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Palestini P, Calvi C, Conforti E, Daffara R, Botto L, Miserocchi G. Compositional changes in lipid microdomains of air-blood barrier plasma membranes in pulmonary interstitial edema. J Appl Physiol (1985) 2003; 95:1446-52. [PMID: 12794031 DOI: 10.1152/japplphysiol.00208.2003] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
We evaluated in anesthetized rabbits the compositional changes of plasmalemmal lipid microdomains from lung tissue samples after inducing pulmonary interstitial edema (0.5 ml/kg for 3 h, leading to approximately 5% increase in extravascular water). Lipid microdomains (lipid rafts and caveolae) were present in the detergent-resistant fraction (DRF) obtained after discontinuous sucrose density gradient. DRF was enriched in caveolin-1, flotillin, aquaporin-1, GM1, cholesterol, sphingomyelin, and phosphatidylserine, and their contents significantly increased in interstitial edema. The higher DRF content in caveolin, flotillin, and aquaporin-1 and of the ganglioside GM1 suggests an increase both in caveolar domains and in lipid rafts, respectively. Compositional changes could be ascribed to endothelial and epithelial cells that provide most of plasma membrane surface area in the air-blood barrier. Alterations in lipid components in the plasma membrane may reflect rearrangement of floating lipid platforms within the membrane and/or lipid translocation from intracellular stores. Lipid traffic could be stimulated by the marked increase in hydraulic interstitial pressure after initial water accumulation, from approximately -10 to 5 cmH2O, due to the low compliance of the pulmonary tissue, in particular in the basement membranes and in the interfibrillar substance. Compositional changes in lipid microdomains represent a sign of cellular activation and suggest the potential role of mechanotransduction in response to developing interstitial edema.
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Affiliation(s)
- Paola Palestini
- Dipartimento di Medicina Sperimentale, Ambientale e Biotecnologie Mediche, Università di Milano-Bicocca, Via Cadore 48, 20052 Monza, MI Italy
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52
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Asaki C, Usuda N, Nakazawa A, Kametani K, Suzuki T. Localization of translational components at the ultramicroscopic level at postsynaptic sites of the rat brain. Brain Res 2003; 972:168-76. [PMID: 12711090 DOI: 10.1016/s0006-8993(03)02523-x] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
We investigated the localization of components of translational machinery and their regulators in the postsynaptic region. We examined several components, especially those involved in translational regulation: components of (1) MAPK-Mnk-eIF4E, (2) PI3-kinase-PDK-Akt/PKB-FRAP/mTOR-PHAS/4EBP, (3) p70S6K-S6 ribosomal protein and (4) eEF2 kinase/CaMKIII-eEF2 pathways. Western blotting detected all the components examined in the synaptic fractions, and their differential localization to the synaptic subcompartments: initiation or elongation factors, except for eIF5, were detected predominantly in the dendritic lipid raft fraction, which contained ER marker proteins. In contrast, most of their regulatory kinases were distributed to both the postsynaptic density (PSD) and the dendritic lipid raft fractions, or enriched in the former fraction. Localization of eIF4E at synaptic sites was further examined immunohistochemically at the electron microscopic level. The eIF-4E-immunoreactivity was localized to the postsynaptic sites, especially to the microvesicle-like structures underneath the postsynaptic membrane in the spine, some of which were localized in close proximity to PSD. These results suggest that the postsynaptic local translational system, in at least four major regulatory pathways, is similar to those in the perinuclear one, and that it takes place, at least partly, immediately beneath the postsynaptic membrane. The results also suggest the presence of ER-associated type of translational machinery at the postsynaptic sites.
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Affiliation(s)
- Chie Asaki
- Department of Neuroplasticity, Research Center on Aging and Adaptation, Shinshu University, 3-1-1 Asahi, Matsumoto 390-8621, Japan
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53
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Fourgeaud L, Bessis AS, Rossignol F, Pin JP, Olivo-Marin JC, Hémar A. The metabotropic glutamate receptor mGluR5 is endocytosed by a clathrin-independent pathway. J Biol Chem 2003; 278:12222-30. [PMID: 12529370 DOI: 10.1074/jbc.m205663200] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Metabotropic glutamate receptors 5 (mGluR5) are members of the growing group C G protein-coupled receptor family. Widely expressed in mammalian brain, they are involved in modulation of the glutamate transmission. By means of transfection of mGluR5 receptors in COS-7 cells and primary hippocampal neurons in culture followed by immunocytochemistry and quantitative image analysis and by a biochemical assay, we have studied the internalization of mGluR5 splice variants. mGluR5a and -5b were endocytosed in COS-7 cells as well as in axons and dendrites of cultured neurons. Endocytosis occurred even in the absence of receptor activity, because receptors mutated in the glutamate binding site were still internalized as well as receptors in which endogenous activity had been inhibited by an inverse agonist. We have measured a constitutive rate of endocytosis of 11.7%/min for mGluR5a. We report for the first time the endocytosis pathway of mGluR5. Internalization of mGluR5 is not mediated by clathrin-coated pits. Indeed, inhibition of this pathway by Eps15 dominant negative mutants did not disturb their endocytosis. However, the large GTPase dynamin 2 is implicated in the endocytosis of mGluR5 in COS-7. mGluR5 is the first shown member of the group C G-protein coupled receptor family internalized by a nonconventional pathway.
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Affiliation(s)
- Lawrence Fourgeaud
- Physiologie Cellulaire de la Synapse, UMR 5091 CNRS/Université Bordeaux 2, France
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54
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Maekawa S, Iino S, Miyata S. Molecular characterization of the detergent-insoluble cholesterol-rich membrane microdomain (raft) of the central nervous system. BIOCHIMICA ET BIOPHYSICA ACTA 2003; 1610:261-70. [PMID: 12648779 DOI: 10.1016/s0005-2736(03)00023-3] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Many fundamental neurological issues such as neuronal polarity, the formation and remodeling of synapses, synaptic transmission, and the pathogenesis of the neuronal cell death are closely related to the membrane dynamics. The elucidation of functional roles of a detergent-insoluble cholesterol-rich domain (raft) could therefore provide good clues to the molecular understanding of these important phenomena, for the participation of the raft in the fundamental cell functions, such as signal transduction and selective transport of lipids and proteins, has been elucidated in nonneural cells. Interestingly, the brain is rich in raft and the brain-derived raft differs in its lipid and protein components from other tissue-derived rafts. Since many excellent reviews are written on the membrane lipid dynamics of this microdomain, signal transduction, and neuronal glycolipids, we review on the characterization of the raft proteins recovered in the detergent-insoluble low-density fraction from rat brain. Special focus is addressed on the biochemical characterization of a neuronal enriched protein, NAP-22, for the lipid organizing activity of this protein has become increasingly clear.
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Affiliation(s)
- Shohei Maekawa
- Department of Life Science, Graduate School of Science and Technology, Kobe University, Rokkodai 1-1, Kobe 657-8501, Japan.
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55
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Noyama K, Maekawa S. Localization of cyclic nucleotide phosphodiesterase 2 in the brain-derived Triton-insoluble low-density fraction (raft). Neurosci Res 2003; 45:141-8. [PMID: 12573460 DOI: 10.1016/s0168-0102(02)00208-0] [Citation(s) in RCA: 20] [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
The cyclic nucleotides perform a variety of roles in the formation and remodeling of the neuronal interaction. The membrane microdomain called "raft" has been paid much attention, for this domain contains many signal-transducing molecules including trimeric G proteins and cytoskeletal proteins. The raft domain is recovered in a low-density fraction after the treatment of the membrane with a non-ionic detergent such as Triton X-100. The enrichment of cholesterol and sphingolipids is ascribed to be responsible for the detergent insolubility. In this study we focused on the cyclic nucleotide signaling process in rafts prepared from the cerebral cortex of 10-day-old rat and the synaptic plasma membrane fraction and found the presence of a high cAMP and cGMP phosphodiesterase (PDE) activity. The activity was effectively inhibited with erythro-9-(2-hydroxy-3-nonyl)adenine, a PDE2-specific inhibitor but not with other inhibitors such as vinpocetine, quazione, or zaprinast. Further western blotting analysis confirmed the localization of PDE2 in the raft fraction. The presence of adenylyl cyclase V/VI and PKA in the raft fraction was also shown with Western blotting. These results suggest the participation of the raft in the cyclic nucleotide signaling cascade in neurons.
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Affiliation(s)
- Kenjiro Noyama
- Division of Bioinformation, Department of Life Science, Graduate School of Science and Technology, Kobe University, Rokkodai 1-1, Nada-ku, Kobe 657-8501, Japan
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56
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Limatola C, Di Bartolomeo S, Trettel F, Lauro C, Ciotti MT, Mercanti D, Castellani L, Eusebi F. Expression of AMPA-type glutamate receptors in HEK cells and cerebellar granule neurons impairs CXCL2-mediated chemotaxis. J Neuroimmunol 2003; 134:61-71. [PMID: 12507773 DOI: 10.1016/s0165-5728(02)00401-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
We find that cerebellar granule neurons (CGN) obtained from newborn rats (p3) migrate in response to both CXC chemokine ligand-2 (CXCL2) and -12 (CXCL12), while CGN from p7 rats are unresponsive to CXCL2. The expression of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA)-type glutamate receptor 1 (GluR1) greatly impairs the chemotaxis induced by CXCL2 in CXCR2-expressing HEK cells. By immunoprecipitation, we show that CXCR2 is associated with AMPA receptors (AMPARs) in p7 CGN, and with GluR1 co-expressed in HEK cells. Taken together, these results suggest that the association between CXCR2 and AMPARs results in the inhibition of CXCL2-dependent chemotaxis, and may represent a molecular mechanism underlying the modulation of nerve cell migration.
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MESH Headings
- Age Factors
- Animals
- Animals, Newborn
- Cell Membrane/immunology
- Cell Membrane/metabolism
- Cell Movement/immunology
- Cells, Cultured
- Central Nervous System/cytology
- Central Nervous System/growth & development
- Central Nervous System/metabolism
- Cerebellar Cortex/cytology
- Cerebellar Cortex/growth & development
- Cerebellar Cortex/metabolism
- Chemokine CXCL1
- Chemokine CXCL2
- Chemokines/immunology
- Chemokines/metabolism
- Chemokines, CXC
- Chemotactic Factors/immunology
- Chemotactic Factors/metabolism
- Chemotaxis/immunology
- Excitatory Amino Acid Antagonists/pharmacology
- Gene Expression Regulation, Developmental/physiology
- Humans
- Intercellular Signaling Peptides and Proteins/immunology
- Intercellular Signaling Peptides and Proteins/metabolism
- Neuroimmunomodulation/physiology
- Neurons/cytology
- Neurons/metabolism
- Precipitin Tests
- Rats
- Rats, Wistar
- Receptors, AMPA/antagonists & inhibitors
- Receptors, AMPA/genetics
- Receptors, AMPA/immunology
- Receptors, AMPA/metabolism
- Receptors, Interleukin-8B/immunology
- Receptors, Interleukin-8B/metabolism
- Signal Transduction/immunology
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Affiliation(s)
- Cristina Limatola
- Dipartimento di Fisiologia Umana e Farmacologia, Università di Roma La Sapienzo, Piazzale Aldo Moro 5, I00185 Rome, Italy.
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57
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Silva VS, Cordeiro JM, Matos MJ, Oliveira CR, Gonçalves PP. Aluminum accumulation and membrane fluidity alteration in synaptosomes isolated from rat brain cortex following aluminum ingestion: effect of cholesterol. Neurosci Res 2002; 44:181-93. [PMID: 12354633 DOI: 10.1016/s0168-0102(02)00128-1] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In the present work, we studied the effect of cholesterol/phospholipid (CH/PL) molar ratio on aluminum accumulation and aluminum-induced alteration of membrane fluidity in rat brain cortex synaptosomes. We observed that sub-acute (daily supply of 1.00 g of AlCl(3) during 10 days) and chronic (daily supply of 0.03 g of AlCl(3) during 4 months) exposure to dietary aluminum leads to a synaptosomal aluminum enrichment of 45 and 59%, respectively. During chronic exposure to AlCl(3), the enhancement of aluminum content was prevented by administration of colestipol (0.31 g/day), which decreased the synaptosomal membrane CH/PL molar ratio (nmol/nmol) from 1.2 to 0.4. Fluorescence anisotropy analysis, using 1,6-diphenyl-1,3,5-hexatriene (DPH) and 1-(4-(trimethylamino)phenyl)-6-phenylhexa-1,3,5-triene (TMA-DPH), showed that after treatment with colestipol a decrease in membrane order occurs at the level of hydrophilic lipid-water surface and deeper hydrophobic region of the synaptosomal membrane. When the rats were exposed to aluminum, it was observed a significant enhancement of membrane fluidity, which was more pronounced at the level of the membrane hydrophilic regions. Meanwhile, when chronic exposure to dietary AlCl(3) was accompanied by treatment with colestipol, the aluminum-induced decrease in membrane order was negligible when compared to TMA-DPH and DPH anisotropy values measured upon colestipol treatment. In contrast, in vitro incubation of synaptosomes (isolated from control rats) with AlCl(3) induced a concentration-dependent rigidification of this more hydrophilic membrane region. The opposite action of aluminum on synaptosomal membrane fluidity, during in vivo and in vitro experiments, appears to be explained by alteration of synaptosomal CH/PL molar ratio, since a significant reduction (approximately 80%) of this parameter occurs during in vivo exposure to aluminum. In conclusion, during in vivo exposure to aluminum, fluidification of hydrophilic regions and reduction of CH/PL molar ratio of presynaptic membranes accompany the accumulation of this cation, which appear to restrict aluminum retention in brain cortex nerve terminals.
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Affiliation(s)
- Virgília S Silva
- Centro de Estudos do Ambiente e Mar, Departamento de Biologia, Universidade de Aveiro, 3810-193 Aveiro, Portugal
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58
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Deregulation of cdk5, hyperphosphorylation, and cytoskeletal pathology in the Niemann-Pick type C murine model. J Neurosci 2002. [PMID: 12151531 DOI: 10.1523/jneurosci.22-15-06515.2002] [Citation(s) in RCA: 132] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
NPC-1 gene mutations cause Niemann-Pick type C (NPC), a neurodegenerative storage disease resulting in premature death in humans. Spontaneous mutation of the NPC-1 gene in mice generates a similar phenotype, usually with death ensuing by 12 weeks of age. Both human and murine NPC are characterized neuropathologically by ballooned neurons distended with lipid storage, axonal spheroid formation, demyelination, and widespread neuronal loss. To elucidate the biochemical mechanism underlying this neuropathology, we have investigated the phosphorylation of neuronal cytoskeletal proteins in the brains of npc-1 mice. A spectrum of antibodies against phosphorylated epitopes in neurofilaments (NFs) and MAP2 and tau were used in immunohistochemical and immunoblotting analyses of 4- to 12-week-old mice. Multiple sites in NFs, MAP2, and tau were hyperphosphorylated as early as 4 weeks of age and correlated with a significant increase in activity of the cyclin-dependent kinase 5 (cdk5) and accumulation of its more potent activator, p25, a proteolytic fragment of p35. At 5 weeks of age, the development of axonal spheroids was noted in the pons. p25 and cdk5 coaccumulated with hyperphosphorylated cytoskeletal proteins in axon spheroids. These various abnormalities escalated with each additional week of age, spreading to other regions of the brainstem, basal ganglia, cerebellum, and eventually, the cortex. Our data suggest that focal deregulation of cdk5/p25 in axons leads to cytoskeletal abnormalities and eventual neurodegeneration in NPC. The npc-1 mouse is a valuable in vivo model for determining how and when cdk5 becomes deregulated and whether cdk5 inhibitors would be useful in blocking NPC neurodegeneration.
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59
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Rizzo AM, Rossi F, Berra B. Glycosyltransferases in different brain regions during chick embryo development. Neurochem Res 2002; 27:815-21. [PMID: 12374218 DOI: 10.1023/a:1020213209078] [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: 11/12/2022]
Abstract
Glycosphingolipids, in particular gangliosides, play a crucial role in neuronal development and are known to change dramatically in total content and distribution in different brain areas during embryogenesis. In the present work we analyzed the activity of enzymes involved in the metabolism of gangliosides, at different periods of functional maturation in different regions of chick embryo brain. Our data demonstrate differences in the enzymatic activities in the examined areas; these differences might be correlated with the functional lateralization occurring in the brain during development. Significative differences were found in glycosphingolipid composition between controlateral cerebral hemispheres and optic lobes; these results together with previous data we found, contribute to reinforce our hypothesis on the occurrence of biochemical lateralization during early brain development.
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Affiliation(s)
- Angela M Rizzo
- Institute of General Physiology and Biochemistry, School of Pharmacy, University of Milan, Italy
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60
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Prioni S, Loberto N, Prinetti A, Chigorno V, Guzzi F, Maggi R, Parenti M, Sonnino S. Sphingolipid metabolism and caveolin expression in gonadotropin-releasing hormone-expressing GN11 and gonadotropin-releasing hormone-secreting GT1-7 neuronal cells. Neurochem Res 2002; 27:831-40. [PMID: 12374220 DOI: 10.1023/a:1020217309987] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
In this paper, we show that caveolin-1 is abundantly present in a cell line of immortalized gonadotropin-releasing hormone-expressing neurons (GN11). In contrast to GN11, caveolin is undetectable in a cognate cell line of immortalized gonadotropin-releasing hormone-secreting neurons (GT1-7). These two cell lines are characterized by a radically different sphingolipid metabolism. After incubation in the presence of tracer amount of [1-(3)H]sphingosine, GN11 and GT1-7 neurons incorporated similar amounts of radioactivity. In GT1-7 neurons, [1-(3)H]sphingosine metabolism was markedly oriented toward the biosynthesis of complex sphingolipids. In fact, almost all the radioactivity in the lipid extracts from GT1-7 cells was associated with biosynthetic products (ceramide, sphingomyelin, and glycosphingolipids). In particular glycosphingolipids represented more than 65% of total lipid radioactivity in these cells, and the main glycosphingolipid was GM3 ganglioside (about 47% of total lipid radioactivity). In the case of GN11 neurons, a high portion of [1-(3)H]sphingosine underwent complete degradation, as indicated by the formation of high levels of radioactive phosphatidylethanolamine (about 23% of lipid radioactivity). Moreover, the main complex sphingolipid in GN11 neurons was not a glycolipid, but sphingomyelin (its level in these cells, about 54% of lipid radioactivity, was two-fold higher than in GT1-7). Glycolipids, gangliosides in particular, were present in low amount (9.5% of lipid radioactivity) if compared with the cognate GT1-7 cell line, and GM3 was almost absent in GN11 neurons. Despite the radical differences in ganglioside and caveolin content, from both cell types a membrane fraction similarly enriched in sphingolipids was prepared. In the case of GN11 cells, this fraction was also enriched in caveolin. The presence of caveolin or GM3 may correlate with different functional properties linked to the stage of neuronal maturation, since GN11 and GT1-7 are representative, respectively, of immature, migrating, and differentiated, postmigratory gonadotropin-releasing hormone-positive neurons.
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Affiliation(s)
- Simona Prioni
- Center of Excellence on Neurodegenerative Diseases, University of Milano, Italy
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61
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Kasahara K, Watanabe K, Kozutsumi Y, Oohira A, Yamamoto T, Sanai Y. Association of GPI-anchored protein TAG-1 with src-family kinase Lyn in lipid rafts of cerebellar granule cells. Neurochem Res 2002; 27:823-9. [PMID: 12374219 DOI: 10.1023/a:1020265225916] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
We have demonstrated that antibody-mediated crosslinking of GPI-anchored TAG-1 induced activation of src-family kinase Lyn and rapid tyrosine phosphorylation of an 80-kDa protein (p80), a putative substrate for Lyn, in the lipid raft fraction prepared from primary cerebellar cultures, suggesting the functional association of TAG-1 with Lyn in lipid rafts of the rat cerebellum. In this study, the association was confirmed using a cDNA expression system. TAG-1-expressing CHO transfectants exhibited enhanced self-aggregation and promoted neurite outgrowth of primary cerebellar cultures as a culture substrate. The anti-TAG-1 antibody co-immunoprecipitated Lyn with TAG-1 and induced co-patching of TAG-1 with Lyn in both TAG-1 and Lyn-expressing CHO transfectants. Density gradient analysis revealed that TAG-1 is present in the lipid raft fraction of the CHO transfectants. Furthermore, pretreatment with a sphingolipid biosynthesis inhibitor ISP-1 reduced the extent of tyrosine phosphorylation of p80 by the antibody-mediated crosslinking of TAG-1. Immunocytochemical study showed that both TAG-1 and Lyn are present in cerebellar granule cells. These observations suggest that TAG-1 associates with Lyn in lipid rafts of rat cerebellar granule cells.
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Affiliation(s)
- Kohji Kasahara
- Department of Biochemical Cell Research, The Tokyo Metropolitan Institute of Medical Science, Tokyo Metropolitan Organization for Medical Research, Japan
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62
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Brocca P, Cantù L, Corti M, Del Favero E, Raudino A. Cooperative behavior of ganglioside molecules in model systems. Neurochem Res 2002; 27:559-63. [PMID: 12374190 DOI: 10.1023/a:1020255529125] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
A concise discussion of the role of different geometrical conformational states in the process of self-assembling of gangliosides is given. The report focuses on the effects of the geometrical variations occurring in the head group region of gangliosides as reflected on the geometrical properties of the whole assembly. Collective phenomena happening at the water interfacial region are found to be coupled to the phase transition of the lipid moiety, that is, to the well-known order-disorder conformational transition involving the hydrophobic tails. The possible biological relevance of the head group bistability is envisaged.
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Affiliation(s)
- Paola Brocca
- Dipartimento di Chimica e Biochimica Medica, I.N.F.M., Università di Milano, Segrate, Italy
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63
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Yamauchi S, Tokita Y, Aono S, Matsui F, Shuo T, Ito H, Kato K, Kasahara K, Oohira A. Phosphorylation of neuroglycan C, a brain-specific transmembrane chondroitin sulfate proteoglycan, and its localization in the lipid rafts. J Biol Chem 2002; 277:20583-90. [PMID: 11929867 DOI: 10.1074/jbc.m200909200] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Neuroglycan C (NGC) is a brain-specific transmembrane chondroitin sulfate proteoglycan. In the present study, we examined whether NGC could be phosphorylated in neural cells. On metabolic labeling of cultured cerebral cortical cells from the rat fetus with (32)P(i), serine residues in NGC were radiolabeled. Some NGC became detectable in the raft fraction from the rat cerebrum, a signaling microdomain of the plasma membrane, with cerebral development. NGC from the non-raft fraction, not the raft fraction, could be phosphorylated by an in vitro kinase reaction. The phosphorylation of NGC was inhibited by adding to the reaction mixture a recombinant peptide representing the ectodomain of NGC, but not by adding a peptide representing its cytoplasmic domain. NGC could be labeled by an in vitro kinase reaction using [gamma-(32)P]GTP as well as [gamma-(32)P]ATP, and this kinase activity was partially inhibited by 5,6-dichloro-1-beta-d-ribofuranosylbenzimidazole, a selective inhibitor of casein kinase II. In addition to the intracellular phosphorylation, NGC was also phosphorylated at the cell surface by an ectoprotein kinase. This is the first report to demonstrate that NGC can be phosphorylated both intracellularly and pericellularly, and our findings suggest that a kinase with a specificity similar to that of casein kinase II is responsible for the NGC ectodomain phosphorylation.
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Affiliation(s)
- Shinobu Yamauchi
- Institute for Developmental Research, Aichi Human Service Center, Kasugai, Aichi 480-0392, Japan
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64
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Duchemin AM, Ren Q, Mo L, Neff NH, Hadjiconstantinou M. GM1 ganglioside induces phosphorylation and activation of Trk and Erk in brain. J Neurochem 2002; 81:696-707. [PMID: 12065629 DOI: 10.1046/j.1471-4159.2002.00831.x] [Citation(s) in RCA: 122] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We investigated the ability of GM1 to induce phosphorylation of the tyrosine kinase receptor for neurotrophins, Trk, in rat brain, and activation of possible down-stream signaling cascades. GM1 increased phosphorylated Trk (pTrk) in slices of striatum, hippocampus and frontal cortex in a concentration- and time-dependent manner, and enhanced the activity of Trk kinase resulting in receptor autophosphorylation. The ability of GM1 to induce pTrk was shared by other gangliosides, and was blocked by the selective Trk kinase inhibitors K252a and AG879. GM1 induced phosphorylation of TrkA > TrkC > TrkB in a region-specific distribution. Adding GM1 to brain slices activated extracellular-regulated protein kinases (Erks) in all three brain regions studied. In striatum, GM1 elicited activation of Erk2 > Erk1 in a time-and concentration-dependent manner. The GM1 effect on Erk2 was mimicked by other gangliosides, and was blocked by the Trk kinase inhibitors K252a and AG879. Pertussis toxin, as well as Src protein tyrosine kinase and protein kinase C inhibitors, did not prevent the GM1-induced activation of Erk2, apparently excluding the participation of Gi and Gq/11 protein-coupled receptors. Intracerebroventricular administration of GM1 induced a transient phosphorylation of TrkA and Erk1/2 in the striatum and hippocampus complementing the in situ studies. These observations support a role for GM1 in modulating Trk and Erk phosphorylation and activity in brain.
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Affiliation(s)
- Anne-Marie Duchemin
- Department of Psychiatry, The Ohio State University College of Medicine and Public Health, 1670 Upham Drive, Columbus, OH 43210, USA
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65
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Palestini P, Botto L, Guzzi F, Calvi C, Ravasi D, Masserini M, Pitto M. Developmental changes in the protein composition of sphingolipid- and cholesterol-enriched membrane domains of rat cerebellar granule cells. J Neurosci Res 2002; 67:729-38. [PMID: 11891786 DOI: 10.1002/jnr.10170] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The biological role of cell membrane domains has been investigated in a number of eukariotic cells, but less attention has been paid to the neuron. In the present investigation, we assessed the changes in lipid and protein composition of detergent-resistant membrane fractions prepared from cultured rat cerebellar granule cells, during differentiation and maturation in vitro. At any stage of the cell life, low-density, detergent-resistant fractions, characterised by the specific presence of prion protein, were enriched in glycolipids, cholesterol, and sphingomyelin. The enrichment in sphingomyelin was developmentally regulated, increasing continuously during cell differentiation and maturation. Concerning proteins, domains were enriched in Fyn and TAG-1, which present exclusively within this fraction at any stage of cell culture, and in GAP-43, mainly during the differentiation stage. On the other side, proteins affecting signal transduction and cytoskeleton-related proteins (heterotrimeric G-proteins, protein kinase C, MARCKS, tubulin), were not enriched within detergent-resistant fractions during cell differentiation, but were recovered within this fraction in mature neurons. These results indicate that during different cellular life stages, specific proteins are recruited within detergent-resistant membrane domains of the neuron and suggest their involvement in specific physiological phenomena (differentiation, maturation and/or aging).
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Affiliation(s)
- Paola Palestini
- Department of Experimental, Environmental Medicine and Biotechnologies (DIMESAB), University of Milano-Bicocca, Monza, Italy.
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66
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Abstract
Caveolea are special (highly hydrophobic) plasma membrane invaginations with a diameter of 50-100 nm. Their characteristic features are the flask- or omega-shape and the lack of basket-like coat composed of clathrin. Caveolin-an integral membrane protein-is the principal component of caveolae membranes in vivo. Multiple forms of caveolin have been identified: caveolin-1alpha, caveolin-1beta, caveolin-2 and caveolin-3. They differ in their specific properties and tissue distribution. In this paper we summarize the morphological and biochemical data providing strong evidence about the existence and function of caveolae in rat peritoneal macrophages. When studied electron microscopically, the surface of both resident and elicited macrophages exhibited omega- or flask-shaped plasma membrane invaginations. There was a significant difference, however, in the number of these profiles: whereas in resident cells only a small amount of them was found on the cell surface, in elicited cells they were abundantly present on the plasma membrane. Using an antibody against the VIP21/caveolin-1 isoform we showed that these plasma membrane pits were indeed caveolae. The number and the appearance of caveolae were found to be in close correlation with the functional activity of these phagocytotic cells, indicating that the formation of caveolae is a highly regulated process. Using Western blot analysis two different proteins ( approximately 29 and approximately 20 kDa)-both labelled with anti-caveolin antibodies-were identified in resident and elicited macrophages that have been isolated from rat peritoneal cavity. The approximately 20 kDa protein was labelled specifically only by anti-VIP21/caveolin-1, while the approximately 29 kDa protein was labelled by both anti-VIP21/caveolin-1 and anti-caveolin-2 antibodies. The presence of the approximately 29 kDa protein was highly characteristic of resident cells, and only a small amount of approximately 20 kDa protein was detected in these cells. Elicitation has resulted in a significant increase in the amount of approximately 20 kDa protein labeled only with anit-VIP21/caveolin-1. Our morphological (confocal and electron microscopical) studies have shown that in resident cells caveolin was present in the cytoplasm, in smaller vesicles and multivesicular bodies around the Golgi area. Only a very small amount of caveolae was found on the cell surface of these cells. In elicited macrophages, caveolae (labelled with anti-VIP21/caveolin-1 antibody) appeared in large numbers on the cell surface, but caveolin detected by anti-caveolin-2 was also found in small vesicles and multivesicular bodies. These data support the idea that the expression of the approximately 29 kDa (caveolin-related) protein is insufficient for caveolae formation in resident cells, it can function as a modified, macrophage-specific caveolin-2 isoform. Our results strongly suggest that caveolin-1 plays a crucial role in the formation of caveolae: it is the amount of caveolin-1 that regulates the appearance of caveolae on the plasma membrane. Studying the endocytotic processes of resident and elicited macrophages we have found that elicited macrophages bound and internalized significantly larger amounts of fluid phase marker (HRP) and immune complex (peroxidase-antiperoxidase-PAP) than resident cells. Serial section analysis, double labelled immunocytochemistry, and filipin treatment were used to demonstrate that caveolae can pinch off from the plasma membrane and can take part in endocytotic processes as alternative carriers in elicited macrophages.
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Affiliation(s)
- A L Kiss
- Department of Human Morphology and Developmental Biology, Semmelweis University, H-1450, Tûzoltó u. 58, Budapest, Hungary.
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67
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Masserini M, Ravasi D. Role of sphingolipids in the biogenesis of membrane domains. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1532:149-61. [PMID: 11470236 DOI: 10.1016/s1388-1981(01)00128-7] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
In recent years, a huge interest in sphingolipid- and cholesterol-enriched membrane domains has risen, after their involvement in fundamental membrane-associated events such as signal transmission, cell adhesion and lipid/protein sorting was postulated. Theoretical considerations and several experimental data suggest that sphingolipids play an important role in the biogenesis and function of domains. In fact, their physicochemical features, different from those of other membrane lipids, allow their interaction either with other sphingolipids or with other membrane components and external ligands. Owing to these features, sphingolipids may undergo segregation and represent a nucleation point for co-clustering with other lipids and proteins in a complex, functional domain. Moreover, sphingolipids confer dynamic properties on domains, a fundamental feature for the modulation of their postulated functions.
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Affiliation(s)
- M Masserini
- Department of Experimental, Environmental Medicine and Biotechnology, University of Milan-Bicocca, Via Cadore 48, 20052 Monza, Italy.
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68
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Prinetti A, Chigorno V, Prioni S, Loberto N, Marano N, Tettamanti G, Sonnino S. Changes in the lipid turnover, composition, and organization, as sphingolipid-enriched membrane domains, in rat cerebellar granule cells developing in vitro. J Biol Chem 2001; 276:21136-45. [PMID: 11264283 DOI: 10.1074/jbc.m010666200] [Citation(s) in RCA: 145] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In the present paper, we report on the properties of sphingolipid-enriched domains of rat cerebellar granule cells in culture at different stages of neuronal development. The major lipid components of these domains were glycerophospholipids and cholesterol. Glycerophospholipids were 45-75% and cholesterol 15-45% of total lipids of the domains. This corresponded to 5-17% of total cell glycerophospholipids and 15-45% of total cell cholesterol. Phosphatidylcholine, mainly dipalmitoylphosphatidylcholine, was 66-85% of all the glycerophospholipids associated with these domains. Consequently, the palmitoyl residue was significantly enriched in the domains. The surface occupied by these structures increased during development. 40-70% of cell sphingolipids segregated in sphingolipid-enriched membrane domains, with the maximum ganglioside density in fully differentiated neurons. A high content of ceramide was found in the domains of aging neurons. Then, the sphingolipid/glycerophospholipid molar ratio was more than doubled during the initial stage of development, whereas the cholesterol/glycerophospholipid molar ratio gradually decreased during in vitro differentiation. Phosphorylated phosphoinositides, which were scant in the domains of undifferentiated cells, dramatically increased during differentiation and aging in culture. Proteins were minor components of the domains (0.1-2.8% of all domain components). Phosphotyrosine-containing proteins were selectively recovered in the sphingolipid-enriched domain. Among these, Src family protein-tyrosine kinases, known to participate to the process of neuronal differentiation, were associated with the sphingolipid-enriched domains in a way specific for the type of kinase and for the developmental stage of the cell. Proteins belonging to other signaling pathways, such as phosphoinositide 3-kinase and its downstream target, Akt, were not associated with the domains.
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Affiliation(s)
- A Prinetti
- Study Center for the Functional Biochemistry of Brain Lipids, Department of Medical Chemistry, Medical School, University of Milan, Segrate, Italy 20090
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69
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Vinson M, Strijbos PJ, Rowles A, Facci L, Moore SE, Simmons DL, Walsh FS. Myelin-associated glycoprotein interacts with ganglioside GT1b. A mechanism for neurite outgrowth inhibition. J Biol Chem 2001; 276:20280-5. [PMID: 11279053 DOI: 10.1074/jbc.m100345200] [Citation(s) in RCA: 148] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Myelin-associated glycoprotein (MAG) is expressed on myelinating glia and inhibits neurite outgrowth from post-natal neurons. MAG has a sialic acid binding site in its N-terminal domain and binds to specific sialylated glycans and gangliosides present on the surface of neurons, but the significance of these interactions in the effect of MAG on neurite outgrowth is unclear. Here we present evidence to suggest that recognition of sialylated glycans is essential for inhibition of neurite outgrowth by MAG. Arginine 118 on MAG is known to make a key contact with sialic acid. We show that mutation of this residue reduces the potency of MAG inhibitory activity but that residual activity is also a result of carbohydrate recognition. We then go on to investigate gangliosides GT1b and GD1a as candidate MAG receptors. We show that MAG specifically binds both gangliosides and that both are expressed on the surface of MAG-responsive neurons. Furthermore, antibody cross-linking of cell surface GT1b, but not GD1a, mimics the effect of MAG, in that neurite outgrowth is inhibited through activation of Rho kinase. These data strongly suggest that interaction with GT1b on the neuronal cell surface is a potential mechanism for inhibition of neurite outgrowth by MAG.
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Affiliation(s)
- M Vinson
- Neurology Centre of Excellence for Drug Discovery, GlaxoSmithKline, New Frontiers Science Park North, Third Ave., Harlow, Essex CM19 5AW, United Kingdom
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70
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Suzuki T, Ito J, Takagi H, Saitoh F, Nawa H, Shimizu H. Biochemical evidence for localization of AMPA-type glutamate receptor subunits in the dendritic raft. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 2001; 89:20-8. [PMID: 11311972 DOI: 10.1016/s0169-328x(01)00051-1] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
A low density Triton-insoluble fraction with characteristic lipid composition was prepared from synaptic plasma membrane from the rat forebrain. The fraction was named dendritic raft based on its absence of the presynaptic marker synaptophysin, the presence of postsynaptic Glutamate receptor (GluR) subunits, and its resemblance to raft, caveolae-like structure. We found a differential distribution of NMDA-type and AMPA-type GluR subunits in the dendritic raft and postsynaptic density (PSD) fractions; the latter type GluR subunits were localized to the dendritic raft as well as PSD fraction, whereas the former type was mostly localized to the PSD fraction. We also found the differential distribution of the components of ras/mitogen-activated protein kinase (MAPK) pathway to the dendritic raft and PSD fractions. Dendritic raft and PSD may possibly interact at the postsynaptic sites for efficient signal processing that is required for expression of synaptic plasticity.
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Affiliation(s)
- T Suzuki
- Department of Neuroplasticity, Research Center on Aging and Adaptation, Shinshu University School of Medicine, Matsumoto 390-8621, Japan.
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71
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Usuki S, Ren J, Utsunomiya I, Cashman NR, Inokuchi J, Miyatake T. GM2 ganglioside regulates the function of ciliary neurotrophic factor receptor in murine immortalized motor neuron-like cells (NSC-34). Neurochem Res 2001; 26:375-82. [PMID: 11495348 DOI: 10.1023/a:1010999014657] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
We previously reported that ciliary neurotrophic factor (CNTF) increased the serum-free cell survival of immortalized motor neuron-like cells (NSC-34), and addition of the exogenous ganglioside GalNAc beta4(Neu5Ac alpha3)Gal beta4GlcCer (GM2) facilitated cell survival together with CNTF. Moreover beta 1,4 N-acetylgalactosaminyltransferase (GM2 synthase) activity increased in NSC-34 cells cultured with CNTF. We now have examined whether CNTF-induced cell survival is associated with the collaboration between GM2 and the CNTF receptor (CNTF-R). Despite the presence of CNTF (50 ng/ml), anti-CNTF-R antibody caused cell death and prevented the up-regulation of GM2 synthase expression. The addition of GM2 (1 to 20 microM) abrogated the anti-CNTF-R antibody effect which shortened cell survival and blocked GM2 synthase activation. Use of [125I]CNTF showed the specificity of CNTF binding in NSC-34 cells in situ. GM2 produced a 5-fold increase in the CNTF binding affinity per cell but did not change the binding site number. The study by metabolic labeling with [1-(14)C]N-acetyl-D-galactosamine ([14C]GalNAc) showed that biosynthesized GM2 was involved in the immunoprecipitation of CNTF-R. These findings indicate that up-regulated GM2 synthesis induces functional conversion of CNTF-R to the activated state, in which it has affinity for CNTF. We conclude that GM2 is a bio-regulating molecule of CNTF-R in motor neurons.
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Affiliation(s)
- S Usuki
- Tokyo Research Institute, Seikagaku Corporation, Japan
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72
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Shogomori H, Futerman AH. Cholera toxin is found in detergent-insoluble rafts/domains at the cell surface of hippocampal neurons but is internalized via a raft-independent mechanism. J Biol Chem 2001; 276:9182-8. [PMID: 11113142 DOI: 10.1074/jbc.m009414200] [Citation(s) in RCA: 132] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
A number of studies have demonstrated that cholera toxin (CT) is found in detergent-insoluble, cholesterol-enriched domains (rafts) in various cells, including neurons. We now demonstrate that even though CT is associated with these domains at the cell surface of cultured hippocampal neurons, it is internalized via a raft-independent mechanism, at both early and late stages of neuronal development. CT transport to the Golgi apparatus, and its subsequent degradation, is inhibited by hypertonic medium (sucrose), and by chlorpromazine; the former blocks clathrin recruitment, and the latter causes aberrant endosomal accumulation of clathrin. Moreover, both internalization of the transferrin receptor (Tf-R), which occurs via a clathrin-dependent mechanism, and CT internalization, are inhibited to a similar extent by sucrose. In contrast, the cholesterol-binding agents filipin and methyl-beta-cyclodextrin have no effect on the rate of CT or Tf-R internalization. Finally, once internalized, CT becomes more detergent-soluble, and chlorpromazine treatment renders internalized CT completely detergent-soluble. We propose two models to explain how, despite being detergent-insoluble at the cell surface, CT is nevertheless internalized via a raft-independent mechanism in hippocampal neurons.
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Affiliation(s)
- H Shogomori
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot 76100, Israel
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73
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Kumanogoh H, Miyata S, Sokawa Y, Maekawa S. Biochemical and morphological analysis on the localization of Rac1 in neurons. Neurosci Res 2001; 39:189-96. [PMID: 11223464 DOI: 10.1016/s0168-0102(00)00211-x] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The acquisition of cell type-specific morphologies is a central feature of neuronal differentiation. Many extra- and intracellular signals are known to cause the morphological changes of neuronal cells through the reconstruction of the microfilaments underneath the cell membrane. The membrane microdomain called "raft" has been paid much attention, for this domain contains many signal-transducing molecules including trimeric G proteins and cytoskeletal proteins. The raft domain is recovered in a low-density fraction after the treatment of the membrane with the non-ionic detergent such as Triton X-100 and the enrichment of cholesterol and sphingolipids is ascribed to be responsible for the detergent insolubility. In contrast to the well-known localization of trimeric G proteins in raft, the localization of small G proteins in the raft is poorly characterized. Since Rho family small G proteins (Rho, Rac, and Cdc42) regulate the microfilament system, we studied the localization of Rho family small G proteins in the raft of rat brain with western blotting. Specific localization of Rac1 was detected in the raft from 10-day-old and 8-week-old rat whole brain, and also in the raft prepared from the growth cone and synaptic plasma membrane fractions. Rho and Cdc42 were, in contrast, recovered in the Triton soluble fraction. Double immunostaining of cultured hippocampal neurons with antibodies to Rac1 and MAP-2, or Rac1 and tau, showed punctate distribution of Rac1 in axons as well as in dendrites.
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Affiliation(s)
- H Kumanogoh
- Department of Biotechnology, Faculty of Textile Science, Kyoto Institute of Technology, 606-8585, Kyoto, Japan
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74
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Kasahara K, Watanabe K, Takeuchi K, Kaneko H, Oohira A, Yamamoto T, Sanai Y. Involvement of gangliosides in glycosylphosphatidylinositol-anchored neuronal cell adhesion molecule TAG-1 signaling in lipid rafts. J Biol Chem 2000; 275:34701-9. [PMID: 10944523 DOI: 10.1074/jbc.m003163200] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The association of ganglioside GD3 with TAG-1, a glycosylphosphatidylinositol-anchored neuronal cell adhesion molecule, was examined by coimmunoprecipitation experiments. Previously, we have shown that the anti-ganglioside GD3 antibody (R24) immunoprecipitated the Src family kinase Lyn from the rat cerebellum, and R24 treatment of primary cerebellar cultures induced Lyn activation and rapid tyrosine phosphorylation of an 80-kDa protein (p80). We now report that R24 coimmunoprecipitates a 135-kDa protein (p135) from primary cerebellar cultures. Treatment with phosphatidylinositol-specific phospholipase C revealed that p135 was glycosylphosphatidylinositol-anchored to the membrane. It was identified as TAG-1 by sequential immunoprecipitation with an anti-TAG-1 antibody. Antibody-mediated cross-linking of TAG-1 induced Lyn activation and rapid tyrosine phosphorylation of p80. Selective inhibitor for Src family kinases reduced the tyrosine phosphorylation of p80. Sucrose density gradient analysis revealed that the TAG-1 and tyrosine-phosphorylated p80 in cerebellar cultures were present in the lipid raft fraction. These data show that TAG-1 transduces signals via Lyn to p80 in the lipid rafts of the cerebellum. Furthermore, degradation of cell-surface glycosphingolipids by endoglycoceramidase induced an alteration of TAG-1 distribution on an OptiPrep gradient and reduced the TAG-1-mediated Lyn activation and tyrosine phosphorylation of p80. These observations suggest that glycosphingolipids are involved in TAG-1-mediated signaling in lipid rafts.
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Affiliation(s)
- K Kasahara
- Department of Biochemical Cell Research, The Tokyo Metropolitan Institute of Medical Science, Tokyo Metropolitan Organization for Medical Research, Honkomagome, Bunkyo-ku, Tokyo 113-8613, Japan.
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75
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Polozova A, Litman BJ. Cholesterol dependent recruitment of di22:6-PC by a G protein-coupled receptor into lateral domains. Biophys J 2000; 79:2632-43. [PMID: 11053136 PMCID: PMC1301144 DOI: 10.1016/s0006-3495(00)76502-7] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Bovine rhodopsin was reconstituted into mixtures of didocosahexaenoylphosphatidylcholine (di22:6-PC), dipalmitoylphosphatidylcholine (di16:0-PC), sn-1-palmitoyl-sn-2-docosahexaenoylphosphatidylcholine (16:0, 22:6-PC) and cholesterol. Rhodopsin denaturation was examined by using high-sensitivity differential scanning calorimetry. The unfolding temperature was increased at lower levels of lipid unsaturation, but the highest temperature was detected for native disk membranes: di22:6-PC < 16:0,22:6-PC < di16:0,18:1-PC < native disks. The incorporation of 30 mol% of cholesterol resulted in 2-4 degrees C increase of denaturation temperature in all reconstituted systems examined. From the analysis of van't Hoff's and calorimetric enthalpies, it was concluded that the presence of cholesterol in di22:6-PC-containing bilayers induces a level of cooperativity in rhodopsin unfolding. Fluorescence resonance energy transfer (FRET), using lipids labeled at the headgroup with pyrene (Py) as donors and rhodopsin retinal group as acceptor of fluorescence, was used to study rhodopsin association with lipids. Higher FRET efficiencies detected for di22:6-PE-Py, compared to di16:0-PE-Py, in mixed di22:6-PC-di16:0-PC-cholesterol bilayers, indicate preferential segregation of rhodopsin with polyunsaturated lipids. The effective range of the rhodopsin-lipid interactions facilitating cluster formation exceeds two adjacent lipid layers. In similar mixed bilayers containing no cholesterol, cluster formation was absent at temperatures above lipid phase transition, indicating a crucial role of cholesterol in microdomain formation.
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Affiliation(s)
- A Polozova
- Laboratory of Membrane Biochemistry and Biophysics, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Rockville, Maryland 20852, USA
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76
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Hedberg KM, Dellheden B, Wikstrand CJ, Fredman P. Monoclonal anti-GD3 antibodies selectively inhibit the proliferation of human malignant glioma cells in vitro. Glycoconj J 2000; 17:717-26. [PMID: 11425192 DOI: 10.1023/a:1011026823362] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The frequently occurring alteration of ganglioside expression in tumor cells has been implicated to play a role in the uncontrolled growth of these cells; antibodies to such gangliosides might affect tumor cell growth. We have studied the effect of IgM monoclonal antibodies to two glioma-associated gangliosides, GD3 and GM2, on cell proliferation of four human glioma cell lines and one renal tumor cell line. Of the two anti-ganglioside antibodies tested, only the anti-GD3 antibody resulted in a significant (p<0.005) inhibition of cell proliferation as measured by thymidine incorporation and Brd-U labeling, after 24h incubation. The effect was not dependent on any serum factor and no increased cell death was observed. All cell lines contained higher or similar amounts of GM2 than GD3, and both antigens were shown to be expressed on the cell surface and accessible to antibodies. The selective effect of anti-GD3 antibodies as contrasted to the inactivity of anti-GM2 antibodies suggests a possible role for ganglioside GD3 in tumor cell proliferation.
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Affiliation(s)
- K M Hedberg
- Institute of Clinical Neuroscience, Section of Experimental Neuroscience, Göteborg University, Sahlgrenska University Hospital/Mölndal, Sweden
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77
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Gómez JL, García-Ayllón MS, Campoy FJ, Vidal CJ. Muscular dystrophy alters the processing of light acetylcholinesterase but not butyrylcholinesterase forms in liver of Lama2(dy) mice. J Neurosci Res 2000; 62:134-45. [PMID: 11002295 DOI: 10.1002/1097-4547(20001001)62:1<134::aid-jnr14>3.0.co;2-t] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
In order to know whether the histopathological changes of liver, which accompany muscular dystrophy, affect the synthesis of cholinesterases, the distribution and glycosylation of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) forms in normal (NL) and dystrophic Lama2(dy) mouse liver (DL) were investigated. About half of liver AChE, and 25% of BuChE were released with a saline buffer (fraction S(1)), and the rest with a saline-Brij 96 buffer (S(2)). Abundant light (G(2)(A) and G(1)(A)) AChE (87%) and BuChE (93%) forms, and a few G(4)(H) and G(4)(A) ChE species were identified in liver. The dystrophic syndrome had no effect on solubilization or composition of ChE forms. Most of the light AChE and BuChE species (>95%) were bound by octyl-Sepharose, while most light AChE forms (80%), but not BuChE isoforms (15%), were retained in phenyl-agarose. About half of the AChE dimers lost their amphiphilic anchor with phosphatidylinositol-specific phospholipase C (PIPLC), and the fraction of PIPLC-resistant species increased in DL. AChE T and R transcripts were detected by reverse transcriptase-polymerase chain reaction (RT-PCR) of liver RNA. ChE components of liver, erythrocyte, and plasma were distinguished by their amphiphilic properties and interaction with lectins. The dystrophic syndrome increased the liver content of the light AChE forms with Lens culinaris agglutinin (LCA) reactivity. The abundance of ChE tetramers in plasma and their small amount in liver suggest that after their assembly in liver they are rapidly secreted, while the light species remain associated to hepatic membranes.
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Affiliation(s)
- J L Gómez
- Departamento de Bioquímica y Biología Molecular-A, Universidad de Murcia, Espinardo, Murcia, Spain
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78
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Henderson LP, Lin L, Prasad A, Paul CA, Chang TY, Maue RA. Embryonic striatal neurons from niemann-pick type C mice exhibit defects in cholesterol metabolism and neurotrophin responsiveness. J Biol Chem 2000; 275:20179-87. [PMID: 10770933 DOI: 10.1074/jbc.m001793200] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Niemann-Pick type C (NP-C) disease is a progressive and fatal neuropathological disorder previously characterized by abnormal cholesterol metabolism in peripheral tissues. Although a defective gene has been identified in both humans and the npc(nih) mouse model of NP-C disease, how this leads to abnormal neuronal function is unclear. Here we show that whereas embryonic striatal neurons from npc(nih) mice can take up low density lipoprotein-derived cholesterol, its subsequent hydrolysis and esterification are significantly reduced. Given the importance of cholesterol to a variety of signal transduction mechanisms, we assessed the effect of this abnormality on the ability of these neurons to respond to brain-derived neurotrophic factor (BDNF). In contrast to its effects on wild type neurons, BDNF failed to induce autophosphorylation of the TrkB receptor and to increase neurite outgrowth in npc(nih) neurons, despite expression of TrkB on the cell surface. The results suggest that abnormal cholesterol metabolism occurs in neurons in the brain during NP-C disease, even at embryonic stages of development prior to the onset of phenotypic symptoms. Moreover, this defect is associated with a lack of TrkB function and BDNF responsiveness, which may contribute to the loss of neuronal function observed in NP-C disease.
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Affiliation(s)
- L P Henderson
- Departments of Physiology and Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755, USA
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79
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Molander M, Berthold CH, Persson H, Fredman P. Immunostaining of ganglioside GD1b, GD3 and GM1 in rat cerebellum: cellular layer and cell type specific associations. J Neurosci Res 2000; 60:531-42. [PMID: 10797556 DOI: 10.1002/(sici)1097-4547(20000515)60:4<531::aid-jnr12>3.0.co;2-6] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
We have studied the cellular distribution of gangliosides GD1b, GD3 and GM1 in rat cerebellum by immunostaining, using monoclonal antibodies and confocal microscopy. Antibodies against astroglial, neuronal and synaptic vesicle associated molecules were used for colocalization analyses. In the gray matter, the anti-GD1b antibody stained thin strands in the molecular layer (ML), interpreted as Bergman glia fibers based on colocalized staining with anti-glial fibrillary acidic protein (GFAP). The neuropil in the granule (GL) and Purkinje (PL) cell layers was also anti-GD1b positive. The anti-GD3 antibody stained the ML, the neuropil in the GL and PL and also the granule and Purkinje cell bodies, appearing intracytoplasmically and vesicle associated. Anti-GD1b and anti-GD3 staining in the GL glomeruli were colocalized with anti-synaptophysin staining. The anti-GM1 antibody stained cell bodies in the ML but they could not be characterized in colocalization experiments. The GL and PL were not stained with the anti-GM1 antibody. In the white matter, different staining patterns were seen for the gangliosides, the anti-GM1 staining being the most intense. This study shows cellular layer and cell type specific associations of the investigated gangliosides and localization of GD1b and GD3 at synaptic sites, warranting further studies on their role in synaptic mechanisms.
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Affiliation(s)
- M Molander
- Institute of Clinical Neuroscience, Experimental Neuroscience Section, Göteborg University, Sweden.
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80
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Palestini P, Pitto M, Tedeschi G, Ferraretto A, Parenti M, Brunner J, Masserini M. Tubulin anchoring to glycolipid-enriched, detergent-resistant domains of the neuronal plasma membrane. J Biol Chem 2000; 275:9978-85. [PMID: 10744673 DOI: 10.1074/jbc.275.14.9978] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
After incubation of intact living cultured rat cerebellar granule cells at 37 degrees C with a new GM1 ganglioside analog, carrying a diazirine group and labeled with (125)I in the ceramide moiety, followed by photoactivation, a relatively small number of radiolabeled proteins were detected in a membrane-enriched fraction. A protein of about 55 kDa with a pI of about 5 carried a large portion of the radioactivity even if incubation and cross-linking were performed at 4 degrees C and in the presence of inhibitors of endocytosis, suggesting that it is cross-linked at the plasma membrane. Immunoprecipitation and Western blotting experiments showed the positivity of this protein for tubulin. Trypsin treatment of intact cells ruled out the involvement of a plasma membrane surface tubulin. Release of radioactivity from cross-linked tubulin after KOH treatment (but not hydroxylamine treatment) suggested that the photoactivated ganglioside reacts with an ester-linked fatty acid anchor of tubulin. Low buoyancy, detergent-resistant membrane fractions, isolated from cells after incubation with the GM1 analogue and photoactivation, proved their enrichment in endogenous and radioactive GM1 ganglioside, sphingomyelin, cholesterol, signal transduction proteins, and tubulin. It is noteworthy that radioactive tubulin was also detected in this fraction, indicating the presence of tubulin molecules carrying a fatty acid anchor in detergent-resistant, ganglioside-enriched domains of the plasma membrane. Parallel experiments carried out with a phosphatidylcholine analogue, also carrying a diazirine group and labeled with (125)I in the fatty acid moiety, showed the specificity of tubulin interaction with GM1. Taken together, these results indicate that some tubulin molecules are associated with a lipid anchor to detergent-resistant glycolipid-enriched domains of the plasma membrane. This novel feature of membrane domains can provide a key for a better understanding of their biological role.
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Affiliation(s)
- P Palestini
- Department of Experimental, Environmental Medicine and Biotechnologies, Medical School, University of Milano-Bicocca, Hospital S. Gerardo, 20052 Monza, Italy.
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81
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Martens JR, Navarro-Polanco R, Coppock EA, Nishiyama A, Parshley L, Grobaski TD, Tamkun MM. Differential targeting of Shaker-like potassium channels to lipid rafts. J Biol Chem 2000; 275:7443-6. [PMID: 10713042 DOI: 10.1074/jbc.275.11.7443] [Citation(s) in RCA: 204] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ion channel targeting within neuronal and muscle membranes is an important determinant of electrical excitability. Recent evidence suggests that there exists within the membrane specialized microdomains commonly referred to as lipid rafts. These domains are enriched in cholesterol and sphingolipids and concentrate a number of signal transduction proteins such as nitric-oxide synthase, ligand-gated receptors, and multiple protein kinases. Here, we demonstrate that the voltage-gated K(+) channel Kv2.1, but not Kv4.2, targets to lipid rafts in both heterologous expression systems and rat brain. The Kv2.1 association with lipid rafts does not appear to involve caveolin. Depletion of cellular cholesterol alters the buoyancy of the Kv2.1 associated rafts and shifts the midpoint of Kv2.1 inactivation by nearly 40 mV without affecting peak current density or channel activation. The differential targeting of Kv channels to lipid rafts represents a novel mechanism both for the subcellular sorting of K(+) channels to regions of the membrane rich in signaling complexes and for modulating channel properties via alterations in lipid content.
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Affiliation(s)
- J R Martens
- Departments of Physiology and Biochemistry and Molecular Biology, Colorado State University, Ft. Collins, Colorado 80523, USA
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82
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Raudino A, Cantù L, Corti M, Del Favero E. Bistable molecular self-assembling. Curr Opin Colloid Interface Sci 2000. [DOI: 10.1016/s1359-0294(00)00029-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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83
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Pitto M, Brunner J, Ferraretto A, Ravasi D, Palestini P, Masserini M. Use of a photoactivable GM1 ganglioside analogue to assess lipid distribution in caveolae bilayer. Glycoconj J 2000; 17:215-22. [PMID: 11201793 DOI: 10.1023/a:1026593307882] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
A new photoactivable, radioactive derivative of ganglioside GM1 has been utilized to assess lipid distribution in the caveolae bilayer, taking advantage of the ability of the glycolipid, endogenous or exogenously added, to concentrate within this membrane compartment and to crosslink neighboring molecules upon illumination. After insertion into A431 plasma membrane and photoactivation, a membrane-enriched and a detergent-resistant fraction, enriched in gangliosides, sphingomyelin and cholesterol, were isolated. While a few radioactive proteins were detected in the membrane-enriched fraction, only radioactive caveolin was detected in the detergent-resistant fraction, indicating at the same time the enrichment of this fraction in caveolae and the presence of ganglioside within this compartment. Among lipids, crosslinked phosphatidylcholine, sphingomyelin and cholesterol were detected in the membrane-enriched fraction, while only crosslinked sphingomyelin was detected in the detergent-resistant fraction. These results suggest the enrichment in sphingomyelin - along with ganglioside - within the outer leaflet, and the preferential localization of cholesterol within the endoplasmic leaflet, of the caveolae bilayer.
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Affiliation(s)
- M Pitto
- Department of Experimental and Environmental Medicine, University of Milano-Bicocca, Monza, Italy.
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84
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Prinetti A, Marano N, Prioni S, Chigorno V, Mauri L, Casellato R, Tettamanti G, Sonnino S. Association of Src-family protein tyrosine kinases with sphingolipids in rat cerebellar granule cells differentiated in culture. Glycoconj J 2000; 17:223-32. [PMID: 11201794 DOI: 10.1023/a:1026545424720] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Src family kinases play a relevant role in the development and differentiation of neuronal cells. They are abundant in sphingolipid-enriched membrane domains of many cell types, and these domains are hypothesized to function in bringing together molecules important to signal transduction. We studied the association of Src family tyrosine kinases and their negative regulatory kinase, Csk, with sphingolipids in sphingolipid-enriched domains of rat cerebellar granule cells differentiated in culture. We find that c-Src, Lyn and Csk are enriched in the sphingolipid-enriched fraction prepared from these cells. Coimmunoprecipitation experiments show that these and sphingolipids are part of the same domain. Cross-linking experiments with a photoactivable, radioactive GD1b derivative show that c-Src and Lyn, which are anchored to the membrane via a myristoyl chain, associate directly with GD1b. Csk, which is not inserted in the hydrophobic core of the membrane, is not photolabeled by this ganglioside. These results suggest that lipid-lipid, lipid-protein, and protein-protein interactions cooperate to maintain domain structure. We hypothesize that such interactions might play a role in the process of neuronal differentiation.
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Affiliation(s)
- A Prinetti
- Department of Medical Chemistry and Biochemistry - LITA - Segrate, The Medical School, University of Milan, Milano, Italy
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85
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Kasahara K, Sanai Y. Functional roles of glycosphingolipids in signal transduction via lipid rafts. Glycoconj J 2000; 17:153-62. [PMID: 11201786 DOI: 10.1023/a:1026576804247] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The formation of glycosphingolipid (GSL)-cholesterol microdomains in cell membranes has been proposed to function as platforms for the attachment of lipid-modified proteins, such as glycosylphosphatidylinositol (GPI)-anchored proteins and src-family tyrosine kinases. The microdomains are postulated to be involved in GPI-anchored protein signaling via src-family kinase. Here, the functional roles of GSLs in signal transduction mediated by the microdomains are discussed. Antibodies against GSLs co-precipitate GPI-anchored proteins, src-family kinases and several components of the microdomains. Antibody-mediated crosslinking of GSLs, as well as that of GPI-anchored proteins, induces a rapid activation of src-family kinases and a transient increase in the tyrosine phosphorylation of several substrates. Enzymatic degradation of GSLs reduces the activation of src-family kinase and tyrosine phosphorylation by antibody-mediated crosslinking of GPI-anchored protein. Furthermore, GSLs can also modulate signal transduction of immunoreceptors and growth factor receptors in the microdomains. Thus, GSLs have important roles in signal transduction mediated by the microdomains.
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Affiliation(s)
- K Kasahara
- The Tokyo Metropolitan Institute of Medical Science, Tokyo Metropolitan Organization for Medical Research, Japan.
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86
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Davy A, Feuerstein C, Robbins SM. Signaling within a caveolae-like membrane microdomain in human neuroblastoma cells in response to fibroblast growth factor. J Neurochem 2000; 74:676-83. [PMID: 10646519 DOI: 10.1046/j.1471-4159.2000.740676.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
It is now clear that the plasma membrane is not homogeneous but contains specific subcompartments characterized by their unique lipid and protein composition. Based on their enrichment in various signaling molecules, these microcompartments are now recognized to be sites of localized signal transduction for several extracellular stimuli. At least two different types of microdomains can be identified, largely based on the presence or absence of the caveolin proteins. The generic name of caveolae-like domains is commonly used to refer to both domains indistinguishably. Although caveolin proteins were long thought to be absent from the brain, we have shown that the human neuroblastoma cell line LAN-1 expresses both caveolin-1 and caveolin-2. Basic fibroblast growth factor (FGF)-2 induced a specific signaling response within the caveolae-like domain of LAN-1 cells, characterized by the tyrosine phosphorylation of a 75-80-kDa protein. This protein present in the caveolae-like domains has properties suggesting that it is a member of the SNT family of adapter proteins. The signaling event originating in the caveolae-like domains in response to FGF-2 appeared to require the activation of at least Fyn and Lyn, two members of the Src family of tyrosine kinases. This work suggests that compartmentalized signaling within caveolae-like domains may create a level of specificity for certain growth factors such as FGF.
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Affiliation(s)
- A Davy
- Department of Oncology, University of Calgary, Alberta, Canada
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87
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Abstract
Roles proposed for nitric oxide (NO) in CNS pathophysiology are increasingly diverse and range from intercellular signaling, through necrotic killing of cells and invading pathogens, to the involvement of NO in apoptosis and tissue remodeling. In vitro evidence and observations from experimental animal models of a variety of human neuropathologies, including stroke, indicate that glial cells can produce NO. Regulation of at least one of the NO synthase genes (NOS-2) in glia has been well described; however, apart from hints emerging out of co-culture studies and extrapolation based upon the reactivity of NO, we are a long way from identifying functions for glial-derived NO in the CNS. Although the assumption is that NO is very often cytotoxic, it is evident that NO production does not always equate with tissue damage, and that both the cellular source of NO and the timing of NO production are important factors in terms of its effects. With the development of strategies to transfer or manipulate expression of the NOS genes in specific cells in situ, the ability to deliver NO into the CNS via long-lived chemical donors, and the emergence of more selective NOS inhibitors, an appreciation of the significance of glial-derived NO will change.
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Affiliation(s)
- S Murphy
- Department of Pharmacology and the Neuroscience Program, University of Iowa College of Medicine, Iowa City, USA.
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