DTNB oxidation effects on T-type Ca²⁺channel isoforms

Redox regulation is one of the ubiquitous mechanisms to modulate ion channels. We here investigated how 5,5′-dithio-bis (2-nitrobenzoic acid), a cysteine specific oxidizing reagent, modulates Cav3.1 and Cav3.2 T-type Ca2 + channels expressed in Xenopus oocytes. Application of the reagent inhibited Cav3.1 and Cav3.2 currents in a dose-dependent manner. The oxidizing reagent (1 mM) reduced the peak amplitude of Cav3.1 and Cav3.2 currents by ~50% over 2–3 minutes and the decreased currents were fully recovered upon washout of it. The reagent slowed the activation and inactivation kinetics of Cav3.1, Cav3.2, and Cav3.3 channel currents. Notably, the reagent positively shifted both activation and steady-state inactivation curves of Cav3.1, while it did not those of Cav3.2. Utilizing chimeric channels from Cav3.1 and Cav3.2, we localized the domains III and IV of Cav3.1 responsible for the positive shifts of channel activation and steady-state inactivation. These findings provide hints relevant to the electrophysiological and molecular mechanisms accounting for the oxidative regulation of T-type channels.