A Novel C-terminal Motif Is Necessary for the Export of the Vasopressin V1b/V3 Receptor to the Plasma Membrane

Jessica Robert, Eric Clauser, Patrice Xavier Petit, Maria Angeles Ventura
2004 Journal of Biological Chemistry  
Little is known about endoplasmic reticulum (ER) export signals, particularly those of members of the Gprotein-coupled receptor family. We investigated the structural motifs involved in membrane export of the human pituitary vasopressin V1b/V3 receptor. A series of V3 receptors carrying deletions and point mutations were expressed in AtT20 corticotroph cells. We analyzed the export of these receptors by monitoring radioligand binding and by analysis of a V3 receptor tagged with both green
more » ... th both green fluorescent protein and Myc epitopes by a novel flow cytometry-based method. This novel method allowed us to quantify total and membrane-bound receptor expression. Receptors lacking the C terminus were not expressed at the cell surface, suggesting the presence of an export motif in this domain. The distal C terminus contains two di-acidic (DXE) ER export motifs; however, mutating both these motifs had no effect on the V3 receptor export. The proximal C terminus contains a di-leucine 345 LL 346 motif surrounded by the hydrophobic residues Phe 341 , Asn 342 , and Leu 350 . The mutation of one or more of these five residues abolished up to 100% of the receptor export. In addition, these mutants colocalized with calnexin, demonstrating that they were retained in the ER. Finally, this motif was sufficient to confer export properties on a CD8␣ glycoprotein-V3 receptor chimera. In conclusion, we have identified a novel export motif, FN(X) 2 LL(X) 3 L, in the C terminus of the V3 receptor.
doi:10.1074/jbc.m410655200 pmid:15528211 fatcat:pi3fvapx3zczvkbyucgtrejqwq