Microinjection of cyclic ADP-ribose triggers a regenerative wave of Ca²⁺ release and exocytosis of cortical alveoli in medaka eggs

Abstract

Medaka (Oryzias latipes) eggs microinjected with the Ca2+-mobilising messenger cyclic adenosine diphosphate ribose (cADPR) underwent a wave of exocytosis of cortical alveoli and were thus activated. The number of eggs activated was sharply dependent on the concentration of cADPR in the pipette, the threshold concentration was approximately 60 nM. After injection, a pronounced latency preceded the onset of cortical alveoli exocytosis; this latency was independent of the concentration of cADPR but decreased markedly with increasing temperature. Heat-treated cADPR, which yields the inert non-cyclised product ADP-ribose, was ineffective in activating eggs. When cADPR was injected into aequorin-loaded eggs, a wave of luminescence arose at the site of cADPR injection and then swept out across the egg with a mean velocity of approximately 13 μm/s; the velocity was independent of the concentration of injected cADPR. In such a large cell (diameter of around 1 mm), this is considerably faster than that possible by simple diffusion of cADPR, which unambiguously demonstrates that cADPR must activate a regenerative process. cADPR has been demonstrated to modulate Ca2+-induced Ca2+ release (CICR) via ryanodine receptors (RyRs) in many cell types, and consistent with this was the finding that microinjection of the pharmacological RyR modulator, ryanodine, also activated medaka eggs. These results suggest that a cADPR-sensitive Ca2+ release mechanism is present in the medaka egg, that cADPR is the most potent activator of medaka eggs described to date, and that it activates eggs by triggering a wave of CICR from internal stores that in turn stimulates a wave of exocytosis.

Endothelin B receptor Ca2+ signaling in shark vascular smooth muscle: participation of inositol trisphosphate and ryanodine receptors

“…In mammals, cADPR is both synthesized and hydrolyzed by the bifunctional protein CD38 (White et al, 2003). There are only two reports of cADPR activity in fish, both in oocytes (Fluck et al, 1999;Polzonetti et al, 2002). The current study is the first to demonstrate activity of cADPR in VSM of an elasmobranch, S. acanthias.…”

CD38/cyclic ADP-ribose signaling: role in the regulation of calcium homeostasis in airway smooth muscle

“…In the longitudinal smooth muscle of the small intestine, stimulation of the cells with cholecystokinin resulted in an increase in the cADPR levels (94). Pretreatment with GDP-␤S, an inhibitor of G protein, abolished the cholecystokinin-induced cADPR elevation, suggesting the involvement of G proteins in the activation of CD38 (47,94,95). Studies by Higashida et al (67)(68)(69)(70) provided further evidence for the involvement of G proteins.…”

“…Incubation of permeabilized cells, microsomal fractions with cADPR, microinjection of cADPR into intact cells, or flash photolysis of caged cADPR resulted in release of calcium from intracellular stores (27,47,141). In permeabilized airway smooth muscle cells, addition of cADPR elicits intracellular calcium responses (138).…”

CD38 expression and NAD+‐induced intracellular Ca2+ mobilization in isolated retinal Müller cells

“…Subsequent internalization of cADPR appears to occur through a pore formed by dimerization of CD38 (De Flora et al, 1997Munshi et al, 2000;Lee, 2001). Intracellular cADPR then activates RyR1 receptors, releasing Ca 2ϩ from internal stores (Fluck et al, 1999;Zubiar et al, 1999). While we cannot unequivocally exclude other possibilities, our present results are highly consistent with a CD38-cADPR mechanism operating in retinal Mü ller cells.…”