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The Ca2+ increase by the sperm factor in physiologically polyspermic newt fertilization: its signaling mechanism in egg cytoplasm and the species-specificity. Dev Biol 2011; 351:266-76. [PMID: 21237143 DOI: 10.1016/j.ydbio.2011.01.003] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2010] [Revised: 12/27/2010] [Accepted: 01/05/2011] [Indexed: 11/22/2022]
Abstract
The newt, Cynops pyrrhogaster, exhibits physiological polyspermic fertilization, in which several sperm enter an egg before egg activation. An intracellular Ca(2+) increase occurs as a Ca(2+) wave at each sperm entry site in the polyspermic egg. Some Ca(2+) waves are preceded by a transient spike-like Ca(2+) increase, probably caused by a tryptic protease in the sperm acrosome at the contact of sperm on the egg surface. The following Ca(2+) wave was induced by a sperm factor derived from sperm cytoplasm after sperm-egg membrane fusion. The Ca(2+) increase in the isolated, cell-free cytoplasm indicates that the endoplasmic reticulum is the major Ca(2+) store for the Ca(2+) wave. We previously demonstrated that citrate synthase in the sperm cytoplasm is a major sperm factor for egg activation in newt fertilization. In the present study, we found that the activation by the sperm factor as well as by fertilizing sperm was prevented by an inhibitor of citrate synthase, palmitoyl CoA, and that an injection of acetyl-CoA or oxaloacetate caused egg activation, indicating that the citrate synthase activity is necessary for egg activation at fertilization. In the frog, Xenopus laevis, which exhibits monospermic fertilization, we were unable to activate the eggs with either the homologous sperm extract or the Cynops sperm extract, indicating that Xenopus sperm lack the sperm factor for egg activation and that their eggs are insensitive to the newt sperm factor. The mechanism of egg activation in the monospermy of frog eggs is quite different from that in the physiological polyspermy of newt eggs.
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2
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Lee B, Vermassen E, Yoon SY, Vanderheyden V, Ito J, Alfandari D, De Smedt H, Parys JB, Fissore RA. Phosphorylation of IP3R1 and the regulation of [Ca2+]i responses at fertilization: a role for the MAP kinase pathway. Development 2007; 133:4355-65. [PMID: 17038520 PMCID: PMC2909192 DOI: 10.1242/dev.02624] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
A sperm-induced intracellular Ca2+ signal ([Ca2+]i) underlies the initiation of embryo development in most species studied to date. The inositol 1,4,5 trisphosphate receptor type 1 (IP3R1) in mammals, or its homologue in other species, is thought to mediate the majority of this Ca2+ release. IP3R1-mediated Ca2+ release is regulated during oocyte maturation such that it reaches maximal effectiveness at the time of fertilization, which, in mammalian eggs, occurs at the metaphase stage of the second meiosis (MII). Consistent with this, the [Ca2+]i oscillations associated with fertilization in these species occur most prominently during the MII stage. In this study, we have examined the molecular underpinnings of IP3R1 function in eggs. Using mouse and Xenopus eggs, we show that IP3R1 is phosphorylated during both maturation and the first cell cycle at a MPM2-detectable epitope(s), which is known to be a target of kinases controlling the cell cycle. In vitro phosphorylation studies reveal that MAPK/ERK2, one of the M-phase kinases, phosphorylates IP3R1 at at least one highly conserved site, and that its mutation abrogates IP3R1 phosphorylation in this domain. Our studies also found that activation of the MAPK/ERK pathway is required for the IP3R1 MPM2 reactivity observed in mouse eggs, and that eggs deprived of the MAPK/ERK pathway during maturation fail to mount normal [Ca2+]i oscillations in response to agonists and show compromised IP3R1 function. These findings identify IP3R1 phosphorylation by M-phase kinases as a regulatory mechanism of IP3R1 function in eggs that serves to optimize [Ca2+]i release at fertilization.
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Affiliation(s)
- Bora Lee
- Molecular and Cellular Biology Program and Department of Veterinary and Animal Sciences, University of Massachusetts, Amherst, MA 01002, USA
| | - Elke Vermassen
- Laboratorium voor Fysiologie, Katholieke Universiteit Leuven, Campus Gasthuisberg O/N1, bus 802, B-3000 Leuven, Belgium
| | - Sook-Young Yoon
- Molecular and Cellular Biology Program and Department of Veterinary and Animal Sciences, University of Massachusetts, Amherst, MA 01002, USA
| | - Veerle Vanderheyden
- Laboratorium voor Fysiologie, Katholieke Universiteit Leuven, Campus Gasthuisberg O/N1, bus 802, B-3000 Leuven, Belgium
| | - Junya Ito
- Molecular and Cellular Biology Program and Department of Veterinary and Animal Sciences, University of Massachusetts, Amherst, MA 01002, USA
| | - Dominique Alfandari
- Molecular and Cellular Biology Program and Department of Veterinary and Animal Sciences, University of Massachusetts, Amherst, MA 01002, USA
| | - Humbert De Smedt
- Laboratorium voor Fysiologie, Katholieke Universiteit Leuven, Campus Gasthuisberg O/N1, bus 802, B-3000 Leuven, Belgium
| | - Jan B. Parys
- Laboratorium voor Fysiologie, Katholieke Universiteit Leuven, Campus Gasthuisberg O/N1, bus 802, B-3000 Leuven, Belgium
| | - Rafael A. Fissore
- Molecular and Cellular Biology Program and Department of Veterinary and Animal Sciences, University of Massachusetts, Amherst, MA 01002, USA
- Author for correspondence ()
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3
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Cao Q, Kim JH, Richter JD. CDK1 and calcineurin regulate Maskin association with eIF4E and translational control of cell cycle progression. Nat Struct Mol Biol 2006; 13:1128-34. [PMID: 17086181 DOI: 10.1038/nsmb1169] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2006] [Accepted: 10/17/2006] [Indexed: 01/02/2023]
Abstract
Maskin regulates assembly of the eIF4F translation initiation complex on messenger RNAs that contain cytoplasmic polyadenylation elements (CPEs) in their 3' untranslated regions. Because Maskin and eIF4G contain similar peptide motifs that bind eIF4E, they compete for occupancy of this factor and consequently control translation. One mRNA that is regulated by Maskin encodes cyclin B1, whose translation oscillates with the early cell cycles of Xenopus laevis embryos. Here we show that Maskin phosphorylation-dephosphorylation also oscillates with the cell cycle and is controlled by the kinase CDK1 and the phosphatase calcineurin. These phosphorylation events control the Maskin-eIF4E interaction and, as a result, translation of cyclin B1 mRNA. Cell cycle progression requires this Maskin-mediated translational regulation.
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Affiliation(s)
- Quiping Cao
- Program in Molecular Medicine, University of Massachusetts Medical School, 373 Plantation St., Worcester, Massachusetts 01605, USA
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4
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Malathi K, Li X, Krizanova O, Ondrias K, Sperber K, Ablamunits V, Jayaraman T. Cdc2/Cyclin B1 Interacts with and Modulates Inositol 1,4,5-Trisphosphate Receptor (Type 1) Functions. THE JOURNAL OF IMMUNOLOGY 2005; 175:6205-10. [PMID: 16237118 DOI: 10.4049/jimmunol.175.9.6205] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The resistance of inositol 1,4,5-trisphosphate receptor (IP3R)-deficient cells to multiple forms of apoptosis demonstrates the importance of IP3-gated calcium (Ca2+) release to cellular apoptosis. However, the specific upstream biochemical events leading to IP3-gated Ca2+ release during apoptosis induction are not known. We have shown previously that the cyclin-dependent kinase 1/cyclin B (cdk1/CyB or cdc2/CyB) complex phosphorylates IP3R1 in vitro and in vivo at Ser421 and Thr799. In this study, we show that: 1) the cdc2/CyB complex directly interacts with IP3R1 through Arg391, Arg441, and Arg871; 2) IP3R1 phosphorylation at Thr799 by the cdc2/CyB complex increases IP3 binding; and 3) cdc2/CyB phosphorylation increases IP3-gated Ca2+ release. Taken together, these results demonstrate that cdc2/CyB phosphorylation positively regulates IP3-gated Ca2+ signaling. In addition, identification of a CyB docking site(s) on IP3R1 demonstrates, for the first time, a direct interaction between a cell cycle component and an intracellular calcium release channel. Blocking this phosphorylation event with a specific peptide inhibitor(s) may constitute a new therapy for the treatment of several human immune disorders.
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Affiliation(s)
- Krishnamurthy Malathi
- Vascular Biology Laboratory, Department of Neurosurgery, St. Luke's Roosevelt Hospital Center, New York, NY 10025, USA
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5
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Jellerette T, Kurokawa M, Lee B, Malcuit C, Yoon SY, Smyth J, Vermassen E, De Smedt H, Parys JB, Fissore RA. Cell cycle-coupled [Ca(2+)](i) oscillations in mouse zygotes and function of the inositol 1,4,5-trisphosphate receptor-1. Dev Biol 2004; 274:94-109. [PMID: 15355791 DOI: 10.1016/j.ydbio.2004.06.020] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2003] [Revised: 06/12/2004] [Accepted: 06/12/2004] [Indexed: 11/20/2022]
Abstract
Sperm entry in mammalian eggs initiates oscillations in the concentration of free calcium ([Ca(2+)](i)). In mouse eggs, oscillations start at metaphase II (MII) and conclude as the zygotes progress into interphase and commence pronuclear (PN) formation. The inositol 1,4,5-trisphosphate receptor (IP(3)R-1), which underlies the oscillations, undergoes degradation during this transition, suggesting that one or more of the eggs' Ca(2+)-releasing machinery components may be regulated in a cell cycle-dependent manner, thereby coordinating [Ca(2+)](i) responses with the cell cycle. To ascertain the site(s) of interaction, we initiated oscillations at different stages of the cell cycle in zygotes with different IP(3)R-1 mass. In addition to sperm, we used two other agonists: porcine sperm factor (pSF), which stimulates production of IP(3), and adenophostin A, a non-hydrolyzable analogue of IP(3). None of the agonists tested induced oscillations at interphase, suggesting that neither decreased IP(3)R-1 mass nor lack of production or excessive IP(3) degradation can account for the insensitivity to IP(3) at this stage. Moreover, the releasable Ca(2+) content of the stores did not change by interphase, but it did decrease by first mitosis. More importantly, experiments revealed that IP(3)R-1 sensitivity and possibly IP(3) binding were altered at interphase, and our data demonstrate stage-specific IP(3)R-1 phosphorylation by M-phase kinases. Accordingly, increasing the activity of M-phase kinases restored the oscillatory-permissive state in zygotes. We therefore propose that the restriction of oscillations in mouse zygotes to the metaphase stage may be coordinated at the level of IP(3)R-1 and that this involves cell cycle stage-specific receptor phosphorylation.
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Affiliation(s)
- Teru Jellerette
- Department of Veterinary and Animal Sciences, University of Massachusetts, Amherst, MA 01003, USA
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6
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Malathi K, Kohyama S, Ho M, Soghoian D, Li X, Silane M, Berenstein A, Jayaraman T. Inositol 1,4,5-trisphosphate receptor (type 1) phosphorylation and modulation by Cdc2. J Cell Biochem 2003; 90:1186-96. [PMID: 14635192 DOI: 10.1002/jcb.10720] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Calcium (Ca2+) release from the endoplasmic reticulum (ER) controls numerous cellular functions including proliferation, and is regulated in part by inositol 1,4,5-trisphosphate receptors (IP3Rs). IP3Rs are ubiquitously expressed intracellular Ca2+-release channels found in many cell types. Although IP3R-mediated Ca2+ release has been implicated in cellular proliferation, the biochemical pathways that modulate intracellular Ca2+ release during cell cycle progression are not known. Sequence analysis of IP3R1 reveals the presence of two putative phosphorylation sites for cyclin-dependent kinases (cdks). In the present study, we show that cdc2/CyB, a critical regulator of eukaryotic cell cycle progression, phosphorylates IP3R1 in vitro and in vivo at both Ser(421) and Thr(799) and that this phosphorylation increases IP3 binding. Taken together, these results indicate that IP3R1 may be a specific target for cdc2/CyB during cell cycle progression.
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Affiliation(s)
- Krishnamurthy Malathi
- Vascular Biology Laboratory, Department of Medicine, St. Luke's Roosevelt Hospital Center, New York, New York, USA
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Sato KI, Tokmakov AA, He CL, Kurokawa M, Iwasaki T, Shirouzu M, Fissore RA, Yokoyama S, Fukami Y. Reconstitution of Src-dependent phospholipase Cgamma phosphorylation and transient calcium release by using membrane rafts and cell-free extracts from Xenopus eggs. J Biol Chem 2003; 278:38413-20. [PMID: 12847104 DOI: 10.1074/jbc.m302617200] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We reported previously that egg membrane rafts serve as a subcellular microdomain for sperm-dependent tyrosine kinase signaling in Xenopus fertilization. Moreover, we demonstrated that raft-associated Src tyrosine kinase was activated by sperm in vitro. Here we show that egg rafts incubated with sperm or hydrogen peroxide (H2O2) can promote Src-dependent phosphorylation of phospholipase Cgamma (PLCgamma) and transient calcium release in the extracts of unfertilized Xenopus eggs. In vivo egg activation by sperm or H2O2 also promotes tyrosine phosphorylation and raft-translocalization of PLCgamma. Immunodepletion of PLCgamma from the egg extracts inhibits the raft-dependent calcium release. Rafts prepared from H2O2-activated eggs also promote Src-dependent dephosphorylation of p42 mitogen-activated protein kinase and cell cycle transition from metaphase II to interphase in egg extracts. PLCgamma phosphorylation and calcium release in egg extracts can be promoted by rafts prepared from COS-7 cells expressing the Xenopus Src gene. These results demonstrate that the signaling events elicited by fertilization in Xenopus eggs can be reconstituted in vitro. The development of such experimental platforms will allow us to dissect the molecular mechanism of sperm-dependent activation of raft-associated Src and subsequent up-regulation of PLCgamma and egg activation machinery in Xenopus eggs.
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Affiliation(s)
- Ken-ichi Sato
- Research Center for Environmental Genomics, Faculty of Science, Kobe University, Nada, Kobe 657-8501, Japan.
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Kawano S, Otsu K, Shoji S, Yamagata K, Hiraoka M. Ca(2+) oscillations regulated by Na(+)-Ca(2+) exchanger and plasma membrane Ca(2+) pump induce fluctuations of membrane currents and potentials in human mesenchymal stem cells. Cell Calcium 2003; 34:145-56. [PMID: 12810056 DOI: 10.1016/s0143-4160(03)00069-1] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Human bone marrow-derived mesenchymal stem cells (hMSCs) have the potential to differentiate into several types of cells. We have demonstrated spontaneous [Ca(2+)](i) oscillations in hMSCs without agonist stimulation, which result primarily from release of Ca(2+) from intracellular stores via InsP(3) receptors. In this study, we further investigated functions and contributions of Ca(2+) transporters on plasma membrane to generate [Ca(2+)](i) oscillations. In confocal Ca(2+) imaging experiments, spontaneous [Ca(2+)](i) oscillations were observed in 193 of 280 hMSCs. The oscillations did not sustain in the Ca(2+) free solution and were completely blocked by the application of 0.1mM La(3+). When plasma membrane Ca(2+) pumps (PMCAs) were blocked with blockers, carboxyeosin or caloxin, [Ca(2+)](i) oscillations were inhibited. Application of Ni(2+) or KBR7943 to block Na(+)-Ca(2+) exchanger (NCX) also inhibited [Ca(2+)](i) oscillations. Using RT-PCR, mRNAs were detected for PMCA type IV and NCX, but not PMCA type II. In the patch clamp experiments, Ca(2+) activated outward K(+) currents (I(KCa)) with a conductance of 170+/-21.6pS could be recorded. The amplitudes of I(KCa) and membrane potential (V(m)) periodically fluctuated liked to [Ca(2+)](i) oscillations. These results suggest that in undifferentiated hMSCs both Ca(2+) entry through plasma membrane and Ca(2+) extrusion via PMCAs and NCXs play important roles for [Ca(2+)](i) oscillations, which modulate the activities of I(KCa) to produce the fluctuation of V(m).
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Affiliation(s)
- Seiko Kawano
- Department of Cardiovascular Diseases, Medical Research Institute, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan.
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9
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Hutchins JRA, Dikovskaya D, Clarke PR. Regulation of Cdc2/cyclin B activation in Xenopus egg extracts via inhibitory phosphorylation of Cdc25C phosphatase by Ca(2+)/calmodulin-dependent protein [corrected] kinase II. Mol Biol Cell 2003; 14:4003-14. [PMID: 14517314 PMCID: PMC206995 DOI: 10.1091/mbc.e03-02-0061] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Activation of Cdc2/cyclin B kinase and entry into mitosis requires dephosphorylation of inhibitory sites on Cdc2 by Cdc25 phosphatase. In vertebrates, Cdc25C is inhibited by phosphorylation at a single site targeted by the checkpoint kinases Chk1 and Cds1/Chk2 in response to DNA damage or replication arrest. In Xenopus early embryos, the inhibitory site on Cdc25C (S287) is also phosphorylated by a distinct protein kinase that may determine the intrinsic timing of the cell cycle. We show that S287-kinase activity is repressed in extracts of unfertilized Xenopus eggs arrested in M phase but is rapidly stimulated upon release into interphase by addition of Ca2+, which mimics fertilization. S287-kinase activity is not dependent on cyclin B degradation or inactivation of Cdc2/cyclin B kinase, indicating a direct mechanism of activation by Ca2+. Indeed, inhibitor studies identify the predominant S287-kinase as Ca2+/calmodulin-dependent protein kinase II (CaMKII). CaMKII phosphorylates Cdc25C efficiently on S287 in vitro and, like Chk1, is inhibited by 7-hydroxystaurosporine (UCN-01) and debromohymenialdisine, compounds that abrogate G2 arrest in somatic cells. CaMKII delays Cdc2/cyclin B activation via phosphorylation of Cdc25C at S287 in egg extracts, indicating that this pathway regulates the timing of mitosis during the early embryonic cell cycle.
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Affiliation(s)
- James R A Hutchins
- Biomedical Research Centre, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, Scotland, United Kingdom
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10
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Tunquist BJ, Maller JL. Under arrest: cytostatic factor (CSF)-mediated metaphase arrest in vertebrate eggs. Genes Dev 2003; 17:683-710. [PMID: 12651887 DOI: 10.1101/gad.1071303] [Citation(s) in RCA: 187] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Affiliation(s)
- Brian J Tunquist
- The Howard Hughes Medical Institute and Department of Pharmacology, University of Colorado School of Medicine, Denver, CO 80262, USA
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11
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Tokmakov AA, Sato KI, Iwasaki T, Fukami Y. Src kinase induces calcium release in Xenopus egg extracts via PLCgamma and IP3-dependent mechanism. Cell Calcium 2002; 32:11-20. [PMID: 12127058 DOI: 10.1016/s0143-4160(02)00078-7] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Mobilization of intracellular calcium is an indispensable step of fertilization-induced egg activation. Recently, this process has been shown to require the sequential activation of Src family tyrosine kinases, phospholipase Cgamma (PLCgamma), and inositol-1,4,5-trisphosphate (IP3)-dependent receptor of endoplasmic reticulum. In the present study, we made an attempt to recapitulate the early events of egg activation by stimulating Src kinase activity in the cell-free extracts of Xenopus eggs. We found that enhanced Src kinase activity can initiate calcium response of low magnitude in cytostatic factor (CSF)-arrested mitotic extracts without releasing them into interphase. The addition of catalytically active recombinant Src kinase, as well as the activation of endogenous Xenopus Src family kinase by hydrogen peroxide (H2O2), increased total tyrosine phosphorylation, tyrosine phosphorylation of PLCgamma, and IP3 production in the extracts. The treatment with the Src family kinase-specific inhibitor, PP1, or PLC inhibitor, U73122, or IP3 receptor antagonist, heparin, prevented calcium release in the extracts. We conclude, therefore, that possible mechanism of Src/H2O2 action in the extracts might involve tyrosine phosphorylation and activation of PLCgamma, accompanied by the increase in IP3 content and subsequent calcium release from IP3-regulated calcium stores. These results also suggest that monitoring calcium signals induced in the Xenopus egg extracts by various components of signaling pathways may provide a particularly useful approach to investigating their role in the signal transduction.
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Affiliation(s)
- A A Tokmakov
- Genomic Sciences Center, RIKEN Yokohama Institute, Yokohama, Japan.
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12
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Sato KI, Iwasaki T, Ogawa K, Konishi M, Tokmakov AA, Fukami Y. Low density detergent-insoluble membrane of Xenopus eggs: subcellular microdomain for tyrosine kinase signaling in fertilization. Development 2002; 129:885-96. [PMID: 11861472 DOI: 10.1242/dev.129.4.885] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Protein-tyrosine phosphorylation plays an important role in egg activation signaling at fertilization. We show that in Xenopus, fertilization stimulates a rapid and transient tyrosine phosphorylation of egg proteins, as revealed by immunoblotting with anti-phosphotyrosine antibody. Immunofluorescent microscopic analysis demonstrated that the phosphorylation occurs in cortical area of the egg animal hemisphere. To further characterize subcellular compartment for fertilization-dependent tyrosine kinase signaling, we isolated low density detergent-insoluble membrane (LD-DIM) fraction from Xenopus eggs. The egg LD-DIM was enriched in cholesterol and GM1 ganglioside. It also contained signaling molecules such as Xyk (Xenopus egg Src), Gqα, Ras, integrin β1 and CD9. Fertilization stimulated tyrosine phosphorylation of Xyk and some other LD-DIM proteins. Remarkably, sperm stimulated tyrosine phosphorylation of the LD-DIM proteins in vitro. The sperm-dependent phosphorylation was sensitive to the tyrosine kinase inhibitors PP2 and genistein. We found that pretreatment of eggs with methyl-β-cyclodextrin, a cholesterol-binding substance, led to a decrease in cholesterol, Xyk and sperm-induced tyrosine phosphorylation in LD-DIM. In methyl-β-cyclodextrin-treated eggs, sperm-induced Ca2+ transient and first cell division were also inhibited. These findings suggest that the egg LD-DIM might serve as subcellular microdomain for tyrosine kinase signaling in Xenopus egg fertilization.
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Affiliation(s)
- Ken-ichi Sato
- Research Center for Environmental Genomics, Kobe University, Nada, Kobe 657-8501 Japan.
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13
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Matsumoto Y, Maller JL. Calcium, calmodulin, and CaMKII requirement for initiation of centrosome duplication in Xenopus egg extracts. Science 2002; 295:499-502. [PMID: 11799245 DOI: 10.1126/science.1065693] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Aberrant centrosome duplication is observed in many tumor cells and may contribute to genomic instability through the formation of multipolar mitotic spindles. Cyclin-dependent kinase 2 (Cdk2) is required for multiple rounds of centrosome duplication in Xenopus egg extracts but not for the initial round of replication. Egg extracts undergo periodic oscillations in the level of free calcium. We show here that chelation of calcium in egg extracts or specific inactivation of calcium/calmodulin-dependent protein kinase II (CaMKII) blocks even initial centrosome duplication, whereas inactivation of Cdk2 does not. Duplication can be restored to inhibited extracts by addition of CaMKII and calmodulin. These results indicate that calcium, calmodulin, and CaMKII are required for an essential step in initiation of centrosome duplication. Our data suggest that calcium oscillations in the cell cycle may be linked to centrosome duplication.
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Affiliation(s)
- Yutaka Matsumoto
- Howard Hughes Medical Institute and Department of Pharmacology, University of Colorado School of Medicine, Denver, CO 80262, USA
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