51
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Bañó MC, Jackson CS, Magee AI. Pseudo-enzymatic S-acylation of a myristoylated yes protein tyrosine kinase peptide in vitro may reflect non-enzymatic S-acylation in vivo. Biochem J 1998; 330 ( Pt 2):723-31. [PMID: 9480882 PMCID: PMC1219197 DOI: 10.1042/bj3300723] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Covalent attachment of a variety of lipid groups to proteins is now recognized as a major group of post-translational modifications. S-acylation of proteins at cysteine residues is the only modification considered dynamic and thus has the potential for regulating protein function and/or localization. The activities that catalyse reversible S-acylation have not been well characterized and it is not clear whether both the acylation and the deacylation steps are regulated, since in principle it would be sufficient to control only one of them. Both apparently enzymatic and non-enzymatic S-acylation of proteins have previously been reported. Here we show that a synthetic myristoylated c-Yes protein tyrosine kinase undecapeptide undergoes spontaneous S-acylation in vitro when using a long chain acyl-CoA as acyl donor in the absence of any protein. The S-acylation was dependent on myristoylation of the substrate, the length of the incubation period, temperature and substrate concentration. When COS cell fractions were added to the S-acylation reaction no additional peptide:S-acyltransferase activity was detected. These results are consistent with the possibility that membrane-associated proteins may undergo S-acylation in vivo by non-enzymatic transfer of acyl groups from acyl-CoA. In this case, the S-acylation-deacylation process could be controlled by a regulated depalmitoylation mechanism.
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Affiliation(s)
- M C Bañó
- Division of Membrane Biology, National Institute for Medical Research, The Ridgeway, Mill Hill, London NW71AA, U.K
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52
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Abstract
Multiple signaling pathways are thought to control the selective expression of genes over the course of neuronal differentiation. One approach to elucidating these pathways is to identify specific cis-acting elements that serve as the final targets for these signaling pathways in neural-specific genes. We now identify a novel repressive element from the growth-associated protein 43 (GAP-43) gene that can contribute to neuron-specific gene expression by inhibiting transcription in a wide range of non-neuronal cell types. This repressive element is located downstream of the GAP-43 TATA box and is highly position-dependent. When transferred to viral promoters this element preferentially inhibits transcription in non-neuronal cells. Electrophoretic mobility shift assays show that the repressive element comprises at least two protein recognition sites. One of these is a novel sequence motif that we designate the SNOG element, because it occurs downstream of the TATA boxes of the synaptosomal-associated protein of 25 kDa and neuronal nitric oxide synthase genes, as well as the GAP-43 gene. The GAP-43 repressive element is distinct in sequence and position dependence from the repressor element 1/neuron-restrictive silencer element previously described in other neural genes and therefore is a likely target for a distinct set of signaling pathways involved in the control of neuronal differentiation.
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53
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Weber JR, Skene JH. Identification of a novel repressive element that contributes to neuron-specific gene expression. J Neurosci 1997; 17:7583-93. [PMID: 9315881 PMCID: PMC6793915] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/1997] [Revised: 07/21/1997] [Accepted: 07/24/1997] [Indexed: 02/05/2023] Open
Abstract
Multiple signaling pathways are thought to control the selective expression of genes over the course of neuronal differentiation. One approach to elucidating these pathways is to identify specific cis-acting elements that serve as the final targets for these signaling pathways in neural-specific genes. We now identify a novel repressive element from the growth-associated protein 43 (GAP-43) gene that can contribute to neuron-specific gene expression by inhibiting transcription in a wide range of non-neuronal cell types. This repressive element is located downstream of the GAP-43 TATA box and is highly position-dependent. When transferred to viral promoters this element preferentially inhibits transcription in non-neuronal cells. Electrophoretic mobility shift assays show that the repressive element comprises at least two protein recognition sites. One of these is a novel sequence motif that we designate the SNOG element, because it occurs downstream of the TATA boxes of the synaptosomal-associated protein of 25 kDa and neuronal nitric oxide synthase genes, as well as the GAP-43 gene. The GAP-43 repressive element is distinct in sequence and position dependence from the repressor element 1/neuron-restrictive silencer element previously described in other neural genes and therefore is a likely target for a distinct set of signaling pathways involved in the control of neuronal differentiation.
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Affiliation(s)
- J R Weber
- Department of Neurobiology, Duke University Medical Center, Durham, North Carolina 27710, USA
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54
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Baker LP, Storm DR. Dynamic palmitoylation of neuromodulin (GAP-43) in cultured rat cerebellar neurons and mouse N1E-115 cells. Neurosci Lett 1997; 234:156-60. [PMID: 9364521 DOI: 10.1016/s0304-3940(97)00667-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
We conducted pulse-chase and metabolic labeling experiments to determine directly whether palmitoylation of neuromodulin in neurons is dynamic, and if acylation is regulated. The rates of turnover of neuromodulin protein and associated palmitoyl groups were quantified using cultured cerebellar granule neurons and the neuronal cell line N1E-115. The half-life of [3H]palmitate bound to neuromodulin was approximately 5 h, whereas the half-life of the [35S]methionine-labeled neuromodulin was greater than 50 h. Metabolic and pulse-chase labeling experiments were carried out in the presence of various activators of cellular signaling pathways. Our data indicate that dynamic acylation and deacylation of neuromodulin in neurons are constitutive and are not regulated by G protein activation or other signals that control growth cone dynamics.
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Affiliation(s)
- L P Baker
- Department of Pharmacology, University of Washington, Seattle 98195-7280, USA
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55
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Buckley BJ, Whorton AR. Tunicamycin increases intracellular calcium levels in bovine aortic endothelial cells. THE AMERICAN JOURNAL OF PHYSIOLOGY 1997; 273:C1298-305. [PMID: 9357774 DOI: 10.1152/ajpcell.1997.273.4.c1298] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Tunicamycin is a nucleoside antibiotic that inhibits protein glycosylation and palmitoylation. The therapeutic use of tunicamycin is limited in animals because of its toxic effects, particularly in cerebral vasculature. Tunicamycin decreases palmitoylation of the endothelial isoform of nitric oxide synthase, stimulates nitric oxide synthesis, and increases the concentration of intracellular calcium ([Ca2+]i) in bovine aortic endothelial cells (B. J. Buckley and A. R. Whorton. FASEB J. 11: A110, 1997). In the present study, we investigated the mechanism by which tunicamycin alters [Ca2+]i using the Ca2+-sensitive dye fura 2. We found that tunicamycin increased [Ca2+]i without increasing levels of inositol phosphates. When cells were incubated in the absence of extracellular Ca2+, [Ca2+]i rapidly rose in response to tunicamycin, although a full response was not achieved. The pool of intracellular Ca2+ mobilized by tunicamycin overlapped with that mobilized by thapsigargin. Extracellular nickel blocked a full response to tunicamycin when cells were incubated in the presence of extracellular Ca2+. The effects of tunicamycin on [Ca2+]i were partially reversed by washing out the drug, and the remainder of the response was inhibited by removing extracellular Ca2+. These results indicate that tunicamycin mobilizes Ca2+ from intracellular stores in a manner independent of phospholipase C activation and increases the influx of Ca2+ across the plasma membrane.
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Affiliation(s)
- B J Buckley
- Department of Pharmacology, Duke University Medical Center, Durham, North Carolina 27710, USA
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56
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Dan N, Middleton RB, Lehrman MA. Hamster UDP-N-acetylglucosamine:dolichol-P N-acetylglucosamine-1-P transferase has multiple transmembrane spans and a critical cytosolic loop. J Biol Chem 1996; 271:30717-24. [PMID: 8940049 DOI: 10.1074/jbc.271.48.30717] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
UDP-GlcNAc:dolichol-P GlcNAc-1-P transferase (GPT) is an endoplasmic reticulum (ER) enzyme responsible for synthesis of GlcNAc-P-P-dolichol, the committed step of dolichol-P-P-oligosaccharide synthesis. The sequence of hamster GPT predicted multiple transmembrane segments (Zhu, X., and Lehrman, M. A. (1990) J. Biol. Chem. 265, 14250-14255). GPT has also been predicted to act on the cytosolic face of the ER membrane, based on topological studies of its substrates and products. In this report we test these predictions by: (i) immunofluorescence microscopy with antibodies specific for native GPT sequences or epitope tags inserted into GPT, after selective permeabilization of the plasma membrane with digitonin; (ii) insertion of Factor Xa cleavage sites; (iii) in vitro translation of GPT; and (iv) site-directed mutagenesis. The loops between the 1st and 2nd and between the 9th and 10th predicted transmembrane spans of GPT were found to be cytosolic. In contrast, the loop between the 6th and 7th transmembrane spans, as well as the carboxyl terminus, were lumenal. Thus, hamster GPT must cross the ER membrane at least three times, consistent with previous computer-assisted predictions. There was no apparent N-glycosylation or signal sequence cleavage detected by in vitro translation. The cytosolic loop between the 9th and 10th transmembrane spans is the largest hydrophilic segment in GPT and, as judged by site-directed mutagenesis, has a number of conserved residues essential for activity. Hence, these results directly support the hypothesis that dolichol-P-P-oligosaccharide assembly is initiated in the cytosol and that a downstream intermediate must translocate to the lumenal face of the ER membrane.
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Affiliation(s)
- N Dan
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas 75235-9041, USA.
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57
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Resh MD. Regulation of cellular signalling by fatty acid acylation and prenylation of signal transduction proteins. Cell Signal 1996; 8:403-12. [PMID: 8958442 DOI: 10.1016/s0898-6568(96)00088-5] [Citation(s) in RCA: 184] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Covalent modification by fatty acylation and prenylation occurs on a wide variety of cellular signalling proteins. The enzymes that catalyze attachment of these lipophilic moieties to proteins have recently been identified and characterized. Each lipophilic group confers unique properties to the modified protein, resulting in alterations in protein/protein interactions, membrane binding and targeting, and intracellular signalling. The biochemistry and cell biology of protein myristoylation, farnesylation and geranylgeranylation is reviewed here, with emphasis on the Src family of tyrosine kinases, Ras proteins and G protein coupled signalling systems.
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Affiliation(s)
- M D Resh
- Cell Biology and Genetics Program, Sloan-Kettering Institute, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA.
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58
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Schroeder H, Leventis R, Shahinian S, Walton PA, Silvius JR. Lipid-modified, cysteinyl-containing peptides of diverse structures are efficiently S-acylated at the plasma membrane of mammalian cells. J Cell Biol 1996; 134:647-60. [PMID: 8707845 PMCID: PMC2120939 DOI: 10.1083/jcb.134.3.647] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
A variety of cysteine-containing, lipid-modified peptides are found to be S-acylated by cultured mammalian cells. The acylation reaction is highly specific for cysteinyl over serinyl residues and for lipid-modified peptides over hydrophilic peptides. The S-acylation process appears by various criteria to be enzymatic and resembles the S-acylation of plasma membrane-associated proteins in various characteristics, including inhibition by tunicamycin. The substrate range of the S-acylation reaction encompasses, but is not limited to, lipopeptides incorporating the motifs myristoylGC- and -CXC(farnesyl)-OCH3, which are reversibly S-acylated in various intracellular proteins. Mass-spectrometric analysis indicates that palmitoyl residues constitute the predominant but not the only type of S-acyl group coupled to a lipopeptide carrying the myristoylGC- motif, with smaller amounts of S-stearoyl and S-oleoyl substituents also detectable. Fluorescence microscopy using NBD-labeled cysteinyl lipopeptides reveals that the products of lipopeptide S-acylation, which cannot diffuse between membranes, are in almost all cases localized preferentially to the plasma membrane. This preferential localization is found even at reduced temperatures where vesicular transport from the Golgi complex to the plasma membrane is suppressed, strongly suggesting that the plasma membrane itself is the preferred site of S-acylation of these species. Uniquely among the lipopeptides studied, species incorporating an unphysiological N-myristoylcysteinyl- motif also show substantial formation of S-acylated products in a second, intracellular compartment identified as the Golgi complex by its labeling with a fluorescent ceramide. Our results suggest that distinct S-acyltransferases exist in the Golgi complex and plasma membrane compartments and that S-acylation of motifs such as myristoylGC- occurs specifically at the plasma membrane, affording efficient targeting of cellular proteins bearing such motifs to this membrane compartment.
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Affiliation(s)
- H Schroeder
- Department of Biochemistry, McGill University, Montréal, Québec, Canada
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59
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Morello JP, Bouvier M. Palmitoylation: a post-translational modification that regulates signalling from G-protein coupled receptors. Biochem Cell Biol 1996; 74:449-57. [PMID: 8960351 DOI: 10.1139/o96-049] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Protein acylation is a post-translational modification that has seized much attention in the last few years. Depending on the nature of the fatty acid added, protein acylation can take the form of palmitoylation, myristoylation, or prenylation. Palmitoylation has been implicated in the modification of several different proteins and is particularly prevalent in G-protein coupled receptors and their cognate G-proteins, where it is thought to have an important regulatory function. Given that palmitoylation of these proteins is a dynamic phenomenon in which turnover rate is modulated by agonist activation, it is thought to be implicated in processes such as receptor phosphorylation and desensitization as well as in G-protein membrane translocation. A better understanding of the regulation of signal transduction mediated by G-protein coupled receptors will require the identification and characterization of those enzymes implicated in the palmitoylation and depalmitoylation process of this large class of receptors and their signalling allies.
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Affiliation(s)
- J P Morello
- Département de biochimie, Faculté de Médecine, Université de Montréal, QC, Canada
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60
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Gundersen CB, Umbach JA, Mastrogiacomo A. Cysteine-string proteins: a cycle of acylation and deacylation? Life Sci 1996; 58:2037-40. [PMID: 8637434 DOI: 10.1016/0024-3205(96)00195-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
We used tunicamycin, an inhibitor of protein fatty acylation, to examine the possibility that there is a cycle of acylation and deacylation of cysteine string proteins at nerve terminals. Using both physiological and immunoblot approaches, we obtained no evidence for a cycle of acylation and deacylation that affects these proteins. These data suggest that this lipid modification of cysteine string proteins is relatively more stable than that observed for other nerve ending proteins, like SNAP-25.
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Affiliation(s)
- C B Gundersen
- Department of Molecular and Medical Pharmacology, UCLA School of Medicine 90095, USA
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61
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Over-expression ofS. cerevisiae G1 cyclins restores the viability ofalg1 N-glycosylation mutants. Curr Genet 1996. [DOI: 10.1007/bf02221573] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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62
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Benton BK, Plump SD, Roos J, Lennarz WJ, Cross FR. Over-expression of S. cerevisiae G1 cyclins restores the viability of alg1 N-glycosylation mutants. Curr Genet 1996; 29:106-13. [PMID: 8821656] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
In budding yeast, one of three G1 cyclins is required for progression though START, when cells commit to a further round of cell division. We have identified mutations in ALG1 (ERC14), a gene required for N-glycosylation, which are inviable in a cln1 cln2 background but are rescued by over-expression of CLNs. CLN1 and CLN2 are much more efficient than CLN3 in rescuing the erc14-1 allele. The erc14-1 allele results in a significant N-glycosylation defect, and no rescue of this defect by CLN1 over-expression was detected. These data suggest that CLN over-expression could be allowing cells to live with lower levels of N-glycosylation, possibly by overcoming a checkpoint sensitive to N-glycosylation capacity. A plasmid suppressor of alg1, PSA1, encodes a 361 amino-acid protein with homology to NDP-hexose pyrophosphorylases, the enzymes that catalyze the formation of activated sugar nucleotides. PSA1 is an essential gene, and PSA1 transcription is nearly co-ordinately regulated with CLN2 transcription, peaking near START. Co-ordinate regulation of glycosylation, sugar nucleotide metabolism, and cell-cycle progression through G1 may be a feature that ensures adequate cell-wall precursors are present before bud emergence.
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Affiliation(s)
- B K Benton
- Rockefeller University, New York, NY 10021, USA
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63
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Jochen AL, Hays J, Mick G. Inhibitory effects of cerulenin on protein palmitoylation and insulin internalization in rat adipocytes. BIOCHIMICA ET BIOPHYSICA ACTA 1995; 1259:65-72. [PMID: 7492617 DOI: 10.1016/0005-2760(95)00147-5] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Protein acylation by long-chain fatty acids has been suggested as a necessary step in membrane trafficking. Because several insulin effects are dependent upon membrane trafficking, the cellular effects of the protein acylation inhibitor cerulenin were examined. Cerulenin blocked palmitoylation of selected rat adipocyte proteins including CD36, the dominant marker for palmitoylation in adipocytes. To measure cerulenin's effects on insulin internalization, rat adipocytes were incubated with 125I-insulin at 37 degrees C in the presence or absence of cerulenin. Surface-bound and intracellular insulin were discriminated by the sensitivity of the former to rapid dissociation by a pH 3 buffer at 4 degrees C. Insulin internalization was inhibited 85% by 0.3 mM cerulenin. Inhibition required preincubation with the agent, was irreversible, was not dependent upon protein synthesis, and was not the result of ATP depletion. Cerulenin was also found to inhibit insulin-stimulated glucose uptake and acetyl-CoA carboxylase activity. Cerulenin had no effect on basal glucose uptake and utilization or on the uptake and retention of fatty acids. In summary, protein acylation may be an important step in insulin-regulated cellular functions dependent upon membrane trafficking, such as insulin internalization.
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Affiliation(s)
- A L Jochen
- Department of Medicine, Zablocki Veterans Administration Medical Center, Medical College of Wisconsin, Milwaukee 53226, USA
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64
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Stewart HJ, Curtis R, Jessen KR, Mirsky R. TGF-beta s and cAMP regulate GAP-43 expression in Schwann cells and reveal the association of this protein with the trans-Golgi network. Eur J Neurosci 1995; 7:1761-72. [PMID: 7582129 DOI: 10.1111/j.1460-9568.1995.tb00696.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
We have shown previously that growth-associated protein 43 (GAP-43) is expressed by rat Schwann cells and is restricted to non-myelin-forming Schwann cells in vivo. Here we examined the regulation of GAP-43 using agents that are known to control Schwann cell differentiation in vitro. GAP-43 protein and mRNA levels are decreased by forskolin and other agents that elevate intracellular cAMP (and promote expression of the myelinating Schwann cell phenotype). We also found that expression of GAP-43 protein but not mRNA is down-regulated by transforming growth factor betas (TGF-beta s). Moreover, TGF-beta treatment of Schwann cells results in cell clumping, process retraction and disappearance of GAP-43 from the plasma membrane, revealing that GAP-43 is associated with the Golgi apparatus. This association was confirmed by partial overlap of GAP-43 with the trans-Golgi network marker (23c) and the disruption of the Golgi with brefeldin A or monensin leading to altered GAP-43 distribution. Golgi-associated GAP-43 appeared to have the same molecular weight as the plasma membrane-associated GAP-43. Thus these results show that GAP-43 expression in Schwann cells is subject to regulation by both extracellular and intracellular signalling molecules and that Schwann cell GAP-43 is often associated with the Golgi apparatus.
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Affiliation(s)
- H J Stewart
- Department of Anatomy and Developmental Biology, University College London, UK
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65
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Patterson SI, Skene JH. Inhibition of dynamic protein palmitoylation in intact cells with tunicamycin. Methods Enzymol 1995; 250:284-300. [PMID: 7651158 DOI: 10.1016/0076-6879(95)50079-0] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- S I Patterson
- Department of Neurobiology, Duke University Medical Center, Durham, North Carolina 27710, USA
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