Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10934004 | Developmental Biology | 2005 | 12 Pages |
Abstract
Ca2+ is the universal signal for egg activation at fertilization in all sexually reproducing species. The Ca2+ signal at fertilization is necessary for egg activation and exhibits specialized spatial and temporal dynamics. Eggs acquire the ability to produce the fertilization-specific Ca2+ signal during oocyte maturation. However, the mechanisms regulating Ca2+ signaling differentiation during oocyte maturation remain largely unknown. At fertilization, Xenopus eggs produce a cytoplasmic Ca2+ (Ca2+cyt) rise that lasts for several minutes, and is required for egg activation. Here, we show that during oocyte maturation Ca2+ transport effectors are tightly modulated. The plasma membrane Ca2+ ATPase (PMCA) is completely internalized during maturation, and is therefore unable to extrude Ca2+ out of the cell. Furthermore, IP3-dependent Ca2+ release is required for the sustained Ca2+cyt rise in eggs, showing that Ca2+ that is pumped into the ER leaks back out through IP3 receptors. This apparent futile cycle allows eggs to maintain elevated cytoplasmic Ca2+ despite the limited available Ca2+ in intracellular stores. Therefore, Ca2+ signaling differentiates in a highly orchestrated fashion during Xenopus oocyte maturation endowing the egg with the capacity to produce a sustained Ca2+cyt transient at fertilization, which defines the egg's competence to activate and initiate embryonic development.
Keywords
EGTAd-myo-Inositol-1,4,5-trisphosphateCytoplasmic Ca2+Store operated Ca2+ entrySarco-endoplasmic reticulum Ca2+-ATPasePIP2GVBDSOCEMPFIP3IP3RPMCA1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acidEndocytosisoocyte maturationBAPTAgerminal vesicle breakdownCa2+ signalingendoplasmic reticulumPlasma membrane Ca2+-ATPaseplasma membrane Ca2+ ATPaseMaturation Promoting Factorphosphatidylinositol-4,5-bisphosphateSERCAXenopusIP3 receptor
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Authors
Wassim El-Jouni, Byungwoo Jang, Shirley Haun, Khaled Machaca,