Rinken A, Terasmaa A, Raidaru G, Fuxe K
Institute of Chemical Physics, University of Tartu, Jakobi Street 2, EE-51 014, Tartu, Estonia.
Neurosci Lett. 2001 Apr 13;302(1):5-8. doi: 10.1016/s0304-3940(01)01568-3.
The cross regulation of agonist binding to D2 dopamine receptors and guanosine nucleotide binding to G proteins was studied using membranes of Chinese hamster ovary cells expressing rat D2short dopamine receptors. All guanosine nucleotides studied caused a concentration-dependent loss of high-affinity agonist binding sites of D2 receptors with potencies corresponding to their affinity to bind to G proteins in these membranes. On the other hand, the dopaminergic agonists, but not antagonists, decreased the affinities of guanosine diphosphate and guanosine monophosphate, but not of guanosine 5'-(gamma-thiotriphosphate). The cross regulation of ligand binding to D2 dopamine receptors and G proteins suggests the existence of several conformational states of these proteins during the signal transduction and that the high-affinity state of agonist binding is a transient state of the agonist-receptor-G protein complex, where no nucleotides are bound.
