Receptor chimeras and truncations reveal α2a adrenergic receptor (a2aar) domains involved in its basolateral localization in mdckii cells

To elucidate structural regions in the CX2AAR responsible for its exclusive and direct delivery to the lateral subdomain of renal epithelial cells, we constructed a chimera with the AI adenosine receptor (AiAdoR), which we have shown is enriched on the apical surface of Madin-Darby canine kidney II (MDCKII) cells. Epitope-tagged <X2AAR/AiAdoR chimera (encoding (X2AAR transmembranes (TM)l-5 and AiAdoR TM 6,7) in multiple MDCKII cell clones reveal apical and basolateral staining patterns via confocal microscopy. Metabolic labeling studies that this chimera is first delivered primarily apically, but then is enriched on the basolateral surface. A truncation mutant of the (X2AAR, (TM 1-5), also is expressed on the basolateral surface, albeit with limited efficiency based on immunocytochemical studies of two independent clones. Metabolic labeling studies show that it is first delivered basolaterally, but then later accumulates preferentially on the apical surface. Taken together, studies with the chimera and the truncation mutant suggest that TM 1-5 of (X2AAR contain some necessary information for basolateral delivery but not for sustained retention on that surface.