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Braccini L, Ciraolo E, Martini M, Pirali T, Germena G, Rolfo K, Hirsch E. PI3K keeps the balance between metabolism and cancer. Adv Biol Regul 2012; 52:389-405. [PMID: 22884032 DOI: 10.1016/j.jbior.2012.04.002] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2012] [Accepted: 04/11/2012] [Indexed: 06/01/2023]
Abstract
Epidemiological studies have established a positive correlation between cancer and metabolic disorders, suggesting that aberrant cell metabolism is a common feature of nearly all tumors. To meet their demand of building block molecules, cancer cells switch to a heavily glucose-dependent metabolism. As insulin triggers glucose uptake, most tumors are or become insulin-dependent. However, the effects of insulin and of other similar growth factors are not only limited to metabolic control but also favor tumor growth by stimulating proliferation and survival. A key signaling event mediating these metabolic and proliferative responses is the activation of the phosphatidylinositol-3 kinases (PI3K) pathway. In this review, we will thus discuss the current concepts of tumor metabolism and the opportunity of PI3K-targeted therapies to exploit the "sweet tooth" of cancer cells.
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Affiliation(s)
- L Braccini
- Department of Genetics, Biology and Biochemistry, Molecular Biotechnology Center, University of Torino, Torino, Italy
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102
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How phosphoinositide 3-phosphate controls growth downstream of amino acids and autophagy downstream of amino acid withdrawal. Biochem Soc Trans 2012; 40:37-43. [PMID: 22260663 DOI: 10.1042/bst20110684] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The simple phosphoinositide PtdIns3P has been shown to control cell growth downstream of amino acid signalling and autophagy downstream of amino acid withdrawal. These opposing effects depend in part on the existence of distinct complexes of Vps34 (vacuolar protein sorting 34), the kinase responsible for the majority of PtdIns3P synthesis in cells: one complex is activated after amino acid withdrawal to induce autophagy and another regulates mTORC1 (mammalian target of rapamycin complex 1) activation when amino acids are present. However, lipid-dependent signalling almost always exhibits a spatial dimension, related to the site of formation of the lipid signal. In the case of PtdIns3P-regulated autophagy induction, recent data suggest that PtdIns3P accumulates in a membrane compartment dynamically connected to the endoplasmic reticulum that constitutes a platform for the formation of some autophagosomes. For PtdIns3P-regulated mTORC1 activity, a spatial context is not yet known: several possibilities can be envisaged based on the known effects of PtdIns3P on the endocytic system and on recent data suggesting that activation of mTORC1 depends on its localization on lysosomes.
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103
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Falasca M, Maffucci T. Regulation and cellular functions of class II phosphoinositide 3-kinases. Biochem J 2012; 443:587-601. [PMID: 22507127 DOI: 10.1042/bj20120008] [Citation(s) in RCA: 116] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Class II isoforms of PI3K (phosphoinositide 3-kinase) are still the least investigated and characterized of all PI3Ks. In the last few years, an increased interest in these enzymes has improved our understanding of their cellular functions. However, several questions still remain unanswered on their mechanisms of activation, their specific downstream effectors and their contribution to physiological processes and pathological conditions. Emerging evidence suggests that distinct PI3Ks activate different signalling pathways, indicating that their functional roles are probably not redundant. In the present review, we discuss the recent advances in our understanding of mammalian class II PI3Ks and the evidence suggesting their involvement in human diseases.
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Affiliation(s)
- Marco Falasca
- Inositide Signalling Group, Centre for Diabetes, Blizard Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, 4 Newark Street, London E1 2AT, UK.
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104
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Monet M, Francoeur N, Boulay G. Involvement of phosphoinositide 3-kinase and PTEN protein in mechanism of activation of TRPC6 protein in vascular smooth muscle cells. J Biol Chem 2012; 287:17672-17681. [PMID: 22493444 DOI: 10.1074/jbc.m112.341354] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
TRPC6 is a cation channel in the plasma membrane that plays a role in Ca(2+) entry after the stimulation of a G(q)-protein-coupled or tyrosine-kinase receptor. TRPC6 translocates to the plasma membrane upon stimulation and remains there as long as the stimulus is present. However, the mechanism that regulates the trafficking and activation of TRPC6 are unclear. In this study we showed phosphoinositide 3-kinase and its antagonistic phosphatase, PTEN, are involved in the activation of TRPC6. The inhibition of PI3K by PIK-93, LY294002, or wortmannin decreased carbachol-induced translocation of TRPC6 to the plasma membrane and carbachol-induced net Ca(2+) entry into T6.11 cells. Conversely, a reduction of PTEN expression did not affect carbachol-induced externalization of TRPC6 but increased Ca(2+) entry through TRPC6 in T6.11 cells. We also showed that the PI3K/PTEN pathway regulates vasopressin-induced translocation of TRPC6 to the plasma membrane and vasopressin-induced Ca(2+) entry into A7r5 cells, which endogenously express TRPC6. In summary, we provided evidence that the PI3K/PTEN pathway plays an important role in the translocation of TRPC6 to the plasma membrane and may thus have a significant impact on Ca(2+) signaling in cells that endogenously express TRPC6.
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Affiliation(s)
- Michaël Monet
- Department of Pharmacology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Quebec J1H 5N4, Canada
| | - Nancy Francoeur
- Department of Pharmacology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Quebec J1H 5N4, Canada
| | - Guylain Boulay
- Department of Pharmacology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Quebec J1H 5N4, Canada.
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105
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Abstract
Oomycete and fungal symbionts have significant impacts on most commercially important crop and forest species, and on natural ecosystems, both negatively as pathogens and positively as mutualists. Symbiosis may be facilitated through the secretion of effector proteins, some of which modulate a variety of host defense mechanisms. A subset of these secreted proteins are able to translocate into host cells. In the oomycete pathogens, two conserved N-terminal motifs, RXLR and dEER, mediate translocation of effector proteins into host cells independent of any pathogen-encoded machinery. An expanded 'RXLR-like' motif [R/K/H]X[L/M/I/F/Y/W]X has been used to identify functional translocation motifs in host-cell-entering fungal effector proteins from pathogens and a mutualist. The RXLR-like translocation motifs were required for the fungal effectors to enter host cells in the absence of any pathogen-encoded machinery. Oomycete and fungal effectors with RXLR and RXLR-like motifs can bind phospholipids, specifically phosphatidylinositol-3-phosphate (PtdIns-3-P). Effector-PtdIns-3-P binding appears to mediate cell entry via lipid raft-mediated endocytosis, and could be blocked by sequestering cell surface PtdIns-3-P or by utilizing inositides that competitively inhibit effector binding to PtdIns-3-P. These findings suggest that effector blocking technologies could be developed and utilized in a variety of important crop species against a broad spectrum of plant pathogens.
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Affiliation(s)
- Shiv D Kale
- Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, VA 24061, USA.
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106
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Abstract
Phosphoinositide 3-kinases (PI3Ks) control cell growth, proliferation, cell survival, metabolic activity, vesicular trafficking, degranulation, and migration. Through these processes, PI3Ks modulate vital physiology. When over-activated in disease, PI3K promotes tumor growth, angiogenesis, metastasis or excessive immune cell activation in inflammation, allergy and autoimmunity. This chapter will introduce molecular activation and signaling of PI3Ks, and connections to target of rapamycin (TOR) and PI3K-related protein kinases (PIKKs). The focus will be on class I PI3Ks, and extend into current developments to exploit mechanistic knowledge for therapy.
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Affiliation(s)
- Matthias Wymann
- Institute Biochemistry & Genetics, Department Biomedicine, University of Basel, Mattenstrasse 28, 4058, Basel, Switzerland,
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107
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Abstract
Phosphoinositides play an essential role in insulin signaling, serving as a localization signal for a variety of proteins that participate in the regulation of cellular growth and metabolism. This chapter will examine the regulation and localization of phosphoinositide species, and will explore the roles of these lipids in insulin action. We will also discuss the changes in phosphoinositide metabolism that occur in various pathophysiological states such as insulin resistance and diabetes.
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Affiliation(s)
- Dave Bridges
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109, USA
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108
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Abstract
Phosphoinositides (PIs) are minor components of cellular membranes that play critical regulatory roles in several intracellular functions. This chapter describes the main enzymes regulating the turnover of each of the seven PIs in mammalian cells and introduces to some of their intracellular functions and to some evidences of their involvement in human diseases. Due to the complex interrelation between the distinct PIs and the plethora of functions that they can regulate inside a cell, this chapter is not meant to be a comprehensive coverage of all aspects of PI signalling but rather an introduction to this complex signalling field. For more details of their regulation/functions and extensive description of their intracellular roles, more detailed reviews are suggested on each single topic.
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Affiliation(s)
- Tania Maffucci
- Centre for Diabetes, Blizard Institute, Inositide Signalling Group, Queen Mary University of London, Barts and The London School of Medicine and Dentistry, UK.
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109
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Abstract
PIKfyve, a phosphoinositide 5-kinase synthesizing PtdIns(3,5)P₂ and PtdIns5P in a cellular context, belongs to an evolutionarily ancient gene family of PtdIns(3,5)P₂-synthesizing enzymes that, except for plants, are products of a single-copy gene across species. In the dozen years after its discovery, enormous progress has been made in characterizing the numerous PIKfyve cellular functions and the regulatory mechanisms that govern these functions. It became clear that PIKfyve does not act alone but, rather, it engages the scaffolding regulator ArPIKfyve and the phosphatase Sac3 to make a multiprotein "PAS" complex, so called for the first letters of the protein names. This complex relays antagonistic signals, one for synthesis, another for turnover of PtdIns(3,5)P₂, whose dysregulated coordination is linked to several human diseases. The physiological significance for each protein in the PAS complex is underscored by the early lethality of the mouse models with disruption in any of the three genes. This chapter summarizes our current knowledge of the diverse and complex functionality of PIKfyve and PtdIns(3,5)P₂/PtdIns5P products with particular highlights on recent discoveries of inherited or somatic mutations in PIKfyve and Sac3 linked to human disorders.
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Affiliation(s)
- Assia Shisheva
- Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan 48201, USA.
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110
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Current world literature. Curr Opin Organ Transplant 2011; 16:650-60. [PMID: 22068023 DOI: 10.1097/mot.0b013e32834dd969] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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111
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Mazza S, Maffucci T. Class II phosphoinositide 3-kinase C2alpha: what we learned so far. INTERNATIONAL JOURNAL OF BIOCHEMISTRY AND MOLECULAR BIOLOGY 2011; 2:168-182. [PMID: 21968800 PMCID: PMC3180093] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 04/13/2011] [Accepted: 04/20/2011] [Indexed: 05/31/2023]
Abstract
More than fifteen years after the first identification of a class II isoform of phosphoinositide 3-kinase (PI3K) in Drosophila melanoǵaster this subfamily remains the most enigmatic among all PI3Ks. What are the functions of these enzymes? What are their mechanisms of activation? Which downstream effectors are specifically regulated by these isoforms? Are class I and class II PI3Ks redundant or do they control different intracellular processes? And, more important, do class II PI3Ks have a role in human diseases? The recent increased interest on class II PI3Ks has started providing some answers to these questions but still a lot needs to be done to completely uncover the contribution of these enzymes to physiological processes and possibly to pathological conditions. Here we will summarise the recent findings on the alpha isoform of mammalian class II PI3Ks (PI3K-C2α ) and we will discuss the potential involvement of this enzyme in human diseases.
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Affiliation(s)
- Simona Mazza
- Queen Mary University of London, Barts and The London School of Medicine and Dentistry, Blizard Institute of Cell and Molecular Science, Centre for Diabetes Inositide Signalling Group, London El 2AT UK
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