Dopamine D2 receptor dimers in human and rat brain

Abstract

In order to determine whether dimers of dopamine D2 receptors can occur in mammalian brain, rat and human brain striatal membranes were photolabelled with two radioactive photoaffinity compounds selective for dopamine D2 receptors, [ IPS I]azidophenethylspiperone and [IPS I]-4-azido-5-iodonemonapride. It was found that [IPS I]azidophenethylspiperone only labelled the D2 monomer, while [IPS I]-4-azido-5-iodonemonapride labelled both D2 monomers and dimers, despite the fact that very high concentrations (6 nM) of both radiocompounds were used. In addition, human cloned D2 receptors were probed with a D2-specific antibody, revealing multiple bands indicating the existence of trimers, tetramers and pentamers of D2 receptors. The different D2-binding patterns of the spiperone and benzamide congeners may explain the different densities of dopamine D2 receptors found with these two radioligands in human brain positron tomography in health and disease.z 1998 Federation of European Biochemical Societies.

Novel identification of peripheral dopaminergic D2 receptor in male germ cells

“…1B), similar to that observed by some authors in other cell systems [Farooqui et al, 1992;Zawarynski et al, 1998;Lee et al, 2000;Scarselli et al, 2001]. This heterogeneity can be explained by homodimerization [Zawarynski et al, 1998;Guo et al, 2003;Lee et al, 2003] and heterooligomerization of the D2 receptor [Rocheville et al, 2000;Canals et al, 2003: Kearn et al, 2005. Immunoprecipitation detection analysis with a monoclonal antibody only detected a predominant broad band of an apparent molecular mass of 50 kDa that can correspond to both isoforms (Fig.…”

“…Figure 1B shows the Western blot analysis of membrane proteins extracted from rat brain and testis (lanes 1 and 2, respectively). The D2 receptor antibody reacted with two bands that migrated with an apparent Mr of 47-50 kDa and bands with a higher molecular mass which could correspond to oligomerizations described previously for D2 receptor in other cell systems [Zawarynski et al, 1998;Lee et al, 2000]. The peptide pre-adsorbed antiserum control showed no stain for D2R testis membrane proteins (lane 3).…”

Methamphetamine Increases Dopamine Transporter Higher Molecular Weight Complex Formation via a Dopamine- and Hyperthermia-Associated Mechanism

“…D2 dimer and higher-order oligomers may be partially SDS resistant (Zawarynski et al, 1998); however, Guo et al (2003), using cysteine cross-linking, have shown that the D2 receptor is a native homodimer but does not survive detergent solubilization. Because of the potential for disulfide linkages that could be induced by METH-induced ROS formation and the fact that, like DAT, the D2 receptor is found presynaptically on DA nerve terminals, effects of METH treatment on this protein were assessed.…”

Dopamine and Serotonin Receptor Binding and Antipsychotic Efficacy

“…Also, the binding data used in the current analysis, measuring ligand binding to cloned human receptors expressed in cell culture systems, may be distinct from binding to limbic neurotransmitter receptor populations in vivo. Differences in receptor phosphorylation, glycosylation, and/or dimerization to hetero-oligomers (Nimchinsky et al, 1997;Scarselli et al, 2001;Zawarynski et al, 1998;Lee et al, 2000) between in vivo and cell culture systems lacking post-translational machinery could potentially alter receptor-binding affinity. Additionally, atypical antipsychotic medications as a group tend to have more rapid dissociation rates from DA receptors than typical antipsychotics (Kapur and Seeman, 2001), an effect that might further complicate the relationship between receptor affinity and clinically effective drug dose.…”