scholarly journals Guanine nucleotide binding protein involved in muscarinic responses in the pig coronary artery is insensitive to islet-activating protein

1986 ◽  
Vol 239 (3) ◽  
pp. 567-574 ◽  
Author(s):  
T Sasaguri ◽  
M Hirata ◽  
T Itoh ◽  
T Koga ◽  
H Kuriyama
Keyword(s):  
Coronary Artery ◽  
G Protein ◽  
Binding Protein ◽  
Protein S ◽  
Nucleotide Binding ◽  
Guanine Nucleotide ◽  
Guanine Nucleotide Binding Protein ◽  
Guanine Nucleotide Binding ◽  
Pig Coronary Artery ◽  
Nucleotide Binding Protein

In an attempt to identify the nature of guanine nucleotide binding protein(s) (G-protein) involved in the acetylcholine (ACh)-induced (muscarinic) response of pig coronary-artery smooth muscle, we studied the effect of ADP-ribosylation of specific membrane protein(s) catalysed by islet-activating protein (IAP; pertussis toxin). The ACh-stimulated and guanine nucleotide-dependent activities of phosphatidylinositol 4,5-bisphosphate (PIP2) phosphodiesterase (PDE), assessed by the production of inositol 1,4,5-trisphosphate (IP3) from exogenously applied PIP2, were not modified, in either IAP-treated or non-treated cell homogenates used as the enzyme source. In intact tissues, pretreatment with up to 100 ng of IAP/ml inhibited neither the ACh-induced decrease in the amount of inositol phospholipids nor the increase in the amounts of phosphatidic acid and of inositol phosphates. IAP treatment increased the amount of cyclic AMP accumulated by isoprenaline. These observations suggest that G-protein which couples the muscarinic receptor to PIP2-PDE is insensitive to IAP. Such being the case, the nature of this protein(s) probably differs from that required for the regulation of adenylate cyclase activities (Ni or Gi).

Guanine Nucleotide Binding Protein (G Protein), Gamma

2012 ◽  
pp. 831-831
Author(s):  
Thomas E. Meigs ◽  
Alex Lyakhovich ◽  
Hoon Shim ◽  
Ching-Kang Chen ◽  
Denis J. Dupré ◽  
...  
Keyword(s):  
G Protein ◽  
Binding Protein ◽  
Nucleotide Binding ◽  
Protein G ◽  
Guanine Nucleotide ◽  
Guanine Nucleotide Binding Protein ◽  
Guanine Nucleotide Binding ◽  
Nucleotide Binding Protein

scholarly journals Inhibition of subunit dissociation and release of the stimulatory G-protein, Gs, by βγ-subunits and somatostatin in S49 lymphoma cell membranes

1991 ◽  
Vol 280 (2) ◽  
pp. 303-307 ◽  
Author(s):  
L A Ransnäs ◽  
D Leiber ◽  
P A Insel
Keyword(s):  
Adenylate Cyclase ◽  
G Protein ◽  
Cell Membranes ◽  
Binding Protein ◽  
Nucleotide Binding ◽  
Guanine Nucleotide ◽  
Guanine Nucleotide Binding Protein ◽  
Subunit Dissociation ◽  
Guanine Nucleotide Binding ◽  
Nucleotide Binding Protein

We examined the interaction between the stimulatory guanine-nucleotide-binding protein, Gs, and the inhibitory guanine-nucleotide-binding protein, Gi, in cell membranes of S49 lymphoma cells. In these cells, beta-adrenergic receptors stimulate the activity of adenylate cyclase via Gs, whereas inhibition via somatostatin receptors is transduced by an inhibitory G-protein, Gi. Using an antibody that selectively recognizes alpha s, the monomeric, but not the heterotrimeric, alpha-subunit of Gs, we quantified the extent of dissociation of Gs in a competitive e.l.i.s.a. Incubation of S49-cell plasma membranes with 0.1 microM-isoprenaline, 100 microM free Mg2+ and 100 microM-GTP produced substantial subunit dissociation of Gs, which was reversible by addition of purified beta gamma-subunit dimer or somatostatin. Somatostatin produced an immediate (without a lag) time- and concentration-dependent decrease in the concentration of dissociated Gs (kinhib. for somatostatin = 51 +/- 12 nM) and in the activity of adenylate cyclase (kinhib. = 121 +/- 20 nM). By contrast, after addition of a 10-fold molar excess of beta gamma-dimer relative to alpha s, there was a 2-3 min lag, after which the beta gamma-dimer re-associated Gs. Isoprenaline-induced dissociation of Gs was accompanied by a release of alpha s from the incubated membranes to a post-100,000 g supernatant, and somatostatin could reverse this release. Immunoblot analysis with both a C-terminal anti-peptide antibody and an antibody directed against a sequence near the N-terminal also showed release of alpha s by the beta-agonist and reversal by somatostatin. Membrane release of Gs by isoprenaline that could be blocked by somatostatin was also confirmed in reconstitution studies of supernatant fraction into cyc- S49-cell membranes. We conclude that in native cell membranes somatostatin-induced activation of Gi dissociates Gi and interferes with the Gs activation cycle by providing beta gamma-dimer, which acts to prevent or reverse formation of monomeric alpha s. Because alpha s can be released from the cell membrane, regulation of the local concentration of GTP-liganded dissociated alpha s is likely to be an important factor in modulating the activity of adenylate cyclase.

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