Receptors coupled to pertussis toxin-sensitive G-proteins traffic to opposite surfaces in Madin-Darby canine kidney cells. A1 adenosine receptors achieve apical and alpha 2A adrenergic receptors achieve basolateral localization

Abstract

The alpha 2A adrenergic receptor (alpha 2AAR) previously was shown to be directly delivered to and retained on the lateral subdomain of renal epithelial cells. The present studies demonstrate that, in contrast, wild-type and epitope-tagged canine A1 adenosine receptors (A1AdoR) are apically enriched (65-83%) in Madin-Darby canine kidney (MDCKII) and porcine renal epithelial (LLC-PKI) cells, based on surface biotinylation strategies detecting photoaffinity-labeled A1AdoR. Confocal microscopy corroborated the apical enrichment of the epitopetagged A1AdoR. Metabolic labeling studies revealed that this steady-state polarization is achieved by direct delivery to both the apical (60-75%) and basolateral surface. Growth of A1AdoR-expressing cells as monolayers presence of A1AdoR antagonists, which decreased cell growth, suggesting that A1AdoR elicit MDCKII cell proliferation. The preferential apical but detectable basolateral localization of A1AdoR provides a molecular understanding of published reports that functional responses can be elicited following apical as well as basolateral delivery of adenosine agonists in varying renal preparations. These findings also suggest that receptor chimeras derived from the Gi/Go-protein-coupled alpha 2AAR and A1AdoR will be informative in revealing structural features critical for basolateral versus apical targeting.