title: D2 dopamine receptor activation of potassium channels is selectively decoupled by Galpha-specific GoLoco motif peptides.
abstract: The GoLoco motif is a short polypeptide sequence found in G-protein signaling regulators such as regulator of G-protein signaling proteins type 12 and 14 and activator of G-protein signaling protein type 3. A unique property of the GoLoco motifs from these three proteins is their preferential interaction with guanosine diphosphate (GDP)-bound Galpha(i1), Galpha(i3) and, sometimes, Galpha(i2) subunits over Galpha(o) subunits. This interaction prevents both spontaneous guanine nucleotide release and reassociation of Galpha(i)-GDP with Gbetagamma. We utilized this property of the GoLoco motif to examine dopamine (D2 and D3) and somatostatin receptor coupling to G-protein-regulated inwardly rectifying potassium (GIRK) channels in mouse AtT20 cells. GoLoco motif peptides had no effect on either basal channel activity or the initial responses to agonists, suggesting that the GoLoco motif cannot disrupt pre-formed G-protein heterotrimers. GoLoco motif peptides did, however, interfere with human D2((short)) receptor coupling to GIRK channels as demonstrated by the progressively diminished responses after repeated agonist application. This behavior is consistent with some form of compartmentalization of D2 receptors and GIRK channels such that Gbetagamma subunits, freed by local receptor activation and prevented from reforming a heterotrimeric complex, are not functionally constrained within the receptor-channel complex and thus are unable to exert a persistent activating effect. In contrast, GoLoco motif peptides had no effect on either D3 or somatostatin coupling to GIRK channels. Our results suggest that GoLoco motif-based peptides will be useful tools in examining the specificity of G-protein-coupled receptor-effector coupling.
authors.affiliation: Department of Cell and Molecular Physiology and UNC Neuroscience Center, University of North Carolina, Chapel Hill, North Carolina, USA.
authors.forename: Christina K
authors.initials: CK
authors.lastname: Webb
authors.forename: Christopher R
authors.initials: CR
authors.lastname: McCudden
authors.forename: Francis S
authors.initials: FS
authors.lastname: Willard
authors.forename: Randall J
authors.initials: RJ
authors.lastname: Kimple
authors.forename: David P
authors.initials: DP
authors.lastname: Siderovski
authors.forename: Gerry S
authors.initials: GS
authors.lastname: Oxford
mesh_terms: D020816:Amino Acid Motifs / Q000502:physiology; D000818:Animals; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism*; D006801:Humans; D046911:Macromolecular Substances / Q000378:metabolism; D051379:Mice; D010455:Peptides / Q000737:chemistry / Q000494:pharmacology*; D024661:Potassium Channels, Inwardly Rectifying / Q000187:drug effects / Q000378:metabolism*; D021122:Protein Subunits / Q000187:drug effects / Q000378:metabolism; D017448:Receptors, Dopamine D2 / Q000187:drug effects / Q000378:metabolism*; D050637:Receptors, Dopamine D3; D043562:Receptors, G-Protein-Coupled / Q000187:drug effects / Q000378:metabolism*; D017481:Receptors, Somatostatin / Q000187:drug effects / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*
chemical_list: C493593:DRD3 protein, human; C493594:Drd3 protein, mouse; D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels; D046911:Macromolecular Substances; D010455:Peptides; D024661:Potassium Channels, Inwardly Rectifying; D021122:Protein Subunits; D017448:Receptors, Dopamine D2; D050637:Receptors, Dopamine D3; D043562:Receptors, G-Protein-Coupled; D017481:Receptors, Somatostatin; D019206:GTP-Binding Protein alpha Subunits, Gi-Go