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5-Azido-8-ethynyl-NAADP: A bifunctional, clickable photoaffinity probe for the identification of NAADP receptors. Biochim Biophys Acta Mol Cell Res 2019 07;1866(7):1180-1188



Pubmed ID




Scopus ID

2-s2.0-85057588907   3 Citations


Nicotinic acid adenine dinucleotide phosphate is an evolutionarily conserved second messenger, which mobilizes Ca2+ from acidic stores. The molecular identity of the NAADP receptor has yet to be defined. In pursuit of isolating and identifying NAADP-binding proteins, we synthesized and characterized a bifunctional probe that incorporates both a photoactivatable crosslinking azido moiety at the 5-position of the nicotinic ring and a 'clickable' ethynyl moiety to the 8-adenosyl position in NAADP. Microinjection of this 5N3-8-ethynyl-NAADP into cultured U2OS cells induced robust Ca2+ responses. Higher concentrations of 5N3-8-ethynyl were required to elicit Ca2+ release or displace 32P-NAADP in radioligand binding experiments in sea urchin egg homogenates. In human cell extracts, incubation of 32P-5N3-8-ethynyl-NAADP followed by UV irradiation resulted in selective labeling of 23 kDa and 35 kDa proteins and photolabeling of these proteins was prevented when incubated in the presence of unlabeled NAADP. Compared to the monofunctional 32P-5N3-NAADP, the clickable 32P-5N3-8-ethynyl-NAADP demonstrated less labeling of the 23 kDa and 35 kDa proteins (~3-fold) but provided an opportunity for further enrichment through the 'clickable' ethynyl moiety. No proteins were specifically labeled by 32P-5N3-8-ethynyl-NAADP in sea urchin egg homogenate. These experiments demonstrate that 5N3-8-ethynyl-NAADP is biologically active and selectively labels putative NAADP-binding proteins in mammalian systems, evidencing a 'bifunctional' probe with utility for isolating NAADP-binding proteins.

Author List

Gunaratne GS, Su P, Marchant JS, Slama JT, Walseth TF


Jonathan S. Marchant PhD Chair, Professor in the Cell Biology, Neurobiology and Anatomy department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Calcium Signaling
Cell Line, Tumor
Fluorescent Dyes
Sea Urchins
Staining and Labeling
Ultraviolet Rays
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