RT Journal Article
SR Electronic
T1 Molecular and Conformational Features of a Transport-Relevant Domain in the C-Terminal Tail of the Vasopressin V<sub>2</sub>Receptor
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP 232
OP 242
VO 57
IS 2
A1 Krause, Gerd
A1 Hermosilla, Ricardo
A1 Oksche, Alexander
A1 Rutz, Claudia
A1 Rosenthal, Walter
A1 Schülein, Ralf
YR 2000
UL http://molpharm.aspetjournals.org/content/57/2/232.abstract
AB We have previously shown a conserved glutamate/dileucine motif (335 ELRSLL 340) in the intracellular C terminus of the vasopressin V2 receptor (V2 receptor) to be essential for receptor transport from the endoplasmic reticulum (ER) to the Golgi apparatus. The motif may represent a transport signal that is recognized by a component of ER to Golgi vesicles. Alternatively, it may be necessary for transport-competent receptor folding to pass the quality-control system of the ER. To assess these two possibilities, we constructed a receptor fragment that allows transport studies independent of full-length receptor folding. Transmembrane domains II–VII were deleted, thereby fusing the intracellular C terminus to the first cytoplasmic loop. The mutations that impaired transport of the full-length receptor were introduced, and receptor fragments were localized in transiently transfected HEK 293 cells. All mutant receptor fragments were detectable at the plasma membrane, demonstrating that the glutamate/dileucine motif does not function as a small, linear vesicular transport signal. Instead, our data strongly suggest that this motif is required for transport-competent folding of the full-length receptor. To assess the underlying conformational features, a three-dimensional homology model of the V2 receptor was computed. Our model predicts that the glutamate/dileucine motif contributes to a U-like loop within the intracellular C terminus. Residue Leu339 may be required for folding back the intracellular C terminus to residue Leu62 of the first cytoplasmic loop. We characterized the naturally occurring L62P and ΔL62-R64 mutations in the first cytoplasmic loop and show that they lead to transport-defective full-length V2 receptors that are retained in the ER, consistent with the structure model. The American Society for Pharmacology and Experimental Therapeutics