Work

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

Year: 2003

Type: article

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.

Source: Biochemical Journal

DOI: 10.1042/bj20030672

Authors: George D. DICKINSON, Sandip PATEL

Institution: University College London

Language: English

Topic: Calcium signaling and nucleotide metabolism

Subfield: Physiology

Field: Biochemistry, Genetics and Molecular Biology

Domain: Life Sciences

Open Access status: bronze

Funders: Wellcome Trust, University College London, Universität Hamburg

OpenAlex ID: W1994577418