Design: An assay based on single-polypeptide-chain heterodimeric A2AR/D2R and non-oligomerized fusions for in vivo analysis of their allosteric receptor-receptor interactions

Abstract

AbstractBackgroundThe adenosine A2A receptor (A2AR) heteromerizes with the dopamine D2 receptor (D2R). In order to explore their functional interaction, we engineered previously stable single-polypeptide-chain (sc) A2AR/D2LR: whether the molecular entity of the striatal A2AR/D2R antagonism, i.e., scA2AR/D2Rs are just A2AR/D2R with the antagonism, remains unresolved.New MethodTo further clarify the heteromerization through the scA2AR/D2LR, we here designed supramolecularly ‘exclusive’ monomers and dimers, using the Cε2 domain of IgE-Fc or apoproteins of the bacterial light-harvesting antenna complex.ResultsA concept of the recptor protein assembly regulation, i.e., the selective monomer/non-obligate dimer formation was obtained. Although none of these new fusions were constructed or tested, we could aim at obtaining heterodimer-specific agents, using the scA2AR/D2R. Whether the resulting designs were explained feasibly and rationally was addressed. The structure and function of the non-obligate dimer were here discussed through scA2AR/D2R, focusing on the procedure of the membrane protein design and methods for transient protein-protein interactions.Summary and OutlookGiven that upon being expressed and allosteric regulation occurs regardless of specific signal to non-specific noise (S/N) ratio, the supramolecular designs, allowing us to express selectively monomer/non-obligate dimer of class A GPCR, are experimentally testable and will be used to confirm in vivo that such low S/N ratio interaction between A2AR and D2LR functions in the dopamine neurotransmission in the striatum.Abbreviations:A2ARadenosine A2A receptor3HA-A2ARA2AR tagged with a triple HA epitopeBchlbacteriochlorophyllBRETbioluminescence resonance energy transferCcarboxy-terminalCDcluster of differentiationD2LR and D2SRthe long and short form of dopamine D2 receptor, respectivelyFabantigen binding fragmentFcFc fragmentFcεRIhigh affinity receptor for IgEFRETfluorescence resonance energy transferG4San amino acid sequence consisting of a four-glycine-repeat followed by a serine residueGABAγ-aminobutyric acidGABABGABA type B receptorGPCRG protein-coupled receptorGttransducinHAhemagglutininHIVhuman immunodeficiency virusICintracellular loopsIgimmunoglobulinLHlight-harvesting antenna complexmAbmonoclonal antibodyMrmolecular weightNamino-terminalPDParkinson’s diseasePSphotosystemRCreaction centerRlucRenilla luciferasescsingle-chainTMtransmembrane3Dthree-dimensional