1
|
Wang Q, Slegers H, Clauwaert J. Isolation of plasma membranes from rat C6 glioma cells cultivated on microcarriers. Acta Histochem 1999; 101:327-39. [PMID: 10443295 DOI: 10.1016/s0065-1281(99)80033-6] [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: 11/27/2022]
Abstract
We have studied the feasibility of rat C6 glioma cell cultivation on microcarrier beads and the isolation of their plasma membranes from the beads. Cells were cultivated on Cytodex-1 microcarrier beads and the plasma membranes were subsequently isolated from confluent cell monolayers on the beads. This approach yielded approximately 4 x 10(6) cells/ml in a 1 L spinner vessel. Enzymatic assays indicated an 18-fold enrichment of plasma membranes isolated from the beads with minor contamination by other cell organelles. Assay for IGF-I receptor binding capacity revealed that 70% of the total receptor binding capacity could be recovered in the plasma membrane fraction isolated from the beads as compared with the receptor binding capacity of intact cells, demonstrating the functional integrity of the isolated membranes. Electron microscopy and immunofluorescence analysis indicated that the isolated plasma membranes were highly homogeneous with the majority exposing the cytoplasmic surface. Our procedure of C6 glioma cell cultivation on microcarriers and subsequent plasma membrane isolation, provides large quantities of homogeneous and metabolically active membranes which can be used to study receptor-mediated effects on cell proliferation and differentiation.
Collapse
Affiliation(s)
- Q Wang
- Department of Biochemistry, University of Antwerp, Belgium
| | | | | |
Collapse
|
2
|
Feany MB, Yee AG, Delvy ML, Buckley KM. The synaptic vesicle proteins SV2, synaptotagmin and synaptophysin are sorted to separate cellular compartments in CHO fibroblasts. J Cell Biol 1993; 123:575-84. [PMID: 7901222 PMCID: PMC2200136 DOI: 10.1083/jcb.123.3.575] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
We expressed the synaptic vesicle proteins SV2, synaptotagmin, and synaptophysin in CHO fibroblasts to investigate the targeting information contained by each protein. All three proteins entered different cellular compartments. Synaptotagmin was found on the plasma membrane. Both SV2 and synaptophysin were sorted to small intracellular vesicles, but synaptophysin colocalized with early endosomal markers, while SV2 did not. SV2-containing vesicles did not have the same sedimentation characteristics as authentic synaptic vesicles, even though transfected SV2 was sorted from endosomal markers. We also created cell lines expressing both SV2 and synaptotagmin, both synaptotagmin and synaptophysin, and lines expressing all three synaptic vesicle proteins. In all cases, the proteins maintained their distinct compartmentalizations, were not found in the same organelle, and did not created synaptic vesicle-like structures. These results have important implications for models of synaptic vesicle biogenesis.
Collapse
Affiliation(s)
- M B Feany
- Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115
| | | | | | | |
Collapse
|
3
|
Paul S, Ebadi M. Vasoactive intestinal peptide: its interactions with calmodulin and catalytic antibodies. Neurochem Int 1993; 23:197-214. [PMID: 8220166 DOI: 10.1016/0197-0186(93)90111-h] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- S Paul
- Department of Anesthesiology, University of Nebraska Medical Center, Omaha 68198-6830
| | | |
Collapse
|
4
|
Feany MB, Buckley KM. The synaptic vesicle protein synaptotagmin promotes formation of filopodia in fibroblasts. Nature 1993; 364:537-40. [PMID: 8166886 DOI: 10.1038/364537a0] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Neuronal filopodia are actin-rich cytoplasmic extensions that are involved in motility and recognition in growth cones and maturing axonal endings. A detailed understanding of neuronal growth will depend on clarification of the membrane fusion events occurring during filopodial extension. The synaptic vesicle protein synaptotagmin seems to be intimately involved in exocytotic membrane fusion. Here we show that fibroblast cell lines transfected with synaptotagmin form long, highly branched, actin-rich filopodial processes, with the expressed synaptotagmin being incorporated into the plasma membrane. In contrast, cell lines expressing either of two other synaptic vesicle proteins, SV2 or synaptophysin, generate only rudimentary processes, and, like neurons, sort SV2 and synaptophysin to small intracellular vesicles. As presynaptic calcium entry regulates synaptic vesicle fusion, our results indicate that synaptotagmin might link neuronal activity with synaptic growth.
Collapse
Affiliation(s)
- M B Feany
- Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115
| | | |
Collapse
|
5
|
Stallwood D, Brugger C, Baggenstoss B, Stemmer P, Shiraga H, Landers D, Paul S. Identity of a membrane-bound vasoactive intestinal peptide-binding protein with calmodulin. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)41819-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
|
6
|
Trifaró JM, Vitale ML, Rodríguez Del Castillo A. Cytoskeleton and molecular mechanisms in neurotransmitter release by neurosecretory cells. Eur J Pharmacol 1992; 225:83-104. [PMID: 1348034 DOI: 10.1016/0922-4106(92)90088-d] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The process of exocytosis is a fascinating interplay between secretory vesicles and cellular components. Secretory vesicles are true organelles which not only store and protect neurotransmitters from inactivation but also provide the cell with efficient carriers of material for export. Different types of secretory vesicles are described and their membrane components compared. Associations of several cytoplasmic proteins and cytoskeletal components with secretory vesicles and the importance of such associations in the mechanism of secretion are discussed. A description of possible sites of action for Ca2+ as well as possible roles for calmodulin, G-proteins and protein kinase C in secretion are also presented. Important aspects of the cytoskeleton of neurosecretory cells are discussed. The cytoskeleton undergoes dynamic changes as a result of cell stimulation. These changes (i.e. actin filament disassembly) which are a prelude to exocytosis, play a central role in secretion. Moreover, advanced electrophysiological techniques which allow the study of secretory vesicle-plasma membrane fusion in real-time resolution and at the level of the single secretory vesicle, have also provided a better understanding of the secretory process.
Collapse
Affiliation(s)
- J M Trifaró
- Department of Pharmacology, University of Ottawa, Ontario, Canada
| | | | | |
Collapse
|
7
|
Pape R, Plattner H. Secretory organelle docking at the cell membrane of Paramecium cells: dedocking and synchronized redocking of trichocysts. Exp Cell Res 1990; 191:263-72. [PMID: 2257880 DOI: 10.1016/0014-4827(90)90013-z] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
We present the first evidence that secretory organelle docking at the cell membrane can be reversed in vivo. In nondischarge (nd) mutants of Paramecium tetraurelia all trichocysts can be detached from the cell surface within 2-3 h by different means, including cytochalasin B (but not D), high cell density, or Ca2+ ionophores. Considering the well-established ultrastructural differences between nd and wild-type (wt) cells, one can conclude that trichocyst docking at the cell periphery involves two docking sites (I, II): Site I ties the organelles to the epiplasm, and site II is the connection to the cell membrane at the fusogenic zone (expressed only in wt cells); both sites are close to the cell surface and only 150 nm apart. When the trigger for detachment of cortically docked trichocysts (high cell density, cytochalasin B) is relieved, trichocysts are synchronously reattached at the cell membrane, within 40-50 min, with a rate of 20-40 organelles/min, which far exceeds spontaneous docking rates. This is therefore also the first report on synchronization of secretory organelle docking. It is shown by radioactive leucine labeling that the same organelles are redocked, because trichocyst biogenesis is minimal under the conditions of de/redocking used. Surprisingly not only redocking but also detachment of trichocysts from the cell surface can be abolished by inhibitors of protein synthesis. Since Ca2+ ionophores mimic the effects of other conditions sufficient to detach trichocysts from the cell surface, we assume that a protein-dependent mechanism sensitive to Ca2+ (or other ions in exchange) may operate in trichocyst detachment. The precise mechanism involved in attachment or detachment of trichocysts remains to be elucidated.
Collapse
Affiliation(s)
- R Pape
- Faculty of Biology, University of Konstanz, Federal Republic of Germany
| | | |
Collapse
|
8
|
De Block J, Petit K, Van Laer L, Dillen L, Roggen E, De Potter W. Calmodulin-binding proteins in granule and plasma membranes from bovine chromaffin cells. BIOCHIMICA ET BIOPHYSICA ACTA 1990; 1030:134-42. [PMID: 2265187 DOI: 10.1016/0005-2736(90)90248-m] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Calmodulin-binding proteins in chromaffin granule membrane and chromaffin cell plasma membranes have been investigated and compared. Chromaffin granules were purified by centrifugation over a 1.7 M sucrose layer. Plasma membranes were obtained in a highly purified form by differential and isopycnic centrifugation. Enzymatic determinations of 5'-nucleotidase, a generally accepted plasma membrane marker, showed a 40-50-fold enrichment as compared to the cell homogenate. Marker enzyme studies demonstrated only minimal contamination by other subcellular organelles. After solubilization with Triton X-100, calmodulin-binding proteins were isolated from chromaffin granule membranes and plasma membranes by affinity chromatography on a calmodulin/Sepharose 4B column. On two-dimensional polyacrylamide gelelectrophoresis a prominent protein (Mr = 65,000, pI ranging from 5.1 to 6) consisting of multiple spots, was present in the calmodulin-binding fraction from chromaffin granule membranes as well as from plasma membranes. Besides this 65 kDa protein both fractions had at least four groups of proteins in common. Also, proteins typical for either preparation were observed. In the calmodulin-binding protein preparations from chromaffin granule membranes a prominent spot with Mr = 80,000 and a pH ranging from 5.0 to 5.7 was present. This protein was enzymatically and immunologically identified as dopamine-beta-monooxygenase.
Collapse
Affiliation(s)
- J De Block
- Department of Medicine, University of Antwerp (UIA), Wilrijk, Belgium
| | | | | | | | | | | |
Collapse
|
9
|
Howard BD, Cho AK, Zhang MB, Koide M, Lin S. Covalent labeling of the cocaine-sensitive catecholamine transporter. J Neurosci Res 1990; 26:149-58. [PMID: 2142222 DOI: 10.1002/jnr.490260204] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Xylamine is an alkylating agent that is a substrate for and specific irreversible inhibitor of the cocaine-sensitive catecholamine transporter that functions in catecholamine reuptake into neurons and PC12 cells. [3H]xylamine prominently labels nine PC12 proteins; the relative xylamine-alkylation of a Mr 54,000 protein was decreased by cocaine and increased in the case of a PC12 variant, B9, which is deficient in catecholamine transport. [3H]xylamine labels no such protein in another transport variant, MPT1. We propose that this Mr 54,000 protein 1) is a component of the catecholamine transporter, 2) is present in B9 cells but in a conformation that reduces transporter activity and makes alkylation by xylamine more likely, and 3) is absent in MPT1 cells. Nerve growth factor treatment restores transporter activity in B9 cells but not in other transporter-deficient variants.
Collapse
Affiliation(s)
- B D Howard
- Department of Biological Chemistry, UCLA School of Medicine 90024
| | | | | | | | | |
Collapse
|
10
|
Plattner H. Regulation of membrane fusion during exocytosis. INTERNATIONAL REVIEW OF CYTOLOGY 1990; 119:197-286. [PMID: 2695484 DOI: 10.1016/s0074-7696(08)60652-x] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- H Plattner
- Faculty of Biology, University of Konstanz, Federal Republic of Germany
| |
Collapse
|
11
|
Fournier S, Novas ML, Trifaró JM. Subcellular distribution of 65,000 calmodulin-binding protein (p65) and synaptophysin (p38) in adrenal medulla. J Neurochem 1989; 53:1043-9. [PMID: 2504884 DOI: 10.1111/j.1471-4159.1989.tb07393.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Both neuronal and endocrine cells contain secretory vesicles that store and release neurotransmitters and peptides. Neuronal cells release their secretory material from both small synaptic vesicles and large dense-core vesicles (LDCVs), whereas endocrine cells release secretory products from LDCVs. Neuronal small synaptic vesicles are known to express three integral membrane proteins: 65,000 calmodulin-binding protein (65-CMBP) (p65), synaptophysin (p38), and SV2. A controversial question surrounding these three proteins is whether they are present in LDCV membranes of endocrine and neuronal cells. Sucrose density centrifugation of adrenal medulla was performed to study and compare the subcellular distribution of two of these small synaptic vesicle proteins (65-CMBP and synaptophysin). Subsequent immunoblotting and 125I-Protein A binding experiments performed on the fractions obtained from sucrose gradients showed that 65-CMBP was present in fractions corresponding to granule membranes and intact chromaffin granules. Similar immunoblotting and 125I-Protein A binding experiments with synaptophysin antibodies showed that this protein was also present in intact granules and granule membrane fractions. However, an additional membrane component, equilibrating near the upper portion of the sucrose gradient, also showed strong immunoreactivity with anti-synaptophysin and high 125I-Protein A binding activity. In addition, immunoblotting experiments on purified plasma and granule membranes demonstrated that 65-CMBP was a component of both membranes, whereas synaptophysin was only present in granule membranes. Thus, there appears to be a different subcellular localization between 65-CMBP and synaptophysin in the chromaffin cell.
Collapse
Affiliation(s)
- S Fournier
- Department of Pharmacology, McGill University, Montreal, Quebec, Canada
| | | | | |
Collapse
|
12
|
Doucet JP, Fournier S, Parulekar M, Trifaró JM. Detection of low molecular mass GTP-binding proteins in chromaffin granules and other subcellular fractions of chromaffin cells. FEBS Lett 1989; 247:127-31. [PMID: 2495990 DOI: 10.1016/0014-5793(89)81254-2] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
A homogenate of purified chromaffin cells was fractionated, after removal of the nuclear fraction, by sucrose density gradient ultracentrifugation. The presence and subcellular localization of low molecular mass GTP-binding proteins was explored by incubation of blots of proteins from different subcellular fractions with [alpha-32P]GTP in the presence of Mg2+. The fractions enriched in intact chromaffin granule markers, i.e. catecholamines, chromogranin A, chromogranin B and cytochrome b-561 were also enriched in labelled GTP-binding proteins. Two major labelled components of 23 and 29 kDa were rapidly detected by autoradiography. Traces of 26 and 27 kDa components were also present. These components were detectable in both plasma and granule membranes. In addition to these components, the cytosolic fraction contained another GTP-binding protein of about 20 kDa. Binding of [alpha-32P]GTP was specific and dependent on Mg2+. By analogy to the findings reported in non-mammalian systems, the observations described here suggest the involvement of low molecular mass GTP-binding proteins in the chromaffin cell secretory process.
Collapse
Affiliation(s)
- J P Doucet
- Department of Pharmacology, Faculty of Health Sciences, University of Ottawa, Ontario, Canada
| | | | | | | |
Collapse
|
13
|
Trifaró JM, Fournier S, Novas ML. The p65 protein is a calmodulin-binding protein present in several types of secretory vesicles. Neuroscience 1989; 29:1-8. [PMID: 2651966 DOI: 10.1016/0306-4522(89)90327-8] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- J M Trifaró
- Department of Pharmacology, School of Medicine, University of Ottawa, Ontario, Canada
| | | | | |
Collapse
|