Evidence for the dual coupling of the rat neurotensin receptor with pertussis toxin-sensitive and insensitive G-proteins.

We previously demonstrated the functional coupling of the rat neurotensin receptor NTS1 with G-proteins on transfected CHO cell homogenates by showing modulation of agonist affinity by guanylyl nucleotides and agonist-mediated stimulation of [(35)S]GTP gamma S binding. In the present study, we observed that G(i/o)-type G-protein inactivation by pertussis toxin (PTx) resulted in a dramatic reduction of the NT-induced [(35)S]GTP gamma S binding whereas the effect of guanylyl nucleotide was almost not affected. As expected, NT-mediated phosphoinositide hydrolysis and intracellular calcium mobilization were not altered after PTx treatment. This suggests the existence of multiple signaling cascades activated by NT. Accordingly, using PTx and the PLC inhibitor U-73122, we showed that both signaling pathways contribute to the NT-mediated production of arachidonic acid. These results support evidence for a dual coupling of the NTS1 with PTx-sensitive and insensitive G-proteins.