Molecular Characterization of Helodermin-Preferring VIP Receptors in SUP T1Lymphoma Cells: Evidence for Receptor Glycosylation

Cross-linking of [125I]helodermin to human SUP-T1 lymphoblasts with bis[2-(succinimidooxycarbonyloxy)ethyl]sulfone (BSOCOES) revealed a 63 K binding protein. This cross-linking was inhibited by helodermin and VIP. In cells submitted for 3-4 days to 0.2 microgram/ml tunicamycin, the Mr of an increasing proportion of helodermin-preferring receptors was reduced to 50 K and the total number of receptors was decreased by about 50%, without alteration in binding affinity and specificity. In parallel, the VIP-mediated adenylate cyclase stimulation was reduced by 30% with no change in NaF-, Gpp[NH]p-, and PGE1-stimulations. We conclude that a proper N-glycosylation of helodermin-preferring VIP receptors is required for normal receptor targeting and turnover but not for ligand binding and adenylate cyclase coupling.