Cannabinoid receptor CB1 activates the Na+/H+ exchanger NHE-1 isoform via Gi-mediated mitogen activated protein kinase signaling transduction pathways

We previously showed that the cannabinoid receptor CBI stably transfected in Chinese hamster ovary cells was constitutively active and could be inhibited by the inverse agonist SR 141716A. In the present study, we demonstrate that the cannabinoid agonist CP-55940 induced cytosol alkalinization of CHO-CBI cells in a dose- and time-dependent manner via activation of the Na+/H+ exchanger NHE-1 isoform, By, contrast, the inverse agonist SR 141716A induced acidification of the cell cytosol, suggesting that the Na+/H+ exchanger NHE-1 was constitutively activated by the CBI receptor. CB1-mediated NHE1 activation was prevented by both pertussis toxin treatment and the specific MAP kinase inhibitor PD98059, NHE-1 and p42/p44 MAPK had a similar time course of activation in response to the addition of CP-55940 to CHO-CBI cells. These results suggest that CB1 stimulates NHE-1 by G(i/o)-mediated activation of p42/p44 MAP kinase and highlight a cellular physiological process targeted by CB1. (C) 1999 Federation of European Biochemical Societies.