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Modulation of NAADP (nicotinic acid-adenine dinucleotide phosphate) receptors by K+ ions: evidence for multiple NAADP receptor conformations

Dickinson, GD; Patel, S; (2003) Modulation of NAADP (nicotinic acid-adenine dinucleotide phosphate) receptors by K+ ions: evidence for multiple NAADP receptor conformations. BIOCHEM J , 375 805 - 812. 10.1042/BJ20030672.

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Abstract

NAADP (nicotinic acid-adenine dinucleotide phosphate) mediates Ca2+ release from intracellular Ca2+ stores in a wide variety of cell types. In sea urchin eggs, subthreshold concentrations of NAADP can cause full inactivation of NAADP-induced Ca2+ release, an effect that may be related to the ability of the target protein to bind its ligand in an essentially irreversible manner. In the present study, we found that K+ ions inhibit dissociation of NAADP from sea urchin egg homogenates. In low K+-containing media, an addition of excess unlabelled NAADP effectively displaced bound radioligand whereas dilution of radioligand initiated only partial dissociation. The inhibitory effects of K+ on dissociation of NAADP were concentration dependent, reversible and persisted after detergent solubilization. Lowering [K+] of the medium decreased the sensitivity of NAADP receptors for their ligand in stimulating Ca2+ release, but it did not affect inactivation of NAADP-induced Ca2+ release by subthreshold concentrations of NAADP. Our results are consistent with the observation of multiple conformations of the NAADP receptor that are readily revealed in low K+-containing media.

Type: Article
Title: Modulation of NAADP (nicotinic acid-adenine dinucleotide phosphate) receptors by K+ ions: evidence for multiple NAADP receptor conformations
DOI: 10.1042/BJ20030672
Keywords: NAADP, calcium, sea urchin, desensitization, fertilization, SEA-URCHIN EGGS, INDUCED CA2+ RELEASE, CYCLIC ADP-RIBOSE, PANCREATIC BETA-CELLS, CA2+-MOBILIZING MESSENGER, INOSITOL TRISPHOSPHATE, MOBILIZES CA2+, APOPTOSIS, STORES, INACTIVATION
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences > Div of Biosciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences > Div of Biosciences > Cell and Developmental Biology
URI: http://discovery.ucl.ac.uk/id/eprint/185562
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