Dimers of G-Protein Coupled Receptors as Versatile Storage and Response Units

Abstract

The status and use of transmembrane, extracellular and intracellular domains in oligomerization of heptahelical G-protein coupled receptors (GPCRs) are reviewed and for transmembrane assemblies also supplemented by new experimental evidence. The transmembrane-linked GPCR oligomers typically have as the minimal unit an asymmetric ~180 kDa pentamer consisting of receptor homodimer or heterodimer and a G-protein αβγ subunit heterotrimer. With neuropeptide Y (NPY) receptors, this assembly is converted to ~90 kDa receptor monomer-Gα complex by receptor and Gα agonists, and dimers/heteropentamers are depleted by neutralization of Gαi subunits by pertussis toxin. Employing gradient centrifugation, quantification and other characterization of GPCR dimers at the level of physically isolated and identified heteropentamers is feasible with labeled agonists that do not dissociate upon solubilization. This is demonstrated with three neuropeptide Y (NPY) receptors and could apply to many receptors that use large peptidic agonists.

Japanese Herbal Medicine Ninjinyoeito Mediates Its Orexigenic Properties Partially by Activating Orexin 1 Receptors

“…However, the selective NPY1R antagonist BIBO3340 did not significantly decrease NPY1R-induced responses (Figure 2A). Recently, it has been reported that NPYR forms heterodimers with other GPCRs (41,42). In some cases, the responses of GPCR heterodimers were not notably inhibited by the antagonist of each GPCR monomer (43).…”

Neuropeptide Y receptor interactions regulate its mitogenic activity

“…Despite growing evidence for GPCR homo-and heterodimerization, the functional outcomes of these interactions remain elusive. Within the NPY receptor family, all receptors have been shown to form homodimers, while Y1R additionally can heterodimerize with Y5R, Y4R and β-adrenergic receptors (39)(40)(41)(42)(43)(44)(45)(46)(47). Nevertheless, reports pertaining to the receptor fate upon agonist stimulation vary depending on the methodology, while experiments with bivalent ligands do not support their enhanced ability to stimulate NPY receptors (48,49).…”

“…Thus, the goal of the current study was to characterize NPY receptor interactions in live cells, as well as the impact of these processes on the receptor activation and function. In contrast to previous studies using fluorescence and bioluminescence resonance energy transfer methods (FRET and BRET, respectively), as well as isolated membrane preparations, all of which analyzed the entire population of the receptors present in the cells, we have focused on their active fraction present on the plasma membrane and responsible for ligand binding (39)(40)(41)(42)(43)(44)(45)(46)(47). To elucidate the functional role of the receptor interactions, we used the mitogenic activity of NPY as a model, since previous results from our laboratory strongly implicated the role for the heterotypic NPY receptor expression in augmenting its growth-regulatory effects in various cells (29,37).…”

“…However, the functional role of such receptor interactions remains elusive and the data pertaining to the pharmacological changes and receptor behavior upon ligand stimulation vary depending on methodology and experimental design. Importantly, most previous studies analyzed the entire receptor population within the cell, including intracellular fraction, which is not involved in ligand binding (39)(40)(41)(42)(43)(44)(45)(46)(47). In addition, experiments with bivalent receptor ligands did not support the postulated role of receptor dimerization in augmenting NPY functions (48,49).…”

“…The potential role of NPY receptor interactions in regulation of NPY functions has been supported by dimerization of the NPY receptors. All NPY receptor types have been shown to form homodimers, while some studies suggest heterodimerization of Y1R and Y5R (39)(40)(41)(42)(43)(44)(45)(46)(47). However, the functional role of such receptor interactions remains elusive and the data pertaining to the pharmacological changes and receptor behavior upon ligand stimulation vary depending on methodology and experimental design.…”