Role for the third intracellular loop in cell surface stabilization of the alpha2A-adrenergic receptor.
Previous studies have shown that alpha2A-adrenergic receptor (alpha2A-AR) retention at the basolateral surface of polarized MDCKII cells involves its third intracellular (3i loop). The present studies examining mutant alpha2A-ARs possessing short deletions of the 3i loop indicate that no single region can completely account for the accelerated surface turnover of the Delta3ialpha2A-AR, suggesting that the entire 3i loop is involved in basolateral retention. Both wild-type and Delta3i loop alpha2A-ARs are extracted from polarized Madin-Darby canine kidney (MDCK) cells with 0.2% Triton X-100 and with a similar concentration/response profile, suggesting that Triton X-100-resistant interactions of the alpha2A-AR with cytoskeletal proteins are not involved in receptor retention on the basolateral surface. The indistinguishable basolateral t(1)/(2) for either the wild-type or nonsense 3i loop alpha2A-AR suggests that the stabilizing properties of the alpha2A-AR 3i loop are not uniquely dependent on a specific sequence of amino acids. The accelerated turnover of Delta3i alpha2A-AR cannot be attributed to alteration in agonist-elicited alpha2A-AR redistribution, because alpha2A-ARs are not down-regulated in response to agonist. Taken together, the present studies show that stabilization of the alpha2A-AR on the basolateral surface of MDCKII cells involves multiple mechanisms, with the third intracellular loop playing a central role in regulating these processes.
Edwards
S W
SW
Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA.
Limbird
L E
LE
D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000737:chemistry; D003902:Detergents; D004285:Dogs; D008969:Molecular Sequence Data; D017830:Octoxynol; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D018341:Receptors, Adrenergic, alpha-2 / Q000737:chemistry*; D013329:Structure-Activity Relationship; D013499:Surface Properties
D003902:Detergents; D018341:Receptors, Adrenergic, alpha-2; D017830:Octoxynol