D1 dopamine receptors can interact with both stimulatory and inhibitory guanine nucleotide binding proteins.
Pretreatment of striatal membranes with N-ethylmaleimide in the presence of a D1-specific agonist inactivated endogenous guanine nucleotide binding proteins (G proteins), but not D1 dopamine receptors, resulting in a loss of high-affinity agonist binding sites. Such D1 receptors were solubilized, mixed with exogenous G proteins from cells not containing D1 receptors, and reconstituted into phospholipid vesicles. These reconstituted receptors were able to couple to the exogenous G proteins, and the proportion of agonist high-affinity sites of the receptor (40-57%) was similar to levels obtained with naive receptors coupling to endogenous G proteins (40%) upon solubilization and reconstitution. These hybrid high-affinity sites were fully modulated by guanine nucleotides. Pretreatment of cells with pertussis toxin prior to extraction of G proteins resulted in a 50% decrease in the proportion of high-affinity sites; these sites remained sensitive to guanine nucleotides. When D1 receptors were reconstituted with extracts of cyc- cells, which lack stimulatory G proteins, the proportion of high-affinity sites was reduced to 31% of the total. Pertussis toxin treatment of the cyc- cells completely abolished the formation of high-affinity sites. These results demonstrate that D1-dopaminergic receptors are able to couple to not only stimulatory G proteins (Gs), but also to inhibitory G proteins (Gi).
Sidhu
A
A
Membrane Biochemistry Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland.
Sullivan
M
M
Kohout
T
T
Balen
P
P
Fishman
P H
PH
D000818:Animals; D002460:Cell Line; D019204:GTP-Binding Proteins / Q000378:metabolism* / Q000494:pharmacology; D006150:Guanine Nucleotides / Q000494:pharmacology; D006165:Guanylyl Imidodiphosphate / Q000494:pharmacology; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000378:metabolism*; D017447:Receptors, Dopamine D1
D006150:Guanine Nucleotides; D011954:Receptors, Dopamine; D017447:Receptors, Dopamine D1; D006165:Guanylyl Imidodiphosphate; D019204:GTP-Binding Proteins