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Abstract
Despite decades of research, cancer metastasis remains an incompletely understood process that is as complex as it is devastating. In recent years, there has been an increasing push to investigate the biomechanical aspects of tumorigenesis, complementing the research on genetic and biochemical changes. In contrast to the high genetic variability encountered in cancer cells, almost all metastatic cells are subject to the same physical constraints as they leave the primary tumor, invade surrounding tissues, transit through the circulatory system, and finally infiltrate new tissues. Advances in live cell imaging and other biophysical techniques, including measurements of subcellular mechanics, have yielded stunning new insights into the physics of cancer cells. While much of this research has been focused on the mechanics of the cytoskeleton and the cellular microenvironment, it is now emerging that the mechanical properties of the cell nucleus and its connection to the cytoskeleton may play a major role in cancer metastasis, as deformation of the large and stiff nucleus presents a substantial obstacle during the passage through the dense interstitial space and narrow capillaries. Here, we present an overview of the molecular components that govern the mechanical properties of the nucleus, and we discuss how changes in nuclear structure and composition observed in many cancers can modulate nuclear mechanics and promote metastatic processes. Improved insights into this interplay between nuclear mechanics and metastatic progression may have powerful implications in cancer diagnostics and therapy and may reveal novel therapeutic targets for pharmacological inhibition of cancer cell invasion.
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Affiliation(s)
- Celine Denais
- Department of Biomedical Engineering, Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY, 14853, USA,
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2
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Gilloteaux J, Kashouty R, Yono N. The perinuclear space of pancreatic acinar cells and the synthetic pathway of zymogen in Scorpaena scrofa L.: Ultrastructural aspects. Tissue Cell 2008; 40:7-20. [DOI: 10.1016/j.tice.2007.08.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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3
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N-terminal of L protein of vesicular stomatitis virus contains a new signal sequence. CHINESE SCIENCE BULLETIN-CHINESE 2003. [DOI: 10.1007/bf03184178] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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4
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Otto H, Dreger M, Bengtsson L, Hucho F. Identification of tyrosine-phosphorylated proteins associated with the nuclear envelope. EUROPEAN JOURNAL OF BIOCHEMISTRY 2001; 268:420-8. [PMID: 11168378 DOI: 10.1046/j.1432-1033.2001.01901.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The nuclear envelope separates the nucleoplasm from the rest of the cell. Throughout the cell cycle, its structural integrity is controlled by reversible protein phosphorylation. Whereas its phosphorylation-dependent disassembly during mitosis is well characterized, little is known about phosphorylation events at this structure during interphase. The few characterized examples cover protein phosphorylation at serine and threonine residues, but not tyrosine phosphorylation at the nuclear envelope. Here, we demonstrate that tyrosine phosphorylation and dephosphorylation occur at the nuclear envelope of intact Neuro2a mouse neuroblastoma cells. Tyrosine kinase and phosphatase activities remain associated with purified nuclear envelopes. A similar pattern of tyrosine-phosphorylated nuclear envelope proteins suggests that the same tyrosine kinases act at the nuclear envelope of intact cells and at the purified nuclear envelope. We have also identified eight tyrosine-phosphorylated nuclear envelope proteins by 2D BAC/SDS/PAGE, immunoblotting with phosphotyrosine-specific antibodies, tryptic in-gel digestion, and MS analysis of tryptic peptides. These proteins are the lamina proteins lamin A, lamin B1, and lamin B2, the inner nuclear membrane protein LAP2beta, the heat shock protein hsc70, and the DNA/RNA-binding proteins PSF, hypothetical 16-kDa protein, and NonO, which copurify with the nuclear envelope.
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Affiliation(s)
- H Otto
- Freie Universität Berlin, Institut für Chemie-Biochemie, Berlin, Germany
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5
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Mani RS, Hammond JR, Marjan JM, Graham KA, Young JD, Baldwin SA, Cass CE. Demonstration of equilibrative nucleoside transporters (hENT1 and hENT2) in nuclear envelopes of cultured human choriocarcinoma (BeWo) cells by functional reconstitution in proteoliposomes. J Biol Chem 1998; 273:30818-25. [PMID: 9804860 DOI: 10.1074/jbc.273.46.30818] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The equilibrative nucleoside transporters (ENTs) are a newly recognized family of membrane proteins of which hENT1 is the nitrobenzylmercaptopurine ribonucleoside (NBMPR)-sensitive (es) and hENT2 the NBMPR-insensitive (ei) transporter of human cells. BeWo cells exhibit large numbers (>10(7)/cell) of NBMPR-binding sites and high es and ei nucleoside transport activities relative to other cell types. In this work, we have demonstrated that proliferating BeWo cells possess (i) mRNA encoding hENT1 and hENT2 and (ii) hENT1-specific immunoepitopes. We examined NBMPR binding and its inhibition of uridine transport in various BeWo membrane fractions and proteoliposomes derived therefrom to determine if NBMPR binding to intracellular membranes represented interaction with functional es transporters. Unfractionated membranes and fractions enriched 5-fold in plasma membranes relative to postnuclear supernatants exhibited high NBMPR binding activity. Intact nuclei and nuclear envelopes also exhibited abundant quantities of NBMPR-binding sites with affinities similar to those of enriched plasma membranes (Kd = 0.4-0.9 nM). When proteoliposomes were made from octyl glucoside-solubilized membranes, high affinity NBMPR-binding sites were not only observed in crude membrane preparations and plasma membrane-enriched fractions but also in nuclear envelope fractions. Proteoliposomes prepared from either unfractionated membranes or nuclear envelopes exhibited both hENT1-mediated (82-85%) and hENT2-mediated (15-18%) transport of [3H]uridine. These results provided evidence for the presence of functional es and ei transporters in nuclear membranes and endoplasmic reticulum, suggesting that hENT1 and hENT2 may function in the translocation of nucleosides between the cytosol and the luminal compartments of one or both of these membrane types.
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Affiliation(s)
- R S Mani
- Department of Oncology, University of Alberta, Edmonton, Alberta T6G 1Z2, Canada
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6
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Loisel TP, Ansanay H, St-Onge S, Gay B, Boulanger P, Strosberg AD, Marullo S, Bouvier M. Recovery of homogeneous and functional beta 2-adrenergic receptors from extracellular baculovirus particles. Nat Biotechnol 1997; 15:1300-4. [PMID: 9359116 DOI: 10.1038/nbt1197-1300] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Expression in baculovirus-infected insect cells allows sufficient production of G-protein coupled receptor for structural studies. An important drawback of this expression system comes from the presence of unprocessed and biologically inactive receptors that have to be eliminated during receptor purification steps. We show that viral particles released from Sf9 cells infected with a recombinant baculovirus coding for the human beta 2-adrenergic receptor (beta 2AR) cDNA contain glycosylated and biologically active beta 2AR. In addition, post-translational modifications known to modulate receptor activity were found to occur in these particles.
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Affiliation(s)
- T P Loisel
- Département de Biochemie and Le Groupe de Recherche sur le Système Nerveux Autonome, Université de Montréal, Canada
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7
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Abstract
Activity of one of the key enzymes involved in arachidonic acid (20:4 n-6) biosynthesis, the delta 5 desaturase, was found in rat liver cell nuclei. Up to now, it has been shown that the fatty acid desaturases are located exclusively in the endoplasmic reticulum. Similarly to what happens with microsomal enzyme the nuclear delta 5 desaturase enzyme was only fully active in the presence of a cytosolic factor. In this condition it reached a specific activity of 50 pmol 20:4 n-6 formed/min/mg of protein. This fact would imply that purified nuclei like purified microsomes lack a soluble cytosol factor necessary for the total desaturation reaction expression. Besides the nuclear delta 5 desaturase has an optimal pH of 7.6 and is inhibited by 1 or 10 mM KCN. Low long chain acyl-CoA synthetase activity that catalyzes the formation of 20:3 n-6-CoA, was also found in liver nuclei. This step would be essential in nuclear desaturation since when ATP and/or CoA (necessary for the acylation reaction) are omitted from the incubation mixture, the desaturation reaction does not take place.
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Affiliation(s)
- A Ves-Losada
- Instituto de Investigaciones Bioquímicas de La Plata (INIBIOLP), Facultad de Ciencias Médicas, UNLP-CONICET, Argentina
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8
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Abstract
During nuclear assembly, vesicles derived from the mitotic disassembly of the nuclear membranes reform the nuclear envelope. The vesicles first bind to chromosomes, specifically recognize other nuclear vesicles and then fuse to enclose the chromosomes. The proteins that mediate these events are largely unknown. Using reconstituted extracts of Xenopus eggs, we found that nuclear vesicle fusion required elevated (microM) concentrations of free Ca2+ [Sullivan KMC. Busa WB. Wilson KL. (1993) Cell, 73, 1411-1422]. Our data suggest that Ca2+ is released from the vesicle lumen by the activation of IP3 receptors (ligand-gated Ca2+ channels). We propose that the role of IP3 receptors during nuclear assembly may be analogous to that of voltage-gated Ca2+ channels during regulated secretion: to provide a microdomain of high cytosolic Ca2+ that triggers fusion. In this article, we will briefly describe current ideas about nuclear assembly and disassembly, and summarize the evidence that IP3 receptors are required for nuclear vesicle fusion. We will discuss parallels between our results and the role of voltage-gated Ca2+ channels, and Ca2+, in regulated exocytosis. Finally, we will address the question of how IP3 receptors are activated during nuclear vesicle fusion: is there a signal that stimulates IP3 production, or is the channel activated directly?
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Affiliation(s)
- K M Sullivan
- Department of Cell Biology and Anatomy, Johns Hopkins University School of Medicine, Baltimore, Maryland
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9
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Affiliation(s)
- L S Cox
- Department of Biochemistry, University of Dundee, Scotland
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10
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Pasquini F, Bochet P, Garbay-Jaureguiberry C, Roques BP, Rossier J, Beaudet A. Electron microscopic localization of photoaffinity-labelled delta opioid receptors in the neostriatum of the rat. J Comp Neurol 1992; 326:229-44. [PMID: 1336020 DOI: 10.1002/cne.903260206] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The distribution of delta opioid receptors, selectively labelled in vitro with the photoaffinity probe monoiodo azido-DTLET ([D-Thr2,pN3Phe4, Leu5]enkephaly-Thr6), was analyzed by light and electron microscopic radioautography in sections from rat neostriatum. Preliminary experiments indicated that up to 65% of specific 125I-azido-DTLET binding to rat striatal sections was still detectable following prefixation of the brain with 0.5% glutaraldehyde. These experiments also showed that up to 20-30% of the specifically bound radioactivity was covalently linked following ultraviolet irradiation and was thereby retained in tissue during subsequent postfixation and dehydration steps. Accordingly, the topographic distribution of the covalently attached azido-DTLET molecules was similar to that seen in fresh frozen sections and characteristic of that previously described for delta sites. Light and electron microscopic examination of the label in prefixed, striatal sections irradiated with ultraviolet light revealed that a significant proportion of specifically bound 125I-azido-DTLET molecules was intraneuronal. Specifically, 16% of the labelled binding sites were found in dendrites, 12% in perikarya and 4% in axon terminals. These results suggest that an important proportion of delta opioid binding sites labelled in the neostriatum correspond to receptors that are undergoing synthesis, transport and/or recycling. They also imply that a major fraction of delta sites are associated with intrastriatal neurons, as opposed to afferent axons. Approximately 44% of the labelled binding sites were associated with neuronal plasma membranes. Although most of these were found at the level of axodendritic (20%) and dendrodendritic (7%) appositions, comparison of the labelling incidence of these two compartments with their frequency of occurrence in tissue suggested that delta sites are fairly widely dispersed along neuronal plasma membranes. Only a small proportion (smaller than that of mu or kappa sites labelled in the same region) was associated with synaptic specializations. These results support the concept that delta receptors correspond to molecular entities that are distinct from mu and kappa sites and suggest that delta ligands act primarily nonjunctionally on the plasma membrane of striatal neurons.
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Affiliation(s)
- F Pasquini
- Montreal Neurological Institute, McGill University, Quebec, Canada
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11
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Rich SA, Marko M, Gibbons WE. Localization of interferon-induced lupus inclusions demonstrated by computer image reconstruction of monensin-treated Daudi cells. J Struct Biol 1992; 108:25-34. [PMID: 1373290 DOI: 10.1016/1047-8477(92)90004-t] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
A structural analysis of cells that contained the interferon-alpha-induced lupus inclusions (LI) was performed using a high-voltage electron microscope to determine the exact cellular location of LI and their association with normal cell organelles. LI were induced in the human B lymphoblastoid cell line, Daudi, by culturing with the pure recombinant human leukocyte interferon, IFLrA. Just prior to harvesting, a portion of the cells was treated with monensin to selectively swell the Golgi apparatus, and thereby simplify their identification using the electron microscope. Organellar associations between LI and the outer nuclear envelope and Golgi apparatus were identified in stereopairs of 1-micron sections prepared from both cells that were not treated with monensin and those that were treated with monensin. Serial 0.25-micron sections of the monensin-treated cells were prepared, and seven arbitrarily chosen cells were examined. Each of these cells contained a single LI, and it formed throughout an endoplasmic-reticulum region that made contact with both the outer nuclear envelope and the Golgi vesicles. Reconstruction of a cell by computer from the digitized negatives of serial sections clearly illustrated these relationships. This study reports the first determination of the association between LI and the Golgi apparatus. It also identifies the presence of only one LI in every cell, and the routine association of the LI with both the outer nuclear envelope and the Golgi apparatus. The unique cell location of LI formation suggests their functioning in membrane biogenesis, the trafficking of proteins to the plasma membrane or to cytoplasmic vesicles, or the processing of proteins for secretion.
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Affiliation(s)
- S A Rich
- Laboratory of Biophysics, Wadsworth Center for Laboratories and Research, New York State Department of Health, Albany 12201-0509
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12
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Peeples ME, Wang C, Gupta KC, Coleman N. Nuclear entry and nucleolar localization of the Newcastle disease virus (NDV) matrix protein occur early in infection and do not require other NDV proteins. J Virol 1992; 66:3263-9. [PMID: 1560547 PMCID: PMC241099 DOI: 10.1128/jvi.66.5.3263-3269.1992] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
A large proportion of the Newcastle disease virus (NDV) matrix (M) protein is found in the nuclei of infected chicken embryo cells. Kinetic analysis indicated that much of the M protein enters the nucleus early in infection, concentrating in discrete regions of the nucleus and remaining there throughout infection. The M protein was found in localized regions of the nuclei of a variety of cell lines infected with NDV. Immunostaining for both M protein and nucleolar antigens indicated that most of these regions represent nucleoli. Moreover, this nucleolar localization of the M protein was observed in chicken embryo cells infected with 11 different strains of NDV. Only the M protein of strain HP displayed a modified pattern, concentrating in the nucleolus early in infection but in the cytoplasm late in infection. M protein transiently expressed in COS-1 cells also localized to the nucleus and nucleolus, indicating that the M protein does not require other NDV proteins for this localization.
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Affiliation(s)
- M E Peeples
- Department of Immunology/Microbiology, Rush-Presbyterian-St. Luke's Medical Center, Chicago, Illinois 60612
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13
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Szigethy E, Leonard K, Beaudet A. Ultrastructural localization of [125I]neurotensin binding sites to cholinergic neurons of the rat nucleus basalis magnocellularis. Neuroscience 1990; 36:377-91. [PMID: 1699163 DOI: 10.1016/0306-4522(90)90433-5] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The distribution of specifically-labeled neurotensin binding sites was examined in relation to that of cholinergic neurons in the rat nucleus basalis magnocellularis at both light and electron microscopic levels. Lightly prefixed forebrain slices were either labeled with [125I](Tyr3) neurotensin alone or processed for combined [125I]neurotensin radioautography and acetylcholinesterase histochemistry. In light microscopic radioautographs from 1-microns-thick sections taken from the surface of single-labeled slices, silver grains were found to be preferentially localized over perikarya and proximal processes of nucleus basalis cells. The label was distributed both throughout the cytoplasm and along the plasma membrane of magnocellular neurons all of which were found to be cholinesterase-positive in a double-labeled material. Probability circle analysis of silver grain distribution in electron microscopic radioautographs confirmed that the major fraction (80-89%) of specifically-labeled binding sites associated with cholinesterase-reactive cell bodies and dendrites was intraneuronal. These intraneuronal sites were mainly dispersed throughout the cytoplasm and are thus likely to represent receptors undergoing synthesis, transport and/or recycling. A proportion of the specific label was also localized over the nucleus, suggesting that neurotensin could modulate the expression of acetylcholine-related enzymes in the nucleus basalis. The remainder of the grains (11-20%) were classified as shared, i.e. overlied the plasma membrane of acetylcholinesterase-positive neuronal perikarya and dendrites. Extrapolation from light microscopic data, combined with the observation that shared grains were detected at several contact points along the plasma membrane of cells which also exhibited exclusive grains, made it possible to ascribe these membrane-associated receptors to the cholinergic neurons themselves rather than to abutting cellular profiles. Comparison of grain distribution with the frequency of occurrence of elements directly abutting the plasma membrane of neurotensin-labeled/cholinesterase-positive perikarya indicated that labeled cell surface receptors were more or less evenly distributed along the membrane as opposed to being concentrated opposite abutting axon terminals endowed or not with a visible junctional specialization. The low incidence of labeled binding sites found in close association with abutting axons makes it unlikely that only this sub-population of sites corresponds to functional receptors. On the contrary, the dispersion of labeled receptors seen here along the plasma membrane of cholinergic neurons suggests that neurotensin acts primarily in a paracrine mode to influence the magnocellular cholinergic system in the nucleus basalis.
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Affiliation(s)
- E Szigethy
- Laboratory of Neuroanatomy, Montreal Neurological Institute, Montreal, Quebec, Canada
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14
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Pico RM, Gall C. Continuities between outer nuclear membrane and the rough endoplasmic reticulum increase in hippocampal neurons during seizure-induced protein synthesis. Brain Res 1989; 497:387-92. [PMID: 2819433 DOI: 10.1016/0006-8993(89)90286-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The ultrastructure of rat dentate gyrus granule cells was examined during, and near the termination of, a period of lesion-induced recurrent limbic seizure activity which has previously been demonstrated to stimulate dramatic changes in the biosynthetic activities of these neurons. In animals sacrificed 5 h postlesion (or 3.5 h following seizure onset) the rough endoplasmic reticulum (RER) appeared more extensive than in controls and there was a large, statistically significant increase in the number of continuities between the RER and the outer nuclear membrane (ONM). By 11 h postlesion the latter index had returned to control values although the presence of numerous elevations of the ONM lying in close proximity to free segments of RER was considered indicative of recent dissolution of contact. These data demonstrate modifications in the arrangement of organelles involved in protein synthesis during a period in which the patterns of synthesis by the granule cells are changing but which do not persist through the full period of seizure-induced alterations in synthetic activity.
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Affiliation(s)
- R M Pico
- Department of Anatomy and Neurobiology, University of California, Irvine 92717
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15
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Pryme IF. The nuclear-associated endoplasmic reticulum. THE INTERNATIONAL JOURNAL OF BIOCHEMISTRY 1989; 21:119-25. [PMID: 2663557 DOI: 10.1016/0020-711x(89)90099-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- I F Pryme
- Department of Biochemistry, University of Bergen, Norway
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16
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Abstract
The M protein of vesicular stomatitis virus (VSV) was localized in the nuclei and cytoplasm of VSV-infected cells by subcellular fractionation and immunofluorescence microscopy. Nuclei isolated from VSV-infected Friend erythroleukemia cells were fractionated into a nuclear membrane and a nucleoplasm fraction by DNase digestion and differential centrifugation. G protein was present in the membrane fraction, and M protein was present in the nucleoplasm fraction. Immunofluorescence detection of M protein in the nucleus required that fixed cells be permeabilized with higher concentrations of detergent than were required for detection of M protein in the cytoplasm of VSV-infected BHK cells.
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Affiliation(s)
- D S Lyles
- Department of Microbiology and Immunology, Bowman Gray School of Medicine, Wake Forest University, Winston-Salem, North Carolina 27103
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17
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Omary MB, Kagnoff MF. Identification of nuclear receptors for VIP on a human colonic adenocarcinoma cell line. Science 1987; 238:1578-81. [PMID: 2825352 DOI: 10.1126/science.2825352] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Vasoactive intestinal peptide (VIP) is a neuropeptide with broad tissue distribution. Although its precise function is unknown, it is thought to exert its effect, at least in part, by interacting with cell surface receptors. Nuclear receptors for VIP have now been identified by specific binding of 125I-labeled VIP to nuclei of a human colonic adenocarcinoma cell line (HT29) and by cross-linking of 125I-labeled VIP to its receptor on intact nuclei. In contrast, 125I-labeled transferrin shows only background binding to nuclei but significant binding to intact cells. Purity of the isolated nuclei was further substantiated by electron microscopy. The apparent molecular sizes of the VIP--cross-linked nuclear and cell surface receptors are similar but not identical.
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Affiliation(s)
- M B Omary
- Department of Medicine, University of California, San Diego, La Jolla 92093
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