Role of the carboxyl-terminal region, di-leucine motif and cysteine residues in signalling and internalization of vasopressin V1a receptor

The structural requirements for internalization and signalling of the vasop ressin Via receptor were investigated in stably transfected HEK-293 cells. Removal of the 51 C-terminal amino acids did not affect vasopressin binding , calcium signalling, heterologous desensitization or internalization of th e receptor, Deletion of 14 additional amino acids reduced vasopressin-depen dent calcium increase and impaired receptor internalization. Substitution o f cysteines 371-372 did not affect intracellular signalling, but decreased endocytosis by 26%, Substitution of the 361-362 leucine by alanine residues reduced by 56% V1a receptor sequestration without affecting calcium signal ling, These results indicate that di-cysteine and mostly dileucine motifs p resent in the C-terminal region of the Via receptor are involved in its int ernalization. (C) 1999 Federation of European Biochemical Societies.