Cyclic AMP regulation of messenger RNA level of the stimulatory GTP-binding protein Gsalpha. Isoproterenol, forskolin and 8-bromoadenosine 3':5'-cyclic monophosphate increase the level of Gsalpha mRNA in cultured astroglial cells

Luteinizing-hormone (LH)-stimulated cyclic AMP production in rat testis Leydig cells was desensitized by both LH and 12-O-tetradecanoylphorbol 13-acetate (TPA). However, TPA, but not LH, enhanced the subsequent response to cholera toxin. Treatment of the cells with pertussis toxin potentiated cyclic AMP production in both control and LH-desensitized cells, but did not potentiate further the responses obtained by TPA pretreatment. The results implicate the presence of an inhibitory GTP-binding protein (Gi), which may be inhibited by TPA. The presence of a Gi-like protein within the plasma membrane of Leydig cells was demonstrated by pertussis-toxin-catalysed [32P]ADP-ribosylation of a Mr-40000-41000 protein.

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Effects of phosphorylation of inhibitory GTP-binding protein by cyclic AMP-dependent protein kinase on its ADP-ribosylation by pertussis toxin, islet-activating protein

FEBS Letters ◽

10.1016/0014-5793(88)80058-9 ◽

1988 ◽

Vol 236 (2) ◽

pp. 372-374 ◽

Cited By ~ 36

Author(s):

Yasuhiro Watanabe ◽

Taro Imaizumi ◽

Naoyuki Misaki ◽

Katsuomi Iwakura ◽

Hiroshi Yoshida

Keyword(s):

Protein Kinase ◽

Cyclic Amp ◽

Pertussis Toxin ◽

Binding Protein ◽

Gtp Binding Protein ◽

Dependent Protein Kinase ◽

Adp Ribosylation ◽

Gtp Binding ◽

Dependent Protein

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The inhibitory GTP-binding protein (Gi) regulates the agonistic property of β-adrenergic ligands in isolated rat adipocytes. Evidence for a priming effect of cyclic AMP

Biochemical Journal ◽

10.1042/bj2880041 ◽

1992 ◽

Vol 288 (1) ◽

pp. 41-46 ◽

Cited By ~ 3

Author(s):

C Wesslau ◽

U Smith

Keyword(s):

Cyclic Amp ◽

Adenylate Cyclase ◽

Pertussis Toxin ◽

Priming Effect ◽

Binding Protein ◽

Gtp Binding Protein ◽

Rat Adipocytes ◽

Partial Agonists ◽

Gtp Binding ◽

Cellular Sensitivity

Prenalterol, an allegedly beta 1-selective adrenergic agonist with high intrinsic sympathomimetic activity (ISA), was shown to be weakly lipolytic in rat adipocytes. However, in pertussis-toxin-treated adipocytes, the ISA of prenalterol was markedly increased (from 10-20% to approx. 100% of that of isoprenaline). The cellular sensitivity was also increased (EC50 approx. 60 nM and approx. 3 microM in pertussis-toxin-treated and control cells respectively). A similar effect was seen for other partial agonists such as the beta 2-selective agonist terbutaline and for beta-adrenergic antagonists with some intrinsic activity (metoprolol, pindolol). There was no clear change in sensitivity to isoprenaline's ability to stimulate adenylate cyclase in adipocyte membranes from pertussis-toxin-treated animals but the cyclase activity was increased approx. 4-fold in the presence of 1 microM-GTP. Prenalterol stimulated lipolysis by only small increases in intracellular cyclic AMP (cAMP) levels (less than 10% of that seen with isoprenaline). Basal lipolysis was increased in cells from pertussis-toxin-treated rats and the cellular sensitivity to the non-degradable cAMP analogue, N6-monobutyryl-cAMP, was increased. In control cells, a submaximal concentration of prenalterol (0.1 microM) increased the sensitivity to the cAMP analogues, N6-monobutyryl-cAMP and 8-bromo-cAMP. A low concentration (1 mM) of 8-bromo-cAMP also increased the effect of prenalterol. Similar effects were seen when the phosphodiesterase was inhibited. Thus (1) lipolysis is extremely sensitive to small increases in intracellular cAMP; (2) the degree of activation of adenylate cyclase and thus cAMP formation is the rate-limiting step for the biological response of partial agonists; (3) the inhibitory GTP-binding protein, Gi, is an important modulator (‘tissue factor’) of the beta-adrenergic agonistic property; (4) low levels of cAMP exert a priming effect on protein kinase A.

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Phospttorylation of inhibitory GTP-binding protein by cyclic AMP-dependent protein kinase inhibits dissociation off the trimer into three subunits of the protein

European Journal of Pharmacology ◽

10.1016/0014-2999(90)93700-z ◽

1990 ◽

Vol 183 (6) ◽

pp. 2173-2174 ◽

Cited By ~ 1

Author(s):

Y. Watanabe ◽

T. Imaizumi ◽

N. Miki

Keyword(s):

Protein Kinase ◽

Cyclic Amp ◽

Binding Protein ◽

Gtp Binding Protein ◽

Dependent Protein Kinase ◽

Gtp Binding ◽

Dependent Protein

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Thrombin exerts a dual effect on stimulated adenylate cyclase in hamster fibroblasts, an inhibition via a GTP-binding protein and a potentiation via activation of protein kinase C

Biochemical Journal ◽

10.1042/bj2530711 ◽

1988 ◽

Vol 253 (3) ◽

pp. 711-719 ◽

Cited By ~ 51

Author(s):

I Magnaldo ◽

J Pouysségur ◽

S Paris

Keyword(s):

Protein Kinase C ◽

Protein Kinase ◽

Cyclic Amp ◽

Adenylate Cyclase ◽

Phospholipase C ◽

Pertussis Toxin ◽

Binding Protein ◽

Gtp Binding Protein ◽

Kinase C ◽

Gtp Binding

Previous studies in Chinese-hamster fibroblasts (CCL39 line) indicate that an important signalling pathway involved in thrombin's mitogenicity is the activation of a phosphoinositide-specific phospholipase C, mediated by a pertussis-toxin-sensitive GTP-binding protein (Gp). The present studies examine the effects of thrombin on the adenylate cyclase system and the interactions between the two signal transduction pathways. We report that thrombin exerts two opposite effects on cyclic AMP accumulation stimulated by cholera toxin, forskolin or prostaglandin E1. (1) Low thrombin concentrations (below 0.1 nM) decrease cyclic AMP formation. A similar inhibition is induced by A1F4-, and both thrombin- and A1F4- –induced inhibitions are abolished by pertussis toxin. (2) Increasing thrombin concentration from 0.1 to 10 nM results in a progressive suppression of adenylate cyclase inhibition and in a marked enhancement of cyclic AMP formation in pertussis-toxin-treated cells. A similar stimulation is induced by an active phorbol ester, and thrombin-induced potentiation of adenylate cyclase is suppressed by down-regulation of protein kinase C. Therefore, we conclude that (1) the inhibitory effect of thrombin on adenylate cyclase is the direct consequence of the activation of a pertussis-toxin-sensitive inhibitory GTP-binding protein (Gi) possibly identical with Gp, and (2) the potentiating effect of thrombin on cyclic AMP formation is due to stimulation of protein kinase C, as an indirect consequence of Gp activation. Our results suggest that the target of protein kinase C is an element of the adenylate cyclase-stimulatory GTP-binding protein (Gs) complex. At low thrombin concentrations, activation of phospholipase C is greatly attenuated by increased cyclic AMP, leading to predominance of the Gi-mediated inhibition.

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Developmental expression of messenger RNA levels of the α subunit of the GTP-binding protein, Gz, in the mouse nervous system

Developmental Brain Research ◽

10.1016/s0165-3806(98)00020-0 ◽

1998 ◽

Vol 107 (2) ◽

pp. 247-253 ◽

Cited By ~ 8

Author(s):

Kim L Kelleher ◽

Klaus I Matthaei ◽

Kwong J Leck ◽

Ian A Hendry

Keyword(s):

Nervous System ◽

Messenger Rna ◽

Binding Protein ◽

Developmental Expression ◽

Gtp Binding Protein ◽

Α Subunit ◽

Gtp Binding ◽

Rna Levels

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Small GTP-binding Protein RalA Associates with Weibel-Palade Bodies in Endothelial Cells

Thrombosis and Haemostasis ◽

10.1055/s-0037-1614349 ◽

1999 ◽

Vol 82 (09) ◽

pp. 1177-1181 ◽

Cited By ~ 27

Author(s):

Hubert de Leeuw ◽

Pauline Wijers-Koster ◽

Jan van Mourik ◽

Jan Voorberg

Keyword(s):

Endothelial Cells ◽

Binding Proteins ◽

Binding Protein ◽

Control Release ◽

Small Gtpase ◽

Gtp Binding Protein ◽

Two Dimensional Gel Electrophoresis ◽

Gtp Binding Proteins ◽

Dense Granules ◽

Gtp Binding

SummaryIn endothelial cells von Willebrand factor (vWF) and P-selectin are stored in dense granules, so-called Weibel-Palade bodies. Upon stimulation of endothelial cells with a variety of agents including thrombin, these organelles fuse with the plasma membrane and release their content. Small GTP-binding proteins have been shown to control release from intracellular storage pools in a number of cells. In this study we have investigated whether small GTP-binding proteins are associated with Weibel-Palade bodies. We isolated Weibel-Palade bodies by centrifugation on two consecutive density gradients of Percoll. The dense fraction in which these subcellular organelles were highly enriched, was analysed by SDS-PAGE followed by GTP overlay. A distinct band with an apparent molecular weight of 28,000 was observed. Two-dimensional gel electrophoresis followed by GTP overlay revealed the presence of a single small GTP-binding protein with an isoelectric point of 7.1. A monoclonal antibody directed against RalA showed reactivity with the small GTP-binding protein present in subcellular fractions that contain Weibel-Palade bodies. The small GTPase RalA was previously identified on dense granules of platelets and on synaptic vesicles in nerve terminals. Our observations suggest that RalA serves a role in regulated exocytosis of Weibel-Palade bodies in endothelial cells.

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Rap1b Association with the Platelet Cytoskeleton Occurs in the Absence of Glycoproteins IIb/IIIa

Thrombosis and Haemostasis ◽

10.1055/s-0037-1615073 ◽

1998 ◽

Vol 79 (04) ◽

pp. 832-836 ◽

Cited By ~ 3

Author(s):

Thomas Fischer ◽

Christina Duffy ◽

Gilbert White

Keyword(s):

Molecular Weight ◽

Divalent Cation ◽

Binding Proteins ◽

Binding Protein ◽

Platelet Membrane ◽

Low Molecular Weight ◽

Membrane Glycoproteins ◽

Gtp Binding Protein ◽

Gtp Binding Proteins ◽

Gtp Binding

SummaryPlatelet membrane glycoproteins (GP) IIb/IIIa and rap1b, a 21 kDa GTP binding protein, associate with the triton-insoluble, activation-dependent platelet cytoskeleton with similar rates and divalent cation requirement. To examine the possibility that GPIIb/IIIa was required for rap1b association with the cytoskeleton, experiments were performed to determine if the two proteins were linked under various conditions. Chromatography of lysates from resting platelets on Sephacryl S-300 showed that GPIIb/IIIa and rap1b were well separated and distinct proteins. Immunoprecipitation of GPIIb/IIIa from lysates of resting platelets did not produce rap1b or other low molecular weight GTP binding proteins and immunoprecipitation of rap1b from lysates of resting platelets did not produce GPIIb/IIIa. Finally, rap1b was associated with the activation-dependent cytoskeleton of platelets from a patient with Glanzmann’s thrombasthenia who lacks surface expressed glycoproteins IIb and IIIa. Based on these findings, we conclude that no association between GPIIb/IIIa and rap1b is found in resting platelets and that rap1b association with the activation-dependent cytoskeleton is at least partly independent of GPIIb/IIIa.

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