Activation of T cell calcium influx by the second messenger ADP-ribose.

Stimulation of Jurkat T cells by high concentrations of concanavalin A (ConA) induced an elevation of the endogenous adenosine diphosphoribose (ADPR) concentration and an inward current significantly different from the Ca2+ release-activated Ca2+ current (I(CRAC)). Electrophysiological characterization and activation of a similar current by infusion of ADPR indicated that the ConA-induced current is carried by TRPM2. Expression of TRPM2 in the plasma membrane of Jurkat T cells was demonstrated by reverse transcription-PCR, Western blot, and immunofluorescence. Inhibition of ADPR formation reduced ConA-mediated, but not store-operated, Ca2+ entry and prevented ConA-induced cell death of Jurkat cells. Moreover, gene silencing of TRPM2 abolished the ADPR- and ConA-mediated inward current. Thus, ADPR is a novel second messenger significantly involved in ConA-mediated cell death in T cells.