Functional Ryanodine Receptor Expression Is Required for NAADP-mediated Local Ca2+ Signaling in T-lymphocytes*

W. Dammermann,A. Guse

Published 2005 in Journal of Biological Chemistry

ABSTRACT

Nicotinic acid adenine dinucleotide phosphate (NAADP) is a potent Ca2+-mobilizing nucleotide involved in T cell Ca2+ signaling (Berg, I., Potter, B. V. L., Mayr, G. W., and Guse, A. H. (2000) J. Cell Biol. 150, 581–588). The objective of this study was to analyze whether the first subcellular Ca2+ signals obtained upon NAADP stimulation of T-lymphocytes depend on the functional expression of ryanodine receptors. Using combined microinjection and high resolution confocal calcium imaging, we demonstrate here that subcellular Ca2+ signals, characterized by amplitudes between ∼30 and 100 nm and diameters of ∼0.5 μm, preceded global Ca2+ signals. Co-injection of the ryanodine receptor antagonists ruthenium red and ryanodine together with NAADP abolished the effects of NAADP, whereas the d-myo-inositol 1,4,5-trisphosphate antagonist heparin and the Ca2+ entry blocker SKF&96365 were without effect. This pharmacological approach was confirmed by a molecular knock-down approach. Jurkat T cell clones with largely reduced expression of ryanodine receptors did not respond to microinjections of NAADP. Taken together, our data suggest that the Ca2+ release channel sensitive to NAADP in T-lymphocytes is the ryanodine receptor.

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