TY - JOUR
T1 - Synthesis and characterization of antagonists of cyclic-ADP-ribose-induced Ca2+ release
AU - Walseth, Timothy F.
AU - Lee, Hon Cheung
PY - 1993/9/13
Y1 - 1993/9/13
N2 - Cyclic ADP-ribose (cADPR) is a naturally-occurring metabolite of NAD+ that is as effective as inositol trisphosphate in mobilizing intracellular Ca2+. A series of analogs modified at the 8-position of the adenine group were synthesized for the investigation of the relationship between the structure of the metabolite and its Ca2+-mobilizing activity. Substitution with an amino group at the 8-position of the adenine ring produced an antagonist. The 1H-NMR spectrum of 8-amino-cADPR showed characteristics of that of cADPR and confirmed the replacement of the 8-proton. By itself, 8-amino-cADPR (150 nM) did not induce Ca2+ release from sea-urchin-egg homogenates but totally blocked cADPR (135 nM) from doing so. The effect was reversible, since high concentrations of cADPR could overcome the inhibition. Addition of 8-amino-cADPR to egg homogenates during the cADPR-induced Ca2+ release blocked the release immediately, demonstrating the effectiveness of the antagonist. Measurements of [32P]cADPR binding to its microsomal binding site showed that 8-amino-cADPR was as effective as cADPR itself in competing for the binding site. In addition to blocking cADPR from releasing Ca2+, 8-amino-cADPR also inhibited cADPR from potentiating Ca2+-release induced by either divalent cations or by caffeine. Two other 8-substituted analogs were also synthesized. Both 8-Br- and 8-azido-cADPR were also antagonists, although with less potency than 8-amino-cADPR. These results show that alterations at the 8-position of the adenine group do not inhibit cADPR from binding to its receptor but do eliminate the ability of the metabolite to activate the Ca2+-release mechanism.
AB - Cyclic ADP-ribose (cADPR) is a naturally-occurring metabolite of NAD+ that is as effective as inositol trisphosphate in mobilizing intracellular Ca2+. A series of analogs modified at the 8-position of the adenine group were synthesized for the investigation of the relationship between the structure of the metabolite and its Ca2+-mobilizing activity. Substitution with an amino group at the 8-position of the adenine ring produced an antagonist. The 1H-NMR spectrum of 8-amino-cADPR showed characteristics of that of cADPR and confirmed the replacement of the 8-proton. By itself, 8-amino-cADPR (150 nM) did not induce Ca2+ release from sea-urchin-egg homogenates but totally blocked cADPR (135 nM) from doing so. The effect was reversible, since high concentrations of cADPR could overcome the inhibition. Addition of 8-amino-cADPR to egg homogenates during the cADPR-induced Ca2+ release blocked the release immediately, demonstrating the effectiveness of the antagonist. Measurements of [32P]cADPR binding to its microsomal binding site showed that 8-amino-cADPR was as effective as cADPR itself in competing for the binding site. In addition to blocking cADPR from releasing Ca2+, 8-amino-cADPR also inhibited cADPR from potentiating Ca2+-release induced by either divalent cations or by caffeine. Two other 8-substituted analogs were also synthesized. Both 8-Br- and 8-azido-cADPR were also antagonists, although with less potency than 8-amino-cADPR. These results show that alterations at the 8-position of the adenine group do not inhibit cADPR from binding to its receptor but do eliminate the ability of the metabolite to activate the Ca2+-release mechanism.
KW - (S. purpuratus)
KW - (Sea urchin egg)
KW - 8-Amino-cyclic ADP-ribose
KW - Calcium ion mobilization
KW - Calcium ion release antagonist
KW - Microsome
KW - cyclic ADP-ribose
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U2 - 10.1016/0167-4889(93)90199-Y
DO - 10.1016/0167-4889(93)90199-Y
M3 - Article
C2 - 8395888
AN - SCOPUS:0027313269
VL - 1178
SP - 235
EP - 242
JO - Biochimica et Biophysica Acta - Molecular Cell Research
JF - Biochimica et Biophysica Acta - Molecular Cell Research
SN - 0167-4889
IS - 3
ER -