Inhibition of the transient receptor potential cation channel TRPM2 by 2-aminoethoxydiphenyl borate (2-APB)

Background and purpose: Transient receptor potential melastatin 2 (TRPM2) is a non-selective Ca2+ -permeable cation channel and is known to be activated by adenosine 5'-diphosphoribose ( ADP-ribose) and hydrogen peroxide. TRPM2 current responses are reported to be drastically potentiated by the combination of each of these ligands with heat. Furthermore, the combination of cyclic ADP-ribose with heat also activates TRPM2. Although flufenamic acid, antifungal agents ( miconazole and clotrimazole), and a phospholipase A(2) inhibitor (N-(p-amylcinnamoyl) anthranilic acid) inhibit TRPM2, their inhibition was either gradual or irreversible. Experimental approach: To facilitate future research on TRPM2, we screened several compounds to investigate their potential to activate or inhibit the TRPM2 channels using the patch-clamp technique in HEK293 cells, transfected with human TRPM2. Key results: 2-aminoethoxydiphenyl borate (2-APB) exhibited a rapid and reversible inhibition of TRPM2 channels that had been activated by its ADP-ribose or cADP-ribose and heat in a dose-dependent manner (IC50 about 1 mu M). 2-APB also inhibited heat-evoked insulin release from pancreatic islets, isolated from rats. Conclusions and implications: 2-APB proved to be a powerful and effective tool for studying the function of TRPM2.