Pertussis toxin induces parallel loss of neuropeptide YY1 receptor dimers and Giα subunit function in CHO cells

Treatment with pertussis toxin in addition to a stable inhibition of G(i)alpha subunits of G-proteins also strongly reduced human neuropeptide Y Y-1 receptors expressed in Chinese hamster ovary (CHO) cells. This was reflected in abolition of the inhibition by Y-1 agonists of forskolin-stimulated adenylyl cyclase in intact cells, and of Y-1 agonist stimulation of GTP-gamma S binding to particulates from disrupted cells. The loss of both receptor and Gia subunit function was attenuated by ammonium chloride, an inhibitor of acid proteinases, pointing to a chaperoning co-protection of active pertussis toxin-sensitive G alpha subunits and Y-1 receptors. The surface complement of the Y-1 receptor was changed a little in conditions of similar to 85% decrease of the Y-1 population, but the rate of the Y-1 receptor-linked internalization of agonist peptides was reduced about 70%. The preserved receptor fraction consisted of monomers significantly coupled to G(q)alpha subunits. The persistent pertussis toxin-insensitive internalization of agonists with the Y-1 receptor may reflect a rescue or alternative switching that could be important for cell functioning in neuropeptide Y-rich environments. The results are compatible with a loss, due to G(i)alpha subunit inactivation by the toxin, of a large Y-1 receptor reserve constituted of oligomers associating with heterotrimeric G-proteins. (C) 2007 Elsevier B.V. All rights reserved.