NAADP mobilizes calcium from the endoplasmic reticular Ca(2+) store in T-lymphocytes.
The target calcium store of nicotinic acid adenine dinucleotide phosphate (NAADP), the most potent endogenous calcium-mobilizing compound known to date, has been proposed to reside in the lysosomal compartment or in the endo/sarcoplasmic reticulum. This study was performed to test the hypothesis of a lysosomal versus an endoplasmic reticular calcium store sensitive to NAADP in T-lymphocytes. Pretreatment of intact Jurkat T cells with glycyl-phenylalanine 2-naphthylamide largely reduced staining of lysosomes by LysoTracker Red and abolished NAADP-induced Ca(2+) signaling. However, the inhibitory effect was not specific since Ca(2+) mobilization by d-myo-inositol 1,4,5-trisphosphate and cyclic ADP-ribose was abolished, too. Bafilomycin A1, an inhibitor of the lysosomal H(+)-ATPase, did not block or reduce NAADP-induced Ca(2+) signaling, although it effectively prevented labeling of lysosomes by LysoTracker Red. Further, previous T cell receptor/CD3 stimulation in the presence of bafilomycin A1, assumed to block refilling of lysosomal Ca(2+) stores, did not antagonize subsequent NAADP-induced Ca(2+) signaling. In contrast to bafilomycin A1, emptying of the endoplasmic reticulum by thapsigargin almost completely prevented Ca(2+) signaling induced by NAADP. In conclusion, in T-lymphocytes, no evidence for involvement of lysosomes in NAADP-mediated Ca(2+) signaling was obtained. The sensitivity of NAADP-induced Ca(2+) signaling toward thapsigargin, combined with our recent results identifying ryanodine receptors as the target calcium channel of NAADP (Dammermann, W., and Guse, A. H. (2005) J. Biol. Chem. 280, 21394-21399), rather suggest that the target calcium store of NAADP in T cells is the endoplasmic reticulum.
Steen
Mareike
M
Calcium Signaling Group, University Medical Centre Hamburg-Eppendorf, Centre of Experimental Medicine, Institute of Biochemistry and Molecular Biology I, Cellular Signal Transduction, Martinistrasse 52, D-20426 Hamburg, Germany.
Kirchberger
Tanja
T
Guse
Andreas H
AH
D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects / Q000276:immunology*; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D019169:Jurkat Cells; D008247:Lysosomes / Q000378:metabolism; D018942:Macrolides / Q000494:pharmacology; D009249:NADP / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D013601:T-Lymphocytes / Q000187:drug effects* / Q000378:metabolism*; D019284:Thapsigargin / Q000494:pharmacology
D004791:Enzyme Inhibitors; D018942:Macrolides; D009249:NADP; C024376:NAADP; D019284:Thapsigargin; C040929:bafilomycin A1; D002118:Calcium