51
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Abstract
Findings from the last two years in signal transduction research, including the elucidation of the crystal structure of alpha1, the uncovering of multiple roles for lipidation, the mimicry of receptor action with peptides, and both the in vitro reconstitution of inhibition of adenylyl cyclase and the in cell reconstitution of receptor-G protein coupling in transient and stable expression studies, are integrated into a "current" view of the receptor --> G protein --> effector pathway. The question is raised whether receptor or betagamma is the nucleotide exchange factor, and the central participation of Mg2+ in G protein activation and the change in affinity of the G protein for Mg2+ during receptor-stimulated activation are stressed.
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Affiliation(s)
- L Birnbaumer
- Department of Cell Biology, Baylor College of Medicine, Houston, Texas 77030, USA
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52
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Motte S, Communi D, Pirotton S, Boeynaems JM. Involvement of multiple receptors in the actions of extracellular ATP: the example of vascular endothelial cells. Int J Biochem Cell Biol 1995; 27:1-7. [PMID: 7757878 DOI: 10.1016/1357-2725(94)00059-x] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The role of ATP and ADP as intercellular mediators is now well established. The presence of the nucleotides in extracellular fluids can result from several mechanisms: cell lysis, selective permeabilization of the plasma membrane and exocytosis of secretory vesicles, such as platelet dense bodies. Extracellular adenine nucleotides are rapidly degraded by ectonucleotidases expressed inter alia on the surface of endothelial cells. They act on cells via the family of P2 receptors which encompasses more than 5 subtypes, some of which have been cloned recently. The P2T, P2U and P2Y receptors belong to the superfamily of receptors coupled to G proteins, whereas the P2X receptor is a cation channel and the P2Z receptor a non-selective pore. ATP and ADP stimulate the endothelial production of prostacyclin (PGI2) and nitric oxide (NO), two vasodilators and inhibitors of platelet aggregation, via an increase in cytosolic Ca2+. This action of adenine nucleotides is believed to limit the extent of intravascular platelet aggregation and to help localize thrombus formation to areas of endothelial damage. The endothelial response to nucleotides is mediated by at least two distinct subtypes of P2 receptors, P2Y and P2U, both coupled to phospholipase C.
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Affiliation(s)
- S Motte
- Institute of Interdisciplinary Research, School of Medicine, Free University of Brussels, Belgium
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53
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Lee CW, Lee KH, Lee SB, Park D, Rhee SG. Regulation of phospholipase C-beta 4 by ribonucleotides and the alpha subunit of Gq. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(18)47252-3] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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54
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Banno Y, Okano Y, Nozawa Y. Thrombin-mediated phosphoinositide hydrolysis in Chinese hamster ovary cells overexpressing phospholipase C-delta 1. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)40758-7] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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55
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56
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Lima CD, Wang JC, Mondragón A. Three-dimensional structure of the 67K N-terminal fragment of E. coli DNA topoisomerase I. Nature 1994; 367:138-46. [PMID: 8114910 DOI: 10.1038/367138a0] [Citation(s) in RCA: 233] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The three-dimensional structure of the 67K amino-terminal fragment of Escherichia coli DNA topoisomerase I has been determined to 2.2 A resolution. The polypeptide folds in an unusual way to give four distinct domains enclosing a hole large enough to accommodate a double-stranded DNA. The active-site tyrosyl residue, which is involved in the transient breakage of a DNA strand and the formation of a covalent enzyme-DNA intermediate, is present at the interface of two domains. The structure suggests a plausible mechanism by which E. coli DNA topoisomerase I and other members of the same DNA topoisomerase subfamily could catalyse the passage of one DNA strand through a transient break in another strand.
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Affiliation(s)
- C D Lima
- Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, Evanston, Illinois 60208
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57
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Milligan G. Specificity and functional applications of antipeptide antisera which identify G-protein alpha subunits. Methods Enzymol 1994; 237:268-83. [PMID: 7935003 DOI: 10.1016/s0076-6879(94)37068-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- G Milligan
- Department of Biochemistry, University of Glasgow, Scotland, United Kingdom
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58
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Waldo GL, Boyer JL, Harden TK. Purification of phospholipase C-activating G protein, G11, from turkey erythrocytes. Methods Enzymol 1994; 237:182-91. [PMID: 7934996 DOI: 10.1016/s0076-6879(94)37062-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- G L Waldo
- Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill 27599
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59
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Waldo GL, Morris AJ, Harden TK. Purification of G-protein-regulated phospholipase C from turkey erythrocytes. Methods Enzymol 1994; 238:195-207. [PMID: 7799785 DOI: 10.1016/0076-6879(94)38017-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- G L Waldo
- Department of Pharmacology, School of Medicine, University of North Carolina at Chapel Hill 27599
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60
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Affiliation(s)
- P Gierschik
- Department of Pharmacology and Toxicology, University of Ulm, Germany
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61
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Hepler JR, Kozasa T, Gilman AG. Purification of recombinant Gq alpha, G11 alpha, and G16 alpha from Sf9 cells. Methods Enzymol 1994; 237:191-212. [PMID: 7934997 DOI: 10.1016/s0076-6879(94)37063-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- J R Hepler
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas 75235
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62
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Selective activation of phospholipase C by recombinant G-protein alpha- and beta gamma-subunits. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)42015-1] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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63
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Das T, Baek KJ, Gray C, Im MJ. Evidence that the Gh protein is a signal mediator from alpha 1-adrenoceptor to a phospholipase C. II. Purification and characterization of a Gh-coupled 69-kDa phospholipase C and reconstitution of alpha 1-adrenoceptor, Gh family, and phospholipase C. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(19)74262-8] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
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64
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Knezevic I, Borg C, Le Breton GC. Identification of Gq as one of the G-proteins which copurify with human platelet thromboxane A2/prostaglandin H2 receptors. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(19)74486-x] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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65
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66
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Schnabel P, Camps M, Carozzi A, Parker PJ, Gierschik P. Mutational analysis of phospholipase C-beta 2. Identification of regions required for membrane association and stimulation by guanine-nucleotide-binding protein beta gamma subunits. EUROPEAN JOURNAL OF BIOCHEMISTRY 1993; 217:1109-15. [PMID: 8223634 DOI: 10.1111/j.1432-1033.1993.tb18343.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Members of the beta isozyme subfamily of the phosphoinositide-specific phospholipases C (PLC beta) have recently been shown to be stimulated by both guanine-nucleotide-binding protein alpha and beta gamma subunits. The alpha subunits of the Gq class activate PLC beta isozymes in the order of PLC beta 1 > or = PLC beta 3 >> PLC beta 2, which is different from the order of PLC beta 3 > PLC beta 2 > PLC beta 1 for beta gamma subunit stimulation. The C-terminal region of PLC beta 1, in particular the sequence between Thr903 and Leu1142, has been shown to be involved in interacting with activated alpha q subunits and to contain a region required for efficient membrane association of PLC beta 1 [Park, D., Jhon, D.-Y., Lee, C.-W., Ryu, S. H. & Rhee, S. G. (1993) J. Biol. Chem. 268, 3710-3714, and Wu, D., Jiang, H., Katz, A. & Simon, M. I. (1993) J. Biol. Chem. 268, 3704-3709]. To examine the structure-function relationships of a PLC beta isozyme highly sensitive to beta gamma subunit stimulation, we have altered the cDNA of PLC beta 2 by site-directed mutagenesis and have examined the effects of these structural alterations on the functional properties of the mutant polypeptides. The results show that the C-terminal region of PLC beta 2 downstream of Phe818, which corresponds to Tyr816 of PLC beta 1, contains a region essential for membrane association, but is required neither for the interaction of PLC beta 2 with Ca2+ and the phospholipid substrate, nor for beta gamma subunit stimulation of PLC beta 2. These data suggest that PLC beta isozymes are activated by alpha q and beta gamma subunits via distinct domains.
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Affiliation(s)
- P Schnabel
- Molecular Pharmacology Division, German Cancer Research Center, Heidelberg
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67
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Tsunoda Y. Receptor-operated Ca2+ signaling and crosstalk in stimulus secretion coupling. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1154:105-56. [PMID: 8218335 DOI: 10.1016/0304-4157(93)90008-c] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
In the cells of higher eukaryotic organisms, there are several messenger pathways of intracellular signal transduction, such as the inositol 1,4,5-trisphosphate/Ca2+ signal, voltage-dependent and -independent Ca2+ channels, adenylate cyclase/cyclic adenosine 3',5'-monophosphate, guanylate cyclase/cyclic guanosine 3',5'-monophosphate, diacylglycerol/protein kinase C, and growth factors/tyrosine kinase/tyrosine phosphatase. These pathways are present in different cell types and impinge on each other for the modulation of the cell function. Ca2+ is one of the most ubiquitous intracellular messengers mediating transcellular communication in a wide variety of cell types. Over the last decades it has become clear that the activation of many types of cells is accompanied by an increase in cytosolic free Ca2+ concentration ([Ca2+]i) that is thought to play an important part in the sequence of events occurring during cell activation. The Ca2+ signal can be divided into two categories: receptor- and voltage-operated Ca2+ signal. This review describes and integrates some recent views of receptor-operated Ca2+ signaling and crosstalk in the context of stimulus-secretion coupling.
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Affiliation(s)
- Y Tsunoda
- Department of Faculty Science, Hokkaido University, Sapporo, Japan
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68
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Lee C, Park D, Lee K, Kim C, Rhee S. Purification, molecular cloning, and sequencing of phospholipase C-beta 4. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(19)36926-1] [Citation(s) in RCA: 96] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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69
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Min DS, Kim Y, Lee YH, Suh PG, Ryu SH. A G-protein-coupled 130 kDa phospholipase C isozyme, PLC-beta 4, from the particulate fraction of bovine cerebellum. FEBS Lett 1993; 331:38-42. [PMID: 8405407 DOI: 10.1016/0014-5793(93)80293-4] [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: 01/30/2023]
Abstract
A 130 kDa PLC isozyme was purified from the particulate fraction of bovine cerebellum. This PLC was recognized by a polyclonal antiserum generated against the purified 97 kDa PLC-beta 4. Reconstitution of the purified 130 kDa PLC with the membranes of C6 Bu-1 cells in the presence of GTP gamma S or AlF4- resulted in PLC activation as well as the association of PLC with the membranes. Both the association and activation were revoked when the membrane was washed with 2 M KCl. The 97 kDa PLC-beta 4 did not associate with membranes. These data suggest that the 130 kDa PLC is the intact form of PLC-beta 4 the activity of which is likely to be regulated by a G-protein on the membrane.
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Affiliation(s)
- D S Min
- Department of Life Science, Pohang University of Science and Technology, South-Korea
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70
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Rooney T, Hager R, Stubbs C, Thomas A. Halothane regulates G-protein-dependent phospholipase C activity in turkey erythrocyte membranes. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)82292-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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71
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Cisar LA, Mochan E, Schimmel R. Interleukin-1 selectively potentiates bradykinin-stimulated arachidonic acid release from human synovial fibroblasts. Cell Signal 1993; 5:463-72. [PMID: 8373725 DOI: 10.1016/0898-6568(93)90086-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Exposure of human synovial fibroblasts prelabelled with [3H]arachidonic acid to bradykinin causes a rapid and sustained increase in arachidonic acid release, a transient increase in cytosolic calcium and an increase in radiolabelled diacylglycerol. Activation of arachidonic acid release by bradykinin was potentiated by interleukin-1 added either simultaneously with bradykinin or to cultures 24 h before addition of bradykinin. In contrast, interleukin-1 did not modify bradykinin-induced increases in cytosolic calcium or diacylglycerol. The stimulation of arachidonic acid release in response to bradykinin, in the absence or presence of interleukin-1, was not affected by RHC-80267, an inhibitor of diacylglycerol kinase, suggesting that deacylation of diacylglycerol was not an important pathway of arachidonic acid production in cultures exposed to bradykinin. This conclusion is supported by the observation that increased release of arachidonic acid was not accompanied by increased release of [14C]stearic acid in cultures labelled with both isotopes. Bradykinin-stimulated release of arachidonic acid was prevented by down-regulating protein kinase C by pretreatment with phorbol 12-myristate 13-acetate and was unaffected by inhibitors of protein synthesis actinomycin D or cycloheximide. On the other hand, interleukin-1 amplification of bradykinin-stimulated release of arachidonic acid was blocked by actinomycin D and cycloheximide. The results from this study point to activation of phospholipase A2 as the source of arachidonic acid in response to bradykinin. Our data further indicate that interleukin-1 selectively potentiates bradykinin activation of a phospholipase A2 by a mechanism requiring protein synthesis, but has no effect on bradykinin activation of phospholipase C.
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Affiliation(s)
- L A Cisar
- Department of Cell Biology, University of Medicine and Dentistry of New Jersey, School of Osteopathic Medicine, Stratford 08084
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72
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Fisher SK, McEwen E, Kunkle C, Thompson AK, Slowiejko D. Contribution of G protein activation to fluoride stimulation of phosphoinositide hydrolysis in human neuroblastoma cells. J Neurochem 1993; 60:1800-5. [PMID: 8386224 DOI: 10.1111/j.1471-4159.1993.tb13406.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
To examine the possibility that NaF enhances phosphoinositide-specific phospholipase C (PIC) activity in neural tissues by a mechanism independent of a guanine nucleotide binding protein (Gp), we have evaluated the contribution of Gp activation to NaF-stimulated phosphoinositide hydrolysis in human SK-N-SH neuroblastoma cells. Addition of NaF to intact cells resulted in an increase in the release of inositol phosphates (450% of control values; EC50 of approximately 8 mM). Inclusion of U-73122, an aminosteroid inhibitor of guanine nucleotide-regulated PIC activity in these cells, resulted in a dose-dependent inhibition of NaF-stimulated inositol lipid hydrolysis (IC50 of approximately 3.5 microM). When added to digitonin-permeabilized cells, NaF or guanosine-5'-O-thiotriphosphate (GTP gamma S) resulted in a three- and sevenfold enhancement, respectively, of inositol phosphate release. In the combined presence of optimal concentrations of NaF and GTP gamma S, inositol phosphate release was less than additive, indicative of a common site of action. Inclusion of 2-5 mM concentrations of guanosine-5'-O-(2-thiodiphosphate) (GDP beta S) fully blocked phosphoinositide hydrolysis elicited by GTP gamma S, whereas that induced by NaF was partially inhibited (65%). However, preincubation of the cells with GDP beta S resulted in a greater reduction in the ability of NaF to stimulate inositol phosphate release (87% inhibition). Both GTP gamma S and NaF-stimulated inositol phosphate release were inhibited by inclusion of 10 microM U-73122 (54-71%). The presence of either NaF or GTP gamma S also resulted in a marked lowering of the Ca2+ requirement for activation of PIC in permeabilized cells. These results indicate that in SK-N-SH cells, little evidence exists for direct stimulation of PIC by NaF and that the majority of inositol phosphate release that occurs in the presence of NaF can be attributed to activation of Gp.
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Affiliation(s)
- S K Fisher
- Neuroscience Laboratory, University of Michigan, Ann Arbor 48104-1687
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73
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74
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75
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Wu D, Jiang H, Katz A, Simon M. Identification of critical regions on phospholipase C-beta 1 required for activation by G-proteins. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)53750-9] [Citation(s) in RCA: 136] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
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76
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Park D, Jhon D, Lee C, Ryu S, Rhee S. Removal of the carboxyl-terminal region of phospholipase C-beta 1 by calpain abolishes activation by G alpha q. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)53751-0] [Citation(s) in RCA: 122] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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77
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Abstract
Specific phospholipase C enzymes can hydrolyse phosphatidylinositol 4,5-bisphosphate into two products: inositol 1,4,5-trisphosphate, which regulates the release of intracellular calcium stores, and diacylglycerol, which can stimulate protein kinase C. A new group of G proteins, the Gq subfamily, have recently been shown to mediate the regulation of this activity by a variety of hormones. How do different members of this family modulate unique phospholipase C isozymes? What is the mechanism of this regulation? How might the Gq subfamily act to modulate other important second messenger pathways? The tools to answer these questions are being rapidly developed.
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Affiliation(s)
- P C Sternweis
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas 75235
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78
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Boyer J, Waldo G, Harden T. Beta gamma-subunit activation of G-protein-regulated phospholipase C. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(19)74062-9] [Citation(s) in RCA: 141] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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79
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Aragay A, Katz A, Simon M. The G alpha q and G alpha 11 proteins couple the thyrotropin-releasing hormone receptor to phospholipase C in GH3 rat pituitary cells. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(19)73994-5] [Citation(s) in RCA: 82] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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80
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Wu D, Katz A, Lee C, Simon M. Activation of phospholipase C by alpha 1-adrenergic receptors is mediated by the alpha subunits of Gq family. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)35680-1] [Citation(s) in RCA: 130] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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81
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Vaziri C, Downes C. Association of a receptor and G-protein-regulated phospholipase C with the cytoskeleton. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)50043-0] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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82
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83
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Abstract
The family of heterotrimeric guanine nucleotide-binding regulatory proteins (G proteins) serves an essential role in transducing receptor-generated signals across the plasma membrane. Recent findings reveal unexpected functional roles for individual G protein subunits. Thus, GTP-binding alpha-subunits and the beta gamma-subunit complex can influence the activity of effector molecules independently or simultaneously, either synergistically or in opposition, to elicit a complex constellation of cellular events.
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Affiliation(s)
- J R Hepler
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas 75235
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84
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Park D, Jhon D, Kriz R, Knopf J, Rhee S. Cloning, sequencing, expression, and Gq-independent activation of phospholipase C-beta 2. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)41963-1] [Citation(s) in RCA: 86] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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85
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Camps M, Hou C, Sidiropoulos D, Stock JB, Jakobs KH, Gierschik P. Stimulation of phospholipase C by guanine-nucleotide-binding protein beta gamma subunits. EUROPEAN JOURNAL OF BIOCHEMISTRY 1992; 206:821-31. [PMID: 1606965 DOI: 10.1111/j.1432-1033.1992.tb16990.x] [Citation(s) in RCA: 241] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
We have previously shown that soluble fractions obtained from human HL-60 granulocytes contain a phospholipase C which is markedly stimulated by the stable GTP analogue guanosine 5'-[3-O-thio]triphosphate (Camps, M., Hou, C., Jakobs, K. H. and Gierschik, P. (1990) Biochem. J. 271, 743-748]. To investigate whether this stimulation was due to a soluble alpha subunit of a heterotrimeric guanine-nucleotide-binding protein or a soluble low-molecular-mass GTP-binding protein, we have examined the effect of purified guanine-nucleotide-binding protein beta gamma dimers on the phospholipase-C-mediated formation of inositol phosphates by HL-60 cytosol. We found that beta gamma subunits, purified from bovine retinal transducin (beta gamma t), markedly stimulated the hydrolysis of phosphatidylinositol 4,5-bisphosphate by this phospholipase C preparation. The stimulation of phospholipase C by beta gamma t was not secondary to a phospholipase-A2-mediated generation of arachidonic acid, was prevented by the GDP-liganded transducin alpha subunit and was additive to activation of phospholipase C by guanosine 5'-[3-O-thio]triphosphate. Beta gamma t also stimulated soluble phospholipase C from human and bovine peripheral neutrophils, as well as membrane-bound, detergent-solubilized phospholipase C from HL-60 cells. Stimulation of soluble HL-60 phospholipase C was not restricted to beta gamma t, but was also observed with highly purified beta gamma subunits from bovine brain. Fractionation of HL-60 cytosol by anion-exchange chromatography revealed the existence of at least two distinct forms of phospholipase C in HL-60 granulocytes. Only one of these forms was sensitive to stimulation by beta gamma t, demonstrating that stimulation of phospholipase C by beta gamma subunits is isozyme specific. Taken together, our results suggest that guanine-nucleotide-binding protein beta gamma subunits may play an important and active role in mediating the stimulation of phospholipase C by heterotrimeric guanine-nucleotide-binding proteins.
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Affiliation(s)
- M Camps
- Pharmakologisches Institut, Universität Heidelberg, Federal Republic of Germany
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86
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87
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Kontani K, Takahashi K, Inanobe A, Ui M, Katada T. Molecular heterogeneity of the beta gamma-subunits of GTP-binding proteins in bovine brain membranes. Arch Biochem Biophys 1992; 294:527-33. [PMID: 1567209 DOI: 10.1016/0003-9861(92)90720-h] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The guanine nucleotide-binding proteins (G proteins) are heterotrimers composed of alpha-, beta-, and gamma-subunits, and each of the constituent subunits has been reported to exhibit a molecular heterogeneity. The beta- and gamma-subunits form a functional unit that does not separate under physiological conditions and interact with various alpha-subunits that appear to mainly regulate specific effectors. We thus purified the beta gamma-complex of G proteins from bovine brain membranes and found that there were chromatographically multiple forms of beta gamma-subunits which could be reassociated with various alpha-subunits. The major findings observed with the purified proteins were summarized as follows. (a) The constituent beta gamma-subunits in the brain membrane G proteins appeared to be divided into two groups in their elution profiles from a hydrophobic column. (b) Each of the two groups contained at least five different components of beta gamma-subunits upon analyzing by a high-resolution, anion-exchange column. (c) Distribution of the heterogeneous beta gamma-subunits was not identical among various trimeric G proteins such as Gi, G0, and Gs. (d) The heterogeneous beta gamma-components were able to interact with a specific alpha-subunit resulting in the alpha beta gamma-trimer that served as the substrate of pertussis toxin-catalyzed ADP-ribosylation. (e) However, the apparent abilities of some beta gamma-subunits to support the toxin-induced modification were significantly different in a special comparison between the two beta gamma-groups that were eluted from the hydrophobic column. These results indicated that there were multiple forms of beta gamma-subunits associating with the specific alpha-subunit of a trimeric G protein and that some of those had different affinities for various alpha-subunits in terms of their tight associations. A possible role of the heterogeneity in beta gamma-subunits is also discussed in terms of G protein-mediated signal transductions.
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Affiliation(s)
- K Kontani
- Department of Life Science, Tokyo Institute of Technology, Yokohama, Japan
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88
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Berstein G, Blank J, Smrcka A, Higashijima T, Sternweis P, Exton J, Ross E. Reconstitution of agonist-stimulated phosphatidylinositol 4,5-bisphosphate hydrolysis using purified m1 muscarinic receptor, Gq/11, and phospholipase C-beta 1. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)42410-6] [Citation(s) in RCA: 152] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Wu DQ, Lee CH, Rhee SG, Simon MI. Activation of phospholipase C by the alpha subunits of the Gq and G11 proteins in transfected Cos-7 cells. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)46018-8] [Citation(s) in RCA: 242] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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Abstract
Phosphatidylinositol bisphosphate hydrolysis is an immediate response to many hormones, including growth factors. The hydrolysis of phosphatidylinositol bisphosphate is catalyzed by phosphatidylinositol-specific phospholipase C. A number of phospholipase C isozymes have been identified. Different isozymes are activated by different receptor classes. This review will summarize the different isozymes of phospholipase C, and the current knowledge of the mechanisms by which phospholipase C activity is modulated by growth factors.
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Affiliation(s)
- G Jones
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232-0146
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Gutowski S, Smrcka A, Nowak L, Wu D, Simon M, Sternweis P. Antibodies to the alpha q subfamily of guanine nucleotide-binding regulatory protein alpha subunits attenuate activation of phosphatidylinositol 4,5-bisphosphate hydrolysis by hormones. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)54955-3] [Citation(s) in RCA: 251] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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Ryoji M, Karpen J, Kaji A. Further characterization of ribosome releasing factor and evidence that it prevents ribosomes from reading through a termination codon. J Biol Chem 1981. [DOI: 10.1016/s0021-9258(19)69277-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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