Downregulation of vasopressin V2receptor promoter activity via V1areceptor pathway

Abstract

Vasopressin V1aand V2receptors (V1aR and V2R, respectively) distribute in the collecting duct of the kidney. Although the function of V2R mediating the antidiuretic effect of AVP has been investigated in detail, the role of V1aR in the collecting ducts has not been elucidated. In the present study, we have investigated the role of the V1aR pathway in V2R promoter activity. We cloned the 5′-flanking region of rat V2R (rV2R) and investigated rV2R promoter activity in the LLC-PK1cell line transfected to express rat V1aR (rV1aR) dominantly (LLC-PK1/rV1aR). AVP induced a transient increase, followed by a sustained decrease, of rV2R promoter activity in these cells. This AVP-induced decrease of rV2R promoter activity was inhibited by V1aR, but not V2R, antagonist. PMA mimicked this decrease of rV2R promoter activity. On the contrary, 8-(4-chlorophenylthio)-cAMP increased rV2R promoter activity. These PMA- and 8-(4-chlorophenylthio)-cAMP-induced effects were not observed on the deletion segment of the 5′-flanking region lacking CAAT and SP1 sites. In conclusion, 1) expression of the V2R is downregulated via the V1aR pathway in LLC-PK1/rV1aR cells, and 2) expression of the V2R is downregulated by the PMA-induced PKC pathway and upregulated by the cAMP-PKA pathway. These opposite effects of PKC and PKA appear to be regulated by the same promoter region of CAAT and SP1.