Ca2+-Signalling in Human T-Lymphocytes. In: Haag F, Koch-nolte F, editors. ADP-Ribosylation in Animal Tissues. Boston: Springer US; 1997. pp. 431-6. [DOI: 10.1007/978-1-4419-8632-0_55]

Bioorganic chemistry of cyclic ADP-ribose (cADPR)

The objective of this brief review is to present an overview of the bioorganic chemistry of cyclic-ADP-ribose (cADPR) with special emphasis on the methodology used for the synthesis of analogues of cADPR. New structural analogues of cADPR can be prepared using either the biomimetic method or ADP-ribosyl cyclase from Aplysia californica. For the most part, both procedures give similar product profiles, but higher yields are generally obtained with the enzymatic method. These synthetic methodologies have allowed the transformation of a variety of structurally modified analogues of NAD+ into their corresponding cyclic nucleotides. Several of these novel analogues are more potent than cADPR in inducing calcium release and are also more stable towards degradative enzymes. They could serve as valuable affinity probes for the isolation of cADPR-binding proteins.

Differential regulation of human neutrophil FcgammaRIIa (CD32) and FcgammaRIIIb (CD16)-induced Ca2+ transients

Human neutrophils express two structurally distinct receptors for the Fc region of IgG, FcgammaRIIa and FcgammaRIIIb. Although earlier studies have suggested that the functional properties of these receptors are similar, mounting evidence suggests that these receptors are capable of inducing distinct functional responses. Accordingly, we have examined the regulation of intracellular Ca2+ transients induced by each of these receptors alone (homotypic receptor cross-linking) and together (heterotypic receptor cross-linking). The glycosylphosphatidylinositol-anchored FcgammaRIIIb induces a rise in [Ca2+] after homotypic cross-linking that is independent of ligand-mediated engagement of the transmembrane FcgammaRIIa. Both receptors were sensitive to the protein-tyrosine kinase inhibitor methyl 2,5-dihydroxycinnamate, but FcgammaRIIa-induced signaling was uniquely sensitive to the protein-tyrosine kinase inhibitor genistein. FcgammaRIIa but not FcgammaRIIIb engages a cAMP-sensitive and inositol 1,4, 5-trisphosphate-dependent pathway(s) that results in the Ca2+-transient. When these receptors are cross-linked into heterotypic clusters, a synergistic rise in [Ca2+] is observed that is accompanied by synergistic increases in the phospholipase Cgamma-breakdown products inositol 1,4,5-trisphosphate and diglyceride. These data provide a mechanism for the functional differences between these two receptors and suggest the possibility that they can be differentially modulated.