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The cytoplasmic tail of the D1A receptor subtype: identification of specific domains controlling dopamine cellular responsiveness
Author(s) -
Chaar Ziad Y.,
Jackson Adele,
Tiberi Mario
Publication year - 2001
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.1471-4159.2001.00648.x
Subject(s) - adenylyl cyclase , hek 293 cells , g protein coupled receptor , receptor , microbiology and biotechnology , agonist , biology , g protein , dopamine receptor , signal transduction , camp dependent pathway , biochemistry
In this study the rat D1A receptor (wild‐type, WT) and truncation mutants thereof, are utilized to delineate specific cytoplasmic tail (CT) domains responsible for regulating ligand binding and receptor‐mediated adenylyl cyclase activation. In human embryonic kidney (HEK) cells, all truncation mutants of the D1A receptor (Δ425, Δ379, Δ351) display cell surface localization and express at high but different receptor numbers. Binding studies suggest that residues located between Cys 351 and Asp 425 may serve to restrain the agonist binding conformation of the D1A receptor. This contention is supported by the observation that the constitutive activation of Δ351 is significantly increased in comparison with WT, Δ425 and Δ379. Furthermore, we demonstrate that the extent of dopamine‐mediated maximal activation of adenylyl cyclase is significantly augmented in cells expressing Δ351 when compared with WT or mutants harboring shorter truncations. These results suggest that in addition to restraining receptor conformation, determinants located downstream of Cys 351 may act as negative regulators of the G protein coupling efficiency and adenylyl cyclase activation. Interestingly, all truncated receptors used in the present study display a decrease in dopamine potency when compared with WT. We show that inhibition of protein kinase A (PKA) activity leads also to a reduction in dopamine potency in cells expressing WT but not Δ351 receptors. These results hint at a potential previously unanticipated role for PKA in facilitating D1A receptor coupling efficiency in HEK cells. Overall, the present study has uncovered specific CT domains involved in regulating discrete aspects of the D1A receptor signaling.