βγ subunits of heterotrimeric G-proteins contribute to Ca2+ release at fertilization in the sea urchin

Voronina, Ekaterina; Wessel, Gary M.

doi:10.1242/jcs.01518

Cited by 25 publications

(15 citation statements)

References 56 publications

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“…The observed effects were concentration‐dependent and more pronounced in embryos treated with 1.2 µg/mL of toxin than in those treated with 0.2 µg/mL of toxin. Injections of the C‐terminal G αi competitor peptide, also documented to interfere with G i activation (Voronina & Wessel 2004a), replicated the results obtained with pertussis toxin injections (Table 1). For further analysis, we focused on the micromere formation deficiency.…”

Section: Resultssupporting

confidence: 69%

Activator of G‐protein signaling in asymmetric cell divisions of the sea urchin embryo

Voronina

Wessel

2006

Dev Growth Differ

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An asymmetric fourth cell division in the sea urchin embryo results in formation of daughter cells, macromeres and micromeres, with distinct sizes and fates. Several lines of functional evidence presented here, including pharmacological interference and dominant negative protein expression, indicate that heterotrimeric G protein Gi and its interaction partner, activator of G-protein signaling (AGS), are necessary for this asymmetric cell division. Inhibition of Gi signaling by pertussis toxin interferes with micromere formation and leads to defects in embryogenesis. AGS was isolated in a yeast two-hybrid screen with Gαi as bait and was expressed in embryos localized to the cell cortex at the time of asymmetric divisions. Introduction of exogenous dominant-negative AGS protein, containing only G-protein regulatory (GPR) domains, selectively prevented the asymmetric division in normal micromere formation. These results support the growing evidence that AGS is a universal regulator of asymmetric cell divisions in embryos.

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Section: Resultssupporting

confidence: 69%

Activator of G‐protein signaling in asymmetric cell divisions of the sea urchin embryo

Voronina

Wessel

2006

Dev Growth Differ

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“…An alternative possibility is that a heterotrimeric GTPase acts upstream of SFK1 activation. c-Src activity is enhanced in vitro by Gαs and Gαi subunits [55], and the activation of Gαs and Gαq heterotrimeric GTPases is required for Ca 2+ mobilisation through the SFK-PLCγ pathway in sea urchin eggs, but the effect is mediated by the Gβγ components [56].…”

Section: Discussionmentioning

confidence: 99%

Dynamics of PLCγ and Src Family Kinase 1 Interactions during Nuclear Envelope Formation Revealed by FRET-FLIM

et al. 2012

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The nuclear envelope (NE) breaks down and reforms during each mitotic cycle. A similar process happens to the sperm NE following fertilisation. The formation of the NE in both these circumstances involves endoplasmic reticulum membranes enveloping the chromatin, but PLCγ-dependent membrane fusion events are also essential. Here we demonstrate the activation of PLCγ by a Src family kinase (SFK1) during NE assembly. We show by time-resolved FRET for the first time the direct in vivo interaction and temporal regulation of PLCγ and SFK1 in sea urchins. As a prerequisite for protein activation, there is a rapid phosphorylation of PLCγ on its Y783 residue in response to GTP in vitro. This phosphorylation is dependent upon SFK activity; thus Y783 phosphorylation and NE assembly are susceptible to SFK inhibition. Y783 phosphorylation is also observed on the surface of the male pronucleus (MPN) in vivo during NE formation. Together the corroborative in vivo and in vitro data demonstrate the phosphorylation and activation of PLCγ by SFK1 during NE assembly. We discuss the potential generality of such a mechanism.

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“…Although the βγ subunits of G-proteins have been implicated in Ca 2+ signaling at fertilization of sea urchin eggs [24], the exact role of G-proteins in Ca 2+ signaling at fertilization of deuterostomes remains controversial. Initial experiments in sea urchin eggs have shown that GTPγS induced cortical granule exocytosis, while GDPβS blocked sperm-induced cortical reaction [25], [26].…”

Section: Discussionmentioning

confidence: 99%

Guanine Nucleotides in the Meiotic Maturation of Starfish Oocytes: Regulation of the Actin Cytoskeleton and of Ca2+ Signaling

et al. 2009

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BackgroundStarfish oocytes are arrested at the first prophase of meiosis until they are stimulated by 1-methyladenine (1-MA). The two most immediate responses to the maturation-inducing hormone are the quick release of intracellular Ca2+ and the accelerated changes of the actin cytoskeleton in the cortex. Compared with the later events of oocyte maturation such as germinal vesicle breakdown, the molecular mechanisms underlying the early events involving Ca2+ signaling and actin changes are poorly understood. Herein, we have studied the roles of G-proteins in the early stage of meiotic maturation.Methodology/Principal FindingsBy microinjecting starfish oocytes with nonhydrolyzable nucleotides that stabilize either active (GTPγS) or inactive (GDPβS) forms of G-proteins, we have demonstrated that: i) GTPγS induces Ca2+ release that mimics the effect of 1-MA; ii) GDPβS completely blocks 1-MA-induced Ca2+; iii) GDPβS has little effect on the amplitude of the Ca2+ peak, but significantly expedites the initial Ca2+ waves induced by InsP3 photoactivation, iv) GDPβS induces unexpectedly striking modification of the cortical actin networks, suggesting a link between the cytoskeletal change and the modulation of the Ca2+ release kinetics; v) alteration of cortical actin networks with jasplakinolide, GDPβS, or actinase E, all led to significant changes of 1-MA-induced Ca2+ signaling.Conclusions/SignificanceTaken together, these results indicate that G-proteins are implicated in the early events of meiotic maturation and support our previous proposal that the dynamic change of the actin cytoskeleton may play a regulatory role in modulating intracellular Ca2+ release.

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βγ subunits of heterotrimeric G-proteins contribute to Ca2+ release at fertilization in the sea urchin

Cited by 25 publications

References 56 publications

Activator of G‐protein signaling in asymmetric cell divisions of the sea urchin embryo

Activator of G‐protein signaling in asymmetric cell divisions of the sea urchin embryo

Dynamics of PLCγ and Src Family Kinase 1 Interactions during Nuclear Envelope Formation Revealed by FRET-FLIM

Guanine Nucleotides in the Meiotic Maturation of Starfish Oocytes: Regulation of the Actin Cytoskeleton and of Ca2+ Signaling

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