Department of Medicine, University of California, San Francisco 94143-0711.
Vasoactive intestinal peptide (VIP) is a potent neuropeptide mediator of central and peripheral nervous system function. A human VIP1 receptor (HVR) cDNA clone was previously obtained from HT29 intestinal epithelial 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 [125I]VIP with a Kd of 0.2-0.8 nM, and specifically recognized by anti-HVR antibodies, were established and characterized. VIP induced increases in intracellular cAMP levels ([cAMP]i) dose-dependently with an EC50 of 0.2 nM in 293 and CHO stable transfectants and concurrently evoked dose-dependent increases in intracellular calcium concentrations ([Ca2+]i), as determined by fluorescence-dye spectroscopy. Untransfected 293 and CHO cells showed minimal binding or intracellular effects of VIP; however, native VIP1 receptors of HT29 cells also increased [cAMP]i and [Ca2+]i in dose-dependent responses to VIP. Thus recombinant and native human VIP1 receptors both couple to two distinct signal transduction pathways within a single cell type.