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Lipid transfer proteins and the tuning of compartmental identity in the Golgi apparatus. Chem Phys Lipids 2016; 200:42-61. [DOI: 10.1016/j.chemphyslip.2016.06.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2016] [Revised: 06/21/2016] [Accepted: 06/22/2016] [Indexed: 11/23/2022]
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52
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Epand RM. Features of the Phosphatidylinositol Cycle and its Role in Signal Transduction. J Membr Biol 2016; 250:353-366. [PMID: 27278236 DOI: 10.1007/s00232-016-9909-y] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Accepted: 05/26/2016] [Indexed: 01/03/2023]
Abstract
The phosphatidylinositol cycle (PI-cycle) has a central role in cell signaling. It is the major pathway for the synthesis of phosphatidylinositol and its phosphorylated forms. In addition, some lipid intermediates of the PI-cycle, including diacylglycerol and phosphatidic acid, are also important lipid signaling agents. The PI-cycle has some features that are important for the understanding of its role in the cell. As a cycle, the intermediates will be regenerated. The PI-cycle requires a large amount of metabolic energy. There are different steps of the cycle that occur in two different membranes, the plasma membrane and the endoplasmic reticulum. In order to complete the PI-cycle lipid must be transferred between the two membranes. The role of the Nir proteins in the process has recently been elucidated. The lipid intermediates of the PI-cycle are normally highly enriched with 1-stearoyl-2-arachidonoyl molecular species in mammals. This enrichment will be retained as long as the intermediates are segregated from other lipids of the cell. However, there is a significant fraction (>15 %) of lipids in the PI-cycle of normal cells that have other acyl chains. Phosphatidylinositol largely devoid of arachidonoyl chains are found in cancer cells. Phosphatidylinositol species with less unsaturation will not be as readily converted to phosphatidylinositol-3,4,5-trisphosphate, the lipid required for the activation of Akt with resulting effects on cell proliferation. Thus, the cyclical nature of the PI-cycle, its dependence on acyl chain composition and its requirement for lipid transfer between two membranes, explain many of the biological properties of this cycle.
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Affiliation(s)
- Richard M Epand
- Department of Biochemistry and Biomedical Sciences, McMaster University, 1280 Main Street West, Hamilton, ON, L8S 4K1, Canada.
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53
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Abstract
UNLABELLED In neurons, loss of plasma membrane phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] leads to a decrease in exocytosis and changes in electrical excitability. Restoration of PI(4,5)P2 levels after phospholipase C activation is therefore essential for a return to basal neuronal activity. However, the dynamics of phosphoinositide metabolism have not been analyzed in neurons. We measured dynamic changes of PI(4,5)P2, phosphatidylinositol 4-phosphate, diacylglycerol, inositol 1,4,5-trisphosphate, and Ca(2+) upon muscarinic stimulation in sympathetic neurons from adult male Sprague-Dawley rats with electrophysiological and optical approaches. We used this kinetic information to develop a quantitative description of neuronal phosphoinositide metabolism. The measurements and analysis show and explain faster synthesis of PI(4,5)P2 in sympathetic neurons than in electrically nonexcitable tsA201 cells. They can be used to understand dynamic effects of receptor-mediated phospholipase C activation on excitability and other PI(4,5)P2-dependent processes in neurons. SIGNIFICANCE STATEMENT Phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] is a minor phospholipid in the cytoplasmic leaflet of the plasma membrane. Depletion of PI(4,5)P2 via phospholipase C-mediated hydrolysis leads to a decrease in exocytosis and alters electrical excitability in neurons. Restoration of PI(4,5)P2 is essential for a return to basal neuronal activity. However, the dynamics of phosphoinositide metabolism have not been analyzed in neurons. We studied the dynamics of phosphoinositide metabolism in sympathetic neurons upon muscarinic stimulation and used the kinetic information to develop a quantitative description of neuronal phosphoinositide metabolism. The measurements and analysis show a several-fold faster synthesis of PI(4,5)P2 in sympathetic neurons than in an electrically nonexcitable cell line, and provide a framework for future studies of PI(4,5)P2-dependent processes in neurons.
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54
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Kiełbowicz-Matuk A, Banachowicz E, Turska-Tarska A, Rey P, Rorat T. Expression and characterization of a barley phosphatidylinositol transfer protein structurally homologous to the yeast Sec14p protein. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2016; 246:98-111. [PMID: 26993240 DOI: 10.1016/j.plantsci.2016.02.014] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Revised: 02/16/2016] [Accepted: 02/20/2016] [Indexed: 06/05/2023]
Abstract
Phosphatidylinositol transfer proteins (PITPs) include a large group of proteins implicated in the non-vesicular traffic of phosphatidylinositol (PI) between membranes. In yeast, the structure and function of the PITP Sec14-p protein have been well characterized. In contrast, the knowledge on plant PITP proteins is very scarce. In this work, we characterized a novel type of PITP protein in barley named HvSec14p and related to the yeast Sec14-p protein. Our data reveal that HvSec14p consists of only the Sec14p-domain structurally homologous to the yeast phosphoinositide binding domain. We show that HvSec14p expression is up-regulated at both transcript and protein levels at specific stages of development during seed formation and germination, and in leaves of a drought-tolerant barley genotype under osmotic constraints. Modeling analyses of the protein three-dimensional structure revealed its capacity to dock the phosphoinositides, PtdIns(3)P, PtdIns(4)P, PtdIns(5)P and PtdIns(3,5)P2. Consistently, the recombinant HvSec14p protein is able to bind in vitro most PIP types, the highest affinity being observed with PtdIns(3,5)P2. Based on the high gene expression at specific developmental stages and in drought-tolerant barley genotypes, we propose that HvSec14p plays essential roles in the biogenesis of membranes in expanding cells and in their preservation under osmotic stress conditions.
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Affiliation(s)
| | - Ewa Banachowicz
- Molecular Biophysics Department, Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań, Poland.
| | - Anna Turska-Tarska
- Institute of Plant Genetics, Polish Academy of Sciences, Strzeszyńska 34, 60-479 Poznań, Poland.
| | - Pascal Rey
- CEA, DSV, IBEB, Laboratoire d'Ecophysiologie Moléculaire des Plantes, Saint-Paul-lez-Durance, F-13108, France; CNRS, UMR 7265 Biologie Végétale & Microbiologie Environnementale, Saint-Paul-lez-Durance, F-13108, France; Aix-Marseille Université, Saint-Paul-lez-Durance, F-13108, France.
| | - Tadeusz Rorat
- Institute of Plant Genetics, Polish Academy of Sciences, Strzeszyńska 34, 60-479 Poznań, Poland.
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55
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Identification of 42 Genes Linked to Stage II Colorectal Cancer Metastatic Relapse. Int J Mol Sci 2016; 17:ijms17050598. [PMID: 27136531 PMCID: PMC4881437 DOI: 10.3390/ijms17050598] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2016] [Revised: 04/11/2016] [Accepted: 04/12/2016] [Indexed: 12/19/2022] Open
Abstract
Colorectal cancer (CRC) is one of the leading causes of cancer mortality. Metastasis remains the primary cause of CRC death. Predicting the possibility of metastatic relapse in early-stage CRC is of paramount importance to target therapy for patients who really need it and spare those with low-potential of metastasis. Ninety-six stage II CRC cases were stratified using high-resolution array comparative genomic hybridization (aCGH) data based on a predictive survival algorithm and supervised clustering. All genes included within the resultant copy number aberrations were each interrogated independently at mRNA level using CRC expression datasets available from public repositories, which included 1820 colon cancers, and 167 normal colon tissues. Reduced mRNA expression driven by copy number losses and increased expression driven by copy number gains revealed 42 altered transcripts (29 reduced and 13 increased transcripts) associated with metastatic relapse, short disease-free or overall survival, and/or epithelial to mesenchymal transition (EMT). Resultant genes were classified based on gene ontology (GO), which identified four functional enrichment groups involved in growth regulation, genomic integrity, metabolism, and signal transduction pathways. The identified 42 genes may be useful for predicting metastatic relapse in stage II CRC. Further studies are necessary to validate these findings.
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56
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New molecular mechanisms of inter-organelle lipid transport. Biochem Soc Trans 2016; 44:486-92. [DOI: 10.1042/bst20150265] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Indexed: 12/19/2022]
Abstract
Lipids are precisely distributed in cell membranes, along with associated proteins defining organelle identity. Because the major cellular lipid factory is the endoplasmic reticulum (ER), a key issue is to understand how various lipids are subsequently delivered to other compartments by vesicular and non-vesicular transport pathways. Efforts are currently made to decipher how lipid transfer proteins (LTPs) work either across long distances or confined to membrane contact sites (MCSs) where two organelles are at close proximity. Recent findings reveal that proteins of the oxysterol-binding protein related-proteins (ORP)/oxysterol-binding homology (Osh) family are not all just sterol transporters/sensors: some can bind either phosphatidylinositol 4-phosphate (PtdIns(4)P) and sterol or PtdIns(4)P and phosphatidylserine (PS), exchange these lipids between membranes, and thereby use phosphoinositide metabolism to create cellular lipid gradients. Lipid exchange is likely a widespread mechanism also utilized by other LTPs to efficiently trade lipids between organelle membranes. Finally, the discovery of more proteins bearing a lipid-binding module (SMP or START-like domain) raises new questions on how lipids are conveyed in cells and how the activities of different LTPs are coordinated.
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57
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Halberg N, Sengelaub CA, Navrazhina K, Molina H, Uryu K, Tavazoie SF. PITPNC1 Recruits RAB1B to the Golgi Network to Drive Malignant Secretion. Cancer Cell 2016; 29:339-353. [PMID: 26977884 PMCID: PMC5300038 DOI: 10.1016/j.ccell.2016.02.013] [Citation(s) in RCA: 95] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Revised: 08/19/2015] [Accepted: 02/18/2016] [Indexed: 01/07/2023]
Abstract
Enhanced secretion of tumorigenic effector proteins is a feature of malignant cells. The molecular mechanisms underlying this feature are poorly defined. We identify PITPNC1 as a gene amplified in a large fraction of human breast cancer and overexpressed in metastatic breast, melanoma, and colon cancers. Biochemical, molecular, and cell-biological studies reveal that PITPNC1 promotes malignant secretion by binding Golgi-resident PI4P and localizing RAB1B to the Golgi. RAB1B localization to the Golgi allows for the recruitment of GOLPH3, which facilitates Golgi extension and enhanced vesicular release. PITPNC1-mediated vesicular release drives metastasis by increasing the secretion of pro-invasive and pro-angiogenic mediators HTRA1, MMP1, FAM3C, PDGFA, and ADAM10. We establish PITPNC1 as a PI4P-binding protein that enhances vesicular secretion capacity in malignancy.
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Affiliation(s)
- Nils Halberg
- Laboratory of Systems Cancer Biology, Rockefeller University, Box 16, 1230 York Avenue, New York, NY 10065, USA; Department of Biomedicine, University of Bergen, Jonas Liesvej 91, 5020 Bergen, Norway.
| | - Caitlin A Sengelaub
- Laboratory of Systems Cancer Biology, Rockefeller University, Box 16, 1230 York Avenue, New York, NY 10065, USA
| | - Kristina Navrazhina
- Laboratory of Systems Cancer Biology, Rockefeller University, Box 16, 1230 York Avenue, New York, NY 10065, USA
| | - Henrik Molina
- Laboratory of Systems Cancer Biology, Rockefeller University, Box 16, 1230 York Avenue, New York, NY 10065, USA
| | - Kunihiro Uryu
- Laboratory of Systems Cancer Biology, Rockefeller University, Box 16, 1230 York Avenue, New York, NY 10065, USA
| | - Sohail F Tavazoie
- Laboratory of Systems Cancer Biology, Rockefeller University, Box 16, 1230 York Avenue, New York, NY 10065, USA.
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58
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Levine TP, Patel S. Signalling at membrane contact sites: two membranes come together to handle second messengers. Curr Opin Cell Biol 2016; 39:77-83. [PMID: 26922871 DOI: 10.1016/j.ceb.2016.02.011] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Revised: 02/02/2016] [Accepted: 02/04/2016] [Indexed: 12/22/2022]
Abstract
It is now clear that many intracellular signals result from multiple membrane-bound compartments acting in concert. Membrane contact sites, regions of close apposition between organelles, have emerged as major points of convergence during signalling, as these are places where material is exchanged. The material exchanged can be either water-insoluble molecules such as membrane lipids that are passed directly between organelles, or ions such as Ca(2+). Here we highlight new insights into the role of contacts in signalling by second messengers, including lipid traffic that underpins re-generation of IP3, the regulation of NAADP and store-operated Ca(2+) signals, and possible involvement in cyclic AMP signalling.
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Affiliation(s)
- Tim P Levine
- UCL Institute of Ophthalmology, London EC1V 9EL, UK.
| | - Sandip Patel
- Department of Cell and Developmental Biology, University College London, London WC1E 6BT, UK.
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59
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Chang CL, Liou J. Homeostatic regulation of the PI(4,5)P2-Ca(2+) signaling system at ER-PM junctions. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1861:862-873. [PMID: 26924250 DOI: 10.1016/j.bbalip.2016.02.015] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2015] [Revised: 02/17/2016] [Accepted: 02/19/2016] [Indexed: 10/22/2022]
Abstract
The phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2)-Ca(2+) signaling system is important for cell activation in response to various extracellular stimuli. This signaling system is initiated by receptor-induced hydrolysis of PI(4,5)P2 in the plasma membrane (PM) to generate the soluble second messenger inositol 1,4,5-trisphosphate (IP3). IP3 subsequently triggers the release of Ca(2+) from the endoplasmic reticulum (ER) store to the cytosol to activate Ca(2+)-mediated responses, such as secretion and proliferation. The consumed PM PI(4,5)P2 and ER Ca(2+) must be quickly restored to sustain signaling responses, and to maintain the homeostasis of PI(4,5)P2 and Ca(2+). Since phosphatidylinositol (PI), the precursor lipid for PM PI(4,5)P2, is synthesized in the ER membrane, and a Ca(2+) influx across the PM is required to refill the ER Ca(2+) store, efficient communications between the ER and the PM are critical for the homeostatic regulation of the PI(4,5)P2-Ca(2+) signaling system. This review describes the major findings that established the framework of the PI(4,5)P2-Ca(2+) signaling system, and recent discoveries on feedback control mechanisms at ER-PM junctions that sustain the PI(4,5)P2-Ca(2+) signaling system. Particular emphasis is placed on the characterization of ER-PM junctions where efficient communications between the ER and the PM occur, and the activation mechanisms of proteins that dynamically localize to ER-PM junctions to provide the feedback control during PI(4,5)P2-Ca(2+) signaling, including the ER Ca(2+) sensor STIM1, the extended synaptotagmin E-Syt1, and the PI transfer protein Nir2. This article is part of a Special Issue entitled: The cellular lipid landscape edited by Tim P. Levine and Anant K. Menon.
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Affiliation(s)
- Chi-Lun Chang
- Department of Physiology, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Jen Liou
- Department of Physiology, UT Southwestern Medical Center, Dallas, TX 75390, USA.
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60
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RdgBα reciprocally transfers PA and PI at ER–PM contact sites to maintain PI(4,5)P2 homoeostasis during phospholipase C signalling in Drosophila photoreceptors. Biochem Soc Trans 2016; 44:286-92. [DOI: 10.1042/bst20150228] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Phosphatidylinositol (PI) is the precursor lipid for the synthesis of PI 4,5-bisphosphate [PI(4,5)P2] at the plasma membrane (PM) and is sequentially phosphorylated by the lipid kinases, PI 4-kinase and phosphatidylinositol 4-phosphate (PI4P)-5-kinase. Receptor-mediated hydrolysis of PI(4,5)P2 takes place at the PM but PI resynthesis occurs at the endoplasmic reticulum (ER). Thus PI(4,5)P2 resynthesis requires the reciprocal transport of two key intermediates, phosphatidic acid (PA) and PI between the ER and the PM. PI transfer proteins (PITPs), defined by the presence of the PITP domain, can facilitate lipid transfer between membranes; the PITP domain comprises a hydrophobic cavity with dual specificity but accommodates a single phospholipid molecule. The class II PITP, retinal degeneration type B (RdgB)α is a multi-domain protein and its PITP domain can bind and transfer PI and PA. In Drosophila photoreceptors, a well-defined G-protein-coupled phospholipase Cβ (PLCβ) signalling pathway, phototransduction defects resulting from loss of RdgBα can be rescued by expression of the PITP domain provided it is competent for both PI and PA transfer. We propose that RdgBα proteins maintain PI(4,5)P2 homoeostasis after PLC activation by facilitating the reciprocal transport of PA and PI at ER–PM membrane contact sites.
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61
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Yadav S, Garner K, Georgiev P, Li M, Gomez-Espinosa E, Panda A, Mathre S, Okkenhaug H, Cockcroft S, Raghu P. RDGBα, a PtdIns-PtdOH transfer protein, regulates G-protein-coupled PtdIns(4,5)P2 signalling during Drosophila phototransduction. J Cell Sci 2015. [PMID: 26203165 PMCID: PMC4582195 DOI: 10.1242/jcs.173476] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Many membrane receptors activate phospholipase C (PLC) during signalling, triggering changes in the levels of several plasma membrane lipids including phosphatidylinositol (PtdIns), phosphatidic acid (PtdOH) and phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2]. It is widely believed that exchange of lipids between the plasma membrane and endoplasmic reticulum (ER) is required to restore lipid homeostasis during PLC signalling, yet the mechanism remains unresolved. RDGBα (hereafter RDGB) is a multi-domain protein with a PtdIns transfer protein (PITP) domain (RDGB-PITPd). We find that, in vitro, the RDGB-PITPd binds and transfers both PtdOH and PtdIns. In Drosophila photoreceptors, which experience high rates of PLC activity, RDGB function is essential for phototransduction. We show that binding of PtdIns to RDGB-PITPd is essential for normal phototransduction; however, this property is insufficient to explain the in vivo function because another Drosophila PITP (encoded by vib) that also binds PtdIns cannot rescue the phenotypes of RDGB deletion. In RDGB mutants, PtdIns(4,5)P2 resynthesis at the plasma membrane following PLC activation is delayed and PtdOH levels elevate. Thus RDGB couples the turnover of both PtdIns and PtdOH, key lipid intermediates during G-protein-coupled PtdIns(4,5)P2 turnover.
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Affiliation(s)
- Shweta Yadav
- National Centre for Biological Sciences, TIFR-GKVK Campus, Bellary Road, Bangalore, Karnataka 560065, India
| | - Kathryn Garner
- Department of Neuroscience, Physiology and Pharmacology, University College, London WC1E 6JJ, UK
| | - Plamen Georgiev
- Inositide Laboratory, Babraham Institute, Cambridge CB22 3AT, UK
| | - Michelle Li
- Department of Neuroscience, Physiology and Pharmacology, University College, London WC1E 6JJ, UK
| | - Evelyn Gomez-Espinosa
- Department of Neuroscience, Physiology and Pharmacology, University College, London WC1E 6JJ, UK
| | - Aniruddha Panda
- National Centre for Biological Sciences, TIFR-GKVK Campus, Bellary Road, Bangalore, Karnataka 560065, India Manipal University, Madhav Nagar, Manipal, Karnataka 576104, India
| | - Swarna Mathre
- National Centre for Biological Sciences, TIFR-GKVK Campus, Bellary Road, Bangalore, Karnataka 560065, India Manipal University, Madhav Nagar, Manipal, Karnataka 576104, India
| | | | - Shamshad Cockcroft
- Department of Neuroscience, Physiology and Pharmacology, University College, London WC1E 6JJ, UK
| | - Padinjat Raghu
- National Centre for Biological Sciences, TIFR-GKVK Campus, Bellary Road, Bangalore, Karnataka 560065, India Inositide Laboratory, Babraham Institute, Cambridge CB22 3AT, UK
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62
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Grabon A, Khan D, Bankaitis VA. Phosphatidylinositol transfer proteins and instructive regulation of lipid kinase biology. BIOCHIMICA ET BIOPHYSICA ACTA 2015; 1851:724-35. [PMID: 25592381 PMCID: PMC5221696 DOI: 10.1016/j.bbalip.2014.12.011] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2014] [Revised: 11/21/2014] [Accepted: 12/16/2014] [Indexed: 11/25/2022]
Abstract
Phosphatidylinositol is a metabolic precursor of phosphoinositides and soluble inositol phosphates. Both sets of molecules represent versatile intracellular chemical signals in eukaryotes. While much effort has been invested in understanding the enzymes that produce and consume these molecules, central aspects for how phosphoinositide production is controlled and functionally partitioned remain unresolved and largely unappreciated. It is in this regard that phosphatidylinositol (PtdIns) transfer proteins (PITPs) are emerging as central regulators of the functional channeling of phosphoinositide pools produced on demand for specific signaling purposes. The physiological significance of these proteins is amply demonstrated by the consequences that accompany deficits in individual PITPs. Although the biological problem is fascinating, and of direct relevance to disease, PITPs remain largely uncharacterized. Herein, we discuss our perspectives regarding what is known about how PITPs work as molecules, and highlight progress in our understanding of how PITPs are integrated into cellular physiology. This article is part of a Special Issue entitled Phosphoinositides.
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Affiliation(s)
- Aby Grabon
- Department of Molecular & Cellular Medicine, Texas A&M Health Science Center, College Station, TX 77843-1114, USA
| | - Danish Khan
- Department of Biochemistry & Biophysics, Texas A&M University, College Station, TX 77843-2128, USA
| | - Vytas A Bankaitis
- Department of Molecular & Cellular Medicine, Texas A&M Health Science Center, College Station, TX 77843-1114, USA; Department of Biochemistry & Biophysics, Texas A&M University, College Station, TX 77843-2128, USA.
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63
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Kim YJ, Guzman-Hernandez ML, Wisniewski E, Balla T. Phosphatidylinositol-Phosphatidic Acid Exchange by Nir2 at ER-PM Contact Sites Maintains Phosphoinositide Signaling Competence. Dev Cell 2015; 33:549-61. [PMID: 26028218 DOI: 10.1016/j.devcel.2015.04.028] [Citation(s) in RCA: 170] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Revised: 03/20/2015] [Accepted: 04/28/2015] [Indexed: 11/30/2022]
Abstract
Sustained agonist-induced production of the second messengers InsP3 and diacylglycerol requires steady delivery of phosphatidylinositol (PtdIns) from its site of synthesis in the ER to the plasma membrane (PM) to maintain PtdIns(4,5)P2 levels. Similarly, phosphatidic acid (PtdOH), generated from diacylglycerol in the PM, has to reach the ER for PtdIns resynthesis. Here, we show that the Drosophila RdgB homolog, Nir2, a presumed PtdIns transfer protein, not only transfers PtdIns from the ER to the PM but also transfers PtdOH to the opposite direction at ER-PM contact sites. PtdOH delivery to the ER is impaired in Nir2-depleted cells, leading to limited PtdIns synthesis and ultimately to loss of signaling from phospholipase C-coupled receptors. These studies reveal a unique feature of Nir2, namely its ability to serve as a highly localized lipid exchanger that ensures that PtdIns synthesis is matched with PtdIns(4,5)P2 utilization so that cells maintain their signaling competence.
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Affiliation(s)
- Yeun Ju Kim
- Section on Molecular Signal Transduction, Program for Developmental Neuroscience, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Maria-Luisa Guzman-Hernandez
- Section on Molecular Signal Transduction, Program for Developmental Neuroscience, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Eva Wisniewski
- Section on Molecular Signal Transduction, Program for Developmental Neuroscience, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Tamas Balla
- Section on Molecular Signal Transduction, Program for Developmental Neuroscience, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
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64
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Chang CL, Liou J. Phosphatidylinositol 4,5-Bisphosphate Homeostasis Regulated by Nir2 and Nir3 Proteins at Endoplasmic Reticulum-Plasma Membrane Junctions. J Biol Chem 2015; 290:14289-301. [PMID: 25887399 DOI: 10.1074/jbc.m114.621375] [Citation(s) in RCA: 99] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2014] [Indexed: 11/06/2022] Open
Abstract
Phosphatidylinositol (PI) 4,5-bisphosphate (PIP2) at the plasma membrane (PM) constitutively controls many cellular functions, and its hydrolysis via receptor stimulation governs cell signaling. The PI transfer protein Nir2 is essential for replenishing PM PIP2 following receptor-induced hydrolysis, but key mechanistic aspects of this process remain elusive. Here, we demonstrate that PI at the membrane of the endoplasmic reticulum (ER) is required for the rapid replenishment of PM PIP2 mediated by Nir2. Nir2 detects PIP2 hydrolysis and translocates to ER-PM junctions via binding to phosphatidic acid. With distinct phosphatidic acid binding abilities and PI transfer protein activities, Nir2 and its homolog Nir3 differentially regulate PIP2 homeostasis in cells during intense receptor stimulation and in the resting state, respectively. Our study reveals that Nir2 and Nir3 work in tandem to achieve different levels of feedback based on the consumption of PM PIP2 and function at ER-PM junctions to mediate nonvesicular lipid transport between the ER and the PM.
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Affiliation(s)
- Chi-Lun Chang
- From the Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Jen Liou
- From the Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390
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65
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Un K, Sakai-Kato K, Kawanishi T, Okuda H, Goda Y. Effects of Liposomal Phospholipids and Lipid Transport-Related Protein on the Intracellular Fate of Encapsulated Doxorubicin. Mol Pharm 2014; 11:560-7. [DOI: 10.1021/mp400505a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Affiliation(s)
- Keita Un
- Division
of Drugs, National Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya-ku, Tokyo 158-8501, Japan
| | - Kumiko Sakai-Kato
- Division
of Drugs, National Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya-ku, Tokyo 158-8501, Japan
| | - Toru Kawanishi
- National Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya-ku, Tokyo 158-8501, Japan
| | - Haruhiro Okuda
- National Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya-ku, Tokyo 158-8501, Japan
| | - Yukihiro Goda
- Division
of Drugs, National Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya-ku, Tokyo 158-8501, Japan
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Cockcroft S, Garner K. Potential role for phosphatidylinositol transfer protein (PITP) family in lipid transfer during phospholipase C signalling. Adv Biol Regul 2013; 53:280-291. [PMID: 23916246 DOI: 10.1016/j.jbior.2013.07.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2013] [Revised: 07/11/2013] [Accepted: 07/12/2013] [Indexed: 06/02/2023]
Abstract
The hallmark of mammalian phosphatidylinositol transfer proteins (PITPs) is to transfer phosphatidylinositol between membrane compartments. In the mammalian genome, there are three genes that code for soluble PITP proteins, PITPα, PITPβ and RdgBβ and two genes that code for membrane-associated multi-domain proteins (RdgBαI and II) containing a PITP domain. PITPα and PITPβ constitute Class I PITPs whilst the RdgB proteins constitute Class II proteins based on sequence analysis. The PITP domain of both Class I and II can sequester one molecule of phosphatidylinositol (PI) in its hydrophobic cavity. Therefore, in principle, PITPs are therefore ideally poised to couple phosphatidylinositol delivery to the PI kinases for substrate provision for phospholipases C during cell activation. Since phosphatidylinositol (4,5)bisphosphate plays critical roles in cells, particularly at the plasma membrane, where it is a substrate for both phospholipase C and phosphoinositide-3-kinases as well as required as an intact lipid to regulate ion channels and the actin cytoskeleton, homeostatic mechanisms to maintain phosphatidylinositol(4,5)bisphosphate levels are vital. To maintain phosphatidylinositol levels, phospholipase C activation inevitably leads to the resynthesis of PI at the endoplasmic reticulum where the enzymes are located. Phosphatidic acid generated at the plasma membrane during phospholipase C activation needs to move to the ER for conversion to PI and here we provide evidence that Class II PITPs are also able to bind and transport phosphatidic acid. Thus RdgB proteins could couple PA and PI transport bidirectionally during phospholipase C signalling.
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Affiliation(s)
- Shamshad Cockcroft
- Dept. of Neuroscience, Physiology and Pharmacology, Division of Biosciences, University College London, London WC1E 6JJ, UK.
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Pencheva N, Tavazoie SF. Control of metastatic progression by microRNA regulatory networks. Nat Cell Biol 2013; 15:546-54. [PMID: 23728460 DOI: 10.1038/ncb2769] [Citation(s) in RCA: 253] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Aberrant microRNA (miRNA) expression is a defining feature of human malignancy. Specific miRNAs have been identified as promoters or suppressors of metastatic progression. miRNAs control metastasis through divergent or convergent regulation of metastatic gene pathways. Some miRNA regulatory networks govern cell-autonomous cancer phenotypes, whereas others modulate the cell-extrinsic composition of the metastatic microenvironment. The use of small RNAs as probes into the molecular and cellular underpinnings of metastasis holds promise for the identification of candidate genes for potential therapeutic intervention.
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Affiliation(s)
- Nora Pencheva
- Laboratory of Systems Cancer Biology, Rockefeller University, New York, New York 10065, USA
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Abstract
Phosphoinositides (PIs) make up only a small fraction of cellular phospholipids, yet they control almost all aspects of a cell's life and death. These lipids gained tremendous research interest as plasma membrane signaling molecules when discovered in the 1970s and 1980s. Research in the last 15 years has added a wide range of biological processes regulated by PIs, turning these lipids into one of the most universal signaling entities in eukaryotic cells. PIs control organelle biology by regulating vesicular trafficking, but they also modulate lipid distribution and metabolism via their close relationship with lipid transfer proteins. PIs regulate ion channels, pumps, and transporters and control both endocytic and exocytic processes. The nuclear phosphoinositides have grown from being an epiphenomenon to a research area of its own. As expected from such pleiotropic regulators, derangements of phosphoinositide metabolism are responsible for a number of human diseases ranging from rare genetic disorders to the most common ones such as cancer, obesity, and diabetes. Moreover, it is increasingly evident that a number of infectious agents hijack the PI regulatory systems of host cells for their intracellular movements, replication, and assembly. As a result, PI converting enzymes began to be noticed by pharmaceutical companies as potential therapeutic targets. This review is an attempt to give an overview of this enormous research field focusing on major developments in diverse areas of basic science linked to cellular physiology and disease.
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Affiliation(s)
- Tamas Balla
- Section on Molecular Signal Transduction, Program for Developmental Neuroscience, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA.
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Kim YJ, Hernandez MLG, Balla T. Inositol lipid regulation of lipid transfer in specialized membrane domains. Trends Cell Biol 2013; 23:270-8. [PMID: 23489878 PMCID: PMC3665726 DOI: 10.1016/j.tcb.2013.01.009] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2012] [Revised: 01/22/2013] [Accepted: 01/31/2013] [Indexed: 11/22/2022]
Abstract
The highly dynamic membranous network of eukaryotic cells allows spatial organization of biochemical reactions to suit the complex metabolic needs of the cell. The unique lipid composition of organelle membranes in the face of dynamic membrane activities assumes that lipid gradients are constantly generated and maintained. Important advances have been made in identifying specialized membrane compartments and lipid transfer mechanisms that are critical for generating and maintaining lipid gradients. Remarkably, one class of minor phospholipids--the phosphoinositides--is emerging as important regulators of these processes. Here, we summarize several lines of research that have led to our current understanding of the connection between phosphoinositides and the transport of structural lipids and offer some thoughts on general principles possibly governing these processes.
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Affiliation(s)
- Yeun Ju Kim
- Section on Molecular Signal Transduction, Program for Developmental Neuroscience, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892
| | - Maria-Luisa Guzman Hernandez
- Section on Molecular Signal Transduction, Program for Developmental Neuroscience, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892
| | - Tamas Balla
- Section on Molecular Signal Transduction, Program for Developmental Neuroscience, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892
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