1
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Nadel G, Yao Z, Hacohen-Lev-Ran A, Wainstein E, Maik-Rachline G, Ziv T, Naor Z, Admon A, Seger R. Phosphorylation of PP2Ac by PKC is a key regulatory step in the PP2A-switch-dependent AKT dephosphorylation that leads to apoptosis. Cell Commun Signal 2024; 22:154. [PMID: 38419089 PMCID: PMC10900696 DOI: 10.1186/s12964-024-01536-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2023] [Accepted: 02/17/2024] [Indexed: 03/02/2024] Open
Abstract
BACKGROUND Although GqPCR activation often leads to cell survival by activating the PI3K/AKT pathway, it was previously shown that in several cell types AKT activity is reduced and leads to JNK activation and apoptosis. The mechanism of AKT inactivation in these cells involves an IGBP1-coupled PP2Ac switch that induces the dephosphorylation and inactivation of both PI3K and AKT. However, the machinery involved in the initiation of PP2A switch is not known. METHODS We used phospho-mass spectrometry to identify the phosphorylation site of PP2Ac, and raised specific antibodies to follow the regulation of this phosphorylation. Other phosphorylations were monitored by commercial antibodies. In addition, we used coimmunoprecipitation and proximity ligation assays to follow protein-protein interactions. Apoptosis was detected by a TUNEL assay as well as PARP1 cleavage using SDS-PAGE and Western blotting. RESULTS We identified Ser24 as a phosphorylation site in PP2Ac. The phosphorylation is mediated mainly by classical PKCs (PKCα and PKCβ) but not by novel PKCs (PKCδ and PKCε). By replacing the phosphorylated residue with either unphosphorylatable or phosphomimetic residues (S24A and S24E), we found that this phosphorylation event is necessary and sufficient to mediate the PP2A switch, which ultimately induces AKT inactivation, and a robust JNK-dependent apoptosis. CONCLUSION Our results show that the PP2A switch is induced by PKC-mediated phosphorylation of Ser24-PP2Ac and that this phosphorylation leads to apoptosis upon GqPCR induction of various cells. We propose that this mechanism may provide an unexpected way to treat some cancer types or problems in the endocrine machinery.
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Affiliation(s)
- Guy Nadel
- Department of Immunology and Regenerative Biology, the Weizmann Institute of Science, Rehovot, Israel
| | - Zhong Yao
- Department of Immunology and Regenerative Biology, the Weizmann Institute of Science, Rehovot, Israel
| | - Avital Hacohen-Lev-Ran
- Department of Immunology and Regenerative Biology, the Weizmann Institute of Science, Rehovot, Israel
| | - Ehud Wainstein
- Department of Immunology and Regenerative Biology, the Weizmann Institute of Science, Rehovot, Israel
| | - Galia Maik-Rachline
- Department of Immunology and Regenerative Biology, the Weizmann Institute of Science, Rehovot, Israel
| | - Tamar Ziv
- Smoler Proteomic Center, Technion-Israel Institute of Technology, Haifa, Israel
| | - Zvi Naor
- Department of Biochemistry and Molecular Biology, Tel Aviv University, Tel Aviv, Israel
| | - Arie Admon
- Faculty of Biology, Technion-Israel Institute of Technology, Haifa, Israel
| | - Rony Seger
- Department of Immunology and Regenerative Biology, the Weizmann Institute of Science, Rehovot, Israel.
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2
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Tsay A, Wang JC. The Role of PIK3R1 in Metabolic Function and Insulin Sensitivity. Int J Mol Sci 2023; 24:12665. [PMID: 37628845 PMCID: PMC10454413 DOI: 10.3390/ijms241612665] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Revised: 08/04/2023] [Accepted: 08/08/2023] [Indexed: 08/27/2023] Open
Abstract
PIK3R1 (also known as p85α) is a regulatory subunit of phosphoinositide 3-kinases (PI3Ks). PI3K, a heterodimer of a regulatory subunit and a catalytic subunit, phosphorylates phosphatidylinositol into secondary signaling molecules involved in regulating metabolic homeostasis. PI3K converts phosphatidylinositol 4,5-bisphosphate (PIP2) to phosphatidylinositol 3,4,5-triphosphate (PIP3), which recruits protein kinase AKT to the inner leaflet of the cell membrane to be activated and to participate in various metabolic functions. PIK3R1 stabilizes and inhibits p110 catalytic activity and serves as an adaptor to interact with insulin receptor substrate (IRS) proteins and growth factor receptors. Thus, mutations in PIK3R1 or altered expression of PIK3R1 could modulate the activity of PI3K and result in significant metabolic outcomes. Interestingly, recent studies also found PI3K-independent functions of PIK3R1. Overall, in this article, we will provide an updated review of the metabolic functions of PIK3R1 that includes studies of PIK3R1 in various metabolic tissues using animal models, the mechanisms modulating PIK3R1 activity, and studies on the mutations of human PIK3R1 gene.
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Affiliation(s)
- Ariel Tsay
- Metabolic Biology Graduate Program, University of California Berkeley, Berkeley, CA 94720, USA;
- Department of Nutritional Sciences & Toxicology, University of California Berkeley, Berkeley, CA 94720, USA
| | - Jen-Chywan Wang
- Metabolic Biology Graduate Program, University of California Berkeley, Berkeley, CA 94720, USA;
- Department of Nutritional Sciences & Toxicology, University of California Berkeley, Berkeley, CA 94720, USA
- Endocrinology Graduate Program, University of California Berkeley, Berkeley, CA 94720, USA
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3
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Fenne KT, Clauss M, Schäfer Olstad D, Johansen EI, Jensen J. An Acute Bout of Endurance Exercise Does Not Prevent the Inhibitory Effect of Caffeine on Glucose Tolerance the following Morning. Nutrients 2023; 15:nu15081941. [PMID: 37111160 PMCID: PMC10143402 DOI: 10.3390/nu15081941] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Revised: 03/29/2023] [Accepted: 04/13/2023] [Indexed: 04/29/2023] Open
Abstract
Caffeine reduces glucose tolerance, whereas exercise training improves glucose homeostasis. The aim of the present study was to investigate the effect of caffeine on glucose tolerance the morning after an acute bout of aerobic exercise. Methods: The study had a 2 × 2 factorial design. Oral glucose tolerance tests (OGTT) were performed after overnight fasting with/without caffeine and with/without exercise the evening before. Eight healthy young active males were included (Age 25.5 ± 1.5 years; 83.9 ± 9.0 kg; VO2max: 54.3 ± 7.0 mL·kg-1·min-1). The exercise session consisted of 30 min cycling at 71% of VO2max followed by four 5 min intervals at 84% with 3 min of cycling at 40% of VO2max between intervals. The exercise was performed at 17:00 h. Energy expenditure at each session was ~976 kcal. Lactate increased to ~8 mM during the exercise sessions. Participants arrived at the laboratory the following morning at 7.00 AM after an overnight fast. Resting blood samples were taken before blood pressure and heart rate variability (HRV) were measured. Caffeine (3 mg/kg bodyweight) or placebo (similar taste/flavor) was ingested, and blood samples, blood pressure and HRV were measured after 30 min. Next, the OGTTs were initiated (75 g glucose dissolved in 3 dL water) and blood was sampled. Blood pressure and HRV were measured during the OGTT. Caffeine increased the area under curve (AUC) for glucose independently of whether exercise was done the evening before (p = 0.03; Two-way ANOVA; Interaction: p = 0.835). Caffeine did not significantly increase AUC for C-peptides compared to placebo (p = 0.096), and C-peptide response was not influenced by exercise. The acute bout of exercise did not significantly improve glucose tolerance the following morning. Diastolic blood pressure during the OGTT was slightly higher after intake of caffeine, independent of whether exercise was performed the evening before or not. Neither caffeine nor exercise the evening before significantly influenced HRV. In conclusion, caffeine reduced glucose tolerance independently of whether endurance exercise was performed the evening before. The low dose of caffeine did not influence heart rate variability but increased diastolic blood pressure slightly.
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Affiliation(s)
- Karoline T Fenne
- Department of Physical Performance, Norwegian School of Sport Sciences, P.O. Box 4014, Ullevål Stadion, 0806 Oslo, Norway
| | - Matthieu Clauss
- Department of Physical Performance, Norwegian School of Sport Sciences, P.O. Box 4014, Ullevål Stadion, 0806 Oslo, Norway
| | | | - Egil I Johansen
- Department of Physical Performance, Norwegian School of Sport Sciences, P.O. Box 4014, Ullevål Stadion, 0806 Oslo, Norway
| | - Jørgen Jensen
- Department of Physical Performance, Norwegian School of Sport Sciences, P.O. Box 4014, Ullevål Stadion, 0806 Oslo, Norway
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4
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Listeria monocytogenes-How This Pathogen Uses Its Virulence Mechanisms to Infect the Hosts. Pathogens 2022; 11:pathogens11121491. [PMID: 36558825 PMCID: PMC9783847 DOI: 10.3390/pathogens11121491] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Revised: 11/23/2022] [Accepted: 12/05/2022] [Indexed: 12/13/2022] Open
Abstract
Listeriosis is a serious food-borne illness, especially in susceptible populations, including children, pregnant women, and elderlies. The disease can occur in two forms: non-invasive febrile gastroenteritis and severe invasive listeriosis with septicemia, meningoencephalitis, perinatal infections, and abortion. Expression of each symptom depends on various bacterial virulence factors, immunological status of the infected person, and the number of ingested bacteria. Internalins, mainly InlA and InlB, invasins (invasin A, LAP), and other surface adhesion proteins (InlP1, InlP4) are responsible for epithelial cell binding, whereas internalin C (InlC) and actin assembly-inducing protein (ActA) are involved in cell-to-cell bacterial spread. L. monocytogenes is able to disseminate through the blood and invade diverse host organs. In persons with impaired immunity, the elderly, and pregnant women, the pathogen can also cross the blood-brain and placental barriers, which results in the invasion of the central nervous system and fetus infection, respectively. The aim of this comprehensive review is to summarize the current knowledge on the epidemiology of listeriosis and L. monocytogenes virulence mechanisms that are involved in host infection, with a special focus on their molecular and cellular aspects. We believe that all this information is crucial for a better understanding of the pathogenesis of L. monocytogenes infection.
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5
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Nicastro R, Gaillard H, Zarzuela L, Péli-Gulli MP, Fernández-García E, Tomé M, García-Rodríguez N, Durán RV, De Virgilio C, Wellinger RE. Manganese is a physiologically relevant TORC1 activator in yeast and mammals. eLife 2022; 11:80497. [PMID: 35904415 PMCID: PMC9337852 DOI: 10.7554/elife.80497] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2022] [Accepted: 07/18/2022] [Indexed: 12/09/2022] Open
Abstract
The essential biometal manganese (Mn) serves as a cofactor for several enzymes that are crucial for the prevention of human diseases. Whether intracellular Mn levels may be sensed and modulate intracellular signaling events has so far remained largely unexplored. The highly conserved target of rapamycin complex 1 (TORC1, mTORC1 in mammals) protein kinase requires divalent metal cofactors such as magnesium (Mg2+) to phosphorylate effectors as part of a homeostatic process that coordinates cell growth and metabolism with nutrient and/or growth factor availability. Here, our genetic approaches reveal that TORC1 activity is stimulated in vivo by elevated cytoplasmic Mn levels, which can be induced by loss of the Golgi-resident Mn2+ transporter Pmr1 and which depend on the natural resistance-associated macrophage protein (NRAMP) metal ion transporters Smf1 and Smf2. Accordingly, genetic interventions that increase cytoplasmic Mn2+ levels antagonize the effects of rapamycin in triggering autophagy, mitophagy, and Rtg1-Rtg3-dependent mitochondrion-to-nucleus retrograde signaling. Surprisingly, our in vitro protein kinase assays uncovered that Mn2+ activates TORC1 substantially better than Mg2+, which is primarily due to its ability to lower the Km for ATP, thereby allowing more efficient ATP coordination in the catalytic cleft of TORC1. These findings, therefore, provide both a mechanism to explain our genetic observations in yeast and a rationale for how fluctuations in trace amounts of Mn can become physiologically relevant. Supporting this notion, TORC1 is also wired to feedback control mechanisms that impinge on Smf1 and Smf2. Finally, we also show that Mn2+-mediated control of TORC1 is evolutionarily conserved in mammals, which may prove relevant for our understanding of the role of Mn in human diseases.
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Affiliation(s)
- Raffaele Nicastro
- University of Fribourg, Department of Biology, Fribourg, Switzerland
| | - Hélène Gaillard
- Centro Andaluz de Biología Molecular y Medicina Regenerativa - CABIMER, Consejo Superior de Investigaciones Científicas, Universidad de Sevilla, Seville, Spain.,Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Seville, Spain
| | - Laura Zarzuela
- Centro Andaluz de Biología Molecular y Medicina Regenerativa - CABIMER, Consejo Superior de Investigaciones Científicas, Universidad de Sevilla, Seville, Spain
| | | | - Elisabet Fernández-García
- Centro Andaluz de Biología Molecular y Medicina Regenerativa - CABIMER, Consejo Superior de Investigaciones Científicas, Universidad de Sevilla, Seville, Spain.,Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Seville, Spain
| | - Mercedes Tomé
- Centro Andaluz de Biología Molecular y Medicina Regenerativa - CABIMER, Consejo Superior de Investigaciones Científicas, Universidad de Sevilla, Seville, Spain
| | - Néstor García-Rodríguez
- Centro Andaluz de Biología Molecular y Medicina Regenerativa - CABIMER, Consejo Superior de Investigaciones Científicas, Universidad de Sevilla, Seville, Spain.,Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Seville, Spain
| | - Raúl V Durán
- Centro Andaluz de Biología Molecular y Medicina Regenerativa - CABIMER, Consejo Superior de Investigaciones Científicas, Universidad de Sevilla, Seville, Spain
| | | | - Ralf Erik Wellinger
- Centro Andaluz de Biología Molecular y Medicina Regenerativa - CABIMER, Consejo Superior de Investigaciones Científicas, Universidad de Sevilla, Seville, Spain.,Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Seville, Spain
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6
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Rangwala AM, Mingione VR, Georghiou G, Seeliger MA. Kinases on Double Duty: A Review of UniProtKB Annotated Bifunctionality within the Kinome. Biomolecules 2022; 12:biom12050685. [PMID: 35625613 PMCID: PMC9138534 DOI: 10.3390/biom12050685] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Revised: 05/03/2022] [Accepted: 05/09/2022] [Indexed: 01/27/2023] Open
Abstract
Phosphorylation facilitates the regulation of all fundamental biological processes, which has triggered extensive research of protein kinases and their roles in human health and disease. In addition to their phosphotransferase activity, certain kinases have evolved to adopt additional catalytic functions, while others have completely lost all catalytic activity. We searched the Universal Protein Resource Knowledgebase (UniProtKB) database for bifunctional protein kinases and focused on kinases that are critical for bacterial and human cellular homeostasis. These kinases engage in diverse functional roles, ranging from environmental sensing and metabolic regulation to immune-host defense and cell cycle control. Herein, we describe their dual catalytic activities and how they contribute to disease pathogenesis.
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7
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Nadel G, Yao Z, Wainstein E, Cohen I, Ben-Ami I, Schajnovitz A, Maik-Rachline G, Naor Z, Horwitz BA, Seger R. GqPCR-stimulated dephosphorylation of AKT is induced by an IGBP1-mediated PP2A switch. Cell Commun Signal 2022; 20:5. [PMID: 34998390 PMCID: PMC8742922 DOI: 10.1186/s12964-021-00805-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Accepted: 11/18/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND G protein-coupled receptors (GPCRs) usually regulate cellular processes via activation of intracellular signaling pathways. However, we have previously shown that in several cell lines, GqPCRs induce immediate inactivation of the AKT pathway, which leads to JNK-dependent apoptosis. This apoptosis-inducing AKT inactivation is essential for physiological functions of several GqPCRs, including those for PGF2α and GnRH. METHODS Here we used kinase activity assays of PI3K and followed phosphorylation state of proteins using specific antibodies. In addition, we used coimmunoprecipitation and proximity ligation assays to follow protein-protein interactions. Apoptosis was detected by TUNEL assay and PARP1 cleavage. RESULTS We identified the mechanism that allows the unique stimulated inactivation of AKT and show that the main regulator of this process is the phosphatase PP2A, operating with the non-canonical regulatory subunit IGBP1. In resting cells, an IGBP1-PP2Ac dimer binds to PI3K, dephosphorylates the inhibitory pSer608-p85 of PI3K and thus maintains its high basal activity. Upon GqPCR activation, the PP2Ac-IGBP1 dimer detaches from PI3K and thus allows the inhibitory dephosphorylation. At this stage, the free PP2Ac together with IGBP1 and PP2Aa binds to AKT, causing its dephosphorylation and inactivation. CONCLUSION Our results show a stimulated shift of PP2Ac from PI3K to AKT termed "PP2A switch" that represses the PI3K/AKT pathway, providing a unique mechanism of GPCR-stimulated dephosphorylation. Video Abstract.
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Affiliation(s)
- Guy Nadel
- Departments of Biological Regulation, The Weizmann Institute of Science, Rehovot, Israel
| | - Zhong Yao
- Departments of Biological Regulation, The Weizmann Institute of Science, Rehovot, Israel
| | - Ehud Wainstein
- Departments of Biological Regulation, The Weizmann Institute of Science, Rehovot, Israel
| | - Izel Cohen
- Departments of Biological Regulation, The Weizmann Institute of Science, Rehovot, Israel
| | - Ido Ben-Ami
- Departments of Biological Regulation, The Weizmann Institute of Science, Rehovot, Israel.,IVF and Fertility Unit, Department of OB/GYN, Shaare Zedek Medical Center and The Hebrew University Medical School, Jerusalem, Israel
| | - Amir Schajnovitz
- Departments of Biological Regulation, The Weizmann Institute of Science, Rehovot, Israel
| | - Galia Maik-Rachline
- Departments of Biological Regulation, The Weizmann Institute of Science, Rehovot, Israel
| | - Zvi Naor
- Department of Biochemistry and Molecular Biology, Tel Aviv University, Tel Aviv, Israel
| | - Benjamin A Horwitz
- Departments of Biological Regulation, The Weizmann Institute of Science, Rehovot, Israel.,Faculty of Biology, Technion-Israel Institute of Technology, Haifa, Israel
| | - Rony Seger
- Departments of Biological Regulation, The Weizmann Institute of Science, Rehovot, Israel.
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8
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Pei J, Wang B, Wang D. Current Studies on Molecular Mechanisms of Insulin Resistance. J Diabetes Res 2022; 2022:1863429. [PMID: 36589630 PMCID: PMC9803571 DOI: 10.1155/2022/1863429] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/17/2022] [Revised: 06/06/2022] [Accepted: 12/12/2022] [Indexed: 12/24/2022] Open
Abstract
Diabetes is a metabolic disease that raises the risk of microvascular and neurological disorders. Insensitivity to insulin is a characteristic of type II diabetes, which accounts for 85-90 percent of all diabetic patients. The fundamental molecular factor of insulin resistance may be impaired cell signal transduction mediated by the insulin receptor (IR). Several cell-signaling proteins, including IR, insulin receptor substrate (IRS), and phosphatidylinositol 3-kinase (PI3K), have been recognized as being important in the impaired insulin signaling pathway since they are associated with a large number of proteins that are strictly regulated and interact with other signaling pathways. Many studies have found a correlation between IR alternative splicing, IRS gene polymorphism, the complicated regulatory function of IRS serine/threonine phosphorylation, and the negative regulatory role of p85 in insulin resistance and diabetes mellitus. This review brings up-to-date knowledge of the roles of signaling proteins in insulin resistance in order to aid in the discovery of prospective targets for insulin resistance treatment.
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Affiliation(s)
- Jinli Pei
- Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, Shandong, China
| | - Baochun Wang
- The First Department of Gastrointestinal Surgery, Hainan General Hospital, Haikou, Hainan 570228, China
| | - Dayong Wang
- Laboratory of Biopharmaceuticals and Molecular Pharmacology, School of Pharmaceutical Sciences, Hainan University, Hainan 570228, China
- State Key Laboratory of Tropical Biological Resources of the Ministry of Education of China, Hainan University, Hainan 570228, China
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9
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Class IA PI3K regulatory subunits: p110-independent roles and structures. Biochem Soc Trans 2021; 48:1397-1417. [PMID: 32677674 PMCID: PMC7458397 DOI: 10.1042/bst20190845] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Revised: 06/26/2020] [Accepted: 06/30/2020] [Indexed: 12/12/2022]
Abstract
The phosphatidylinositol 3-kinase (PI3K) pathway is a critical regulator of many cellular processes including cell survival, growth, proliferation and motility. Not surprisingly therefore, the PI3K pathway is one of the most frequently mutated pathways in human cancers. In addition to their canonical role as part of the PI3K holoenzyme, the class IA PI3K regulatory subunits undertake critical functions independent of PI3K. The PI3K regulatory subunits exist in excess over the p110 catalytic subunits and therefore free in the cell. p110-independent p85 is unstable and exists in a monomer-dimer equilibrium. Two conformations of dimeric p85 have been reported that are mediated by N-terminal and C-terminal protein domain interactions, respectively. The role of p110-independent p85 is under investigation and it has been found to perform critical adaptor functions, sequestering or influencing compartmentalisation of key signalling proteins. Free p85 has roles in glucose homeostasis, cellular stress pathways, receptor trafficking and cell migration. As a regulator of fundamental pathways, the amount of p110-independent p85 in the cell is critical. Factors that influence the monomer-dimer equilibrium of p110-independent p85 offer additional control over this system, disruption to which likely results in disease. Here we review the current knowledge of the structure and functions of p110-independent class IA PI3K regulatory subunits.
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10
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Nussinov R, Zhang M, Tsai CJ, Jang H. Phosphorylation and Driver Mutations in PI3Kα and PTEN Autoinhibition. Mol Cancer Res 2020; 19:543-548. [PMID: 33288731 DOI: 10.1158/1541-7786.mcr-20-0818] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2020] [Revised: 10/29/2020] [Accepted: 12/03/2020] [Indexed: 11/16/2022]
Abstract
PI3K and PTEN are the second and third most highly mutated proteins in cancer following only p53. Their actions oppose each other. PI3K phosphorylates signaling lipid PIP2 to PIP3 PTEN dephosphorylates it back. Driver mutations in both proteins accrue PIP3 PIP3 recruits AKT and PDK1 to the membrane, promoting cell-cycle progression. Here we review phosphorylation events and mutations in autoinhibition in PI3K and PTEN from the structural standpoint. Our purpose is to clarify how they control the autoinhibited states. In autoinhibition, a segment or a subunit of the protein occludes its functional site. Protein-protein interfaces are often only marginally stable, making them sensitive to changes in conditions in living cells. Phosphorylation can stabilize or destabilize the interfaces. Driver mutations commonly destabilize them. In analogy to "passenger mutations," we coin "passenger phosphorylation" to emphasize that the presence of a phosphorylation recognition sequence logo does not necessarily imply function. Rather, it may simply reflect a statistical occurrence. In both PI3K and PTEN, autoinhibiting phosphorylation events are observed in the occluding "piece." In PI3Kα, the "piece" is the p85α subunit. In PTEN, it is the C-terminal segment. In both enzymes the stabilized interface covers the domain that attaches to the membrane. Driver mutations that trigger rotation of the occluding piece or its deletion prompt activation. To date, both enzymes lack specific, potent drugs. We discuss the implications of detailed structural and mechanistic insight into oncogenic activation and how it can advance allosteric precision oncology.
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Affiliation(s)
- Ruth Nussinov
- Computational Structural Biology Section, Frederick National Laboratory for Cancer Research in the Laboratory of Cancer Immunometabolism, NCI, Frederick, Maryland. .,Department of Human Molecular Genetics and Biochemistry, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Mingzhen Zhang
- Computational Structural Biology Section, Frederick National Laboratory for Cancer Research in the Laboratory of Cancer Immunometabolism, NCI, Frederick, Maryland
| | - Chung-Jung Tsai
- Computational Structural Biology Section, Frederick National Laboratory for Cancer Research in the Laboratory of Cancer Immunometabolism, NCI, Frederick, Maryland
| | - Hyunbum Jang
- Computational Structural Biology Section, Frederick National Laboratory for Cancer Research in the Laboratory of Cancer Immunometabolism, NCI, Frederick, Maryland
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11
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Sharma J, Bhardwaj V, Purohit R. Structural Perturbations due to Mutation (H1047R) in Phosphoinositide-3-kinase (PI3Kα) and Its Involvement in Oncogenesis: An in Silico Insight. ACS OMEGA 2019; 4:15815-15823. [PMID: 31592171 PMCID: PMC6776984 DOI: 10.1021/acsomega.9b01439] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2019] [Accepted: 07/23/2019] [Indexed: 05/03/2023]
Abstract
PI3Kα is a heterodimer protein consisting of two subunits (p110α and p85α) which promotes various signaling pathways. Oncogenic mutation in the catalytic subunit p110α of PI3Kα at the 1047 position in the kinase domain substitutes the histidine with arginine. This mutation brings about conformational transitions in the protein complex. These transitions expose the membrane binding region of PI3Kα, and then it independently binds to the cell membrane through its kinase domain without the involvement of the membrane-bound protein RAS. We observed notable changes between the protein complexes (p110α-p85α) of native and mutant structures at the atomic level using molecular dynamics simulations. Simulation results revealed formation of a less number of hydrogen bonds between the two subunits in the mutant protein complex which led the two subunits to move away from each other. This increase in distance between the subunits led to an expanded structure, thereby increasing the flexibility of the protein complex. Furthermore, a study of secondary structure elements and the electrostatic potential of the protein also gave a molecular insight into the change in interaction patterns of the protein with the plasma membrane. Our finding clearly indicates the role of mutation in oncogenesis and provides an insight into considering the structural aspects to handle this mutation.
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Affiliation(s)
- Jatin Sharma
- Structural Bioinformatics
Lab, CSIR-Institute of Himalayan Bioresource
Technology (CSIR-IHBT), Palampur, Himachal Pradesh 176061, India
- Biotechnology Division, CSIR-IHBT, Palampur, Himachal Pradesh 176061, India
| | - Vijay Bhardwaj
- Structural Bioinformatics
Lab, CSIR-Institute of Himalayan Bioresource
Technology (CSIR-IHBT), Palampur, Himachal Pradesh 176061, India
- Biotechnology Division, CSIR-IHBT, Palampur, Himachal Pradesh 176061, India
| | - Rituraj Purohit
- Structural Bioinformatics
Lab, CSIR-Institute of Himalayan Bioresource
Technology (CSIR-IHBT), Palampur, Himachal Pradesh 176061, India
- Biotechnology Division, CSIR-IHBT, Palampur, Himachal Pradesh 176061, India
- Academy of Scientific & Innovative Research (AcSIR), CSIR-IHBT Campus, Palampur, Himachal Pradesh 176061, India
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12
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Citrate-Induced p85α⁻PTEN Complex Formation Causes G 2/M Phase Arrest in Human Pharyngeal Squamous Carcinoma Cell Lines. Int J Mol Sci 2019; 20:ijms20092105. [PMID: 31035650 PMCID: PMC6539620 DOI: 10.3390/ijms20092105] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2019] [Revised: 04/20/2019] [Accepted: 04/24/2019] [Indexed: 01/11/2023] Open
Abstract
Citrate is a key intermediate of the tricarboxylic acid cycle and acts as an allosteric signal to regulate the production of cellular ATP. An elevated cytosolic citrate concentration inhibits growth in several types of human cancer cells; however, the underlying mechanism by which citrate induces the growth arrest of cancer cells remains unclear. The results of this study showed that treatment of human pharyngeal squamous carcinoma (PSC) cells with a growth-suppressive concentration of citrate caused cell cycle arrest at the G2/M phase. A coimmunoprecipitation study demonstrated that citrate-induced cell cycle arrest in the G2/M phase was associated with stabilizing the formation of cyclin B1-phospho (p)-cyclin-dependent kinase 1 (CDK1) (Thr 161) complexes. The citrate-induced increased levels of cyclin B1 and G2/M phase arrest were suppressed by the caspase-3 inhibitor Ac-DEVD-CMK and caspase-3 cleavage of mutant p21 (D112N). Ectopic expression of the constitutively active form of protein kinase B (Akt1) could overcome the induction of p21 cleavage, cyclin B1-p-CDK1 (Thr 161) complexes, and G2/M phase arrest by citrate. p85α-phosphatase and tensin homolog deleted from chromosome 10 (PTEN) complex-mediated inactivation of Akt was required for citrate-induced G2/M phase cell cycle arrest because PTEN short hairpin RNA or a PTEN inhibitor (SF1670) blocked the suppression of Akt Ser 473 phosphorylation and the induction of cyclin B1-p-CDK1 (Thr 161) complexes and G2/M phase arrest by citrate. In conclusion, citrate induces G2/M phase arrest in PSC cells by inducing the formation of p85α-PTEN complexes to attenuate Akt-mediated signaling, thereby causing the formation of cyclin B1-p-CDK1 (Thr 161) complexes.
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Vallejo-Díaz J, Chagoyen M, Olazabal-Morán M, González-García A, Carrera AC. The Opposing Roles of PIK3R1/p85α and PIK3R2/p85β in Cancer. Trends Cancer 2019; 5:233-244. [PMID: 30961830 DOI: 10.1016/j.trecan.2019.02.009] [Citation(s) in RCA: 69] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2018] [Revised: 02/11/2019] [Accepted: 02/15/2019] [Indexed: 01/04/2023]
Abstract
Dysregulation of the PI3K/PTEN pathway is a frequent event in cancer, and PIK3CA and PTEN are the most commonly mutated genes after TP53. PIK3R1 is the predominant regulatory isoform of PI3K. PIK3R2 is an ubiquitous isoform that has been so far overlooked, but data from The Cancer Genome Atlas shows that increased expression of PIK3R2 is also frequent in cancer. In contrast to PIK3R1, which is a tumor-suppressor gene, PIK3R2 is an oncogene. We review here the opposing roles of PIK3R1 and PIK3R2 in cancer, the regulatory mechanisms that control PIK3R2 expression, and emerging therapeutic approaches targeting PIK3R2.
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Affiliation(s)
- Jesús Vallejo-Díaz
- Department of Immunology and Oncology, Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas (CSIC), Universidad Autónoma de Madrid, Cantoblanco, Madrid E-28049, Spain
| | - Monica Chagoyen
- Department of Systems Biology, Centro Nacional de Biotecnología, CSIC, Universidad Autónoma de Madrid, Cantoblanco, Madrid E-28049, Spain
| | - Manuel Olazabal-Morán
- Department of Immunology and Oncology, Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas (CSIC), Universidad Autónoma de Madrid, Cantoblanco, Madrid E-28049, Spain
| | - Ana González-García
- Department of Immunology and Oncology, Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas (CSIC), Universidad Autónoma de Madrid, Cantoblanco, Madrid E-28049, Spain
| | - Ana Clara Carrera
- Department of Immunology and Oncology, Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas (CSIC), Universidad Autónoma de Madrid, Cantoblanco, Madrid E-28049, Spain.
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Maheshwari S, Miller MS, O'Meally R, Cole RN, Amzel LM, Gabelli SB. Kinetic and structural analyses reveal residues in phosphoinositide 3-kinase α that are critical for catalysis and substrate recognition. J Biol Chem 2017; 292:13541-13550. [PMID: 28676499 DOI: 10.1074/jbc.m116.772426] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Revised: 06/30/2017] [Indexed: 12/26/2022] Open
Abstract
Phosphoinositide 3-kinases (PI3Ks) are ubiquitous lipid kinases that activate signaling cascades controlling cell survival, proliferation, protein synthesis, and vesicle trafficking. PI3Ks have dual kinase specificity: a lipid kinase activity that phosphorylates the 3'-hydroxyl of phosphoinositides and a protein-kinase activity that includes autophosphorylation. Despite the wealth of biochemical and structural information on PI3Kα, little is known about the identity and roles of individual active-site residues in catalysis. To close this gap, we explored the roles of residues of the catalytic domain and the regulatory subunit of human PI3Kα in lipid and protein phosphorylation. Using site-directed mutagenesis, kinetic assays, and quantitative mass spectrometry, we precisely mapped key residues involved in substrate recognition and catalysis by PI3Kα. Our results revealed that Lys-776, located in the P-loop of PI3Kα, is essential for the recognition of lipid and ATP substrates and also plays an important role in PI3Kα autophosphorylation. Replacement of the residues His-936 and His-917 in the activation and catalytic loops, respectively, with alanine dramatically changed PI3Kα kinetics. Although H936A inactivated the lipid kinase activity without affecting autophosphorylation, H917A abolished both the lipid and protein kinase activities of PI3Kα. On the basis of these kinetic and structural analyses, we propose possible mechanistic roles of these critical residues in PI3Kα catalysis.
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Affiliation(s)
- Sweta Maheshwari
- From the Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Michelle S Miller
- Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21287
| | - Robert O'Meally
- Mass Spectrometry and Proteomics Facility, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, and
| | - Robert N Cole
- Mass Spectrometry and Proteomics Facility, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, and
| | - L Mario Amzel
- From the Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205,
| | - Sandra B Gabelli
- From the Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, .,Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21287.,Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
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15
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Watson LJ, Alexander KM, Mohan ML, Bowman AL, Mangmool S, Xiao K, Naga Prasad SV, Rockman HA. Phosphorylation of Src by phosphoinositide 3-kinase regulates beta-adrenergic receptor-mediated EGFR transactivation. Cell Signal 2016; 28:1580-92. [PMID: 27169346 DOI: 10.1016/j.cellsig.2016.05.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Revised: 05/03/2016] [Accepted: 05/05/2016] [Indexed: 01/08/2023]
Abstract
β2-Adrenergic receptors (β2AR) transactivate epidermal growth factor receptors (EGFR) through formation of a β2AR-EGFR complex that requires activation of Src to mediate signaling. Here, we show that both lipid and protein kinase activities of the bifunctional phosphoinositide 3-kinase (PI3K) enzyme are required for β2AR-stimulated EGFR transactivation. Mechanistically, the generation of phosphatidylinositol (3,4,5)-tris-phosphate (PIP3) by the lipid kinase function stabilizes β2AR-EGFR complexes while the protein kinase activity of PI3K regulates Src activation by direct phosphorylation. The protein kinase activity of PI3K phosphorylates serine residue 70 on Src to enhance its activity and induce EGFR transactivation following βAR stimulation. This newly identified function for PI3K, whereby Src is a substrate for the protein kinase activity of PI3K, is of importance since Src plays a key role in pathological and physiological signaling.
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Affiliation(s)
- Lewis J Watson
- Department of Medicine, Duke University Medical Center, Durham, NC 27710, United States
| | - Kevin M Alexander
- Department of Medicine, Duke University Medical Center, Durham, NC 27710, United States
| | - Maradumane L Mohan
- Department of Molecular Cardiology, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH 44195, United States
| | - Amber L Bowman
- Department of Medicine, Duke University Medical Center, Durham, NC 27710, United States
| | - Supachoke Mangmool
- Department of Pharmacology, Faculty of Pharmacy, Mahidol University, Thailand
| | - Kunhong Xiao
- Department of Medicine, Duke University Medical Center, Durham, NC 27710, United States; Department of Pharmacology and Chemical Biology, University of Pittsburg School of Medicine, Pittsburgh, PA 15261, United States
| | - Sathyamangla V Naga Prasad
- Department of Molecular Cardiology, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH 44195, United States.
| | - Howard A Rockman
- Department of Medicine, Duke University Medical Center, Durham, NC 27710, United States; Department of Cell Biology, Duke University Medical Center, Durham, NC 27710, United States; Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, United States.
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16
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Asati V, Mahapatra DK, Bharti SK. PI3K/Akt/mTOR and Ras/Raf/MEK/ERK signaling pathways inhibitors as anticancer agents: Structural and pharmacological perspectives. Eur J Med Chem 2016; 109:314-41. [PMID: 26807863 DOI: 10.1016/j.ejmech.2016.01.012] [Citation(s) in RCA: 383] [Impact Index Per Article: 47.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Revised: 01/08/2016] [Accepted: 01/09/2016] [Indexed: 12/17/2022]
Abstract
The protein kinases regulate cellular functions such as transcription, translation, proliferation, growth and survival by the process of phosphorylation. Over activation of signaling pathways play a major role in oncogenesis. The PI3K signaling pathway is dysregulated almost in all cancers due to the amplification, genetic mutation of PI3K gene and the components of the PI3K pathway themselves. Stimulation of the PI3K/Akt/mTOR and Ras/Raf/MEK/ERK pathways enhances growth, survival, and metabolism of cancer cells. Recently, the PI3K/Akt/mTOR and Ras/Raf/MEK/ERK signaling pathways have been identified as promising therapeutic targets for cancer therapy. The kinase inhibitors with enhanced specificity and improved pharmacokinetics have been considered for design and development of anticancer agents. This review focuses primarily on the Ras/Raf/MEK/ERK and PI3K/Akt/mTOR signaling pathways as therapeutic targets of anticancer drugs, their specific and dual inhibitors, structure activity relationships (SARs) and inhibitors under clinical trials.
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Affiliation(s)
- Vivek Asati
- Institute of Pharmaceutical Sciences, Guru Ghasidas Vishwavidyalaya (A Central University), Bilaspur 495009, Chhattisgarh, India
| | - Debarshi Kar Mahapatra
- Institute of Pharmaceutical Sciences, Guru Ghasidas Vishwavidyalaya (A Central University), Bilaspur 495009, Chhattisgarh, India
| | - Sanjay Kumar Bharti
- Institute of Pharmaceutical Sciences, Guru Ghasidas Vishwavidyalaya (A Central University), Bilaspur 495009, Chhattisgarh, India.
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Ogi H, Goto GH, Ghosh A, Zencir S, Henry E, Sugimoto K. Requirement of the FATC domain of protein kinase Tel1 for localization to DNA ends and target protein recognition. Mol Biol Cell 2015; 26:3480-8. [PMID: 26246601 PMCID: PMC4591692 DOI: 10.1091/mbc.e15-05-0259] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2015] [Accepted: 07/29/2015] [Indexed: 02/04/2023] Open
Abstract
Two large phosphatidylinositol 3-kinase-related protein kinases (PIKKs), ATM and ATR, play a central role in the DNA damage response pathway. PIKKs contain a highly conserved extreme C-terminus called the FRAP-ATM-TRRAP-C-terminal (FATC) domain. In budding yeast, ATM and ATR correspond to Tel1 and Mec1, respectively. In this study, we characterized functions of the FATC domain of Tel1 by introducing substitution or truncation mutations. One substitution mutation, termed tel1-21, and a truncation mutation, called tel1-ΔC, did not significantly affect the expression level. The tel1-21 mutation impaired the cellular response to DNA damage and conferred moderate telomere maintenance defect. In contrast, the tel1-ΔC mutation behaved like a null mutation, conferring defects in both DNA damage response and telomere maintenance. Tel1-21 protein localized to DNA ends as effectively as wild-type Tel1 protein, whereas Tel1-ΔC protein failed. Introduction of a hyperactive TEL1-hy mutation suppressed the tel1-21 mutation but not the tel1-ΔC mutation. In vitro analyses revealed that both Tel1-21 and Tel1-ΔC proteins undergo efficient autophosphorylation but exhibit decreased kinase activities toward the exogenous substrate protein, Rad53. Our results show that the FATC domain of Tel1 mediates localization to DNA ends and contributes to phosphorylation of target proteins.
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Affiliation(s)
- Hiroo Ogi
- Department of Microbiology, Biochemistry and Molecular Genetics, International Center for Public Health, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ 07103
| | - Greicy H Goto
- Department of Microbiology, Biochemistry and Molecular Genetics, International Center for Public Health, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ 07103
| | - Avik Ghosh
- Department of Microbiology, Biochemistry and Molecular Genetics, International Center for Public Health, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ 07103
| | - Sevil Zencir
- Department of Microbiology, Biochemistry and Molecular Genetics, International Center for Public Health, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ 07103
| | - Everett Henry
- Department of Microbiology, Biochemistry and Molecular Genetics, International Center for Public Health, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ 07103
| | - Katsunori Sugimoto
- Department of Microbiology, Biochemistry and Molecular Genetics, International Center for Public Health, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ 07103 )
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18
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Kang H, Kiess A, Chung CH. Emerging biomarkers in head and neck cancer in the era of genomics. Nat Rev Clin Oncol 2014; 12:11-26. [PMID: 25403939 DOI: 10.1038/nrclinonc.2014.192] [Citation(s) in RCA: 201] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Head and neck cancer (HNC) broadly includes carcinomas arising from the mucosal epithelia of the head and neck region as well as various cell types of salivary glands and the thyroid. As reflected by the multiple sites and histologies of HNC, the molecular characteristics and clinical outcomes of this disease vary widely. In this Review, we focus on established and emerging biomarkers that are most relevant to nasopharyngeal carcinoma and head and neck squamous-cell carcinoma (HNSCC), which includes primary sites in the oral cavity, oropharynx, hypopharynx and larynx. Applications and limitations of currently established biomarkers are discussed along with examples of successful biomarker development. For emerging biomarkers, preclinical or retrospective data are also described in the context of recently completed comprehensive molecular analyses of HNSCC, which provide a broad genetic landscape and molecular classification beyond histology and clinical characteristics. We will highlight the ongoing effort that will see a shift from prognostic to predictive biomarker development in HNC with the goal of delivering individualized cancer therapy.
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Affiliation(s)
- Hyunseok Kang
- Department of Oncology, Johns Hopkins University School of Medicine, Johns Hopkins Medical Institutions, 1650 Orleans Street, CRB-1 Room 344, Baltimore, MD 21287-0013, USA
| | - Ana Kiess
- Department of Radiation Oncology, Johns Hopkins University School of Medicine, Johns Hopkins Medical Institutions, 1650 Orleans Street, CRB-1 Room 344, Baltimore, MD 21287-0013, USA
| | - Christine H Chung
- 1] Department of Oncology, Johns Hopkins University School of Medicine, Johns Hopkins Medical Institutions, 1650 Orleans Street, CRB-1 Room 344, Baltimore, MD 21287-0013, USA. [2] Department of Otolaryngology-Head and Neck Surgery, Johns Hopkins University School of Medicine, Johns Hopkins Medical Institutions, 1650 Orleans Street, CRB-1 Room 344, Baltimore, MD 21287-0013, USA
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Cell activation-induced phosphoinositide 3-kinase alpha/beta dimerization regulates PTEN activity. Mol Cell Biol 2014; 34:3359-73. [PMID: 24958106 DOI: 10.1128/mcb.00167-14] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The phosphoinositide 3-kinase (PI3K)/PTEN (phosphatase and tensin homolog) pathway is one of the central routes that enhances cell survival, division, and migration, and it is frequently deregulated in cancer. PI3K catalyzes formation of phosphatidylinositol 3,4,5-triphosphate [PI(3,4,5)P3] after cell activation; PTEN subsequently reduces these lipids to basal levels. Activation of the ubiquitous p110α isoform precedes that of p110β at several points during the cell cycle. We studied the potential connections between p110α and p110β activation, and we show that cell stimulation promotes p110α and p110β association, demonstrating oligomerization of PI3K catalytic subunits within cells. Cell stimulation also promoted PTEN incorporation into this complex, which was necessary for PTEN activation. Our results show that PI3Ks dimerize in vivo and that PI3K and PTEN activities modulate each other in a complex that controls cell PI(3,4,5)P3 levels.
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20
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Laurent PA, Severin S, Gratacap MP, Payrastre B. Class I PI 3-kinases signaling in platelet activation and thrombosis: PDK1/Akt/GSK3 axis and impact of PTEN and SHIP1. Adv Biol Regul 2014; 54:162-174. [PMID: 24095650 DOI: 10.1016/j.jbior.2013.09.006] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Revised: 09/05/2013] [Accepted: 09/06/2013] [Indexed: 06/02/2023]
Abstract
Class I phosphoinositide 3-kinases (PI3K) have been extensively studied in different models these last years and several isoforms are now promising drug targets to treat cancer and immune diseases. Blood platelets are non-nucleated cells critical for hemostasis and strongly involved in arterial thrombosis, a leading cause of death worldwide. Besides their role in hemostasis and thrombosis, platelets provide an interesting model to characterize the implication of the different isoforms of PI3K in signaling. They are specialized for regulated adhesion, particularly under high shear stress conditions found in arteries and use highly regulated signaling mechanisms to form and stabilize a thrombus. In this review we will highlight the role of class I PI3K in these processes and the pertinence of targeting them in the context of antithrombotic strategies but also the potential consequences on the bleeding risk of inhibiting the PI3K signaling in cancer therapy. The implication of upstream regulators of the most important isoforms of PI3K in platelets and their downstream effectors such as protein kinase B (PKB or Akt) and its target glycogen synthase kinase 3 (GSK3) will be discussed as well as the impact of PTEN and SHIP phosphatases as modulators of this pathway.
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Affiliation(s)
| | - Sonia Severin
- Inserm U1048, I2MC and Université Paul Sabatier, 31024 Toulouse Cedex 03, France
| | | | - Bernard Payrastre
- Inserm U1048, I2MC and Université Paul Sabatier, 31024 Toulouse Cedex 03, France; CHU de Toulouse, Laboratoire d'Hématologie, 31059 Toulouse Cedex 03, France.
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21
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PKD1 mediates negative feedback of PI3K/Akt activation in response to G protein-coupled receptors. PLoS One 2013; 8:e73149. [PMID: 24039875 PMCID: PMC3767810 DOI: 10.1371/journal.pone.0073149] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2013] [Accepted: 07/22/2013] [Indexed: 12/15/2022] Open
Abstract
We examined whether protein kinase D1 (PKD1) mediates negative feeback of PI3K/Akt signaling in intestinal epithelial cells stimulated with G protein-coupled receptor (GPCR) agonists. Exposure of intestinal epithelial IEC-18 cells to increasing concentrations of the PKD family inhibitor kb NB 14270, at concentrations that inhibited PKD1 activation, strikingly potentiated Akt phosphorylation at Thr308 and Ser473 in response to the mitogenic GPCR agonist angiotensin II (ANG II). Enhancement of Akt activation by kb NB 142-70 was also evident in cells with other GPCR agonists, including vasopressin and lysophosphatidic acid. Cell treatment rovincial Hospital Affiliated to Shandong University, Jinan, China with the structurally unrelated PKD family inhibitor CRT0066101 increased Akt phosphorylation as potently as kb NB 142–70. Knockdown of PKD1 with two different siRNAs strikingly enhanced Akt phosphorylation in response to ANG II stimulation in IEC-18 cells. To determine whether treatment with kb NB 142–70 enhances accumulation of phosphatidylinositol (3,4,5)-trisphosphate (PIP3) in the plasma membrane, we monitored the redistribution of Akt-pleckstrin homology domain-green fluorescent protein (Akt-PH-GFP) in single IEC-18 cells. Exposure to kb NB 142–70 strikingly increased membrane accumulation of Akt-PH-GFP in response to ANG II. The translocation of the PIP3 sensor to the plasma membrane and the phosphorylation of Akt was completed prevented by prior exposure to the class I p110α specific inhibitor A66. ANG II markedly increased the phosphorylation of p85α detected by a PKD motif-specific antibody and enhanced the association of p85α with PTEN. Transgenic mice overexpressing PKD1 showed a reduced phosphorylation of Akt at Ser473 in intestinal epithelial cells compared to wild type littermates. Collectively these results indicate that PKD1 activation mediates feedback inhibition of PI3K/Akt signaling in intestinal epithelial cells in vitro and in vivo.
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Buchanan CM, Dickson JMJ, Lee WJ, Guthridge MA, Kendall JD, Shepherd PR. Oncogenic mutations of p110α isoform of PI 3-kinase upregulate its protein kinase activity. PLoS One 2013; 8:e71337. [PMID: 23936502 PMCID: PMC3731339 DOI: 10.1371/journal.pone.0071337] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2013] [Accepted: 07/03/2013] [Indexed: 12/31/2022] Open
Abstract
In addition to lipid kinase activity, the class-I PI 3-kinases also function as protein kinases targeting regulatory autophosphorylation sites and exogenous substrates. The latter include a recently identified regulatory phosphorylation of the GM-CSF/IL-3 βc receptor contributing to survival of acute myeloid leukaemia cells. Previous studies suggested differences in the protein kinase activity of the 4 isoforms of class-I PI 3-kinase so we compared the ability of all class-I PI 3-kinases and 2 common oncogenic mutants to autophosphorylate, and to phosphorylate an intracellular fragment of the GM-CSF/IL-3 βc receptor (βic). We find p110α, p110β and p110γ all phosphorylate βic but p110δ is much less effective. The two most common oncogenic mutants of p110α, H1047R and E545K have stronger protein kinase activity than wildtype p110α, both in terms of autophosphorylation and towards βic. Importantly, the lipid kinase activity of the oncogenic mutants is still inhibited by autophosphorylation to a similar extent as wildtype p110α. Previous evidence indicates the protein kinase activity of p110α is Mn(2+) dependent, casting doubt over its role in vivo. However, we show that the oncogenic mutants of p110α plus p110β and p110γ all display significant activity in the presence of Mg(2+). Furthermore we demonstrate that some small molecule inhibitors of p110α lipid kinase activity (PIK-75 and A66) are equally effective against the protein kinase activity, but other inhibitors (e.g. wortmannin and TGX221) show different patterns of inhibition against the lipid and protein kinases activities. These findings have implications for the function of PI 3-kinase, especially in tumours carrying p110α mutations.
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Affiliation(s)
- Christina M. Buchanan
- Department of Molecular Medicine, University of Auckland, Auckland, New Zealand
- Maurice Wilkins Centre for Molecular Biodiscovery, University of Auckland, Auckland, New Zealand
| | - James M. J. Dickson
- Maurice Wilkins Centre for Molecular Biodiscovery, University of Auckland, Auckland, New Zealand
- School of Biological Sciences, University of Auckland, Auckland, New Zealand
| | - Woo-Jeong Lee
- Department of Molecular Medicine, University of Auckland, Auckland, New Zealand
| | - Mark A. Guthridge
- Australian Centre for Blood Diseases, Monash University, Melbourne, Victoria, Australia
| | - Jackie D. Kendall
- Maurice Wilkins Centre for Molecular Biodiscovery, University of Auckland, Auckland, New Zealand
- Auckland Cancer Society Research Centre, University of Auckland, Auckland, New Zealand
| | - Peter R. Shepherd
- Department of Molecular Medicine, University of Auckland, Auckland, New Zealand
- Maurice Wilkins Centre for Molecular Biodiscovery, University of Auckland, Auckland, New Zealand
- * E-mail:
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Thomas D, Powell JA, Green BD, Barry EF, Ma Y, Woodcock J, Fitter S, Zannettino ACW, Pitson SM, Hughes TP, Lopez AF, Shepherd PR, Wei AH, Ekert PG, Guthridge MA. Protein kinase activity of phosphoinositide 3-kinase regulates cytokine-dependent cell survival. PLoS Biol 2013; 11:e1001515. [PMID: 23526884 PMCID: PMC3601961 DOI: 10.1371/journal.pbio.1001515] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2012] [Accepted: 02/07/2013] [Indexed: 12/20/2022] Open
Abstract
The protein kinase activity of PI3K phosphorylates specific serine residues in growth factor receptors to promote cell survival; these events are constitutively activated in some leukemias. The dual specificity protein/lipid kinase, phosphoinositide 3-kinase (PI3K), promotes growth factor-mediated cell survival and is frequently deregulated in cancer. However, in contrast to canonical lipid-kinase functions, the role of PI3K protein kinase activity in regulating cell survival is unknown. We have employed a novel approach to purify and pharmacologically profile protein kinases from primary human acute myeloid leukemia (AML) cells that phosphorylate serine residues in the cytoplasmic portion of cytokine receptors to promote hemopoietic cell survival. We have isolated a kinase activity that is able to directly phosphorylate Ser585 in the cytoplasmic domain of the interleukin 3 (IL-3) and granulocyte macrophage colony stimulating factor (GM-CSF) receptors and shown it to be PI3K. Physiological concentrations of cytokine in the picomolar range were sufficient for activating the protein kinase activity of PI3K leading to Ser585 phosphorylation and hemopoietic cell survival but did not activate PI3K lipid kinase signaling or promote proliferation. Blockade of PI3K lipid signaling by expression of the pleckstrin homology of Akt1 had no significant impact on the ability of picomolar concentrations of cytokine to promote hemopoietic cell survival. Furthermore, inducible expression of a mutant form of PI3K that is defective in lipid kinase activity but retains protein kinase activity was able to promote Ser585 phosphorylation and hemopoietic cell survival in the absence of cytokine. Blockade of p110α by RNA interference or multiple independent PI3K inhibitors not only blocked Ser585 phosphorylation in cytokine-dependent cells and primary human AML blasts, but also resulted in a block in survival signaling and cell death. Our findings demonstrate a new role for the protein kinase activity of PI3K in phosphorylating the cytoplasmic tail of the GM-CSF and IL-3 receptors to selectively regulate cell survival highlighting the importance of targeting such pathways in cancer. The ability of cells to survive in the absence of proliferation (cell division), differentiation (cell maturation) or activation allows tissues to maintain cell populations that are poised for rapid responses to damage, infections, or other physiological demands. While this “survival-only” response is fundamental to all physiological processes, the underlying mechanisms are not understood. Many growth factors are potent regulators of cell survival through their ability to bind specific cell surface receptors, which in turn activate specialized enzymes called kinases. Phosphoinositide 3-kinase (PI3K) is a dual specificity kinase that is known to be involved in cell survival and malignant transformation, and it is able to phosphorylate both lipid and protein substrates. While the PI3K lipid kinase activity has been extensively studied, the functional significance of its protein kinase activity remains unclear. Here we show that PI3K protein kinase activity can directly phosphorylate growth factor receptors on human hematopoietic (blood) cells to promote a “survival-only” response. We further show that the protein kinase activity of PI3K can be hijacked to result in uncontrolled growth factor receptor phosphorylation and the deregulated survival of leukemic cells. Our studies provide the first evidence that the protein kinase activity of PI3K can control cell survival and that this activity may be deregulated in cancer.
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Affiliation(s)
- Daniel Thomas
- Cell Growth and Differentiation Laboratory, Division of Human Immunology, Centre for Cancer Biology, SA Pathology, Adelaide, Australia
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Layton MJ, Saad M, Church NL, Pearson RB, Mitchell CA, Phillips WA. Autophosphorylation of serine 608 in the p85 regulatory subunit of wild type or cancer-associated mutants of phosphoinositide 3-kinase does not affect its lipid kinase activity. BMC BIOCHEMISTRY 2012; 13:30. [PMID: 23270540 PMCID: PMC3546864 DOI: 10.1186/1471-2091-13-30] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/28/2012] [Accepted: 12/22/2012] [Indexed: 02/08/2023]
Abstract
Background The α-isoform of the Type 1A Phosphoinositide 3-kinases (PI3Kα) has protein kinase activity as well as phosphoinositide lipid kinase activity. The best described substrate for its protein kinase activity is its regulatory subunit, p85α, which becomes phosphorylated on Serine 608. Phosphorylation of Serine 608 has been reported to down-regulate its lipid kinase activity. Results We have assessed whether oncogenic mutants of PI3Kα, which have up-regulated lipid kinase activity, have altered levels of Serine 608 phosphorylation compared to wild type PI3Kα, and whether differential phosphorylation of Serine 608 contributes to increased activity of oncogenic forms of PI3Kα with point mutations in the helical or the kinase domains. Despite markedly increased lipid kinase activity, protein kinase activity was not altered in oncogenic compared to wild type forms of PI3Kα. By manipulating levels of phosphorylation of Serine 608 in vitro, we found no evidence that the protein kinase activity of PI3Kα affects its phosphoinositide lipid kinase activity in either wild-type or oncogenic mutants of PI3Kα. Conclusions Phosphorylation of p85α S608 is not a significant regulator of wild-type or oncogenic PI3Kα lipid kinase activity.
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Affiliation(s)
- Meredith J Layton
- The Department of Biochemistry and Molecular Biology, Monash University, Clayton, VIC 3800, Australia
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Vadas O, Burke JE, Zhang X, Berndt A, Williams RL. Structural basis for activation and inhibition of class I phosphoinositide 3-kinases. Sci Signal 2011; 4:re2. [PMID: 22009150 DOI: 10.1126/scisignal.2002165] [Citation(s) in RCA: 212] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Phosphoinositide 3-kinases (PI3Ks) are implicated in a broad spectrum of cellular activities, such as growth, proliferation, differentiation, migration, and metabolism. Activation of class I PI3Ks by mutation or overexpression correlates with the development and maintenance of various human cancers. These PI3Ks are heterodimers, and the activity of the catalytic subunits is tightly controlled by the associated regulatory subunits. Although the same p85 regulatory subunits associate with all class IA PI3Ks, the functional outcome depends on the isotype of the catalytic subunit. New PI3K partners that affect the signaling by the PI3K heterodimers have been uncovered, including phosphate and tensin homolog (PTEN), cyclic adenosine monophosphate-dependent protein kinase (PKA), and nonstructural protein 1. Interactions with PI3K regulators modulate the intrinsic membrane affinity and either the rate of phosphoryl transfer or product release. Crystal structures for the class I and class III PI3Ks in complexes with associated regulators and inhibitors have contributed to developing isoform-specific inhibitors and have shed light on the numerous regulatory mechanisms controlling PI3K activation and inhibition.
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Affiliation(s)
- Oscar Vadas
- Laboratory of Molecular Biology, Medical Research Council, Hills Road, Cambridge CB20QH, UK.
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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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Vogt PK, Hart JR, Gymnopoulos M, Jiang H, Kang S, Bader AG, Zhao L, Denley A. Phosphatidylinositol 3-kinase: the oncoprotein. Curr Top Microbiol Immunol 2011; 347:79-104. [PMID: 20582532 DOI: 10.1007/82_2010_80] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The catalytic and regulatory subunits of class I phosphoinositide 3-kinase (PI3K) have oncogenic potential. The catalytic subunit p110α and the regulatory subunit p85 undergo cancer-specific gain-of-function mutations that lead to enhanced enzymatic activity, ability to signal constitutively, and oncogenicity. The β, γ, and δ isoforms of p110 are cell-transforming as overexpressed wild-type proteins. Class I PI3Ks have the unique ability to generate phosphoinositide 3,4,5 trisphosphate (PIP(3)). Class II and class III PI3Ks lack this ability. Genetic and cell biological evidence suggests that PIP(3) is essential for PI3K-mediated oncogenicity, explaining why class II and class III enzymes have not been linked to cancer. Mutational analysis reveals the existence of at least two distinct molecular mechanisms for the gain of function seen with cancer-specific mutations in p110α; one causing independence from upstream receptor tyrosine kinases, the other inducing independence from Ras. An essential component of the oncogenic signal that is initiated by PI3K is the TOR (target of rapamycin) kinase. TOR is an integrator of growth and of metabolic inputs. In complex with the raptor protein (TORC1), it controls cap-dependent translation, and this function is essential for PI3K-initiated oncogenesis.
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Affiliation(s)
- Peter K Vogt
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA.
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Hofmann BT, Hoxha E, Mohr E, Schulz K, Jücker M. Posttranscriptional regulation of the p85α adapter subunit of phosphatidylinositol 3-kinase in human leukemia cells. Leuk Lymphoma 2010; 52:467-77. [PMID: 21077741 DOI: 10.3109/10428194.2010.530360] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Constitutive activation of phosphatidylinositol 3-kinase (PI3K)/Akt signaling has been observed in up to 70% of acute myeloid leukemia. Class I(A) PI3K consists of a catalytic subunit (p110α, p110β, p110δ) and an adapter subunit (p85α, p55α, p50α, p85β, p55γ). The p85α adapter subunit stabilizes the catalytic p110 subunit and recruits p110 to the plasma membrane. In addition, p85α inhibits the basal activity of p110α and can negatively regulate signal transduction, as shown for insulin and GM-CSF receptor signaling. Here, we describe that the expression of p85α is posttranscriptionally regulated in several human and murine leukemia cell lines and in a Hodgkin lymphoma cell line (CO) by translational repression. A detailed analysis of CO cells revealed that both wild type and a mutated p85α mRNA are detectable at similar ratios in the nucleus and polysomes. However, while the mutated p85α protein is expressed in CO cells, translation of the wild type p85α mRNA is completely inhibited. Ectopic expression of wild type p85α from a retroviral vector is suppressed in CO cells and in five out of six leukemia cell lines. Our data indicate that leukemia cells can regulate the expression of p85α by posttranscriptional regulation.
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Affiliation(s)
- Bianca T Hofmann
- Center of Experimental Medicine, Institute of Biochemistry and Molecular Biology I, Cellular Signal Transduction, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
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Vogt PK, Hart JR, Gymnopoulos M, Jiang H, Kang S, Bader AG, Zhao L, Denley A. Phosphatidylinositol 3-kinase: the oncoprotein. Curr Top Microbiol Immunol 2010. [PMID: 20582532 DOI: 10.1007/82-2010-80] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The catalytic and regulatory subunits of class I phosphoinositide 3-kinase (PI3K) have oncogenic potential. The catalytic subunit p110α and the regulatory subunit p85 undergo cancer-specific gain-of-function mutations that lead to enhanced enzymatic activity, ability to signal constitutively, and oncogenicity. The β, γ, and δ isoforms of p110 are cell-transforming as overexpressed wild-type proteins. Class I PI3Ks have the unique ability to generate phosphoinositide 3,4,5 trisphosphate (PIP(3)). Class II and class III PI3Ks lack this ability. Genetic and cell biological evidence suggests that PIP(3) is essential for PI3K-mediated oncogenicity, explaining why class II and class III enzymes have not been linked to cancer. Mutational analysis reveals the existence of at least two distinct molecular mechanisms for the gain of function seen with cancer-specific mutations in p110α; one causing independence from upstream receptor tyrosine kinases, the other inducing independence from Ras. An essential component of the oncogenic signal that is initiated by PI3K is the TOR (target of rapamycin) kinase. TOR is an integrator of growth and of metabolic inputs. In complex with the raptor protein (TORC1), it controls cap-dependent translation, and this function is essential for PI3K-initiated oncogenesis.
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Affiliation(s)
- Peter K Vogt
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA.
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Rotman T, Etkovitz N, Spiegel A, Rubinstein S, Breitbart H. Protein kinase A and protein kinase C(alpha)/PPP1CC2 play opposing roles in the regulation of phosphatidylinositol 3-kinase activation in bovine sperm. Reproduction 2010; 140:43-56. [PMID: 20442273 DOI: 10.1530/rep-09-0314] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
In order to acquire fertilization competence, spermatozoa have to undergo biochemical changes in the female reproductive tract, known as capacitation. Signaling pathways that take place during the capacitation process are much investigated issue. However, the role and regulation of phosphatidylinositol 3-kinase (PI3K) in this process are still not clear. Previously, we reported that short-time activation of protein kinase A (PRKA, PKA) leads to PI3K activation and protein kinase C(alpha)(PRKCA, PKC(alpha)) inhibition. In the present study, we found that during the capacitation PI3K phosphorylation/activation increases. PI3K activation was PRKA dependent, and down-regulated by PRKCA. PRKCA is found to be highly active at the beginning of the capacitation, conditions in which PI3K is not active. Moreover, inhibition of PRKCA causes significant activation of PI3K. Similar activation of PI3K is seen when the phosphatase PPP1 is blocked suggesting that PPP1 regulates PI3K activity. We found that during the capacitation PRKCA and PPP1CC2 (PP1gamma2) form a complex, and the two enzymes were degraded during the capacitation, suggesting that this degradation enables the activation of PI3K. This degradation is mediated by PRKA, indicating that in addition to the direct activation of PI3K by PRKA, this kinase can enhance PI3K phosphorylation indirectly by enhancing the degradation and inactivation of PRKCA and PPP1CC2.
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Affiliation(s)
- T Rotman
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 52900, Israel
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31
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Functional differences between two classes of oncogenic mutation in the PIK3CA gene. Biochem Biophys Res Commun 2009; 381:577-81. [PMID: 19233141 DOI: 10.1016/j.bbrc.2009.02.081] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2009] [Accepted: 02/18/2009] [Indexed: 02/07/2023]
Abstract
PIK3CA codes for the p110alpha isoform of class-IA PI 3-kinase and oncogenic mutations in the helical domain and kinase domain are common in several cancers. We studied the biochemical properties of a common helical domain mutant (E545K) and a common kinase domain mutant (H1047R). Both retain the ability to autophosphorylate Ser608 of p85alpha and are also inhibited by a range of PI 3-kinase inhibitors (Wortmannin, LY294002, PI-103 and PIK-75) to a similar extent as WT p110alpha. Both mutants display an increased V(max) but while a PDGF derived diphosphotyrosylpeptide caused an increase in V(max) for WT p85alpha/p110alpha it did not for the E545K variant and actually decreased V(max) for the H1047R variant. Further, the E545K mutant was activated by H-Ras whereas the H1047R mutant was not. Together these results suggest helical domain mutants are in a state mimicking activation by growth factors whereas kinase domain mutants mimic the state activated by H-Ras.
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Sagan D, Eckardt-Schupp F, Eichholtz-Wirth H. Reduced expression of SRC family kinases decreases PI3K activity in NBS1 lymphoblasts. Biochem Biophys Res Commun 2008; 377:181-6. [DOI: 10.1016/j.bbrc.2008.09.098] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2008] [Accepted: 09/22/2008] [Indexed: 12/11/2022]
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Abstract
Class I phosphoinositide 3-kinase (PI3K) is a dimeric enzyme, consisting of a catalytic and a regulatory subunit. The catalytic subunit occurs in four isoforms designated as p110 alpha, p110 beta, p110 gamma and p110 delta. These isoforms combine with several regulatory subunits; for p110 alpha, beta and delta, the standard regulatory subunit is p85, for p110 gamma, it is p101. PI3Ks play important roles in human cancer. PIK3CA, the gene encoding p110 alpha, is mutated frequently in common cancers, including carcinoma of the breast, prostate, colon and endometrium. Eighty percent of these mutations are represented by one of the three amino-acid substitutions in the helical or kinase domains of the enzyme. The mutant p110 alpha shows a gain of function in enzymatic and signaling activity and is oncogenic in cell culture and in animal model systems. Structural and genetic data suggest that the mutations affect regulatory inter- and intramolecular interactions and support the conclusion that there are at least two molecular mechanisms for the gain of function in p110 alpha. One of these mechanisms operates largely independently of binding to p85, the other abolishes the requirement for an interaction with Ras. The non-alpha isoforms of p110 do not show cancer-specific mutations. However, they are often differentially expressed in cancer and, in contrast to p110 alpha, wild-type non-alpha isoforms of p110 are oncogenic when overexpressed in cell culture. The isoforms of p110 have become promising drug targets. Isoform-selective inhibitors have been identified. Inhibitors that target exclusively the cancer-specific mutants of p110 alpha constitute an important goal and challenge for current drug development.
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Ciraolo E, Iezzi M, Marone R, Marengo S, Curcio C, Costa C, Azzolino O, Gonella C, Rubinetto C, Wu H, Dastrù W, Martin EL, Silengo L, Altruda F, Turco E, Lanzetti L, Musiani P, Rückle T, Rommel C, Backer JM, Forni G, Wymann MP, Hirsch E. Phosphoinositide 3-kinase p110beta activity: key role in metabolism and mammary gland cancer but not development. Sci Signal 2008; 1:ra3. [PMID: 18780892 DOI: 10.1126/scisignal.1161577] [Citation(s) in RCA: 205] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The phosphoinositide 3-kinase (PI3K) pathway crucially controls metabolism and cell growth. Although different PI3K catalytic subunits are known to play distinct roles, the specific in vivo function of p110beta (the product of the PIK3CB gene) is not clear. Here, we show that mouse mutants expressing a catalytically inactive PIK3CB(K805R) mutant survived to adulthood but showed growth retardation and developed mild insulin resistance with age. Pharmacological and genetic analyses of p110beta function revealed that p110beta catalytic activity is required for PI3K signaling downstream of heterotrimeric guanine nucleotide-binding protein (G protein)-coupled receptors as well as to sustain long-term insulin signaling. In addition, PIK3CB(K805R) mice were protected in a model of ERBB2-driven tumor development. These findings indicate an unexpected role for p110beta catalytic activity in diabetes and cancer, opening potential avenues for therapeutic intervention.
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Affiliation(s)
- Elisa Ciraolo
- Department of Genetics, Biology and Biochemistry, Molecular Biotechnology Center, University of Torino, Via Nizza 52, 10126 Torino, Italy
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Houck KL, Fox TE, Sandirasegarane L, Kester M. Ether-linked diglycerides inhibit vascular smooth muscle cell growth via decreased MAPK and PI3K/Akt signaling. Am J Physiol Heart Circ Physiol 2008; 295:H1657-68. [PMID: 18723771 DOI: 10.1152/ajpheart.00141.2008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Diglycerides (DGs) are phospholipid-derived second messengers that regulate PKC-dependent signaling pathways. Distinct species of DGs are generated from inflammatory cytokines and growth factors. Growth factors increase diacyl- but not ether-linked DG species, whereas inflammatory cytokines predominately generate alkyl, acyl- and alkenyl, acyl-linked DG species in rat mesenchymal cells. These DG species have been shown to differentially regulate protein kinase C (PKC) isotypes. Ester-linked diacylglycerols activate PKC-epsilon and cellular proliferation in contrast to ether-linked DGs, which lead to growth arrest through the inactivation of PKC-epsilon. It is now hypothesized that ether-linked DGs inhibit mitogenesis through the inactivation of ERK and/or Akt signaling cascades. We demonstrate that cell-permeable ether-linked DGs reduce vascular smooth muscle cell growth by inhibiting platelet-derived growth factor-stimulated ERK in a PKC-epsilon-dependent manner. This inhibition is specific to the ERK pathway, since ether-linked DGs do not affect growth factor-induced activation of other family members of the MAPKs, including p38 MAPK and c-Jun NH(2)-terminal kinases. We also demonstrate that ether-linked DGs reduce prosurvival phosphatidylinositol 3-kinase (PI3K)/Akt signaling, independent of PKC-epsilon, by diminishing an interaction between the subunits of PI3K and not by affecting protein phosphatase 2A or lipid (phosphatase and tensin homologue deleted in chromosome 10) phosphatases. Taken together, our studies identify ether-linked DGs as potential adjuvant therapies to limit vascular smooth muscle migration and mitogenesis in atherosclerotic and restenotic models.
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Affiliation(s)
- Kristy L Houck
- Department of Pharmacology, College of Medicine, Pennsylvania State University, Hershey, Pennsylvania 17033, USA
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Thirunavukkarasu M, Addya S, Juhasz B, Pant R, Zhan L, Surrey S, Maulik G, Menon VP, Maulik N. Heterozygous disruption of Flk-1 receptor leads to myocardial ischaemia reperfusion injury in mice: application of affymetrix gene chip analysis. J Cell Mol Med 2008; 12:1284-302. [PMID: 18266966 PMCID: PMC3865673 DOI: 10.1111/j.1582-4934.2008.00269.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
This study addresses an important clinical issue by identifying potential candidates of vascular endothelial growth factor (VEGF) signalling through the Flk-1 receptor that trigger cardioprotective signals under ischaemic stress. Isolated working mouse hearts of both wild-type (WT) and Flk-1+/− were subjected to global ischaemia (I) for 30 min. followed by 2 hrs of reperfusion (R). Flk-1+/− myocardium displayed almost 50% reduction in Flk-1 mRNA as examined by quantitative real-time RT-PCR at the baseline level. Flk-1+/− mouse hearts displayed reduction in left ventricular functional recovery throughout reperfusion (dp/dt 605 versus 884), after 2 hrs (P < 0.05). Coronary (1.9 versus 2.4 ml) and aortic flow (AF) (0.16 versus 1.2 ml) were reduced in Flk-1+/− after 2 hrs of reperfusion. In addition, increased infarct size (38.4%versus 28.41%, P < 0.05) and apoptotic cardiomyocytes (495 versus 213) were observed in Flk-1+/− knockout (KO) mice. We also examined whether ischaemic preconditioning (PC), a novel method to induce cardioprotection against ischaemia reperfusion injury, through stimulating the VEGF signalling pathway might function in Flk-1+/− mice. We found that knocking down Flk-1 resulted in significant reduction in the cardioprotective effect by PC compared to WT. Affymetrix gene chip analysis demonstrated down-regulation of important genes after IR and preconditioning followed by ischaemia reperfusion in Flk-1+/− mice compared to WT. To get insight into the underlying molecular pathways involved in ischaemic PC, we determined the distinct and overlapping biological processes using Ingenuity pathway analysis tool. Independent evidence at the mRNA level supporting the Affymetrix results were validated using real-time RT-PCR for selected down-regulated genes, which are thought to play important roles in cardioprotection after ischaemic insult. In summary, our data indicated for the first time that ischaemic PC modifies genomic responses in heterozygous VEGFR-2/Flk-1 KO mice and abolishes its cardioprotective effect on ischaemic myocardium.
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Affiliation(s)
- M Thirunavukkarasu
- Department of Surgery, Molecular Cardiology and Angiogenesis Laboratory, University of Connecticut Health CenterFarmington, CT, USA
- Department of Biochemistry and Biotechnology, Annamalai UniversityTN, India
| | - S Addya
- Cancer Genomics Facility, Kimmel Cancer Center, Thomas Jefferson UniversityPhiladelphia, PA, USA
| | - B Juhasz
- Department of Surgery, Molecular Cardiology and Angiogenesis Laboratory, University of Connecticut Health CenterFarmington, CT, USA
- Department of Pharmacology, University of DebrecenHungary
| | - R Pant
- Department of Surgery, Molecular Cardiology and Angiogenesis Laboratory, University of Connecticut Health CenterFarmington, CT, USA
| | - L Zhan
- Department of Surgery, Molecular Cardiology and Angiogenesis Laboratory, University of Connecticut Health CenterFarmington, CT, USA
| | - S Surrey
- Cardeza Foundation for Hematologic Research, Department of Medicine, Thomas Jefferson UniversityPhiladelphia, PA, USA
| | - G Maulik
- Department of Thoracic Surgery, Harvard Medical SchoolBoston, MA, USA
| | - V P Menon
- Department of Biochemistry and Biotechnology, Annamalai UniversityTN, India
| | - N Maulik
- Department of Surgery, Molecular Cardiology and Angiogenesis Laboratory, University of Connecticut Health CenterFarmington, CT, USA
- *Correspondence to: Nilanjana MAULIK, Ph.D., FACN, FICA, Department of Surgery, Molecular Cardiology and Angiogenesis Laboratory, University of Connecticut Health Center, 263 Farmington Avenue, Farmington, CT 06030-1110, USA. Tel.: (860) 679-2857 Fax: (860) 679-2825 E-mail:
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Lu G, Wang Y. FUNCTIONAL DIVERSITY OF MAMMALIAN TYPE 2C PROTEIN PHOSPHATASE ISOFORMS: NEW TALES FROM AN OLD FAMILY. Clin Exp Pharmacol Physiol 2008; 35:107-12. [DOI: 10.1111/j.1440-1681.2007.04843.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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Hale BG, Batty IH, Downes CP, Randall RE. Binding of influenza A virus NS1 protein to the inter-SH2 domain of p85 suggests a novel mechanism for phosphoinositide 3-kinase activation. J Biol Chem 2007; 283:1372-1380. [PMID: 18029356 DOI: 10.1074/jbc.m708862200] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Influenza A virus NS1 protein stimulates host-cell phosphoinositide 3-kinase (PI3K) signaling by binding to the p85beta regulatory subunit of PI3K. Here, in an attempt to establish a mechanism for this activation, we report further on the functional interaction between NS1 and p85beta. Complex formation was found to be independent of NS1 RNA binding activity and is mediated by the C-terminal effector domain of NS1. Intriguingly, the primary direct binding site for NS1 on p85beta is the inter-SH2 domain, a coiled-coil structure that acts as a scaffold for the p110 catalytic subunit of PI3K. In vitro kinase activity assays, together with protein binding competition studies, reveal that NS1 does not displace p110 from the inter-SH2 domain, and indicate that NS1 can form an active heterotrimeric complex with PI3K. In addition, it was established that residues at the C terminus of the inter-SH2 domain are essential for mediating the interaction between p85beta and NS1. Equivalent residues in p85alpha have previously been implicated in the basal inhibition of p110. However, such p85alpha residues were unable to substitute for those in p85beta with regards NS1 binding. Overall, these data suggest a model by which NS1 activates PI3K catalytic activity by masking a normal regulatory element specific to the p85beta inter-SH2 domain.
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Affiliation(s)
- Benjamin G Hale
- Centre for Biomolecular Sciences, University of St. Andrews, St. Andrews, Fife KY16 9ST, United Kingdom.
| | - Ian H Batty
- Division of Molecular Physiology, Faculty of Life Sciences, University of Dundee, Dundee DD1 5EH, United Kingdom
| | - C Peter Downes
- Division of Molecular Physiology, Faculty of Life Sciences, University of Dundee, Dundee DD1 5EH, United Kingdom
| | - Richard E Randall
- Centre for Biomolecular Sciences, University of St. Andrews, St. Andrews, Fife KY16 9ST, United Kingdom
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Bousquet C, Guillermet-Guibert J, Saint-Laurent N, Archer-Lahlou E, Lopez F, Fanjul M, Ferrand A, Fourmy D, Pichereaux C, Monsarrat B, Pradayrol L, Estève JP, Susini C. Direct binding of p85 to sst2 somatostatin receptor reveals a novel mechanism for inhibiting PI3K pathway. EMBO J 2006; 25:3943-54. [PMID: 16917505 PMCID: PMC1560358 DOI: 10.1038/sj.emboj.7601279] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2005] [Accepted: 07/21/2006] [Indexed: 12/16/2022] Open
Abstract
Phosphatidylinositol 3-kinase (PI3K) regulates many cellular functions including growth and survival, and its excessive activation is a hallmark of cancer. Somatostatin, acting through its G protein-coupled receptor (GPCR) sst2, has potent proapoptotic and anti-invasive activities on normal and cancer cells. Here, we report a novel mechanism for inhibiting PI3K activity. Somatostatin, acting through sst2, inhibits PI3K activity by disrupting a pre-existing complex comprising the sst2 receptor and the p85 PI3K regulatory subunit. Surface plasmon resonance and molecular modeling identified the phosphorylated-Y71 residue of a p85-binding pYXXM motif in the first sst2 intracellular loop, and p85 COOH-terminal SH2 as direct interacting domains. Somatostatin-mediated dissociation of this complex as well as p85 tyrosine dephosphorylation correlates with sst2 tyrosine dephosphorylation on the Y71 residue. Mutating sst2-Y71 disabled sst2 to interact with p85 and somatostatin to inhibit PI3K, consequently abrogating sst2's ability to suppress cell survival and tumor growth. These results provide the first demonstration of a physical interaction between a GPCR and p85, revealing a novel mechanism for negative regulation by ligand-activated GPCR of PI3K-dependent survival pathways, which may be an important molecular target for antineoplastic therapy.
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Affiliation(s)
- Corinne Bousquet
- INSERM U531, Institut Louis Bugnard, CHU Rangueil, Toulouse cedex 4, France.
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40
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Déléris P, Gayral S, Breton-Douillon M. Nuclear Ptdlns(3,4,5)P3 signaling: an ongoing story. J Cell Biochem 2006; 98:469-85. [PMID: 16645993 DOI: 10.1002/jcb.20695] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Phosphatidylinositol 3,4,5-trisphosphate (Ptdlns(3,4,5)P(3)) is linked to a variety of cellular functions, such as growth, cell survival, and differentiation. Ptdlns(3,4,5)P(3) is primarily synthesized by class I phosphoinositide 3-kinases and its hydrolysis by two 3-phosphoinositide 3-phosphatases, PTEN and SHIP proteins, leads to the production of two other second messengers, Ptdlns(4,5)P(2) and Ptdlns(3,4)P(2), respectively. Evidence accumulated over the last years strongly suggest that Ptdlns(3,4,5)P(3) is an important component of signaling pathway operating within the nucleus. Moreover, recent advances indicated that nuclear translocation of cell surface receptors could activate nuclear phosphoinositide 3-kinase suggesting a new mode of signal transduction. The aim of this review is intended to summarize the state of our knowledge on nuclear Ptdlns(3,4,5)P(3) and its metabolizing enzymes, and to highlight the emerging roles for intranuclear Ptdlns(3,4,5)P(3).
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Affiliation(s)
- Paul Déléris
- Laboratoire de Signalisation et Croissance Cellulaire, Institut de Recherche en Immunovirologie et Cancérologie, Université de Montréal, Montréal, QC H3T 1J4 Canada
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41
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Vinciguerra M, Foti M. PTEN and SHIP2 phosphoinositide phosphatases as negative regulators of insulin signalling. Arch Physiol Biochem 2006; 112:89-104. [PMID: 16931451 DOI: 10.1080/13813450600711359] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Insulin resistance in peripheral tissues is the primary cause responsible for onset of type II diabetes mellitus. Recently, the genetic and biochemical dissection of intracellular signalling pathways transducing the metabolic and mitogenic effects of insulin has contributed to the understanding of the molecular causes of this insulin resistance. In particular, important efforts have been developed to comprehend the role of negative regulators of insulin signalling, since they might represent future therapeutical targets to reduce insulin resistance in peripheral tissues. Herein, we will briefly review major intracellular signalling pathways activated by insulin and how they are negatively regulated by distinct mechanisms. In particular, the role of PTEN and SHIP2, two phosphoinositide phosphatases recently implicated as negative modulators of insulin signalling, is in focus. Current knowledge on the role of PTEN and SHIP2 in insulin resistance, type II diabetes and related disorders will also be discussed.
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Affiliation(s)
- Manlio Vinciguerra
- Department of Cellular Physiology and Metabolism, Faculty of Medicine, University of Geneva, Geneva, Switzerland
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Kubo H, Hazeki K, Takasuga S, Hazeki O. Specific role for p85/p110beta in GTP-binding-protein-mediated activation of Akt. Biochem J 2006; 392:607-14. [PMID: 16091017 PMCID: PMC1316301 DOI: 10.1042/bj20050671] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
We prepared CHO (Chinese hamster ovary) cells expressing both IR (insulin receptor) and A1R (A1 adenosine receptor). Treatment of the cells with insulin or PIA [N6-(2-phenylisopropyl)adenosine], a specific A(1)R agonist increased Akt activity in the cells in a PI3K- (phosphoinositide 3-kinase) dependent manner. Transfection of p110beta into the cells augmented the action of PIA with little effect on insulin. Introduction of a pH1 vector producing shRNA (short hairpin RNA) that targets p110beta abolished PIA-induced Akt activation. By contrast, an shRNA probe targeting p110alpha did not impair the effects of PIA. The effect of PIA in p110alpha-deficient cells was attenuated effectively by both Deltap85 and betaARK-CT (beta-adrenergic receptor kinase-C-terminal peptide). A Deltap85-derived protein possessing point mutations in its two SH2 domains did not impair PIA action. These results suggest that tyrosine-phosphorylated proteins and Gbetagamma (betagamma subunits of GTP-binding protein) are necessary for the specific function of p110beta in intact cells. The p110beta-middle (middle part of p110beta) may play an important role in signal reception from GPCRs (GTP-binding-protein-coupled receptor), because transfection of the middle part impaired PIA sensitivity.
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Affiliation(s)
- Hiroshi Kubo
- Division of Molecular Medical Science, Graduate School of Biomedical Sciences, Hiroshima University, Hiroshima 734-8551, Japan
| | - Kaoru Hazeki
- Division of Molecular Medical Science, Graduate School of Biomedical Sciences, Hiroshima University, Hiroshima 734-8551, Japan
| | - Shunsuke Takasuga
- Division of Molecular Medical Science, Graduate School of Biomedical Sciences, Hiroshima University, Hiroshima 734-8551, Japan
| | - Osamu Hazeki
- Division of Molecular Medical Science, Graduate School of Biomedical Sciences, Hiroshima University, Hiroshima 734-8551, Japan
- To whom correspondence should be addressed (email )
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Kang S, Denley A, Vanhaesebroeck B, Vogt PK. Oncogenic transformation induced by the p110beta, -gamma, and -delta isoforms of class I phosphoinositide 3-kinase. Proc Natl Acad Sci U S A 2006; 103:1289-94. [PMID: 16432180 PMCID: PMC1360601 DOI: 10.1073/pnas.0510772103] [Citation(s) in RCA: 226] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Class I phosphoinositide 3-kinase contains four isoforms of the catalytic subunit, p110alpha, -beta, -gamma, and -delta. At physiological levels of expression, the wild-type p110alpha isoform lacks oncogenic potential, but gain-of-function mutations and overexpression of p110alpha are correlated with oncogenicity. The p110beta, -gamma, and -delta isoforms induce transformation of cultured cells as wild-type proteins. This oncogenic potential requires kinase activity and can be suppressed by the target of rapamycin inhibitor rapamycin. The p110delta isoform constitutively activates the Akt signaling pathway; p110gamma activates Akt only in the presence of serum. The isoforms differ in their requirements for upstream signaling. The transforming activity of the p110gamma isoform depends on rat sarcoma viral oncogene homolog (Ras) binding; preliminary data suggest the same for p110beta and indicate Ras-independent oncogenic potential of p110delta. The surprising oncogenic potential of the wild-type non-alpha isoforms of class I phosphoinositide 3-kinase may explain the dearth of cancer-specific mutations in these proteins, because these non-alpha isoforms could contribute to the oncogenic phenotype of the cell by differential expression.
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Affiliation(s)
- Sohye Kang
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, 10550 North Torrey Pines Road, BCC 239, La Jolla, CA 92037, USA
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Bilancio A, Okkenhaug K, Camps M, Emery JL, Ruckle T, Rommel C, Vanhaesebroeck B. Key role of the p110δ isoform of PI3K in B-cell antigen and IL-4 receptor signaling: comparative analysis of genetic and pharmacologic interference with p110δ function in B cells. Blood 2006; 107:642-50. [PMID: 16179367 DOI: 10.1182/blood-2005-07-3041] [Citation(s) in RCA: 179] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
AbstractMouse gene–targeting studies have documented a central role of the p110δ isoform of phosphoinositide 3-kinase (PI3K) in B-cell development and function. A defect in B-cell antigen receptor (BCR) signaling is key to this B-cell phenotype. Here we further characterize this signaling defect and report that a p110δ-selective small molecule inhibitor mirrors the effect of genetic inactivation of p110δ in BCR signaling. p110δ activity is indispensable for BCR-induced DNA synthesis and phosphorylation of Akt/protein kinase B (PKB), forkhead transcription factor/forkhead box O3a (FOXO3a), and p70 S6 kinase (p70 S6K), with modest effects on the phosphorylation of glycogen synthase kinase 3 α/β (GSK3α/β) and extracellular signal-regulated kinase (Erk). The PI3K-dependent component of intracellular calcium mobilization also completely relies on p110δ catalytic activity. Resting B cells with inactive p110δ fail to enter the cell cycle, correlating with an incapacity to up-regulate the expression of cyclins D2, A, and E, and to phosphorylate the retinoblastoma protein (Rb). p110δ is also critical for interleukin 4 (IL-4)–induced phosphorylation of Akt/PKB and FOXO3a, and protection from apoptosis. Taken together, these data show that defects observed in p110δ mutant mice are not merely a consequence of altered B-cell differentiation, and emphasize the potential utility of p110δ as a drug target in autoimmune diseases in which B cells play a crucial role.
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Affiliation(s)
- Antonio Bilancio
- Ludwig Institute for Cancer Research, 91 Riding House Street, London, W1W 7BS, United Kingdom
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Martelli AM, Follo MY, Evangelisti C, Falà F, Fiume R, Billi AM, Cocco L. Nuclear inositol lipid metabolism: more than just second messenger generation? J Cell Biochem 2005; 96:285-92. [PMID: 16088939 DOI: 10.1002/jcb.20527] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
A distinct polyphosphoinositide cycle is present in the nucleus, and growing evidence suggests its importance in DNA replication, gene transcription, and apoptosis. Even though it was initially thought that nuclear inositol lipids would function as a source for second messengers, recent findings strongly indicate that lipids present in the nucleus also fulfil other roles. The scope of this review is to highlight the most intriguing advances made in the field over the last few years, such as the possibility that nuclear phosphatidylinositol (4,5) bisphosphate is involved in maintaining chromatin in a transcriptionally active conformation, the new emerging roles for intranuclear phosphatidylinositol (3,4,5) trisphosphate and phosphoinositide 3-kinase, and the evidence which suggests a tight relationship between a decreased level of nuclear phosphoinositide specific phospholipase C-beta1 and the evolution of myelodisplastic syndrome into acute myeloid leukemia.
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Affiliation(s)
- Alberto M Martelli
- Dipartimento di Scienze Anatomiche Umane e Fisiopatologia dell'Apparato Locomotore, Sezione di Anatomia Umana, Cell Signalling Laboratory, Università di Bologna, 40126 Bologna, Italy
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46
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Shekar SC, Wu H, Fu Z, Yip SC, Cahill SM, Girvin ME, Backer JM. Mechanism of Constitutive Phosphoinositide 3-Kinase Activation by Oncogenic Mutants of the p85 Regulatory Subunit. J Biol Chem 2005; 280:27850-5. [PMID: 15932879 DOI: 10.1074/jbc.m506005200] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
p85/p110 phosphoinositide 3-kinases regulate multiple cell functions and are frequently mutated in human cancer. The p85 regulatory subunit stabilizes and inhibits the p110 catalytic subunit. The minimal fragment of p85 capable of regulating p110 is the N-terminal SH2 domain linked to the coiled-coil iSH2 domain (referred to as p85ni). We have previously proposed that the conformationally rigid iSH2 domain tethers p110 to p85, facilitating regulatory interactions between p110 and the p85 nSH2 domain. In an oncogenic mutant of murine p85, truncation at residue 571 leads to constitutively increased phosphoinositide 3-kinase activity, which has been proposed to result from either loss of an inhibitory Ser-608 autophosphorylation site or altered interactions with cellular regulatory factors. We have examined this mutant (referred to as p65) in vitro and find that p65 binds but does not inhibit p110, leading to constitutive p110 activity. This activated phenotype is observed with recombinant proteins in the absence of cellular factors. Importantly, this effect is also produced by truncating p85ni at residue 571. Thus, the phenotype is not because of loss of the Ser-608 inhibitory autophosphorylation site, which is not present in p85ni. To determine the structural basis for the phenotype of p65, we used a broadly applicable spin label/NMR approach to define the positioning of the nSH2 domain relative to the iSH2 domain. We found that one face of the nSH2 domain packs against the 581-593 region of the iSH2 domain. The loss of this interaction in the truncated p65 would remove the orienting constraints on the nSH2 domain, leading to a loss of p110 regulation by the nSH2. Based on these findings, we propose a general model for oncogenic mutants of p85 and p110 in which disruption of nSH2-p110 regulatory contacts leads to constitutive p110 activity.
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Affiliation(s)
- S Chandra Shekar
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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47
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Yip SC, El-Sibai M, Hill KM, Wu H, Fu Z, Condeelis JS, Backer JM. Over-expression of the p110beta but not p110alpha isoform of PI 3-kinase inhibits motility in breast cancer cells. ACTA ACUST UNITED AC 2005; 59:180-8. [PMID: 15468162 DOI: 10.1002/cm.20032] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Phosphoinositide 3-kinase (PI 3-kinase) activity is required for growth factor-induced cytoskeletal regulation and cell migration. We previously found that in MTLn3 rat adenocarcinoma cells, EGF-stimulated induction of actin barbed ends and lamellipod extension specifically requires the p85/p110alpha isoform of PI 3-kinase. To further characterize signaling by distinct PI 3-kinase isoforms, we have developed MTLn3 cells that transiently or stably overexpress either p110alpha or p110beta. Transient overexpression of p110beta inhibited EGF-stimulated lamellipod extension, whereas p110alpha-transfected cells showed normal EGF-stimulated lamellipod extension. Similar results were obtained by overexpression of kinase-dead p110beta, suggesting that effects on cytoskeletal signaling were due to competition with p85/p110alpha complexes. Stable overexpression of p110alpha appeared to be toxic, based on the difficulty in obtaining stable overexpressing clones. In contrast, cells expressing a 2-fold increase in p110beta were readily obtainable. Interestingly, cells stably expressing p110beta showed a marked inhibition of EGF-stimulated lamellipod extension. Using computer-assisted analysis of time-lapse images, we found that overexpression of p110beta caused a nearly complete inhibition of motility. Cells overexpressing p110beta showed normal activation of Akt and Erk, suggesting that overall PI 3-kinase signaling was intact. A chimeric p110 molecule containing the p85-binding and Ras-binding domains of p110alpha and the C2, helical, and kinase domains of p110beta, was catalytically active yet also inhibited EGF-stimulated lamellipod extension. These data highlight the differential signaling by distinct p110 isoforms. Identification of effectors that are differently regulated by p110alpha versus p110beta will be important for understanding cell migration and its role in metastasis.
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Affiliation(s)
- Shu-Chin Yip
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA
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Vanhaesebroeck B, Ali K, Bilancio A, Geering B, Foukas LC. Signalling by PI3K isoforms: insights from gene-targeted mice. Trends Biochem Sci 2005; 30:194-204. [PMID: 15817396 DOI: 10.1016/j.tibs.2005.02.008] [Citation(s) in RCA: 357] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Phosphoinositide 3-kinases (PI3Ks) generate lipids that control a wide variety of intracellular signalling pathways. Part of this diversity in PI3K actions stems from the broad range of protein effectors of the PI3K lipids. A further layer of complexity is added by the existence of multiple isoforms of PI3K. Gene-targeting studies in the mouse have recently uncovered key roles for specific PI3K isoforms in immunity, metabolism and cardiac function. Remarkably, some of these actions do not require PI3K catalytic activity. In addition, loss-of-expression of certain PI3K genes leads to increased PI3K signalling following insulin stimulation. PI3K gene targeting has, in many cases, led to altered expression of the non-targeted PI3K subunits, making it difficult to exclude that some of the reported phenotypes result from 'knock-on' effects of PI3K gene deletion. Targeting strategies that take into account the complex interplay between members of the PI3K family will be crucial to gain a full understanding of the physiological roles of the isoforms of PI3K.
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Affiliation(s)
- Bart Vanhaesebroeck
- Ludwig Institute for Cancer Research, 91 Riding House Street, London W1W 7BS, UK.
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49
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Shepherd PR. Mechanisms regulating phosphoinositide 3-kinase signalling in insulin-sensitive tissues. ACTA ACUST UNITED AC 2005; 183:3-12. [PMID: 15654916 DOI: 10.1111/j.1365-201x.2004.01382.x] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A great deal of evidence has accumulated indicating that the activity of PI 3-kinase is necessary, and in some cases sufficient, for a wide range of insulin's actions in the cell. Most biochemical, genetic and pharmacological studies have focused on identifying potential roles for the class-Ia PI 3-kinases which are rapidly activated following insulin stimulation. However, recent evidence indicates the alpha isoform of class-II PI 3-kinase (PI3K-C2alpha) may also play a role as insulin causes a very rapid activation of this as well. The basic mechanisms by which insulin activates the various members of the PI 3-kinase family are increasingly well understood and these studies reveal multiple mechanisms for modulating the activity and functionality of PI 3-kinase and for down regulating the signals they generate. These include inhibitory phosphorylation events, lipid phosphatases such as PTEN and SHIP2 and inhibitor proteins of the suppressors of cytokine signalling (SOCS) family. The current review will focus on these mechanisms and how defects in these might contribute to the development of insulin resistance.
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Affiliation(s)
- P R Shepherd
- Department of Biochemistry and Molecular Biology, University College London, Gower St, London WC1E 6BT, UK
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50
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Li L, Grønning LM, Anderson PO, Li S, Edvardsen K, Johnston J, Kioussis D, Shepherd PR, Wang P. Insulin Induces SOCS-6 Expression and Its Binding to the p85 Monomer of Phosphoinositide 3-Kinase, Resulting in Improvement in Glucose Metabolism. J Biol Chem 2004; 279:34107-14. [PMID: 15123678 DOI: 10.1074/jbc.m312672200] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The suppressors of cytokine signaling (SOCS) family is thought to act largely as a negative regulator of signaling by cytokines and some growth factors. Surprisingly, the SOCS-6 transgenics had no significant defects in the cytokine signaling and hematopoietic system but displayed significant improvements in glucose metabolism. Insulin stimulation of Akt/protein kinase B was also potentiated. Biochemical analysis showed that, after insulin stimulation, SOCS-6 interacted with the monomeric p85 subunit of class-Ia phosphoinositide (PI) 3-kinase but not with p85/p110 dimers. Furthermore, SOCS-6 expression is transiently increased by serum and insulin in normal fibroblasts. However, both the mRNA and protein of SOCS-6 were rapidly degraded after induction by insulin. The degradation of the SOCS-6 protein was partially inhibited by a proteasome inhibitor, suggesting a proteasome-mediated degradation mechanism. In contrast, SOCS-6-associated p85 was not degraded and could be recruited to the newly synthesized SOCS-6 molecules in the presence of insulin, suggesting that SOCS-6 expression and its interaction with p85, but not the degradation, is regulated by insulin. The phenotype of SOCS-6 transgenic mice bears a striking resemblance to p85 knock-out mouse models in which glucose metabolism stimulated by insulin is significantly improved despite reduced activation of PI 3-kinase. This suggests that monomeric p85 might play a physiologically important role in attenuating signaling through PI 3-kinase-dependent pathways in unstimulated cells. Therefore, our results indicate that SOCS-6 may provide a dynamically regulated mechanism by which insulin can transiently overcome the negative effects that p85 monomers have on signaling via PI 3-kinase-dependent signaling pathways.
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Affiliation(s)
- Li Li
- Immunology Group, Institute of Cell and Molecular Sciences, St. Barts and The Royal London School of Medicine, 59 Bartholomew's Close, London EC1A 7ED, United Kingdom
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