Abstract

Various naturally occurring polymorphic forms of human G protein-coupled receptors (GPCRs) have been identified and linked to diverse pathological diseases, including receptors for vasopressin type 2 (nephrogenic diabetes insipidus) and gonadotropin releasing hormone (hypogonadotropic hypogonadism). In most cases, polymorphic amino acid mutations disrupt protein folding, altering receptor function as well as plasma membrane expression. Other pathological GPCR variants have been found that do not alter receptor function, but instead affect only plasma membrane trafficking (e.g., delta opiate and histamine type 1 receptors). Thus, altered membrane trafficking with retained receptor function may be another mechanism causing polymorphic GPCR dysfunction. Two common human a2A and a2C adrenergic receptor (AR) variants have been identified (a2A N251K and a2C ?322-325 ARs), but pharmacological analysis of ligand binding and second messenger signaling has not consistently demonstrated altered receptor function. However, possible alterations in plasma membrane trafficking have not been investigated. We utilized a systematic approach previously developed for the study of GPCR trafficking motifs and accessory proteins to assess whether these a2 AR variants affected intracellular trafficking or plasma membrane expression. By combining immunofluorescent microscopy, glycosidic processing analysis, and quantitative fluorescent-activated cell sorting (FACS), we demonstrate that neither variant receptor had altered intracellular localization, glycosylation, nor plasma membrane expression compared to wild-type a2 ARs. Therefore, pathopharmacological properties of a2A N251K and a2C ?322-325 ARs do not appear to be due to altered receptor pharmacology or plasma membrane trafficking, but may involve interactions with other intracellular signaling cascades or proteins.

View details for DOI 10.1007/s00210-014-0972-6

View details for PubMedID 24643471

View details for PubMedCentralID PMC4035122