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Ectocellular CD38‐catalyzed synthesis and intracellular Ca 2+ ‐signalling activity of cyclic ADP‐ribose in T‐lymphocytes are not functionally related
Author(s) -
da Silva Cristina P,
Schweitzer Katrin,
Heyer Petra,
Malavasi Fabio,
Mayr Georg W,
Guse Andreas H
Publication year - 1998
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(98)01396-9
Subject(s) - cyclic adp ribose , intracellular , cd38 , nad+ kinase , cyclase , biochemistry , chemistry , microbiology and biotechnology , biology , enzyme , stem cell , cd34
Cyclic ADP‐ribose (cADPR) is a natural metabolite of β‐NAD + with a potent Ca 2+ ‐mobilizing activity in different cell types, including T‐lymphocytes. We investigated (i) whether stimulation of T‐lymphocytes with different agonists affects the intracellular concentration of cADPR, and (ii) whether the lymphocyte antigen CD38, through its ectocellular ADP‐ribosyl cyclase and cADPR‐hydrolase enzymatic activities, can account for the regulation of the intracellular levels of cADPR and the Ca 2+ ‐mobilizing effects of this nucleotide in Jurkat and HPB.ALL T‐lymphocytes. The anti‐CD3 antibody OKT3, the sphingolipid sphingosine and lysophosphatidic acid induced an increase in intracellular cADPR with concomitant increases in the intracellular Ca 2+ concentration ([Ca 2+ ] i ). In contrast, activation of an ectocellular ADP‐ribosyl cyclase by preincubation of cells with β‐NAD + led to a dose‐dependent increase in cADPR, but no changes in [Ca 2+ ] i were observed. However, extensive washing of the cells following preincubation with NAD + demonstrated that the increases in cADPR were not intracellular but due to cell surface‐associated nucleotide. Accordingly, measurements of ADP‐ribosyl cyclase activity in intact T‐cells showed ectocellular synthesis of cADPR, but no evidence was obtained for a shift of this activity into the cells which could account for intracellular accumulation of cADPR. Taken together, the results indicate no direct involvement of the ADP‐ribosyl cyclase activity of CD38 on the regulation of the cADPR‐mediated intracellular Ca 2+ ‐signalling in T‐lymphocytes.