Ca(2+)-signalling in human T-lymphocytes. Potential roles for cyclic ADP-ribose and 2'-phospho-cyclic ADP-ribose.

Intracellular Ca(2+)-signals belong to the major events transducing extracellular signals into living cells. The discovery of (i) a caffeine-sensitive intracellular Ca(2+)-pool in Jurkat T-lymphocytes [1] and (ii) cyclic adenosine diphosphoribose (cADPR) as an agent that mobilizes Ca2+ from a caffeine- and ryanodine sensitive Ca(2+)-store in sea urchin egg homogenates [2] prompted us to investigate the potential role of this compound in T-lymphocyte Ca(2+)-signalling. cADPR, as well as its 2'-phosphorylated derivative, 2'-phospho-cADPR (2'-cADPR), released Ca2+ in a dose-dependent, specific manner from intracellular, non-endoplasmic reticular stores of permeabilized Jurkat and HPB.ALL T cells. In addition, attempts were made to prove the presence of endogenous cADPR and 2'-P-cADPR by HPLC. Several HPLC protocols, including microbore-HPLC were tested resulting in the detection of endogenous cADPR by sequential separation on strong-anion exchange HPLC and reverse-phase ion-pair HPLC.