Starfish oocytes that are extracted from the ovaries are arrested at the prophase of the first meiotic division. At this stage of maturation, they are characterized by a large nucleus called the germinal vesicle. Meiosis resumption (maturation) can be induced in vitro by adding the hormone 1-methyladenine (1-MA) to the seawater in which the oocytes are suspended. Earlier work in our laboratory had detected Ca2+ increases in both the cytoplasm and the nucleus of the oocytes approx. 2 min after the 1-MA challenge. The nuclear Ca2+ increase was found to be essential for the continuation of the meiotic cycle, since the injection of bis-(o-aminophenoxy)ethane-N,N,N´,N´-tetra-acetic acid (BAPTA) into the nuclear compartment completely blocked the re-initiation of the cell cycle. We have recently confirmed, using confocal microscopy, that the cytoplasmic and nuclear Ca2+ pools are regulated independently and that the nuclear envelope in starfish oocytes is not freely permeated by the Ca2+ wave that sweeps across the nuclear region. Studies by others have shown that the sensitivity of the Ins(1,4,5)P3 (IP3) receptors (IP3Rs) to IP3 increases during oocyte maturation, so that they release progressively more calcium in response to the injection of IP3, as maturation proceeds. We have now shown that the increased sensitivity of the IP3Rs may depend on the activation of the cyclin-dependent kinase, MPF (M-phase-promoting factor) that occurs in the nucleus. MPF does not directly phosphorylate IP3Rs but phosphorylates instead the actin-binding protein actin depolymerization factor (ADF)/cofilin.
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February 2003
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Conference Article|
February 01 2003
Activated M-phase-promoting factor (MPF) is exported from the nucleus of starfish oocytes to increase the sensitivity of the Ins(1,4,5)P3 receptors
L. Santella;
L. Santella
1
Laboratory of Cell Biology, Stazione Zoologica ‘Anton Dohrn’ Villa Comunale I-80121, Napoli, Italy
1To whom correspondence should be addressed (e-mail santella@szn.it).
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E. Ercolano;
E. Ercolano
Laboratory of Cell Biology, Stazione Zoologica ‘Anton Dohrn’ Villa Comunale I-80121, Napoli, Italy
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D. Lim;
D. Lim
Laboratory of Cell Biology, Stazione Zoologica ‘Anton Dohrn’ Villa Comunale I-80121, Napoli, Italy
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G.A. Nusco;
G.A. Nusco
Laboratory of Cell Biology, Stazione Zoologica ‘Anton Dohrn’ Villa Comunale I-80121, Napoli, Italy
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F. Moccia
F. Moccia
Laboratory of Cell Biology, Stazione Zoologica ‘Anton Dohrn’ Villa Comunale I-80121, Napoli, Italy
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Publisher: Portland Press Ltd
Online ISSN: 1470-8752
Print ISSN: 0300-5127
Copyright 2003 Biochemical Society
2003
Biochem Soc Trans (2003) 31 (1): 79–82.
Citation
L. Santella, E. Ercolano, D. Lim, G.A. Nusco, F. Moccia; Activated M-phase-promoting factor (MPF) is exported from the nucleus of starfish oocytes to increase the sensitivity of the Ins(1,4,5)P3 receptors. Biochem Soc Trans 1 February 2003; 31 (1): 79–82. doi: https://doi.org/10.1042/bst0310079
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