Synthesis of stable and cell-type selective analogues of cyclic ADP-ribose, a Ca(2+)-mobilizing second messenger. Structure--activity relationship of the N1-ribose moiety.
Kudoh T., Fukuoka M., Ichikawa S., Murayama T., Ogawa Y., Hashii M., Higashida H., Kunerth S., Weber K., Guse AH., Potter BV., Matsuda A., Shuto S.
We previously developed cyclic ADP-carbocyclic ribose (cADPcR, 2) as a stable mimic of cyclic ADP-ribose (cADPR, 1), a Ca(2+)-mobilizing second messenger. A series of the N1-ribose modified cADPcR analogues, designed as novel stable mimics of cADPR, which were the 2"-deoxy analogue 3, the 3"-deoxy analogue 4, the 3"-deoxy-2"-O-(methoxymethyl) analogue 5, the 3"-O-methyl analogue 6, the 2",3"-dideoxy analogue 7, and the 2",3"-dideoxydidehydro analogue 8, were successfully synthesized using the key intramolecular condensation reaction with phenylthiophosphate-type substrates. We investigated the conformations of these analogues and of cADPR and found that steric repulsion between both the adenine and N9-ribose moieties and between the adenine and N1-ribose moieties was a determinant of the conformation. The Ca(2+)-mobilizing effects were evaluated systematically using three different biological systems, i.e., sea urchin eggs, NG108-15 neuronal cells, and Jurkat T-lymphocytes. The relative potency of Ca(2+)-mobilization by these cADPR analogues varies depending on the cell-type used: e.g., 3"-deoxy-cADPcR (4) > cADPcR (2) > cADPR (1) in sea urchin eggs; cADPR (1) > cADPcR (2) approximately 3"-deoxy-cADPcR (4) in T-cells; and cADPcR (2) > cADPR (1) > 3"-deoxy-cADPcR (4) in neuronal cells, respectively. These indicated that the target proteins and/or the mechanism of action of cADPR in sea urchin eggs, T-cells, and neuronal cells are different. Thus, this study represents an entry to cell-type selective cADPR analogues, which can be used as biological tools and/or novel drug leads.