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First published online 9 November 2004
doi: 10.1242/jcs.01518
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Research Article |
subunits of heterotrimeric G-proteins contribute to Ca2+ release at fertilization in the sea urchin
Department of Molecular and Cell Biology and Biochemistry, Brown University, 69 Brown Street, Providence, RI 02912, USA
* Author for correspondence (e-mail: rhet{at}brown.edu)
Accepted 31 August 2004
A cytoplasmic Ca2+ transient is required for egg activation at fertilization in all animals. The pathway leading to release of Ca2+ from the endoplasmic reticulum in echinoderms includes activation of a SRC homolog, followed by phospholipase C
activation, and formation of inositol trisphosphate. However, the upstream activators or modulators of this signaling pathway are not known. We recently identified four G
subunits of heterotrimeric G-proteins present in the sea urchin egg, and here we find that activation of G-proteins of the G
s and G
q type, but not G
i or G
12 type, is required for normal Ca2+ dynamics at fertilization. The effects of these G-proteins are mediated by the Gß
subunits, occur upstream of the cytoplasmic Ca2+ release, and influence both the amplitude of Ca2+ release and the duration of the lag phase. We propose integration of the G-protein input into the framework of signaling at sea urchin fertilization.
Key words: Fertilization, Egg activation, Heterotrimeric G-proteins, Sea urchin, Ca2+
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