UNIQUE STRUCTURAL FEATURES IMPORTANT FOR STABILIZATION VERSUS POLARIZATION OF THE ALPHA(2A)-ADRENERGIC RECEPTOR ON THE BASOLATERAL MEMBRANEOF MADIN-DARBY CANINE KIDNEY-CELLS
Jr. Keefer et al., UNIQUE STRUCTURAL FEATURES IMPORTANT FOR STABILIZATION VERSUS POLARIZATION OF THE ALPHA(2A)-ADRENERGIC RECEPTOR ON THE BASOLATERAL MEMBRANEOF MADIN-DARBY CANINE KIDNEY-CELLS, The Journal of biological chemistry, 269(23), 1994, pp. 16425-16432
The alpha(2A)-adrenergic receptor (alpha(2A)AR) is polarized to the ba
solateral membrane of Madin-Darby canine kidney cells via direct targe
ting. Examination of mutant <alpha >(2A)AR reveals that direct deliver
y is independent of NH,-terminal glycosylation, COOH-terminal acylatio
n, or protein sequences within the large third cytoplasmic loop or COO
H-terminal tail. Combined mutation of these structural features also d
oes not perturb alpha(2A)AR delivery, suggesting that a three-dimensio
nal structure imparted by non-contiguous endofacial sequences does not
confer alpha(2A)AR targeting and that motifs in or near the bilayer m
ust be involved in targeting of the alpha(2A)AR. Mutation of a conserv
ed Asp residue in transmembrane two that alters receptor-G-protein int
eractions also does not impair alpha(2A)AR targeting. Finally, modific
ation of sequences in transmembrane seven that resemble tyrosine-conta
ining endocytosis motifs utilized for targeting by some proteins does
not perturb alpha(2A)AR sorting. Interestingly, deletion of the large
third cytoplasmic loop of the alpha(2A)AR decreases receptor half-life
on the basolateral surface from approximately 11 to 4.5 h without alt
ering the ability of the alpha(2A)AR to couple to G-proteins. These da
ta suggest that although targeting of the alpha(2A)AR likely involves
bilayer sequences, the third cytoplasmic loop may contain structural f
eatures that promote stabilization of the alpha(2A)AR on the basolater
al surface of Madin-Darby canine kidney cells.