Novel Hydrolysis-Resistant Analogues of Cyclic ADP-ribose:  Modification of the “Northern” Ribose and Calcium Release Activity

Abstract

Three novel analogues modified in the "northern" ribose (ribose linked to N1 of adenine) of the Ca(2+) mobilizing second messenger cyclic adenosine diphosphoribose, termed 2"-NH(2)-cyclic adenosine diphosphoribose, cyclic adenosine diphospho-carbocyclic-ribose, and 8-NH(2)-cyclic adenosine diphospho-carbocyclic-ribose, were synthesized (chemoenzymatically and by total synthesis) and spectroscopically characterized, and the pK(a) values for the 6-amino/imino transition were determined in two cases. The biological activity of these analogues was determined in permeabilized human Jurkat T-lymphocytes. 2"-NH(2)-cyclic adenosine diphosphoribose mediated Ca(2+) release was slightly more potent than that of the endogenous cyclic adenosine diphosphoribose in terms of the concentration-reponse relationship. Both compounds released Ca(2+) from the same intracellular Ca(2+) pool. In addition, the control compound 2"-NH(2)-adenosine diphosphoribose was almost without effect. In contrast, only at much higher concentrations (> or =50 microM) did the "northern" carbocyclic analogue, cyclic adenosine diphospho-carbocyclic-ribose, significantly release Ca(2+) from permeabilized T cells, whereas the previously reported "southern" carbocyclic analogue, cyclic aristeromycin diphosphoribose, was slightly more active than the endogenous cyclic adenosine diphosphoribose. Likewise, 8-NH(2)-cyclic adenosine diphospho-carbocyclic-ribose, expected to antagonize Ca(2+) release as demonstrated previously for 8-NH(2)-cyclic adenosine diphosphoribose, did not inhibit cyclic adenosine diphosphoribose mediated Ca(2+) release. This indicates that the 2"-NH(2)-group substitutes well for the 2"-OH-group it replaces; it may be oriented toward the outside of the putative cyclic adenosine diphosphoribose receptor binding domain and/or it can potentially also engage in H bonding interactions with residues of that domain. In sharp contrast to this, replacement of the endocyclic furanose oxygen atom by CH(2) in a carbocyclic system obviously interferes with a crucial element of interaction between cyclic adenosine diphosphoribose and its receptor in T-lymphocytes.

Cyclic ADP-Carbocyclic-Ribose and -4-Thioribose, as Stable Mimics of Cyclic ADP-Ribose, a Ca²⁺-Mobilizing Second Messenger

“…However, to our surprise, it was inactive in T cells, whereas natural cADPR effectively mobilizes Ca 2+ in both neuronal cells and T cells. 34) These results confirmed that the target proteins and/or the mechanism of action of cADPR in sea urchin eggs, T cells, and neuronal cells are different, 35) as suggested by previous biological studies. [36][37][38][39][40][41][42] …”

Cyclic ADP‐Ribose Analogues with Minimal Structure: Synthesis and Calcium‐Release Activity

“…In contrast, in mammalian cells, cADPcR acted much more weakly as compared to the sea urchin system (Guse et al, 2002). However, it was found that cIDPcR showed only an insignificant Ca 2þ -mobilizing effect (EC 50 > 10 6 mM), and 8-BrcIDPcR was almost inactive in sea urchin egg homogenates (Shuto and Matsuda, 2004).…”

A Minimal Structural Analogue of Cyclic ADP-ribose

“…Permeabilized Jurkat T cells were prepared as detailed previously (14). In brief, cells were transferred into an intracellular medium (nominally Ca 2ϩ -free, pH 7.2), permeabilized with 55 mg/ml saponin for 20 min, and afterward washed three times to remove all saponin.…”

“…O-Methylation of the 3Ј-hydroxyl group generated an antagonist (12). The stable carbocyclic derivative cyclic aristeromycin diphosphoribose was an agonist in both sea urchin eggs and T lymphocytes (13,14). To further explore the structure-activity relationship of cADPR in mammalian cells, we replaced both the southern and northern ribose moieties of cIDPR with ether strands.…”