Probable participation of phospholipase A<sub>2</sub> reaction in the process of fertilization‐induced activation of sea urchin eggs

Kamata, Yoichi; Mita, Masatoshi; Fujiwara, Akiko; Tojo, Tadashi; Takano, Jiro; Ide, Akira; Yasumasu, Ikuo

doi:10.1046/j.1440-169x.1997.t01-3-00002.x

Cited by 3 publications

(4 citation statements)

References 34 publications

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“…As noted earlier, PLA2 inhibition blocks some fertilization events, and there is evidence that LPC, produced through the action of PLA2 on PC, plays a role in membrane fusion (20,21). Although this should be examined directly, the ?50% drop in total amount LPC during fertilization suggests that high levels of LPC do not play a role in sperm-egg fusion or subsequent cortical granule exocytosis.…”

Section: Lpc Changes In Fertilizationmentioning

confidence: 92%

“…LPC can stimulate tyrosine kinases (18), phospholipase C (PLC), and map kinases (19). Phospholipase A2 (PLA2) breaks down phosphatidylcholine (PC) to LPC, and it is interesting to note that a PLA2 inhibitor inhibited fertilization envelope formation during sea urchin fertilization but did not block the increase in [Ca11] in or acid efflux/zygote alkalinization (20). Furthermore, Riffo and Parraga (21) suggest that PLA2 activation is important in sperm-egg fusion, inasmuch as LPC addition induced the interspecies fusion of human sperm and the hamster egg and anti-PLA2 antibodies were inhibitory.…”

Section: Lipid Signaling Related To Fertilizationmentioning

confidence: 99%

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Lipid levels in sperm, eggs, and during fertilization in Xenopus laevis

Petcoff

Holland

Stith

2008

Journal of Lipid Research

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Critical developmental periods, such as fertilization, involve metabolic activation, membrane fusion events such as sperm-egg or plasma membrane-cortical granule merger, and production and hydrolysis of phospholipids. However, there has been no large-scale quantification of phospholipid changes during fertilization. Using an enzymatic assay, traditional FA analysis by TLC and gas chromatography, along with a new method of phospholipid measurement involving HPLC separation and evaporative light-scattering detection, we report lipid levels in eggs, sperm, and during fertilization in Xenopus laevis. Sperm were found to contain different amounts of phospholipids as compared with eggs. During fertilization, total phosphatidylinositol, lysophosphatidylcholine, sphingomyelin, and phosphatidylserine decreased, and ceramide increased, whereas there was no change in phosphatidylcholine, cardiolipin, or phosphatidylethanolamine. FA analysis of phospholipids found numerous changes during fertilization. Because there is an increase in sn-1,2-diacylglycerol at fertilization, the FAs associated with this increase and the source of the increase in this neutral lipid were examined. Finally, activation of phospholipase C, phospholipase D, phospholipase A2, autotoxin, and sphingomyelinase at fertilization is discussed. Major goals of the LIPID Metabolites and Pathways Strategy (LIPID MAPS) are to "separate and detect all of the lipids in a specific cell," "to quantitate each of the lipid metabolites present and determine the changes in their levels," and to study lipid metabolic pathways during biological events (1). Characterizing changes in the lipid composition during defined biological events is part of the concept of "functional lipidomics" (2). These fundamental, descriptive studies will facilitate our understanding of how lipids regulate membrane fluidity and fusion, lipid rafts, the cytoskeleton, kinases, and protein binding to membranes (e.g., 3-5) to induce pleiotropic cellular effects.About 15 years ago, quantification of lipid mass changes during maturation of the oocyte to the fertilizable egg, and during fertilization of the egg by sperm, was begun in Xenopus laevis (6-9). Critical developmental events can be isolated in vitro with this model system, and large numbers of gametes can be obtained to provide sufficient amounts of second messengers and lipids. During fertilization, membrane bending and fusion are associated with the acrosome reaction of sperm (wherein the large sperm acrosome undergoes exocytosis upon interaction with layers that cover the egg), with sperm-egg merger, and with subsequent fertilization events such as cortical granule exocytosis (10, 11). Furthermore, both Xenopus and human eggs are arrested in meiosis II (12).Compared with oocytes, one disadvantage of studying eggs is that they have a short life, much less than the estimated time for lipid precursor incorporation to near equilibrium levels (6, 7). Thus, lipid analysis based on label incorporation or turnover is not reliable, and ...

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Section: Lpc Changes In Fertilizationmentioning

confidence: 92%

Section: Lipid Signaling Related To Fertilizationmentioning

confidence: 99%

Lipid levels in sperm, eggs, and during fertilization in Xenopus laevis

Petcoff

Holland

Stith

2008

Journal of Lipid Research

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“…As mentioned earlier, PLA 2 inhibition was able to block some activation events such as cortical vesicle exocytosis and subsequent fertilization envelope formation probably through calcium-triggered sequential reactions (Kamata et al ., 1997).…”

Section: Discussionmentioning

confidence: 99%

“…In contrast, melittin, known to be an activator of PLA 2 , strongly induced the envelope formation in sea urchin eggs. These observations led to the assumption that the PLA 2 reaction participates in the Ca 2+ -triggered reaction system to cortical vesicles in sea urchin eggs (Ferguson & Shen, 1984; Kamata et al ., 1997).…”

Section: Introductionmentioning

confidence: 99%

Role of phospholipase A₂pathway in regulating activation ofBufo arenarumoocytes

Ajmat

Bonilla

Hermosilla

et al. 2012

Zygote

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Transient increases in the concentration of cytosolic Ca(2+) are essential for triggering egg activation events. Increased Ca(2+) results from its rapid release from intracellular stores, mainly mediated by one or both intracellular calcium channels: the inositol trisphosphate receptor (IP3R) and the ryanodine receptor (RyR). Several regulatory pathways that tailor the response of these channels to the specific cell type have been proposed. Among its many modulatory actions, calcium can serve as an activator of a cytosolic phospholipase A(2) (cPLA2), which releases arachidonic acid from phospholipids of the endoplasmic reticulum as well as from the nuclear envelope. Previous studies have suggested that arachidonic acid and/or its metabolites were able to modulate the activity of several ion channels. Based on these findings, we have studied the participation of the phospholipase A(2) (PLA(2)) pathway in the process of Bufo arenarum oocyte activation and the interrelation between any of its metabolites and the ion channels involved in the calcium release from the intracellular reservoirs at fertilization. We found that addition of both melittin, a potent PLA(2) activator, and arachidonic acid, the main PLA(2) reaction metabolite, was able to induce activation events in a bell-shaped manner. Differential regulation of IP3Rs and RyRs by arachidonic acid and its products could explain melittin and arachidonic acid behaviour in Bufo arenarum egg activation. The concerted action of arachidonic acid and/or its metabolites could provide controlled mobilization of calcium from intracellular reservoirs and useful tools for understanding calcium homeostasis in eggs that express both types of receptors.

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A fluorescence dequenching method for monitoring exocytotic membrane fusion in fertilization of single sea urchin eggs

Takemoto

Hirano

Hayakawa

et al. 1999

Biology of the Cell

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A method for monitoring exocytotic membrane fusion by using a fluorescent membrane probe is presented. The method is based on the relief from concentration‐dependent self‐quenching (dequenching) of fluorescence of 5‐N‐(octadecanoyl)aminofluorescein (AF18), an amphiphilic derivative of fluorescein. The validity and usefulness of this method were shown by the following results: 1) self‐quenching of AF18 fluorescence occurred in the plasma membrane of unfertilized eggs of a sea urchin, Pseudocentrotus depressus, which were heavily stained with the fluorescent dye; 2) dequenching of AF18 fluorescence occurred upon fertilization in normal eggs but not in EGTA‐injected eggs; 3) Ca2+ induced both AF18 fluorescence dequenching and cortical granule disappearance in the isolated sea urchin egg cortex; and 4) simultaneous measurements of the intracellular Ca2+ concentration ([Ca2+]i) and dequenching of AF18 fluorescence by using a simple one‐excitation and two‐emission wavelength system.

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Probable participation of phospholipase A₂ reaction in the process of fertilization‐induced activation of sea urchin eggs

Cited by 3 publications

References 34 publications

Lipid levels in sperm, eggs, and during fertilization in Xenopus laevis

Lipid levels in sperm, eggs, and during fertilization in Xenopus laevis

Role of phospholipase A₂pathway in regulating activation ofBufo arenarumoocytes

A fluorescence dequenching method for monitoring exocytotic membrane fusion in fertilization of single sea urchin eggs

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Probable participation of phospholipase A2 reaction in the process of fertilization‐induced activation of sea urchin eggs

Cited by 3 publications

References 34 publications

Lipid levels in sperm, eggs, and during fertilization in Xenopus laevis

Lipid levels in sperm, eggs, and during fertilization in Xenopus laevis

Role of phospholipase A2pathway in regulating activation ofBufo arenarumoocytes

A fluorescence dequenching method for monitoring exocytotic membrane fusion in fertilization of single sea urchin eggs

Contact Info

Product

Resources

About

Probable participation of phospholipase A₂ reaction in the process of fertilization‐induced activation of sea urchin eggs

Role of phospholipase A₂pathway in regulating activation ofBufo arenarumoocytes