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 CA(2+)-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 (IC(50) about 1 microM). 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.