of PI3K signaling in POMC neurons alters normal glucose homeostasis using mouse models designed to both increase and decrease PI3K-mediated signaling in these neurons. We found that deleting p85alpha alone induced resistance to diet-induced obesity. In contrast, deletion of the p110alpha catalytic subunit of PI3K led to increased weight gain and adipose tissue along with reduced energy expenditure. Independent of these effects, increased PI3K activity in POMC neurons improved insulin sensitivity, whereas decreased PI3K signaling resulted in impaired glucose regulation. These studies show that activity of the PI3K pathway in POMC neurons is involved in not only normal energy regulation but also glucose homeostasis.
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Affiliation(s)
- Jennifer W Hill
- Division of Hypothalamic Research, Department of Internal Medicine, The University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas 75390-9077, USA
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17
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Fluck MM, Schaffhausen BS. Lessons in signaling and tumorigenesis from polyomavirus middle T antigen. Microbiol Mol Biol Rev 2009; 73:542-63, Table of Contents. [PMID: 19721090 PMCID: PMC2738132 DOI: 10.1128/mmbr.00009-09] [Citation(s) in RCA: 121] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
The small DNA tumor viruses have provided a very long-lived source of insights into many aspects of the life cycle of eukaryotic cells. In recent years, the emphasis has been on cancer-related signaling. Here we review murine polyomavirus middle T antigen, its mechanisms, and its downstream pathways of transformation. We concentrate on the MMTV-PyMT transgenic mouse, one of the most studied models of breast cancer, which permits the examination of in situ tumor progression from hyperplasia to metastasis.
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Affiliation(s)
- Michele M Fluck
- Department of Microbiology and Molecular Genetics, Interdepartmental Program in Cell and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA.
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18
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Kok K, Nock GE, Verrall EAG, Mitchell MP, Hommes DW, Peppelenbosch MP, Vanhaesebroeck B. Regulation of p110delta PI 3-kinase gene expression. PLoS One 2009; 4:e5145. [PMID: 19357769 PMCID: PMC2663053 DOI: 10.1371/journal.pone.0005145] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2008] [Accepted: 02/19/2009] [Indexed: 01/20/2023] Open
Abstract
BACKGROUND Despite an intense interest in the biological functions of the phosphoinositide 3-kinase (PI3K) signalling enzymes, little is known about the regulation of PI3K gene expression. This also applies to the leukocyte-enriched p110delta catalytic subunit of PI3K, an enzyme that has attracted widespread interest because of its role in immunity and allergy. PRINCIPAL FINDINGS We show that p110delta expression is mainly regulated at the transcriptional level. In fibroblasts, lymphocytes and myeloid cells, p110delta gene transcription appears to be constitutive and not subject to acute stimulation. 5'RACE experiments revealed that p110delta mRNA transcripts contain distinct upstream untranslated exons (named exon -1, -2a, -2b, -2c and -2d), which are located up to 81 kb upstream of the translational start codon in exon 1. The levels of all the different p110delta transcripts are higher in leukocytes compared to non-leukocytes, with the p110delta transcript containing exon -2a most abundantly expressed. We have identified a highly conserved transcription factor (TF) binding cluster in the p110delta gene which has enhanced promoter activity in leukocytes compared to non-leukocytes. In human, this TF cluster is located immediately upstream of exon -2a whilst in mouse, it is located within exon -2a. CONCLUSION This study identifies a conserved PIK3CD promoter region that may account for the predominant leukocyte expression of p110delta.
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Affiliation(s)
- Klaartje Kok
- Centre for Cell Signalling, Institute of Cancer, Queen Mary University of London, Charterhouse Square, London, United Kingdom
- Department of Cell Biology, University Medical Centre Groningen, University of Groningen, Groningen, The Netherlands
| | - Gemma E. Nock
- Centre for Cell Signalling, Institute of Cancer, Queen Mary University of London, Charterhouse Square, London, United Kingdom
| | - Elizabeth A. G. Verrall
- Centre for Cell Signalling, Institute of Cancer, Queen Mary University of London, Charterhouse Square, London, United Kingdom
| | - Michael P. Mitchell
- Bioinformatics and Biostatistics, Cancer Research UK London Research Institute, London, United Kingdom
| | - Daan W. Hommes
- Department of Gastroenterology and Hepatology; Leiden University Medical Centre, Leiden, The Netherlands
| | - Maikel P. Peppelenbosch
- Department of Cell Biology, University Medical Centre Groningen, University of Groningen, Groningen, The Netherlands
| | - Bart Vanhaesebroeck
- Centre for Cell Signalling, Institute of Cancer, Queen Mary University of London, Charterhouse Square, London, United Kingdom
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Jaeger PA, Wyss-Coray T. All-you-can-eat: autophagy in neurodegeneration and neuroprotection. Mol Neurodegener 2009; 4:16. [PMID: 19348680 PMCID: PMC2679749 DOI: 10.1186/1750-1326-4-16] [Citation(s) in RCA: 132] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2008] [Accepted: 04/06/2009] [Indexed: 12/12/2022] Open
Abstract
Autophagy is the major pathway involved in the degradation of proteins and organelles, cellular remodeling, and survival during nutrient starvation. Autophagosomal dysfunction has been implicated in an increasing number of diseases from cancer to bacterial and viral infections and more recently in neurodegeneration. While a decrease in autophagic activity appears to interfere with protein degradation and possibly organelle turnover, increased autophagy has been shown to facilitate the clearance of aggregation-prone proteins and promote neuronal survival in a number of disease models. On the other hand, too much autophagic activity can be detrimental as well and lead to cell death, suggesting the regulation of autophagy has an important role in cell fate decisions. An increasing number of model systems are now available to study the role of autophagy in the central nervous system and how it might be exploited to treat disease. We will review here the current knowledge of autophagy in the central nervous system and provide an overview of the various models that have been used to study acute and chronic neurodegeneration.
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Affiliation(s)
- Philipp A Jaeger
- Geriatric Research Education and Clinical Center, VA Palo Alto Health Care System, 3801 Miranda Ave, Palo Alto, California, USA.
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20
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Schaffhausen BS, Roberts TM. Lessons from polyoma middle T antigen on signaling and transformation: A DNA tumor virus contribution to the war on cancer. Virology 2008; 384:304-16. [PMID: 19022468 DOI: 10.1016/j.virol.2008.09.042] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2008] [Accepted: 09/30/2008] [Indexed: 01/16/2023]
Abstract
Middle T antigen (MT) is the principal oncogene of murine polyomavirus. Its study has led to the discovery of the roles of tyrosine kinase and phosphoinositide 3-kinase (PI3K) signaling in mammalian growth control and transformation. MT is necessary for viral transformation in tissue culture cells and tumorigenesis in animals. When expressed alone as a transgene, MT causes tumors in a wide variety of tissues. It has no known catalytic activity, but rather acts by assembling cellular signal transduction molecules. Protein phosphatase 2A, protein tyrosine kinases of the src family, PI3K, phospholipase Cgamma1 as well as the Shc/Grb2 adaptors are all assembled on MT. Their activation sets off a series of signaling cascades. Analyses of virus mutants as well as transgenic animals have demonstrated that the effects of a given signal depend not only tissue type, but on the genetic background of the host animal. There remain many opportunities as we seek a full molecular understanding of MT and apply some of its lessons to human cancer.
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Affiliation(s)
- Brian S Schaffhausen
- Department of Biochemistry, Tufts University School of Medicine, Boston, MA 02111, USA
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21
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Scholl S, Bondeva T, Liu Y, Clement JH, Höffken K, Wetzker R. Additive effects of PI3-kinase and MAPK activities on NB4 cell granulocyte differentiation: potential role of phosphatidylinositol 3-kinase gamma. J Cancer Res Clin Oncol 2008; 134:861-72. [PMID: 18288489 DOI: 10.1007/s00432-008-0356-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2007] [Accepted: 12/28/2007] [Indexed: 11/25/2022]
Abstract
PURPOSE In acute promyelocytic leukemia (APL) the chromosome translocation t(15;17) resulting in the PML-RAR alpha fusion protein is responsible for a blockage of myeloid differentiation. In this study we investigated the expression of different Phosphatidylinositol 3-kinase (PI3K) isoforms during granulocyte differentiation of NB4 cells induced by all-trans-retinoic acid (ATRA), 9-cis-retinoic acid (9cisRA) or retinoic acid receptor (RAR) agonists. METHODS NB4 cells were analysed for their ability to differentiate into granulocytic lineage by the use of ATRA, 9cisRA or RAR agonists. Expression of signalling proteins was investigated by western blot and real-time PCR. PI3K activity was determined by in vitro kinase assays. RESULTS Co-treatment of NB4 cells with either LY294002 to inhibit PI3Ks or PD98059 in order to suppress MEK activity led to significant reduction of CD11b surface expression during ATRA, 9cisRA or the RAR alpha agonist Ro40-6055 dependent NB4 cells granulocyte differentiation. We also show that only the G-protein coupled receptor activated PI3Kgamma isoform demonstrates up-regulated protein and mRNA expression during myeloid differentiation of NB4 cells via RAR alpha and RAR beta-dependent mechanism. Furthermore, activation of MAPK cascade including phosphorylation of MEK increases during retinoid induced differentiation of NB4 cells. Interestingly, protein kinase assays of immunoprecipitated PI3Kgamma revealed a protein of about 50 kDa that is phosphorylated when NB4 cells were treated with the RAR alpha agonist Ro40-6055. CONCLUSION Collectively, our data suggest additive effects of PI3K and MAPK activity on ATRA-dependent NB4 cells granulocyte differentiation.
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Affiliation(s)
- Sebastian Scholl
- Department of Internal Medicine II, Medical Faculty at Friedrich Schiller University, Erlanger Allee 101, 07740, Jena, Germany.
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22
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Eickholt BJ, Ahmed AI, Davies M, Papakonstanti EA, Pearce W, Starkey ML, Bilancio A, Need AC, Smith AJH, Hall SM, Hamers FP, Giese KP, Bradbury EJ, Vanhaesebroeck B. Control of axonal growth and regeneration of sensory neurons by the p110delta PI 3-kinase. PLoS One 2007; 2:e869. [PMID: 17846664 PMCID: PMC1959241 DOI: 10.1371/journal.pone.0000869] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2007] [Accepted: 08/16/2007] [Indexed: 12/13/2022] Open
Abstract
The expression and function of the 8 distinct catalytic isoforms of PI 3-kinase (PI3K) in the nervous system are unknown. Whereas most PI3Ks have a broad tissue distribution, the tyrosine kinase-linked p110δ isoform has previously been shown to be enriched in leukocytes. Here we report that p110δ is also highly expressed in the nervous system. Inactivation of p110δ in mice did not affect gross neuronal development but led to an increased vulnerability of dorsal root ganglia neurons to exhibit growth cone collapse and decreases in axonal extension. Loss of p110δ activity also dampened axonal regeneration following peripheral nerve injury in adult mice and impaired functional recovery of locomotion. p110δ inactivation resulted in reduced neuronal signaling through the Akt protein kinase, and increased activity of the small GTPase RhoA. Pharmacological inhibition of ROCK, a downstream effector of RhoA, restored axonal extension defects in neurons with inactive p110δ, suggesting a key role of RhoA in p110δ signaling in neurons. Our data identify p110δ as an important signaling component for efficient axonal elongation in the developing and regenerating nervous system.
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Affiliation(s)
- Britta J Eickholt
- Medical Research Council Centre for Developmental Neurobiology, King's College London, London, United Kingdom.
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Fu Z, Aronoff-Spencer E, Wu H, Gerfen GJ, Backer JM. The iSH2 domain of PI 3-kinase is a rigid tether for p110 and not a conformational switch. Arch Biochem Biophys 2005; 432:244-51. [PMID: 15542063 PMCID: PMC3889214 DOI: 10.1016/j.abb.2004.09.032] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2004] [Indexed: 11/23/2022]
Abstract
Class IA PI 3-kinases are heterodimeric proteins with distinct catalytic (p110) and regulatory (p85) subunits. The minimal fragment of p85 capable of regulating p110 activity (p85ni) is the N-terminal SH2 domain linked to the iSH2 coiled-coil domain. We used cysteine mutagenesis and (14)C-NEM-labeling to show that the p110-binding site in the iSH2 domain includes two regions: residues 482-484 and 532-541. These regions are adjacent to each other in the three-dimensional structural model of the iSH2 domain, and define a coherent binding site. We then used spin labeling and EPR spectroscopy to demonstrate that the conformation of the iSH2 domain is unaffected by binding to the N-terminal fragment of p110 (residues 1-108), and/or by phosphopeptide binding to p85ni/p110(1-108) heterodimers. Finally, we show that the cSH2 domain cannot substitute for the nSH2 domain with regard to inhibition of p110. These data support a model in which the iSH2 domain is a rigid tether for p110, and regulation of p85/p110 is mediated by nSH2-p110 contacts.
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Affiliation(s)
- Zheng Fu
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY, USA
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24
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Rajala RVS, McClellan ME, Chan MD, Tsiokas L, Anderson RE. Interaction of the retinal insulin receptor beta-subunit with the p85 subunit of phosphoinositide 3-kinase. Biochemistry 2004; 43:5637-50. [PMID: 15134438 DOI: 10.1021/bi035913v] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Recently, we have shown that phosphoinositide 3-kinase (PI3K) in retina is regulated in vivo through light activation of the insulin receptor beta-subunit. In this study, we have cloned the 41 kDa cytoplasmic region of the retinal insulin receptor (IRbeta) and used the two-hybrid assay of protein-protein interaction in the yeast Saccharomyces cerevisiae to demonstrate the interaction between the p85 subunit of PI3K and the cytoplasmic region of IRbeta. Under conditions where IRbeta autophosphorylates, substitution of Y1322F and M1325P in IRbeta resulted in the abolition of p85 binding to the IRbeta, confirming that the p85 subunit of PI3K binds to Y1322. The binding site for p85 on IRbeta was also confirmed in the yeast three-hybrid system. Using the C-terminal region of IRbeta (amino acids 1293-1343 encompassing the YHTM motif) as bait and supplying an exogenous tyrosine kinase gene to yeast cells, we determined that the IRbeta-pYTHM motif interacts with p85. We also used retinal organ cultures to demonstrate insulin activation of the insulin receptor and subsequent binding of p85, measured through GST pull-down assays with p85 fusion proteins. Further, the Y960F mutant insulin receptor, which does not bind IRS-1, is capable of bringing down PI3K activity from retina lysates. On the other hand, in response to insulin, IRS-2 is able to interact with the p85 subunit of PI3K in the retina. These results suggest that multiple signaling pathways could regulate the PI3K activity and subsequent activation of Akt in the retina.
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Affiliation(s)
- Raju V S Rajala
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, USA.
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Scholl S, Kirsch C, Böhmer FD, Klinger R. Signal transduction of c-Kit receptor tyrosine kinase in CHRF myeloid leukemia cells. J Cancer Res Clin Oncol 2004; 130:711-8. [PMID: 15340843 DOI: 10.1007/s00432-004-0602-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2003] [Accepted: 06/26/2004] [Indexed: 11/24/2022]
Abstract
PURPOSE The tyrosine kinase receptor c-Kit (stem cell factor receptor, CD117) is a potential target for signal transduction therapy in different cancers. In this study we investigated c-Kit in CHRF cells, a megakaryoblastic cell line of Acute Myeloid Leukemia (FAB M7). MATERIALS AND METHODS We characterized the interactions between c-Kit and PI 3-kinase (p85) after stimulation with SCF (stem cell factor) as well as the regulation of SHP-1 and SHP-2 associated with Kit in this cell line. RESULTS Stimulation with SCF leads to a significant increase in interaction between Kit and p85 as well as in receptor associated PI 3-kinase activity. Interestingly, using different kinds of substances (AG 1295, CGP 53716) to inhibit the tyrosine kinase activity of c-Kit blocked activation of c-Kit, but the association of p85 still increased after SCF stimulation even when the tyrosine kinase activity of the receptor was completely blocked. In contrast, the other known interaction partners of c-Kit, SHP-1 and SHP-2, exhibited a basal association with c-Kit and no change of the association could be detected after stimulation of CHRF cells with SCF or treatment with the kinase inhibitors. CONCLUSIONS Therefore, we suggest that association of p85, SHP-1, and SHP-2 to c-Kit in CHRF cells can, at least in part, occur in a c-Kit kinase-activity independent manner. In contrast, the kinase activity of c-Kit is necessary for the activation of receptor-associated PI 3-kinase.
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Affiliation(s)
- Sebastian Scholl
- Department of Internal Medicine II (Hematology and Oncology), Friedrich Schiller University Jena, Germany.
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26
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Kossila M, Pihlajamäki J, Kärkkäinen P, Miettinen R, Kekäläinen P, Vauhkonen I, Ylä-Herttuala S, Laakso M. Promoter polymorphisms -359T/C and -303A/G of the catalytic subunit p110beta gene of human phosphatidylinositol 3-kinase are not associated with insulin secretion or insulin sensitivity in finnish subjects. Diabetes Care 2003; 26:179-82. [PMID: 12502677 DOI: 10.2337/diacare.26.1.179] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
OBJECTIVE Phosphatidylinositol (PI) 3-kinase activity is required for insulin-stimulated translocation of GLUT4 transporters and glucose uptake and utilization. Therefore, genes encoding the subunits of PI 3-kinase are promising candidate genes for insulin resistance and type 2 diabetes. We recently cloned the catalytic subunit p110beta gene of human PI 3-kinase and reported two nucleotide polymorphisms, -359T/C and -303A/G, in the promoter region of this gene. In this study, we determined the effects of these polymorphisms on insulin secretion and insulin sensitivity. RESEARCH DESIGN AND METHODS We studied two separate groups of Finnish nondiabetic subjects. Insulin secretion was evaluated by intravenous glucose tolerance test and insulin sensitivity by hyperinsulinemic-euglycemic clamp. RESULTS Our results showed that the -359T/C and -303A/G polymorphisms did not have a significant effect on fasting plasma insulin levels, insulin secretion, or insulin sensitivity. CONCLUSIONS It is unlikely that the promoter polymorphisms -359T/C and -303A/G of the catalytic subunit p110beta gene of human PI 3-kinase have a major impact on insulin secretion, insulin sensitivity, or the risk of type 2 diabetes in Finnish subjects.
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Affiliation(s)
- Maija Kossila
- A.I. Virtanen Institute for Molecular Sciences, Kuopio. Department of Medicine, University of Kuopio, Kuopio, Finland
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Krugmann S, Cooper MA, Williams DH, Hawkins PT, Stephens LR. Mechanism of the regulation of type IB phosphoinositide 3OH-kinase byG-protein betagamma subunits. Biochem J 2002; 362:725-31. [PMID: 11879201 PMCID: PMC1222438 DOI: 10.1042/0264-6021:3620725] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Type IB phosphoinositide 3OH-kinase (PI3K) is activated by G-protein betagamma subunits (Gbetagammas). The enzyme is soluble and largely cytosolic in vivo. Its substrate, PtdIns(4,5)P(2), and the Gbetagammas are localized at the plasma membrane. We have addressed the mechanism by which Gbetagammas regulate the PI3K using an in vitro approach. We used sedimentation assays and surface plasmon resonance to determine association of type IB PI3K with lipid monolayers and vesicles of varying compositions, some of which had Gbetagammas incorporated. Association and dissociation rate constants were determined. Our results indicated that in an assay situation in vitro the majority of PI3K will be associated with lipid vesicles, irrespective of the presence or absence of Gbetagammas. In line with this, a constitutively active membrane-targeted PI3K construct could still be activated substantially by Gbetagammas in vitro. We conclude that Gbetagammas activate type IB PI3K by a mechanism other than translocation to the plasma membrane.
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Affiliation(s)
- Sonja Krugmann
- Signalling Programme, The Babraham Institute, Babraham, Cambridge CB2 4AT, U.K
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29
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Bi L, Okabe I, Bernard DJ, Nussbaum RL. Early embryonic lethality in mice deficient in the p110beta catalytic subunit of PI 3-kinase. Mamm Genome 2002; 13:169-72. [PMID: 11919689 DOI: 10.1007/bf02684023] [Citation(s) in RCA: 127] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2001] [Accepted: 10/31/2001] [Indexed: 11/25/2022]
Affiliation(s)
- Lei Bi
- Genetic Diseases Research Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland 20892-4472, USA
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30
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Lefai E, Roques M, Vega N, Laville M, Vidal H. Expression of the splice variants of the p85alpha regulatory subunit of phosphoinositide 3-kinase in muscle and adipose tissue of healthy subjects and type 2 diabetic patients. Biochem J 2001; 360:117-26. [PMID: 11695998 PMCID: PMC1222208 DOI: 10.1042/0264-6021:3600117] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The regulation by insulin of the expression of the p85alpha regulatory subunit of phosphoinositide 3-kinase (PI 3-kinase) is impaired in skeletal muscle and adipose tissue of type 2 diabetic patients. The gene encoding p85alpha (named grb-1) can generate several variants by alternative splicing, all being able to activate the p110 catalytic subunits of PI 3-kinase. Our aims were (i) to determine the mRNA expression profiles of these variants in human skeletal muscle and adipose tissue; (ii) to investigate the effect of insulin on their expression in vivo and in vitro in muscle and (iii) to verify whether this regulation is defective in type 2 diabetes. We determined the human genomic organization of grb-1 and set up reverse transcriptase competitive PCR assays for the quantification of each mRNA variant. In muscle, p85alpha and p50alpha mRNAs were the most abundant, and p55alpha represented less than 20% of all grb-1-derived mRNAs. In adipose tissue, p85alpha was expressed predominantly and p55alpha mRNA was not detectable. These expression profiles were not different in type 2 diabetics. During a 3 h hyperinsulinaemic clamp, insulin increased the mRNA expression of the three variants in muscle of control subjects. In diabetic patients, the effect of insulin on p85alpha and p50alpha mRNAs was blunted, and largely reduced on p55alpha transcripts. In cultured human myotubes, up-regulation of p85alpha, p55alpha and p50alpha mRNAs by insulin was abolished by LY294002 (10 microM) and by rapamycin (50 nM), suggesting that the PI 3-kinase/protein kinase B/p70 S6 kinase pathway could be involved in the stimulation of grb-1 gene expression by insulin in human muscle cells.
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Affiliation(s)
- E Lefai
- INSERM U.449 and Lyon Human Nutrition Research Centre, Faculty of Medicine R. Laennec, F-69372 Lyon Cedex 08, France.
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Row PE, Reaves BJ, Domin J, Luzio JP, Davidson HW. Overexpression of a rat kinase-deficient phosphoinositide 3-kinase, Vps34p, inhibits cathepsin D maturation. Biochem J 2001; 353:655-61. [PMID: 11171063 PMCID: PMC1221612 DOI: 10.1042/0264-6021:3530655] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Lipid kinases and their phosphorylated products are important regulators of many cellular processes, including intracellular membrane traffic. The best example of this is provided by the class III phosphoinositide 3-kinase (PI-3K), Vps34p, which is required for correct targeting of newly synthesized carboxypeptidase Y to the yeast vacuole. A probable mammalian Vps34p orthologue has been previously identified, but its function in the trafficking of lysosomal enzymes has not been resolved. To investigate the possible role(s) of mammalian Vps34p in protein targeting to lysosomes, we have cloned the rat orthologue and overexpressed a kinase-deficient mutant in HeLa cells. Expression of the mutant protein inhibited both maturation of procathepsin D and basal secretion of the precursor. In contrast wortmannin, which also inhibited maturation, caused hypersecretion of the precursor. We propose that mammalian Vps34p plays a direct role in targeting lysosomal enzyme precursors to the endocytic pathway in an analogous fashion to its role in the fusion of early endocytic vesicles with endosomes. We further suggest that inhibition of a wortmannin-sensitive enzyme, other than mammalian Vps34p, is responsible for the failure to recycle unoccupied mannose 6-phosphate receptors to the trans-Golgi network, and consequent hypersecretion of lysosomal enzyme precursors observed in the presence of this drug.
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Affiliation(s)
- P E Row
- Wellcome Trust Centre for the Study of Molecular Mechanisms in Disease, University of Cambridge, Addenbrookes Hospital, Hills Road, Cambridge CB2 2XY, UK
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Siddhanta U, McIlroy J, Shah A, Zhang Y, Backer JM. Distinct roles for the p110alpha and hVPS34 phosphatidylinositol 3'-kinases in vesicular trafficking, regulation of the actin cytoskeleton, and mitogenesis. J Cell Biol 1998; 143:1647-59. [PMID: 9852157 PMCID: PMC2132989 DOI: 10.1083/jcb.143.6.1647] [Citation(s) in RCA: 134] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/1998] [Revised: 10/27/1998] [Indexed: 11/22/2022] Open
Abstract
We have examined the roles of the p85/ p110alpha and hVPS34 phosphatidylinositol (PI) 3'-kinases in cellular signaling using inhibitory isoform-specific antibodies. We raised anti-hVPS34 and anti-p110alpha antibodies that specifically inhibit recombinant hVPS34 and p110alpha, respectively, in vitro. We used the antibodies to study cellular processes that are sensitive to low-dose wortmannin. The antibodies had distinct effects on the actin cytoskeleton; microinjection of anti-p110alpha antibodies blocked insulin-stimulated ruffling, whereas anti-hVPS34 antibodies had no effect. The antibodies also had different effects on vesicular trafficking. Microinjection of inhibitory anti-hVPS34 antibodies, but not anti-p110alpha antibodies, blocked the transit of internalized PDGF receptors to a perinuclear compartment, and disrupted the localization of the early endosomal protein EEA1. Microinjection of anti-p110alpha antibodies, and to a lesser extent anti-hVPS34 antibodies, reduced the rate of transferrin recycling in CHO cells. Surprisingly, both antibodies inhibited insulin-stimulated DNA synthesis by 80%. Injection of cells with antisense oligonucleotides derived from the hVPS34 sequence also blocked insulin-stimulated DNA synthesis, whereas scrambled oligonucleotides had no effect. Interestingly, the requirement for p110alpha and hVPS34 occurred at different times during the G1-S transition. Our data suggest that different PI 3'-kinases play distinct regulatory roles in the cell, and document an unexpected role for hVPS34 during insulin-stimulated mitogenesis.
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Affiliation(s)
- U Siddhanta
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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Roche S, Downward J, Raynal P, Courtneidge SA. A function for phosphatidylinositol 3-kinase beta (p85alpha-p110beta) in fibroblasts during mitogenesis: requirement for insulin- and lysophosphatidic acid-mediated signal transduction. Mol Cell Biol 1998; 18:7119-29. [PMID: 9819398 PMCID: PMC109293 DOI: 10.1128/mcb.18.12.7119] [Citation(s) in RCA: 117] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/1998] [Accepted: 09/07/1998] [Indexed: 11/20/2022] Open
Abstract
We have previously shown that phosphatidylinositol 3-kinase alpha (PI 3-Kalpha) (p85alpha-p110alpha) is required for DNA synthesis induced by various growth factors (S. Roche, M. Koegl, and S. A. Courtneidge, Proc. Natl. Acad. Sci. USA 91:9185-9189, 1994) in fibroblasts. In the present study, we have investigated the function of PI 3-Kbeta (p85alpha-p110beta) during mitogenesis. By using antibodies specific to p110beta we showed that PI 3-Kbeta is expressed in NIH 3T3 cells. PI 3-Kbeta and PI 3-Kalpha have common features: PI 3-Kbeta is tightly associated with a protein serine kinase that phosphorylates p85alpha, it interacts with the Src-middle T antigen complex and the activated platelet-derived growth factor (PDGF) receptor in fibroblasts in vivo, and it becomes tyrosine phosphorylated after PDGF stimulation. PI 3-Kbeta was also activated in Swiss 3T3 and Cos7 cells stimulated with lysophosphatidic acid (LPA), a mitogen that interacts with a heterotrimeric G protein-coupled receptor. In contrast PI 3-Kalpha was activated to a lesser extent in these cells. Microinjection of neutralizing antibodies specific for p110beta into quiescent fibroblasts inhibited DNA synthesis induced by both insulin and LPA but poorly affected PDGF receptor signaling. Therefore, PI 3-Kbeta plays an important role in transmitting the mitogenic response induced by some, but not all, growth factors. Finally, we show that while oncogenic V12Ras interacts with type I PI 3-Ks, it could induce DNA synthesis in the absence of active PI 3-Kalpha and PI 3-Kbeta, suggesting that Ras uses other effectors for DNA synthesis.
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Affiliation(s)
- S Roche
- CNRS EP612 Faculté de Pharmacie, 34060 Montpellier, France.
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34
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Isakoff SJ, Cardozo T, Andreev J, Li Z, Ferguson KM, Abagyan R, Lemmon MA, Aronheim A, Skolnik EY. Identification and analysis of PH domain-containing targets of phosphatidylinositol 3-kinase using a novel in vivo assay in yeast. EMBO J 1998; 17:5374-87. [PMID: 9736615 PMCID: PMC1170863 DOI: 10.1093/emboj/17.18.5374] [Citation(s) in RCA: 271] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Phosphatidylinositol 3-kinase (PI3K) mediates a variety of cellular responses by generating PtdIns(3,4)P2 and PtdIns(3,4,5)P3. These 3-phosphoinositides then function directly as second messengers to activate downstream signaling molecules by binding pleckstrin homology (PH) domains in these signaling molecules. We have established a novel assay in the yeast Saccharomyces cerevisiae to identify proteins that bind PtdIns(3,4)P2 and PtdIns(3,4,5)P3 in vivo which we have called TOPIS (Targets of PI3K Identification System). The assay uses a plasma membrane-targeted Ras to complement a temperature-sensitive CDC25 Ras exchange factor in yeast. Coexpression of PI3K and a fusion protein of activated Ras joined to a PH domain known to bind PtdIns(3,4)P2 (AKT) or PtdIns(3,4,5)P3 (BTK) rescues yeast growth at the non-permissive temperature of 37 degreesC. Using this assay, we have identified several amino acids in the beta1-beta2 region of PH domains that are critical for high affinity binding to PtdIns(3,4)P2 and/or PtdIns(3,4,5)P3, and we have proposed a structural model for how these PH domains might bind PI3K products with high affinity. From these data, we derived a consensus sequence which predicts high-affinity binding to PtdIns(3, 4)P2 and/or PtdIns(3,4,5)P3, and we have identified several new PH domain-containing proteins that bind PI3K products, including Gab1, Dos, myosinX, and Sbf1. Use of this assay to screen for novel cDNAs which rescue yeast at the non-permissive temperature should provide a powerful approach for uncovering additional targets of PI3K.
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Affiliation(s)
- S J Isakoff
- The Skirball Institute for Biomolecular Medicine and Department of Pharmacology, New York University Medical Center, New York, NY 10016, USA
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35
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Kivens WJ, Hunt SW, Mobley JL, Zell T, Dell CL, Bierer BE, Shimizu Y. Identification of a proline-rich sequence in the CD2 cytoplasmic domain critical for regulation of integrin-mediated adhesion and activation of phosphoinositide 3-kinase. Mol Cell Biol 1998; 18:5291-307. [PMID: 9710614 PMCID: PMC109115 DOI: 10.1128/mcb.18.9.5291] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/1998] [Accepted: 06/10/1998] [Indexed: 11/20/2022] Open
Abstract
The CD2 molecule is one of several lymphocyte receptors that rapidly initiates signaling events regulating integrin-mediated cell adhesion. CD2 stimulation of resting human T cells results within minutes in an increase in beta1-integrin-mediated adhesion to fibronectin. We have utilized the HL60 cell line to map critical residues within the CD2 cytoplasmic domain involved in CD2 regulation of integrin function. A panel of CD2 cytoplasmic domain mutants was constructed and analyzed for their ability to upregulate integrin-mediated adhesion to fibronectin. Mutations in the CD2 cytoplasmic domain implicated in CD2-mediated interleukin-2 production or CD2 avidity do not affect CD2 regulation of integrin activity. A proline-rich sequence, K-G-P-P-L-P (amino acids 299 to 305), is essential for CD2-mediated regulation of beta1 integrin activity. CD2-induced increases in beta1 integrin activity could be blocked by two phosphoinositide 3-kinase (PI 3-K) inhibitors or by overexpression of a dominant negative form of the p85 subunit of PI 3-K. In addition, CD2 cytoplasmic domain mutations that abrogate CD2-induced increases in integrin-mediated adhesion also ablate CD2-induced increases in PI 3-K enzymatic activity. Surprisingly, CD2 cytoplasmic domain mutations that inhibit CD2 regulation of adhesion do not affect the constitutive association of the p85 subunit of PI 3-K association with CD2. Mutation of the proline residues in the K-G-P-P-L-P motif to alanines prevented CD2-mediated activation of integrin function and PI 3-K activity but not mitogen-activated protein (MAP) kinase activity. Furthermore, the MEK inhibitor PD 098059 blocked CD2-mediated activation of MAP kinase but had no effect on CD2-induced adhesion. These studies identify a proline-rich sequence in CD2 critical for PI 3-K-dependent regulation of beta1 integrin adhesion by CD2. In addition, these studies suggest that CD2-mediated activation of MAP kinase is not involved in CD2 regulation of integrin adhesion.
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Affiliation(s)
- W J Kivens
- Department of Laboratory Medicine and Pathology, Center for Immunology, and Cancer Center, University of Minnesota Medical School, Minneapolis, Minnesota 55455, USA
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36
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Shepherd PR, Withers DJ, Siddle K. Phosphoinositide 3-kinase: the key switch mechanism in insulin signalling. Biochem J 1998; 333 ( Pt 3):471-90. [PMID: 9677303 PMCID: PMC1219607 DOI: 10.1042/bj3330471] [Citation(s) in RCA: 727] [Impact Index Per Article: 28.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Insulin plays a key role in regulating a wide range of cellular processes. However, until recently little was known about the signalling pathways that are involved in linking the insulin receptor with downstream responses. It is now apparent that the activation of class 1a phosphoinositide 3-kinase (PI 3-kinase) is necessary and in some cases sufficient to elicit many of insulin's effects on glucose and lipid metabolism. The lipid products of PI 3-kinase act as both membrane anchors and allosteric regulators, serving to localize and activate downstream enzymes and their protein substrates. One of the major ways these lipid products of PI 3-kinase act in insulin signalling is by binding to pleckstrin homology (PH) domains of phosphoinositide-dependent protein kinase (PDK) and protein kinase B (PKB) and in the process regulating the phosphorylation of PKB by PDK. Using mechanisms such as this, PI 3-kinase is able to act as a molecular switch to regulate the activity of serine/threonine-specific kinase cascades important in mediating insulin's effects on endpoint responses.
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Affiliation(s)
- P R Shepherd
- Department of Biochemistry and Molecular Biology, University College London, Gower Street, London WC1E 6BT, UK.
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37
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Melendez AJ, Gillooly DJ, Harnett MM, Allen JM. Aggregation of the human high affinity immunoglobulin G receptor (FcgammaRI) activates both tyrosine kinase and G protein-coupled phosphoinositide 3-kinase isoforms. Proc Natl Acad Sci U S A 1998; 95:2169-74. [PMID: 9482857 PMCID: PMC19285 DOI: 10.1073/pnas.95.5.2169] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Phosphoinositide 3-kinases (PI3-kinases) play an important role in the generation of lipid second messengers and the transduction of a myriad of biological responses. Distinct isoforms have been shown to be exclusively activated either by tyrosine kinase-coupled or G protein-coupled receptors. We show here, however, that certain nonclassical receptors can couple to both tyrosine kinase- and G protein-dependent isoforms of PI3-kinase: thus, aggregation of FcgammaRI, the human high affinity IgG receptor, on monocytes unusually leads to activation of both of these types of PI3-kinase. After aggregation of FcgammaRI, phosphatidylinositol 3,4, 5-triphosphate (PIP3) levels rise rapidly in interferon gamma-primed cells, reaching a peak within 30 sec. Moreover, and in contrast to the situation observed after stimulation of these cells with either insulin or ATP, which exclusively activate the tyrosine kinase- and G protein-coupled forms of PI3-kinase, respectively, PIP3 levels remain elevated up to 15 min after receptor aggregation. We show here that although the initial peak results from transient activation of the p85-dependent p110 isoform of PI-3kinase, presumably through recruitment of tyrosine kinases by the gamma chain, the later sustained rise of PIP3 results from activation of the G protein betagamma subunit-sensitive isoform, p110gamma. This finding indicates that receptors lacking an intrinsic signaling motif, such as FcgammaRI, can recruit both tyrosine kinase and G protein-coupled intracellular signaling molecules and thereby initiate cellular responses.
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Affiliation(s)
- A J Melendez
- Department of Medicine and Therapeutics and Division of Biochemistry and Molecular Biology, University of Glasgow, Glasgow G12 8QQ, Scotland, United Kingdom
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38
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Yu J, Zhang Y, McIlroy J, Rordorf-Nikolic T, Orr GA, Backer JM. Regulation of the p85/p110 phosphatidylinositol 3'-kinase: stabilization and inhibition of the p110alpha catalytic subunit by the p85 regulatory subunit. Mol Cell Biol 1998; 18:1379-87. [PMID: 9488453 PMCID: PMC108851 DOI: 10.1128/mcb.18.3.1379] [Citation(s) in RCA: 399] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/1997] [Accepted: 12/01/1997] [Indexed: 02/06/2023] Open
Abstract
We propose a novel model for the regulation of the p85/pl10alpha phosphatidylinositol 3'-kinase. In insect cells, the p110alpha catalytic subunit is active as a monomer but its activity is decreased by coexpression with the p85 regulatory subunit. Similarly, the lipid kinase activity of recombinant glutathione S-transferase (GST)-p110alpha is reduced by 65 to 85% upon in vitro reconstitution with p85. Incubation of p110alpha/p85 dimers with phosphotyrosyl peptides restored activity, but only to the level of monomeric p110alpha. These data show that the binding of phosphoproteins to the SH2 domains of p85 activates the p85/p110alpha dimers by inducing a transition from an inhibited to a disinhibited state. In contrast, monomeric p110 had little activity in HEK 293T cells, and its activity was increased 15- to 20-fold by coexpression with p85. However, this apparent requirement for p85 was eliminated by the addition of a bulky tag to the N terminus of p110alpha or by the growth of the HEK 293T cells at 30 degrees C. These nonspecific interventions mimicked the effects of p85 on p110alpha, suggesting that the regulatory subunit acts by stabilizing the overall conformation of the catalytic subunit rather than by inducing a specific activated conformation. This stabilization was directly demonstrated in metabolically labeled HEK 293T cells, in which p85 increased the half-life of p110. Furthermore, p85 protected p110 from thermal inactivation in vitro. Importantly, when we examined the effect of p85 on GST-p110alpha in mammalian cells at 30 degrees C, culture conditions that stabilize the catalytic subunit and that are similar to the conditions used for insect cells, we found that p85 inhibited p110alpha. Thus, we have experimentally distinguished two effects of p85 on p110alpha: conformational stabilization of the catalytic subunit and inhibition of its lipid kinase activity. Our data reconcile the apparent conflict between previous studies of insect versus mammalian cells and show that p110alpha is both stabilized and inhibited by dimerization with p85.
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Affiliation(s)
- J Yu
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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39
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Jimenez C, Jones DR, Rodríguez-Viciana P, Gonzalez-García A, Leonardo E, Wennström S, von Kobbe C, Toran JL, R-Borlado L, Calvo V, Copin SG, Albar JP, Gaspar ML, Diez E, Marcos MA, Downward J, Martinez-A C, Mérida I, Carrera AC. Identification and characterization of a new oncogene derived from the regulatory subunit of phosphoinositide 3-kinase. EMBO J 1998; 17:743-53. [PMID: 9450999 PMCID: PMC1170423 DOI: 10.1093/emboj/17.3.743] [Citation(s) in RCA: 201] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
p85/p110 phosphoinositide 3-kinase (PI3K) is a heterodimer composed of a p85-regulatory and a p110-catalytic subunit, which is involved in a variety of cellular responses including cytoskeletal organization, cell survival and proliferation. We describe here the cloning and characterization of p65-PI3K, a mutant of the regulatory subunit of PI3K, which includes the initial 571 residues of the wild type p85alpha-protein linked to a region conserved in the eph tyrosine kinase receptor family. We demonstrate that this mutation, obtained from a transformed cell, unlike previously engineered mutations of the regulatory subunit, induces the constitutive activation of PI3K and contributes to cellular transformation. This report links the PI3K enzyme to mammalian tumor development for the first time.
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Affiliation(s)
- C Jimenez
- Department of Immunology and Oncology, Centro Nacional de Biotecnología, Universidad Autónoma de Madrid, Cantoblanco, Madrid E-28049, Spain
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40
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Logan SK, Falasca M, Hu P, Schlessinger J. Phosphatidylinositol 3-kinase mediates epidermal growth factor-induced activation of the c-Jun N-terminal kinase signaling pathway. Mol Cell Biol 1997; 17:5784-90. [PMID: 9315636 PMCID: PMC232426 DOI: 10.1128/mcb.17.10.5784] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The signaling events which mediate activation of c-Jun N-terminal kinase (JNK) are not yet well characterized. To broaden our understanding of upstream mediators which link extracellular signals to the JNK pathway, we investigated the role of phosphatidylinositol (PI) 3-kinase in epidermal growth factor (EGF)-mediated JNK activation. In this report we demonstrate that a dominant negative form of PI 3-kinase as well as the inhibitor wortmannin blocks EGF-induced JNK activation dramatically. However, wortmannin does not have an effect on JNK activation induced by UV irradiation or osmotic shock. In addition, a membrane-targeted, constitutively active PI 3-kinase (p110beta) was shown to produce in vivo products and to activate JNK, while a kinase-mutated form of this protein showed no activation. On the basis of these experiments, we propose that PI 3-kinase activity plays a role in EGF-induced JNK activation in these cells.
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Affiliation(s)
- S K Logan
- Department of Pharmacology, New York University Medical Center, New York 10016, USA
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41
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Domin J, Pages F, Volinia S, Rittenhouse SE, Zvelebil MJ, Stein RC, Waterfield MD. Cloning of a human phosphoinositide 3-kinase with a C2 domain that displays reduced sensitivity to the inhibitor wortmannin. Biochem J 1997; 326 ( Pt 1):139-47. [PMID: 9337861 PMCID: PMC1218647 DOI: 10.1042/bj3260139] [Citation(s) in RCA: 201] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The generation of phosphatidylinositide 3-phosphates has been observed in a variety of cellular responses. The enzymes that mediate synthesis are the phosphoinositide 3-kinases (PI3-Ks) that form a family of structurally diverse enzymes with distinct substrate specificities. In this paper, we describe the cloning of a novel human PI3-K, namely PI3-K-C2 alpha, which contains a C-terminal C2 domain. This enzyme can be assigned to the class II PI3-Ks, which was defined by characterization of the Drosophila 68D enzyme and includes the recently described murine enzymes m-cpk and p170. Despite the overall similarity in the amino acid sequence of the murine and human enzymes, which suggests that they are encoded by closely related genes, these molecules show marked sequence heterogeneity at their N-termini. Biochemical analysis of recombinant PI3-K-C2 alpha demonstrates a restricted lipid substrate specificity. As reported for other members of this class, the enzyme only phosphorylates PtdIns and PtdIns4P when the lipids are presented alone. However, when lipids were presented together with phosphatidylserine acting as a carrier, phosphorylation of PtdIns(4,5)P2 was also observed. The catalytic activity of PI3-K-C2 alpha is refractory to concentrations of wortmannin and LY294002 which inhibit the PI3-K activity of other family members. The comparative insensitivity of PI3-K-C2 alpha to these inhibitors suggests that their use should be reevaluated in the study of PI3-Ks.
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Affiliation(s)
- J Domin
- Ludwig Institute for Cancer Research, London, U.K
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42
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Ptasznik A, Beattie GM, Mally MI, Cirulli V, Lopez A, Hayek A. Phosphatidylinositol 3-kinase is a negative regulator of cellular differentiation. J Cell Biol 1997; 137:1127-36. [PMID: 9166412 PMCID: PMC2136228 DOI: 10.1083/jcb.137.5.1127] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/1997] [Revised: 03/21/1997] [Indexed: 02/04/2023] Open
Abstract
Phosphatidylinositol 3-kinase (PI3K) has been shown to be an important mediator of intracellular signal transduction in mammalian cells. We show here, for the first time, that the blockade of PI3K activity in human fetal undifferentiated cells induced morphological and functional endocrine differentiation. This was associated with an increase in mRNA levels of insulin, glucagon, and somatostatin, as well as an increase in the insulin protein content and secretion in response to secretagogues. Blockade of PI3K also increased the proportion of pluripotent precursor cells coexpressing multiple hormones and the total number of terminally differentiated cells originating from these precursor cells. We examined whether any of the recently described modulators of endocrine differentiation could participate in regulating PI3K activity in fetal islet cells. The activity of PI3K was inversely correlated with the hepatocyte growth factor/scatter factor-induced downregulation or nicotinamideinduced upregulation of islet-specific gene expression, giving support to the role of PI3K, as a negative regulator of endocrine differentiation. In conclusion, our results provide a mechanism for the regulation of hormone-specific gene expression during human fetal neogenesis. They also suggest a novel function for PI3K, as a negative regulator of cellular differentiation.
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Affiliation(s)
- A Ptasznik
- The Whittier Institute for Diabetes and Endocrinology, Department of Pediatrics, University of California at San Diego, School of Medicine, La Jolla, California 92037, USA
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43
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Stoyanova S, Bulgarelli-Leva G, Kirsch C, Hanck T, Klinger R, Wetzker R, Wymann MP. Lipid kinase and protein kinase activities of G-protein-coupled phosphoinositide 3-kinase gamma: structure-activity analysis and interactions with wortmannin. Biochem J 1997; 324 ( Pt 2):489-95. [PMID: 9182708 PMCID: PMC1218456 DOI: 10.1042/bj3240489] [Citation(s) in RCA: 92] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Signalling via seven transmembrane helix receptors can lead to a massive increase in cellular PtdIns(3,4,5)P3, which is critical for the induction of various cell responses and is likely to be produced by a trimeric G-protein-sensitive phosphoinositide 3-kinase (PI3Kgamma). We show here that PI3Kgamma is a bifunctional lipid kinase and protein kinase, and that both activities are inhibited by wortmannin at concentrations equal to those affecting the p85/p110alpha heterodimeric PI3K (IC50 approx. 2 nM). The binding of wortmannin to PI3Kgamma, as detected by anti-wortmannin antisera, closely followed the inhibition of the kinase activities. Truncation of more than the 98 N-terminal amino acid residues from PI3Kgamma produced proteins that were inactive in wortmannin binding and kinase assays. This suggests that regions apart from the core catalytic domain are important in catalysis and inhibitor interaction. The covalent reaction of wortmannin with PI3Kgamma was prevented by preincubation with phosphoinositides, ATP and its analogues adenine and 5'-(4-fluorosulphonylbenzoyl)adenine. Proteolytic analysis of wortmannin-prelabelled PI3Kgamma revealed candidate wortmannin-binding peptides around Lys-799. Replacement of Lys-799 by Arg through site-directed mutagenesis aborted the covalent reaction with wortmannin and the lipid kinase and protein kinase activities completely. The above illustrates that Lys-799 is crucial to the phosphate transfer reaction and wortmannin reactivity. Parallel inhibition of the PI3Kgamma-associated protein kinase and lipid kinase by wortmannin and by the Lys-799-->Arg mutation reveals that both activities are inherent in the PI3Kgamma polypeptide.
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Affiliation(s)
- S Stoyanova
- Institute of Biochemistry II, Medical Faculty of the Friedrich Schiller University, Löbderstrasse 3, D-07743 Jena, Federal Republic of Germany
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44
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Vanhaesebroeck B, Welham MJ, Kotani K, Stein R, Warne PH, Zvelebil MJ, Higashi K, Volinia S, Downward J, Waterfield MD. P110delta, a novel phosphoinositide 3-kinase in leukocytes. Proc Natl Acad Sci U S A 1997; 94:4330-5. [PMID: 9113989 PMCID: PMC20722 DOI: 10.1073/pnas.94.9.4330] [Citation(s) in RCA: 351] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Phosphoinositide 3-kinases (PI3Ks) are a family of lipid kinases that have been implicated in signal transduction through tyrosine kinase- and heterotrimeric G-protein-linked receptors. We report herein the cloning and characterization of p110delta, a novel class I PI3K. Like p110alpha and p110beta, other class I PI3Ks, p110delta displays a broad phosphoinositide lipid substrate specificity and interacts with SH2/SH3 domain-containing p85 adaptor proteins and with GTP-bound Ras. In contrast to the widely distributed p110alpha and beta, p110delta is exclusively found in leukocytes. In these cells, p110alpha and delta both associate with the p85alpha and beta adaptor subunits and are similarly recruited to activated signaling complexes after treatment with the cytokines interleukin 3 and 4 and stem cell factor. Thus, these class I PI3Ks appear not to be distinguishable at the level of p85 adaptor selection or recruitment to activated receptor complexes. However, distinct biochemical and structural features of p110delta suggest divergent functional/regulatory capacities for this PI3K. Unlike p110alpha, p110delta does not phosphorylate p85 but instead harbors an intrinsic autophosphorylation capacity. In addition, the p110delta catalytic domain contains unique potential protein-protein interaction modules such as a Pro-rich region and a basic-region leucine-zipper (bZIP)-like domain. Possible selective functions of p110delta in white blood cells are discussed.
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Affiliation(s)
- B Vanhaesebroeck
- Ludwig Institute for Cancer Research, 91 Riding House Street, London W1P 8BT, United Kingdom
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Linassier C, MacDougall LK, Domin J, Waterfield MD. Molecular cloning and biochemical characterization of a Drosophila phosphatidylinositol-specific phosphoinositide 3-kinase. Biochem J 1997; 321 ( Pt 3):849-56. [PMID: 9032475 PMCID: PMC1218144 DOI: 10.1042/bj3210849] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Molecular, biochemical and genetic characterization of phosphoinositide 3-kinases (PI3Ks) have identified distinct classes of enzymes involved in processes mediated by activation of cell-surface receptors and in constitutive intracellular protein trafficking events. The latter process appears to involve a PtdIns-specific PI3K first described in yeast as a mutant, vps34, defective in the sorting of newly synthesized proteins from the Golgi to the vacuole. We have identified a representative member of each class of PI3Ks in Drosophila using a PCR-based approach. In the present paper we describe the molecular cloning of a PI3K from Drosophila, P13K_59F, that shows sequence similarity to Vps34. PI3K_59F encodes a protein of 108 kDa co-linear with Vps34 homologues, and with three regions of sequence similarity to other PI3Ks. Biochemical characterization of the enzyme, by expression of the complete coding sequence as a glutathione S-transferase fusion protein in Sf9 cells, demonstrates that PI3K_59F is a PtdIns-specific PI3K that can utilize either Mg2+ or Mn2+. This activity is sensitive to inhibition both by non-ionic detergent (Nonidet P40) and by wortmannin (IC50 10 nM). PI3K_59F, therefore, conserves both the structural and biochemical properties of the Vps34 class of enzymes.
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Affiliation(s)
- C Linassier
- Ludwig Institute for Cancer Research, University College London, U.K
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McIlroy J, Chen D, Wjasow C, Michaeli T, Backer JM. Specific activation of p85-p110 phosphatidylinositol 3'-kinase stimulates DNA synthesis by ras- and p70 S6 kinase-dependent pathways. Mol Cell Biol 1997; 17:248-55. [PMID: 8972205 PMCID: PMC231749 DOI: 10.1128/mcb.17.1.248] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
We have developed a polyclonal antibody that activates the heterodimeric p85-p110 phosphatidylinositol (PI) 3'-kinase in vitro and in microinjected cells. Affinity purification revealed that the activating antibody recognized the N-terminal SH2 (NSH2) domain of p85, and the antibody increased the catalytic activity of recombinant p85-p110 dimers threefold in vitro. To study the role of endogenous PI 3'-kinase in intact cells, the activating anti-NSH2 antibody was microinjected into GRC + LR73 cells, a CHO cell derivative selected for tight quiescence during serum withdrawal. Microinjection of anti-NSH2 antibodies increased bromodeoxyuridine (BrdU) incorporation fivefold in quiescent cells and enhanced the response to serum. These data reflect a specific activation of PI 3'-kinase, as the effect was blocked by coinjection of the appropriate antigen (glutathione S-transferase-NSH2 domains from p85 alpha), coinjection of inhibitory anti-p110 antibodies, or treatment of cells with wortmannin. We used the activating antibodies to study signals downstream from PI 3'-kinase. Although treatment of cells with 50 nM rapamycin only partially decreased anti-NSH2-stimulated BrdU incorporation, coinjection with an anti-p70 S6 kinase antibody effectively blocked anti-NSH2-stimulated DNA synthesis. We also found that coinjection of inhibitory anti-ras antibodies blocked both serum- and anti-NSH2-stimulated BrdU incorporation by approximately 60%, and treatment of cells with a specific inhibitor of MEK abolished antibody-stimulated BrdU incorporation. We conclude that selective activation of physiological levels of PI 3'-kinase is sufficient to stimulate DNA synthesis in quiescent cells. PI 3'-kinase-mediated DNA synthesis requires both p70 S6 kinase and the P21ras/MEK pathway.
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Affiliation(s)
- J McIlroy
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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Abstract
The C2 domain is a Ca(2+)-binding motif of approximately 130 residues in length originally identified in the Ca(2+)-dependent isoforms of protein kinase C. Single and multiple copies of C2 domains have been identified in a growing number of eukaryotic signalling proteins that interact with cellular membranes and mediate a broad array of critical intracellular processes, including membrane trafficking, the generation of lipid-second messengers, activation of GTPases, and the control of protein phosphorylation. As a group, C2 domains display the remarkable property of binding a variety of different ligands and substrates, including Ca2+, phospholipids, inositol polyphosphates, and intracellular proteins. Expanding this functional diversity is the fact that not all proteins containing C2 domains are regulated by Ca2+, suggesting that some C2 domains may play a purely structural role or may have lost the ability to bind Ca2+. The present review summarizes the information currently available regarding the structure and function of the C2 domain and provides a novel sequence alignment of 65 C2 domain primary structures. This alignment predicts that C2 domains form two distinct topological folds, illustrated by the recent crystal structures of C2 domains from synaptotagmin 1 and phosphoinositide-specific phospholipase C-delta 1, respectively. The alignment highlights residues that may be critical to the C2 domain fold or required for Ca2+ binding and regulation.
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Affiliation(s)
- E A Nalefski
- Department of Chemistry and Biochemistry, University of Colorado, Boulder 80309-0215, USA
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Kanagasundaram V, Jaworowski A, Hamilton JA. Association between phosphatidylinositol-3 kinase, Cbl and other tyrosine phosphorylated proteins in colony-stimulating factor-1-stimulated macrophages. Biochem J 1996; 320 ( Pt 1):69-77. [PMID: 8947469 PMCID: PMC1217899 DOI: 10.1042/bj3200069] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Colony stimulating factor-1 (CSF-1) stimulation of the macrophage cell line BAC1.2F5 and murine bone marrow-derived macrophages resulted in tyrosine phosphorylation of phosphatidylinositol-3 kinase (PI-3 kinase) p85 alpha and its stable association with several tyrosine phosphorylated proteins, including CSF-1 receptor (p165), p120, p95 and p55-p60. p120 co-migrated with the product of the protooncogene c-cb1 in anti-p85 alpha immunoprecipitates, and associated with p85 alpha in a rapid and transient manner. Reciprocal experiments confirmed the presence of p85 alpha in anti-Cb1 immunoprecipitates on CSF-1 stimulation of macrophages. PI-3 kinase immunoprecipitates from the myeloid FDC-P1 cell line expressing mutant CSF-1 receptor (Y721F), which does not associate with PI-3 kinase, still contained Cbl. The identity of the tyrosine phosphorylated protein p95 remains unknown. The interaction between p85 alpha and the tyrosine phosphorylated proteins survived anion-exchange chromatography, suggesting perhaps the presence of a stable complex; furthermore, in CSF-1-treated BAC1.2F5 cell extracts, only one of the two pools of PI-3 kinase separated by chromatography was present in this putative complex. The association did not appear to correlate with proliferation, since a similar interaction between p85 alpha and tyrosine phosphorylated proteins was also observed in poorly proliferating resident peritoneal macrophages stimulated with CSF-1. The possible significance of these findings for CSF-1-regulated macrophage functions is discussed.
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Affiliation(s)
- V Kanagasundaram
- University of Melbourne, Department of Medicine, Royal Melbourne Hospital, Parkville, Victoria, Australia
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Wymann MP, Bulgarelli-Leva G, Zvelebil MJ, Pirola L, Vanhaesebroeck B, Waterfield MD, Panayotou G. Wortmannin inactivates phosphoinositide 3-kinase by covalent modification of Lys-802, a residue involved in the phosphate transfer reaction. Mol Cell Biol 1996; 16:1722-33. [PMID: 8657148 PMCID: PMC231159 DOI: 10.1128/mcb.16.4.1722] [Citation(s) in RCA: 524] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Wortmannin at nanomolar concentrations is a potent and specific inhibitor of phosphoinositide (PI) 3-kinase and has been used extensively to demonstrate the role of this enzyme in diverse signal transduction processes. At higher concentrations, wortmannin inhibits the ataxia telangiectasia gene (ATM)-related DNA-dependent protein kinase (DNA-PKcs). We report here the identification of the site of interaction of wortmannin on the catalytic subunit of PI 3-kinase, p110alpha. At physiological pH (6.5 to 8) wortmannin reacted specifically with p110alpha. Phosphatidylinositol-4,5-diphosphate, ATP, and ATP analogs [adenine and 5'-(4-fluorosulfonylbenzoyl)adenine] competed effectively with wortmannin, while substances containing nucleophilic amino acid side chain functions had no effect at the same concentrations. This suggests that the wortmannin target site is localized in proximity to the substrate-binding site and that residues involved in wortmannin binding have an increased nucleophilicity because of their protein environment. Proteolytic fragments of wortmannin-treated, recombinant p110alpha were mapped with anti-wortmannin and anti-p110alpha peptide antibodies, thus limiting the target site within a 10-kDa fragment, colocalizing with the ATP-binding site. Site-directed mutagenesis of all candidate residues within this region showed that only the conservative Lys-802-to-Arg mutation abolished wortmannin binding. Inhibition of PI 3-kinase occurs, therefore, by the formation of an enamine following the attack of Lys-802 on the furan ring (at C-20) of wortmannin. The Lys-802-to-Arg mutant was also unable to bind FSBA and was catalytically inactive in lipid and protein kinase assays, indicating a crucial role for Lys-802 in the phosphotransfer reaction. In contrast, an Arg-916-to-Pro mutation abolished the catalytic activity whereas covalent wortmannin binding remained intact. Our results provide the basis for the design of novel and specific inhibitors of an enzyme family, including PI kinases and ATM-related genes, that play a central role in many physiological processes.
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Affiliation(s)
- M P Wymann
- Institute of Biochemistry, University of Fribourg, Switzerland
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Shimizu Y, Mobley JL, Finkelstein LD, Chan AS. A role for phosphatidylinositol 3-kinase in the regulation of beta 1 integrin activity by the CD2 antigen. J Cell Biol 1995; 131:1867-80. [PMID: 8557753 PMCID: PMC2120662 DOI: 10.1083/jcb.131.6.1867] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The rapid and reversible upregulation of the functional activity of integrin receptors on T lymphocytes is a vital step in the adhesive interactions that occur during successful T cell recognition of foreign antigen and transendothelial migration. Although the ligation of several different cell surface receptors, including the antigen-specific CD3/T cell receptor complex, the CD2, CD7, and CD28 antigens, as well as several chemokine receptors, has been shown to rapidly upregulate integrin function, the intracellular signaling events that initiate this increase in adhesion remain poorly defined. In this study, we have used DNA-mediated gene transfer to explore the role of phosphatidylinositol 3-kinase (PI 3-K) in the upregulation of beta 1 integrin functional activity mediated by the CD2 antigen. CD2 was expressed in the myelomonocytic cell line HL60, which expresses beta 1 integrins that mediate adhesion to fibronectin and VCAM-1 in an activation-dependent manner. Antibody stimulation of CD2 expressed on HL60 transfectants resulted within minutes in increased beta 1-mediated adhesion to fibronectin and VCAM-1 at levels comparable to that obtained upon stimulation with the phorbol ester PMA. A role for PI 3-K in CD2-mediated increases in beta 1 integrin function is suggested by: (a) the ability of the PI 3-K inhibitor wortmannin to completely inhibit CD2-induced increases in beta 1 integrin activity; (b) the association of PI 3-K with CD2; and (c) induced PI 3-K activity upon CD2 stimulation. The mode of association of PI 3-K with CD2 is not mediated by tyrosine phosphorylation-dependent binding of PI 3-K via SH2 domains, since: (a) PI 3-K is associated with CD2 in unstimulated cells; (b) CD2 stimulation fails to increase the amount of associated PI 3-K; and (c) the CD2 cytoplasmic domain lacks tyrosine residues. A role for both protein kinase C and cytoskeletal rearrangements in CD2 regulation of integrin activity is also suggested, since a PKC inhibitor partially inhibits CD2-induced increases in beta 1 integrin function, and CD2 stimulation increases F-actin content in a wortmannin-sensitive manner. Analysis of human peripheral T cells indicated that CD2 stimulation also results in PI 3-K-dependent upregulation of beta 1 integrin activity. Thus, these results demonstrate that CD2 can function as an adhesion regulator in the absence of expression of the CD3/T cell receptor complex; and directly implicate PI 3-K as a critical intracellular mediator involved in the regulation of beta 1 integrin functional activity by the CD2 antigen.
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Affiliation(s)
- Y Shimizu
- Department of Laboratory Medicine and Pathology, University of Minnesota Medical School, Minneapolis 55455, USA
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