HUMAN VASOACTIVE INTESTINAL PEPTIDE(1) RECEPTORS EXPRESSED BY STABLE TRANSFECTANTS COUPLE TO 2 DISTINCT SIGNALING PATHWAYS

Vasoactive intestinal peptide (VIP) is a potent neuropeptide mediator of central and peripheral nervous system function. A human VIP1 recept or (HVR) cDNA clone was previously obtained from HT29 intestinal epith elial cells and lung tissue. Stably-transfected human embryonic kidney 293 cells and chinese hamster ovary (CHO) cells expressing about 10(6 ) HVRs per cell that bind [I-125]VIP with a Kd of 0.2 - 0.8 nM, and sp ecifically recognized by anti-HVR antibodies, were established and cha racterized. VIP induced increases in intracellular cAMP levels ([cAMP] i) dose-dependently with EC50 of 0.2 nM in 293 anxc CHO stable transfe ctants and concurrently evoked dose-dependent increases in intracellul ar calcium concentrations ([Ca2+]i) as determined by fluorescence-dye spectroscopy. Untransfected 293 anc CHO cells showed minimal binding o f intracellular effects of VIP; however, native VIP1 receptors of HT29 cells also increased [cAMP]i and [Ca2+]i-dependent responses to VIP. Thus recombinant and native human VIP1 receptors both couple to two di stinct signal transduction pathways within a single cell type. (C) 199 1 Academic Press, Inc.