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Cell Signal. 2004 Nov;16(11):1283-9.

Ca2+ release via ryanodine receptors and Ca2+ entry: major mechanisms in NAADP-mediated Ca2+ signaling in T-lymphocytes.

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Institute of Biochemistry and Molecular Biology I: Cellular Signal Transduction, University Hospital Hamburg-Eppendorf, Center of Experimental Medicine, Martinistr. 52, D-20246, Germany.


Nicotinic acid adenine dinucleotide phosphate (NAADP) is a potent Ca2+ mobilizing nucleotide essentially involved in T cell activation. Using combined microinjection and single cell calcium imaging, we demonstrate that co-injection of NAADP and the D-myo-inositol 1,4,5-trisphosphate antagonist heparin did not inhibit Ca2+ mobilization. In contrast, co-injection of the ryanodine receptor antagonist ruthenium red efficiently blocked NAADP induced Ca2+ signalling. This pharmacological approach was confirmed using T cell clones stably transfected with plasmids expressing antisense mRNA targeted specifically against ryanodine receptors. NAADP induced Ca2+ signaling was strongly reduced in these clones. In addition, inhibition of Ca2+ entry by SK&F 96365 resulted in a dramatically decreased Ca2+ signal upon NAADP injection. Gd3+, a known blocker of Ca2+ release activated Ca2+ entry, only partially inhibited NAADP mediated Ca2+ signaling. These data indicate that in T cells (i) ryanodine receptor are the major intracellular Ca2+ release channels involved in NAADP induced Ca2+ signals, and that (ii) such Ca2+ release events are largely amplified by Ca2+ entry.

[Indexed for MEDLINE]

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