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Chemical genetic identification of NDR1/2 kinase substrates AAK1 and Rabin8 Uncovers their roles in dendrite arborization and spine development. Neuron 2012; 73:1127-42. [PMID: 22445341 DOI: 10.1016/j.neuron.2012.01.019] [Citation(s) in RCA: 99] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/05/2012] [Indexed: 11/21/2022]
Abstract
Dendrite arborization and synapse formation are essential for wiring the neural circuitry. The evolutionarily conserved NDR1/2 kinase pathway, important for polarized growth from yeast to mammals, controls dendrite growth and morphology in the worm and fly. The function of NDR1/2 in mammalian neurons and their downstream effectors were not known. Here we show that the expression of dominant negative (kinase-dead) NDR1/2 mutants or siRNA increase dendrite length and proximal branching of mammalian pyramidal neurons in cultures and in vivo, whereas the expression of constitutively active NDR1/2 has the opposite effect. Moreover, NDR1/2 contributes to dendritic spine development and excitatory synaptic function. We further employed chemical genetics and identified NDR1/2 substrates in the brain, including two proteins involved in intracellular vesicle trafficking: AAK1 (AP-2 associated kinase) and Rabin8, a GDP/GTP exchange factor (GEF) of Rab8 GTPase. We finally show that AAK1 contributes to dendrite growth regulation, and Rabin8 regulates spine development.
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52
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Jović M, Kean MJ, Szentpetery Z, Polevoy G, Gingras AC, Brill JA, Balla T. Two phosphatidylinositol 4-kinases control lysosomal delivery of the Gaucher disease enzyme, β-glucocerebrosidase. Mol Biol Cell 2012; 23:1533-45. [PMID: 22337770 PMCID: PMC3327330 DOI: 10.1091/mbc.e11-06-0553] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Trafficking of glucocerebrosidase (GBA) enzyme from the endoplasmic reticulum to the lysosome requires lysosomal integral membrane protein type 2 (LIMP-2), which is a receptor for GBA. This study shows that phosphatidylinositol 4-kinase (PI4K) type IIIβ controls the exit of LIMP-2/GBA complex from the Golgi, while PI4KIIα is required for the post-Golgi trafficking of the complex via the late endosomes. Gaucher disease is a lysosomal storage disorder caused by a defect in the degradation of glucosylceramide catalyzed by the lysosomal enzyme β-glucocerebrosidase (GBA). GBA reaches lysosomes via association with its receptor, lysosomal integral membrane protein type 2 (LIMP-2). We found that distinct phosphatidylinositol 4-kinases (PI4Ks) play important roles at multiple steps in the trafficking pathway of the LIMP-2/GBA complex. Acute depletion of phosphatidylinositol 4-phosphate in the Golgi caused accumulation of LIMP-2 in this compartment, and PI4KIIIβ was found to be responsible for controlling the exit of LIMP-2 from the Golgi. In contrast, depletion of PI4KIIα blocked trafficking at a post-Golgi compartment, leading to accumulation of LIMP-2 in enlarged endosomal vesicles. PI4KIIα depletion also caused secretion of missorted GBA into the medium, which was attenuated by limiting LIMP-2/GBA exit from the Golgi by PI4KIIIβ inhibitors. These studies identified PI4KIIIβ and PI4KIIα as important regulators of lysosomal delivery of GBA, revealing a new element of control to sphingolipid homeostasis by phosphoinositides.
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Affiliation(s)
- Marko Jović
- Section on Molecular Signal Transduction, Program for Developmental Neuroscience, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
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53
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Quantification of Signaling Lipids by Nano-Electrospray Ionization Tandem Mass Spectrometry (Nano-ESI MS/MS). Metabolites 2012; 2:57-76. [PMID: 24957368 PMCID: PMC3901191 DOI: 10.3390/metabo2010057] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2011] [Revised: 01/04/2012] [Accepted: 01/06/2012] [Indexed: 01/10/2023] Open
Abstract
Lipids, such as phosphoinositides (PIPs) and diacylglycerol (DAG), are important signaling intermediates involved in cellular processes such as T cell receptor (TCR)-mediated signal transduction. Here we report identification and quantification of PIP, PIP2 and DAG from crude lipid extracts. Capitalizing on the different extraction properties of PIPs and DAGs allowed us to efficiently recover both lipid classes from one sample. Rapid analysis of endogenous signaling molecules was performed by nano-electrospray ionization tandem mass spectrometry (nano-ESI MS/MS), employing lipid class-specific neutral loss and multiple precursor ion scanning for their identification and quantification. Profiling of DAG, PIP and PIP2 molecular species in primary human T cells before and after TCR stimulation resulted in a two-fold increase in DAG levels with a shift towards 1-stearoyl-2-arachidonoyl-DAG in stimulated cells. PIP2 levels were slightly reduced, while PIP levels remained unchanged.
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54
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Abstract
The endo-lysosomal system is an interconnected tubulo-vesicular network that acts as a sorting station to process and distribute internalised cargo. This network accepts cargoes from both the plasma membrane and the biosynthetic pathway, and directs these cargos either towards the lysosome for degradation, the peri-nuclear recycling endosome for return to the cell surface, or to the trans-Golgi network. These intracellular membranes are variously enriched in different phosphoinositides that help to shape compartmental identity. These lipids act to localise a number of phosphoinositide-binding proteins that function as sorting machineries to regulate endosomal cargo sorting. Herein we discuss regulation of these machineries by phosphoinositides and explore how phosphoinositide-switching contributes toward sorting decisions made at this platform.
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Affiliation(s)
- Peter J Cullen
- Henry Wellcome Integrated Signaling Laboratories, School of Biochemistry, Medical Sciences Building, University of Bristol, BS8 1TD, Bristol, United Kingdom,
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55
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Pinke DE, Lee JM. The lipid kinase PI4KIIIβ and the eEF1A2 oncogene co-operate to disrupt three-dimensional in vitro acinar morphogenesis. Exp Cell Res 2011; 317:2503-11. [PMID: 21851817 DOI: 10.1016/j.yexcr.2011.08.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2011] [Revised: 07/29/2011] [Accepted: 08/01/2011] [Indexed: 11/25/2022]
Abstract
The study of in vitro morphogenesis is fundamental to understanding neoplasia since the dysregulation of morphogenic pathways that create multi-cellular organisms is a common hallmark of oncogenesis. The in vitro culture of human breast epithelial cells on reconstituted basement membranes recapitulate some features of in vivo breast development, including the formation of a three-dimensional structure termed an acinus. Importantly, the capacity to disrupt in vitro acinar morphogenesis is a common property of human breast oncogenes. In this report, we find that phosphatidylinositol 4-kinase IIIβ (PI4KIIIβ), a lipid kinase that phosphorylates phosphatidylinositol (PI) to PI(4)P, disrupts in vitro mammary acinar formation. The PI4KIIIβ protein localizes to the basal surface of acini created by human MCF10A cells and ectopic expression of PI4KIIIβ induces multi-acinar devlopment. Furthermore, expression of an oncogenic PI4KIIIβ activator, eEF1A2 (eukaryotic elongation factor 1 alpha 2), phenocopies the PI4KIIIβ multi-acinar phenotype. Ectopic expression of PI4KIIIβ or eEF1A2 alters the localization of PI(4)P and PI(4,5)P(2) within acini, indicating the importance of these lipids in acinar development. Our work shows that PI4KIIIβ, eEF1A2 and PI(4)P likely play an important role in mammary neoplasia and acinar development.
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Affiliation(s)
- Dixie E Pinke
- Department of Biochemistry, University of Ottawa, 451 Smyth Road, Ottawa, Ontario, Canada K1H 8M5
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56
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Abstract
The protein processing and trafficking function of the Golgi is intimately linked to multiple intracellular signaling pathways. Assembly of Golgi trafficking structures and lipid sorting at the Golgi complex is controlled and coordinated by specific phosphoinositide kinases and phosphatases. The intra-Golgi transport machinery is also regulated by kinases belonging to several functionally distinct families, for example, MAP kinase signaling is required for mitotic disassembly of the Golgi. However, the Golgi plays an additional, prominent role in compartmentalizing other signaling cascades that originate at the plasma membrane or at other organelles. This article summarizes recent advances in our understanding of the signaling network that converges at the Golgi.
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Affiliation(s)
- Peter Mayinger
- Division of Nephrology and Hypertension and Department of Cell and Developmental Biology, Oregon Health & Science University, Portland, OR 97239, USA.
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57
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Shen B, Wu N, Yang JM, Gould SJ. Protein targeting to exosomes/microvesicles by plasma membrane anchors. J Biol Chem 2011; 286:14383-95. [PMID: 21300796 PMCID: PMC3077638 DOI: 10.1074/jbc.m110.208660] [Citation(s) in RCA: 206] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2010] [Revised: 01/25/2011] [Indexed: 12/14/2022] Open
Abstract
Animal cells secrete small vesicles, otherwise known as exosomes and microvesicles (EMVs). A short, N-terminal acylation tag can target a highly oligomeric cytoplasmic protein, TyA, into secreted vesicles (Fang, Y., Wu, N., Gan, X., Yan, W., Morell, J. C., and Gould, S. J. (2007) PLoS Biol. 5, 1267-1283). However, it is not clear whether this is true for other membrane anchors or other highly oligomeric, cytoplasmic proteins. We show here that a variety of plasma membrane anchors can target TyA-GFP to sites of vesicle budding and into EMVs, including: (i) a myristoylation tag; (ii) a phosphatidylinositol-(4,5)-bisphosphate (PIP(2))-binding domain; (iii), a phosphatidylinositol-(3,4,5)-trisphosphate-binding domain; (iv) a prenylation/palmitoylation tag, and (v) a type-1 plasma membrane protein, CD43. However, the relative budding efficiency induced by these plasma membrane anchors varied over a 10-fold range, from 100% of control (AcylTyA-GFP) for the myristoylation tag and PIP(2)-binding domain, to one-third or less for the others, respectively. Targeting TyA-GFP to endosome membranes by fusion to a phosphatidylinositol 3-phosphate-binding domain induced only a slight budding of TyA-GFP, ∼2% of control, and no budding was observed when TyA-GFP was targeted to Golgi membranes via a phosphatidylinositol 4-phosphate-binding domain. We also found that a plasma membrane anchor can target two other highly oligomeric, cytoplasmic proteins to EMVs. These observations support the hypothesis that plasma membrane anchors can target highly oligomeric, cytoplasmic proteins to EMVs. Our data also provide additional parallels between EMV biogenesis and retrovirus budding, as the anchors that induced the greatest budding of TyA-GFP are the same as those that mediate retrovirus budding.
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Affiliation(s)
- Beiyi Shen
- From the Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Ning Wu
- From the Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Jr-Ming Yang
- From the Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Stephen J. Gould
- From the Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
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58
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Recruitment and activation of a lipid kinase by hepatitis C virus NS5A is essential for integrity of the membranous replication compartment. Cell Host Microbe 2011; 9:32-45. [PMID: 21238945 DOI: 10.1016/j.chom.2010.12.002] [Citation(s) in RCA: 396] [Impact Index Per Article: 30.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2010] [Revised: 11/12/2010] [Accepted: 12/16/2010] [Indexed: 02/07/2023]
Abstract
Hepatitis C virus (HCV) is a major causative agent of chronic liver disease in humans. To gain insight into host factor requirements for HCV replication, we performed a siRNA screen of the human kinome and identified 13 different kinases, including phosphatidylinositol-4 kinase III alpha (PI4KIIIα), as being required for HCV replication. Consistent with elevated levels of the PI4KIIIα product phosphatidylinositol-4-phosphate (PI4P) detected in HCV-infected cultured hepatocytes and liver tissue from chronic hepatitis C patients, the enzymatic activity of PI4KIIIα was critical for HCV replication. Viral nonstructural protein 5A (NS5A) was found to interact with PI4KIIIα and stimulate its kinase activity. The absence of PI4KIIIα activity induced a dramatic change in the ultrastructural morphology of the membranous HCV replication complex. Our analysis suggests that the direct activation of a lipid kinase by HCV NS5A contributes critically to the integrity of the membranous viral replication complex.
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59
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Goulart L, Rosa e Silva LK, Chiapello L, Silveira C, Crestani J, Masih D, Vainstein MH. Cryptococcus neoformans and Cryptococcus gattii genes preferentially expressed during rat macrophage infection. Med Mycol 2011; 48:932-41. [PMID: 20302549 DOI: 10.3109/13693781003677494] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Cryptococcus neoformans and Cryptococcus gattii are encapsulated yeast agents of cryptococcosis and facultative intracellular pathogens. The interaction of these yeasts with macrophages is essential for containing the infection. However, Cryptococcus spp. overcome this initial host defense barrier using a unique pathogenic strategy involving intracellular replication and cytoplasmic accumulation of polysaccharide-containing vesicles. Here, we employed representational difference analysis (RDA) to identify C. neoformans and C. gattii genes differentially expressed during intracellular growth in rat peritoneal macrophages. The upregulated transcripts of C. neoformans during macrophage interaction were related to ATP-binding cassette (ABC) transporters, intra-golgi transport, chaperone activity, ribosomal maintenance, NAD metabolism, histone methylation, stress response, and monosaccharide metabolism. In contrast, with C. gattii, upregulated genes were associated with cell growth, aerobic respiration, protein binding, microtubule nucleation, monosaccharides and nitrogen metabolism, inositol or phosphatidylinositol phosphatase activity, cellular signaling, and stress response. Our findings reveal new genes that may be necessary for the intracellular parasitism of C. neoformans and C. gattii.
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Affiliation(s)
- Letícia Goulart
- Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
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60
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Anitei M, Wassmer T, Stange C, Hoflack B. Bidirectional transport between the trans-Golgi network and the endosomal system. Mol Membr Biol 2010; 27:443-56. [DOI: 10.3109/09687688.2010.522601] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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61
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Acute manipulation of Golgi phosphoinositides to assess their importance in cellular trafficking and signaling. Proc Natl Acad Sci U S A 2010; 107:8225-30. [PMID: 20404150 DOI: 10.1073/pnas.1000157107] [Citation(s) in RCA: 133] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Phosphoinositides are essential lipid regulators of trafficking and signaling pathways of all eukaryotic cells. Phosphatidylinositol 4-phosphate (PtdIns4P) is an intermediate in the synthesis of several important phosphoinositide species but also serves as a regulatory molecule in its own right. Phosphatidylinositol 4-kinases are most abundant in the Golgi but are also found in the plasma membrane and in endocytic compartments. To investigate the role of Golgi PtdIns4P in orchestrating trafficking events, we used a unique drug-inducible molecular approach to rapidly deplete PtdIns4P from Golgi membranes by a recruitable Sac1 phosphatase enzyme. The utility of the system was shown by the rapid loss of Golgi localization of PH domains known to bind PtdIns4P after Sac1 recruitment to the Golgi. Acute PtdIns4P depletion prevented the exit of cargo from the Golgi destined to both the plasma membrane and the late endosomes and led to the loss of some but not all clathrin adaptors from the Golgi membrane. Rapid PtdIns4P depletion in the Golgi also impaired but did not eliminate the replenishment of the plasma membrane PtdIns(4,5)P(2) during phospholipase C activation revealing a hitherto unrecognized contribution of Golgi PtdIns4P to this process. This unique approach will allow further studies on the role of phosphoinositides in endocytic compartments that have evaded detection using the conventional long-term manipulations of inositide kinase and phosphatase activities.
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62
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Minogue S, Chu KME, Westover EJ, Covey DF, Hsuan JJ, Waugh MG. Relationship between phosphatidylinositol 4-phosphate synthesis, membrane organization, and lateral diffusion of PI4KIIalpha at the trans-Golgi network. J Lipid Res 2010; 51:2314-24. [PMID: 20388919 DOI: 10.1194/jlr.m005751] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Type II phosphatidylinositol 4-kinase IIalpha (PI4KIIalpha) is the dominant phosphatidylinositol kinase activity measured in mammalian cells and has important functions in intracellular vesicular trafficking. Recently PI4KIIalpha has been shown to have important roles in neuronal survival and tumorigenesis. This study focuses on the relationship between membrane cholesterol levels, phosphatidylinositol 4-phosphate (PI4P) synthesis, and PI4KIIalpha mobility. Enzyme kinetic measurements, sterol substitution studies, and membrane fragmentation analyses all revealed that cholesterol regulates PI4KIIalpha activity indirectly through effects on membrane structure. In particular, we found that cholesterol levels determined the distribution of PI4KIIalpha to biophysically distinct membrane domains. Imaging studies on cells expressing enhanced green fluorescent protein (eGFP)-tagged PI4KIIalpha demonstrated that cholesterol depletion resulted in morphological changes to the juxtanuclear membrane pool of the enzyme. Lateral membrane diffusion of eGFP-PI4KIIalpha was assessed by fluorescence recovery after photobleaching (FRAP) experiments, which revealed the existence of both mobile and immobile pools of the enzyme. Sterol depletion decreased the size of the mobile pool of PI4KIIalpha. Further measurements revealed that the reduction in the mobile fraction of PI4KIIalpha correlated with a loss of trans-Golgi network (TGN) membrane connectivity. We conclude that cholesterol modulates PI4P synthesis through effects on membrane organization and enzyme diffusion.
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Affiliation(s)
- Shane Minogue
- Department of Inflammation, Division of Medicine, University College London, Centre for Molecular Cell Biology, London, United Kingdom
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63
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Ogiso H, Taguchi R. Reversed-phase LC/MS method for polyphosphoinositide analyses: changes in molecular species levels during epidermal growth factor activation in A431 cells. Anal Chem 2009; 80:9226-32. [PMID: 19551943 DOI: 10.1021/ac801451p] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
In studies on lipid metabolomics, liquid chromatography/ mass spectrometry (LC/MS) is a robust and popular technique. Although effective reversed-phase (RP) LC/ MS methods enabling the separation of phospholipid molecular species have been developed, RPLC methods to analyze phosphatidylinositol phosphates (PIPs) have not been reported. In this study, we developed conditions suitable for PIP analysis. Coupled with (diethylamino)ethyl (DEAE)-cellulose pretreatment, at least 1 pmol each of phosphatidylinositol monophosphates (PIP1), bisphosphates (PIP2), and triphosphates standards per approximately 6 x 10(6) cultured cells could be measured. Using these methods, we detected elevated concentrations of more than 12 PIP1 species in epidermal growth factor (EGF)-stimulated A431 cells, a human epidermoid carcinoma cell line. The PIP2 species detected were not elevated after stimulation. We also detected EGF-induced increases in the levels of several phosphatidic acid species using another set of methods. Our method sensitively determined PIPs within a biological sample and is thus suitable for analysis of phoisphoiniositide metabolism.
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Affiliation(s)
- Hideo Ogiso
- Department of Metabolome, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
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64
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Abstract
Phosphoinositides constitute only a small fraction of cellular phospholipids, yet their importance in the regulation of cellular functions can hardly be overstated. The rapid metabolic response of phosphoinositides after stimulation of certain cell surface receptors was the first indication that these lipids could serve as regulatory molecules. These early observations opened research areas that ultimately clarified the plasma membrane role of phosphoinositides in Ca(2+) signaling. However, research of the last 10 years has revealed a much broader range of processes dependent on phosphoinositides. These lipids control organelle biology by regulating vesicular trafficking, and they modulate lipid distribution and metabolism more generally via their close relationship with lipid transfer proteins. Phosphoinositides also regulate ion channels, pumps, and transporters as well as both endocytic and exocytic processes. The significance of phosphoinositides found within the nucleus is still poorly understood, and a whole new research concerns the highly phosphorylated inositols that also appear to control multiple nuclear processes. The expansion of research and interest in phosphoinositides naturally created a demand for new approaches to determine where, within the cell, these lipids exert their effects. Imaging of phosphoinositide dynamics within live cells has become a standard cell biological method. These new tools not only helped us localize phosphoinositides within the cell but also taught us how tightly phosphoinositide control can be linked with distinct effector protein complexes. The recent progress allows us to understand the underlying causes of certain human diseases and design new strategies for therapeutic interventions.
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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, USA.
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65
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Qin Y, Li L, Pan W, Wu D. Regulation of phosphatidylinositol kinases and metabolism by Wnt3a and Dvl. J Biol Chem 2009; 284:22544-8. [PMID: 19561074 DOI: 10.1074/jbc.m109.014399] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Wnt signaling plays important roles in various physiological and pathophysiological processes. The pathway that leads to beta-catenin stabilization is initiated by Wnt binding to its cell surface receptors, which induces the formation of phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P(2)) via activation of phosphatidylinositol 4-phosphate 5-kinase (PIP5K) type I. Here, we show that Wnt also stimulated the production of phosphatidylinositol 4-phosphate (PtdIns(4)P), which depended on Frizzled (Fz), Dishevelled (Dvl), and phosphatidylinositol 4-kinase (PI4K) type II alpha in HEK293T cells. Dvl directly interacted with and activated PI4KII alpha by increasing its V(max) for ATP and PtdIns. In addition, Dvl regulated PI4KII alpha and PIP5KI via different domains. Moreover, Dvl, PI4KII alpha, and PIP5KI appeared to form a ternary complex upon Wnt3a stimulation. This complex may allow efficient production of PtdIns(4,5)P(2) from PtdIns, which is far more abundant than PtdIns(4)P in cells. Therefore, this study provides new insights into the mechanism by which Wnt3a regulates the production of PtdIns(4,5)P(2).
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Affiliation(s)
- Yuanbo Qin
- State Key Laboratory of Molecular Biology and Center of Cell Signaling, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
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66
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Jović M, Kieken F, Naslavsky N, Sorgen PL, Caplan S. Eps15 homology domain 1-associated tubules contain phosphatidylinositol-4-phosphate and phosphatidylinositol-(4,5)-bisphosphate and are required for efficient recycling. Mol Biol Cell 2009; 20:2731-43. [PMID: 19369419 DOI: 10.1091/mbc.e08-11-1102] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The C-terminal Eps15 homology domain (EHD) 1/receptor-mediated endocytosis-1 protein regulates recycling of proteins and lipids from the recycling compartment to the plasma membrane. Recent studies have provided insight into the mode by which EHD1-associated tubular membranes are generated and the mechanisms by which EHD1 functions. Despite these advances, the physiological function of these striking EHD1-associated tubular membranes remains unknown. Nuclear magnetic resonance spectroscopy demonstrated that the Eps15 homology (EH) domain of EHD1 binds to phosphoinositides, including phosphatidylinositol-4-phosphate. Herein, we identify phosphatidylinositol-4-phosphate as an essential component of EHD1-associated tubules in vivo. Indeed, an EHD1 EH domain mutant (K483E) that associates exclusively with punctate membranes displayed decreased binding to phosphatidylinositol-4-phosphate and other phosphoinositides. Moreover, we provide evidence that although the tubular membranes to which EHD1 associates may be stabilized and/or enhanced by EHD1 expression, these membranes are, at least in part, pre-existing structures. Finally, to underscore the function of EHD1-containing tubules in vivo, we used a small interfering RNA (siRNA)/rescue assay. On transfection, wild-type, tubule-associated, siRNA-resistant EHD1 rescued transferrin and beta1 integrin recycling defects observed in EHD1-depleted cells, whereas expression of the EHD1 K483E mutant did not. We propose that phosphatidylinositol-4-phosphate is an essential component of EHD1-associated tubules that also contain phosphatidylinositol-(4,5)-bisphosphate and that these structures are required for efficient recycling to the plasma membrane.
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Affiliation(s)
- Marko Jović
- Department of Biochemistry and Molecular Biology, and Eppley Cancer Center, University of Nebraska Medical Center, Omaha, NE 68198-5870, USA
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67
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Zoncu R, Perera RM, Balkin DM, Pirruccello M, Toomre D, De Camilli P. A phosphoinositide switch controls the maturation and signaling properties of APPL endosomes. Cell 2009; 136:1110-21. [PMID: 19303853 DOI: 10.1016/j.cell.2009.01.032] [Citation(s) in RCA: 271] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2008] [Revised: 11/12/2008] [Accepted: 01/06/2009] [Indexed: 01/11/2023]
Abstract
The recent identification of several novel endocytic compartments has challenged our current understanding of the topological and functional organization of the endocytic pathway. Using quantitative single vesicle imaging and acute manipulation of phosphoinositides we show that APPL endosomes, which participate in growth factor receptor trafficking and signaling, represent an early endocytic intermediate common to a subset of clathrin derived endocytic vesicles and macropinosomes. Most APPL endosomes are precursors of classical PI3P positive endosomes, and PI3P plays a critical role in promoting this conversion. Depletion of PI3P causes a striking reversion of Rab5 positive endosomes to the APPL stage, and results in enhanced growth factor signaling. These findings reveal a surprising plasticity of the early endocytic pathway. Importantly, PI3P functions as a switch to dynamically regulate maturation and signaling of APPL endosomes.
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Affiliation(s)
- Roberto Zoncu
- Department of Cell Biology, Kavli Institute for Neuroscience and Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, CT 06510, USA
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68
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McCrea HJ, De Camilli P. Mutations in phosphoinositide metabolizing enzymes and human disease. Physiology (Bethesda) 2009; 24:8-16. [PMID: 19196647 DOI: 10.1152/physiol.00035.2008] [Citation(s) in RCA: 134] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Phosphoinositides are implicated in the regulation of a wide variety of cellular functions. Their importance in cellular and organismal physiology is underscored by the growing number of human diseases linked to perturbation of kinases and phosphatases that catalyze interconversion from one phosphoinositide to another. Many such enzymes are attractive targets for therapeutic interventions. Here, we review diseases linked to inheritable or somatic mutations of these enzymes.
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Affiliation(s)
- Heather J McCrea
- Howard Hughes Medical Institute, Department of Cell Biology, Kavli Institute for Neuroscience, Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, Connecticut, USA
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69
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Luo R, Ha VL, Hayashi R, Randazzo PA. Arf GAP2 is positively regulated by coatomer and cargo. Cell Signal 2009; 21:1169-79. [PMID: 19296914 DOI: 10.1016/j.cellsig.2009.03.006] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2009] [Revised: 03/05/2009] [Accepted: 03/09/2009] [Indexed: 11/19/2022]
Abstract
Arf GAP2 is one of four Arf GAPs that function in the Golgi apparatus. We characterized the kinetics of Arf GAP2 and its regulation. Purified Arf GAP2 had little activity compared to purified Arf GAP1. Of the potential regulators we examined, coatomer had the greatest effect, stimulating activity one to two orders of magnitude. The effect was biphasic, with half-maximal activation observed at 50 nM coatomer and activation peaking at approximately 150 nM coatomer. Activation by coatomer was greater for Arf GAP2 than has been reported for Arf GAP1. The effects of phosphoinositides and changes in vesicle curvature on GAP activity were small compared to coatomer; however, both increased coatomer-dependent activity. Peptides from p24 cargo proteins increased Arf GAP2 activity by an additional 2- to 4-fold. The effect of cargo peptide was dependent on coatomer. Overexpressing the cargo protein p25 decreased cellular Arf1*GTP levels. The differential sensitivity of Arf GAP1 and Arf GAP2 to coatomer could coordinate their activities. Based on the common regulatory features of Arf GAP1 and 2, we propose a mechanism for cargo selection in which GTP hydrolysis triggered by cargo binding to the coat protein is coupled to coat polymerization.
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Affiliation(s)
- Ruibai Luo
- Laboratory of Cellular and Molecular Biology, National Cancer Institute, Bethesda, MD 20892, USA
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70
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Balla T, Várnai P. Visualization of cellular phosphoinositide pools with GFP-fused protein-domains. CURRENT PROTOCOLS IN CELL BIOLOGY 2009; Chapter 24:Unit 24.4. [PMID: 19283730 PMCID: PMC3125592 DOI: 10.1002/0471143030.cb2404s42] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
This unit describes the method of following phosphoinositide dynamics in live cells. Inositol phospholipids have emerged as universal signaling molecules present in virtually every membrane of eukaryotic cells. Phosphoinositides are present in only tiny amounts as compared to structural lipids, but they are metabolically very active as they are produced and degraded by the numerous inositide kinase and phosphatase enzymes. Phosphoinositides control the membrane recruitment and activity of many membrane protein signaling complexes in specific membrane compartments, and they have been implicated in the regulation of a variety of signaling and trafficking pathways. It has been a challenge to develop methods that allow detection of phosphoinositides at the single-cell level. The only available technique in live cell applications is based on the use of the same protein domains selected by evolution to recognize cellular phosphoinositides. Some of these isolated protein modules, when fused to fluorescent proteins, can follow dynamic changes in phosphoinositides. While this technique can provide information on phosphoinositide dynamics in live cells with subcellular localization, and it has rapidly gained popularity, it also has several limitations that must be taken into account when interpreting the data. This unit summarizes the design and practical use of these constructs and also reviews important considerations for interpretation of the data obtained by this technique.
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Affiliation(s)
- Tamas Balla
- Section on Molecular Signal Transduction, Program for Developmental Neuroscience, NICHD, National Institutes of Health, Bethesda, MD 20892 USA
| | - Péter Várnai
- Department of Physiology, Semmelweis University Medical School, Budapest, Hungary
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71
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Abstract
Phosphoinositides are an important component of the cell as they have a variety of roles that include cytoskeleton regulation, generation of second messengers, endosome trafficking, membrane transport and regulation of ion channels. The direct interaction between phosphatidylinositol-4,5-bisphosphate (PIP(2)) and various inwardly rectifying potassium channels has been shown in recent years. Most of these studies have used existing electrophysiological methods. In this review, we describe a rapid and convenient biochemical assay that can be used to show direct binding of potassium channel subunits to anionic phospholipids. This method has been used to demonstrate the differences in affinity between members of the Kir3.0 family, where only the cytoplasmic C-terminal Kir3.1 domain and the N- and C-terminal domains of Kir3.4 have the ability to bind to anionic phospholipids.
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72
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Thole JM, Nielsen E. Phosphoinositides in plants: novel functions in membrane trafficking. CURRENT OPINION IN PLANT BIOLOGY 2008; 11:620-31. [PMID: 19028349 DOI: 10.1016/j.pbi.2008.10.010] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2008] [Revised: 09/23/2008] [Accepted: 10/28/2008] [Indexed: 05/07/2023]
Abstract
Tight regulation of membrane trafficking is crucial to the proper maintenance of the endomembrane trafficking system of eukaryotic cells. Distinct organelles must maintain their identities while at the same time continuously accepting, sorting, and exchanging membrane and luminal cargo constituents. Additionally, many of these organelles differentiate specialized subdomains containing distinct sets of lipids and proteins and restrict certain aspects of membrane trafficking to these regions of the organelle. Phosphoinositides (PIs) are a class of membrane lipids that have emerged as key components in some of these membrane trafficking events. The ability of these lipids to be rapidly produced, modified, and hydrolyzed by distinct classes of phosphatidylinositol (PtdIns) kinases, phosphatases, and phospholipases, allows for their use as finely tuned spatial and temporal landmarks for organelle and sub-organelle domains. In this review we will attempt to highlight some of the recent studies of the roles of this class of lipids in plant membrane trafficking, particularly on their important roles in polarized membrane trafficking in plants.
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Affiliation(s)
- Julie M Thole
- Department of Biology, Washington University, One Brookings Drive, St. Louis, MO 63130, United States
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73
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Blagoveshchenskaya A, Mayinger P. SAC1 lipid phosphatase and growth control of the secretory pathway. MOLECULAR BIOSYSTEMS 2008; 5:36-42. [PMID: 19081929 DOI: 10.1039/b810979f] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Phosphoinositide lipids play a dual role in cell physiology. Specific sets of these molecules are short-lived downstream mediators of growth signals, regulating cell survival and differentiation. In addition, distinct classes of phosphoinositide lipids function as constitutive mediators of membrane traffic and organelle identity. Recent work has provided the first direct evidence that phosphoinositides also play a direct role in linking protein secretion with cell growth and proliferation. This review focuses on SAC1 lipid phosphatase and how this enzyme operates in an evolutionary conserved mechanism to coordinate the secretory capacity of ER and Golgi during cell growth.
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Affiliation(s)
- Anastasia Blagoveshchenskaya
- Division of Nephrology & Hypertension and Department of Cell & Developmental Biology, Oregon Health & Science University, Portland, Oregon, USA
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74
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Daniele T, Di Tullio G, Santoro M, Turacchio G, De Matteis MA. ARAP1 regulates EGF receptor trafficking and signalling. Traffic 2008; 9:2221-35. [PMID: 18764928 DOI: 10.1111/j.1600-0854.2008.00823.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
The activation state of the EGF receptor (EGF-R) is tightly controlled in the cell so as to prevent excessive signalling, with the dangerous consequences that this would have on cell growth and proliferation. This control occurs at different levels, with a key level being the trafficking and degradation of the EGF-R itself. Multiple guanosine triphosphatases belonging to the Arf, Rab and Rho families and their accessory proteins have key roles in these processes. In this study, we have identified ARAP1, a multidomain protein with both Arf GTPase-activating protein (GAP) and Rho GAP activities, as a novel component of the machinery that controls the trafficking and signalling of the EGF-R. We show that ARAP1 localizes to multiple cell compartments, including the Golgi complex, as previously reported, and endosomal compartments, where it is enriched in the internal membranes of multivesicular bodies. ARAP1 distribution is controlled by its phosphorylation and by its interactions with the 3- and 4-phosphorylated phosphoinositides through its five PH domains. We provide evidence that ARAP1 controls the late steps of the endocytic trafficking of the EGF-R, with ARAP1 knockdown leading to EGF-R accumulation in a sorting/late endosomal compartment and to the inhibition of EGF-R degradation that is accompanied by prolonged signalling.
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Affiliation(s)
- Tiziana Daniele
- Laboratory of Physiopathology of Secretion, Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, 66030 Santa Maria Imbaro, Chieti, Italy
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75
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Curwin AJ, McMaster CR. Structure and function of the enigmatic Sec14 domain-containing proteins and the etiology of human disease. ACTA ACUST UNITED AC 2008. [DOI: 10.2217/17460875.3.4.399] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
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76
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Blagoveshchenskaya A, Cheong FY, Rohde HM, Glover G, Knödler A, Nicolson T, Boehmelt G, Mayinger P. Integration of Golgi trafficking and growth factor signaling by the lipid phosphatase SAC1. ACTA ACUST UNITED AC 2008; 180:803-12. [PMID: 18299350 PMCID: PMC2265582 DOI: 10.1083/jcb.200708109] [Citation(s) in RCA: 290] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
When a growing cell expands, lipids and proteins must be delivered to its periphery. Although this phenomenon has been observed for decades, it remains unknown how the secretory pathway responds to growth signaling. We demonstrate that control of Golgi phosphatidylinositol-4-phosphate (PI(4)P) is required for growth-dependent secretion. The phosphoinositide phosphatase SAC1 accumulates at the Golgi in quiescent cells and down-regulates anterograde trafficking by depleting Golgi PI(4)P. Golgi localization requires oligomerization of SAC1 and recruitment of the coat protein (COP) II complex. When quiescent cells are stimulated by mitogens, SAC1 rapidly shuttles back to the endoplasmic reticulum (ER), thus releasing the brake on Golgi secretion. The p38 mitogen-activated kinase (MAPK) pathway induces dissociation of SAC1 oligomers after mitogen stimulation, which triggers COP-I–mediated retrieval of SAC1 to the ER. Inhibition of p38 MAPK abolishes growth factor–induced Golgi-to-ER shuttling of SAC1 and slows secretion. These results suggest direct roles for p38 MAPK and SAC1 in transmitting growth signals to the secretory machinery.
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77
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Demmel L, Gravert M, Ercan E, Habermann B, Müller-Reichert T, Kukhtina V, Haucke V, Baust T, Sohrmann M, Kalaidzidis Y, Klose C, Beck M, Peter M, Walch-Solimena C. The clathrin adaptor Gga2p is a phosphatidylinositol 4-phosphate effector at the Golgi exit. Mol Biol Cell 2008; 19:1991-2002. [PMID: 18287542 DOI: 10.1091/mbc.e06-10-0937] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Phosphatidylinositol 4-phosphate (PI(4)P) is a key regulator of membrane transport required for the formation of transport carriers from the trans-Golgi network (TGN). The molecular mechanisms of PI(4)P signaling in this process are still poorly understood. In a search for PI(4)P effector molecules, we performed a screen for synthetic lethals in a background of reduced PI(4)P and found the gene GGA2. Our analysis uncovered a PI(4)P-dependent recruitment of the clathrin adaptor Gga2p to the TGN during Golgi-to-endosome trafficking. Gga2p recruitment to liposomes is stimulated both by PI(4)P and the small GTPase Arf1p in its active conformation, implicating these two molecules in the recruitment of Gga2p to the TGN, which ultimately controls the formation of clathrin-coated vesicles. PI(4)P binding occurs through a phosphoinositide-binding signature within the N-terminal VHS domain of Gga2p resembling a motif found in other clathrin interacting proteins. These data provide an explanation for the TGN-specific membrane recruitment of Gga2p.
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Affiliation(s)
- Lars Demmel
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, D-01307, Germany
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78
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Knödler A, Konrad G, Mayinger P. Expression of yeast lipid phosphatase Sac1p is regulated by phosphatidylinositol-4-phosphate. BMC Mol Biol 2008; 9:16. [PMID: 18226253 PMCID: PMC2258305 DOI: 10.1186/1471-2199-9-16] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2007] [Accepted: 01/28/2008] [Indexed: 01/06/2023] Open
Abstract
Background Phosphoinositides play a central role in regulating processes at intracellular membranes. In yeast, a large number of phospholipid biosynthetic enzymes use a common mechanism for transcriptional regulation. Yet, how the expression of genes encoding lipid kinases and phosphatases is regulated remains unknown. Results Here we show that the expression of lipid phosphatase Sac1p in the yeast Saccharomyces cerevisiae is regulated in response to changes in phosphatidylinositol-4-phosphate (PI(4)P) concentrations. Unlike genes encoding enzymes involved in phospholipid biosynthesis, expression of the SAC1 gene is independent of inositol levels. We identified a novel 9-bp motif within the 5' untranslated region (5'-UTR) of SAC1 that is responsible for PI(4)P-mediated regulation. Upregulation of SAC1 promoter activity correlates with elevated levels of Sac1 protein levels. Conclusion Regulation of Sac1p expression via the concentration of its major substrate PI(4)P ensures proper maintenance of compartment-specific pools of PI(4)P.
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Affiliation(s)
- Andreas Knödler
- Division of Nephrology and Hypertension, Oregon Health & Science University, Portland OR 97239, USA.
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79
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van Leeuwen W, Vermeer JEM, Gadella TWJ, Munnik T. Visualization of phosphatidylinositol 4,5-bisphosphate in the plasma membrane of suspension-cultured tobacco BY-2 cells and whole Arabidopsis seedlings. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2007; 52:1014-26. [PMID: 17908156 DOI: 10.1111/j.1365-313x.2007.03292.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P(2)] is an important signalling lipid in mammalian cells, where it functions as a second-messenger precursor in response to agonist-dependent activation of phospholipase C (PLC) but also operates as a signalling molecule on its own. Much of the recent knowledge about it has come from a new technique to visualize PtdIns(4,5)P(2)in vivo, by expressing a green or yellow fluorescent protein (GFP or YFP) fused to the pleckstrin homology (PH) domain of human PLCdelta1 that specifically binds PtdIns(4,5)P(2). In this way, YFP-PH(PLCdelta1) has been shown to predominantly label the plasma membrane and to transiently translocate into the cytoplasm upon PLC activation in a variety of mammalian cell systems. In plants, biochemical studies have shown that PtdIns(4,5)P(2) is present in very small quantities, but knowledge of its localization and function is still very limited. In this study, we have used YFP-PH(PLCdelta1) to try monitoring PtdIns(4,5)P(2)/PLC signalling in stably-transformed tobacco Bright Yellow-2 (BY-2) cells and Arabidopsis seedlings. In both plant systems, no detrimental effects were observed, indicating that overexpression of the biosensor did not interfere with the function of PtdIns(4,5)P(2). Confocal imaging revealed that most of the YFP-PH(PLCdelta1) fluorescence was present in the cytoplasm, and not in the plasma membrane as in mammalian cells. Nonetheless, four conditions were found in which YFP-PH(PLCdelta1) was concentrated at the plasma membrane: (i) upon treatment with the PLC inhibitor U73122; (ii) in response to salt stress; (iii) as a gradient at the tip of growing root hairs; (iv) during the final stage of a BY-2 cell division. We conclude that PtdIns(4,5)P(2), as in animals, is present in the plasma membrane of plants, but that its concentration in most cells is too low to be detected by YFP-PH(PLCdelta1). Hence, the reporter remains unbound in the cytosol, making it unsuitable to monitor PLC signalling. Nonetheless, YFP-PH(PLCdelta1) is a valuable plant PtdIns(4,5)P(2) reporter, for it highlights specific cells and conditions where this lipid becomes abnormally concentrated in membranes, raising the question of what it is doing there. New roles for PtdIns(4,5)P(2) in plant cell signalling are discussed.
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Affiliation(s)
- Wessel van Leeuwen
- Section Plant Physiology, University of Amsterdam, Swammerdam Institute for Life Sciences, Kruislaan 318, NL-1098 SM, Amsterdam, The Netherlands
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80
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Williams C, Choudhury R, McKenzie E, Lowe M. Targeting of the type II inositol polyphosphate 5-phosphatase INPP5B to the early secretory pathway. J Cell Sci 2007; 120:3941-51. [DOI: 10.1242/jcs.014423] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The inositol polyphosphate 5-phosphatase INPP5B is closely related to the Lowe syndrome protein OCRL1, sharing a similar substrate specificity, domain organisation and an ability to compensate for loss of OCRL1 in knockout mice. The cellular localisation and functions of INPP5B have remained poorly defined until recently, when a role within the endocytic pathway was suggested. Here, we report that INPP5B is also localised to the early secretory pathway including the Golgi apparatus and ER-to-Golgi intermediate compartment (ERGIC). Consistent with this localisation, INPP5B binds to specific RAB proteins within the secretory pathway, and mutational analysis indicates that RAB binding is required for efficient Golgi targeting of INPP5B. Unlike OCRL1, INPP5B interacts with neither clathrin nor α-adaptin and is largely absent from clathrin-coated intermediates. Expression of INPP5B but not OCRL1 alters the distribution of the cycling protein ERGIC53 when cells are incubated at low temperature (15°C) or in the presence of brefeldin A, causing ERGIC53 to accumulate in the ERGIC, with a concomitant loss from the ER. Our data suggest a role for INPP5B in retrograde ERGIC-to-ER transport and imply that it has functions distinct from those of OCRL1 within both the secretory and endocytic pathways.
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Affiliation(s)
- Catrin Williams
- Faculty of Life Sciences, University of Manchester, The Michael Smith Building, Oxford Road, Manchester M13 9PT, UK
| | - Rawshan Choudhury
- Faculty of Life Sciences, University of Manchester, The Michael Smith Building, Oxford Road, Manchester M13 9PT, UK
| | - Eddie McKenzie
- Faculty of Life Sciences, University of Manchester, The Michael Smith Building, Oxford Road, Manchester M13 9PT, UK
| | - Martin Lowe
- Faculty of Life Sciences, University of Manchester, The Michael Smith Building, Oxford Road, Manchester M13 9PT, UK
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81
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Heuvingh J, Franco M, Chavrier P, Sykes C. ARF1-mediated actin polymerization produces movement of artificial vesicles. Proc Natl Acad Sci U S A 2007; 104:16928-33. [PMID: 17942688 PMCID: PMC2040406 DOI: 10.1073/pnas.0704749104] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2007] [Indexed: 11/18/2022] Open
Abstract
Vesicular trafficking and actin dynamics on Golgi membranes are both regulated by ADP-ribosylation factor 1 (ARF1) through the recruitment of various effectors, including vesicular coats. Actin assembly on Golgi membranes contributes to the architecture of the Golgi complex, vesicle formation, and trafficking and is mediated by ARF1 through a cascade that leads to Arp2/3 complex activation. Here we addressed the role of Golgi actin downstream of ARF1 by using a biomimetic assay consisting of liposomes of defined lipid composition, carrying an activated form of ARF1 incubated in cytosolic cell extracts. We observed actin polymerization around the liposomes resulting in thick actin shells and actin comet tails that pushed the ARF1 liposomes forward. The assay was used to characterize the ARF1-dependent pathway, leading to actin polymerization, and confirmed a dependency on CDC42 and its downstream effector N-WASP. Overall, this study demonstrates that actin polymerization driven by the complex multicomponent signaling cascade of the Golgi apparatus can be reproduced with a biomimetic system. Moreover, our results are consistent with the view that actin-based force generation at the site of vesicle formation contributes to the mechanism of fission. In addition to its well established function in coat recruitment, the ARF1 machinery also might produce movement- and fission-promoting forces through actin polymerization.
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Affiliation(s)
- Julien Heuvingh
- *Centre de Recherche, Institut Curie, F-75248 Paris, France
- Unités Mixte de Recherche 168 and
- 144, Centre National de la Recherche Scientifique, F-75248 Paris, France
- Université Paris VI, F-75248 Paris, France; and
| | - Michel Franco
- Institut de Pharmacologie Moléculaire et Cellulaire, Unité Mixte de Recherche 6097, Centre National de la Recherche Scientifique, F-06560 Valbonne, France
| | - Philippe Chavrier
- *Centre de Recherche, Institut Curie, F-75248 Paris, France
- 144, Centre National de la Recherche Scientifique, F-75248 Paris, France
| | - Cécile Sykes
- *Centre de Recherche, Institut Curie, F-75248 Paris, France
- Unités Mixte de Recherche 168 and
- Université Paris VI, F-75248 Paris, France; and
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82
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Haynes LP, Sherwood MW, Dolman NJ, Burgoyne RD. Specificity, promiscuity and localization of ARF protein interactions with NCS-1 and phosphatidylinositol-4 kinase-III beta. Traffic 2007; 8:1080-92. [PMID: 17555535 PMCID: PMC2492389 DOI: 10.1111/j.1600-0854.2007.00594.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
ADP-ribosylation factor (ARF) proteins are involved in multiple intracellular vesicular transport pathways. Most studies have focused on the functions of ARF1 or ARF6 and little is known about the remaining ARF isoforms. Although the mammalian ARF proteins share a high degree of sequence identity, recent evidence has indicated that they may control distinct trafficking steps within cells. A unanswered issue is the degree of specificity of ARF family members for different interacting proteins. To investigate potential functional differences between the human ARF proteins, we have examined the localization of all human ARF isoforms and their interactions with two ARF1 binding proteins, neuronal calcium sensor-1 (NCS-1) and phosphatidylinositol-4 kinase-IIIbeta (PI4Kbeta). Use of a fluorescent protein fragment complementation method showed direct interactions between ARFs 1, 3, 5 and 6 with NCS-1 but at different intracellular locations in live HeLa cells. Photobleaching experiments indicated that complementation did not detect dynamic changes in protein interactions over short-time scales. A more specific interaction between ARFs 1/3 and PI4Kbeta was observed. Consistent with these latter findings ARF1 but not ARF5 or 6 enhanced the stimulatory effect of PI4Kbeta on regulated exocytosis, suggesting a specific role for class-I ARFs in the regulation of PI4Kbeta.
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Affiliation(s)
- Lee P Haynes
- The Physiological Laboratory, School of Biomedical Sciences, University of Liverpool, Crown Street, Liverpool, L69 3BX, UK
| | - Mark W. Sherwood
- The Physiological Laboratory, School of Biomedical Sciences, University of Liverpool, Crown Street, Liverpool, L69 3BX, UK
| | - Nick J Dolman
- The Physiological Laboratory, School of Biomedical Sciences, University of Liverpool, Crown Street, Liverpool, L69 3BX, UK
| | - Robert D Burgoyne
- The Physiological Laboratory, School of Biomedical Sciences, University of Liverpool, Crown Street, Liverpool, L69 3BX, UK
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83
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Rodgers MJ, Albanesi JP, Phillips MA. Phosphatidylinositol 4-kinase III-beta is required for Golgi maintenance and cytokinesis in Trypanosoma brucei. EUKARYOTIC CELL 2007; 6:1108-18. [PMID: 17483288 PMCID: PMC1951100 DOI: 10.1128/ec.00107-07] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The parasitic protozoan Trypanosoma brucei contains two type III phosphatidylinositol 4-kinases (alpha and beta). We have cloned the gene encoding the T. brucei type III phosphatidylinositol 4-kinase beta (TbPI4KIII-beta), expressed the protein in COS-7 cells, and confirmed that the protein catalyzes the phosphorylation of phosphatidylinositol. Depletion of TbPI4KIII-beta in procyclic T. brucei by RNA interference (RNAi) resulted in inhibition of cell growth and a distorted cellular morphology. RNAi cells had a distorted Golgi apparatus, and lysosomal and flagellar pocket proteins were mislocalized. Ultrastructural analysis revealed the internal accumulation of a heterogeneous population of vesicles, abnormal positioning of organelles, and a loss of cell polarity. Scanning electron microcopy revealed a twisted phenotype, and dividing cells often exhibited a detached daughter flagellum and lacked a cleavage furrow. Cell cycle analysis confirmed that cells depleted of TbPI4KIII-beta have a postmitotic cytokinesis block that occurs after a single round of mitosis, suggestive of a specific cell cycle block. In summary, TbPI4KIII-beta is an essential protein in procyclic T. brucei, required for maintenance of Golgi structure, protein trafficking, normal cellular shape, and cytokinesis.
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Affiliation(s)
- Melissa J Rodgers
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9041, USA
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84
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Várnai P, Balla T. Visualization and manipulation of phosphoinositide dynamics in live cells using engineered protein domains. Pflugers Arch 2007; 455:69-82. [PMID: 17473931 DOI: 10.1007/s00424-007-0270-y] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2007] [Accepted: 04/12/2007] [Indexed: 11/26/2022]
Abstract
There is hardly a membrane-associated molecular event that is not regulated by phosphoinositides, a minor but critically important class of phospholipids of cellular membranes. The rapid formation, elimination, and conversion of these lipids in specific membrane compartments are ensured by a wealthy number of inositol lipid kinases and phosphatases with unique localization and regulatory properties. The existence of multiple inositol lipid pools have been indicated by metabolic labeling studies, but the level of functional compartmentalization revealed by the identification of numerous protein effectors acted upon by phosphoinositides could not have been foreseen. The changing perception of inositides from just serving as lipid precursors of second messengers to becoming highly dynamic local membrane-bound regulators poses new challenges concerning the detection of their rapid localized changes. Moreover, it is increasingly evident that manipulation of lipids in highly defined compartments would be a highly superior approach to soaking the cells with a particular phosphoinositide when studying the local regulation of the lipid on any effectors. In this review, we will summarize our efforts to improve our tools in studying phosphoinositide dynamics and discuss our views on the values of these methods compared to other options currently used or being explored.
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Affiliation(s)
- Péter Várnai
- Endocrinology and Reproduction Research Branch, NICHD, National Institutes of Health, Bldg 49, Rm 6A35, 49 Convent Drive, Bethesda, MD, USA.
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85
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Karataeva NA, Nevinsky GA. Enzymes phosphorylating lipids and polysaccharides. BIOCHEMISTRY. BIOKHIMIIA 2007; 72:367-79. [PMID: 17511601 DOI: 10.1134/s0006297907040037] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Phosphorylation plays an important role in regulation of living functions of organisms; phosphorylation may significantly alter chemical properties of proteins, lipids, and carbohydrates. Canonical kinases catalyze transfer of terminal phosphate group from ATP (or other NTPs) to specific nucleophilic groups of proteins, lipids, and polysaccharides. Recently, unique kinases, catalytically active antibodies (abzymes) phosphorylating proteins, lipids, and polysaccharides have also been discovered. This review highlights biological functions and enzymatic characteristics of canonical kinases and abzymes phosphorylating lipids and polysaccharides.
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Affiliation(s)
- N A Karataeva
- Institute of Chemical Biology and Fundamental Medicine, Siberian Branch of the Russian Academy of Sciences, 630090 Novosibirsk, Russia
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86
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Abstract
Phosphoinositides are minor phospholipid constituents of virtually every biological membrane yet they play fundamental roles in controlling membrane-bound signalling events. Phosphoinositides are produced from phosphatidylinositol (PtdIns) by phosphorylation of one or more of three positions (3, 4 and 5) of the inositol headgroup located at the membrane cytoplasmic interface by distinct families of inositol lipid kinases. Intriguingly, many of the kinase reactions are catalysed by more than one form of the kinases even in simple organisms and these enzymes often assume non-redundant functions. A similar diversity is seen with inositide phosphatases, the enzymes that dephosphorylate phosphoinositides with a certain degree of specificity and the impairments of which are often linked to human diseases. This degree of multiplicity at the enzyme level together with the universal roles of these lipids in cell regulation assumes that inositol lipids are spatially and functionally restricted in specific membrane compartments. Studying the compartmentalized roles of these lipids at the cellular level represents a major methodological challenge. Over the last 10 years significant progress has been made in creating reagents that can monitor inositol lipid changes in live cells with fluorescence or confocal microscopy. New methods are also being developed to manipulate these lipids in specific membrane compartments in a regulated fashion. This article recalls some historical aspects of inositide research and describes the new methodological advances highlighting their great potential as well as the problems one can encounter with their use.
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Affiliation(s)
- Tamas Balla
- National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
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87
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Zoncu R, Perera RM, Sebastian R, Nakatsu F, Chen H, Balla T, Ayala G, Toomre D, De Camilli PV. Loss of endocytic clathrin-coated pits upon acute depletion of phosphatidylinositol 4,5-bisphosphate. Proc Natl Acad Sci U S A 2007; 104:3793-8. [PMID: 17360432 PMCID: PMC1805489 DOI: 10.1073/pnas.0611733104] [Citation(s) in RCA: 210] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Phosphatidylinositol 4,5-bisphosphate [PI(4,5)P(2)], a phosphoinositide concentrated predominantly in the plasma membrane, binds endocytic clathrin adaptors, many of their accessory factors, and a variety of actin-regulatory proteins. Here we have used fluorescent fusion proteins and total internal reflection fluorescence microscopy to investigate the effect of acute PI(4,5)P(2) breakdown on the dynamics of endocytic clathrin-coated pit components and of the actin regulatory complex, Arp2/3. PI(4,5)P(2) breakdown was achieved by the inducible recruitment to the plasma membrane of an inositol 5-phosphatase module through the rapamycin/FRB/FKBP system or by treatment with ionomycin. PI(4,5)P(2) depletion resulted in a dramatic loss of clathrin puncta, which correlated with a massive dissociation of endocytic adaptors from the plasma membrane. Remaining clathrin spots at the cell surface had only weak fluorescence and were static over time. Dynamin and the p20 subunit of the Arp2/3 actin regulatory complex, which were concentrated at late-stage clathrin-coated pits and in lamellipodia, also dissociated from the plasma membrane, and these changes correlated with an arrest of motility at the cell edge. These findings demonstrate the critical importance of PI(4,5)P(2) in clathrin coat dynamics and Arp2/3-dependent actin regulation.
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Affiliation(s)
- Roberto Zoncu
- *Department of Cell Biology and
- Howard Hughes Medical Institute, Kavli Institute For Neuroscience and Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, CT 06510
| | | | - Rafael Sebastian
- Departamento de Informatica, Universidad de Valencia, Avenida Vicente Andres Estelles, s/n, 46100 Burjasot, Spain; and
| | - Fubito Nakatsu
- *Department of Cell Biology and
- Howard Hughes Medical Institute, Kavli Institute For Neuroscience and Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, CT 06510
| | - Hong Chen
- *Department of Cell Biology and
- Howard Hughes Medical Institute, Kavli Institute For Neuroscience and Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, CT 06510
| | - Tamas Balla
- Section on Molecular Signal Transduction, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892
| | - Guillermo Ayala
- Departamento de Informatica, Universidad de Valencia, Avenida Vicente Andres Estelles, s/n, 46100 Burjasot, Spain; and
| | - Derek Toomre
- *Department of Cell Biology and
- To whom correspondence may be addressed. E-mail: or
| | - Pietro V. De Camilli
- *Department of Cell Biology and
- Howard Hughes Medical Institute, Kavli Institute For Neuroscience and Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, CT 06510
- To whom correspondence may be addressed. E-mail: or
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88
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Derby MC, Gleeson PA. New Insights into Membrane Trafficking and Protein Sorting. INTERNATIONAL REVIEW OF CYTOLOGY 2007; 261:47-116. [PMID: 17560280 DOI: 10.1016/s0074-7696(07)61002-x] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Protein transport in the secretory and endocytic pathways is a multistep process involving the generation of transport carriers loaded with defined sets of cargo, the shipment of the cargo-loaded transport carriers between compartments, and the specific fusion of these transport carriers with a target membrane. The regulation of these membrane-mediated processes involves a complex array of protein and lipid interactions. As the machinery and regulatory processes of membrane trafficking have been defined, it is increasingly apparent that membrane transport is intimately connected with a number of other cellular processes, such as quality control in the endoplasmic reticulum (ER), cytoskeletal dynamics, receptor signaling, and mitosis. The fidelity of membrane trafficking relies on the correct assembly of components on organelles. Recruitment of peripheral proteins plays a critical role in defining organelle identity and the establishment of membrane subdomains, essential for the regulation of vesicle transport. The molecular mechanisms for the biogenesis of membrane subdomains are also central to understanding how cargo is sorted and segregated and how different populations of transport carriers are generated. In this review we will focus on the emerging themes of organelle identity, membrane subdomains, regulation of Golgi trafficking, and advances in dissecting pathways in physiological systems.
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Affiliation(s)
- Merran C Derby
- Department of Biochemistry and Molecular Biology and Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Melbourne, Victoria 3010, Australia
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89
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Hammond GRV, Schiavo G. Polyphosphoinositol lipids: Under-PPInning synaptic function in health and disease. Dev Neurobiol 2007; 67:1232-47. [PMID: 17514716 DOI: 10.1002/dneu.20509] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Phosphoinositides (PPIn) form a unique family of lipids derived by phosphorylation of the parent compound, phosphatidylinositol. Despite being minor constituents of synaptic membranes, these lipids have exceptionally high rates of metabolic turnover and are involved with myriad aspects of pre- and post-synaptic function, from the control of the synaptic vesicle cycle to postsynaptic excitability. In this review, we outline the main synaptic processes known to be regulated by these molecules, focusing mainly but not exclusively on the major species phosphatidylinositol 4-phosphate and phosphatidylinositol (4,5)-bisphosphate. Furthermore, we discuss the enzymes responsible for their synthesis and degradation, with a view to exploring how the activity-dependent control of their enzymatic action can lead to the precise regulation of PPIn levels at the nerve terminal. Also, the modulation of synaptic PPIn turnover by drugs used for the treatment of bipolar disorder is discussed. We propose that the modulation of PPIn levels may act as a central mechanism to coordinate the cascade of synaptic events leading to neurotransmission.
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Affiliation(s)
- Gerald R V Hammond
- Molecular NeuroPathobiology, Cancer Research UK London Research Institute, Lincoln's Inn Fields Laboratories, London WC2A 3PX, United Kingdom.
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90
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Lay D, Gorgas K, Just WW. Peroxisome biogenesis: Where Arf and coatomer might be involved. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2006; 1763:1678-87. [PMID: 17023067 DOI: 10.1016/j.bbamcr.2006.08.036] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2006] [Revised: 08/12/2006] [Accepted: 08/23/2006] [Indexed: 11/24/2022]
Abstract
The present review summarizes recent observations on binding of Arf and COPI coat to isolated rat liver peroxisomes. The general structural and functional features of both Arf and coatomer were considered along with the requirements and dependencies of peroxisomal Arf and coatomer recruitment. Studies on the expression of mammalian Pex11 proteins, mainly Pex11alpha and Pex11beta, intimately related to the process of peroxisome proliferation, revealed a sequence of individual steps including organelle elongation/tubulation, formation of membrane and matrix protein patches segregating distinct proteins from each other, development of membrane constrictions and final membrane fission. Based on the similarities of the processes leading to cargo selection and concentration on Golgi membranes on the one hand and to the formation of peroxisomal protein patches on the other hand, an implication of Arf and COPI in distinct processes of peroxisomal proliferation is hypothesized. Alternatively, peroxisomal Arf/COPI might facilitate the formation of COPI-coated peroxisomal vesicles functioning in cargo transport and retrieval from peroxisomes to the ER. Recent observations suggesting transport of Pex3 and Pex19 during early steps of peroxisome biogenesis from the ER to peroxisomes inevitably propose such a retrieval mechanism, provided the ER to peroxisome pathway is based on transporting vesicles.
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Affiliation(s)
- Dorothee Lay
- Biochemie-Zentrum der Universität Heidelberg (BZH), Im Neuenheimer Feld 328D-69120 Heidelberg, Germany
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91
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Abstract
Inositol phospholipids have long been known to have an important regulatory role in cell physiology. The repertoire of cellular processes known to be directly or indirectly controlled by this class of lipids has now dramatically expanded. Through interactions mediated by their headgroups, which can be reversibly phosphorylated to generate seven species, phosphoinositides play a fundamental part in controlling membrane-cytosol interfaces. These lipids mediate acute responses, but also act as constitutive signals that help define organelle identity. Their functions, besides classical signal transduction at the cell surface, include regulation of membrane traffic, the cytoskeleton, nuclear events and the permeability and transport functions of membranes.
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Affiliation(s)
- Gilbert Di Paolo
- Department of Pathology and Cell Biology, The Taub Institute for Research on Alzheimer's Disease and the Aging Brain, Columbia University Medical Center, New York, New York 10032, USA.
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92
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Radulescu AE, Siddhanta A, Shields D. A role for clathrin in reassembly of the Golgi apparatus. Mol Biol Cell 2006; 18:94-105. [PMID: 17065556 PMCID: PMC1751329 DOI: 10.1091/mbc.e06-06-0532] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The Golgi apparatus is a highly dynamic organelle whose organization is maintained by a proteinaceous matrix, cytoskeletal components, and inositol phospholipids. In mammalian cells, disassembly of the organelle occurs reversibly at the onset of mitosis and irreversibly during apoptosis. Several pharmacological agents including nocodazole, brefeldin A (BFA), and primary alcohols (1-butanol) induce reversible fragmentation of the Golgi apparatus. To dissect the mechanism of Golgi reassembly, rat NRK and GH3 cells were treated with 1-butanol, BFA, or nocodazole. During washout of 1-butanol, clathrin, a ubiquitous coat protein implicated in vesicle traffic at the trans-Golgi network and plasma membrane, and abundant clathrin coated vesicles were recruited to the region of nascent Golgi cisternae. Knockdown of endogenous clathrin heavy chain showed that the Golgi apparatus failed to reform efficiently after BFA or 1-butanol removal. Instead, upon 1-butanol washout, it maintained a compact, tight morphology. Our results suggest that clathrin is required to reassemble fragmented Golgi elements. In addition, we show that after butanol treatment the Golgi apparatus reforms via an initial compact intermediate structure that is subsequently remodeled into the characteristic interphase lace-like morphology and that reassembly requires clathrin.
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Affiliation(s)
| | | | - Dennis Shields
- *Departments of Developmental and Molecular Biology and
- Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, NY 10461
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93
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Béthune J, Wieland F, Moelleken J. COPI-mediated Transport. J Membr Biol 2006; 211:65-79. [PMID: 17041781 DOI: 10.1007/s00232-006-0859-7] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2005] [Revised: 03/18/2006] [Indexed: 12/27/2022]
Abstract
COPI-coated vesicles are protein and liquid carriers that mediate transport within the early secretory pathway. In this Topical Review, we present their main protein components and discuss current models for cargo sorting. Finally, we describe the striking similarities that exist between the COPI system and the two other characterized types of vesicular carriers: COPII- and clathrin-coated vesicles.
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Affiliation(s)
- J Béthune
- Biochemie Zentrum, University of Heidelberg, Im Neuenheimer Feld 328, D-69120, Heidelberg, Germany.
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94
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Jeynov B, Lay D, Schmidt F, Tahirovic S, Just WW. Phosphoinositide synthesis and degradation in isolated rat liver peroxisomes. FEBS Lett 2006; 580:5917-24. [PMID: 17045591 DOI: 10.1016/j.febslet.2006.09.058] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2006] [Revised: 09/18/2006] [Accepted: 09/19/2006] [Indexed: 11/30/2022]
Abstract
Analyzing peroxisomal phosphoinositide (PId(#)) synthesis in highly purified rat liver peroxisomes we found synthesis of phosphatidylinositol 4-phosphate (PtdIns4P), PtdIns(4,5)P(2) and PtdIns(3,5)P(2). PtdIns3P was hardly detected in vitro, however, was observed in vivo after [(32)P]-phosphate labeling of primary rat hepatocytes. In comparison with other subcellular organelles peroxisomes revealed a unique PId pattern suggesting peroxisomal specificity of the observed synthesis. Use of phosphatase inhibitors enhanced the amount of PtdIns4P. The results obtained provide evidence that isolated rat liver peroxisomes synthesize PIds and suggest the association of PId 4-kinase and PId 5-kinase and PId 4-phosphatase activities with the peroxisomal membrane.
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Affiliation(s)
- Boyan Jeynov
- Biochemie-Zentrum der Universität Heidelberg (BZH), Im Neuenheimer Feld 328, D-69120 Heidelberg, Germany
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95
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Abstract
Eukaryotic cells maintain a sophisticated network of intracellular membranous system to ensure the proper distribution and compartmentalization of cellular proteins critical for diverse functions such as cell division or cell-cell communication. Yet, little is known about the mechanism that regulates the homeostasis of this system. While analyzing the impact of sorting nexins on the trafficking of membrane type matrix metalloproteinases, we unexpectedly discovered that the expression of SNX10 induced the formation of giant vacuoles in mammalian cells. This vacuolizing activity is sensitive to mutations at the putative phosphoinositide 3-phosphate binding residue Arg(53). Domain-swap experiments with SNX3 demonstrate that the PX domain of SNX10 alone is insufficient to generate vacuoles and the downstream C-terminal domain is required for vacuolization. Brefeldin A, a chemical known to block the endoplasmic reticulum to Golgi transport, inhibited the vacuolization process. Together, these results suggest that SNX10 activity may be involved in the regulation of endosome homeostasis.
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Affiliation(s)
- Baoming Qin
- Guangzhou Institute of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510663, China
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96
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Slomiany A, Grabska M, Slomiany BL. Homeostatic restitution of cell membranes. Nuclear membrane lipid biogenesis and transport of protein from cytosol to intranuclear spaces. Int J Biol Sci 2006; 2:216-26. [PMID: 16967103 PMCID: PMC1560408 DOI: 10.7150/ijbs.2.216] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2006] [Accepted: 08/29/2006] [Indexed: 01/08/2023] Open
Abstract
Our studies on homeostatic restitution of cellular and subcellular membranes showed that vesicular intracellular transport is engaged in systematic and coordinated replacement of lipids and proteins in the membranes of the secretory, non-dividing epithelial cells (Slomiany et al., J. Physiol. Pharmacol. 2004; 55: 837-860). In this report, we present evidence on the homeostatic restitution of lipids in the biomembranes that constitute nuclear envelopes. We investigated nuclear membranes lipid synthesis by employing purified intact nuclei (IN), the outer nuclear membrane (ONM), the inner nuclear membrane (INM) and the cell cytosol (CC). In contrast to Endoplasmic Reticulum (ER) which in the presence of CC generates new biomembrane that forms ER vesicles transporting ER products to Golgi, the IN, ONM and INM are not producing transport vesicles. Instead, the newly synthesized lipids remain in the nuclear membranes. The membranes (INM, ONM) of IN incubated with CC become enriched with newly synthesized phosphatidylcholine (PC), phosphatidylinositol (PI), phosphatidylinositol phosphates (PIPs) and phosphatidic acid (PA). The incubation of separated ONM and INM with CC also enriched the membranes with IN specific lipids identified above. Moreover, the incubation of IN or its membranes with CC afforded retention of numerous CC proteins on the nuclear membrane. Here, we concentrated on 30kDa CC protein that displayed affinity to nuclear membrane PIP2. The 30kDa CC protein bound to PIP2 of IN, INM, and ONM. With IN, initially the PIP2-30kDa CC protein complex was detected on ONM, after 30-120 min of incubation, was found on INM and in nuclear contents. At the same time when the 30 kDa protein was released from INM and found in nuclear contents, the PIP2 of INM and ONM became undetectable, while the lipid extract from the membrane displaced from IN contained labeled PI only. Since ONM is an uninterrupted continuum of ER and INM, we speculate that the synthesis of the lipids in the ER, in the region adjacent to nucleus, is defining nuclear outer and inner biomembrane composition, is responsible for transport of the cytosolic protein into the nucleus and, replenishment of ER membrane used for vesicular transport.
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Affiliation(s)
- Amalia Slomiany
- Research Center C-873, University of Medicine and Dentistry of New Jersey, New Jersey Dental School, Newark, NJ 07103, USA.
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97
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Abstract
The unique lipid composition of the Golgi membranes is critical for maintaining their structural and functional identity, and is regulated by local lipid metabolism, a variety of lipid-binding, -modifying, -sensing and -transfer proteins, and by selective lipid sorting mechanisms. A growing body of evidence suggests that certain lipids, such as phosphoinositides and diacylglycerol, regulate Golgi-mediated transport events. However, their exact role in this process, and the underlying mechanisms that maintain their critical levels in specific membrane domains of the Golgi apparatus, remain poorly understood. Nevertheless, recent advances have revealed key regulators of lipid homoeostasis in the Golgi complex and have demonstrated their role in Golgi secretory function.
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Affiliation(s)
- S Lev
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel.
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98
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Jiang H, Sha SH, Schacht J. Kanamycin alters cytoplasmic and nuclear phosphoinositide signaling in the organ of Corti in vivo. J Neurochem 2006; 99:269-76. [PMID: 16903869 DOI: 10.1111/j.1471-4159.2006.04117.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Aminoglycoside antibiotics strongly bind to phosphoinositides and affect their membrane distribution and metabolism. Kanamycin treatment also disrupts Rac/Rho signaling pathways to the actin cytoskeleton in the mouse inner ear in vivo. Here, we investigate the influence of kanamycin on phosphoinositide signaling in sensory cells (hair cells) of the mouse cochlea. Immunoreactivity to phosphatidylinositol-3,4,5-trisphosphate (PIP3) decreased in the organ of Corti, especially in outer hair cells, after 3-7 days of drug treatment, whereas imunoreactivity to phosphatidylinositol-4,5-bisphosphate (PIP2) increased. Immunoreactivity to PIP2 was present at the apical poles of outer hair cells, but appeared in their nuclei only after drug treatment. Furthermore, nuclear PIP2 formed a complex with histone H3 and attenuated its acetylation in outer hair cells. In agreement with reduced PIP3 signaling, phosphorylated Akt decreased in both the cytoplasm and nuclei of outer hair cells after kanamycin treatment. This study suggests that kanamycin disturbs the balance between PIP2 and PIP3, modifies gene transcription via histone acetylation and diminishes the PI3K/Akt survival pathway. These actions may contribute to the death of outer hair cells, which is a consequence of chronic kanamycin treatment.
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Affiliation(s)
- Hongyan Jiang
- Kresge Hearing Research Institute, Department of Otolaryngology, University of Michigan, Ann Arbor, Michigan, USA
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99
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Balla A, Balla T. Phosphatidylinositol 4-kinases: old enzymes with emerging functions. Trends Cell Biol 2006; 16:351-61. [PMID: 16793271 DOI: 10.1016/j.tcb.2006.05.003] [Citation(s) in RCA: 285] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2006] [Revised: 04/21/2006] [Accepted: 05/22/2006] [Indexed: 11/23/2022]
Abstract
Phosphoinositides account for only a tiny fraction of cellular phospholipids but are extremely important in the regulation of the recruitment and activity of many signaling proteins in cellular membranes. Phosphatidylinositol (PtdIns) 4-kinases generate PtdIns 4-phosphate, the precursor of important regulatory phosphoinositides but also an emerging regulatory molecule in its own right. The four mammalian PtdIns 4-kinases regulate a diverse array of signaling events, as well as vesicular trafficking and lipid transport, but the mechanisms by which their lipid product PtdIns 4-phosphate controls these processes is only beginning to unfold.
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Affiliation(s)
- Andras Balla
- Endocrinology and Reproduction Research Branch, NICHD, National Institutes of Health, Bethesda, MD 20892, USA
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100
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Heuer K, Sylvester M, Kliche S, Pusch R, Thiemke K, Schraven B, Freund C. Lipid-binding hSH3 domains in immune cell adapter proteins. J Mol Biol 2006; 361:94-104. [PMID: 16831444 DOI: 10.1016/j.jmb.2006.06.004] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2006] [Revised: 06/02/2006] [Accepted: 06/02/2006] [Indexed: 11/25/2022]
Abstract
SH3 domains represent versatile scaffolds within eukaryotic cells by targeting proline-rich sequences within intracellular proteins. More recently, binding of SH3 domains to unusual peptide motifs, folded proteins or lipids has been reported. Here we show that the newly defined hSH3 domains of immune cell adapter proteins bind lipid membranes with distinct affinities. The interaction of the hSH3 domains of adhesion and degranulation promoting adapter protein (ADAP) and PRAM-1 (Promyelocytic-Retinoic acid receptor alpha target gene encoding an Adaptor Molecule-1), with phosphatidylcholine-containing liposomes is observed upon incorporation of phosphatidylserine (PS) or phosphoinositides (PIs) into the membrane bilayer. Mechanistically we show that stable association of the N-terminal, amphipathic helix with the beta-sheet scaffold favours lipid binding and that the interaction with PI(4,5)P(2)-containing liposomes is consistent with a single-site, non-cooperative binding mechanism. Functional investigations indicate that deletion of both amphipathic helices of the hSH3 domains reduces the ability of ADAP to enhance adhesion and migration in stimulated T cells.
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Affiliation(s)
- Katja Heuer
- Protein Engineering Group, Leibniz Institute of Molecular Pharmacology and Freie Universität Berlin, Germany
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