Functional coupling of dopamine D2 and muscarinic cholinergic receptors to their respective G proteins assessed by agonist-induced activation of high-affinity GTPase activity in rat striatal membranes

1995 ◽  
Vol 50 (3) ◽  
pp. 325-335 ◽  
Author(s):  
Yuji Odagaki ◽  
Kjell Fuxe
Keyword(s):  
G Proteins ◽  
Cholinergic Receptors ◽  
Functional Coupling ◽  
Gtpase Activity ◽  
Muscarinic Cholinergic Receptors ◽  
High Affinity ◽  
Dopamine D2 ◽  
Muscarinic Cholinergic

Carbachol-induced down-regulation of high-affinity receptors for vasoactive intestinal peptide

1989 ◽  
Vol 257 (3) ◽  
pp. G402-G408
Author(s):  
M. Murakami ◽  
R. Vinayek ◽  
R. T. Jensen ◽  
J. D. Gardner
Keyword(s):  
Vasoactive Intestinal Peptide ◽  
Response Curve ◽  
Cholinergic Receptors ◽  
The Other ◽  
Tetraacetic Acid ◽  
Muscarinic Cholinergic Receptors ◽  
Pancreatic Acini ◽  
Vip Receptors ◽  
High Affinity ◽  
Muscarinic Cholinergic

When dispersed acini from guinea pig pancreas are first incubated with carbachol, the subsequent binding of 125I-vasoactive intestinal peptide (VIP) is inhibited during a second incubation. This inhibitory action of carbachol on binding of 125I-VIP depends on time, temperature, and the concentration of carbachol in the first incubation and can be blocked by atropine. First incubating acini with A23187, ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA), cholecystokinin octapeptide, bombesin, or 12-O-tetradecanoylphorbol-13-acetate does not alter binding of 125I-VIP. Adding EGTA to the first incubation medium abolishes the effect of carbachol on binding of 125I-VIP. In control acini or acini first incubated with carbachol, approximately half of the bound 125I-VIP can be stripped by acetic acid. 125I-VIP interacts with two distinct classes of receptors on pancreatic acini. One has a high affinity for VIP (Kd, 1 nM); the other has a low affinity for VIP (Kd, 2 microM). First incubating acini with carbachol decreases the number but not the affinity of high-affinity VIP receptors with no change in the number or affinity of low-affinity VIP receptors. Pancreatic acini possess two classes of muscarinic cholinergic receptors: one has a high affinity (Kd, 4 microM) and the other has a low affinity (Kd, 698 microM) for carbachol. The dose-response curve for carbachol-induced inhibition of binding of 125I-VIP and that for occupation of low-affinity muscarinic cholinergic receptors by carbachol are similar.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Further evidence that muscarinic cholinergic receptors of 1321N1 astrocytoma cells couple to a guanine nucleotide regulatory protein that is not Ni

1985 ◽  
Vol 229 (2) ◽  
pp. 539-544 ◽  
Author(s):  
M W Martin ◽  
T Evans ◽  
T K Harden
Keyword(s):  
Adenylate Cyclase ◽  
Regulatory Protein ◽  
Cholinergic Receptors ◽  
Guanine Nucleotide ◽  
Muscarinic Cholinergic Receptors ◽  
High Affinity ◽  
Astrocytoma Cells ◽  
A Cell ◽  
Muscarinic Cholinergic ◽  
Guanine Nucleotide Regulatory Protein

Inhibitory coupling of receptors to adenylate cyclase previously has been shown to be relatively sensitive to inactivation by alkylation with N-ethylmaleimide (NEM). Modification of the inhibitory guanine nucleotide regulatory protein, Ni, has been proposed to be responsible for this effect. The effects of NEM on GTP-sensitive binding of carbachol to muscarinic cholinergic receptors has been compared in a cell line (1321N1 human astrocytoma cells) in which these receptors stimulate phosphoinositide breakdown and in a cell line (NG108-15 neuroblastoma X glioma cells) in which activation of these receptors results in inhibition of adenylate cyclase. Pretreatment of membrane preparations from 1321N1 cells with NEM resulted in a concentration-dependent decrease in the extent of pertussis toxin-catalysed [32P]ADP-ribosylation of a 41 000 Da protein previously proposed to be the alpha subunit of Ni. Under conditions where 32P-labelling of Ni in 1321N1 membranes was reduced by NEM by 90%, no effect was observed on the extent of guanine nucleotide-sensitive high-affinity binding of carbachol to muscarinic cholinergic receptors. In contrast, treatment of NG108-15 membranes with NEM under the same conditions resulted in complete loss of high-affinity guanine nucleotide sensitive binding of carbachol. These results illustrate another difference between the muscarinic receptor population of these two cell lines, and support the previous proposal that muscarinic receptors of 1321N1 cells couple to a guanine nucleotide regulatory protein that is not Ni.

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