AGONIST AND ANTAGONIST-DEPENDENT INTERNALIZATION OF THE HUMAN VASOPRESSIN V-2 RECEPTOR

In this report we demonstrate that in HEK293 cells stably expressing t he human V-2 vasopressin receptor, ligand-induced internalization of t he hormone receptor occurs via the clathrin-dependent pathway. Studies of receptor trafficking either by direct visualization of the V-2 rec eptor by confocal microscopy or binding experiments show a rapid inter nalization (half-time 6-7 min), Blocking of the clathrin-dependent pat hway by hypertonic sucrose increased vasopressin-induced cellular cAMP production and decreased the desensitization of the V-2 receptor-aden ylyl cyclase system. Thus, internalization appears to be a major regul atory mechanism terminating vasopressin action in HEK293 cells. Two an tagonists of the vasopressin V-2 receptor exerted different effects on receptor internalization, as determined by confocal fluorescence micr oscopy, The nonpeptidic antagonist OPC31260 did not induce any visible receptor internalization, whereas the peptidic antagonist d(CH2)(5)[D -Tyr(Et)(2),Val(4),Lys(8), Tyr-NH29]VP induced a slow but substantial receptor internalization. These results suggest that long-term treatme nt with peptidic V-2 receptor antagonists might lead to desensitizatio n. (C) 1998 Academic Press.