701
|
Abstract
Recent advances have uncovered the general protein apparatus used by all eukaryotes for intracellular transport, including secretion and endocytosis, and for triggered exocytosis of hormones and neurotransmitters. Membranes are shaped into vesicles by cytoplasmic coats which then dissociate upon GTP hydrolysis. Both vesicles and their acceptor membranes carry targeting proteins which interact specifically to initiate docking. A general apparatus then assembles at the docking site and fuses the vesicle with its target.
Collapse
Affiliation(s)
- J E Rothman
- Cellular Biochemistry and Biophysics Program, Memorial Sloan-Kettering Cancer Center, New York, New York 10021
| |
Collapse
|
702
|
Effects of acid phospholipids on nucleotide exchange properties of ADP-ribosylation factor 1. Evidence for specific interaction with phosphatidylinositol 4,5-bisphosphate. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(18)46904-9] [Citation(s) in RCA: 85] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
|
703
|
Randazzo PA, Terui T, Sturch S, Kahn RA. The amino terminus of ADP-ribosylation factor (ARF) 1 is essential for interaction with Gs and ARF GTPase-activating protein. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(18)43906-3] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
|
704
|
Schmidt M, Hüwe SM, Fasselt B, Homann D, Rümenapp U, Sandmann J, Jakobs KH. Mechanisms of phospholipase D stimulation by m3 muscarinic acetylcholine receptors. Evidence for involvement of tyrosine phosphorylation. EUROPEAN JOURNAL OF BIOCHEMISTRY 1994; 225:667-75. [PMID: 7957182 DOI: 10.1111/j.1432-1033.1994.00667.x] [Citation(s) in RCA: 78] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
In human embryonic kidney cells stably expressing the human m3 muscarinic acetylcholine receptor (mAChR) subtype, agonist (carbachol) activation stimulated phospholipase C, increased cytoplasmic calcium concentration, induced tyrosine phosphorylation of various cellular proteins and activated phospholipase D. Bypassing membrane receptors, phospholipase D was activated in these cells by direct activation of protein kinase C by phorbol esters, by direct activation of GTP-binding proteins by A1F4- and a stable GTP analogue (in permeabilized cells), by increasing cytoplasmic calcium concentration with the calcium ionophore A23187 and also apparently by tyrosine phosphorylation. In order to identify possible mechanisms by which the m3 mAChR couples to phospholipase D, various inhibitors of protein kinase C, tyrosine kinases and calcium-dependent events were studied. Prevention of an agonist-induced increase in cytoplasmic calcium concentration did not alter the mAChR-induced phospholipase D stimulation. The protein kinase C inhibitors, calphostin C and staurosporine, efficiently prevented phospholipase D activation by phorbol 12-myristate 13-acetate but only partially inhibited the activation induced by the mAChR agonist. Additionally, down-regulation of protein kinase C by prolonged exposure to phorbol 12-myristate 13-acetate abrogated phospholipase D activation by this effector but had only minor or no effects on the response to the mAChR agonist and direct activators of GTP-binding proteins. In contrast, the tyrosine kinase inhibitor genistein abolished the carbachol-induced and A1F4(-)-induced phospholipase D activation but had no effect on enzyme activation by phorbol 12-myristate 13-acetate. The data indicate that phospholipase D in m3 mAChR-expressing human embryonic kidney cells can be activated by various different mechanisms, i.e. receptor agonists, GTP-binding proteins, protein kinase C-dependent and calcium-dependent events and tyrosine phosphorylation. The coupling of m3 mAChR to phospholipase D appears to be largely independent of concomitant phospholipase C activation with subsequent increase in cytoplasmic calcium concentration and protein kinase C activity. The data instead suggest the involvement of an essential protein tyrosine phosphorylation mechanism in phopsholipase D activation by the m3 mAChR and heterotrimeric GTP-binding proteins.
Collapse
Affiliation(s)
- M Schmidt
- Institut für Pharmakologie, Universität GH Essen, Germany
| | | | | | | | | | | | | |
Collapse
|
705
|
Pavlidis P, Ramaswami M, Tanouye MA. The Drosophila easily shocked gene: a mutation in a phospholipid synthetic pathway causes seizure, neuronal failure, and paralysis. Cell 1994; 79:23-33. [PMID: 7923374 DOI: 10.1016/0092-8674(94)90397-2] [Citation(s) in RCA: 169] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
We have characterized easily shocked (eas), a Drosophila "band-sensitive" paralytic mutant. Electrophysiological recordings from flight muscles in the giant fiber pathway of adult eas flies reveal that induction of paralysis with electrical stimulation results in a brief seizure, followed by a failure of the muscles to respond to giant fiber stimulation. Molecular cloning, germline transformation, and biochemical experiments show that eas mutants are defective in the gene for ethanolamine kinase, which is required for a pathway of phosphatidylethanolamine synthesis. Assays of phospholipid composition reveal that total phosphatidylethanolamine is decreased in eas mutants. The data suggest that eas bang sensitivity is due to an excitability defect caused by altered membrane phospholipid composition.
Collapse
Affiliation(s)
- P Pavlidis
- Department of Molecular and Cell Biology, University of California, Berkeley 94720
| | | | | |
Collapse
|
706
|
Malcolm KC, Ross AH, Qiu RG, Symons M, Exton JH. Activation of rat liver phospholipase D by the small GTP-binding protein RhoA. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(18)47140-2] [Citation(s) in RCA: 149] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
|
707
|
Venable ME, Blobe GC, Obeid LM. Identification of a defect in the phospholipase D/diacylglycerol pathway in cellular senescence. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(18)47156-6] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
|
708
|
Export of protein from the endoplasmic reticulum is regulated by a diacylglycerol/phorbol ester binding protein. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(18)47097-4] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
|
709
|
Higgs HN, Glomset JA. Identification of a phosphatidic acid-preferring phospholipase A1 from bovine brain and testis. Proc Natl Acad Sci U S A 1994; 91:9574-8. [PMID: 7937808 PMCID: PMC44855 DOI: 10.1073/pnas.91.20.9574] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Recent experiments in several laboratories have provided evidence that phosphatidic acid functions in cell signaling. However, the mechanisms that regulate cellular phosphatidic acid levels remain obscure. Here we describe a soluble phospholipase A1 from bovine testis that preferentially hydrolyzes phosphatidic acid when assayed in Triton X-100 micelles. Moreover, the enzyme hydrolyzes phosphatidic acid molecular species containing two unsaturated fatty acids in preference to those containing a combination of saturated and unsaturated fatty acyl groups. Under certain conditions, the enzyme also displays lysophospholipase activity toward lysophosphatidic acid. The phospholipase A1 is not likely to be a lysosomal enzyme because its optimum pH is 7.5-8.5. Furthermore, it is probably not a general lipid metabolic enzyme because high levels of activity are found in mature testis and brain but no measurable activity is seen in liver, spleen, or heart. The fact that the activity of the phospholipase A1 in mature bovine testis is > 10-fold higher than that in newborn calf testis raises the possibility that the enzyme may play a regulatory role in spermatogenesis or sperm function.
Collapse
Affiliation(s)
- H N Higgs
- Department of Biochemistry, Howard Hughes Medical Institute, University of Washington, Seattle 98195
| | | |
Collapse
|
710
|
Whatmore J, Cronin P, Cockcroft S. ARF1-regulated phospholipase D in human neutrophils is enhanced by PMA and MgATP. FEBS Lett 1994; 352:113-7. [PMID: 7925957 DOI: 10.1016/0014-5793(94)00930-9] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Human neutrophil PLD activity stimulated with GTP-gamma-S was reconstituted with recombinant ARF1 in cytosol-depleted cells. PMA-pretreatment of intact cells greatly enhanced the subsequent reconstitution of the ARF1-regulated PLD activity. This enhancement was only observed provided that the intact cells were pretreated with PMA, suggesting the stable recruitment of a cytosolic component, presumably protein kinase C, to the membranes. rARF1-reconstituted PLD activity was not dependent on MgATP, but could be considerably enhanced by MgATP. Maximal effects of MgATP were seen at 1 mM. This enhancement by MgATP could not be attributed to protein kinase C. Neomycin was found to inhibit ARF1-regulated PLD activity suggesting the requirement for polyphosphoinositides. We conclude: (i) that many of the observed effects of PMA may be dependent on the presence of the small GTP-binding protein, ARF, and (ii) polyphosphoinositides are required for ARF1-stimulated PLD activity.
Collapse
Affiliation(s)
- J Whatmore
- Department of Physiology, University College London, UK
| | | | | |
Collapse
|
711
|
Kiss Z, Tomono M, Anderson WB. Phorbol ester selectively stimulates the phospholipase D-mediated hydrolysis of phosphatidylethanolamine in multidrug-resistant MCF-7 human breast carcinoma cells. Biochem J 1994; 302 ( Pt 3):649-54. [PMID: 7945188 PMCID: PMC1137280 DOI: 10.1042/bj3020649] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The phospholipase D (PLD)-mediated synthesis of phosphatidylethanol (PtdEtOH) and the hydrolysis of phosphatidylethanolamine (PtdEtn) and phosphatidylcholine (PtdCho) were examined in drug-sensitive and multidrug-resistant lines of MCF-7 human breast carcinoma cells. In drug-sensitive (MCF-7/WT) cells, the protein kinase C (PKC) activator phorbol 12-myristate 13-acetate (PMA) failed to enhance either the synthesis of PtdEtOH or the hydrolysis of either phospholipid. In the drug-resistant (MCF-7/MDR) cells, 100 nM PMA greatly enhanced both the synthesis of PtdEtOH (approximately 21-fold) and the hydrolysis of PtdEtn (approximately 29-fold), but had no effect on the hydrolysis of PtdCho. The PLD activators sphingosine and H2O2 were found to elicit only a slight (1.28-1.4-fold) stimulatory effect on PtdCho hydrolysis in both the MCF-7/WT and MCF-7/MDR cell types, and had only a small effect on PtdEtn hydrolysis in the MCF-7/WT cells as well. However, these agents significantly (approximately 2.6-3.5-fold) stimulated PtdEtn hydrolysis in the MCF-7/MDR cells. These data indicate that MCF-7/MDR cells contain a PtdEtn-specific PLD activity which can be selectively stimulated by PMA, sphingosine and H2O2.
Collapse
Affiliation(s)
- Z Kiss
- Hormel Institute, University of Minnesota, Austin 55912
| | | | | |
Collapse
|
712
|
Huang M, Jolicoeur P. Myristylation of Pr60gag of the murine AIDS-defective virus is required to induce disease and notably for the expansion of its target cells. J Virol 1994; 68:5648-55. [PMID: 8057445 PMCID: PMC236966 DOI: 10.1128/jvi.68.9.5648-5655.1994] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Murine AIDS (MAIDS) is characterized by severe lymphadenopathy and splenomegaly. The proliferation of the infected target B cells is also an important manifestation of the disease (M. Huang, C. Simard, D. G. Kay, and P. Jolicoeur, J. Virol. 65:6562-6571, 1991). The etiologic agent of MAIDS is a defective murine leukemia virus that is deleted of most of its pol and env genes and appears to encode a single protein, the Gag precursor Pr60gag protein. Pr60gag is myristylated and attached to the plasma membrane. To study the role myristylation on the function of Pr60gag, we have generated a myristylation-negative (Myr-) mutant of the MAIDS defective virus. We found that Myr- Pr60gag interacted less tightly with the plasma membrane. In addition, the Myr- MAIDS defective virus mutant was unable to induce expansion of infected cells and was nonpathogenic. These results emphasize the essential role of Pr60gag in the disease process. Our data also suggest that Pr60gag, once recruited to the cell membrane through its myristylation, interacts with other membrane-bound effectors to send signals to induce proliferation of the infected cells and to initiate immune dysfunctions.
Collapse
Affiliation(s)
- M Huang
- Laboratory of Molecular Biology, Clinical Research Institute of Montreal, Québec, Canada
| | | |
Collapse
|
713
|
Redmond T, Tardif M, Zigmond S. Induction of actin polymerization in permeabilized neutrophils. Role of ATP. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)31856-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
|
714
|
Novel function of phosphatidylinositol 4,5-bisphosphate as a cofactor for brain membrane phospholipase D. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)31816-1] [Citation(s) in RCA: 223] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
|
715
|
|
716
|
Donaldson JG, Klausner RD. ARF: a key regulatory switch in membrane traffic and organelle structure. Curr Opin Cell Biol 1994; 6:527-32. [PMID: 7986529 DOI: 10.1016/0955-0674(94)90072-8] [Citation(s) in RCA: 210] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The small GTP-binding protein ADP ribosylation factor (ARF) regulates, through a GTP cycle, the reversible binding of cytosolic coat proteins to Golgi membranes. By determining the binding and release of coat proteins from membranes, ARF controls the production and lifetime of coated-membrane structures. In the past year, studies suggesting a role for ARF in phospholipid metabolism have broadened our perspective on ARF function within the cell.
Collapse
Affiliation(s)
- J G Donaldson
- Cell Biology & Metabolism Branch, NICHD, National Institutes of Health, Bethesda, MD 20892
| | | |
Collapse
|
717
|
Wang X, Xu L, Zheng L. Cloning and expression of phosphatidylcholine-hydrolyzing phospholipase D from Ricinus communis L. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)31993-2] [Citation(s) in RCA: 137] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
|
718
|
Fensome A, Cunningham E, Troung O, Cockcroft S. ARF1(2-17) does not specifically interact with ARF1-dependent pathways. Inhibition by peptide of phospholipases C beta, D and exocytosis in HL60 cells. FEBS Lett 1994; 349:34-8. [PMID: 8045298 DOI: 10.1016/0014-5793(94)00634-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The small GTP-binding protein ARF has been shown recently to regulate phospholipase D (PLD). In order to investigate the role of ARF proteins in regulated exocytosis, we have used the N-terminal peptide ARF1(2-17) of the ARF1 protein. ARF1 reconstituted PLD activity in cytosol-depleted HL60 cells was inhibited by ARF1(2-17). In the presence of endogenous cytosol, ARF1(2-17) also inhibited GTP-gamma-S-stimulated PLD activity and exocytosis. Mastoparan Politses jadwagae and mastoparan Vespula lewisii which exhibit similar structural properties to ARF1(2-17) also inhibited GTP-gamma-S-stimulated PLD and exocytosis. GTP-gamma-S-stimulated phospholipase C-beta (PLC-beta) was also inhibited by ARF(2-17) and mastoparan. In cytosol-depleted HL60 cells, the ARF(2-17) inhibited the reconstitution of GTP-gamma-S-stimulated PLC-beta activity with exogenously-added PLC-beta 1 and phosphatidylinositol transfer protein. We conclude that the widely-used ARF1(2-17) peptide inhibits both ARF-independent (i.e. PLC-beta) and ARF-dependent pathways (i.e. PLD) and therefore cannot be regarded as a specific inhibitor of ARF function.
Collapse
Affiliation(s)
- A Fensome
- Department of Physiology, University College London, UK
| | | | | | | |
Collapse
|
719
|
Abstract
v-Src-induced increases in diglyceride are derived from phosphatidylcholine via a type D phospholipase (PLD) and a phosphatidic acid phosphatase. v-Src-induced PLD activity, as measured by PLD-catalyzed transphosphatidylation of phosphatidylcholine to phosphatidylethanol, is inhibited by GDP beta S, which inhibits G-protein-mediated intracellular signals. Similarly, v-Src-induced increases in diglyceride are also blocked by GDP beta S. In contrast to the PLD activity induced by v-Src, PLD activity induced by the protein kinase C agonist, 12-O-tetradecanoylphorbol-13-acetate (TPA), was insensitive to GDP beta S. Consistent with the involvement of a G protein in the activation of PLD activity by v-Src, GTP gamma S, a nonhydrolyzable analog of GTP that potentiates G-protein-mediated signals, strongly enhanced PLD activity in v-Src-transformed cells relative to that in parental BALB/c 3T3 cells. The effect of GTP gamma S on PLD activity in v-Src-transformed cells was observed only when cells were prelabeled with [3H]myristate, which is incorporated exclusively into phosphatidylcholine, the substrate for the v-Src-induced PLD. There was no difference in the effect of GTP gamma S-induced PLD activity on v-Src-transformed and BALB/c 3T3 cells when the cells were prelabeled with [3H]arachidonate, which is not incorporated into phospholipids that are substrates for the v-Src-induced PLD. Similarly, GDP beta S inhibited PLD activity in v-Src-transformed cells much more strongly than in BALB/c 3T3 cells when [3H]myristate was used to prelabel the cells. The GTP-dependent activation of PLD by v-Src was dependent upon the presence of ATP but was unaffected by either cholera or pertussis toxin. These data suggest that v-Src induces PLD activity through a phosphorylation event and is mediated by a cholera and pertussis toxin-insensitive G protein.
Collapse
|
720
|
|
721
|
Jiang H, Alexandropoulos K, Song J, Foster DA. Evidence that v-Src-induced phospholipase D activity is mediated by a G protein. Mol Cell Biol 1994; 14:3676-82. [PMID: 8196611 PMCID: PMC358735 DOI: 10.1128/mcb.14.6.3676-3682.1994] [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: 01/29/2023] Open
Abstract
v-Src-induced increases in diglyceride are derived from phosphatidylcholine via a type D phospholipase (PLD) and a phosphatidic acid phosphatase. v-Src-induced PLD activity, as measured by PLD-catalyzed transphosphatidylation of phosphatidylcholine to phosphatidylethanol, is inhibited by GDP beta S, which inhibits G-protein-mediated intracellular signals. Similarly, v-Src-induced increases in diglyceride are also blocked by GDP beta S. In contrast to the PLD activity induced by v-Src, PLD activity induced by the protein kinase C agonist, 12-O-tetradecanoylphorbol-13-acetate (TPA), was insensitive to GDP beta S. Consistent with the involvement of a G protein in the activation of PLD activity by v-Src, GTP gamma S, a nonhydrolyzable analog of GTP that potentiates G-protein-mediated signals, strongly enhanced PLD activity in v-Src-transformed cells relative to that in parental BALB/c 3T3 cells. The effect of GTP gamma S on PLD activity in v-Src-transformed cells was observed only when cells were prelabeled with [3H]myristate, which is incorporated exclusively into phosphatidylcholine, the substrate for the v-Src-induced PLD. There was no difference in the effect of GTP gamma S-induced PLD activity on v-Src-transformed and BALB/c 3T3 cells when the cells were prelabeled with [3H]arachidonate, which is not incorporated into phospholipids that are substrates for the v-Src-induced PLD. Similarly, GDP beta S inhibited PLD activity in v-Src-transformed cells much more strongly than in BALB/c 3T3 cells when [3H]myristate was used to prelabel the cells. The GTP-dependent activation of PLD by v-Src was dependent upon the presence of ATP but was unaffected by either cholera or pertussis toxin. These data suggest that v-Src induces PLD activity through a phosphorylation event and is mediated by a cholera and pertussis toxin-insensitive G protein.
Collapse
Affiliation(s)
- H Jiang
- Institute for Biomolecular Structure and Function, Hunter College, City University of New York, New York 10021
| | | | | | | |
Collapse
|
722
|
Abstract
PC hydrolysis by PLA2, PLC or PLD is a widespread response elicited by most growth factors, cytokines, neurotransmitters, hormones and other extracellular signals. The mechanisms can involve G-proteins, PKC, Ca2+ and tyrosine kinase activities. Although an agonist-responsive cytosolic PLA2 has been purified, cloned and sequenced, the agonist-responsive form(s) of PC-PLC has not been identified and no form of PC-PLD has been purified or cloned. Regulation of PLA2 by Ca2+ and MAPK is well established and involves membrane translocation and phosphorylation, respectively. PKC regulation of the enzyme in intact cells is probably mediated by MAPK. The question of G-protein control of PLA2 remains controversial since the nature of the G-protein is unknown and it is not established that its interaction with the enzyme is direct or not. Growth factor regulation of PLA2 involves tyrosine kinase activity, but not necessarily PKC. It may be mediated by MAPK. The physiological significance of PLA2 activation is undoubtedly related to the release of AA for eicosanoid production, but the LPC formed may have actions also. There is much evidence that PKC regulates PC-PLC and PC-PLD and this is probably a major mechanism by which agonists that promote PI hydrolysis secondarily activate PC hydrolysis. Since no agonist-responsive forms of either phospholipase have been isolated, it is not clear that PKC exerts its effects directly on the enzymes. Although it is assumed that a phosphorylation mechanism is involved, this may not be the case, and regulation may be by protein-protein interactions. G-protein control of PC-PLD is well-established, although, again, it has not been demonstrated that this is direct, and the nature of the G-protein(s) involved is unknown. In some cell types, there is evidence of the participation of a soluble protein, which may be a low Mr GTP-binding protein. What role this plays in the activation of PC-PLD is obscure. Agonist activation of PC hydrolysis in cells is usually Ca(2+)-dependent, but the step at which Ca2+ is involved is unclear, since PC-PLD and PC-PLC per se are not influenced by physiological concentrations of the ion. Most growth factors promote PC hydrolysis and this is mainly due to activation of PKC as a result of PI breakdown. However, in some cases, PC breakdown occurs in the absence of PI hydrolysis, implying another mechanism that does not involve PI-derived DAG.(ABSTRACT TRUNCATED AT 400 WORDS)
Collapse
Affiliation(s)
- J H Exton
- Howard Hughes Medical Institute, Nashville, TN
| |
Collapse
|
723
|
Type I phosphatidylinositol 4-phosphate 5-kinase isoforms are specifically stimulated by phosphatidic acid. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(19)78159-9] [Citation(s) in RCA: 332] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
|
724
|
Randazzo P, Kahn R. GTP hydrolysis by ADP-ribosylation factor is dependent on both an ADP-ribosylation factor GTPase-activating protein and acid phospholipids. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)34124-8] [Citation(s) in RCA: 153] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
|
725
|
Abstract
Significant advances have been made recently concerning mechanisms involved in the regulation of cell calcium levels. The mechanisms and physiological significance of agonist-induced phosphatidylcholine hydrolysis are also becoming clearer.
Collapse
Affiliation(s)
- J H Exton
- Howard Hughes Medical Institute, Vanderbilt University School of Medicine, Nashville, TN 37232
| |
Collapse
|
726
|
Zhang CJ, Rosenwald AG, Willingham MC, Skuntz S, Clark J, Kahn RA. Expression of a dominant allele of human ARF1 inhibits membrane traffic in vivo. J Biophys Biochem Cytol 1994; 124:289-300. [PMID: 8294513 PMCID: PMC2119943 DOI: 10.1083/jcb.124.3.289] [Citation(s) in RCA: 164] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
ADP-ribosylation factor (ARF) proteins and inhibitory peptides derived from ARFs have demonstrated activities in a number of in vitro assays that measure ER-to-Golgi and intra-Golgi transport and endosome fusion. To better understand the roles of ARF proteins in vivo, stable cell lines were obtained from normal rat kidney (NRK) cells transfected with either wild-type or a dominant activating allele ([Q71L]) of the human ARF1 gene under the control of the interferon-inducible mouse Mx1 promoter. Upon addition of interferon, expression of ARF1 proteins increased with a half-time of 7-8 h, as determined by immunoblot analysis. Induction of mutant ARF1, but not wild-type ARF1, led to an inhibition of protein secretion with kinetics similar to that observed for induction of protein expression. Examination of the Golgi apparatus and the ER by indirect immunofluorescence or transmission electron microscopy revealed that expression of low levels of mutant ARF1 protein correlated with a dramatic increase in vesiculation of the Golgi apparatus and expansion of the ER lumen, while expression of substantially higher levels of wild-type ARF1 had no discernible effect. Endocytosis was also inhibited by expression of mutant ARF1, but not by the wild-type protein. Finally, the expression of [Q71L]ARF1, but not wild-type ARF1, antagonized the actions of brefeldin A, as determined by the delayed loss of ARF and beta-COP from Golgi membranes and disruption of the Golgi apparatus. General models for the actions of ARF1 in membrane traffic events are discussed.
Collapse
Affiliation(s)
- C J Zhang
- Laboratory of Biological Chemistry, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892
| | | | | | | | | | | |
Collapse
|
727
|
Taylor TC, Kanstein M, Weidman P, Melançon P. Cytosolic ARFs are required for vesicle formation but not for cell-free intra-Golgi transport: evidence for coated vesicle-independent transport. Mol Biol Cell 1994; 5:237-52. [PMID: 8019009 PMCID: PMC301029 DOI: 10.1091/mbc.5.2.237] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
We investigated the role of ADP-ribosylation factors (ARFs) in Golgi function using biochemical and morphological cell-free assays. An ARF-free cytosol produced from soluble Chinese hamster ovary (CHO) extracts supports intra-Golgi transport by a mechanism that is biochemically indistinguishable from control transport reactions: ARF-free transport reactions are NSF-dependent, remain sensitive to the donor Golgi-specific inhibitor ilimaquinone, and exhibit kinetics that are identical to that of control reactions containing ARFs. In contrast, ARF-free cytosol does not support the formation of coated vesicles on Golgi cisternae. However, vesicle formation is reconstituted upon the addition of ARF1. These data suggest that neither soluble ARFs nor coated vesicle formation are essential for transport. We conclude that cell-free intra-Golgi transport proceeds via a coated vesicle-independent mechanism regardless of vesicle formation on Golgi cisternae.
Collapse
Affiliation(s)
- T C Taylor
- Department of Chemistry and Biochemistry, University of Colorado, Boulder 80303-0215
| | | | | | | |
Collapse
|
728
|
Bolander FF. Calcium, Calmodulin, and Phospholipids. Mol Endocrinol 1994. [DOI: 10.1016/b978-0-12-111231-8.50014-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
|
729
|
Bolander FF. G Proteins and Cyclic Nucleotides. Mol Endocrinol 1994. [DOI: 10.1016/b978-0-12-111231-8.50013-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
|
730
|
Affiliation(s)
- R A Kahn
- Laboratory of Biological Chemistry, National Cancer Institute, Bethesda, Maryland 20892
| | | | | |
Collapse
|