| Summary: | Transient receptor potential melastatin 2 (TRPM2), is a ligand-gated Ca2+-permeable non19 selective cation channel. While physiological stimuli, e.g. chemotactic agents, evoke controlled Ca2+ signals via TRPM2, pathophysiological signals, such as reactive oxygen species or genotoxic stress result in prolonged TRPM2-mediated Ca2+ entry and consequently apoptosis. To date, adenosine 5ʹ-diphosphoribose (ADPR, 1) has been assumed to be the main agonist for TRPM2. Here, we show that 2ʹ-deoxy-ADPR 2 was a significantly better TRPM2 agonist, inducing 10.4-fold 24 higher whole cell currents at saturation. Mechanistically, this increased activity was caused by decreased rate of inactivation and higher average open probability. Using high performance liquid chromatography (HPLC) and mass spectrometry, endogenous 2ʹ-deoxy-ADPR was detected in Jurkat T-lymphocytes. Consistently, cytosolic nicotinamide mononucleotide adenylyltransferase 2 (NMNAT-2) and nicotinamide adenine dinucleotide (NAD)-glycohydrolase CD38 sequentially catalyzed synthesis of 2ʹ-deoxy- ADPR from nicotinamide mononucleotide and 2ʹ-deoxy-ATP in vitro. Thus, 2ʹ-deoxy-ADPR is an endogenous TRPM2 superagonist that may act as cell signaling molecule.
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