NAADP mobilizes Ca2+ from a thapsigargin-sensitive store in the nuclear envelope by activating ryanodine receptors

Abstract

Ca2+ release from the envelope of isolated pancreatic acinar nuclei could be activated by nicotinic acid adenine dinucleotide phosphate (NAADP) as well as by inositol 1,4,5-trisphosphate (IP3) and cyclic ADP-ribose (cADPR). Each of these agents reduced the Ca2+ concentration inside the nuclear envelope, and this was associated with a transient rise in the nucleoplasmic Ca2+ concentration. NAADP released Ca2+ from the same thapsigargin-sensitive pool as IP3. The NAADP action was specific because, for example, nicotineamide adenine dinucleotide phosphate was ineffective. The Ca2+ release was unaffected by procedures interfering with acidic organelles (bafilomycin, brefeldin, and nigericin). Ryanodine blocked the Ca2+-releasing effects of NAADP, cADPR, and caffeine, but not IP3. Ruthenium red also blocked the NAADP-elicited Ca2+ release. IP3 receptor blockade did not inhibit the Ca2+ release elicited by NAADP or cADPR. The nuclear envelope contains ryanodine and IP3 receptors that can be activated separately and independently; the ryanodine receptors by either NAADP or cADPR, and the IP3 receptors by IP3.

Involvement of P2X receptors in the NAD+-induced rise in [Ca2+]i in human monocytes

“…Suramin is highly active as a P2X 1 and weak or nearly inactive as a P2X 7 and P2X 4 receptor antagonist [28]. As seen in Fig.…”

“…The polyclonal goat anti-human P2X 1 receptor Ab (A-15, sc-31489), the goat IgG isotype (sc-2028), and the FITC-labeled donkey-anti-goat antibody (sc-2024) were from Santa Cruz Biotechnology (Heidelberg, Germany); the rabbit-anti-human P2X 4 receptor was from Alomone Labs (Jerusalem, Israel); the FITC-labeled goat anti-mouse antibody was from DiaMak (Leipzig, Germany); the IgG2b isotype, the anti-β-actin antibody (clone AC-74), and the POD-conjugated goat anti-mouse antibody were from Sigma-Aldrich (Taufkirchen, Germany); and the monoclonal mouse anti-human P2X 7 receptor Ab was kindly provided by GlaxoSmithKline (Harlow, UK).…”

“…4b) when applying periodate-oxATP, currently in use as an efficient P2X 7 receptor blocker [32]. In addition to KN62 and oxATP, we tested an anti-P2X 7 mAb which has been demonstrated to act as a selective antagonist of human P2X 7 receptors in several functional studies [33]. As seen in Fig.…”

“…cADPR, NAADP, and ADPR are involved in the regulation of cellular Ca 2+ homeostasis. While cADPR and NAADP trigger Ca 2+ -release from intracellular stores [5][6][7], ADPR controls calcium entry through the plasma membrane channel TRPM2 [8,9]. It is difficult to envision how cADPR and NAADP can function inside the cell if they are generated by ectoenzymes.…”

Gangliosides of the nuclear membrane: A crucial locus of cytoprotective modulation

“…The NE lumen is continuous with the ER intermembrane space and thus provides a luminal storage site for a significant portion of nuclear Ca 2þ [Petersen et al, 1998;Strubing and Clapham, 1999]. The INM contains a number of Ca 2þ -release mechanisms regulated by Ins(1,4,5)P 3 , cADPribose, and NAADP; activation of these results in Ca 2þ transfer from NE to nucleoplasm [Stehno-Bittel et al, 1995;Humbert et al, 1996;Gerasimenko et al, 2003]. The apparent ability of Ca 2þ to freely diffuse through the nuclear pore complexes under many (perhaps all) conditions has raised doubts concerning the possible existence of nuclear-cytosolic Ca 2þ gradients (for review: Gerasimenko and Gerasimenko, 2004).…”