Glycosylation of the calcitonin receptor-like receptor at Asn60 or Asn112 is important for cell surface expression

The human calcitonin (CT) receptor-like receptor (hCRLR) of the B family of G protein-coupled receptors is N-glycosylated and associates with receptor-activity-modifying proteins for functional interaction with CT gene-related peptide (CGRP) or adrenomedullin (ADM), respectively. Three putative N-glycosylation sites Asn(60), Asn(112) and Asn(117) are present in the amino-terminal extracellular domain of the hCRLR. Tunicamycin dose-dependently inhibited the glycosylation of a myc-tagged hCRLR and in parallel specific [I-125]CGRP and -ADM, binding. Similarly, the double mutant myc-hCRLR(N60,112T) exhibited minimal N-glycosidase F sensitive glycosylation, presumably at the third Asn(117), and the cell surface expression and specific radioligand binding were impaired. Substitution of the Asn(117) by Thr abolished CGRP and ADM binding in the face of intact N-glycosylation and cell surface expression. (C) 2000 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.