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Inhibition of Adenylyl Cyclase Activity by a Homogeneous Population of Dopamine Receptors: Selective Blockade by Antisera Directed Against G i1 and/or G i2
Author(s) -
Izenwasser Sari,
Côté Thomas E.
Publication year - 1995
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1995.64041614.x
Subject(s) - adenylyl cyclase , dopamine , receptor , dopamine receptor d2 , g protein , pertussis toxin , dopamine receptor , adcy9 , medicine , endocrinology , biology , gs alpha subunit , population , chemistry , biochemistry , environmental health
The 7315c pituitary tumor cell expresses a homogeneous population of dopamine receptors that are functionally similar to brain dopamine D 2 receptors. [ 3 H]‐Sulpiride binding to 7315c cell homogenates was specific and saturable, and K i values for compounds to compete for these sites were highly correlated with values for the same compounds at D 2 receptors in brain. Dopamine maximally inhibited ∼65% of forskolin‐stimulated cyclase activity in cell membranes. Some D 2 agonists had lower efficacies, suggesting that some compounds are partial agonists at this receptor. Removal of GTP from the assay buffer or pretreatment of the tissue with pertussis toxin abolished the inhibition of adenylyl cyclase by dopamine. Immunodetection of most of the known Gα subunits revealed that G i1 , G i2 , G i3 , G o , G q , and G s are present in the 7315c membrane. Pretreatment with the AS antibody (which recognizes the C‐terminal regions of Gα i1 and Gα i2 ) significantly attenuated the inhibition of adenylyl cyclase activity by dopamine, whereas antibodies to C‐terminal regions of the other Gα subunits had no effect. These findings suggest that the dopamine D 2 receptor regulates cyclase inhibition predominantly via G i1 and/or G i2 and that the 7315c tumor cells provide a useful model for studying naturally expressed dopamine D 2 receptors in the absence of other dopamine receptor subtypes.