Agonist and antagonist-dependent internalization of the human vasopressin V2 receptor

In this report we demonstrate that in HEK293 cells stably expressing the human V-2 vasopressin receptor, ligand-induced internalization of the hormone receptor occurs via the clathrin-dependent pathway. Studies of receptor trafficking either by direct visualization of the V-2 receptor by confocal microscopy or binding experiments show a rapid internalization (half-time 6-7 min), Blocking of the clathrin-dependent pathway by hypertonic sucrose increased vasopressin-induced cellular cAMP production and decreased the desensitization of the V-2 receptor-adenylyl cyclase system. Thus, internalization appears to be a major regulatory mechanism terminating vasopressin action in HEK293 cells. Two antagonists of the vasopressin V-2 receptor exerted different effects on receptor internalization, as determined by confocal fluorescence microscopy, 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 treatment with peptidic V-2 receptor antagonists might lead to desensitization. (C) 1998 Academic Press.