Unique mode of binding between angiotensin II type 1 receptor and its blockers

ABSTRACT

BACKGROUND: We hypothesized that the 5-oxo-1,2,4-oxadiazole moiety of azilsartan (AZL), which represents a small difference in the molecular structures of AZL and candesartan (CAN) [angiotensin II type 1 receptor (AT₁R) blockers], may be responsible for the molecular effects of AZL. METHODS: We examined the binding affinities of AZL and CAN to AT₁R, along with their ability to block receptor activity. A competition binding study, inositol phosphate (IP) production assay and extracellular signal-regulated kinase (ERK) assay were performed using wild-type (WT) and mutants AT₁R-transfected cells. RESULTS: The binding affinities of CAN and AZL were reduced by > 5-fold for Y35F, W84F, R167K, K199Q and I288A compared with WT. In addition, AZL showed a > 5-fold reduction in its binding affinity to V108A. CAN and AZL exhibited > 20-fold and > 100-fold reductions in binding affinity to R167K, respectively. The loss of binding affinity of AZL to R167K was greater than that of CAN. CAN-7H exhibited a > 10-fold reduction in binding affinity to R167K compared with CAN. On the other hand, the binding affinity of AZL-7H to R167K was comparable to that of AZL. While 10^-6M CAN and CAN-7H partly blocked Ang II-induced IP production in R167K, 10^-6M AZL and AZL-7H did not. In addition, 10^-6M CAN, but not 10^-6M AZL, partly blocked Ang II-induced ERK activation in R167K. CONCLUSIONS: The interaction between 5-oxo-1,2,4-oxadiazole in AZL and Arg¹⁶⁷ in the AT1R appears to be more important than the interaction between the tetrazole ring in CAN and Arg¹⁶⁷.

KEYWORDS:

• 5-oxo-1-oxadiazole
• azilsartan
• candesartan
• Arg¹⁶⁷

Conflict of Interest

S.M. has received grants and lecture honoraria from Takeda Pharmaceutical Co. Ltd. S.M. is a Director of NPO Clinical and Applied Science, Fukuoka, Japan. S.M. belongs to the Department of Molecular Cardiovascular Therapeutics, which is supported by MSD, Co. LTD.

Additional information

Funding

This work was supported by a Grant-in-Aid for Scientific Research (No. 20343709) from the Ministry of Education, Culture, Sports, Science and Technology of Japan to S.M.The Ministry of Education, Culture, Sports, Science and Technology of Japan [No. 20343709].