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Echinobase
ECB-ART-31239
Cell Regul 1991 Feb 01;22:121-33. doi: 10.1091/mbc.2.2.121.
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Guanosine 5''-thiotriphosphate may stimulate phosphoinositide messenger production in sea urchin eggs by a different route than the fertilizing sperm.

Crossley I , Whalley T , Whitaker M .


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We show that microinjecting guanosine-5''-thiotriphosphate (GTP gamma S) into unfertilized sea urchin eggs generates an intracellular free calcium concentration [( Ca]i) transient apparently identical in magnitude and duration to the calcium transient that activates the egg at fertilization. The GTP gamma S-induced transient is blocked by prior microinjection of the inositol trisphosphate (InsP3) antagonist heparin. GTP gamma S injection also causes stimulation of the egg''s Na+/H+ antiporter via protein kinase C, even in the absence of a [Ca]i increase. These data suggest that GTP gamma S acts by stimulating the calcium-independent production of the phosphoinositide messengers InsP3 and diacylglycerol (DAG). However, the fertilization [Ca]i transient is not affected by heparin, nor can the sperm cause calcium-independent stimulation of protein kinase C. It seems that the bulk of InsP3 and DAG production at fertilization is triggered by the [Ca]i transient, not by the sperm itself. GDP beta S, a G-protein antagonist, does not affect the fertilization [Ca]i transient. Our findings do not support the idea that signal transduction at fertilization operates via a G-protein linked directly to a plasma membrane sperm receptor.

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Genes referenced: LOC100887844 LOC586799 pkcl2

References [+] :
Berridge, Inositol trisphosphate and diacylglycerol: two interacting second messengers. 1987, Pubmed