The effects of activators of G-proteins, mastoparan and compound 48/80, on the G-protein/adenylate cyclase system in cultured melanophores of the black-moor goldfish, Carassius auratus

1996 ◽  
Vol 166 (8) ◽  
pp. 467-472
Author(s):  
F. Morishita ◽  
A. Shimada ◽  
Y. Takeda ◽  
M. Fujimoto ◽  
H. Katayama ◽  
...  
Keyword(s):  
Adenylate Cyclase ◽  
G Protein ◽  
G Proteins ◽  
Carassius Auratus ◽  
Adenylate Cyclase System ◽  
Goldfish Carassius Auratus

Immunoprecipitation of a pertussis toxin substrate of the Go family from rat islets of Langerhans

1992 ◽  
Vol 12 (2) ◽  
pp. 95-100 ◽  
Author(s):  
Nicholas S. Berrow ◽  
Roger D. Hurst ◽  
Susan L. F. Chan ◽  
Noel G. Morgan
Keyword(s):  
Molecular Weight ◽  
Insulin Secretion ◽  
Adenylate Cyclase ◽  
G Protein ◽  
G Proteins ◽  
Islets Of Langerhans ◽  
Pertussis Toxin ◽  
Inhibitory Receptors ◽  
Rat Islets ◽  
Rat Islets Of Langerhans

Rat islets express a pertussis toxin sensitive G-protein involved in receptor-mediated inhibition of insulin secretion. This has been assumed previously to represent “Gi” which couples inhibitory receptors to adenylate cyclase. Incubation of islet G-proteins with32P-NAD and pertussis toxin resulted in the labelling of a band of molecular weight 40,000. This band was very broad and did not allow resolution of individual components. Incubation of the radiolabelled proteins with an anti-Go antiserum resulted in specific immunoprecipitation of a32P-labelled band. These results demonstrate that the complement of pertussis toxin sensitive G-proteins in rat islets includes Go.

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 Heparin and other polyanions uncouple α1-adrenoceptors from G-proteins

1991 ◽  
Vol 280 (3) ◽  
pp. 791-795 ◽  
Author(s):  
L L T Dasso ◽  
C W Taylor
Keyword(s):  
Adenylate Cyclase ◽  
G Protein ◽  
G Proteins ◽  
Alkaline Treatment ◽  
Receptor Activation ◽  
Maximal Effect ◽  
Intact Cells ◽  
High Affinity ◽  
Antagonist Binding ◽  
Coupling Mechanisms

Several polyanionic compounds antagonize the interaction between receptors and the G-proteins that regulate adenylate cyclase or K+ channels, possibly by binding to a basic stretch of the receptor that is proposed to mediate its interaction with the G-proteins. We have studied the effects of polyanions on the interaction between the liver alpha 1-adrenoceptor and the G-protein through which it stimulates polyphosphoinositide turnover. Heparin [concn. causing 50% of maximal effect (EC50) = 0.5 microM], Trypan Blue (EC50 7.1 microM) or suramin (EC50 2.1 microM) prevented formation of the high-affinity adrenaline-receptor-G-protein complex without affecting antagonist binding. After alkaline treatment of the membranes, previously reported to cause G-protein removal, binding of agonists was insensitive to both guanine nucleotides and heparin. We conclude that these polyanions uncouple the alpha 1-adrenoceptor from its G-protein, suggesting that similar coupling mechanisms may underlie receptor activation of the G-proteins that activate polyphosphoinositide hydrolysis and those that regulate adenylate cyclase. This action of heparin severely limits its utility as a selective antagonist of the Ins(1,4,5)P3 receptor in intact cells.

Visualizing Signal Transduction: Receptors, G-Proteins, and Adenylate Cyclases

1996 ◽  
Vol 91 (5) ◽  
pp. 527-537 ◽  
Author(s):  
Carmen W. Dessauer ◽  
Bruce A. Posner ◽  
Alfred G. Gilman
Keyword(s):  
Signal Transduction ◽  
Adenylate Cyclase ◽  
G Protein ◽  
G Proteins ◽  
Crystallographic Analysis ◽  
Α Subunit ◽  
Signalling Network ◽  
Great Insight ◽  
Guanine Nucleotide Binding ◽  
Retinal Cgmp Phosphodiesterase

1. The first glimpses of heterotrimeric G-proteins came with the discoveries of the ubiquitous adenylate cyclase activator, Gs, and the specialized retinal cGMP phosphodiesterase activator, Gt or transducin. The model that evolved for regulation of adenylate cyclase activity by G-proteins soon proved to be a general paradigm for a large number of signalling pathways. Although many different G-proteins interact with a diverse array of receptors and effectors, each is composed of a guanine-nucleotide-binding α-subunit and a tightly associated complex of a β- and a γ-subunit. 2. Receptors catalyse the activation of G-proteins by promoting exchange of GDP for GTP, while G-proteins catalyse their own deactivation as a result of their intrinsic GTPase activity. Crystallographic analysis has described several of the various conformational states that G-proteins undergo as they are activated and deactivated and has provided great insight into the kinetic models of G-protein-mediated signal transduction. 3. The regulation of adenylate cyclase has proven to be intriguing and complex. Gsα activates all forms of mammalian adenylate cyclase; other G-proteins (Gi, Go and Gz) inhibit certain isoforms of the enzyme. The discovery of new isoforms of adenylate cyclase has revealed synergistic and conditional mechanisms of regulation. These include activation or inhibition by the G-protein βγ-subunit complex, activation by Ca2+-calmodulin, and phosphorylation by protein kinases. The large number of receptors, G-proteins and adenylate cyclases provides a complex signalling network that integrates and interprets a multitude of convergent inputs.

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