151
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Corrotte M, Chasserot-Golaz S, Huang P, Du G, Ktistakis NT, Frohman MA, Vitale N, Bader MF, Grant NJ. Dynamics and function of phospholipase D and phosphatidic acid during phagocytosis. Traffic 2006; 7:365-77. [PMID: 16497229 DOI: 10.1111/j.1600-0854.2006.00389.x] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Phospholipase D (PLD) produces phosphatidic acid (PA), an established intracellular signalling lipid that has been also implicated in vesicular trafficking, and as such, PLD could play multiple roles during phagocytosis. Using an RNA interference strategy, we show that endogenous PLD1 and PLD2 are necessary for efficient phagocytosis in murine macrophages, in line with results obtained with wild-type constructs and catalytically inactive PLD mutants which, respectively, enhance and inhibit phagocytosis. Furthermore, we found that PA is transiently produced at sites of phagosome formation. Macrophage PLD1 and PLD2 differ in their subcellular distributions. PLD1 is associated with cytoplasmic vesicles, identified as a late endosomal/lysosomal compartment, whereas PLD2 localizes at the plasma membrane. In living cells undergoing phagocytosis, PLD1 vesicles are recruited to nascent and internalized phagosomes, whereas PLD2 is only observed on nascent phagosomes. These results provide evidence that both PLD isoforms are required for phagosome formation, but only PLD1 seems to be implicated in later stages of phagocytosis occurring after phagosomal internalization.
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Affiliation(s)
- Matthias Corrotte
- Département Neurotransmission et Sécrétion Neuroendocrine, UMR 7168/LC2, CNRS/Université Louis Pasteur, Strasbourg, France
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152
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Huang S, Gao L, Blanchoin L, Staiger CJ. Heterodimeric capping protein from Arabidopsis is regulated by phosphatidic acid. Mol Biol Cell 2006; 17:1946-58. [PMID: 16436516 PMCID: PMC1415281 DOI: 10.1091/mbc.e05-09-0840] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2005] [Revised: 12/13/2005] [Accepted: 01/17/2006] [Indexed: 11/11/2022] Open
Abstract
The cytoskeleton is a key regulator of morphogenesis, sexual reproduction, and cellular responses to extracellular stimuli. Changes in the cellular architecture are often assumed to require actin-binding proteins as stimulus-response modulators, because many of these proteins are regulated directly by binding to intracellular second messengers or signaling phospholipids. Phosphatidic acid (PA) is gaining widespread acceptance as a major, abundant phospholipid in plants that is required for pollen tube tip growth and mediates responses to osmotic stress, wounding, and phytohormones; however, the number of identified effectors of PA is rather limited. Here we demonstrate that exogenous PA application leads to significant increases in filamentous actin levels in Arabidopsis suspension cells and poppy pollen grains. To investigate further these lipid-induced changes in polymer levels, we analyzed the properties of a key regulator of actin filament polymerization, the heterodimeric capping protein from Arabidopsis thaliana (AtCP). AtCP binds to PA with a K(d) value of 17 muM and stoichiometry of approximately 1:2. It also binds well to PtdIns(4,5)P(2), but not to several other phosphoinositide or acidic phospholipids. The interaction with PA inhibited the actin-binding activity of CP. In the presence of PA, CP is unable to block the barbed or rapidly growing and shrinking end of actin filaments. Precapped filament barbed ends can also be uncapped by addition of PA, allowing rapid filament assembly from an actin monomer pool that is buffered with profilin. The findings support a model in which the inhibition of CP activity in cells by elevated PA results in the stimulation of actin polymerization from a large pool of profilin-actin. Such regulation may be important for the response of plant cells to extracellular stimuli as well as for the normal process of pollen tube tip growth.
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Affiliation(s)
- Shanjin Huang
- Department of Biological Sciences and The Bindley Bioscience Center, Purdue University, West Lafayette, IN 47907-2064, USA
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153
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Mazie AR, Spix JK, Block ER, Achebe HB, Klarlund JK. Epithelial cell motility is triggered by activation of the EGF receptor through phosphatidic acid signaling. J Cell Sci 2006; 119:1645-54. [PMID: 16569667 DOI: 10.1242/jcs.02858] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Phospholipase D catalyzes the hydrolysis of phosphatidylcholine to generate phosphatidic acid, and there is currently much interest in elucidating messenger functions for this molecule. We report here that wounding sheets of corneal epithelial and Madin Darby canine kidney cells induces strong activation of phospholipase D, and we provide evidence that activation is amplified through a positive feed-back loop. Short-chain analogues of phosphatidic acid induce motility robustly in corneal and other epithelial cell types. The effects of these analogues were not the result of their conversion to the corresponding diacylglycerol or lysophosphatidic acid, implying that phosphatidic acid acts directly on one or more cellular targets. Strikingly, phosphatidic acid signaling was found to stimulate the epidermal growth factor receptor (EGFR) through a transactivation process. Healing of wounds in sheets of corneal epithelial cells is absolutely dependent on epidermal growth factor receptor signaling, and the present data suggest that its activation is a result of wound-induced phospholipase D activation.
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Affiliation(s)
- Abigail R Mazie
- Ophthalmology and Visual Sciences Research Center, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA
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154
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Kaur H, Park C, Lewis J, Haugh J. Quantitative model of Ras-phosphoinositide 3-kinase signalling cross-talk based on co-operative molecular assembly. Biochem J 2006; 393:235-43. [PMID: 16159314 PMCID: PMC1383682 DOI: 10.1042/bj20051022] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
In growth-factor-stimulated signal transduction, cell-surface receptors recruit PI3Ks (phosphoinositide 3-kinases) and Ras-specific GEFs (guanine nucleotide-exchange factors) to the plasma membrane, where they produce 3'-phosphorylated phosphoinositide lipids and Ras-GTP respectively. As a direct example of pathway networking, Ras-GTP also recruits and activates PI3Ks. To refine the mechanism of Ras-PI3K cross-talk and analyse its quantitative implications, we offer a theoretical model describing the assembly of complexes involving receptors, PI3K and Ras-GTP. While the model poses the possibility that a ternary receptor-PI3K-Ras complex forms in two steps, it also encompasses the possibility that receptor-PI3K and Ras-PI3K interactions are competitive. In support of this analysis, experiments with platelet-derived growth factor-stimulated fibroblasts revealed that Ras apparently enhances the affinity of PI3K for receptors; in the context of the model, this suggests that a ternary complex does indeed form, with the second step greatly enhanced through membrane localization and possibly allosteric effects. The apparent contribution of Ras to PI3K activation depends strongly on the quantities and binding affinities of the interacting molecules, which vary across different cell types and stimuli, and thus the model could be used to predict conditions under which PI3K signalling is sensitive to interventions targeting Ras.
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Affiliation(s)
- Harjeet Kaur
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695-7905, U.S.A
| | - Chang Shin Park
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695-7905, U.S.A
| | - Jodee M. Lewis
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695-7905, U.S.A
| | - Jason M. Haugh
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695-7905, U.S.A
- To whom correspondence should be addressed (email )
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155
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Iyer SS, Agrawal RS, Thompson CR, Thompson S, Barton JA, Kusner DJ. Phospholipase D1 Regulates Phagocyte Adhesion. THE JOURNAL OF IMMUNOLOGY 2006; 176:3686-96. [PMID: 16517737 DOI: 10.4049/jimmunol.176.6.3686] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Adhesion is a fundamental cellular response that is essential to the physiologic processes of development, differentiation, proliferation, and motility, as well as to the pathology of inflammation, transformation, and metastasis. Adhesion of phagocytic leukocytes is a critical modulator of antimicrobial and cytotoxic functions, including the respiratory burst, secretion, and apoptosis. Because phospholipase D (PLD) is linked to several signaling pathways implicated in these processes, we tested the hypothesis that PLD regulates phagocyte adhesion. Adhesion of primary human neutrophils and monocyte-derived macrophages to fibronectin was accompanied by marked stimulation of PLD activity. Similarly, adhesion of both human (PLB, THP-1) and murine (RAW) myeloid-macrophage cell lines to fibronectin, fibrinogen, collagen, or plastic resulted in significant activation of PLD. Stimulation of PLD activity was rapid and persisted for at least 90 min. Confocal microscopy indicated that PLD1 exhibited partial colocalization with actin filaments at the adherent interface, in proximity to the focal adhesion protein, paxillin. Reductions in PLD activity by chemical inhibitors or specific short-interfering RNA-induced knockdown of PLD1 resulted in significant inhibition of phagocyte adhesion and was accompanied by reductions in total cellular F-actin. These data support the hypotheses that adhesion stimulates PLD activity, and that PLD1 regulates the initial stages of phagocyte adhesion. Stimulation of PLD activity may promote adhesion-dependent phagocyte effector responses.
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Affiliation(s)
- Shankar S Iyer
- Inflammation Program, Division of Infectious Diseases, Department of Internal Medicine, University of Iowa Carver College of Medicine, 2501 Crosspark Road, Iowa City, IA 52242, USA
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156
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CHU CHARLEENT, ZHU JIANHUI. Subcellular Compartmentalization of P-ERKs in the Lewy Body Disease Substantia Nigra. Ann N Y Acad Sci 2006. [DOI: 10.1111/j.1749-6632.2003.tb07486.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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157
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Abstract
The mitogen-activated protein kinase (MAPK) signaling pathway is activated in response to a variety of extracellular stimuli such as growth factor stimulation. The best-characterized MAPK pathway involves the sequential activation of Raf, MEK and ERK proteins, capable of regulating the gene expression required for cell proliferation. Binding to specific lipids can regulate both the subcellular localization of these MAPK signaling proteins as well as their kinase activities. More recently it has become increasingly clear that the majority of MAPK signaling takes place intracellularly on endosomes and that the perturbation of endocytic pathways has dramatic effects on the MAPK pathway. This review highlights the direct effects of lipids on the localization and regulation of MAPK pathway proteins. In addition, the indirect effects lipids have on MAPK signaling via their regulation of endocytosis and the biophysical properties of different membrane lipids as a result of growth factor stimulation are discussed. The ability of a protein to bind to both lipids and proteins at the same time may act like a "ZIP code" to target that protein to a highly specific microlocation and could also allow a protein to be "handed off" to maintain tight control over its binding partners and location.
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Affiliation(s)
- Deborah H Anderson
- Cancer Research Unit, Health Research Division, Saskatchewan Cancer Agency, 20 Campus Drive, Saskatoon, Sask., Canada S7N 4H4.
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158
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Abstract
Rab proteins are small GTPases involved in the regulation of vesicular membrane traffic. Research done in the past years has demonstrated that some of these proteins are under the control of signal transduction pathways. Still, several recent papers point out to a new unexpected role for this family of Ras-related proteins, as potential regulators of intracellular signaling pathways. In particular, several evidence indicate that members of the Rab family of small GTPases, through their effectors, are key molecules participating to the regulation of numerous signal transduction pathways profoundly influencing cell proliferation, cell nutrition, innate immune response, fragmentation of compartments during mitosis and apoptosis. Even more surprisingly, direct involvement of Rab proteins in signaling to the nucleus has been demonstrated. This review will focus on aspects of Rab proteins function connected to signal transduction and, in particular, connections between membrane traffic and other cell pathways will be examined.
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Affiliation(s)
- Cecilia Bucci
- Dipartimento di Scienze e Tecnologie Biologiche ed Ambientali, Università di Lecce, Via Provinciale Monteroni, 73100 Lecce, Italy.
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159
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Abstract
Diacylglycerol kinases (DGKs) attenuate diacylglycerol signaling by converting this lipid to phosphatidic acid (PA). The nine mammalian DGKs that have been identified are widely expressed, but each isoform has a unique tissue and subcellular distribution. Their kinase activity is regulated by mechanisms that modify their access to diacylglycerol, directly affect their kinase activity, or alter their ability to bind to other proteins. In many cases, these enzymes regulate the activity of proteins that are modulated by either diacylglycerol or PA. Experiments using cultured cells and model organisms have demonstrated that DGKs have prominent roles in neuronal transmission, lymphocyte signaling, and carcinogenesis.
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Affiliation(s)
- Matthew K Topham
- Department of Internal Medicine, The Huntsman Cancer Institute, University of Utah, 2000 Circle of Hope, Salt Lake City, UT 84112-5550, USA.
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160
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Bonham L, Leung DW, White T, Hollenback D, Klein P, Tulinsky J, Coon M, de Vries P, Singer JW. Lysophosphatidic acid acyltransferase-beta: a novel target for induction of tumour cell apoptosis. Expert Opin Ther Targets 2005; 7:643-61. [PMID: 14498826 DOI: 10.1517/14728222.7.5.643] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Phosphatidic acid (PA) is a component of cellular membranes that is also a mediator of certain cell signalling functions associated with oncogenesis. These include ras/raf/Erk and Akt/mTor [1-3]. The authors have investigated whether it would be possible to interrupt these known oncogenic pathways through the inhibition of lysophosphatidic acid acyltransferase (LPAAT), an enzyme that catalyses the biosynthesis of PA. The expression and activity of the LPAAT-beta isoform are elevated in human tumours, and the respective gene displays transforming capacity when overexpressed in vitro. Inhibition by either genetic means or by isoform-specific small molecules results in a block to cell signalling pathways and apoptosis. Furthermore, the small-molecule inhibitors of LPAAT-beta are not cytotoxic to a number of normal cell types, including primary bone marrow progenitors, indicating a differential dependence of tumour cells on LPAAT-beta function. These discoveries indicate that LPAAT-beta represents a potential novel cancer therapy target.
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MESH Headings
- Acylation/drug effects
- Acyltransferases/antagonists & inhibitors
- Acyltransferases/genetics
- Acyltransferases/physiology
- Animals
- Antineoplastic Agents/pharmacology
- Antineoplastic Agents/therapeutic use
- Apoptosis/drug effects
- Carcinoma, Lewis Lung/drug therapy
- Cell Division/drug effects
- Cell Division/physiology
- Cell Line, Tumor/drug effects
- Cell Transformation, Neoplastic
- Chromosomes, Human, Pair 9/genetics
- Drug Design
- Drug Evaluation, Preclinical
- Genes, ras
- Humans
- Hydrocarbons, Halogenated/pharmacology
- Hydrocarbons, Halogenated/therapeutic use
- Lung Neoplasms/drug therapy
- Mice
- Neoplasm Proteins/antagonists & inhibitors
- Neoplasm Proteins/physiology
- Neoplasms/drug therapy
- Neoplasms/pathology
- Phosphatidic Acids/physiology
- Protein Conformation
- Protein Processing, Post-Translational/drug effects
- Signal Transduction/drug effects
- Signal Transduction/physiology
- Triazines/pharmacology
- Triazines/therapeutic use
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Affiliation(s)
- Lynn Bonham
- Cell Therapeutics, Inc., 201 Elliott Avenue West, Suite 400, Seattle, WA 98119, USA.
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161
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Zouwail S, Pettitt T, Dove S, Chibalina M, Powner D, Haynes L, Wakelam M, Insall R. Phospholipase D activity is essential for actin localization and actin-based motility in Dictyostelium. Biochem J 2005; 389:207-14. [PMID: 15769249 PMCID: PMC1184553 DOI: 10.1042/bj20050085] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
PLD (phospholipase D) activity catalyses the generation of the lipid messenger phosphatidic acid, which has been implicated in a number of cellular processes, particularly the regulation of membrane traffic. In the present study, we report that disruption of PLD signalling causes unexpectedly profound effects on the actin-based motility of Dictyostelium. Cells in which PLD activity is inhibited by butan-1-ol show a complete loss of actin-based structures, accompanied by relocalization of F-actin into small clusters, and eventually the nucleus, without a visible fall in levels of F-actin. Addition of exogenous phosphatidic acid reverses the effects of butan-1-ol, confirming that these effects are caused by inhibition of PLD. Loss of motility correlates with complete inhibition of endocytosis and a reduction in phagocytosis. Inhibition of PLD caused a major decrease in the synthesis of PtdIns(4,5)P2, which could again be reversed by exogenously applied phosphatidic acid. Thus the essential role of PLD signalling in both motility and endocytosis appears to be mediated directly via regulation of PtdIns(4)P kinase activity. This implies that localized PLD-regulated synthesis of PtdIns(4,5)P2 is essential for Dictyostelium actin function.
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Affiliation(s)
- Soha Zouwail
- *School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, U.K
| | - Trevor R. Pettitt
- †Cancer Research UK Institute for Cancer Studies, University of Birmingham, Edgbaston, Birmingham B15 2TT, U.K
| | - Stephen K. Dove
- *School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, U.K
| | | | - Dale J. Powner
- †Cancer Research UK Institute for Cancer Studies, University of Birmingham, Edgbaston, Birmingham B15 2TT, U.K
| | - Lee Haynes
- †Cancer Research UK Institute for Cancer Studies, University of Birmingham, Edgbaston, Birmingham B15 2TT, U.K
| | - Michael J. O. Wakelam
- †Cancer Research UK Institute for Cancer Studies, University of Birmingham, Edgbaston, Birmingham B15 2TT, U.K
| | - Robert H. Insall
- *School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, U.K
- To whom correspondence should be addressed (email )
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162
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Kooijman EE, Carter KM, van Laar EG, Chupin V, Burger KNJ, de Kruijff B. What Makes the Bioactive Lipids Phosphatidic Acid and Lysophosphatidic Acid So Special? Biochemistry 2005; 44:17007-15. [PMID: 16363814 DOI: 10.1021/bi0518794] [Citation(s) in RCA: 132] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Phosphatidic acid and lysophosphatidic acid are minor but important anionic bioactive lipids involved in a number of key cellular processes, yet these molecules have a simple phosphate headgroup. To find out what is so special about these lipids, we determined the ionization behavior of phosphatidic acid (PA) and lysophosphatidic acid (LPA) in extended (flat) mixed lipid bilayers using magic angle spinning 31P NMR. Our data show two surprising results. First, despite identical phosphomonoester headgroups, LPA carries more negative charge than PA when present in a phosphatidylcholine bilayer. Dehydroxy-LPA [1-oleoyl-3-(phosphoryl)propanediol] behaves in a manner identical to that of PA, indicating that the difference in negative charge between LPA and PA is caused by the hydroxyl on the glycerol backbone of LPA and its interaction with the phosphomonoester headgroup. Second, deprotonation of phosphatidic acid and lysophosphatidic acid was found to be strongly stimulated by the inclusion of phosphatidylethanolamine in the bilayer, indicating that lipid headgroup charge depends on local lipid composition and will vary between the different subcellular locations of (L)PA. Our findings can be understood in terms of a hydrogen bond formed within the phosphomonoester headgroup of (L)PA and its destabilization by competing intra- or intermolecular hydrogen bonds. We propose that this hydrogen bonding property of (L)PA is involved in the various cellular functions of these lipids.
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Affiliation(s)
- Edgar E Kooijman
- Department of Biochemistry of Membranes, Bijvoet Center, Institute of Biomembranes, Utrecht University, Utrecht, The Netherlands.
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163
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Zhang Y, Kanaho Y, Frohman MA, Tsirka SE. Phospholipase D1-promoted release of tissue plasminogen activator facilitates neurite outgrowth. J Neurosci 2005; 25:1797-805. [PMID: 15716416 PMCID: PMC6725938 DOI: 10.1523/jneurosci.4850-04.2005] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Temporal lobe epilepsy (TLE) is the most common form of epilepsy, affecting approximately 1-2% of the population. Seizure events resulting from TLE are characterized by aberrant hippocampal mossy fiber sprouting and plastic responses that affect brain function. Seizure susceptibility is modulated by the enzyme tissue plasminogen activator (tPA), the normal physiological role of which includes promotion of synaptic reorganization in the mossy fiber pathway by initiating a proteolytic cascade that cleaves extracellular matrix components and influences neurite extension. tPA is concentrated at and selectively secreted from growth cones during excitatory events. However, the mechanisms underlying tPA release during seizure-induced synaptogenesis are not well understood. We examine here potential roles for the signaling enzyme phospholipase D1 (PLD1), which promotes regulated exocytosis in non-CNS cell types, and which we previously demonstrated increases in expression in hippocampal neurons during seizure-induced mossy fiber sprouting. We now show that overexpression of wild-type PLD1 in cultured neurons promotes tPA release and tPA-dependent neurite extension, whereas overexpression of an inactive PLD1 allele or pharmacological inhibition of PLD1 inhibits tPA release. Similarly, viral delivery of wild-type PLD1 into the hippocampus facilitates tPA secretion and mossy fiber sprouting in a seizure-inducing model, whereas the inactive PLD1 allele inhibits tPA release and elicits blunted and abnormal mossy fiber extension similar to that observed for tPA-/- mice. Together, these findings secretion and thus mossy fiber extension in the setting of elevated suggest that PLD1 functions endogenously to regulate tPA-/- neuronal stimulation, such as that seen in TLE.
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Affiliation(s)
- Yan Zhang
- Program in Molecular and Cellular Pharmacology, Department of Pharmacological Sciences, University Medical Center at Stony Brook, Stony Brook, New York 11794, USA
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164
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Lee JS, Kim JH, Jang IH, Kim HS, Han JM, Kazlauskas A, Yagisawa H, Suh PG, Ryu SH. Phosphatidylinositol (3,4,5)-trisphosphate specifically interacts with the phox homology domain of phospholipase D1 and stimulates its activity. J Cell Sci 2005; 118:4405-13. [PMID: 16179605 DOI: 10.1242/jcs.02564] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
Phospholipase D (PLD), which catalyzes the hydrolysis of phosphatidylcholine to phosphatidic acid and choline, plays key roles in cellular signal transduction by mediating extracellular stimuli including hormones, growth factors, neurotransmitters, cytokines and extracellular matrix molecules. The molecular mechanisms by which domains regulate the activity of PLD - especially the phox homology (PX) domain - have not been fully elucidated. In this study, we have examined the properties of the PX domains of PLD1 and PLD2 in terms of phosphoinositide binding and PLD activity regulation. Interestingly, the PX domain of PLD1, but not that of PLD2, was found to specifically interact with phosphatidylinositol (3,4,5)-trisphosphate (PtdIns(3,4,5)P3). We found that mutation of the conserved arginine at position 179 of the PLD1 PX domain to lysine or to alanine (R179A or R179K, respectively) disrupts PtdIns(3,4,5)P3 binding. In NIH-3T3 cells, the EGFP-PLD1 PX wild-type domain, but not the two mutants, localized to the plasma membrane after 5-minute treatment with platelet-derived growth factor (PDGF). The enzymatic activity of PLD1 was stimulated by adding PtdIns(3,4,5)P3 in vitro. Treatment with PDGF resulted in the significant increase of PLD1 activity and phosphorylation of the downstream extracellular signal-regulated kinases (ERKs), which was blocked by pre-treatment of HEK 293 cells with phosphoinositide 3-kinase (PI3K) inhibitor after the endogenous PLD2 had been depleted by siRNA specific for PLD2. Nevertheless, both PLD1 mutants (which cannot interact with PtdIns(3,4,5)P3) did not respond to treatment with PDGF. Moreover, PLD1 was activated in HepG2 cells stably expressing the Y40/51 mutant of PDGF receptor that is required for the binding with PI3K. Our results suggest that the PLD1 PX domain enables PLD1 to mediate signal transduction via ERK1/2 by providing a direct binding site for PtdIns(3,4,5)P3 and by activating PLD1.
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Affiliation(s)
- Jun Sung Lee
- Division of Molecular and Life Science, Pohang University of Science and Technology, Pohang 790-784, Korea
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165
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Testerink C, Munnik T. Phosphatidic acid: a multifunctional stress signaling lipid in plants. TRENDS IN PLANT SCIENCE 2005; 10:368-75. [PMID: 16023886 DOI: 10.1016/j.tplants.2005.06.002] [Citation(s) in RCA: 187] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2005] [Revised: 04/22/2005] [Accepted: 06/28/2005] [Indexed: 05/03/2023]
Abstract
Phosphatidic acid (PA) has only recently been identified as an important signaling molecule in both plants and animals. Nonetheless, it already promises to rival the importance of the classic second messengers Ca(2+) and cAMP. In plants, its formation is triggered in response to various biotic and abiotic stress factors, including pathogen infection, drought, salinity, wounding and cold. In general, PA signal production is fast (minutes) and transient. Recently, our understanding of the role of PA formation in stress responses as a result of phospholipases C and D activity has greatly increased. Moreover, the first protein targets of PA have been identified. Based on this recent work, potential mechanisms by which PA provokes downstream effects are emerging.
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Affiliation(s)
- Christa Testerink
- Section of Plant Physiology, Swammerdam Institute for Life Sciences, University of Amsterdam, The Netherlands
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166
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Chauhan V, Sheikh AM, Chauhan A, Spivack WD, Fenko MD, Malik MN. Regulation of high molecular weight bovine brain neutral protease by phospholipids in vitro. Mol Cell Biochem 2005; 272:145-9. [PMID: 16010981 DOI: 10.1007/s11010-005-6915-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
The activity of the heat stable, glycosylated high molecular weight bovine brain neutral protease (HMW protease) is differentially regulated by phospholipids. While phosphatidylcholine (PC), phosphatidylserine (PS) and phosphatidic acid (PA) had only marginal stimulatory effect (40-75%) on the activity of HMW protease, lysophoshatidylcholine (lysoPC) and lysophosphatidic acid (lysoPA) activated the enzyme by more than two-fold. Both lysoPC and lysoPA exhibited concentration-dependent saturation kinetics for the activation of HMW protease. Surprisingly, phosphoinositides (phosphatidylinositol, PI; phosphatidylinositol 4-phosphate, PIP; and phosphatidylinositol 4,5-bisphosphate, PIP2) modulated the activity of protease differently: activation of the enzyme was higher with PIP (90%) as compared to PI (21%), whereas PIP2 inhibited the enzyme (16%). The inhibition of the protease by PIP2 was concentration-dependent. During receptor-coupled cell activation, phospholipase A2 (PLA2) converts PC and PA to lysoPC and lysoPA, respectively; PI is converted to PIP2 by successive enzymatic phosphorylation by PI 4-kinase and PIP 5-kinase; and phospholipase C (PLC) degrades PIP2 to diacylglycerol and inositol 1,4,5-trisphosphate. Therefore, the data suggest that HMW protease may be coupled to cell signal transduction where PLA2, PI 4-kinase, PIP 5-kinase and PLC are involved.
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Affiliation(s)
- V Chauhan
- NYS Institute for Basic Research in Developmental Disabilities, 1050 Forest Hill Road, Staten Island, NY 10314, USA.
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167
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Pagel JM, Laugen C, Bonham L, Hackman RC, Hockenbery DM, Bhatt R, Hollenback D, Carew H, Singer JW, Press OW. Induction of Apoptosis Using Inhibitors of Lysophosphatidic Acid Acyltransferase- and Anti-CD20 Monoclonal Antibodies for Treatment of Human Non-Hodgkin's Lymphomas. Clin Cancer Res 2005; 11:4857-66. [PMID: 16000584 DOI: 10.1158/1078-0432.ccr-04-2352] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
PURPOSE Lysophosphatidic acid acyltransferase-beta (LPAAT-beta) is a transmembrane enzyme critical for the biosynthesis of phosphoglycerides whose product, phosphatidic acid, plays a key role in raf and AKT/mTor-mediated signal transduction. EXPERIMENTAL DESIGN LPAAT-beta may be a novel target for anticancer therapy, and, thus, we examined the effects of a series of inhibitors of LPAAT-beta on multiple human non-Hodgkin's lymphoma cell lines in vitro and in vivo. RESULTS We showed that five LPAAT-beta inhibitors at doses of 500 nmol/L routinely inhibited growth in a panel of human lymphoma cell lines in vitro by >90%, as measured by [3H]thymidine incorporation. Apoptotic effects of the LPAAT-beta inhibitors were evaluated either alone or in combination with the anti-CD20 antibody, Rituximab. The LPAAT-beta inhibitors induced caspase-mediated apoptosis at 50 to 100 nmol/L in up to 90% of non-Hodgkin's lymphoma cells. The combination of Rituximab and an LPAAT-beta inhibitor resulted in a 2-fold increase in apoptosis compared with either agent alone. To assess the combination of Rituximab and a LPAAT-beta inhibitor in vivo, groups of athymic mice bearing s.c. human Ramos lymphoma xenografts were treated with the LPAAT-beta inhibitor CT-32228 i.p. (75 mg/kg) daily for 5 d/wk x 4 weeks (total 20 doses), Rituximab i.p. (10 mg/kg) weekly x 4 weeks (4 doses total), or CT-32228 plus Rituximab combined. Treatment with either CT-32228 or Rituximab alone showed an approximate 50% xenograft growth delay; however, complete responses were only observed when the two agents were delivered together. CONCLUSIONS These data suggest that Rituximab, combined with a LPAAT-beta inhibitor, may provide enhanced therapeutic effects through apoptotic mechanisms.
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MESH Headings
- Acyltransferases/antagonists & inhibitors
- Acyltransferases/metabolism
- Alanine Transaminase/blood
- Animals
- Antibodies, Monoclonal/administration & dosage
- Antibodies, Monoclonal/adverse effects
- Antibodies, Monoclonal/pharmacology
- Antibodies, Monoclonal, Murine-Derived
- Antigens, CD20/immunology
- Antineoplastic Combined Chemotherapy Protocols/adverse effects
- Antineoplastic Combined Chemotherapy Protocols/therapeutic use
- Apoptosis/drug effects
- Aspartate Aminotransferases/blood
- Caspases/metabolism
- Cell Line, Tumor
- Dose-Response Relationship, Drug
- Enzyme Inhibitors/administration & dosage
- Enzyme Inhibitors/adverse effects
- Enzyme Inhibitors/pharmacology
- Humans
- Hydrocarbons, Halogenated/administration & dosage
- Hydrocarbons, Halogenated/pharmacology
- Injections, Intraperitoneal
- Lymphoma, Non-Hodgkin/drug therapy
- Lymphoma, Non-Hodgkin/pathology
- Mice
- Mice, Nude
- Mice, SCID
- Rituximab
- Specific Pathogen-Free Organisms
- Survival Analysis
- Thymidine/metabolism
- Time Factors
- Treatment Outcome
- Triazines/administration & dosage
- Triazines/pharmacology
- Tritium
- Xenograft Model Antitumor Assays
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Affiliation(s)
- John M Pagel
- Fred Hutchinson Cancer Research Center; Department of Medicine, University of Washington, Seattle, Washington 98109, USA.
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168
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Plowman SJ, Hancock JF. Ras signaling from plasma membrane and endomembrane microdomains. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2005; 1746:274-83. [PMID: 16039730 DOI: 10.1016/j.bbamcr.2005.06.004] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2005] [Revised: 05/30/2005] [Accepted: 06/10/2005] [Indexed: 11/29/2022]
Abstract
Ras proteins are compartmentalized by dynamic interactions with both plasma membrane microdomains and intracellular membranes. The mechanisms underlying Ras compartmentalization involve a series of protein/lipid, lipid/lipid and cytoskeleton interactions, resulting in the generation of discrete microdomains from which Ras operates. Segregation of Ras proteins to these different platforms regulates the formation of Ras signaling complexes and the generation of discrete signal outputs. This temporal and spatial modulation of Ras signal transduction provides a mechanism for the generation of different biological outcomes from different Ras isoforms, as well as flexibility in the signal output from a single activated isoform.
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Affiliation(s)
- S J Plowman
- Institute for Molecular Bioscience, University of Queensland, St. Lucia, QLD 4072, Australia
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169
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Kostenis E. Novel clusters of receptors for sphingosine-1-phosphate, sphingosylphosphorylcholine, and (lyso)-phosphatidic acid: new receptors for "old" ligands. J Cell Biochem 2005; 92:923-36. [PMID: 15258916 DOI: 10.1002/jcb.20092] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The (lyso)phospholipid mediators sphingosine-1-phosphate (S1P), lysophosphatidic acid (LPA), sphingosylphosphorylcholine (SPC), and phosphatidic acid (PA) regulate diverse cellular responses such as proliferation, survival and death, cytoskeletal rearrangements, cell motility, and differentiation among many others. Signaling is complex and many signaling events are mediated through the activation of cell surface seven transmembrane (7TM) G protein coupled receptors. Five high affinity receptors for S1P have been identified so far and named S1P(1, 2,3,4,5) (formerly referred to as endothelial differentiation gene (edg)1, 5, 3, 6, 8). Recently, the orphan receptor GPR63 was identified a low affinity S1P receptor structurally distant from the S1P(1-5) family. The orphan GPR3, 6, 12 cluster, phylogenetically related to the edg and melanocortin receptors appears to be subject to modulation by S1P and SPC although all three receptors are strong constitutive stimulators of the Galphas-adenylyl cyclase (AC) pathway and would not require additional ligand stimulation but rather inverse agonism to control activity. Ovarian cancer G protein coupled receptor 1 (OGR1) and GPR4, two structurally closely related receptors were assigned in functional and binding studies as high affinity molecular targets for SPC. Very recently, however, both OGR1 and GPR4 were described as receptors endowed with the ability to signal cells in response to protons. LPA exerts its biological effects through the activation of G protein coupled LPA(1-3) receptors (formerly referred to as edg2, 4, 7). A fourth high affinity LPA receptor has been identified: P2Y9 (GPR23) structurally related to nucleotide receptors and phylogenetically quite distant from the high affinity LPA(1-3) cluster. This review attempts to give an overview about the existing families of lysophosholipid receptors and the spectrum of lipid agonists they use as high or low affinity ligands to relay extracellular signals into intracellular responses. Recently deorphaned lipid receptors, within and outside the known lipid receptor clusters will receive particular attention.
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Affiliation(s)
- Evi Kostenis
- 7TM Pharma A/S, 3 Fremtidsvej, 2970 Hoersholm, Denmark.
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170
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Bollag WB, Zhong X, Dodd ME, Hardy DM, Zheng X, Allred WT. Phospholipase d signaling and extracellular signal-regulated kinase-1 and -2 phosphorylation (activation) are required for maximal phorbol ester-induced transglutaminase activity, a marker of keratinocyte differentiation. J Pharmacol Exp Ther 2005; 312:1223-31. [PMID: 15537826 DOI: 10.1124/jpet.104.075622] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Protein kinase C (PKC)-activating 12-O-tetradecanoylphorbol 13-acetate (TPA) stimulates phospholipase D (PLD) activity in primary mouse epidermal keratinocytes. PLD catalyzes the hydrolysis of phosphatidylcholine to yield phosphatidic acid (PA), which can be dephosphorylated to produce PKC-activating diacylglycerol. In the presence of small amounts of a primary alcohol, PLD can instead produce novel phosphatidylalcohols at the expense of PA and diacylglycerol. Here, we have demonstrated that inhibiting PLD signal generation with 1-butanol reduced TPA-stimulated transglutaminase activity, a marker of keratinocyte differentiation. On the other hand, the structurally related tertiary alcohol tert-butanol, which cannot be used by PLD, had no effect on TPA-induced transglutaminase activity. Since TPA activates all conventional and novel PKC isoforms directly, yet cannot overcome 1-butanol-mediated inhibition, this result suggests that PLD mediates its effects on transglutaminase activity (and keratinocyte differentiation) through an effector enzyme system distinct from the conventional or novel PKC isoenzymes. Data in the literature suggest that PA can recruit Raf-1 to the membrane, where it can be activated and initiate the mitogen-activated protein kinase cascade that culminates in activation of extracellular signal-regulated kinase (ERK)-1 and -2. Indeed, we found that inhibition of ERK-1/2 phosphorylation (activation) inhibited TPA-induced transglutaminase activity. However, inhibition of PLD-mediated signal generation had only a small effect on TPA-elicited ERK-1/2 phosphorylation (activation), whereas inhibition of ERK-1/2 did not affect PLD activation, suggesting that these two pathways likely operate largely in parallel. Thus, our results suggest the independent involvement of the PLD and ERK-1/2 pathways in mediating transglutaminase activity and keratinocyte differentiation.
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Affiliation(s)
- Wendy B Bollag
- Institute of Molecular Medicine and Genetics/CB-2803, Medical College of Georgia, 1120 15th St., Augusta, GA 30912-2630, USA.
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171
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Li HS, Stolz DB, Romero G. Characterization of Endocytic Vesicles Using Magnetic Microbeads Coated with Signalling Ligands. Traffic 2005; 6:324-34. [PMID: 15752137 DOI: 10.1111/j.1600-0854.2005.00274.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Iron microbeads coated with the protein ligands insulin and EGF (Fe-INS and Fe-EGF) were prepared. Examination of the traffic of these ligand-coated microbeads demonstrated their internalization via clathrin-coated vesicles. Using magnetic methods, we have purified vesicles derived from the endocytic pathway. Vesicles prepared by this method are essentially free of contamination with other endomembrane compartments. Examination of the vesicles derived from cells treated with Fe-INS beads demonstrated the presence of the components of the Ras/Erk cascade on their surface. We conclude that the coupling of the Erk-signalling cascade induced by insulin takes place on the surface of endocytic vesicles derived from the internalization of the insulin receptor.
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Affiliation(s)
- Hai-Sheng Li
- Department of Pharmacology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
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172
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Piper M, Salih S, Weinl C, Holt CE, Harris WA. Endocytosis-dependent desensitization and protein synthesis-dependent resensitization in retinal growth cone adaptation. Nat Neurosci 2005; 8:179-86. [PMID: 15643427 PMCID: PMC3682638 DOI: 10.1038/nn1380] [Citation(s) in RCA: 132] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2004] [Accepted: 11/10/2004] [Indexed: 11/09/2022]
Abstract
It has been proposed that growth cones navigating through gradients adapt to baseline concentrations of guidance cues. This adaptation process is poorly understood. Using the collapse assay, we show that adaptation in Xenopus laevis retinal growth cones to the guidance cues Sema3A or netrin-1 involves two processes: a fast, ligand-specific desensitization that occurs within 2 min of exposure and is dependent on endocytosis, and a slower, ligand-specific resensitization, which occurs within 5 min and is dependent upon protein synthesis. These two phases of adaptation allow retinal axons to adjust their range of sensitivity to specific guidance cues.
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Affiliation(s)
- Michael Piper
- Department of Anatomy, University of Cambridge, Downing Street, Cambridge CB2 3DY, United Kingdom
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173
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Zambonelli C, Roberts MF. Non-HKD Phospholipase D Enzymes: New Players in Phosphatidic Acid Signaling? ACTA ACUST UNITED AC 2005; 79:133-81. [PMID: 16096028 DOI: 10.1016/s0079-6603(04)79003-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Affiliation(s)
- Carlo Zambonelli
- Merkert Chemistry Center, Boston College, Chestnut Hill, Massachusetts 02467, USA
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174
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Komati H, Naro F, Mebarek S, De Arcangelis V, Adamo S, Lagarde M, Prigent AF, Némoz G. Phospholipase D is involved in myogenic differentiation through remodeling of actin cytoskeleton. Mol Biol Cell 2004; 16:1232-44. [PMID: 15616193 PMCID: PMC551488 DOI: 10.1091/mbc.e04-06-0459] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
We investigated the role of phospholipase D (PLD) and its product phosphatidic acid (PA) in myogenic differentiation of cultured L6 rat skeletal myoblasts. Arginine-vasopressin (AVP), a differentiation inducer, rapidly activated PLD in a Rho-dependent way, as shown by almost total suppression of activation by C3 exotoxin pretreatment. Addition of 1-butanol, which selectively inhibits PA production by PLD, markedly decreased AVP-induced myogenesis. Conversely, myogenesis was potentiated by PLD1b isoform overexpression but not by PLD2 overexpression, establishing that PLD1 is involved in this process. The expression of the PLD isoforms was differentially regulated during differentiation. AVP stimulation of myoblasts induced the rapid formation of stress fiber-like actin structures (SFLSs). 1-Butanol selectively inhibited this response, whereas PLD1b overexpression induced SFLS formation, showing that it was PLD dependent. Endogenous PLD1 was located at the level of SFLSs, and by means of an intracellularly expressed fluorescent probe, PA was shown to be accumulated along these structures in response to AVP. In addition, AVP induced a PLD-dependent neosynthesis of phosphatidylinositol 4,5-bisphosphate (PIP2), which also was accumulated along actin fibers. These data support the hypothesis that PLD participates in myogenesis through PA- and PIP2-dependent actin fiber formation.
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Affiliation(s)
- Hiba Komati
- Laboratoire de Physiopathologie des Lipides et Membranes, Institut National de la Santé et de la Recherche Médicale Unité 585, Institut National des Sciences Appliquées de Lyon, 69621 Villeurbanne, France
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175
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Mahon ES, Hawrysh AD, Chagpar RB, Johnson LM, Anderson DH. A-Raf associates with and regulates platelet-derived growth factor receptor signalling. Cell Signal 2004; 17:857-68. [PMID: 15763428 DOI: 10.1016/j.cellsig.2004.11.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2004] [Revised: 11/03/2004] [Accepted: 11/03/2004] [Indexed: 11/25/2022]
Abstract
Raf kinases are important intermediates in epidermal growth factor (EGF) and platelet-derived growth factor (PDGF) mediated activation of the mitogen-activated protein kinase (MAPK) pathway. In this report, we show that the A-Raf kinase is associated with activated EGF receptor complexes and with PDGF receptor (PDGFR) complexes independent of prior PDGF treatment. The ability of A-Raf to associate with receptor tyrosine kinases could provide a Ras-GTP-independent mechanism for the membrane localization of A-Raf. Expression of a partially activated A-Raf mutant resulted in decreased tyrosine phosphorylation of the PDGFR, specifically on Y857 (autophosphorylation site) and Y1021 (phospholipase Cgamma1 (PLCgamma1) binding site), but not the binding sites for other signalling proteins (Nck, phosphatidylinositol 3'-kinase (PI3K), RasGAP, Grb2, SHP). Activated A-Raf expression also altered the activation of PLCgamma1, and p85-associated PI3K. Thus, A-Raf can regulate PLCgamma1 signalling via a PDGFR-dependent mechanism and may also regulate PI3K signalling via a PDGFR-independent mechanism.
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Affiliation(s)
- Elizabeth S Mahon
- Department of Biochemistry, University of Saskatchewan, 107 Wiggins Ave., Saskatoon, Saskatchewan, Canada S7N 5E5
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176
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Lindsay AJ, McCaffrey MW. The C2 domains of the class I Rab11 family of interacting proteins target recycling vesicles to the plasma membrane. J Cell Sci 2004; 117:4365-75. [PMID: 15304524 DOI: 10.1242/jcs.01280] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The Rab11 family of interacting proteins (Rab11-FIP) is a recently identified protein family composed of, to date, six members that interact with Rab11. They all share a highly homologous Rab11-binding domain (RBD) at their C-termini. However, apart from the RBD, they vary in their domain organization. Rab11-FIP3 and Rab11-FIP4 possess an ezrin-radixin-moesin (ERM) domain in their C-terminal half and EF hands in their N-terminal region. They have been termed class II Rab11-FIPs. The class I Rab11-FIPs, Rab coupling protein (RCP), Rip11 and Rab11-FIP2, each have a C2 phospholipid-binding domain near their N-termini. Although they are still membrane associated, truncation mutants of the class I Rab11-FIPs that lack their C2 domains display an altered subcellular distribution in vivo, indicating that this domain plays an important role in specifying their correct intracellular localization. To determine the phospholipids to which they bind, a protein phospholipid overlay assay was performed. Our results indicate that the class-I Rab11-FIPs bind preferentially to phosphatidylinositol-(3,4,5)-trisphosphate [PtdIns(3,4,5)P3] and the second messenger phosphatidic acid. Stimulation of PtdIns(3,4,5)P3 or phosphatidic acid synthesis results in the translocation of the Rab11-FIPs from a perinuclear location to the periphery of the cell. By contrast, the transferrin receptor does not translocate to the plasma membrane under these conditions. This translocation is dependent on the presence of the C2 domain, because class I Rab11-FIP green-fluorescent-protein fusions that lack the C2 domain cannot translocate to the plasma membrane. We propose that the C2 domains of the class I Rab11-FIPs function to target these proteins to `docking sites' in the plasma membrane that are enriched in PtdIns(3,4,5)P3 and phosphatidic acid.
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Affiliation(s)
- Andrew J Lindsay
- Molecular Cell Biology Laboratory, Department of Biochemistry, Biosciences Institute, University College Cork, Cork, Ireland
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177
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Choi JH, Hong WP, Kim MJ, Kim JH, Ryu SH, Suh PG. Sorting nexin 16 regulates EGF receptor trafficking by phosphatidylinositol-3-phosphate interaction with the Phox domain. J Cell Sci 2004; 117:4209-18. [PMID: 15292396 DOI: 10.1242/jcs.01233] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Sorting nexins (SNXs) containing the Phox (PX) domain are implicated in the regulation of membrane trafficking and sorting processes of epithelial growth factor receptor (EGFR). In this study, we investigated whether SNX16 regulates EGF-induced cell signaling by regulating EGFR trafficking. SNX16 is localized in early and recycling endosomes via its PX domain. Mutation of the PX domain disrupted the association between SNX16 and phosphatidylinositol 3-phosphate [PtdIns(3)P]. Treatment with wortmannin, a PtdIns 3-kinase inhibitor, abolished the endosomal localization of SNX16, suggesting that the intracellular localization of SNX16 is regulated by PtdIns 3-kinase activity. SNX16 was found to associate with EGFR after stimulation with EGF in COS-7 cells. Moreover, overexpression of SNX16 increased the rate of EGF-induced EGFR degradation and inhibited the EGF-induced up-regulation of ERK and serum response element (SRE). In addition, mutation in the PX domain significantly blocked the inhibitory effect of SNX16 on EGF-induced activation of ERK and SRE. From these results, we suggest that SNX16 directs the sorting of EGFR to the endosomal compartment and thus regulates EGF-induced cell signaling.
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Affiliation(s)
- Jang Hyun Choi
- Division of Molecular and Life Science, Pohang University of Science and Technology, San 31, Hojadong, Pohang, Kyungbuk 790-784, Republic of Korea
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178
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Delon C, Manifava M, Wood E, Thompson D, Krugmann S, Pyne S, Ktistakis NT. Sphingosine kinase 1 is an intracellular effector of phosphatidic acid. J Biol Chem 2004; 279:44763-74. [PMID: 15310762 DOI: 10.1074/jbc.m405771200] [Citation(s) in RCA: 154] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Sphingosine kinase 1 (SK1) phosphorylates sphingosine to generate sphingosine 1-phosphate (S1P). Because both substrate and product of the enzyme are potentially important signaling molecules, the regulation of SK1 is of considerable interest. We report that SK1, which is ordinarily a cytosolic enzyme, translocates in vivo and in vitro to membrane compartments enriched in phosphatidic acid (PA), the lipid product of phospholipase D. This translocation depends on direct interaction of SK1 with PA, because recombinant purified enzyme shows strong affinity for pure PA coupled to Affi-Gel. The SK1-PA interaction maps to the C terminus of SK1 and is independent of catalytic activity or of the diacylglycerol kinase-like domain of the enzyme. Thus SK1 constitutes a novel, physiologically relevant PA effector.
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Affiliation(s)
- Christine Delon
- Department of Signalling, Babraham Institute, Cambridge CB2 4AT, United Kingdom
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179
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Hassan S, Dobner PR, Carraway RE. Involvement of MAP-kinase, PI3-kinase and EGF-receptor in the stimulatory effect of Neurotensin on DNA synthesis in PC3 cells. ACTA ACUST UNITED AC 2004; 120:155-66. [PMID: 15177934 DOI: 10.1016/j.regpep.2004.03.004] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2003] [Revised: 03/02/2004] [Accepted: 03/09/2004] [Indexed: 10/26/2022]
Abstract
The mechanism by which neurotensin (NT) promotes the growth of prostate cancer epithelial cells is not yet defined. Here, androgen-independent PC3 cells, which express high levels of the type 1 NT-receptor (NTR1), are used to examine the involvement of epidermal growth factor receptor (EGFR), mitogen-activated protein kinases (ERK, SAPK/JNK and p38), PI3 kinase and PKC in the mitogenic effect of NT. NT dose dependently (0.1-30 nM) enhanced phosphorylation of EGFR, ERK and Akt, reaching maximal levels within 3 min as measured by Western blotting. These effects were associated with an accumulation of EGF-like substance(s) in the medium (assayed by EGFR binding) and a 2-fold increase in DNA synthesis (assayed by [3H]thymidine incorporation). The DNA synthesis enhancement by NT was non-additive with that of EGF. The NT-induced stimulation of EGFR/ERK/Akt phosphorylation and DNA synthesis was inhibited by EGFR-tyrosine kinase inhibitors (AG1478, PD153035), metallo-endopeptidase inhibitor phosphoramidon and by heparin, but not by neutralizing anti-EGF antibody. Thus, transactivation of EGFR by NT involved heparin-binding EGF (HB-EGF or amphiregulin) rather than EGF. The effects of NT on EGFR/ERK/Akt activation and DNA synthesis were attenuated by PLC-inhibitor (U73122), PKC-inhibitors (bisindolylmaleimide, staurosporine, rottlerin), MEK inhibitor (U0126) and PI3 kinase inhibitors (wortmannin, LY 294002). We conclude that NT stimulated mitogenesis in PC3 cells by a PKC-dependent ligand-mediated transactivation of EGFR, which led to stimulation of the Raf-MEK-ERK pathway in a PI3 kinase-dependent manner.
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Affiliation(s)
- Sazzad Hassan
- Department of Cellular and Molecular Physiology, University of Massachusetts Medical School, 55 Lake Avenue North, Worcester 01655-0127, USA
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180
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Testerink C, Dekker HL, Lim ZY, Johns MK, Holmes AB, Koster CG, Ktistakis NT, Munnik T. Isolation and identification of phosphatidic acid targets from plants. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2004; 39:527-36. [PMID: 15272872 DOI: 10.1111/j.1365-313x.2004.02152.x] [Citation(s) in RCA: 145] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Phosphatidic acid (PA) is emerging as an important lipid signalling molecule. In plants, it is implicated in various stress-signalling pathways and is formed in response to wounding, osmotic stress, cold stress, pathogen elicitors, Nod factors, ethylene and abscisic acid. How PA exerts its effects is still unknown, mainly because of the lack of characterized PA targets. In an approach to isolate such targets we have used PA-affinity chromatography. Several PA-binding proteins were present in the soluble fraction of tomato and Arabidopsis cells. Using mass spectrometric analysis, several of these proteins, including Hsp90, 14-3-3 proteins, an SnRK2 serine/threonine protein kinase and the PP2A regulatory subunit RCN1 could be identified. As an example, the binding of one major PA-binding protein, phosphoenolpyruvate carboxylase (PEPC), was characterized further. Competition experiments with different phospholipids confirmed specificity for PA. Hypo-osmotic treatment of the cells increased the amount of PEPC that bound the PA beads without increasing the absolute amount of PEPC. This suggests that PEPC's affinity for PA had increased. The work shows that PA-affinity chromatography/mass spectrometry is an effective way to isolate and identify PA-binding proteins from plants.
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Affiliation(s)
- Christa Testerink
- Section of Plant Physiology, Swammerdam Institute for Life Sciences, University of Amsterdam, Kruislaan 318, 1098 SM Amsterdam, the Netherlands
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181
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Kostenis E. A glance at G-protein-coupled receptors for lipid mediators: a growing receptor family with remarkably diverse ligands. Pharmacol Ther 2004; 102:243-57. [PMID: 15246248 DOI: 10.1016/j.pharmthera.2004.04.005] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
A plethora of lipid-like molecules known to act as intracellular second messengers are now recognized to signal cells through plasma membrane 7 transmembrane G-protein-coupled receptors (GPCRs). This has been the result of a decade-long genetic hunt for novel sequences encoding 7 transmembrane receptor proteins and the efforts to pair novel sequences with biologically active substances of (partly) unknown molecular mechanism of action. Identification of novel GPCR ligand pairs represents the first step to shed more light into the mode of action of novel cellular signaling molecules in human health and disease and might represent a fruitful source for the development of new drugs, judged on the successful history of GPCR as drug targets. Since 2000, more than 16 reports became available on lipid mediators--as diverse as lysophospholipids, arachidonic acid metabolites, short-, medium-, and long-chain fatty acids as well as steroid-like molecules--exerting their effects as extracellular mediators via rhodopsin-like family GPCRs. These reports have opened new avenues for research in human lipid receptor physiology and pharmacology. Here, the current knowledge on the recently deorphanized lipid receptors, including their isolation, expression pattern, function, and possible physiological or pathological roles will be reviewed.
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Affiliation(s)
- Evi Kostenis
- 7TM Pharma A/S, 3 Fremtidsvej, 2970 Hoersholm, Denmark.
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182
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Lee YN, Lee HY, Kang HK, Kwak JY, Bae YS. Phosphatidic acid positively regulates LPS-induced differentiation of RAW264.7 murine macrophage cell line into dendritic-like cells. Biochem Biophys Res Commun 2004; 318:839-45. [PMID: 15147947 DOI: 10.1016/j.bbrc.2004.04.112] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2004] [Indexed: 11/30/2022]
Abstract
Phosphatidic acid (PA) is an important second messenger produced by the activation of numerous cell surface receptors. Recent data have suggested that PA regulates multiple cellular processes. In this study, we found that PA positively regulates the lipopolysaccharide (LPS)-induced differentiation of RAW264.7 murine macrophage cells into dendritic-like cells. Co-treatment of PA with LPS further increased dendritic cell surface marker expressions (CD80, CD86, CD40, MHC class I, and class II antigens) and reduced the phagocytic activity of LPS-treated cells. Moreover, PA up regulated allostimulatory activity and the secretion of IL-12 in LPS-treated RAW264.7 cells. Taken together, these data indicate that PA might play a role in the LPS-mediated differentiation of macrophage cells into dendritic-like cells.
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Affiliation(s)
- Youl-Nam Lee
- Medical Research Center for Cancer Molecular Therapy, Dong-A University, Busan 602-714, Republic of Korea
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183
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Zhang Y, Huang P, Du G, Kanaho Y, Frohman MA, Tsirka SE. Increased expression of two phospholipase D isoforms during experimentally induced hippocampal mossy fiber outgrowth. Glia 2004; 46:74-83. [PMID: 14999815 DOI: 10.1002/glia.10322] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Mammalian phospholipase D (PLD), a multifunctional signaling enzyme, has been reported to facilitate neurite outgrowth in cultured neurons. However, two mammalian isoforms have been found, PLD1 and PLD2, and it has not been determined which isoform is involved, or whether this in vitro phenomenon is relevant to neurite extension in vivo. Using confocal microscopy, we demonstrate that the PLDs are expressed by different cell types in the mouse brain: PLD1 by neurons, and PLD2 by astrocytes. Moreover, using a model of experimentally induced hippocampal mossy fiber sprouting, both isoforms were observed to increase dramatically in expression level along tracts of mossy fiber spouting, supporting the proposal that PLD plays a role in this process. Given that the two isoforms undertake unique molecular functions in cultured cells, our findings suggest that in vivo PLD1 and PLD2 may modulate neuronal plasticity via different pathways and cell types.
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Affiliation(s)
- Yan Zhang
- Department of Pharmacological Sciences, University Medical Center at Stony Brook, Stony Brook, New York 11794-8651, USA
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184
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Anthony RG, Henriques R, Helfer A, Mészáros T, Rios G, Testerink C, Munnik T, Deák M, Koncz C, Bögre L. A protein kinase target of a PDK1 signalling pathway is involved in root hair growth in Arabidopsis. EMBO J 2004; 23:572-81. [PMID: 14749726 PMCID: PMC1271803 DOI: 10.1038/sj.emboj.7600068] [Citation(s) in RCA: 212] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2003] [Accepted: 12/15/2003] [Indexed: 11/09/2022] Open
Abstract
Here we report on a lipid-signalling pathway in plants that is downstream of phosphatidic acid and involves the Arabidopsis protein kinase, AGC2-1, regulated by the 3'-phosphoinositide-dependent kinase-1 (AtPDK1). AGC2-1 specifically interacts with AtPDK1 through a conserved C-terminal hydrophobic motif that leads to its phosphorylation and activation, whereas inhibition of AtPDK1 expression by RNA interference abolishes AGC2-1 activity. Phosphatidic acid specifically binds to AtPDK1 and stimulates AGC2-1 in an AtPDK1-dependent manner. AtPDK1 is ubiquitously expressed in all plant tissues, whereas expression of AGC2-1 is abundant in fast-growing organs and dividing cells, and activated during re-entry of cells into the cell cycle after sugar starvation-induced G1-phase arrest. Plant hormones, auxin and cytokinin, synergistically activate the AtPDK1-regulated AGC2-1 kinase, indicative of a role in growth and cell division. Cellular localisation of GFP-AGC2-1 fusion protein is highly dynamic in root hairs and at some stages confined to root hair tips and to nuclei. The agc2-1 knockout mutation results in a reduction of root hair length, suggesting a role for AGC2-1 in root hair growth and development.
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Affiliation(s)
- Richard G Anthony
- School of Biological Sciences, Royal Holloway, University of London, Egham, Surrey, UK
| | - Rossana Henriques
- School of Biological Sciences, Royal Holloway, University of London, Egham, Surrey, UK
| | - Anne Helfer
- School of Biological Sciences, Royal Holloway, University of London, Egham, Surrey, UK
| | - Tamás Mészáros
- School of Biological Sciences, Royal Holloway, University of London, Egham, Surrey, UK
| | - Gabino Rios
- Max-Planck Institut für Züchtungsforschung Carl-von-Linné-Weg 10, Köln, Germany
| | - Christa Testerink
- Department of Plant Physiology, Swammerdam Institute for Life Sciences (SILS), University of Amsterdam, Netherlands
| | - Teun Munnik
- Department of Plant Physiology, Swammerdam Institute for Life Sciences (SILS), University of Amsterdam, Netherlands
| | - Maria Deák
- MRC Protein Phosphorylation Unit, University of Dundee, Dow Street, Dundee, UK
| | - Csaba Koncz
- Max-Planck Institut für Züchtungsforschung Carl-von-Linné-Weg 10, Köln, Germany
| | - László Bögre
- School of Biological Sciences, Royal Holloway, University of London, Egham, Surrey, UK
- School of Biological Sciences, Royal Holloway, University of London, Egham TW20 0EX, UK. Tel.: +44 1784 443407; Fax: +44 1784 434326; E-mail:
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185
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Du G, Huang P, Liang BT, Frohman MA. Phospholipase D2 localizes to the plasma membrane and regulates angiotensin II receptor endocytosis. Mol Biol Cell 2004; 15:1024-30. [PMID: 14718562 PMCID: PMC363061 DOI: 10.1091/mbc.e03-09-0673] [Citation(s) in RCA: 172] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Phospholipase D (PLD) is a key facilitator of multiple types of membrane vesicle trafficking events. Two PLD isoforms, PLD1 and PLD2, exist in mammals. Initial studies based on overexpression studies suggested that in resting cells, human PLD1 localized primarily to the Golgi and perinuclear vesicles in multiple cell types. In contrast, overexpressed mouse PLD2 was observed to localize primarily to the plasma membrane, although internalization on membrane vesicles was observed subsequent to serum stimulation. A recent report has suggested that the assignment of PLD2 to the plasma membrane is in error, because the endogenous isoform in rat secretory cells was imaged and found to be present primarily in the Golgi apparatus. We have reexamined this issue by using a monoclonal antibody specific for mouse PLD2, and find, as reported initially using overexpression studies, that endogenous mouse PLD2 is detected most readily at the plasma membrane in multiple cell types. In addition, we report that mouse, rat, and human PLD2 when overexpressed all similarly localize to the plasma membrane in cell lines from all three species. Finally, studies conducted using overexpression of wild-type active or dominant-negative isoforms of PLD2 and RNA interference-mediated targeting of PLD2 suggest that PLD2 functions at the plasma membrane to facilitate endocytosis of the angiotensin II type 1 receptor.
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Affiliation(s)
- Guangwei Du
- Department of Pharmacology and the Center for Developmental Genetics, University Medical Center at Stony Brook, Stony Brook, New York 11794-5140, USA
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186
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Zhu J, Guo F, Shelburne J, Watkins S, Chu CT. Localization of phosphorylated ERK/MAP kinases to mitochondria and autophagosomes in Lewy body diseases. Brain Pathol 2004; 13:473-81. [PMID: 14655753 PMCID: PMC1911206 DOI: 10.1111/j.1750-3639.2003.tb00478.x] [Citation(s) in RCA: 205] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
We previously found that sustained ERK activation contributes to toxicity elicited by the parkinsonian neurotoxin 6-hydroxydopamine. In addition, substantia nigra neurons from patients with incidental Lewy body disease, Parkinson disease (PD), and diffuse Lewy body dementia (DLB) display abnormal phospho-ERK accumulations in the form of discrete cytoplasmic granules. In this study, we investigated the subcellular localization of phospho-ERK immunoreactive granules using double label confocal microscopy and immuno-electron microscopy. A small percentage of phospho-ERK granules co-localized with the early endosome marker Rab5, but not with cathepsin D, 20S proteasome beta-subunit, or cytochrome P450 reductase. Phospho-ERK immunoreactivity was often associated with mitochondrial proteins (MnSOD, 60 kDa and 110 kDa mitochondrial antigens), and some vesicular-appearing phospho-ERK granules appeared to envelop enlarged mitochondria by confocal laser scanning microscopy. Ultrastructural immuno-gold studies revealed phospho-ERK labeling in mitochondria and in association with bundles of approximately 10 nm fibrils. Heavily labeled mitochondria were observed within autophagosomes. As mitochondrial pathology may play a pivotal role in Parkinson and other related neurodegenerative diseases, these studies suggest a potential interaction between dysfunctional mitochondria, autophagy, and ERK signaling pathways.
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Affiliation(s)
- Jian‐Hui Zhu
- Department of Pathology, Division of Neuropathology, University of Pittsburgh, Pa
| | - Fengli Guo
- Department of Cell Biology and Physiology, Center for Biologic Imaging, and the University of Pittsburgh, Pa
| | - John Shelburne
- Department of Pathology, Duke University and VA Medical Centers, Durham, NC
| | - Simon Watkins
- Department of Cell Biology and Physiology, Center for Biologic Imaging, and the University of Pittsburgh, Pa
| | - Charleen T. Chu
- Department of Pathology, Division of Neuropathology, University of Pittsburgh, Pa
- Pittsburgh Institute of Neurodegenerative Diseases, University of Pittsburgh, Pa
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187
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Barbieri MA, Ramkumar TP, Fernadez-Pol S, Chen PI, Stahl PD. Receptor Tyrosine Kinase Signaling and Trafficking—Paradigms Revisited. Curr Top Microbiol Immunol 2004. [DOI: 10.1007/978-3-540-69494-6_1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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188
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Abstract
The lipid matrix of biological membranes is composed of a complex mixture of polar lipids. It has been estimated that more than 600 distinct molecular species of lipid are constituents of biological membranes. This rather remarkable feature raises the questions of why such complexity is required when barrier properties and many protein functions can be reconstituted with relatively simple lipid systems. Secondly, the molecular species composition of morphologically distinct membranes appears to be preserved within fairly narrow limits. The biochemical mechanism(s) responsible for this homeostasis are not fully understood. This review examines the origin of membrane lipid complexity, the methods that are currently employed to measure and detect lipid molecular species and the biochemical reactions associated with the turnover of membrane lipids in resting and stimulated cells.
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Affiliation(s)
- Claude Wolf
- Biochemistry Department, Mass Spectrometry Laboratory, INSERM U 538, Faculté de Médecine Saint Antoine, Paris 75012, France
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189
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Hekman M, Wiese S, Metz R, Albert S, Troppmair J, Nickel J, Sendtner M, Rapp UR. Dynamic changes in C-Raf phosphorylation and 14-3-3 protein binding in response to growth factor stimulation: differential roles of 14-3-3 protein binding sites. J Biol Chem 2003; 279:14074-86. [PMID: 14688280 DOI: 10.1074/jbc.m309620200] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Phosphorylation events play a crucial role in Raf activation. Phosphorylation of serines 259 and 621 in C-Raf and serines 364 and 728 in B-Raf has been suggested to be critical for association with 14-3-3 proteins. To study the functional consequences of Raf phosphorylations at these positions, we developed and characterized phosphospecific antibodies directed against 14-3-3 binding epitopes: a monoclonal phosphospecific antibody (6B4) directed against pS621 and a polyclonal antibody specific for B-Raf-pS364 epitope. Although 6B4 detected both C- and B-Raf in Western blots, it specifically recognizes the native form of C-Raf but not B-Raf. Contrary to B-Raf, a kinase-dead mutant of C-Raf was found to be only poorly phosphorylated in the Ser-621 position. Moreover, serine 259 to alanine mutation prevented the Ser-621 phosphorylation suggesting an interdependence between these two 14-3-3 binding domains. Direct C-Raf.14-3-3 binding studies with purified proteins combined with competition assays revealed that the 14-3-3 binding domain surrounding pS621 represents the high affinity binding site, whereas the pS259 epitope mediates lower affinity binding. Raf isozymes differ in their 14-3-3 association rates. The time course of endogenous C-Raf activation in mammalian cells by nerve growth factor (NGF) has been examined using both phosphospecific antibodies directed against 14-3-3 binding sites (6B4 and anti-pS259) as well as phosphospecific antibodies directed against the activation domain (anti-pS338 and anti-pY340/pY341). Time course of Ser-621 phosphorylation, in contrast to Ser-259 phosphorylation, exhibited unexpected pattern reaching maximal phosphorylation within 30 s of NGF stimulation. Phosphorylation of tyrosine 340/341 reached maximal levels subsequent to Ser-621 phosphorylation and was coincident with emergence of kinase activity. Taken together, we found substantial differences between C-Raf.14-3-3 binding epitopes pS259 and pS621 and visualized for the first time the sequence of the essential C-Raf phosphorylation events in mammalian cells in response to growth factor stimulation.
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Affiliation(s)
- Mirko Hekman
- Institute for Medical Radiation and Cell Research, University of Wuerzburg, 97078 Wuerzburg
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190
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Most P, Boerries M, Eicher C, Schweda C, Ehlermann P, Pleger ST, Loeffler E, Koch WJ, Katus HA, Schoenenberger CA, Remppis A. Extracellular S100A1 protein inhibits apoptosis in ventricular cardiomyocytes via activation of the extracellular signal-regulated protein kinase 1/2 (ERK1/2). J Biol Chem 2003; 278:48404-12. [PMID: 12960148 DOI: 10.1074/jbc.m308587200] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
S100A1 is a Ca2+-binding protein of the EF-hand type that belongs to the S100 protein family. It is specifically expressed in the myocardium at high levels and is considered to be an important regulator of cardiac contractility. Because the S100A1 protein is released into the extracellular space during ischemic myocardial injury, we examined the cardioprotective potential of the extracellular S100A1 protein on ventricular cardiomyocytes in vitro. In this report we show that extracellularly added S100A1 protein is endocytosed into the endosomal compartment of neonatal ventricular cardiomyocytes via a Ca2+-dependent clathrin-mediated process. S100A1 uptake protects neonatal ventricular cardiomyocytes from 2-deoxyglucose and oxidative stress-induced apoptosis in vitro. S100A1-mediated anti-apoptotic effects involve specific activation of the extracellular signal-regulated kinase 1/2 (ERK1/2) pro-survival pathway, including activation of phospholipase C, protein kinase C, mitogen-activated protein kinase kinase 1, and ERK1/2. In contrast, neither transsarcolemmal Ca2+ influx via the L-type channel nor protein kinase A activity seems to take part in the S100A1-mediated signaling pathway. In conclusion, this study provides evidence for the S100A1 protein serving as a novel cardioprotective factor in vitro. These findings warrant speculation that injury-dependent release of the S100A1 protein from cardiomyocytes may serve as an intrinsic mechanism to promote survival of the myocardium in vivo.
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Affiliation(s)
- Patrick Most
- Innere Medizin III, Universität Heidelberg, 69115 Heidelberg, Germany.
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191
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Ghosh S, Moore S, Bell RM, Dush M. Functional analysis of a phosphatidic acid binding domain in human Raf-1 kinase: mutations in the phosphatidate binding domain lead to tail and trunk abnormalities in developing zebrafish embryos. J Biol Chem 2003; 278:45690-6. [PMID: 12925535 DOI: 10.1074/jbc.m302933200] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Previously, we and others identified a 35-amino acid segment within human Raf-1 kinase that preferentially binds phosphatidic acid. The presence of phosphatidic acid was found to be necessary for the translocation of Raf-1 to the plasma membrane. We have now employed a combination of alanine-scanning and deletion mutagenesis to identify the critical amino acid residues in Raf-1 necessary for interaction with phosphatidic acid. Progressive mutations within a tetrapeptide motif (residues 398-401 of human Raf-1) reduced and finally eliminated binding of Raf-1 to phosphatidic acid. We then injected zebrafish embryos with RNA encoding wild-type Raf-1 kinase or a mutant version with triple alanine mutations in the tetrapeptide motif and followed the morphological fate of embryonic development. Embryos with mutant but not wild-type Raf-1 exhibited defects in posterior axis formation exemplified by bent trunk and tail structures. Molecular evidence for lack of signaling through mutated Raf-1 was obtained by aberrant in situ hybridization of the ntl (no tail) gene, which functions downstream of Raf-1. Our results demonstrate that a functional phosphatidate binding site is necessary for Raf-1 function in embryonic development.
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Affiliation(s)
- Sujoy Ghosh
- GlaxoSmithKline, Genetics Research, Research Triangle Park, North Carolina 27709, USA.
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192
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Harding A, Hsu V, Kornfeld K, Hancock JF. Identification of residues and domains of Raf important for function in vivo and in vitro. J Biol Chem 2003; 278:45519-27. [PMID: 12954633 DOI: 10.1074/jbc.m303106200] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Random mutagenesis and genetic screens for impaired Raf function in Caenorhabditis elegans were used to identify six loss-of-function alleles of lin-45 raf that result in a substitution of a single amino acid. The mutations were classified as weak, intermediate, and strong based on phenotypic severity. We engineered these mutations into the homologous residues of vertebrate Raf-1 and analyzed the mutant proteins for their underlying biochemical defects. Surprisingly, phenotype strength did not correlate with the catalytic activity of the mutant proteins. Amino acid substitutions Val-589 and Ser-619 severely compromised Raf kinase activity, yet these mutants displayed weak phenotypes in the genetic screen. Interestingly, this is because these mutant Raf proteins efficiently activate the MAPK (mitogen-activated protein kinase) cascade in living cells, a result that may inform the analysis of knockout mice. Equally intriguing was the observation that mutant proteins with non-functional Ras-binding domains, and thereby deficient in Ras-mediated membrane recruitment, displayed only intermediate strength phenotypes. This confirms that secondary mechanisms exist to couple Ras to Raf in vivo. The strongest phenotype in the genetic screens was displayed by a S508N mutation that again did not correlate with a significant loss of kinase activity or membrane recruitment by oncogenic Ras in biochemical assays. Ser-508 lies within the Raf-1 activation loop, and mutation of this residue in Raf-1 and the equivalent Ser-615 in B-Raf revealed that this residue regulates Raf binding to MEK. Further characterization revealed that in response to activation by epidermal growth factor, the Raf-S508N mutant protein displayed both reduced catalytic activity and aberrant activation kinetics: characteristics that may explain the C. elegans phenotype.
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Affiliation(s)
- Angus Harding
- Institute for Molecular Bioscience and Department of Molecular and Cellular Pathology, University of Queensland, Brisbane 4072, Australia
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193
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Abstract
Insulin-stimulated Glut-4 translocation is regulated through a complex pathway. Increasing attention is being paid to the role undertaken in this process by Phospholipase D, a signal transduction-activated enzyme that generates the lipid second-messenger phosphatidic acid. Phospholipase D facilitates Glut-4 translocation at potentially multiple steps in its outward movement. Current investigation is centered on Phospholipase D promotion of Glut-4-containing membrane vesicle trafficking and vesicle fusion into the plasma membrane, in part through activation of atypical protein kinase C isoforms.
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Affiliation(s)
- Ping Huang
- Department of Pharmacology and the Center for Developmental Genetics, University Medical Center at Stony Brook, Stony Brook, NY 11794-5140, USA
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194
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Ciprés A, Carrasco S, Merino E, Díaz E, Krishna UM, Falck JR, Martínez-A C, Mérida I. Regulation of diacylglycerol kinase alpha by phosphoinositide 3-kinase lipid products. J Biol Chem 2003; 278:35629-35. [PMID: 12832407 DOI: 10.1074/jbc.m305635200] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Diacylglycerol kinase alpha (DAGK alpha), like all type I DAGKs, has calcium regulatory motifs that act as negative regulators of enzyme activity and localization. Accordingly, DAGK alpha is activated by phospholipase C-coupled receptors in a calcium-dependent manner. One of the first functions attributed to DAGK alpha in lymphocytes was that of regulating interleukin 2-induced cell cycle entry. Interleukin-2 nonetheless exerts its action in the absence of cytosolic calcium increase. We have studied alternative receptor-derived signals to explain calcium-independent DAGK alpha activation, and show that DAGK alpha is stimulated by Src-like kinase-dependent phosphoinositide 3 kinase (PI3K) activation in lymphocytes. Our results demonstrate that, in vivo, the increase in cellular levels of PI3K products is sufficient to induce DAGK alpha activation, allowing DAGK alpha relocation to the intact lymphocyte plasma membrane. This activation is isoform-specific, because other type I DAGKs are not subject to this type of regulation. These studies are the first to describe a pathway in which, in the absence of receptor-regulated calcium increase, DAGK alpha activation and membrane localization is a direct consequence of PI3K activation.
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Affiliation(s)
- Angel Ciprés
- Department of Immunology and Oncology, National Center for Biotechnology, Consejo Superior de Investigaciones Científicas, Campus de Cantoblanco, E-28049 Madrid, Spain
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195
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Li HS, Shome K, Rojas R, Rizzo MA, Vasudevan C, Fluharty E, Santy LC, Casanova JE, Romero G. The guanine nucleotide exchange factor ARNO mediates the activation of ARF and phospholipase D by insulin. BMC Cell Biol 2003; 4:13. [PMID: 12969509 PMCID: PMC212319 DOI: 10.1186/1471-2121-4-13] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2003] [Accepted: 09/11/2003] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND Phospholipase D (PLD) is involved in many signaling pathways. In most systems, the activity of PLD is primarily regulated by the members of the ADP-Ribosylation Factor (ARF) family of GTPases, but the mechanism of activation of PLD and ARF by extracellular signals has not been fully established. Here we tested the hypothesis that ARF-guanine nucleotide exchange factors (ARF-GEFs) of the cytohesin/ARNO family mediate the activation of ARF and PLD by insulin. RESULTS Wild type ARNO transiently transfected in HIRcB cells was translocated to the plasma membrane in an insulin-dependent manner and promoted the translocation of ARF to the membranes. ARNO mutants: DeltaCC-ARNO and CC-ARNO were partially translocated to the membranes while DeltaPH-ARNO and PH-ARNO could not be translocated to the membranes. Sec7 domain mutants of ARNO did not facilitate the ARF translocation. Overexpression of wild type ARNO significantly increased insulin-stimulated PLD activity, and mutations in the Sec7 and PH domains, or deletion of the PH or CC domains inhibited the effects of insulin. CONCLUSIONS Small ARF-GEFs of the cytohesin/ARNO family mediate the activation of ARF and PLD by the insulin receptor.
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Affiliation(s)
- Hai-Sheng Li
- Departments of Pharmacology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261 USA
| | - Kuntala Shome
- Departments of Pharmacology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261 USA
| | - Raúl Rojas
- Departments of Pharmacology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261 USA
- Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261 USA
| | - Megan A Rizzo
- Departments of Pharmacology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261 USA
| | - Chandrasekaran Vasudevan
- Departments of Pharmacology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261 USA
| | - Eric Fluharty
- Departments of Pharmacology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261 USA
| | - Lorraine C Santy
- Department of Cell Biology, University of Virginia School of Medicine, Charlottesville, VA 22908 USA
| | - James E Casanova
- Department of Cell Biology, University of Virginia School of Medicine, Charlottesville, VA 22908 USA
| | - Guillermo Romero
- Departments of Pharmacology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261 USA
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196
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Mitchell R, Robertson DN, Holland PJ, Collins D, Lutz EM, Johnson MS. ADP-ribosylation factor-dependent phospholipase D activation by the M3 muscarinic receptor. J Biol Chem 2003; 278:33818-30. [PMID: 12799371 DOI: 10.1074/jbc.m305825200] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
G protein-coupled receptors can potentially activate phospholipase D (PLD) by a number of routes. We show here that the native M3 muscarinic receptor in 1321N1 cells and an epitope-tagged M3 receptor expressed in COS7 cells substantially utilize an ADP-ribosylation factor (ARF)-dependent route of PLD activation. This pathway is activated at the plasma membrane but appears to be largely independent of G, phospholipase C, Ca2+ q/11, protein kinase C, tyrosine kinases, and phosphatidyl inositol 3-kinase. We report instead that it involves physical association of ARF with the M3 receptor as demonstrated by co-immunoprecipitation and by in vitro interaction with a glutathione S-transferase fusion protein of the receptor's third intracellular loop domain. Experiments with mutant constructs of ARF1/6 and PLD1/2 indicate that the M3 receptor displays a major ARF1-dependent route of PLD1 activation with an additional ARF6-dependent pathway to PLD1 or PLD2. Examples of other G protein-coupled receptors assessed in comparison display alternative pathways of protein kinase C- or ARF6-dependent activation of PLD2.
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Affiliation(s)
- Rory Mitchell
- Medical Research Council Membrane and Adapter Proteins Co-operative Group, Membrane Biology Interdisciplinary Research Group, School of Biomedical and Clinical Laboratory Sciences, University of Edinburgh, EH8 9XD, United Kingdom.
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197
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Takahashi T, Kamimura A, Hamazono-Matsuoka T, Honda S. Phosphatidic acid has a potential to promote hair growth in vitro and in vivo, and activates mitogen-activated protein kinase/extracellular signal-regulated kinase kinase in hair epithelial cells. J Invest Dermatol 2003; 121:448-56. [PMID: 12925199 DOI: 10.1046/j.1523-1747.2003.12426.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Phospholipids have recently been discovered to play an important role in cellular regulation. In this study, we focused on phosphatidic acid and lysophosphatidic acid, which are phospholipids known to possess growth-hormonal effects on several types of cells, and examined their growth-promoting effects on murine hair epithelial cells. We discovered that phosphatidic acid possesses intensive growth-promotional effects on hair epithelial cells and epidermal keratinocytes. In contrast, lyso-phosphatidic acid showed lower growth-promoting effects on hair epithelial cells relative to phosphatidic acid and showed minimal or no growth-promoting activity on epidermal keratinocytes. Phosphatidic acid was also shown to have hair-growing activity to induce the anagen phase of the hair cycle in the in vivo murine model. For the purpose of examining the hair-growing mechanisms of phosphatidic acid, we examined its relationship to the mitogen-activated protein kinase cascade linked to cell proliferation and the transforming growth factor beta signal pathway known to be a regulator of catagen induction. We confirmed that phosphatidic acid activates MEK-1/2 and upregulates the expression of MEK-1/2 in cultured murine hair epithelial cells. Addition of transforming growth factor beta1 to hair epithelial cell cultures concentration-dependently decreased cell growth and induced apoptosis; however, addition of phosphatidic acid to the culture neutralized the growth-inhibiting effects of transforming growth factor beta1 and protected the cells from apoptosis. We speculate that the hair-growing activity of phosphatidic acid is at least linked to its growth-promoting effects on hair epithelial cells that follow mitogen-activated protein kinase/extracellular signal-regulated kinase kinase activation and its protective action on transforming-growth-factor-beta1-induced apoptosis that is assumed to trigger catagen induction in the hair cycle.
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Affiliation(s)
- Tomoya Takahashi
- Tsukuba Research Laboratories, Kyowa Hakko Kogyo Company, 2 Miyukigaoka, Tsukuba, Ibaraki 305-0841, Japan.
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Navratil AM, Bliss SP, Berghorn KA, Haughian JM, Farmerie TA, Graham JK, Clay CM, Roberson MS. Constitutive localization of the gonadotropin-releasing hormone (GnRH) receptor to low density membrane microdomains is necessary for GnRH signaling to ERK. J Biol Chem 2003; 278:31593-602. [PMID: 12791688 DOI: 10.1074/jbc.m304273200] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Specialized membrane microdomains known as lipid rafts are thought to contribute to G-protein coupled receptor (GPCR) signaling by organizing receptors and their cognate signaling molecules into discrete membrane domains. To determine if the GnRHR, an unusual member of the GPCR superfamily, partitions into lipid rafts, homogenates of alpha T3-1 cells expressing endogenous GnRHR or Chinese hamster ovary cells expressing an epitope-tagged GnRHR were fractionated through a sucrose gradient. We found the GnRHR and c-raf kinase constitutively localized to low density fractions independent of hormone treatment. Partitioning of c-raf kinase into lipid rafts was also observed in whole mouse pituitary glands. Consistent with GnRH induced phosphorylation and activation of c-raf kinase, GnRH treatment led to a decrease in the apparent electrophoretic mobility of c-raf kinase that partitioned into lipid rafts compared with unstimulated cells. Cholesterol depletion of alpha T3-1 cells using methyl-beta-cyclodextrin disrupted GnRHR but not c-raf kinase association with rafts and shifted the receptor into higher density fractions. Cholesterol depletion also significantly attenuated GnRH but not phorbol ester-mediated activation of extracellular signal-related kinase (ERK) and c-fos gene induction. Raft localization and GnRHR signaling to ERK and c-Fos were rescued upon repletion of membrane cholesterol. Thus, the organization of the GnRHR into low density membrane microdomains appears critical in mediating GnRH induced intracellular signaling.
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Affiliation(s)
- Amy M Navratil
- Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado 80523, USA
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199
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Du G, Altshuller YM, Vitale N, Huang P, Chasserot-Golaz S, Morris AJ, Bader MF, Frohman MA. Regulation of phospholipase D1 subcellular cycling through coordination of multiple membrane association motifs. J Cell Biol 2003; 162:305-15. [PMID: 12876278 PMCID: PMC2172799 DOI: 10.1083/jcb.200302033] [Citation(s) in RCA: 135] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The signaling enzyme phospholipase D1 (PLD1) facilitates membrane vesicle trafficking. Here, we explore how PLD1 subcellular localization is regulated via Phox homology (PX) and pleckstrin homology (PH) domains and a PI4,5P2-binding site critical for its activation. PLD1 localized to perinuclear endosomes and Golgi in COS-7 cells, but on cellular stimulation, translocated to the plasma membrane in an activity-facilitated manner and then returned to the endosomes. The PI4,5P2-interacting site sufficed to mediate outward translocation and association with the plasma membrane. However, in the absence of PX and PH domains, PLD1 was unable to return efficiently to the endosomes. The PX and PH domains appear to facilitate internalization at different steps. The PH domain drives PLD1 entry into lipid rafts, which we show to be a step critical for internalization. In contrast, the PX domain appears to mediate binding to PI5P, a lipid newly recognized to accumulate in endocytosing vesicles. Finally, we show that the PH domain-dependent translocation step, but not the PX domain, is required for PLD1 to function in regulated exocytosis in PC12 cells. We propose that PLD1 localization and function involves regulated and continual cycling through a succession of subcellular sites, mediated by successive combinations of membrane association interactions.
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Affiliation(s)
- Guangwei Du
- Department of Pharmacology, University Medical Center, State University of New York at Stony Brook, Stony Brook, NY 11794, USA
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200
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Abstract
Ras signalling has classically been thought to occur exclusively at the inner surface of a relatively uniform plasma membrane. Recent studies have shown that Ras proteins interact dynamically with specific microdomains of the plasma membrane as well as with other internal cell membranes. These different membrane microenvironments modulate Ras signal output and highlight the complex interplay between Ras location and function.
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Affiliation(s)
- John F Hancock
- Institute for Molecular Bioscience and Department of Molecular and Cellular Pathology, University of Queensland, Brisbane, Australia 4072.
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