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Davies BSJ, Beigneux AP, Barnes RH, Tu Y, Gin P, Weinstein MM, Nobumori C, Nyrén R, Goldberg I, Olivecrona G, Bensadoun A, Young SG, Fong LG. GPIHBP1 is responsible for the entry of lipoprotein lipase into capillaries. Cell Metab 2010; 12:42-52. [PMID: 20620994 PMCID: PMC2913606 DOI: 10.1016/j.cmet.2010.04.016] [Citation(s) in RCA: 273] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/18/2009] [Revised: 03/05/2010] [Accepted: 04/28/2010] [Indexed: 12/18/2022]
Abstract
The lipolytic processing of triglyceride-rich lipoproteins by lipoprotein lipase (LPL) is the central event in plasma lipid metabolism, providing lipids for storage in adipose tissue and fuel for vital organs such as the heart. LPL is synthesized and secreted by myocytes and adipocytes, but then finds its way into the lumen of capillaries, where it hydrolyzes lipoprotein triglycerides. The mechanism by which LPL reaches the lumen of capillaries has remained an unresolved problem of plasma lipid metabolism. Here, we show that GPIHBP1 is responsible for the transport of LPL into capillaries. In Gpihbp1-deficient mice, LPL is mislocalized to the interstitial spaces surrounding myocytes and adipocytes. Also, we show that GPIHBP1 is located at the basolateral surface of capillary endothelial cells and actively transports LPL across endothelial cells. Our experiments define the function of GPIHBP1 in triglyceride metabolism and provide a mechanism for the transport of LPL into capillaries.
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Affiliation(s)
- Brandon S J Davies
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
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Müller G, Schulz A, Dearey EA, Wetekam EM, Wied S, Frick W. Synthetic phosphoinositolglycans regulate lipid metabolism between rat adipocytes via release of GPI-protein-harbouring adiposomes. Arch Physiol Biochem 2010; 116:97-115. [PMID: 20515260 DOI: 10.3109/13813455.2010.485205] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
A novel molecular mechanism for the regulation of lipid metabolism by palmitate, H2O2 and the anti-diabetic sulfonylurea drug, glimepiride, in rat adipocytes was recently elucidated. It encompasses the translocation of the glycosylphosphatidylinositol-anchored (GPI-) and (c)AMP degrading enzymes Gce1 and CD73 from detergent-insoluble glycolipid-enriched microdomains of the plasma membrane (DIGs) to intracellular lipid droplets (LD), the incorporation of Gce1 and CD73 into vesicles (adiposomes) which are then released from donor adipocytes and finally the transfer of Gce1 and CD73 from the adiposomes to acceptor adipocytes, where they degrade (c)AMP at the LD surface. Here the stimulation of esterification and inhibition of lipolysis by synthetic phosphoinositolglycans (PIGs), such as PIG37, which represents the glycan component of the GPI anchor, are shown to be correlated to translocation from DIGs to LD and release into adiposomes of Gce1 and CD73. PIG37 actions were blocked upon disruption of DIGs, inactivation of PIG receptor and removal of adiposomes from the incubation medium as was true for those induced by palmitate, H2O2 or glimepiride. In contrast, only the latter actions were dependent on the GPI-specific phospholipase C (GPI-PLC), which may generate PIGs, or on exogenous PIG37 in case of inhibited GPI-PLC. At submaximal concentrations PIG37 and palmitate, H2O2 or glimepiride acted in synergistic fashion. These data suggest that PIGs provoke the transfer of GPI-proteins from DIGs via LD and adiposomes of donor adipocytes to acceptor adipocytes and thereby mediate the regulation of lipid metabolism by palmitate, H2O2 and glimepiride between adipocytes.
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Affiliation(s)
- Günter Müller
- Sanofi-Aventis Deutschland GmbH, Research & Development, 65926 Frankfurt am Main, Germany.
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Chandra S, Ruhela D, Deb A, Vishwakarma RA. Glycobiology of theLeishmaniaparasite and emerging targets for antileishmanial drug discovery. Expert Opin Ther Targets 2010; 14:739-57. [DOI: 10.1517/14728222.2010.495125] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Müller G, Jung C, Wied S, Biemer-Daub G, Frick W. Transfer of the glycosylphosphatidylinositol-anchored 5'-nucleotidase CD73 from adiposomes into rat adipocytes stimulates lipid synthesis. Br J Pharmacol 2010; 160:878-91. [PMID: 20590586 PMCID: PMC2935995 DOI: 10.1111/j.1476-5381.2010.00724.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2009] [Revised: 11/13/2009] [Accepted: 12/13/2009] [Indexed: 01/06/2023] Open
Abstract
BACKGROUND AND PURPOSE In addition to predominant localization at detergent-insoluble, glycolipid-enriched plasma membrane microdomains (DIGs), glycosylphosphatidylinositol (GPI)-anchored proteins (GPI-proteins) have been found associated with lipid droplets (LDs) and adiposomes. Adiposomes are vesicles that are released from adipocytes in response to anti-lipolytic and lipogenic signals, such as H(2)O(2), palmitate and the antidiabetic sulfonylurea drug, glimepiride, and harbour (c)AMP-degrading GPI-proteins, among them the 5-nucleotidase CD73. Here the role of adiposomes in GPI-protein-mediated information transfer was studied. EXPERIMENTAL APPROACH Adiposomes were incubated with isolated rat adipocytes under various conditions. Trafficking of CD73 and lipid synthesis were analysed. KEY RESULTS Upon blockade of GPI-protein trafficking, CD73 specifically associated with DIGs of small, and to a lower degree, large, adipocytes. On reversal of the blockade, CD73 appeared at cytosolic LD in time- adiposome concentration- and signal (H(2)O(2) > glimepiride > palmitate)-dependent fashion. The salt- and carbonate-resistant association of CD73 with structurally intact DIGs and LD was dependent on its intact GPI anchor. Upon incubation with small and to a lower degree, large adipocytes, adiposomes increased lipid synthesis in the absence or presence of H(2)O(2), glimepiride and palmitate and improved the sensitivity toward these signals. Upregulation of lipid synthesis by adiposomes was dependent on the translocation of CD73 with intact GPI anchors from DIGs to LD. CONCLUSIONS The signal-induced transfer of GPI-anchored CD73 from adiposomes via DIGs to LD of adipocytes mediates paracrine upregulation of lipid synthesis within the adipose tissue.
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Affiliation(s)
- G Müller
- Sanofi-Aventis Germany GmbH, Research & Development, Therapeutic Department Metabolism, Frankfurt am Main, Germany.
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56
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Müller G, Schulz A, Hartz D, Dearey EA, Wetekam EM, Okonomopulos R, Crecelius A, Wied S, Frick W. Novel glimepiride derivatives with potential as double-edged swords against type II diabetes. Arch Physiol Biochem 2010; 116:3-20. [PMID: 20166804 DOI: 10.3109/13813450903575720] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Sulphonylurea drugs have been widely used in the safe and efficacous therapy of type II diabetes during the past five decades. They lower blood glucose predominantly via the stimulation of insulin release from pancreatic beta-cells. However, a moderate insulin-independent regulation of fatty acid esterification and release in adipose tissue cells has been reported for certain sulphonylureas, in particular for glimepiride. On basis of the known pleiotropic pathogenesis of type II diabetes with a combination of beta-cell failure and peripheral, including adipocyte, insulin resistance, anti-diabetic drugs exerting both insulin releasing- and fatty acid-metabolizing activities in a more balanced and potent fashion may be of advantage. However, the completely different molecular mechanisms underlying the insulin-releasing and fatty acid-metabolizing activities, as have been delineated so far for glimepiride, may hamper their optimization within a single sulphonylurea molecule. By analyzing conventional sulphonylureas and novel glimepiride derivatives for their activities at the primary targets and downstream steps in both beta-cells and adipocytes in vitro we demonstrate here that the insulin-releasing and fatty acid-metabolizing activities are critically dependent on both overlapping and independent structural determinants. These were unravelled by the parallel losses of these two activities in a subset of glimepiride derivatives and the impairment in the insulin-releasing activity in parallel with elevation in the fatty acid-metabolizing activity in a different subset. Together these findings may provide a basis for the design of novel sulphonylureas with blood glucose-lowering activity relying on less pronounced stimulation of insulin release from pancreatic beta-cells and more pronounced insulin-independent stimulation of esterification as well as inhibition of release of fatty acids by adipocytes than provoked by the sulphonylureas currently used in therapy.
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Affiliation(s)
- Günter Müller
- Therapeutic Department Metabolism and Medicinal Chemistry, Frankfurt am Main, Germany.
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57
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Müller G, Wied S, Jung C, Frick W, Biemer-Daub G. Inhibition of lipolysis by adiposomes containing glycosylphosphatidylinositol-anchored Gce1 protein in rat adipocytes. Arch Physiol Biochem 2010; 116:28-41. [PMID: 20053127 DOI: 10.3109/13813450903508812] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Small membrane vesicles released from large adipocytes and harbouring the glycosylphosphatidylinositol-anchored (GPI-) AMP-degrading protein CD73 have previously been demonstrated to stimulate the signal-induced esterification of free fatty acids into neutral lipids suggesting a role of these so-called adiposomes (ADIP) in the paracrine regulation of lipid metabolism in the adipose tissue. Here the involvement of another constituent GPI-protein of ADIP, the cAMP-degrading protein Gce1 in the signal-induced inhibition of lipolysis was investigated in primary rat adipocytes. Incubation of small, and to a lower degree, large adipocytes with ADIP inhibited lipolysis and increased its sensitivity toward inhibition by H(2)O(2), the anti-diabetic drug glimepiride and palmitate. This was accompanied by the transfer of Gce1 from the ADIP to detergent-insoluble glycolipid-enriched plasma membrane microdomains (DIGs) and its subsequent translocation to cytoplasmic lipid droplets (LD) of the acceptor adipocytes. The translocation from DIGs to LD rather than the transfer from ADIP to DIGs of Gce1 was stimulated by H(2)O(2) > glimepiride > palmitate. Both transfer and translocation led to salt- and carbonate-resistant association of Gce1 with DIGs and LD, respectively, and relied on the structural integrity of the DIGs and GPI anchor of Gce1. In conclusion, the trafficking of GPI-proteins from ADIP of donor adipocytes via DIGs to LD of acceptor adipocytes mediates paracrine regulation of lipolysis within adipose tissue.
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Müller G, Wied S, Dearey EA, Wetekam EM, Biemer-Daub G. Lipid storage in large and small rat adipocytes by vesicle-associated glycosylphosphatidylinositol-anchored proteins. Results Probl Cell Differ 2010; 52:27-34. [PMID: 20865369 DOI: 10.1007/978-3-642-14426-4_3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Adipose tissue mass in mammals expands by increasing the average cell volume and/or total number of the adipocytes. Upregulated lipid storage in fully differentiated adipocytes resulting in their enlargement is well documented and thought to be a critical mechanism for the expansion of adipose tissue depots during the growth of both lean and obese animals and human beings. A novel molecular mechanism for the regulation of lipid storage and cell size in rat adipocytes was recently elucidated for the physiological stimuli, palmitate and H(2)O(2), and the antidiabetic sulfonylurea drug, glimepiride. It encompasses (1) the release of small vesicles, so-called adiposomes, harboring the glycosylphosphatidylinositol -anchored (c)AMP-degrading phosphodiesterase Gce1 and 5'-nucleotidase CD73 from donor adipocytes, (2) the transfer of the adiposomes and their interaction with detergent-insoluble glycolipid-enriched microdomains of the plasma membrane of acceptor adipocytes, (3) the translocation of Gce1 and CD73 from the adiposomes to the intracellular lipid droplets of the acceptor adipocytes, and (4) the degradation of (c)AMP at the lipid droplet surface zone by Gce1 and CD73 in the acceptor adipocytes, leading to the upregulation of the esterification of fatty acids into triacylglycerol s and the downregulation of their release from triacylglycerols. This mechanism may provide novel strategies for the therapy of metabolic diseases, such as type 2 diabetes and obesity.
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Affiliation(s)
- Günter Müller
- Sanofi-Aventis Deutschland GmbH, Research & Development, 65926 Frankfurt, Germany.
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59
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Parameters modulating the maximum insertion pressure of proteins and peptides in lipid monolayers. Biochimie 2009; 91:718-33. [DOI: 10.1016/j.biochi.2009.03.018] [Citation(s) in RCA: 129] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2008] [Accepted: 03/25/2009] [Indexed: 11/18/2022]
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Lee A, Kolarich D, Haynes PA, Jensen PH, Baker MS, Packer NH. Rat Liver Membrane Glycoproteome: Enrichment by Phase Partitioning and Glycoprotein Capture. J Proteome Res 2009; 8:770-81. [DOI: 10.1021/pr800910w] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Albert Lee
- Department of Chemistry and Biomolecular Sciences, Macquarie University, Sydney Australia 2109, and Australian Proteome Analysis Facility (APAF), Macquarie University, Sydney Australia 2109
| | - Daniel Kolarich
- Department of Chemistry and Biomolecular Sciences, Macquarie University, Sydney Australia 2109, and Australian Proteome Analysis Facility (APAF), Macquarie University, Sydney Australia 2109
| | - Paul A. Haynes
- Department of Chemistry and Biomolecular Sciences, Macquarie University, Sydney Australia 2109, and Australian Proteome Analysis Facility (APAF), Macquarie University, Sydney Australia 2109
| | - Pia H. Jensen
- Department of Chemistry and Biomolecular Sciences, Macquarie University, Sydney Australia 2109, and Australian Proteome Analysis Facility (APAF), Macquarie University, Sydney Australia 2109
| | - Mark S. Baker
- Department of Chemistry and Biomolecular Sciences, Macquarie University, Sydney Australia 2109, and Australian Proteome Analysis Facility (APAF), Macquarie University, Sydney Australia 2109
| | - Nicolle H. Packer
- Department of Chemistry and Biomolecular Sciences, Macquarie University, Sydney Australia 2109, and Australian Proteome Analysis Facility (APAF), Macquarie University, Sydney Australia 2109
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61
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Jaggi M, Chauhan SC, Du C, Balaji KC. Bryostatin 1 modulates beta-catenin subcellular localization and transcription activity through protein kinase D1 activation. Mol Cancer Ther 2008; 7:2703-12. [PMID: 18765827 DOI: 10.1158/1535-7163.mct-08-0119] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In recent years, the use of natural products for cancer prevention and treatment has received considerable attention. Bryostatin 1 is a natural macrocyclic lactone and a protein kinase D (PKD) modulator with potent antineoplastic properties that has been used to treat human cancers in clinical trials with limited success. Further understanding the mechanistic basis of Bryostatin 1 action may provide opportunities to improve clinical results of treatment with Bryostatin 1. We identified that PKD1, founding member of PKD family of serine/threonine kinases, modulates E-cadherin/beta-catenin activity, which plays an important role in cell integrity, polarity, growth, and morphogenesis. An aberrant expression and localization of E-cadherin/beta-catenin has been strongly associated with cancer progression and metastasis. In this study, we examined the effect of Bryostatin 1 treatment on PKD1 activation, beta-catenin translocation and transcription activity, and malignant phenotype of prostate cancer cells. Initial activation of PKD1 with Bryostatin 1 leads to colocalization of the cytoplasmic pool of beta-catenin with PKD1, trans-Golgi network markers, and proteins involved in vesicular trafficking. Activation of PKD1 by Bryostatin 1 decreases nuclear beta-catenin expression and beta-catenin/TCF transcription activity. Activation of PKD1 alters cellular aggregation and proliferation in prostate cancer cells associated with subcellular redistribution of E-cadherin and beta-catenin. For the first time, we have identified that Bryostatin 1 modulates beta-catenin signaling through PKD1, which identifies a novel mechanism to improve efficacy of Bryostatin 1 in clinical settings.
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Affiliation(s)
- Meena Jaggi
- Cancer Biology Research Center, Department of OBGYN and Basic Biomedical Science, Sanford Research/University of South Dakota, Sanford School of Medicine, University of South Dakota, 1400 West 22nd Street, Sioux Falls, SD 57105, USA.
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62
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Shanmugarajan S, Youssef RF, Pati P, Ries WL, Rao DS, Reddy SV. Osteoclast inhibitory peptide-1 (OIP-1) inhibits measles virus nucleocapsid protein stimulated osteoclast formation/activity. J Cell Biochem 2008; 104:1500-8. [PMID: 18348201 DOI: 10.1002/jcb.21723] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Paget's disease (PD) of bone is characterized by increased activity of large abnormal osteoclasts (OCLs) which contain paramyxoviral nuclear and cytoplasmic inclusions. MVNP gene expression has been shown to induce pagetic phenotype in OCLs. We previously characterized the osteoclast inhibitory peptide-1 (OIP-1/hSca) which inhibits OCL formation/bone resorption. OIP-1 is a glycophosphatidylinositol (GPI)-linked membrane protein containing a 79 amino acid extra cellular peptide and a 32 amino acid carboxy terminal GPI-linked peptide (c-peptide) which is critical for OCL inhibition. In this study, we demonstrate that OIP-1 c-peptide significantly decreased (43%) osteoclast differentiation of peripheral blood mononuclear cells from patients with PD. Also, OIP-1 treatment to normal human bone marrow mononuclear cells transduced with the MVNP inhibited (41%) osteoclast precursor (CFU-GM) growth in methyl-cellulose cultures. We further tested if OIP-1 overexpression in the OCL lineage in transgenic mice inhibits MVNP stimulated OCL formation. MVNP transduction and RANKL stimulation of OIP-1 mouse bone marrow cells showed a significant decrease (43%) in OCL formation and inhibition (38%) of bone resorption area compared to wild-type mice. Western blot analysis identified that OIP-1 decreased (3.5-fold) MVNP induced TRAF2 expression during OCL differentiation. MVNP or OIP-1 expression did not affect TRAF6 levels. Furthermore, OIP-1 expression resulted in a significant inhibition of MVNP stimulated ASK1, Rac1, c-Fos, p-JNK, and NFATc1 expression during OCL differentiation. These results suggest that OIP-1 inhibits MVNP induced pagetic OCL formation/activity through suppression of RANK signaling. Thus, OIP-1 may have therapeutic utility against excess bone resorption in patients with PD.
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Affiliation(s)
- Srinivasan Shanmugarajan
- Charles P. Darby Children's Research Institute, Medical University of South Carolina, Charleston, South Carolina 29425, USA
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63
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Paulick MG, Bertozzi CR. The glycosylphosphatidylinositol anchor: a complex membrane-anchoring structure for proteins. Biochemistry 2008; 47:6991-7000. [PMID: 18557633 PMCID: PMC2663890 DOI: 10.1021/bi8006324] [Citation(s) in RCA: 399] [Impact Index Per Article: 24.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Positioned at the C-terminus of many eukaryotic proteins, the glycosylphosphatidylinositol (GPI) anchor is a posttranslational modification that anchors the modified protein in the outer leaflet of the cell membrane. The GPI anchor is a complex structure comprising a phosphoethanolamine linker, glycan core, and phospholipid tail. GPI-anchored proteins are structurally and functionally diverse and play vital roles in numerous biological processes. While several GPI-anchored proteins have been characterized, the biological functions of the GPI anchor have yet to be elucidated at a molecular level. This review discusses the structural diversity of the GPI anchor and its putative cellular functions, including involvement in lipid raft partitioning, signal transduction, targeting to the apical membrane, and prion disease pathogenesis. We specifically highlight studies in which chemically synthesized GPI anchors and analogues have been employed to study the roles of this unique posttranslational modification.
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Affiliation(s)
- Margot G Paulick
- Department of Chemistry, University of California, Berkeley, California 94720, USA
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64
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Azzouz N, Gerold P, Schwarz RT. Metabolic labeling and structural analysis of glycosylphosphatidylinositols from parasitic protozoa. Methods Mol Biol 2008; 446:183-98. [PMID: 18373258 DOI: 10.1007/978-1-60327-084-7_13] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
Glycosylphosphatidylinositol (GPI) is a complex glycolipid structure that acts as a membrane anchor for many cell-surface proteins of eukaryotes. GPI-anchored proteins are particularly abundant in protozoa and represent the major carbohydrate modification of many cell-surface parasite proteins. A minimal GPI-anchor precursor consists of core glycan (ethanolamine-P-Manalpha1-2Manalpha1-6Manalpha1-4GlcNH2) linked to the 6-position of the D-myo-inositol ring of phos-phatidylinositol. Although the GPI core glycan is conserved in all organisms, many differences in additional modifications to GPI structures and biosynthetic pathways have been reported. The preassembled GPI-anchor precursor is post-translationally transferred to a variety of membrane proteins in the lumen of the endoplasmic reticulum in a transamidase-like reaction during which a C-terminal GPI attachment signal is released. Increasing evidence show that a significant proportion of the synthesized GPIs are not used for protein anchoring, particularly in protozoa in which a large amount of free GPIs are being displayed at the cell surface. The characteristics of GPI biosynthesis are currently being explored for the development of parasite-specific inhibitors. Especially as this pathway, at least for Trypanosoma brucei, has been validated as a drug target.
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Affiliation(s)
- Nahid Azzouz
- Laboratory for Organic Chemistry, Swiss Federal Institute of Technology, Zürich, Switzerland
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65
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Sesana S, Re F, Bulbarelli A, Salerno D, Cazzaniga E, Masserini M. Membrane Features and Activity of GPI-Anchored Enzymes: Alkaline Phosphatase Reconstituted in Model Membranes. Biochemistry 2008; 47:5433-40. [DOI: 10.1021/bi800005s] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Silvia Sesana
- Department of Experimental Medicine, University of Milano-Bicocca, Monza, Italy
| | - Francesca Re
- Department of Experimental Medicine, University of Milano-Bicocca, Monza, Italy
| | | | - Domenico Salerno
- Department of Experimental Medicine, University of Milano-Bicocca, Monza, Italy
| | - Emanuela Cazzaniga
- Department of Experimental Medicine, University of Milano-Bicocca, Monza, Italy
| | - Massimo Masserini
- Department of Experimental Medicine, University of Milano-Bicocca, Monza, Italy
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66
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A chemical approach to unraveling the biological function of the glycosylphosphatidylinositol anchor. Proc Natl Acad Sci U S A 2007; 104:20332-7. [PMID: 18077333 DOI: 10.1073/pnas.0710139104] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The glycosylphosphatidylinositol (GPI) anchor is a C-terminal posttranslational modification found on many eukaryotic proteins that reside in the outer leaflet of the cell membrane. The complex and diverse structures of GPI anchors suggest a rich spectrum of biological functions, but few have been confirmed experimentally because of the lack of appropriate techniques that allow for structural perturbation in a cellular context. We previously synthesized a series of GPI anchor analogs with systematic deletions within the glycan core and coupled them to the GFP by a combination of expressed protein ligation and native chemical ligation [Paulick MG, Wise AR, Forstner MB, Groves JT, Bertozzi CR (2007) J Am Chem Soc 129:11543-11550]. Here we investigate the behavior of these GPI-protein analogs in living cells. These modified proteins integrated into the plasma membranes of a variety of mammalian cells and were internalized and directed to recycling endosomes similarly to GFP bearing a native GPI anchor. The GPI-protein analogs also diffused freely in cellular membranes. However, changes in the glycan structure significantly affected membrane mobility, with the loss of monosaccharide units correlating to decreased diffusion. Thus, this cellular system provides a platform for dissecting the contributions of various GPI anchor components to their biological function.
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67
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Khodagholi F, Yazdanparast R, Sadeghirizi A. The Glycophosphatidylinositol Anchor Oppositely Affects Unfolding and Refolding of Alkaline Phosphatase. J Biomol Struct Dyn 2007; 25:189-94. [PMID: 17718598 DOI: 10.1080/07391102.2007.10507168] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
Regarding the world wide success of artificial chaperone-assisted protein refolding technique and based on its well worked-out mechanism, it is anticipated that the lipid moieties of glycosylphosphatidylinositol (GPI) group, which is present in some membrane proteins, might interfere with the capturing step of the technique. To find an answer, we evaluated the chemical denaturation and also the refolding behavior of insoluble and soluble alkaline phosohatase (ALP), with or without GPI group, respectively. The results indicated that the presence of GPI in the enzyme increased the stability of the protein against chemical denaturation while it decreased its refolding yield by the artificial chaperone refolding technique. The lower refolding yield, compared to soluble ALP (sALP), might be due to a less efficient stripping step caused by new interactions imparted to the refolding elements of the system especially those among the hydrophobic tails of GPI and the capturing agent of the technique. These new interactions will interrupt the kinetics of detergent stripping from the captured molecules by the stripping agent (i.e., cyclodextrins). This situation will lead to higher intermolecular hydrophobic interactions among the refolding protein intermediates leading to their higher misfolding and aggregation.
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Affiliation(s)
- Fariba Khodagholi
- Institute of Biochemistry and Biophysics, University of Tehran, P. O. Box 13145-1384, Tehran, Iran
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68
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Paulick MG, Wise AR, Forstner MB, Groves JT, Bertozzi CR. Synthetic analogues of glycosylphosphatidylinositol-anchored proteins and their behavior in supported lipid bilayers. J Am Chem Soc 2007; 129:11543-50. [PMID: 17715922 DOI: 10.1021/ja073271j] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Positioned at the C-terminus of many eukaryotic proteins, the glycosylphosphatidylinositol (GPI) anchor is a posttranslational modification that anchors the modified proteins in the outer leaflet of the plasma membrane. GPI-anchored proteins play vital roles in signal transduction, the vertebrate immune response, and the pathobiology of trypanosomal parasites. While many GPI-anchored proteins have been characterized, the biological functions of the GPI anchor have yet to be elucidated at a molecular level. We synthesized a series of GPI-protein analogues bearing modified anchor structures that were designed to dissect the contribution of various glycan components to the GPI-protein's membrane behavior. These anchor analogues were similar in length to native GPI anchors and included mimics of the native structure's three domains. A combination of expressed protein ligation and native chemical ligation was used to attach these analogues to the green fluorescent protein (GFP). These modified GFPs were incorporated in supported lipid bilayers, and their mobilities were analyzed using fluorescence correlation spectroscopy. The data from these experiments suggest that the GPI anchor is more than a simple membrane-anchoring device; it also may prevent transient interactions between the attached protein and the underlying lipid bilayer, thereby permitting rapid diffusion in the bilayer. The ability to generate chemically defined analogues of GPI-anchored proteins is an important step toward elucidating the molecular functions of this interesting post-translational modification.
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Affiliation(s)
- Margot G Paulick
- Department of Chemistry, University of California, Berkeley, California 94720, USA
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Rabuka D, Parthasarathy R, Lee GS, Chen X, Groves JT, Bertozzi CR. Hierarchical assembly of model cell surfaces: synthesis of mucin mimetic polymers and their display on supported bilayers. J Am Chem Soc 2007; 129:5462-71. [PMID: 17425309 PMCID: PMC2535821 DOI: 10.1021/ja067819i] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Molecular level analysis of cell-surface phenomena could benefit from model systems comprising structurally defined components. Here we present the first step toward bottom-up assembly of model cell surfaces-the synthesis of mucin mimetics and their incorporation into artificial membranes. Natural mucins are densely glycosylated O-linked glycoproteins that serve numerous functions on cell surfaces. Their large size and extensive glycosylation makes the synthesis of these biopolymers impractical. We designed synthetically tractable glycosylated polymers that possess rodlike extended conformations similar to natural mucins. The glycosylated polymers were end-functionalized with lipid groups and embedded into supported lipid bilayers where they interact with protein receptors in a structure-dependent manner. Furthermore, their dynamic behavior in synthetic membranes mirrored that of natural biomolecules. This system provides a unique framework with which to study the behavior of mucin-like macromolecules in a controlled, cell surface-mimetic environment.
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Affiliation(s)
- David Rabuka
- Department of Chemistry, Howard Hughes Medical Institute, University of California, California, USA
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70
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Li X, Kaloyanova D, van Eijk M, Eerland R, van der Goot G, Oorschot V, Klumperman J, Lottspeich F, Starkuviene V, Wieland FT, Helms JB. Involvement of a Golgi-resident GPI-anchored protein in maintenance of the Golgi structure. Mol Biol Cell 2007; 18:1261-71. [PMID: 17251550 PMCID: PMC1838991 DOI: 10.1091/mbc.e06-03-0236] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2006] [Revised: 12/22/2006] [Accepted: 01/12/2007] [Indexed: 01/08/2023] Open
Abstract
The Golgi apparatus consists of a series of flattened cisternal membranes that are aligned in parallel to form stacks. Cytosolic-oriented Golgi-associated proteins have been identified that may coordinate or maintain the Golgi architecture. Here, we describe a novel GPI-anchored protein, Golgi-resident GPI-anchored protein (GREG) that has a brefeldin A-sensitive Golgi localization. GREG resides in the Golgi lumen as a cis-oriented homodimer, due to strong interactions between coiled-coil regions in the C termini. Dimerization of GREG as well as its Golgi localization depends on a unique tandem repeat sequence within the coiled-coil region. RNA-mediated interference of GREG expression or expression of GREG mutants reveals an essential role for GREG in maintenance of the Golgi integrity. Under these conditions, secretion of the vesicular stomatitis virus glycoprotein protein as a marker for protein transport along the secretory pathway is inhibited, suggesting a loss of Golgi function as well. These results imply the involvement of a luminal protein in Golgi structure and function.
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Affiliation(s)
- Xueyi Li
- *Biochemie-Zentrum Heidelberg, University of Heidelberg, 69120 Heidelberg, Germany
| | - Dora Kaloyanova
- Department of Biochemistry and Cell Biology and Institute of Biomembranes, Utrecht University, 3508 TD Utrecht, The Netherlands
| | - Martin van Eijk
- Department of Biochemistry and Cell Biology and Institute of Biomembranes, Utrecht University, 3508 TD Utrecht, The Netherlands
| | - Ruud Eerland
- Department of Biochemistry and Cell Biology and Institute of Biomembranes, Utrecht University, 3508 TD Utrecht, The Netherlands
| | - Gisou van der Goot
- Institut des Maladies Infectieuses, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
| | - Viola Oorschot
- Department of Cell Biology, University Medical Center and Institute for Biomembranes, 3584 CX Utrecht, The Netherlands
| | - Judith Klumperman
- Department of Cell Biology, University Medical Center and Institute for Biomembranes, 3584 CX Utrecht, The Netherlands
| | | | - Vytaute Starkuviene
- Cell Biology and Biophysics Programme, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Felix T. Wieland
- *Biochemie-Zentrum Heidelberg, University of Heidelberg, 69120 Heidelberg, Germany
| | - J. Bernd Helms
- Department of Biochemistry and Cell Biology and Institute of Biomembranes, Utrecht University, 3508 TD Utrecht, The Netherlands
- *Biochemie-Zentrum Heidelberg, University of Heidelberg, 69120 Heidelberg, Germany
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71
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Pechlivanis M, Kuhlmann J. Hydrophobic modifications of Ras proteins by isoprenoid groups and fatty acids--More than just membrane anchoring. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2006; 1764:1914-31. [PMID: 17110180 DOI: 10.1016/j.bbapap.2006.09.017] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2006] [Revised: 09/26/2006] [Accepted: 09/29/2006] [Indexed: 01/25/2023]
Abstract
During the last years, post-translational modification of peripheral membrane proteins with hydrophobic side groups has been attributed to a couple of additional functions than just simple anchoring into lipid bilayers. In particular isoprenylation and N- and S-acylation did quicken interest in terms of specific recognition elements for protein-protein interactions and as hydrophobic switches that allow for temporal regulated association with distinct target structures. Furthermore new insights into the heterogeneity of natural membranes have connected the physical properties of e.g. farnesyl or palmitoyl side chains with a preference for such sub-compartments as lipid rafts or caveolae. In this review the impact of the two frequently realized modifications by isoprenylation and S-acylation on the process of cellular signal transduction is exemplified with proteins of the Ras and Rab family of small GTP-binding proteins.
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Affiliation(s)
- Markos Pechlivanis
- Department of Structural Biology, Max Planck Institute for Molecular Physiology, D-44227 Dortmund, Germany
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72
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Zacks MA, Garg N. Recent developments in the molecular, biochemical and functional characterization of GPI8 and the GPI-anchoring mechanism [review]. Mol Membr Biol 2006; 23:209-25. [PMID: 16785205 DOI: 10.1080/09687860600601494] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Glycoconjugates are utilized by eukaryotic organisms ranging from yeast to humans for the cell surface expression of a wide variety of proteins and lipids. These glycoconjugates are expressed as enzymes or receptors and serve a diversity of functions, including cell signaling and cell survival. In parasitic protozoans, glycoconjugates play roles in infectivity, survival, virulence and immune evasion. Among the alternate glycoconjugate structures that have been identified, glycosylphosphatidylinositols (GPIs) represent a universal structure for the anchorage of proteins, lipids, and phosphosaccharides to cellular membranes. Biosynthesis of the GPI is a multi-step process that culminates in the attachment of the assembled GPI to a precursor protein. This final step in the transfer of the GPI to a protein is catalyzed by GPI8 of the putative transamidase complex (TAM). GPI8 functions dually to perform the proteolytic cleavage of the C-terminal signal sequence of the precursor protein, followed by the formation of an amide bond between the protein and the ethanolamine phosphate of the GPI. This review summarizes the current aggregate of biochemical, gene-disruption and active site mutagenesis studies, which provide evidence that GPI8 is responsible for the protein-GPI anchoring reaction. We describe recently published studies that have identified other potential components of the TAM complex and that have elucidated their likely role in protein-GPI attachment. Further, we discuss the biochemical, molecular and functional differences between protozoan and mammalian GPI8 and the protein-GPI anchoring machinery. Finally, we will present the implications of these studies for the development of anti-parasite drug therapies.
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Affiliation(s)
- Michele A Zacks
- Department of Pathology, Center for Biodefense and Emerging Infectious Diseases, University of Texas Medical Branch, Galveston, Texas 77555-1070, USA
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73
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Ronzon F, Rieu JP, Chauvet JP, Roux B. A thermodynamic study of GPI-anchored and soluble form of alkaline phosphatase films at the air-water interface. J Colloid Interface Sci 2006; 301:493-502. [PMID: 16793053 DOI: 10.1016/j.jcis.2006.05.055] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2006] [Revised: 05/23/2006] [Accepted: 05/25/2006] [Indexed: 11/29/2022]
Abstract
Glycosylphosphatidyl inositol (GPI) anchored proteins are localized and clustered on the outer layer of the plasma membranes forming microdomains. Among them, mammalian alkaline phosphatases (AP-GPI) are widely distributed enzymes. They can also exist as soluble proteins without anchor (APs). Using the Langmuir film technique, we study the thermodynamic properties of monolayers for both protein forms at the air-buffer interface. The enzymatic activity is maintained at the interface but the adsorption of the two forms of AP is very different. AP-GPI presents a higher surface activity and a larger molecular area than the soluble form. The molecular area deduced for high surface pressures suggests a different organization of the monolayers for these two forms. APs molecules seem to adsorb as a multilayer at the interface while AP-GPI appear to be orientated with the major axis parallel to the interface. This orientation allows the accessibility of AP-GPI enzymatic sites that are turned in direction of the subphase as in vivo where the active sites must be turned outside of the membrane.
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Affiliation(s)
- Frédéric Ronzon
- Laboratoire de Physico-Chimie Biologique, UMR 5013, Université Claude Bernard Lyon I, 43 boulevard du 11 Novembre 1918, 69622 Villeurbanne cedex, France.
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74
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Hutchinson TE, Rastogi A, Prasad R, Pereira BMJ. Phospholipase-C sensitive GPI-anchored proteins of goat sperm: possible role in sperm protection. Anim Reprod Sci 2005; 88:271-86. [PMID: 16143217 DOI: 10.1016/j.anireprosci.2004.12.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2004] [Revised: 11/15/2004] [Accepted: 12/16/2004] [Indexed: 10/25/2022]
Abstract
The role of glycosylphosphatidylinositol (GPI)-anchored sperm proteins in reproduction has been investigated. SDS-polyacrylamide gels (PAGE) analysis of goat sperm (Capra indica) indicated that several GPI-anchored proteins were released by phosphatidylinositol-specific phospholipase-C (PI-PLC) treatment. The distribution of this category of PI-PLC-sensitive GPI-anchored proteins on the surface of sperm was examined by indirect immunofluorescence. The fluorescence microscopic study clearly demonstrated that the PI-PLC-sensitive GPI-anchored proteins are confined predominantly to the head region of goat sperm. Further experiments were conducted on intact and PI-PLC treated sperm in order to decipher the function of GPI proteins. Co-incubation of sperm with peritoneal macrophages led to the enhanced phagocytosis of PI-PLC treated sperm by macrophages compared with the untreated intact sperm. Transmission electron micrographs of the macrophages acquired from the phagocytosis assay are provided to corroborate the same. From the results obtained it is inferred that one or more of the PI-PLC-sensitive GPI-anchored proteins on the sperm surface could act as protection factor(s) that shield the sperm from macrophages.
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Affiliation(s)
- T E Hutchinson
- Reproductive Biology Laboratory, Department of Biotechnology, Indian Institute of Technology Roorkee, Uttaranchal
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75
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Grogan MJ, Kaizuka Y, Conrad RM, Groves JT, Bertozzi CR. Synthesis of Lipidated Green Fluorescent Protein and Its Incorporation in Supported Lipid Bilayers. J Am Chem Soc 2005; 127:14383-7. [PMID: 16218633 DOI: 10.1021/ja052407f] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Herein we report a semisynthetic method of producing membrane-anchored proteins. Ligation of synthetic lipids with designed anchor structures to proteins was performed using native chemical ligation (NCL) of a C-terminal peptide thioester and an N-terminal cysteine lipid. This strategy mimics the natural glycosylphosphatidylinositol (GPI) linkage found in many natural membrane-associated proteins; however, the synthetic method utilizes simple lipid anchors without glycans. Synthetically lipidated recombinant green fluorescent protein (GFP) was shown to be stably anchored to the membrane, and its lateral fluidity was quantitatively characterized by direct fluorescence imaging in supported membranes. Circumventing the steps of purification from native cell membranes, this methodology facilitates the reconstitution of membrane-associated proteins.
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Affiliation(s)
- Michael J Grogan
- Departments of Chemistry and Molecular and Cell Biology, Physical Biosciences and Materials Sciences Divisions, University of California-Berkeley, Berkeley, CA 94720, USA
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76
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Kouzayha A, Besson F. GPI-alkaline phosphatase insertion into phosphatidylcholine monolayers: phase behavior and morphology changes. Biochem Biophys Res Commun 2005; 333:1315-21. [PMID: 15979580 DOI: 10.1016/j.bbrc.2005.06.049] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2005] [Accepted: 06/06/2005] [Indexed: 11/17/2022]
Abstract
GPI-anchored proteins are localized on the outer layer of plasma membranes and clustered in microdomains generally called lipid rafts. To study the interactions between the lipidic GPI-anchor of the protein and phospholipids, we used phosphatidylcholine monolayers at the air-water interface as a biomimetic membrane system and GPI-alkaline phosphatase prepared from bovine intestinal mucosa (GPI-BIAP) as an GPI-anchored protein model. The monolayer technique allowed us to define GPI-BIAP interaction with DPPC and POPC, lipids differing only by the presence of one unsaturation in their acyl chains. Meanwhile the exclusion pressures were similar for the two phospholipids, the comparison of the Langmuir isotherms (i.e., pressure/area diagrams) indicates that GPI-BIAP interacted differently with DPPC and POPC monolayers. BAM images, acquired in order to visualize the interface organization induced by GPI-BIAP incorporation, confirm these differences.
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Affiliation(s)
- Achraf Kouzayha
- Laboratoire Organisation and Dynamique des Membranes Biologiques, UMR-CNRS 5013, Université Claude Bernard Lyon I, 43 boulevard du 11 novembre 1918, F-69622 Villeurbanne Cedex, France
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77
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Simon MC, Schmidt HJ. Variety of Serotypes of Paramecium primaurelia: Single Epitopes are Responsible for Immunological Differentiation. J Eukaryot Microbiol 2005; 52:319-27. [PMID: 16014009 DOI: 10.1111/j.1550-7408.2005.00040.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Paramecium primaurelia expresses three major types of surface antigens. We report here the identification of the gene for serotype S, which completes the sequence data of expressed serotypes of P. primaurelia. The complete open reading frame of surface antigen S was identified using a novel technique, based upon the presence of conservative regions in the non-coding areas of the multigene family. We were able to isolate the 7194-bp-long open reading frame from the macronuclear DNA for Serotype 156S. The corresponding mRNA was detected in the two serotype S-expressing stocks, 60 and 156, of P. primaurelia, which clarifies that both stocks are using the same S allele. Comparisons of the nucleic acid and the deduced amino-acid sequence showed high identity to surface antigen 51B of P. tetraurelia, sufficient to cause an immunological cross-reaction in vivo. Immunologically relevant epitopes in vivo were identified in the central regions of the genes, constructed of nearly perfect tandem repeats.
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Affiliation(s)
- Martin C Simon
- Department of Ecology, University of Kaiserslautern, Building 14, Gottlieb-Daimler Street, 67663 Kaiserslautern, Germany.
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78
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Garcerá A, Castillo L, Martínez AI, Elorza MV, Valentín E, Sentandreu R. Anchorage of Candida albicans Ssr1 to the cell wall, and transcript profiling of the null mutant. Res Microbiol 2005; 156:911-20. [PMID: 16024227 DOI: 10.1016/j.resmic.2005.05.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2005] [Revised: 05/03/2005] [Accepted: 05/04/2005] [Indexed: 11/16/2022]
Abstract
Incorporation into the wall of Candida albicans Ssr1, a GPI-dependent protein, was investigated by construction of different truncated genes for which the three potential omega sites (S199, S215 and G216) and the corresponding omega+1 and omega+2 were eliminated or modified. Cells of the C. albicans ssr1Delta mutant were transformed with pADH-pl harboring the truncated versions of CaSSR1, pADH-DeltaCaSSR1t(217-234) (lacking a C-terminal hydrophobic stretch of 18 aa including the putative omega+2 and omega+1, omega+2 of S215 and G216) or pADH-DeltaCaSSR1t(199-201) (lacking three serine residues), and their walls were analyzed for the protein. Results suggested that the three serine residues are essential for incorporation of CaSsr1 into the wall beta-glucan. This interpretation was confirmed when the truncated protein CaSsr1pt(199-201) was found in the spent medium. The transcription profile of the 6039 genes in C. albicans ssr1Delta showed that seven genes are upregulated (1.4-fold), including SRP54 (a signal recognition particle subunit), IPF29 (a zinc finger protein) and PTR3 (a transcriptional regulator), whereas 27 genes are downregulated (0.7-fold), including IPF6318 (a beta-glucosidase) and SOU1 (a sorbitol utilization protein). Additional genes showed a reduced increase, or decreased expression, suggesting that some current orphan genes may have unknown cell wall functions. In addition, a compensatory mechanism would appear to occur, as a substantial increase in the amount of beta-1,3-glucan (2.34-fold) was detected in the cell wall of the mutant cells.
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Affiliation(s)
- Ana Garcerá
- Department de Microbiología i Ecología, Facultat de Farmacia, Universitat de València, Avgda. Vicent Andrés Estellés s/n, 46100 Burjassot, València, Spain
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79
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Cross B, Ronzon F, Roux B, Rieu JP. Measurement of the anchorage force between GPI-anchored alkaline phosphatase and supported membranes by AFM force spectroscopy. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2005; 21:5149-53. [PMID: 15896063 DOI: 10.1021/la0470986] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Mammalian alkaline phosphatases (AP) are glycosylphosphatidylinositol (GPI) anchored proteins that are localized on the outer layer of the plasma membrane. The GPI anchors are covalently attached to the C-termini of proteins and consist of a glycan chain bonded to phosphatidylinositol with two acyl chains anchored into the membrane bilayer. Force spectroscopy, based on atomic force microscope (AFM) technology, was used to determine the adhesion of alkaline phosphatase in the absence and presence of anchors. The GPI anchors increase markedly the adhesion frequency (i.e., the protein affinity for the membrane). An adhesion force of 350 +/- 200 pN is measured between GPI-anchored AP (AP(GPI)) and supported phospholipid bilayers of dipalmitoylphosphatidylcholine (DPPC) presenting structural defects (holes). In the absence of defects, the adhesion force (103 +/- 17 pN) and the adhesion frequency are reduced. These results indicate that AP(GPI) poorly spontaneously insert into membranes in vivo and open new perspectives for the characterization of the interactions between GPI proteins and membranes.
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Affiliation(s)
- Benjamin Cross
- Laboratoire de Physique de la Matière Condensée et Nanostructures, Université Claude Bernard Lyon-1 et CNRS, 69622 Villeurbanne, France
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80
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Caseli L, Oliveira RG, Masui DC, Furriel RPM, Leone FA, Maggio B, Zaniquelli MED. Effect of molecular surface packing on the enzymatic activity modulation of an anchored protein on phospholipid Langmuir monolayers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2005; 21:4090-4095. [PMID: 15835979 DOI: 10.1021/la047292s] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The catalytic activity of a glycosylphosphatidylinositol (GPI)-anchored alkaline phosphatase has been studied in Langmuir phospholipid monolayers at different surface pressures. The enzyme substrate, p-nitrophenyl phosphate, was injected into the subphase of mixed enzyme/lipid Langmuir monolayers. Its hydrolysis product was followed by monitoring the absorbance at 410 nm in situ in the monolayer subphase of the Langmuir trough. Several surface pressures, corresponding to different molecular surface densities, were attained by lateral compression of the monolayers. The morphology of the monolayers, observed by fluorescence microscopy, showed three different types of domains owing to the heterogeneous partition of the enzyme within the mixed enzyme/lipid film. The catalytic activity was modulated by the enzyme surface density, and it increased until a pressure of 18 mN/m was reached, but it decreased significantly when the equilibrium in-plane elasticity (surface compressional modulus) increased more noticeably, resulting in alterations in the interface morphology. A model for the modulation of the enzyme orientation and catalytic activity by lipid/enzyme surface morphology and enzyme surface packing at the air/liquid interface is proposed. The results might have an important impact on the comprehension of the enzymatic activity regulation of GPI-anchored proteins in biomembranes.
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Affiliation(s)
- Luciano Caseli
- Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo, Brazil
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81
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Müller G, Schulz A, Wied S, Frick W. Regulation of lipid raft proteins by glimepiride- and insulin-induced glycosylphosphatidylinositol-specific phospholipase C in rat adipocytes. Biochem Pharmacol 2005; 69:761-80. [PMID: 15710354 DOI: 10.1016/j.bcp.2004.11.014] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2004] [Accepted: 11/25/2004] [Indexed: 11/18/2022]
Abstract
The insulin receptor-independent insulin-mimetic signalling provoked by the antidiabetic sulfonylurea drug, glimepiride, is accompanied by the redistribution and concomitant activation of lipid raft-associated signalling components, such as the acylated tyrosine kinase, pp59(Lyn), and some glycosylphosphatidylinositol-anchored proteins (GPI-proteins). We now found that impairment of glimepiride-induced lipolytic cleavage of GPI-proteins in rat adipocytes by the novel inhibitor of glycosylphosphatidylinositol-specific phospholipase C (GPI-PLC), GPI-2350, caused almost complete blockade of (i) dissociation from caveolin-1 of pp59(Lyn) and GPI-proteins, (ii) their redistribution from high cholesterol- (hcDIGs) to low cholesterol-containing (lcDIGs) lipid rafts, (iii) tyrosine phosphorylation of pp59(Lyn) and insulin receptor substrate-1 protein (IRS-1) and (iv) stimulation of glucose transport as well as (v) inhibition of isoproterenol-induced lipolysis in response to glimepiride. In contrast, blockade of the moderate insulin activation of the GPI-PLC and of lipid raft protein redistribution by GPI-2350 slightly reduced insulin signalling and metabolic action, only. Importantly, in response to both insulin and glimepiride, lipolytically cleaved hydrophilic GPI-proteins remain associated with hcDIGs rather than redistribute to lcDIGs as do their uncleaved amphiphilic versions. In conclusion, GPI-PLC controls the localization within lipid rafts and thereby the activity of certain GPI-anchored and acylated signalling proteins. Its stimulation is required and may even be sufficient for insulin-mimetic cross-talking to IRS-1 in response to glimepiride via redistributed and activated pp59(Lyn).
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Affiliation(s)
- Günter Müller
- Sanofi-Aventis, TD Metabolism, Industrial Park Frankfurt-Höchst, 65926 Frankfurt am Main, Germany.
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82
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Kang JY, Hong Y, Ashida H, Shishioh N, Murakami Y, Morita YS, Maeda Y, Kinoshita T. PIG-V involved in transferring the second mannose in glycosylphosphatidylinositol. J Biol Chem 2004; 280:9489-97. [PMID: 15623507 DOI: 10.1074/jbc.m413867200] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Glycosylphosphatidylinositol (GPI) is a glycolipid that anchors many proteins to the eukaryotic cell surface. The biosynthetic pathway of GPI is mediated by sequential additions of sugars and other components to phosphatidylinositol. Four mannoses in the GPI are transferred from dolichol-phosphate-mannose (Dol-P-Man) and are linked through different glycosidic linkages. Therefore, four Dol-P-Man-dependent mannosyltransferases, GPI-MT-I, -MT-II, -MT-III, and -MT-IV for the first, second, third, and fourth mannoses, respectively, are required for generation of GPI. GPI-MT-I (PIG-M), GPI-MT-III (PIG-B), and GPI-MT-IV (SMP3) were previously reported, but GPI-MT-II remains to be identified. Here we report the cloning of PIG-V involved in transferring the second mannose in the GPI anchor. Human PIG-V encodes a 493-amino acid, endoplasmic reticulum (ER) resident protein with eight putative transmembrane regions. Saccharomyces cerevisiae protein encoded in open reading frame YBR004c, which we termed GPI18, has 25% amino acid identity to human PIG-V. Viability of the yeast gpi18 deletion mutant was restored by human PIG-V cDNA. PIG-V has two functionally important conserved regions facing the ER lumen. Taken together, we suggest that PIG-V is the second mannosyltransferase in GPI anchor biosynthesis.
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Affiliation(s)
- Ji Young Kang
- Department of Immunoregulation, Research Institute for Microbial Diseases, 3-1 Yamada-oka, Suita, Osaka 565-0871, Japan
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83
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Pang S, Urquhart P, Hooper NM. N-Glycans, not the GPI anchor, mediate the apical targeting of a naturally glycosylated, GPI-anchored protein in polarised epithelial cells. J Cell Sci 2004; 117:5079-86. [PMID: 15456847 DOI: 10.1242/jcs.01386] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The glycosyl-phosphatidylinositol (GPI) anchor mediates the apical sorting of proteins in polarised epithelial cells through its interaction with lipid rafts. Here we investigated the signals required for the apical targeting of the naturally N-glycosylated and GPI-anchored membrane dipeptidase by selective point mutation to remove the GPI anchor addition signal or the sites for N-linked glycosylation, or both. Activity assays, immunoblotting and immunofluorescence microscopy revealed that the constructs lacking the GPI anchor were secreted from Madin-Darby canine kidney (MDCK) cells, whereas those retaining the GPI anchor were attached at the cell surface, irrespective of the glycosylation status. Wild-type membrane dipeptidase was expressed preferentially on the apical surface of both MDCK and CaCo-2 cells. By contrast, the GPI-anchored construct lacking the N-glycans was targeted preferentially to the basolateral surface of both cell types. In constructs lacking the GPI anchor, the N-glycans also targeted the protein to the apical surface. Both the apically targeted, glycosylated and the basolaterally targeted, unglycosylated GPI-anchored forms of the protein were located in detergent-insoluble lipid rafts. These data indicate that it is the N-glycans, not the association of the GPI anchor with lipid rafts, which determine apical targeting of an endogenously N-glycosylated, GPI-anchored protein in polarised epithelial cells.
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Affiliation(s)
- Susan Pang
- School of Biochemistry and Microbiology, University of Leeds, LS2 9JT, UK
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84
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Siu LS, Romanska H, Abel PD, Kayademir T, Blin N, Stamp GWH, Lalani EN. TFF1 is membrane-associated in breast carcinoma cell line MCF-7. Peptides 2004; 25:745-53. [PMID: 15177868 DOI: 10.1016/j.peptides.2004.01.024] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/01/2003] [Accepted: 01/14/2004] [Indexed: 02/04/2023]
Abstract
Trefoil factor family (TFF) domain peptides, products of mucin-secreting epithelial cells, are thought to influence mucosal integrity. Molecular studies revealed that mammalian TFFs lack transmembrane domains. Using immunocytochemistry and FACS analysis we demonstrated the association of TFF1 with the cell membrane in MCF-7 (a breast adenocarcinoma cell line), and tested the hypothesis that glycosylphosphatidylinositol (GPI) linkage is the mechanism for this association. Cleavage of GPI anchorage using phospholipase C did not affect TFF1 binding to the cell membrane. Our results demonstrate for the first time that TFF1 is associated with the cell membrane of MCF-7 cells and is not linked via a GPI anchor.
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Affiliation(s)
- Lai-San Siu
- Department of Histopathology, Imperial College, Hammersmith Campus, London W12 0NN, UK
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85
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Grimme SJ, Gao XD, Martin PS, Tu K, Tcheperegine SE, Corrado K, Farewell AE, Orlean P, Bi E. Deficiencies in the endoplasmic reticulum (ER)-membrane protein Gab1p perturb transfer of glycosylphosphatidylinositol to proteins and cause perinuclear ER-associated actin bar formation. Mol Biol Cell 2004; 15:2758-70. [PMID: 15075373 PMCID: PMC420100 DOI: 10.1091/mbc.e04-01-0035] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The essential GAB1 gene, which encodes an endoplasmic reticulum (ER)-membrane protein, was identified in a screen for mutants defective in cellular morphogenesis. A temperature-sensitive gab1 mutant accumulates complete glycosylphosphatidylinositol (GPI) precursors, and its temperature sensitivity is suppressed differentially by overexpression of different subunits of the GPI transamidase, from strong suppression by Gpi8p and Gpi17p, to weak suppression by Gaa1p, and to no suppression by Gpi16p. In addition, both Gab1p and Gpi17p localize to the ER and are in the same protein complex in vivo. These findings suggest that Gab1p is a subunit of the GPI transamidase with distinct relationships to other subunits in the same complex. We also show that depletion of Gab1p or Gpi8p, but not Gpi17p, Gpi16p, or Gaa1p causes accumulation of cofilin-decorated actin bars that are closely associated with the perinuclear ER, which highlights a functional interaction between the ER network and the actin cytoskeleton.
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Affiliation(s)
- Stephen J Grimme
- Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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86
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Abstract
In order to carry out their physiological functions, ion transport proteins must be targeted to the appropriate domains of cell membranes. Regulation of ion transport activity frequently involves the tightly controlled delivery of intracellular populations of transport proteins to the plasma membrane or the endocytic retrieval of transport proteins from the cell surface. Transport proteins carry signals embedded within their structures that specify their subcellular distributions and endow them with the capacity to participate in regulated membrane trafficking processes. Recently, a great deal has been learned about the biochemical nature of these signals, as well as about the cellular machinery that interprets them and acts upon their messages.
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Affiliation(s)
- Theodore R Muth
- Department of Biology, CUNY Brooklyn College, 2900 Bedford Avenue, Brooklyn, New York 11231, USA.
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87
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Sun W, Zhao ZD, Hare MC, Kieliszewski MJ, Showalter AM. Tomato LeAGP-1 is a plasma membrane-bound, glycosylphosphatidylinositol-anchored arabinogalactan-protein. PHYSIOLOGIA PLANTARUM 2004; 120:319-327. [PMID: 15032867 DOI: 10.1111/j.0031-9317.2004.0236.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Arabinogalactan-proteins (AGPs) are a class of highly glycosylated, hydroxyproline-rich glycoproteins that function in plant growth and development. Tomato LeAGP-1 represents a major AGP expressed in cultured cells and plants. Based on cDNA and amino acid sequence analyses along with carbohydrate and other biochemical analyses, tomato LeAGP-1 is hypothesized to be a classical AGP localized to the plasma membrane via a glycosylphosphatidylinositol (GPI) anchor. Here, this hypothesis was tested and supported with the following experiments. First, tomato (Lycopersicon esculentum, cv. UC82B) cotyledon protoplasts were isolated following cell wall digestion with cellulase and pectinase, and LeAGP-1 was immunolocalized to the plasma membrane with a LeAGP-1 antibody. Second, LeAGP-1 was shown to be a major AGP component in plasma membrane vesicles from tomato cv. Bonnie Best suspension-cultured cells by Western blot analysis with the LeAGP-1 antibody. Third, fluorescence microscopy of plasmolysed, transgenic tobacco (Nicotiana tabacum BY-2) suspension-cultured cells expressing a green fluorescent protein (GFP)-LeAGP-1 fusion product demonstrated localization to the plasma membrane and Hechtian threads. Fourth, the GFP-LeAGP-1 fusion protein was present in plasma membrane preparations from these transgenic tobacco cells by Western blot analysis with a GFP antibody. Fifth, GFP-LeAGP-1 secreted into the culture media contained ethanolamine, presumably attached to the C-terminal amino acid residue, consistent with its processing and release from the plasma membrane. Thus, these data support the hypothesis that LeAGP-1 is localized to the plasma membrane via a GPI anchor and suggest possible roles for LeAGP-1 in cellular signalling and matrix remodelling.
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Affiliation(s)
- Wenxian Sun
- Department of Environmental and Plant Biology, Ohio University, Athens, OH 45701-2979, USA
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88
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Eisenhaber B, Maurer-Stroh S, Novatchkova M, Schneider G, Eisenhaber F. Enzymes and auxiliary factors for GPI lipid anchor biosynthesis and post-translational transfer to proteins. Bioessays 2003; 25:367-85. [PMID: 12655644 DOI: 10.1002/bies.10254] [Citation(s) in RCA: 139] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
GPI lipid anchoring is an important post-translational modification of eukaryote proteins in the endoplasmic reticulum. In total, 19 genes have been directly implicated in the anchor synthesis and the substrate protein modification pathway. Here, the molecular functions of the respective proteins and their evolution are analyzed in the context of reported literature data and sequence analysis studies for the complete pathway (http://mendel.imp.univie.ac.at/SEQUENCES/gpi-biosynthesis/) and questions for future experimental investigation are discussed. Studies of two of these proteins have provided new mechanistic insights. The cytosolic part of PIG-A/GPI3 has a two-domain alpha/beta/alpha-layered structure; it is suggested that its C-terminal subsegment binds UDP-GlcNAc whereas the N-terminal domain interacts with the phosphatidylinositol moiety. The lumenal part of PIG-T/GPI16 apparently consists of a beta-propeller with a central hole that regulates the access of substrate protein C termini to the active site of the cysteine protease PIG-K/GPI8 (gating mechanism) as well as of a polypeptide hook that embraces PIG-K/GPI8. This structural proposal would explain the paradoxical properties of the GPI lipid anchor signal motif and of PIG-K/GPI8 orthologs without membrane insertion regions in some species.
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Affiliation(s)
- Birgit Eisenhaber
- Research Institute of Molecular Pathology, Dr. Bohr-Gasse 7, A-1030 Vienna, Republic Austria
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89
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Pusch U, Effendy I, Schwarz RT, Azzouz N. Glycosylphosphatidylinositols synthesized by Trichophyton rubrum in a cell-free system. Mycoses 2003; 46:104-13. [PMID: 12870198 DOI: 10.1046/j.1439-0507.2003.00854.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The opportunistic fungi Trichophyton rubrum and T. mentagrophytes, are responsible for relatively non-inflammatory chronic dermatophytes infections in immunocompromised patients but also in healthy individuals. This chronic infection is associated with immunosuppressive effects of the cell wall components particularly the polysaccharides secreted by these organisms. We have studied glycosylphosphatidylinositol (GPI) anchor biosynthesis in the pathogenic fungus T. rubrum and could demonstrate that T. rubrum is able to synthesize GPI structures. Glycolipids synthesized in a cell-free system prepared from the dermatophyte T. rubrum and labeled with [3H]mannose, and [3H]galactose using GDP-[3H]mannose and UDP-[3H]galactose, respectively, were identified and structurally characterized as GPIs. The evolutionary conserved backbone of T. rubrum GPIs incorporates galactose. Further, all glycolipids lack the acyl group on the inositol which was shown for Saccharomyces cerevisiae and mammalian GPIs. Our data suggest significant differences in the GPI biosynthetic pathway between mammalian and T. rubrum cells that could perhaps be exploited for the development of an antimycotic for Trichophyton infection.
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Affiliation(s)
- Ulrike Pusch
- Institut für Virology, Medizinisches Zentrum für Hygiene und Medizinische Mikrobiologie, Philipps-Universität Marburg, Robert-Koch-Strasse 17, D-35037 Marburg, Germany
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90
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de Macedo CS, Shams-Eldin H, Smith TK, Schwarz RT, Azzouz N. Inhibitors of glycosyl-phosphatidylinositol anchor biosynthesis. Biochimie 2003; 85:465-72. [PMID: 12770785 DOI: 10.1016/s0300-9084(03)00065-8] [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: 11/15/2022]
Abstract
Glycosyl-phosphatidylinositol (GPI) is a complex glycolipid structure that acts as a membrane anchor for many cell-surface proteins of eukaryotes. GPI-anchored proteins are particularly abundant in protozoa such as Trypanosoma brucei, Leishmania major, Plasmodium falciparum and Toxoplasma gondii, and represent the major carbohydrate modification of many cell-surface parasite proteins. Although the GPI core glycan is conserved in all organisms, many differences in additional modifications to GPI structures and biosynthetic pathways have been reported. Therefore, the characteristics of GPI biosynthesis are currently being explored for the development of parasite-specific inhibitors. In vitro and in vivo studies using sugars and substrate analogues as well as natural compounds have shown that it is possible to interfere with GPI biosynthesis at different steps in a species-specific manner. Here we review the recent and promising progress in the field of GPI inhibition.
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Affiliation(s)
- Cristiana Santos de Macedo
- Institut für Virologie, Zentrum für Hygiene und Med. Mikrobiologie, Philipps-Universität Marburg, Germany
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91
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Kimmel J, Ogun SA, de Macedo CS, Gerold P, Vivas L, Holder AA, Schwarz RT, Azzouz N. Glycosylphosphatidyl-inositols in murine malaria: Plasmodium yoelii yoelii. Biochimie 2003; 85:473-81. [PMID: 12770786 DOI: 10.1016/s0300-9084(03)00019-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Glycosylphosphatidyl-inositols (GPIs) are vital major glycoconjugates in intraerythrocytic stages of Plasmodium. Here, we report on the biosynthesis and the characterization of GPIs synthesized by the murine malarial parasite P. yoelii yoelii YM. Parasitized erythrocytes were labeled in vivo and in vitro with either radioactive nucleotide sugar precursors, ethanolamine or glucosamine. The pathway leading to the formation of GPI precursors was found to resemble that described for P. falciparum; however, in P. yoelii, the formation of an additional hydrophilic precursor containing an acid-labile modification was detected. The data suggest that this modification is linked to the fourth mannose attached to the trimannosyl backbone in an alpha1-2 linkage. The modification was susceptible to hydrofluoric acid (HF), but not to nitrous acid (HNO(2)). Data obtained from size-exclusion chromatography on Bio-Gel P4, and Mono Q analysis of the fragments generated by HNO(2) deamination suggest that the modification is due to the presence of an additional ethanolamine linked to the fourth mannose via a phosphodiester bond.
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Affiliation(s)
- Jürgen Kimmel
- Institut für Virologie, Zentrum für Hygiene und Med. Mikrobiologie, Philipps-Universität Marburg, 35037 Marburg, Germany
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92
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93
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Müller G, Hanekop N, Kramer W, Bandlow W, Frick W. Interaction of phosphoinositolglycan(-peptides) with plasma membrane lipid rafts of rat adipocytes. Arch Biochem Biophys 2002; 408:17-32. [PMID: 12485599 DOI: 10.1016/s0003-9861(02)00451-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Insulin receptor-independent activation of the insulin signal transduction cascade in insulin-responsive target cells by phosphoinositolglycans (PIG) and PIG-peptides (PIG-P) is accompanied by redistribution of glycosylphosphatidylinositol (GPI)-anchored plasma membrane proteins (GPI proteins) and dually acylated nonreceptor tyrosine kinases from detergent/carbonate-resistant glycolipid-enriched plasma membrane raft domains of high-cholesterol content (hcDIGs) to rafts of lower cholesterol content (lcDIGs). Here we studied the nature and localization of the primary target of PIG(-P) in isolated rat adipocytes. Radiolabeled PIG-P (Tyr-Cys-Asn-NH-(CH(2))(2)-O-PO(OH)O-6Manalpha1(Manalpha1-2)-2Manalpha1-6Manalpha1-4GluN1-6Ino-1,2-(cyclic)-phosphate) prepared by chemical synthesis or a radiolabeled lipolytically cleaved GPI protein from Saccharomyces cerevisiae, which harbors the PIG-P moiety, bind to isolated hcDIGs but not to lcDIGs. Binding is saturable and abolished by pretreatment of intact adipocytes with trypsin followed by NaCl or with N-ethylmaleimide, indicating specific interaction of PIG-P with a cell surface protein. A 115-kDa polypeptide released from the cell surface by the trypsin/NaCl-treatment is labeled by [(14)C]N-ethylmaleimide. The labeling is diminished upon incubation of adipocytes with PIG-P which can be explained by direct binding of PIG-P to the 115-kDa protein and concomitant loss of its accessibility to N-ethylmaleimide. Binding of PIG-P to hcDIGs is considerably increased after pretreatment of adipocytes with (glycosyl)phosphatidylinositol-specific phospholipases compatible with lipolytic removal of endogenous ligands, such as GPI proteins/lipids. These data demonstrate that in rat adipocytes synthetic PIG(-P) as well as lipolytically cleaved GPI proteins interact specifically with hcDIGs. The interaction depends on the presence of a trypsin/NaCl/NEM-sensitive 115-kDa protein located at hcDIGs which thus represents a candidate for a binding protein for exogenous insulin-mimetic PIG(-P) and possibly endogenous GPI proteins/lipids.
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Affiliation(s)
- Günter Müller
- Aventis Pharma Germany, DG Metabolic Diseases, Industrial Park Höchst, Bldg. H825, 65926, Frankfurt am Main, Germany.
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94
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Grogan MJ, Pratt MR, Marcaurelle LA, Bertozzi CR. Homogeneous glycopeptides and glycoproteins for biological investigation. Annu Rev Biochem 2002; 71:593-634. [PMID: 12045107 DOI: 10.1146/annurev.biochem.71.110601.135334] [Citation(s) in RCA: 138] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Protein glycosylation is widely recognized as a modulator of protein structure, localization, and cell-cell recognition in multicellular systems. Glycoproteins are typically expressed as mixtures of glycoforms, their oligosaccharides being generated by a template-independent biosynthetic process. Investigation of their function has been greatly assisted by sources of homogeneous material. This review summarizes current efforts to obtain homogeneous glycopeptide and glycoprotein materials by a variety of methods that draw from the techniques of recombinant expression, chemical synthesis, enzymatic transformation, and chemoselective ligation. Some of these techniques remove obstacles to glycoprotein synthesis by installing nonnative linkages and other modifications for facilitated assembly. The end purpose of the described approaches is the production of glycosylated materials for experiments relevant to the biological investigation of glycoproteins, although the strategies presented apply to other posttranslational modifications as well.
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Affiliation(s)
- Michael J Grogan
- Department of Chemistry, University of California; Berkeley California 94720, USA.
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95
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Magnusson P, Sharp CA, Farley JR. Different distributions of human bone alkaline phosphatase isoforms in serum and bone tissue extracts. Clin Chim Acta 2002; 325:59-70. [PMID: 12367767 DOI: 10.1016/s0009-8981(02)00248-6] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
BACKGROUND In vitro, bone alkaline phosphatase (BALP) is released from the osteoblast membrane with its glycosylphosphatidylinositol (GPI) anchor still attached (i.e., in an anchor-intact form); however, in vivo, BALP circulates as a variable mixture of anchorless isoforms, which can be identified by high-performance liquid chromatography (HPLC). Previous studies have shown that the relative abundance of these BALP isoforms in serum may be clinically useful for the diagnosis and management of metabolic bone disease. METHODS In the current studies, we describe a method for the determination of anchorless BALP isoforms in extracts of bone and we present novel data on the conversion of anchor-intact to anchorless BALP by incubation with endogenous circulating GPI-specific phospholipase D (GPI-PLD). RESULTS A 72-h extraction with 0.1% Triton X-100 released approximately 90% of the BALP activity from powdered bone. An average of 19% of this activity was anchorless, but essentially all of the activity could be converted to the anchorless form by incubation with partially purified GPI-PLD from human serum. Using HPLC, we detected four BALP isoforms (B/I, B1x, B1, and B2) in these GPI-PLD-treated extracts of bone. An additional BALP fraction was also detected in the samples during the initial phase of GPI-PLD treatment. CONCLUSIONS The abundance of the BALP isoforms differed between bone and serum, particularly for the B/I isoform, which comprised, on average, 18% of the BALP in GPI-PLD-treated extracts of healthy bone tissue, but only 6% of the total BALP activity in serum from healthy individuals. Based on our recent finding of differences in the number of sialic acid residues between the BALP isoforms, we hypothesize that this difference between BALP isoforms in serum and extracts of bone is due to the different patterns of glycosylation, which results in different biological half-lives in the circulation. A preliminary application of our method to the extraction of BALP isoforms from a small number of human bone samples suggests that the method should be useful for studies of human skeletal site-specific and metabolic bone disease-specific differences in the amounts and distributions of the BALP isoforms in bone.
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Affiliation(s)
- Per Magnusson
- Department of Biomedicine and Surgery, Bone and Mineral Metabolic Unit, Division of Clinical Chemistry, Linköping University Hospital, SE-581-85 Linköping, Sweden.
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96
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Abstract
The critical role of the heterogeneous nature of cellular plasma membranes in transmembrane signal transduction has become increasingly appreciated during the past decade. Areas of relatively disordered, loosely packed phospholipids are disrupted by hydrophobic detergent/carbonate-insoluble glycolipid-enriched raft microdomains (DIGs) of highly ordered (glyco)sphingolipids and cholesterol. DIGs exhibit low buoyant density and are often enriched in glycosylphosphatidylinositol-anchored plasma membrane proteins (GPI proteins), dually acylated signalling proteins, such as non-receptor tyrosine kinases (NRTKs), and caveolin. At least two types of DIGs, hcDIGs and lcDIGs, can be discriminated on basis of higher and lower content, respectively, of these typical DIGs components. In quiescent differentiated cells, GPI proteins and NRTKs are mainly associated with hcDIGs, however, in adipose cells certain insulin-mimetic stimuli trigger redistribution of subsets of GPI proteins and NRTKs from hcDIGs to lcDIGs. Presumably, these stimuli induce displacement of GPI proteins from a GPI receptor located at hcDIGs whereas simultaneously NRTKs dissociate from a complex with caveolin located at hcDIGs, too. NRTKs are thereby activated and, in turn, modulate intracellular signalling pathways, such as stimulation of metabolic insulin signalling in insulin-sensitive cells. The apparent dynamics of DIGs may provide a target mechanism for regulating the activity of lipid-modified signalling proteins by small drug molecules, as exemplified by the sulfonylurea, glimepiride, which lowers blood glucose in an insulin-independent fashion, in part.
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Affiliation(s)
- Günter Müller
- Aventis Pharma Germany, DG Metabolic Diseases, Industrial Park Höchst, Bldg. H825, 65926, Frankfurt am Main, Germany.
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97
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Becker Kojić ZA, Terness P. A novel human erythrocyte glycosylphosphatidylinositol (GPI)-anchored glycoprotein ACA. Isolation, purification, primary structure determination, and molecular parameters of its lipid structure. J Biol Chem 2002; 277:40472-8. [PMID: 12167612 DOI: 10.1074/jbc.m202416200] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A method has been elaborated to isolate and purify up to homogeneity a novel membrane glycoprotein containing a glycosyl-phosphatidylinositol (GPI) anchor by means of salting out with ammonium sulfate (40-80% saturation), followed by preparative SDS-PAGE, chromatography and acetone precipitation. The preparation obtained was homogeneous upon electrophoresis in the presence of 0.1% SDS after reduction with 2-mercaptoethanol. It is protein-soluble at its isoelectrical point (pH 5.5) with molecular mass of 65,000 daltons. The isolated protein is linked to the membrane via glycosyl-phosphatidylinositol susceptible to cleavage by purified phospholipase C. The hydrophobic portion of the glycolipid membrane anchor of the protein was radiolabeled with the photoactivated reagent 3-(trifluoromethyl)-3-(m-[(125)I]iodophenyl)diazirine and hydrolyzed with glycosyl-phosphatidylinositol-specific phospholipase C, followed by enzymatic deacetylation of the remaining lipid. Thin-layer chromatography showed that the generated radiolabeled fragment migrates with the same mobility as that of variant surface glycoprotein (VSG), obtained in the same manner. In this study we describe a novel erythrocyte membrane GPI-linked protein with the structural feature of an anchor that, in contrast to other GPI-linked erythrocyte proteins, has a non-acetylated inositol ring and diacylglycerol rather than alkyl-acyl glycerol as a lipid tail of the anchor.
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Affiliation(s)
- Zorica A Becker Kojić
- Institute of Immunology, Department of Transplantation Immunology, University of Heidelberg, Otto Meyerhof Centre, Terness Laboratory, Im Neuenheimer Feld 305, 69120 Heidelberg, Germany.
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98
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Smith TK, Gerold P, Crossman A, Paterson MJ, Borissow CN, Brimacombe JS, Ferguson MAJ, Schwarz RT. Substrate specificity of the Plasmodium falciparum glycosylphosphatidylinositol biosynthetic pathway and inhibition by species-specific suicide substrates. Biochemistry 2002; 41:12395-406. [PMID: 12369829 DOI: 10.1021/bi020351l] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The substrate specificities of the early glycosylphosphatidylinositol biosynthetic enzymes of Plasmodium were determined using substrate analogues of D-GlcN(alpha)1-6-D-myo-inositol-1-HPO(4)-sn-1,2-dipalmitoylglycerol (GlcN-PI). Similarities between the Plasmodium and mammalian (HeLa) enzymes were observed. These are as follows: (i) The presence and orientation of the 2'-acetamido/amino and 3'-OH groups are essential for substrate recognition for the de-N-acetylase, inositol acyltransferase, and first mannosyltransferase enzymes. (ii) The 6'-OH group of the GlcN is dispensable for the de-N-acetylase, inositol acyltransferase, all four of the mannosyltransferases, and the ethanolamine phosphate transferase. (iii) The 4'-OH group of GlcNAc is not required for recognition, but substitution interferes with binding to the de-N-acetylase. The 4'-OH group of GlcN is essential for the inositol acyltransferase and first mannosyltransferase. (iv) The carbonyl group of the natural 2-O-hexadecanyl ester of GlcN-(acyl)PI is essential for substrate recognition by the first mannosyltransferase. However, several differences were also discovered: (i) Plasmodium-specific inhibition of the inositol acyltransferase was detected with GlcN-[L]-PI, while GlcN-(2-O-alkyl)PI weakly inhibited the first mannosyltransferase in a competitive manner. (ii) The Plasmodium de-N-acetylase can act on analogues containing N-benzoyl, GalNAc, or betaGlcNAc whereas the human enzyme cannot. Using the parasite specificity of the later two analogues with the known nonspecific de-N-acetylase suicide inhibitor [Smith, T. K., et al. (2001) EMBO J. 20, 3322-3332], GalNCONH(2)-PI and GlcNCONH(2)-beta-PI were designed and found to be potent (IC(50) approximately 0.2 microM), Plasmodium-specific suicide substrate inhibitors. These inhibitors could be potential lead compounds for the development of antimalaria drugs.
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Affiliation(s)
- Terry K Smith
- Division of Biological Chemistry and Molecular Microbiology, The School of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, UK
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99
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Morandat S, Bortolato M, Roux B. Cholesterol-dependent insertion of glycosylphosphatidylinositol-anchored enzyme. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1564:473-78. [PMID: 12175931 DOI: 10.1016/s0005-2736(02)00497-2] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Evidence is now accumulating that the plasma membrane is organized in different lipid and protein subdomains. Thus, glycosylphosphatidylinositol (GPI)-anchored proteins are proposed to be clustered in membrane microdomains enriched in cholesterol and sphingolipids, called rafts. By a detergent-mediated method, alkaline phosphatase, a GPI-anchored enzyme, was efficiently inserted into the membrane of sphingolipids- and cholesterol-rich liposomes as demonstrated by flotation in sucrose gradients. We have determined the enzyme extraluminal orientation. Using defined lipid components to assess the possible requirements for GPI-anchored protein insertion, we have demonstrated that insertion into membranes was cholesterol-dependent as the cholesterol addition increased the enzyme incorporation in simple phosphatidylcholine liposomes.
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Affiliation(s)
- Sandrine Morandat
- Laboratoire de Physico-Chimie Biologique, UMR-CNRS 5013, Bâtiment Chevreul, Université Claude Bernard Lyon I, 43, boulevard du 11 novembre 1918, F-69622 Villeurbanne Cedex, France
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100
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Bortolato M, Besson F, Roux B. An infrared study of the thermal and pH stabilities of the GPI-alkaline phosphatase from bovine intestine. Biochem Biophys Res Commun 2002; 292:874-9. [PMID: 11944895 DOI: 10.1006/bbrc.2002.6735] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Alkaline phosphatase (EC 3.1.3.1) from bovine intestine mucosa (BIAP) is a homodimeric metalloenzyme, which hydrolyses nonspecifically phosphate monoesters at alkaline pH with release of inorganic phosphate and alcohol. BIAP is either soluble (sBIAP) or membrane-anchored by a glycosylphosphatidylinositol moiety (GPI-BIAP). This anchor might have some contribution in the stabilization of the GPI-linked protein structure. Our purpose was to study the role of the anchor by using two parameters, the enzymatic activity and the protein conformation, which was analyzed by using FTIR spectroscopy. We determined that the two forms of BIAP show some similarities with the previously described structure of alkaline phosphatase isolated from Escherichia coli and human placenta. Meanwhile GPI-BIAP and sBIAP exhibit similar specific activities, the presence of the anchor increases the thermal and pH stabilities of the enzyme activity and conformation.
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Affiliation(s)
- Muriel Bortolato
- Laboratoire de Physico-Chimie Biologique, UMR-CNRS 5013, Université Claude Bernard Lyon I, 43, Villeurbanne Cedex, F-69622, France.
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