[Recombinant receptors for testing agonists and antagonists of VIP and PACAP receptors]

VIP and PACAP are structurally related neuropeptides. They interact with multiple classes of receptors that have been cloned recently. These receptors may be divided into two main classes: the PACAP type I receptors with a high affinity for PACAP and a low affinity for VIP and the PACAP type II receptors (with a high affinity for PACAP and VIP). Five different forms of the PACAP type I receptors are described and result from an alternative splicing of the messenger. Two distinct forms (VIP1 and VIP2 receptors) of the PACAP type II receptors are described. Considering this high number of variants and the coexistence of several variants in the same cell, the development of cell lines expressing a single type of receptor was required for the testing of selective agonists and antagonists. However, limits in the interpretation of the results obtained in the cell lines expressing the recombinant receptors were obvious: discovery of unusual receptor states and unusual coupling of cellular effectors when a high number of receptors was expressed.