The α2-adrenergic receptor (α2-AR) is a member of the seven transmembrane-spanning G-protein-coupled receptor superfamily. In the kidney, the α2-AR is most abundant in the epithelial cells of the proximal tubule where it is important in enhancing Na+ reabsorption via the modulation of Na+/H+ exchange. Radioligand binding and physiological studies suggest that the α2-AR resides primarily on the basolateral surface of these proximal tubule cells in vivo. To investigate the mechanisms underlying α2-AR polarization in epithelial cells, we permanently expressed wild-type and an epitope-tagged version of the α(2A)-AR in Madin-Darby canine kidney (MDCK) cells. Using a steady-state surface biotinylation assay, we observe that 80- 90% of the α(2A)-AR in MDCK cell clones is located on the basolateral membrane domain. Immunolocalization studies confirm the biotinylation results and demonstrate that the α(2A)-AR is actually confined primarily to the lateral domain of the basolateral surface. Metabolic labeling experiments suggest that basolateral polarization of the α(2A)-AR is achieved by direct targeting of the receptor to the basolateral domain. Targeting of the α(2A)- AR to the basolateral surface is not perturbed by pertussis toxin-treatment of MDCK cells, suggesting that coupling of the α(2A)-AR to GTP-binding proteins is not important for receptor polarization.
|Original language||English (US)|
|Number of pages||8|
|Journal||Journal of Biological Chemistry|
|State||Published - 1993|
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology