In this study, in order to evaluate the structural characteristics of the vasopressin receptor, it was tried to construct the V2-V1 chimeric vasopressin receptor and to compare its pharmacological natures to the natural receptors.
The 2nd and 3rd extracellular loop of V2 receptor was substituted to that of V1ｂ receptor using polymerase chain reaction(PCR) and the changes in binding affinity of vasopressin as well as the changes in intracytosolic effector pathways were observed.
The V2-V1 chimeric receptor showed a greatly decreased hormone binding affinity compared to that of natural receptors(3% of the V2 receptor and 10% of the V1ｂ receptor) and also completely lost the intracellular effect to produce cAMP in transfected COS-7 cells. On the while, the chimeric receptor still reserved the ability to produce IP3 inside the COS-7 cells(35% of V1ｂ receptor), which indicates that the effector pathway for IP3 production is still available in chimeric receptor.
These results suggest that binding of vasopressin to its receptor is determined not by the specific partial amino acid sequence, but by the entire extracellualr protein structure of the receptor. Also suggested is that binding of vasopressin receptor to G protein is governed mainly by the 2nd or 3rd intracytosolic loop structure. These studies could contribute to the development of antagonistic pharmaceuticals , which will act as antihypertensive or antidiuretics, through the evaluation of structural characteristics of vasopressin receptor.
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