Phospholipase D in rat myometrium: occurrence of a membrane-bound ARF6 (ADP-ribosylation factor 6)-regulated activity controlled by βγ subunits of heterotrimeric G-proteins

2000 ◽  
Vol 352 (2) ◽  
pp. 491-499 ◽  
Author(s):  
Hervé LE STUNFF ◽  
Lien DOKHAC ◽  
Sylvain BOURGOIN ◽  
Marie-France BADER ◽  
Simone HARBON
Keyword(s):  
G Protein ◽  
G Proteins ◽  
Ammonium Sulphate ◽  
Phospholipase D ◽  
Tyrosine Kinases ◽  
Glutathione S Transferase ◽  
Free System ◽  
Adp Ribosylation ◽  
A Cell ◽  
Membrane Bound

Both protein kinase C and protein tyrosine kinases have been shown to be involved in phospholipase D (PLD) activation in intact rat myometrium [Le Stunff, Dokhac and Harbon (2000) J. Pharmacol. Exp. Ther. 292, 629–637]. In this study we assessed the involvement of monomeric G-proteins in PLD activation in a cell-free system derived from myometrial tissue. Both the PLD1 and PLD2 isoforms were detected. Two forms of PLD activity, essentially membrane-bound, were found in myometrial preparations. One form was stimulated by oleate and insensitive to guanosine 5ƀ-[γ-thio] triphosphate (GTP[S]). The second required ammonium sulphate to be detected and was stimulated by GTP[S]. ADP-ribosylation factors (ARF1 and ARF6) and RhoA were immunodetected in myometrial preparations. ARF1 and RhoA were present in the membrane and cytosolic fractions whereas ARF6 was detected exclusively in the membrane fraction. A synthetic myristoylated peptide corresponding to the N-terminal domain of ARF6 [myrARF6(2–13)] totally abolished PLD activation in the presence of ammonium sulphate and GTP[S], whereas myrARF1(2–17) and the inhibitory GDP/GTP-exchange factor, Rho GDI, did not. These data are consistent with a membrane-bound ARF6-regulated PLD activity. Finally, the stimulation of PLD by ARF6 was inhibited by AlF-4 and this inhibition was counteracted by the fusion protein glutathione S-transferase-β-adrenergic receptor kinase 1 (495–689) and by the QEHA peptide (from adenylate cyclase ACII), which act as G-protein βγ-subunit scavengers. It is concluded that G-protein subunits βγ are involved in a pathway modulating PLD activation by ARF6, illustrating cross-talk between heterotrimeric and monomeric G-proteins.

scholarly journals Exocytosis in mast cells by basic secretagogues: evidence for direct activation of GTP-binding proteins.

1990 ◽  
Vol 111 (3) ◽  
pp. 909-917 ◽  
Author(s):  
M Aridor ◽  
L M Traub ◽  
R Sagi-Eisenberg
Keyword(s):  
Mast Cells ◽  
G Protein ◽  
G Proteins ◽  
Independent Manner ◽  
Histamine Secretion ◽  
Free System ◽  
Stimulatory G Protein ◽  
A Cell ◽  
Secretion Inhibition ◽  
Gamma S

Histamine release induced by the introduction of a nonhydrolyzable analogue of GTP, GTP-gamma-S, into ATP-permeabilized mast cells, is associated with phosphoinositide breakdown, as evidenced by the production of phosphatidic acid (PA) in a neomycin-sensitive process. The dependency of both PA formation and histamine secretion on GTP-gamma-S concentrations is bell shaped. Whereas concentrations of up to 0.1 mM GTP-gamma-S stimulate both processes, at higher concentrations the cells' responsiveness is inhibited. At a concentration of 1 mM, GTP-gamma-S self-inhibits both PA formation and histamine secretion. Inhibition of secretion can, however, be overcome by the basic secretagogues compound 48/80 and mastoparan that in suboptimal doses synergize with 1 mM GTP-gamma-S to potentiate secretion. Secretion under these conditions is not accompanied by PA formation and is resistant both to depletion of Ca2+ from internal stores and to pertussis toxin (PtX) treatment. In addition, 48/80, like mastoparan, is capable of directly stimulating the GTPase activity of G-proteins in a cell-free system. Together, our results are consistent with a model in which the continuous activation of a phosphoinositide-hydrolyzing phospholipase C (PLC) by a stimulatory G-protein suffices to trigger histamine secretion. Basic secretagogues of mast cells, such as compound 48/80 and mastoparan, are capable of inducing secretion in a mechanism that bypasses PLC by directly activating a G-protein that is presumably located downstream from PLC (GE). Thereby, these secretagogues induce histamine secretion in a receptor-independent manner.

Regulation of Rho protein binding to membranes by rhoGDI: inhibition of releasing activity by physiological ionic conditions

1999 ◽  
Vol 77 (1) ◽  
pp. 59-69 ◽  
Author(s):  
Diane Bilodeau ◽  
Sylvie Lamy ◽  
Richard R Desrosiers ◽  
Denis Gingras ◽  
Richard Béliveau
Keyword(s):  
Ionic Strength ◽  
Brush Border ◽  
Rat Kidney ◽  
Regulatory Protein ◽  
Rho Proteins ◽  
Glutathione S Transferase ◽  
Free System ◽  
Brush Border Membranes ◽  
A Cell ◽  
Membrane Bound

The Rho GDP dissociation inhibitor (GDI) is an ubiquitously expressed regulatory protein involved in the cycling of Rho proteins between membrane-bound and soluble forms. Here, we characterized the Rho solubilization activity of a glutathione S-transferase (GST) - GDI fusion protein in a cell-free system derived from rat kidney. Addition of GST-GDI to kidney brush border membranes resulted in the specific release of Cdc42 and RhoA from the membranes, while RhoB and Ras were not extracted. The release of Cdc42 and RhoA by GST-GDI was dose dependent and saturable with about 50% of both RhoA and Cdc42 extracted. The unextracted Rho proteins were tightly bound to membranes and could not be solubilized by repeated GST-GDI treatment. These results demonstrated that kidney brush border membranes contained two populations of RhoA and Cdc42. Furthermore, the GST-GDI solubilizing activity on membrane-bound Cdc42 and RhoA was abolished at physiological conditions of salt and temperature in all tissues examined. When using bead-immobilized GST-GDI, KCl did not reduced the binding of Rho proteins. However, washing brush border membranes with KCl prior treatment by GST-GDI inhibited the extraction of Rho proteins. Taken together, these results suggest that the binding of GDI to membrane-bound Cdc42 and RhoA occurs easily under physiological ionic strength conditions, but a complementary factor is required to extract these proteins from membranes. These observations suggest that the shuttling activity of GDI upon Rho proteins could be normally downregulated under physiological conditions.Key words: rhoGDI, rho proteins, ionic strength, kidney.

scholarly journals ELF-2, a new member of the Eph ligand family, is segmentally expressed in mouse embryos in the region of the hindbrain and newly forming somites.

1995 ◽  
Vol 15 (9) ◽  
pp. 4921-4929 ◽  
Author(s):  
A D Bergemann ◽  
H J Cheng ◽  
R Brambilla ◽  
R Klein ◽  
J G Flanagan
Keyword(s):  
Tyrosine Kinases ◽  
Dissociation Constants ◽  
Expression Patterns ◽  
Mouse Embryos ◽  
Eph Receptors ◽  
Vertebrate Development ◽  
Orphan Receptors ◽  
Free System ◽  
A Cell

The Eph receptors are the largest known family of receptor tyrosine kinases and are notable for distinctive expression patterns in the nervous system and in early vertebrate development. However, all were identified as orphan receptors, and only recently have there been descriptions of a corresponding family of ligands. We describe here a new member of the Eph ligand family, designated ELF-2 (Eph ligand family 2). The cDNA sequence for mouse ELF-2 indicates that it is a transmembrane ligand. It shows closest homology to the other known transmembrane ligand in the family, ELK-L/LERK-2/Cek5-L, with 57% identity in the extracellular domain. There is also striking homology in the cytoplasmic domain, including complete identity of the last 33 amino acids, suggesting intracellular interactions. On cell surfaces, and in a cell-free system, ELF-2 binds to three closely related Eph family receptors, Elk, Cek10 (apparent ortholog of Sek-4 and HEK2), and Cek5 (apparent ortholog of Nuk/Sek-3), all with dissociation constants of approximately 1 nM. In situ hybridization of mouse embryos shows ELF-2 RNA expression in a segmental pattern in the hindbrain region and the segmenting mesoderm. Comparable patterns have been described for Eph family receptors, including Sek-4 and Nuk/Sek-3, suggesting roles for ELF-2 in patterning these regions of the embryo.

Specific coupling of a cation-sensing receptor to G protein alpha-subunits in MDCK cells

1997 ◽  
Vol 273 (1) ◽  
pp. F129-F135 ◽  
Author(s):  
J. M. Arthur ◽  
G. P. Collinsworth ◽  
T. W. Gettys ◽  
L. D. Quarles ◽  
J. R. Raymond
Keyword(s):  
G Protein ◽  
G Proteins ◽  
Plasma Membranes ◽  
Mdck Cells ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Cellular Activation ◽  
Protein Activation ◽  
A Cell ◽  
Cation Sensing

Extracellular cations such as Ca2+ stimulate a G protein-coupled, cation-sensing receptor (CaR). We used microphysiometry to determine whether an extracellular cation-sensing mechanism exists in Madin-Darby canine kidney (MDCK) cells. The CaR agonists Ca2+ and Gd3+ caused cellular activation in a concentration-dependent manner. mRNA for the CaR was identified by reverse transcription and polymerase chain reaction (PCR) using nested CaR-specific primers, identification of an appropriately located restriction site, and sequencing of the subcloned fragment obtained by PCR. G protein activation was evaluated using the GTP photoaffinity label [alpha-32P]GTP azidoanalide (AA-GTP). After stimulation with Gd3+ and cross-linking, plasma membranes were solubilized and immunoprecipitated with antisera specific for Gq/11 alpha and Gi alpha family members. Gd3+ increased incorporation of AA-GTP into Gq/11 alpha precipitates by 146 +/- 48% and into G alpha i-2 and G alpha i-3 to a lesser extent but not into G alpha i-1. Direct effects of Gd3+ on the G proteins were ruled out using partially purified mammalian G proteins expressed in Escherichia coli or Sf9 cells. We conclude that MDCK cells possess a cell-surface CaR that activates Gq/11 alpha, G alpha i-2, and G alpha i-3 but not G alpha i-1.

Phospholipase D: enzymology, mechanisms of regulation, and function

1997 ◽  
Vol 77 (2) ◽  
pp. 303-320 ◽  
Author(s):  
J. H. Exton
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Phosphatidic Acid ◽  
G Protein ◽  
Phospholipase D ◽  
Tyrosine Kinases ◽  
Rho Proteins ◽  
Kinase C

Phospholipase D exists in various forms that differ in their regulation but predominantly hydrolyze phosphatidylcholine. The Ca(2+)-dependent isozymes of protein kinase C regulate phospholipase D in vitro and play a major role in its control by growth factors and G protein-linked agonists in vivo. Recent studies have demonstrated that small G proteins of the ADP-ribosylation factor (ARF) and Rho families activate the enzyme in vitro, and evidence is accumulating that they also are involved in its control in vivo. Both types of G protein play important roles in cellular function, and the possible mechanisms by which they are activated by agonists are discussed. There is also emerging evidence of the control of phospholipase D and Rho proteins by soluble tyrosine kinases and novel serine/threonine kinases. The possible role of these kinases in agonist regulation of phospholipase D is discussed. The function of phospholipase D in cells is still poorly defined. Postulated roles of phosphatidic acid produced by phospholipase D action include the activation of Ca(2+)-independent isoforms of protein kinase C, the regulation of growth and the cytoskeleton in fibroblasts, and control of the respiratory burst in neutrophils. Another important function of phosphatidic acid is to act as a substrate for a specific phospholipase A2 to generate lysophosphatidic acid, which is becoming increasingly recognized as a major intercellular messenger. Finally, it is possible that the phospholipid changes induced in various cellular membranes by phospholipase D may per se play an important role in vesicle trafficking and other membrane-associated events.

Characterization of phospholipase D in a cell-free system of cultured cells derived from rat frontal cortex

1992 ◽  
Vol 595 (1) ◽  
pp. 12-16 ◽  
Author(s):  
Akira Nishida ◽  
Masami Shimizu ◽  
Yasunori Kanaho ◽  
Yoshinori Nozawa ◽  
Shigeto Yamawaki
Keyword(s):  
Frontal Cortex ◽  
Phospholipase D ◽  
Cultured Cells ◽  
Free System ◽  
Cell Free System ◽  
A Cell ◽  
Rat Frontal Cortex

The properties of free and membrane bound polysomes studied in a cell free system of Bombix mori silkglands

FEBS Letters ◽  
1971 ◽  
Vol 13 (6) ◽  
pp. 321-324 ◽  
Author(s):  
J. Daillie ◽  
L. Grasset ◽  
J.-C. Beck ◽  
J.-P. Prudhomme ◽  
J.-P. Ebel
Keyword(s):  
Free System ◽  
Cell Free System ◽  
A Cell ◽  
Membrane Bound

scholarly journals A predictive computational model reveals that GIV/girdin serves as a tunable valve for EGFR-stimulated cyclic AMP signals

2019 ◽  
Vol 30 (13) ◽  
pp. 1621-1633 ◽  
Author(s):  
Michael Getz ◽  
Lee Swanson ◽  
Debashish Sahoo ◽  
Pradipta Ghosh ◽  
Padmini Rangamani
Keyword(s):  
Growth Factor ◽  
G Protein ◽  
G Proteins ◽  
Cross Talk ◽  
Tyrosine Kinases ◽  
Control Valve ◽  
Camp Signaling ◽  
Nucleotide Exchange ◽  
Camp Concentration ◽  
Camp Levels

Cellular levels of the versatile second messenger cyclic (c)AMP are regulated by the antagonistic actions of the canonical G protein → adenylyl cyclase pathway that is initiated by G-protein–coupled receptors (GPCRs) and attenuated by phosphodiesterases (PDEs). Dysregulated cAMP signaling drives many diseases; for example, its low levels facilitate numerous sinister properties of cancer cells. Recently, an alternative paradigm for cAMP signaling has emerged in which growth factor–receptor tyrosine kinases (RTKs; e.g., EGFR) access and modulate G proteins via a cytosolic guanine-nucleotide exchange modulator (GEM), GIV/girdin; dysregulation of this pathway is frequently encountered in cancers. In this study, we present a network-based compartmental model for the paradigm of GEM-facilitated cross-talk between RTKs and G proteins and how that impacts cellular cAMP. Our model predicts that cross-talk between GIV, G αs, and G αi proteins dampens ligand-stimulated cAMP dynamics. This prediction was experimentally verified by measuring cAMP levels in cells under different conditions. We further predict that the direct proportionality of cAMP concentration as a function of receptor number and the inverse proportionality of cAMP concentration as a function of PDE concentration are both altered by GIV levels. Taking these results together, our model reveals that GIV acts as a tunable control valve that regulates cAMP flux after growth factor stimulation. For a given stimulus, when GIV levels are high, cAMP levels are low, and vice versa. In doing so, GIV modulates cAMP via mechanisms distinct from the two most often targeted classes of cAMP modulators, GPCRs and PDEs.

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