Resistance of the dopamine D4 receptor to agonist-induced internalization and degradation.
Dopamine receptors are G-protein-coupled receptors involved in the control of motivation, learning, and fine-tuning of motor movement, as well as modulation of neuroendocrine signalling. Stimulation of G-protein-coupled receptors normally results in attenuation of signalling through desensitization, followed by internalization and down-regulation of the receptor. These processes allow the cell to regain homeostasis after exposure to extracellular stimuli and offer protection against excessive signalling. Here, we have investigated the agonist-mediated attenuation properties of the dopamine D4 receptor. We found that several hallmarks of signal attenuation such as receptor phosphorylation, internalization and degradation showed a blunted response to agonist treatment. Moreover, we did not observe recruitment of beta-arrestins upon D4 receptor stimulation. We also provide evidence for the constitutive phosphorylation of two serine residues in the third intracellular loop of the D4 receptor. These data demonstrate that, when expressed in CHO, HeLa and HEK293 cells, the human D4 receptor shows resistance to agonist-mediated internalization and down-regulation. Data from neuronal cell lines, which have been reported to show low endogenous D4 receptor expression, such as the hippocampal cell line HT22 and primary rat hippocampal cells, further support these observations.
Spooren
Anneleen
A
Laboratory of Eukaryotic Gene Expression and Signal Transduction (LEGEST), Ghent University-UGent, K.L. Ledeganckstraat 35, B-9000 Gent, Belgium.
Rondou
Pieter
P
Debowska
Katarzyna
K
Lintermans
Béatrice
B
Vermeulen
Linda
L
Samyn
Bart
B
Skieterska
Kamila
K
Debyser
Griet
G
Devreese
Bart
B
Vanhoenacker
Peter
P
Wojda
Urszula
U
Haegeman
Guy
G
Van Craenenbroeck
Kathleen
K
D000818:Animals; D019390:Arrestins / Q000378:metabolism; D016466:CHO Cells; D002460:Cell Line; D002478:Cells, Cultured; D006224:Cricetinae; D003412:Cricetulus; D015536:Down-Regulation; D006367:HeLa Cells; D006624:Hippocampus / Q000166:cytology; D006801:Humans; D009474:Neurons / Q000166:cytology; D010766:Phosphorylation; D021381:Protein Transport; D051381:Rats; D050638:Receptors, Dopamine D4 / Q000819:agonists* / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D000071557:beta-Arrestins
D019390:Arrestins; C493599:DRD4 protein, human; D000071557:beta-Arrestins; D050638:Receptors, Dopamine D4