title: Dopamine D4 receptor oligomerization--contribution to receptor biogenesis.
abstract: Dopamine D(4) receptors (D(4) Rs) are G protein-coupled receptors that play a role in attention and cognition. In the present study, we investigated the dimerization properties of this receptor. Western blot analysis of the human D(4.2)R, D(4.4)R and D(4.7)R revealed the presence of higher molecular weight immunoreactive bands, which might indicate the formation of receptor dimers and multimers. Homo- and heterodimerization of the receptors was confirmed by co-immunoprecipitation and bioluminescence resonance energy transfer studies. Although dimerization of a large number of G protein-coupled receptors has been described, the functional importance often remains to be elucidated. Folding efficiency is rate-limiting for D(4)R biogenesis and quality control in the endoplasmic reticulum plays an important role for D(4)R maturation. Co-immunoprecipitation and immunofluorescence microscopy studies using wild-type and a nonfunctional D(4.4)R folding mutant show that oligomerization occurs in the endoplasmic reticulum and that this plays a role in the biogenesis and cell surface targeting of the D(4)R. The different polymorphic repeat variants of the D(4)R display differential sensitivity to the chaperone effect. In the present study, we show that this is also reflected by bioluminescence resonance energy transfer saturation assays, suggesting that the polymorphic repeat variants have different relative affinities to form homo- and heterodimers. In summary, we conclude that D(4)Rs form oligomers with different affinities and that dimerization plays a role in receptor biogenesis.
authors.affiliation: Laboratory of Eukaryotic Gene Expression and Signal Transduction (LEGEST), Ghent University Hospital, UZ Gent, Belgium. kathleen.vancraenenbroeck@ugent.be
authors.forename: Kathleen
authors.initials: K
authors.lastname: Van Craenenbroeck
authors.forename: Dasiel O
authors.initials: DO
authors.lastname: Borroto-Escuela
authors.forename: Wilber
authors.initials: W
authors.lastname: Romero-Fernandez
authors.forename: Kamila
authors.initials: K
authors.lastname: Skieterska
authors.forename: Pieter
authors.initials: P
authors.lastname: Rondou
authors.forename: Béatrice
authors.initials: B
authors.lastname: Lintermans
authors.forename: Peter
authors.initials: P
authors.lastname: Vanhoenacker
authors.forename: Kjell
authors.initials: K
authors.lastname: Fuxe
authors.forename: Francisco
authors.initials: F
authors.lastname: Ciruela
authors.forename: Guy
authors.initials: G
authors.lastname: Haegeman
mesh_terms: D019281:Dimerization; D004721:Endoplasmic Reticulum / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D008163:Luminescent Measurements; D017510:Protein Folding; D050638:Receptors, Dopamine D4 / Q000737:chemistry / Q000378:metabolism*
chemical_list: D050638:Receptors, Dopamine D4