Abstract
The vasopressin V2 receptor (V2R) belongs to the family of G protein-coupled receptors (GPCRs) and is expressed in the collecting duct of nephrons in kidneys. V2R is coupled with the Gs protein and its activation by vasopressin or AVP stimulates the production of cAMP to induce an antidiuretic effect. The V2 receptor is involved in many pathologies including renal cancer in which its expression is abnormal and therefore represents an interesting target. Studies have shown that the use of receptor antagonists such as OPC41061 or SR121463 inhibits the proliferation of human renal cancer cells and also tumor growth on in vivo models [Bolignano et al., 2010 ; Sinha et al., 2020]. However, these antagonists lack selectivity towards the V2 receptor and can induce side effects and are also hepatotoxic. Recently in the laboratory, we developed a new selective V2 receptor antagonist, Mambaquaretin-1 (MQ1) which is a green mamba venom toxin. This molecule has shown its effectiveness in mouse models with polycystic kidney disease, a proliferative disease associated with V2R [Ciolek et al., 2017]. This work consisted in evaluating the effect of Mambaquaretin-1 on human renal cancer cells in order to characterize a potential drug for this pathology. On different in vitro models of renal cancer, we demonstrated the presence of RNA of V2R, as well as the membrane protein using fluorescent MQ1 as a diagnostic tool [Published results - Droctové et al., 2020]. We characterized an inhibitory effect of MQ1 on cell proliferation and migration associated with a decrease of MAPK, positioning Mambaquaretin-1 as a pharmacological tool. Then on nude mouse models with xenografts of cancer cells, we validated its potential therapeutic effect. The structure-activity allowed us to characterize a new mutant MQ1-K39A with a higher affinity and consequently could be more interesting [Published results - Droctové et al., 2021]. In parallel, the analysis of the RNA seque nces of these cancer lines revealed the presence of a truncated variant of V2 receptor in addition to the canonical form. On classical cell models we demonstrated an inability of the truncated form to produce cAMP by stimulation with AVP, as well as a preferential intracellular expression. We also showed the formation of the Canonical V2R-Truncated V2R heterodimer detected only inside the cell, suggesting a possible retention of the Wild Type form and therefore a potential dominant-negative effect of the truncated variant. Our work allowed us to characterize a potential drug candidate, Mambaquaretin-1 for renal cancer, and identify a variant of the V2 receptor which could represent a new therapeutic target or a marker for this cancer.