ORAI1, STIM1/2, and RYR1 shape subsecond Ca microdomains upon T cell activation.

The earliest intracellular signals that occur after T cell activation are local, subsecond Ca microdomains. Here, we identified a Ca entry component involved in Ca microdomain formation in both unstimulated and stimulated T cells. In unstimulated T cells, spontaneously generated small Ca microdomains required ORAI1, STIM1, and STIM2.

2'-Deoxyadenosine 5'-diphosphoribose is an endogenous TRPM2 superagonist.

Transient receptor potential melastatin 2 (TRPM2) is a ligand-gated Ca-permeable nonselective cation channel. Whereas physiological stimuli, such as chemotactic agents, evoke controlled Ca signals via TRPM2, pathophysiological stimuli such as reactive oxygen species and genotoxic stress result in prolonged TRPM2-mediated Ca entry and, consequently, apoptosis. To date, adenosine 5'-diphosphoribose (ADPR) has been assumed to be the main agonist for TRPM2.