Molecular and conformational features of a transport-relevant domain in the C-terminal tail of the vasopressin V(2) receptor

Item Type:	Article
Title:	Molecular and conformational features of a transport-relevant domain in the C-terminal tail of the vasopressin V(2) receptor
Creators Name:	Krause, G. and Hermosilla, R. and Oksche, A. and Rutz, C. and Rosenthal, W. and Schuelein, R.
Abstract:	We have previously shown a conserved glutamate/dileucine motif ((335)ELRSLL(340)) in the intracellular C terminus of the vasopressin V(2) receptor (V(2) 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 V(2) receptor was computed. Our model predicts that the glutamate/dileucine motif contributes to a U-like loop within the intracellular C terminus. Residue Leu(339) may be required for folding back the intracellular C terminus to residue Leu(62) of the first cytoplasmic loop. We characterized the naturally occurring L62P and DeltaL62-R64 mutations in the first cytoplasmic loop and show that they lead to transport-defective full-length V(2) receptors that are retained in the ER, consistent with the structure model.
Keywords:	Amino Acid Sequence, Biological Transport, Endoplasmic Reticulum, Glutamic Acid, Golgi Apparatus, Leucine, Molecular Models, Molecular Sequence Data, Mutation, Protein Conformation, Protein Folding, Vasopressin Receptors, Amino Acid Sequence Homology, Signal Transduction
Source:	Molecular Pharmacology
ISSN:	0026-895X
Publisher:	American Society for Pharmacology and Experimental Therapeutics
Volume:	57
Number:	2
Page Range:	232-242
Date:	February 2000
Official Publication:	http://molpharm.aspetjournals.org/cgi/content/abstract/57/2/232
PubMed:	View item in PubMed

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