Receptors coupled to pertussis toxin-sensitive G-proteins traffic to opposite surfaces in Madin-Darby canine kidney cells - A(1) adenosine receptors achieve apical and alpha(2A) adrenergic receptors achieve basolateral localization

The alpha(2A) adrenergic receptor (alpha(2A)AR) 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 A(1) adenosine receptors (A(1)AdoR) 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 A(1)AdoR. Confocal micros copy corroborated the apical enrichment of the epitope-tagged A(1)AdoR. 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 A(1)AdoR-expressing cells as monolayers was achieved only following Transwell culture in the presence of A(1)AdoR antagonists, which decreased cell growth, suggesting that A(1)AdoR elicit MDCKII cell proliferation. The preferential apical but detectable basolateral localization of A(1)AdoR 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 G(i)/G(o)-protein-coupled alpha(2A)AR and A(1)AdoR will be informative in revealing structural features critical for basolateral versus apical targeting.