Parallel inactivation of Y2 receptor and G-proteins in CHO cells by pertussis toxin

The Y2 receptor for neuropeptide Y (NPY) interacts with pertussis toxin (PTX)-sensitive G-proteins, but little is known about interdependence of their levels and functions. We found that PTX reduces Y2 receptors expressed in CHO cells in parallel to inactivation of Gi G-proteins, to loss of inhibition by Y2 agonists of forskolin-stimulated adenylyl cyclase, and to decrease in the binding of GTP-γ-S. These losses were attenuated by the endosome alkalinizer ammonium chloride. Affinity of the Y2 receptor was not changed by PTX treatment. Prolonged treatment induced a large decrease of Y2 receptor immunoreactivity (more than 70% in 48 h). The Gi3 α-subunit immunoreactivity decreased slowly (about 46% in 48 h). There was a significant increase in Gq α immunoreactivity and in fraction of Y2 binding sensitive to a Gq-selective antagonist. Possibly linked to that, the surface Y2 sites and the internalization of the Y2 receptor were less than 40% reduced. However, the abundant masked Y2 sites were eliminated by the toxin, and could be mainly coupled to PTX-sensitive G-proteins.