Activation of the cation channel long transient receptor potential channel 2 (LTRPC2) by hydrogen peroxide -: A splice variant reveals a mode of activation independent of ADP-ribose

LTRPC2 is a cation channel recently reported to be activated by adenosine diphosphate-ribose (ADP-ribose) and NAD. Since ADP-ribose can be formed from NAD and NAD is elevated during oxidative stress, we studied whole cell currents and increases in the intercellular free calcium concentration ([Ca2+](i)) in long transient receptor potential channel 2 (LTRPC2)-transfected HEK 293 cells after stimulation with hydrogen peroxide (H2O2). Cation currents carried by monovalent cations and Ca2+ were induced by H2O2 (5 mm in the bath solution) as well as by intracellular ADP-ribose (0.3 mm in the pipette solution) but not by NAD (1 mm). H2O2-induced currents developed slowly after a characteristic delay of 3-6 min and receded after wash-out of H2O2. [Ca2+](i) was rapidly increased by H2O2 in LTRPC2-transfected cells as well as in control cells; however, in LTRPC2-transfected cells, H2O2 evoked a second delayed rise in [Ca2+](i). A splice variant of LTRPC2 with a deletion in the C terminus (amino acids 1292-1325) was identified in neutrophil granulocytes. This variant was stimulated by H2O2 as the wild type. However, it did not respond to ADP-ribose. We conclude that activation of LTRPC2 by H2O2 is independent of ADP-ribose and that LTRPC2 may mediate the influx of Na+ and Ca2+ during oxidative stress, such as the respiratory burst in granulocytes.