scholarly journals Suppression of Giα2 enhances phospholipase C signalling

1994 ◽  
Vol 299 (3) ◽  
pp. 593-596 ◽  
Author(s):  
D C Watkins ◽  
C M Moxham ◽  
A J Morris ◽  
C C Malbon
Keyword(s):  
Adenylate Cyclase ◽  
Phospholipase C ◽  
G Proteins ◽  
Antisense Rna ◽  
Signalling Pathways ◽  
Surface Receptors ◽  
Inositol 1,4,5 Trisphosphate ◽  
F9 Teratocarcinoma ◽  
First Time

G-proteins mediate transmembrane signalling from a populous group of cell-surface receptors to a smaller group of effectors that includes adenylate cyclase, various ion channels and phospholipase C. Stem cells (F9 teratocarcinoma) or rat osteosarcoma 17/2.8 cells in which Gi alpha 2 expression is abolished by antisense RNA display markedly elevated basal inositol 1,4,5-trisphosphate accumulation and a potentiated phospholipase C response to stimulatory hormones. Expression of the Q205L mutant of Gi alpha 2, which is constitutively active, was found to block persistently hormonally stimulated phospholipase C activity, implicating Gi alpha 2 as an inhibitory regulator of phospholipase C signalling. Analysis using Gi alpha 2-deficient adipocytes of transgenic mice provided further evidence for a role for Gi alpha 2 in phospholipase C regulation, demonstrating in vivo that loss of Gi alpha 2 elevates basal, and markedly potentiates hormonally stimulated, phospholipase C activity. This report demonstrates for the first time that a single G-protein, G12, can regulate two distinct signalling pathways, i.e. adenylate cyclase and phospholipase C.

Dual Regulation of Phospolipase C Activity by G Proteins

Physiology ◽  
1993 ◽  
Vol 8 (2) ◽  
pp. 61-63
Author(s):  
H Deckmyn ◽  
C Van Geet ◽  
J Vermylen
Keyword(s):  
Adenylate Cyclase ◽  
Phospholipase C ◽  
G Protein ◽  
G Proteins ◽  
Pertussis Toxin ◽  
Inhibitory Pathway ◽  
Close Parallelism

Some subtypes of phosphatidylinositide-specific phospholipase C (PLC) are activated via pertussis toxin-sensitive or -insensitive G proteins. However, a G protein-dependent PLC inhibitory pathway also may exist. The resultant picture is of dual regulation of PLC, showing a close parallelism with the dual regulation of adenylate cyclase.

scholarly journals Phospholipase C in Dictyostelium discoideum. Identification of stimulatory and inhibitory surface receptors and G-proteins

1994 ◽  
Vol 297 (1) ◽  
pp. 189-193 ◽  
Author(s):  
A A Bominaar ◽  
P J M Van Haastert
Keyword(s):  
Phospholipase C ◽  
G Protein ◽  
G Proteins ◽  
Alpha Subunit ◽  
Wild Type ◽  
Inhibitory Pathway ◽  
Surface Receptors ◽  
G Protein Alpha Subunit ◽  
Camp Receptor ◽  
Protein Alpha Subunit

A combined biochemical and genetic approach was used to show that phospholipase C in the cellular slime mould Dictyostelium is under dual regulation by the chemoattractant cyclic AMP (cAMP). This dual regulation involves stimulatory and inhibitory surface receptors and G-proteins. In wild-type cells both cAMP and guanosine 5′-[gamma-thio]triphosphate (GTP[S]) stimulated phospholipase C. In contrast, mutant fgd A, lacking the G-protein alpha-subunit G alpha 2, showed no stimulation by either cAMP or GTP[S], indicating that G alpha 2 is the stimulatory G-protein. In mutant fgd C cAMP did not stimulate phospholipase C, but stimulation by GTP[S] was normal, suggesting that the defect in this mutant is upstream of the stimulatory G alpha 2. Inhibition of phospholipase C was achieved in wild-type cells by the partial antagonist 3′-deoxy-3′-aminoadenosine 3′,5′-phosphate (3′NH-cAMP). This inhibition was no longer observed in transformed cell lines lacking either the surface cAMP receptor cAR1 or the G-protein alpha-subunit G alpha 1; in these cells the agonist cAMP still activated phospholipase C. These results indicate that Dictyostelium phospholipase C is regulated via a stimulatory and an inhibitory pathway. The inhibitory pathway is composed of the surface receptor cAR1 and the G-protein G1. The stimulatory pathway consists of an unknown cAMP receptor (possibly the fgd C gene product) and the G-protein G2.

scholarly journals G-proteins of fat-cells Role in hormonal regulation of intracellular inositol 1,4,5-trisphosphate

1986 ◽  
Vol 240 (1) ◽  
pp. 35-40 ◽  
Author(s):  
P J Rapiejko ◽  
J K Northup ◽  
T Evans ◽  
J E Brown ◽  
C C Malbon
Keyword(s):  
Adenylate Cyclase ◽  
G Proteins ◽  
Pertussis Toxin ◽  
Hormonal Regulation ◽  
Alpha Subunit ◽  
Fat Cells ◽  
Fat Cell ◽  
Alpha Subunits ◽  
Inositol 1,4,5 Trisphosphate ◽  
Rat Fat Cells

Pertussis toxin abolishes hormonal inhibition of adenylate cyclase, hormonal stimulation of inositol 1,4,5-trisphosphate accumulation in rat fat-cells, and catalyses the ADP-ribosylation of two peptides, of Mr 39,000 and 41,000 [Malbon, Rapiejko & Mangano (1985) J. Biol. Chem. 260, 2558-2564]. The 41,000-Mr peptide is the alpha-subunit of the G-protein, referred to as Gi, that is believed to mediate inhibitory control of adenylate cyclase by hormones. The nature of the 39,000-Mr substrate for pertussis toxin was investigated. The fat-cell 39,000-Mr peptide was compared structurally and immunologically with the alpha-subunits of two other G-proteins, Gt isolated from the rod outer segments of bovine retina and Go isolated from bovine brain. After radiolabelling in the presence of pertussis toxin and [32P]NAD+, the electrophoretic mobilities of the fat-cell 39,000-Mr peptide and the alpha-subunits of Go and Gt were nearly identical. Partial proteolysis of these ADP-ribosylated proteins generates peptide patterns that suggest the existence of a high degree of homology between the fat-cell 39,000-Mr peptide and the alpha-subunit of Go. Antisera raised against purified G-proteins and their subunits were used to probe immunoblots of purified Gt, Gi, Go, and fat-cell membrane proteins. Although recognizing the 36,000-Mr beta-subunit band of Gt, Gi, Go and a 36,000-Mr fat-cell peptide, antisera raised against Gt failed to recognize either the 39,000- or the 41,000-Mr peptides of fat-cells or the alpha-subunits of Go and Gi. Antisera raised against the alpha-subunit of Go, in contrast, recognized the 39,000-Mr peptide of rat fat-cells, but not the alpha-subunit of either Gi or Gt. These data establish the identity of Go, in addition to Gi, in fat-cell membranes and suggest the possibility that either Go or Gi alone, or both, may mediate hormonal regulation of adenylate cyclase and phospholipase C.

Modulation of phospholipase C pathway and level of Gq alpha/G11 alpha in rat myometrium during gestation

1996 ◽  
Vol 271 (3) ◽  
pp. C895-C904 ◽  
Author(s):  
S. Lajat ◽  
Z. Tanfin ◽  
G. Guillon ◽  
S. Harbon
Keyword(s):  
Phospholipase C ◽  
G Proteins ◽  
Pertussis Toxin ◽  
Inositol Phosphates ◽  
Receptor Activation ◽  
Similar Increase ◽  
Inositol 1,4,5 Trisphosphate ◽  
M3 Subtype ◽  
Subtype A ◽  
Stimulation Of

The regulation of the receptor-G protein-phospholipase C (PLC) cascade was investigated in rat myometrium at midgestation (day 12) and at term (day 21) comparatively to the estrogen-treated tissue (day 0). Carbachol-mediated generation of [3H]inositol phosphates was insensitive to pertussis toxin and was enhanced at days 12 and 21 two- and threefold, respectively, with no alteration of muscarinic sites (M3 subtype). A similar increase could be detected in the production of inositol 1,4,5-trisphosphate, indicating the stimulation of a PLC degrading phosphatidylinositol 4,5-bisphosphate. AlF4- also enhanced PLC activation during gestation, suggesting pregnancy-related regulations that bypass receptor activation. Immunoreactive G proteins, Gq alpha and G11 alpha, and PLC-beta 3 were detected in all myometrial preparations. The amount of PLC-beta 3 was similar in day 0 and day 21 myometrium, although decreasing by 75% at midgestation. Of significance was the increased amount of Gq alpha in day 12 and day 21 myometrium (3- and 2-fold, respectively) which coincided with the enhanced phosphoinositide breakdown. The upregulation of Gq alpha may contribute to the enhanced PLC activity during pregnancy and at term.

scholarly journals Sustained Platelet-Derived Growth Factor Receptor α Signaling in Osteoblasts Results in Craniosynostosis by Overactivating the Phospholipase C-γ Pathway

2008 ◽  
Vol 29 (3) ◽  
pp. 881-891 ◽  
Author(s):  
Anne Moenning ◽  
Richard Jäger ◽  
Angela Egert ◽  
Wolfram Kress ◽  
Eva Wardelmann ◽  
...  
Keyword(s):  
Growth Factor ◽  
Phospholipase C ◽  
Bone Matrix ◽  
Growth Factor Receptor ◽  
Specific Inhibitor ◽  
Platelet Derived Growth Factor ◽  
Cranial Sutures ◽  
First Time

ABSTRACT The development and growth of the skull is controlled by cranial sutures, which serve as growth centers for osteogenesis by providing a pool of osteoprogenitors. These osteoprogenitors undergo intramembranous ossification by direct differentiation into osteoblasts, which synthesize the components of the extracellular bone matrix. A dysregulation of osteoblast differentiation can lead to premature fusion of sutures, resulting in an abnormal skull shape, a disease called craniosynostosis. Although several genes could be linked to craniosynostosis, the mechanisms regulating cranial suture development remain largely elusive. We have established transgenic mice conditionally expressing an autoactivated platelet-derived growth factor receptor α (PDGFRα) in neural crest cells (NCCs) and their derivatives. In these mice, premature fusion of NCC-derived sutures occurred at early postnatal stages. In vivo and in vitro experiments demonstrated enhanced proliferation of osteoprogenitors and accelerated ossification of osteoblasts. Furthermore, in osteoblasts expressing the autoactivated receptor, we detected an upregulation of the phospholipase C-γ (PLC-γ) pathway. Treatment of differentiating osteoblasts with a PLC-γ-specific inhibitor prevented the mineralization of synthesized bone matrix. Thus, we show for the first time that PDGFRα signaling stimulates osteogenesis of NCC-derived osteoblasts by activating the PLC-γ pathway, suggesting an involvement of this pathway in the etiology of human craniosynostosis.

Formation and actions of calcium-mobilizing messenger, inositol 1,4,5-trisphosphate

1987 ◽  
Vol 252 (2) ◽  
pp. G149-G157 ◽  
Author(s):  
J. W. Putney
Keyword(s):  
Endoplasmic Reticulum ◽  
Phospholipase C ◽  
Surface Membrane ◽  
Membrane Receptors ◽  
Regulatory Proteins ◽  
Second Phase ◽  
Guanine Nucleotide ◽  
Specific Receptor ◽  
Surface Receptors ◽  
Inositol 1,4,5 Trisphosphate

A variety of surface membrane receptors can activate a phospholipase C, which degrades phosphatidylinositol 4,5-bisphosphate liberating a calcium mobilizing second messenger, inositol 1,4,5-trisphosphate [(1,4,5)IP3]. The coupling of surface receptors to the phospholipase C involves one or more guanine nucleotide-dependent regulatory proteins that are similar but not identical to those that regulate adenylate cyclase. (1,4,5)IP3 has been shown to release Ca2+ from a portion of the endoplasmic reticulum and is believed responsible for the initial phase of Ca2+ mobilization ascribed to internal Ca2+ release. (1,4,5)IP3 acts by binding to a specific receptor that either is a component of, or regulates, a Ca2+ ion channel. The release of Ca2+ from the (1,4,5)IP3-sensitive component of the endoplasmic reticulum may secondarily activate the second phase of Ca2+ mobilization, which involves Ca2+ entry. (1,4,5)IP3 is metabolized by two pathways. One involves the action of a 5-phosphatase that degrades (1,4,5)IP3 to inositol 1,4-bisphosphate, whereas the other involves a 3-kinase that phosphorylates (1,4,5)IP3 to produce inositol 1,3,4,5-tetrakisphosphate. The significance of this dual metabolism is not known, but it may be important in rapidly extinguishing the Ca2+-releasing activity (1,4,5)IP3.

Involvement of G proteins in the effect of carbachol and cholecystokinin in rat pancreatic islets

1996 ◽  
Vol 271 (1) ◽  
pp. E65-E72 ◽  
Author(s):  
E. J. Verspohl ◽  
K. Herrmann
Keyword(s):  
Pancreatic Islets ◽  
Phospholipase C ◽  
G Protein ◽  
G Proteins ◽  
Insulin Release ◽  
Rat Pancreatic Islets ◽  
Inositol 1,4,5 Trisphosphate ◽  
Insulinotropic Effect ◽  
Gamma S

Phospholipase C is involved in the insulinotropic effect of carbachol (CCh) and cholecystokinin octapeptide (CCK-8). The involvement of the type of G protein was investigated in rat pancreatic islets. Guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S; a nonhydrolyzable GTP analogue) increased insulin release in electrically permeabilized islets. Both CCh and CCK-8 increased the GTP gamma S effect indicative of an involvement of G proteins. Pretreatment of the islets with pertussis toxin (PT) impaired the CCh-induced insulin secretion in the presence of 3.0 mM glucose and inhibited the stimulatory CCh effect on inositol 1,4,5-trisphosphate (IP3) levels at low and high glucose. In contrast to CCh, the CCK-8 effect on both insulin release and IP3 levels of islets was not modified by a PT pretreatment at various glucose concentrations. Two types of experiments indicate the type of G protein involved: first, long-term agonistic stimulation by either CCh or CCK-8 led to a downregulation of alpha o and alpha q/11, respectively; second, introduction of specific anti-alpha o or -alpha q/11 antibodies into electrically permeabilized islets nearly completely abolished the effects of CCh and CCK-8, respectively. The data indicate that both CCh and CCK-8 act as insulinotropic agents via the phospholipase C system; in the effect of CCh the PT-sensitive alpha o and in the effect of CCK-8 the PT-insensitive alpha q/11 is involved.

scholarly journals Cross-talk between the ATP and ADP nucleotide receptor signalling pathways in glioma C6 cells.

2002 ◽  
Vol 49 (4) ◽  
pp. 877-889 ◽  
Author(s):  
Rafał Czajkowski ◽  
Jolanta Barańska
Keyword(s):  
Adenylyl Cyclase ◽  
Phospholipase C ◽  
Cross Talk ◽  
Present Status ◽  
P2y Receptors ◽  
Signalling Pathways ◽  
C6 Cells ◽  
Receptor Signalling ◽  
Glioma C6 ◽  
Inositol 1,4,5 Trisphosphate

In this review we summarize the present status of our knowledge on the enzymes involved in the extracellular metabolism of nucleotides and the receptors involved in nucleotide signalling. We focus on the mechanism of the ATP and ADP signalling pathways in glioma C6, representative of the type of nonexcitable cells. In these cells, ATP acts on the P2Y(2) receptor coupled to phospholipase C, whereas ADP on two distinct P2Y receptors: P2Y(1) and P2Y(12). The former is linked to phospholipase C and the latter is negatively coupled to adenylyl cyclase. The possible cross-talk between the ATP-, ADP- and adenosine-induced pathways, leading to simultaneous regulation of inositol 1,4,5-trisphosphate and cAMP mediated signalling, is discussed.

scholarly journals Effects of tiazofurin on guanine nucleotide binding regulatory proteins in HL-60 cells

Blood ◽  
1990 ◽  
Vol 75 (3) ◽  
pp. 583-588 ◽  
Author(s):  
SM Kharbanda ◽  
ML Sherman ◽  
DW Kufe
Keyword(s):  
Adenylate Cyclase ◽  
Phospholipase C ◽  
G Protein ◽  
G Proteins ◽  
Binding Sites ◽  
Nucleotide Binding ◽  
Membrane Receptors ◽  
Guanine Nucleotide ◽  
Guanine Nucleotide Binding ◽  
Stimulation Of

Abstract Guanine nucleotide binding proteins (G proteins) are regulatory molecules that couple membrane receptors to effector systems such as adenylate cyclase and phospholipase C. The alpha subunits of G proteins bind to guanosine 5′-diphosphate (GDP) in the unstimulated state and guanosine 5′ triphosphate (GTP) in the active state. Tiazofurin (2-beta- D-ribofuranosylthiazole-4-carboxamide), a specific inhibitor of inosine monophosphate (IMP) dehydrogenase, decreases guanylate synthesis from IMP in HL-60 promyelocytic leukemia cells and depletes intracellular guanine nucleotide pools. This study demonstrates that treatment of HL- 60 cells with tiazofurin is associated with a fourfold increase in membrane binding sites for the nonhydrolyzable analogue GDP beta S. This increase in binding sites was associated with a 3.2-fold decrease in GDP beta S binding affinity. Similar findings were obtained with GTP gamma S. These effects of tiazofurin treatment on guanine nucleotide binding were also associated with decreased adenosine diphosphate- ribosylation of specific G protein substrates by cholera and pertussis toxin. The results further demonstrate that tiazofurin treatment results in inhibition of G protein-mediated transmembrane signaling mechanisms. In this regard, stimulation of adenylate cyclase by prostaglandin E2 was inhibited by over 50% in tiazofurin-treated cells. Furthermore, tiazofurin treatment resulted in inhibition of N- formylmethionylleucylphenylalanine-induced stimulation of phospholipase C. Taken together, these results indicate that tiazofurin acts at least in part by inhibiting the ability of G proteins to function as transducers of intracellular signals.

Hormone signalling via G-protein: regulation of phosphatidylinositol 4,5-bisphosphate hydrolysis by G q

1992 ◽  
Vol 336 (1276) ◽  
pp. 35-42 ◽  
Keyword(s):  
Phospholipase C ◽  
G Protein ◽  
G Proteins ◽  
Regulatory Proteins ◽  
Affinity Reagents ◽  
Surface Receptors ◽  
New Class ◽  
Α Subunits ◽  
Hormone Signalling ◽  
G Protein Α Subunits

Heterotrimeric GTP-dependent regulatory proteins (G-proteins) mediate modulation by many cell surface receptors. Activation of the G-proteins promotes dissociation of their α and βγ subunits. The similarity of behaviour of βγ subunits derived from a variety of G-proteins has led to their use as affinity reagents for the analysis of the more unique a subunits. The evolution of these uses is presented. One of the more insightful results was the isolation of a new class of G -protein α subunits (the α q subfamily) which have been shown to regulate the activity of a phospholipase C (PLC) specific for phosphatidylinositols. The experimental evidence leading to this conclusion is discussed. The activation by α q increases the apparent V max of the β isoform of phosphatidylinositol-specific phospholipase C (PLCβ) and can be modulated by βγ subunits.

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