Cyclic ADP-ribose-gated Ca2+ release in sea urchin eggs requires an elevated.
Cyclic ADP-ribose (cADPr) has been shown to release intracellular Ca2+ from sea urchin eggs and a variety of vertebrate cell types, although its mechanism of action remains elusive. We employed the caged version of cADPr to study the [Ca2+] transient kinetics in intact sea urchin eggs for insights into how cADPr gates Ca2+ release. Ca2+ release triggered by photolytic production of cADPr was initially slow, with an effective delay of several hundred milliseconds before the onset of a rapid Ca2+ release phase. In contrast, Ca2+ release induced by photolysis of caged inositol 1,4,5-trisphosphate was immediate in onset and roughly an order of magnitude faster. The delay before cADPr-induced Ca2+ release was eliminated when the [Ca2+] was step-elevated coincident with the photoliberation of cADPr and greatly prolonged in the presence of exogenous Ca2+ buffers. Thus, the slow onset of Ca2+ release does not reflect an intrinsically slow rate by which cADPr gates release channels. Rather, a [Ca2+] rise from resting levels is needed to achieve more than minimal cADPr activity. Full release of Ca2+ by cADPr in intact sea urchin eggs requires a positive Ca2+ feedback.
Guo
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Department of Physiology, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
Becker
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PL
D000246:Adenosine Diphosphate Ribose / Q000031:analogs & derivatives* / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002614:Chelating Agents / Q000378:metabolism; D036563:Cyclic ADP-Ribose; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D007700:Kinetics; D010063:Ovum / Q000378:metabolism*; D010782:Photolysis; D012617:Sea Urchins
D002614:Chelating Agents; D036563:Cyclic ADP-Ribose; D000246:Adenosine Diphosphate Ribose; C085112:2-nitrophenyl-EGTA; D004533:Egtazic Acid; D015544:Inositol 1,4,5-Trisphosphate; D002118:Calcium