Spinophilin Stabilizes Cell Surface Expression of alpha sub(2B)-Adrenergic Receptors

The third intracellular (3i) loops of the alpha sub(2A)- and alpha sub(2B)-adrenergic receptor (AR) subtypes are critical for retention of these receptors at the basolateral surface of polarized Madin-Darby canine kidney (MDCKII) cells at steady state. The third intracellular loops of the alpha sub(2A), alpha sub(2B), and alpha sub(2C)-AR subtypes interact with spinophilin, a multidomain protein that, like the three alpha sub(2)-AR subtypes, is enriched at the basolateral surface of MDCKII cells. The present studies provide evidence that alpha sub(2)-AR interaction with spinophilin contributes to cell surface stabilization of the receptor. We exploited the unique targeting profile of the alpha sub(2B)-AR subtype in MDCKII cells: random delivery to apical and basolateral surfaces with rapid (t sub([1/2])