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Zhao H, Pan X. Mitochondrial Ca 2+ and cell cycle regulation. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2021; 362:171-207. [PMID: 34253295 DOI: 10.1016/bs.ircmb.2021.02.015] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
It has been demonstrated for more than 40 years that intracellular calcium (Ca2+) controls a variety of cellular functions, including mitochondrial metabolism and cell proliferation. Cytosolic Ca2+ fluctuation during key stages of the cell cycle can lead to mitochondrial Ca2+ uptake and subsequent activation of mitochondrial oxidative phosphorylation and a range of signaling. However, the relationship between mitochondrial Ca2+ and cell cycle progression has long been neglected because the molecule responsible for Ca2+ uptake has been unknown. Recently, the identification of the mitochondrial Ca2+ uniporter (MCU) has led to key advances. With improved Ca2+ imaging and detection, effects of MCU-mediated mitochondrial Ca2+ have been observed at different stages of the cell cycle. Elevated Ca2+ signaling boosts ATP and ROS production, remodels cytosolic Ca2+ pathways and reprograms cell fate-determining networks. These findings suggest that manipulating mitochondrial Ca2+ signaling may serve as a potential strategy in the control of many crucial biological events, such as tumor development and cell division in hematopoietic stem cells (HSCs). In this review, we summarize the current understanding of the role of mitochondrial Ca2+ signaling during different stages of the cell cycle and highlight the potential physiological and pathological significance of mitochondrial Ca2+ signaling.
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Affiliation(s)
- Haixin Zhao
- State Key Laboratory of Experimental Haematology, Institute of Hematology, Fifth Medical Center of Chinese PLA General Hospital, Beijing, China
| | - Xin Pan
- State Key Laboratory of Proteomics, Institute of Basic Medical Sciences, National Center of Biomedical Analysis, Beijing, China.
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Abbineni PS, Hibbert JE, Coorssen JR. Critical role of cortical vesicles in dissecting regulated exocytosis: overview of insights into fundamental molecular mechanisms. THE BIOLOGICAL BULLETIN 2013; 224:200-217. [PMID: 23995744 DOI: 10.1086/bblv224n3p200] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Regulated exocytosis is one of the defining features of eukaryotic cells, underlying many conserved and essential functions. Definitively assigning specific roles to proteins and lipids in this fundamental mechanism is most effectively accomplished using a model system in which distinct stages of exocytosis can be effectively separated. Here we discuss the establishment of sea urchin cortical vesicle fusion as a model to study regulated exocytosis-a system in which the docked, release-ready, and late Ca(2+)-triggered steps of exocytosis are isolated and can be quantitatively assessed using the rigorous coupling of functional and molecular assays. We provide an overview of the insights this has provided into conserved molecular mechanisms and how these have led to and integrate with findings from other regulated exocytotic cells.
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Affiliation(s)
- Prabhodh S Abbineni
- Department of Molecular Physiology, School of Medicine, University of Western Sydney, NSW, Australia
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Machaca K. Ca(2+) signaling, genes and the cell cycle. Cell Calcium 2010; 48:243-50. [PMID: 21084120 DOI: 10.1016/j.ceca.2010.10.003] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2010] [Revised: 10/06/2010] [Accepted: 10/06/2010] [Indexed: 11/30/2022]
Abstract
Changes in the concentration and spatial distribution of Ca(2+) ions in the cytoplasm constitute a ubiquitous intracellular signaling module in cellular physiology. With the advent of Ca(2+) dyes that allow direct visualization of Ca(2+) transients, combined with powerful experimental tools such as electrophysiological recordings, intracellular Ca(2+) transients have been implicated in practically every aspect of cellular physiology, including cellular proliferation. Ca(2+) signals are associated with different phases of the cell cycle and interfering with Ca(2+) signaling or downstream pathways often disrupts progression of the cell cycle. Although there exists a dependence between Ca(2+) signals and the cell cycle the mechanisms involved are not well defined and given the cross-talk between Ca(2+) and other signaling modules, it is difficult to assess the exact role of Ca(2+) signals in cell cycle progression. Two exceptions however, include fertilization and T-cell activation, where well-defined roles for Ca(2+) signals in mediating progression through specific stages of the cell cycle have been clearly established. In the case of T-cell activation Ca(2+) regulates entry into the cell cycle through the induction of gene transcription.
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Affiliation(s)
- Khaled Machaca
- Department of Physiology and Biophysics, Weill Cornell Medical College in Qatar (WCMC-Q), PO Box 24144, Education City - Qatar Foundation, Doha, Qatar.
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5
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Abstract
Over the past few years, we have witnessed a burgeoning series of papers addressing the role of calcium signalling in cell cycle control. In this review I will attempt to bring together all the diverse threads and discuss new concepts that have arisen from the most recent data. Because the major part of the data concerns mitosis/meiosis entry and exit, I have focused on these areas. I will jointly refer to meiotic and mitotic phases of the cell cycle as M-phase because these phases are highly comparable. Studies of the cell cycle involve a huge range of species, from plants to humans. I will, however, restrict this review to the work performed in early embryos. I apologise in advance to contributors to this field whose names I do not mention because they do not work on embryos.
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Carroll J, Swann K, Whittingham D, Whitaker M. Spatiotemporal dynamics of intracellular [Ca2+]i oscillations during the growth and meiotic maturation of mouse oocytes. Development 1994; 120:3507-17. [PMID: 7821218 DOI: 10.1242/dev.120.12.3507] [Citation(s) in RCA: 101] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Calcium oscillations occur during meiotic maturation of mouse oocytes. They also trigger activation at fertilization. We have monitored [Ca2+]i in oocytes at different stages of growth and maturation to examine how the calcium release mechanisms alter during oogenesis. Spontaneous calcium oscillations occur every 2–3 minutes in the majority of fully grown (but immature) mouse oocytes released from antral follicles and resuming meiosis. The oscillations last for 2–4 hours after release from the follicle and take the form of global synchronous [Ca2+]i increases throughout the cell. Rapid image acquisition or cooling the bath temperature from 28 degrees C to 16 degrees C did not reveal any wave-like spatial heterogeneity in the [Ca2+]i signal. Calcium appears to reach highest levels in the germinal vesicle but this apparent difference of [Ca2+] in nucleus and cytoplasm is an artifact of dye loading. Smaller, growing immature oocytes are less competent: about 40% are able to resume meiosis and a similar proportion of these oocytes show spontaneous calcium oscillations. [Ca2+]i transients are not seen in oocytes that do not resume meiosis spontaneously in vitro. Nonetheless, these oocytes are capable of [Ca2+]i oscillations since they show them in response to the addition of carbachol or thimerosal. To examine how the properties of calcium release change during meiotic maturation, a calcium-releasing factor from sperm was microinjected into fully grown immature and mature oocytes. The sperm-factor-induced oscillations were about two-fold larger and longer in mature oocytes compared to immature oocytes. Calcium waves travelling at 40–60 microns/second were generated in mature oocytes, but not in immature oocytes. In some mature oocytes, successive calcium waves had different sites of origin. The modifications in the size and spatial organization of calcium transients during oocyte maturation may be a necessary prerequisite for normal fertilization.
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Affiliation(s)
- J Carroll
- MRC Experimental Embryology and Teratology Unit, St George's Hospital Medical School, London, UK
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Yoshimoto Y, Hiramoto Y. Observation of intracellular Ca2+ with aequorin luminescence. INTERNATIONAL REVIEW OF CYTOLOGY 1991; 129:45-73. [PMID: 1917380 DOI: 10.1016/s0074-7696(08)60508-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Y Yoshimoto
- Biological Laboratory, Kansai Medical University, Osaka, Japan
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MEER JITSEMVANDER. THE ROLE OF METABOLISM AND CALCIUM IN THE CONTROL OF MITOSIS AND OOPLASMIC MOVEMENTS IN INSECT EGGS: A WORKING HYPOTHESIS. Biol Rev Camb Philos Soc 1988. [DOI: 10.1111/j.1469-185x.1988.tb00628.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Fujino Y, Mitsunaga K, Fujiwara A, Yasumasu I. Inhibition of45Ca2+ uptake in the eggs and embryos of the sea urchin,Anthocidaris crassispina, by several calcium antagonists, anion transport inhibitor, and chloride transport inhibitors. ACTA ACUST UNITED AC 1985. [DOI: 10.1002/jez.1402350215] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Duncan CJ. The role of Ca2+ in the regulation of embryogenesis in early amphibian and echinoderm embryos. Life Sci 1984; 35:2481-8. [PMID: 6542618 DOI: 10.1016/0024-3205(84)90433-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
It is difficult to measure intracellular calcium concentrations in dividing embryos and, furthermore, these interact with pHi and with cyclic nucleotides. Nevertheless, the evidence currently suggests that changing [Ca2+]i levels probably do not have a major role in controlling normal cell-to-cell communication and so do not integrate cell division during programmed cleavage in amphibian embryos. However, treatments that are known or expected to raise artificially cytoplasmic calcium to relatively high levels cause abnormal embryogenesis, probably via the uncoupling of intercellular communication of the blastomeres, and also cortical contractions in early echinoderm and amphibian embryos.
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Ichida S, Tokunaga H, Moriyama M, Oda Y, Tanaka S, Kita T. Effects of neurotransmitter candidates on 45Ca uptake by cortical slices of rat brain: stimulatory effect of L-glutamic acid. Brain Res 1982; 248:305-11. [PMID: 6128054 DOI: 10.1016/0006-8993(82)90588-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The effects of neurotransmitter candidates and the characteristics of the stimulatory effect of L-glutamic acid (L-Glu) on 45Ca uptake by rat brain slices were investigated. 45Ca uptake was significantly stimulated by acetylcholine, serotonin and especially L-Glu, but not by other neurotransmitter candidates. L-Glu caused dose-dependent stimulation of 45Ca uptake (L-Glu-stimulated 45Ca uptake), its effect being half-maximal at 1 microM. The related compounds D-glutamic acid, D,L-alpha-aminoadipic acid and N-methyl-D,L-glutamic acid (final conc. of 10 microM) also stimulated 45Ca uptake, but less than 10 microM L-Glu. D,L-alpha-Methylglutamic acid and L-glutamic acid diethylether (final conc. of 10 microM), which are specific inhibitors of L-Glu, inhibited L-Glu-stimulated 45Ca uptake. Mg,Ca-ATPase activity was hardly affected by a concentration of 10 microM L-Glu that caused maximal stimulation of 45Ca uptake. These findings suggest that L-Glu-stimulated 45Ca uptake by brain cortical slices is linked to L-Glu receptor.
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12
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Dubé F, Guerrier P. Activation of Barnea candida (Mollusca, Pelecypoda) oocytes by sperm of KCl, but not by NH4Cl, requires a calcium influx. Dev Biol 1982; 92:408-17. [PMID: 7117692 DOI: 10.1016/0012-1606(82)90186-5] [Citation(s) in RCA: 58] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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13
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Nash WW, Poor BW, Jenkins KD. The uptake and subcellular distribution of lead in developing sea urchin embryos. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. C: COMPARATIVE PHARMACOLOGY 1981; 69:205-11. [PMID: 6116564 DOI: 10.1016/0306-4492(81)90130-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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Nishioka D, McGwin NF. Relationships between the release of acid, the cortical reaction, and the increase of protein synthesis in sea urchin eggs. ACTA ACUST UNITED AC 1980. [DOI: 10.1002/jez.1402120208] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Forer A, Gupta BL, Hall TA. Electron probe x-ray microanalysis of calcium and other elements in meiotic spindles, in frozen sections of spermatocytes from crane fly testes. Exp Cell Res 1980; 126:217-26. [PMID: 7358092 DOI: 10.1016/0014-4827(80)90488-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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Conrad GW, Davis SE. Polar lobe formation and cytokinesis in fertilized eggs of Ilyanassa obsoleta. III. Large bleb formation caused by Sr2+, ionophores X537A and A23187, and compound 48/80. Dev Biol 1980; 74:152-72. [PMID: 6765932 DOI: 10.1016/0012-1606(80)90058-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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Abstract
Mouse oocytes with cumulus cells intact were parthenogenetically activated following release from the oviduct into calcium-free medium. The proportion of activated oocytes increased with post ovulatory age both for oocytes initially exposed to calcium-free and calcium-containing medium (control). Apart from oocytes released shortly after ovulation (approximately 1 h) when less than 1% of the oocytes from treated and control were activated, activation was always higher in oocytes incubated in calcium-free medium (p less than 0.001). The omission of magnesium from the medium had no effect on the activation response of oocytes obtained approximately 3 h after ovulation but its absence did increase the activation rate of oocytes of later post ovulatory age (approximately 9 h after ovulation) although it was still lower than that obtained with media devoid of calcium. When the extracellular calcium was replaced by other divalent cations (strontium, barium and manganese) high rates of activation were obtained even at post ovulatory times which produced relatively low rates of activation in calcium-free medium alone. Similar results were obtained when hamster oocytes were exposed to all the aforementioned treatments. It is concluded that calcium plays an essential role in the activation of the mammalian oocyte but the mechanism of its action remains obscure. Further development of oocytes activated by calcium-free treatment was limited and was similar to that of oocytes activated in other ways.
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Affiliation(s)
- D G Whittingham
- MRC Mammalian Development Unit, University College London, UK
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20
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Meyerhof PG, Masui Y. Ca and Mg control of cytostatic factors from Rana pipiens oocytes which cause metaphase and cleavage arrest. Dev Biol 1977; 61:214-29. [PMID: 412716 DOI: 10.1016/0012-1606(77)90293-7] [Citation(s) in RCA: 89] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Conrad GW, Davis SE. Microiontophoretic injection of calcium ions or of cyclic AMP causes rapid shape changes in fertilized eggs of Ilyanassa obsoleta. Dev Biol 1977; 61:184-201. [PMID: 201519 DOI: 10.1016/0012-1606(77)90291-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Abstract
Fertilization or ionophore activation of Lytechinus pictus eggs can be monitored after injection with the Ca-sensitive photoprotein aequorin to estimate calcium release during activation. We estimate the peak calcium transient to reach concentrations of 2.5–4.5 μM free calcium 45–60 sec after activation and to last 2–3 min, assuming equal Ca2+ release throughout the cytoplasm. Calcium is released from an intracellular store, since similar responses are obtained during fertilization at a wide range of external calcium concentrations or in zero-calcium seawater in ionophore activations. In another effort to estimate free calcium at fertilization, we isolated egg cortices, added back calcium quantitatively, and fixed for observation with a scanning electron microscope. In this way, we determined that the threshold for discharge of the cortical granules is between 9 and 18 μM Ca2+. Therefore, the threshold for the in vitro cortical reaction is about five times the amount of free calcium, assuming equal distribution in the egg. This result suggests that transient calcium release is confined to the inner subsurface of the egg.
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Conrad GW, Kammer AE, Athey GF. Membrane potential of fertilized eggs of Ilyanassa obsoleta during polar lobe formation and cytokinesis. Dev Biol 1977; 57:215-20. [PMID: 558927 DOI: 10.1016/0012-1606(77)90367-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Lauder JM. The effects of early hypo- and hyperthyroidism on the development of rat cerebellar cortex. III. Kinetics of cell proliferation in the external granular layer. Brain Res 1977; 126:31-51. [PMID: 856416 DOI: 10.1016/0006-8993(77)90213-x] [Citation(s) in RCA: 76] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The effects of early hypo- and hyperthyroidism on the rates of cell acquisition and proliferation have been studied in the external granular layer (EGL) of the developing rat cerebellar cortex at 10 days of age using quantitative autoradiographic methods. Both altered thyroid states reduce the rate of cell acquisition in the EGL, but appear to do so for different reasons. Hyperthyroidism shortens the average length of the cell cycle by decreasing the duration of the pre-DNA synthetic phase (G1), indicating that excess thyroxine may exert a direct effect on the EGL. This action involves the early onset of neuronal differentiation (cessation of proliferation)46 which presumably leads to the observed decrease in the rate of cell acquisition (increased doubling time). Such differentiating cells do not, however, leave the proliferative zone or the EGL prematurely, resulting in a reduced labeling index, mitotic index, and growth fraction as non-dividing cells dilute the proliferating cell population. Hypothyroidism, on the other hand, leads to no significant change in the length of the cell cycle or in the mitotic index, but causes a decreased labeling index and growth fraction, as well as a reduced rate of cell acquisition (increased doubling time). No significant change in the amount of cell death in the EGL could be found to explain this apparent discrepancy between the rate of cell proliferation (cell cycle length) and cell acqusiition. The answer to this puzzle appears to lie in the mitotic index, which is not affected to the same extent as the labeling index, although it is also slightly reduced. If cells were to remain longer in mitosis, this could result in a decreased labeling index and growth fraction but nearly normal mitotic index and cell cycle length (as measured using the % labeled mitoses method), since those cells dropping out of the cycling population would be counted as mitoses...
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KUSA MAMORU, SATO HIDEO. ATTEMPTS TO CULTURE ISOLATED URODELAN BLASTOMERES THAT CONTINUE TO DIVIDE WITHOUT AGGREGATING*. Dev Growth Differ 1976. [DOI: 10.1111/j.1440-169x.1976.00227.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Vacquier VD. Isolated cortical granules: a model system for studying membrane fusion and calcium-mediated exocytosis. JOURNAL OF SUPRAMOLECULAR STRUCTURE 1976; 5:27-35. [PMID: 11368 DOI: 10.1002/jss.400050104] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Cortical granules are secretory vesicles bound to the inner surface of the plasma membrane of sea urchin eggs. Intact granules can be isolated by shearing away the cytoplasm of eggs which have been bonded to a protamine-coated surface. When Ca2+ is added to preparations of isolated granules the granules fuse with each other and release their contents. It is believed that isolated cortical granules may be an excellent model system for the biochemical study of exocytosis.
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Garnett HM, Kemp RB. (Ca-2+ + Mg-2+)-Activated ATPase in the plasma membrane mouse liver cells. BIOCHIMICA ET BIOPHYSICA ACTA 1975; 382:526-33. [PMID: 1125244 DOI: 10.1016/0005-2736(75)90219-9] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
1. Purified plasma membranes from dissociated adult mouse liver cells posses a (Ca-2+ + Mg-2+)-stimulated ATPase (EC 3.6.1.3) activity. 2. Enzyme activity is at a maximum with the addition of 0.3 mM Ca-2+ and 3 mM Mg-2+. 3. Using medium devoid of alkali metal ions (Ca-2+ + Mg-2+)-ATPase enzyme activity was observed with Km1 = 0.35 - 10-3 M at a substrate concentration of 1 mM or less and an apparent Km2 = 0.88 - 10-3 M at higher substrate concentrations. 4. In the presence of Na+ and 4 mM ATP, an increase in activity was seen, suggesting the presence of a (Ca-2+ + Mg-2+ + Na+)-activated ATPase. 5. In the presence of both Na+ and K+ the (Ca-2+ + Mg-2+)-dependent enzyme activity was further increased, indicating that a (Ca-2+ +Mg-2+ + K+)-stimulated ATPase may also be present.
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Vacquier VD. The isolation of intact cortical granules from sea urchin eggs: calcium lons trigger granule discharge. Dev Biol 1975; 43:62-74. [PMID: 1171035 DOI: 10.1016/0012-1606(75)90131-1] [Citation(s) in RCA: 300] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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Duffus JH, Patterson LJ. Control of cell division in yeast using the ionophore, A23187 with calcium and magnesium. Nature 1974; 251:626-7. [PMID: 4423924 DOI: 10.1038/251626a0] [Citation(s) in RCA: 36] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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Abstract
Micromolar amounts of the divalent ionophore A23187 can activate echinoderm eggs. The activations by ionophore A23187 were examined in terms of membrane elevation, the program of membrane conductance changes, the respiratory burst, and the increases in protein and DNA synthesis which normally accompany activation by sperm. In all these respects activation by the ionophore was fairly normal although subsequent cleavage and embryonic development was limited. Ionophore A23187 activations of the cortex of Lytechinus pictus and Strongylocentrotus purpuratus eggs were compared in various ionic media and were found to be completely independent of the ionic composition of the external solution. Respiration and protein synthesis of L. pictus eggs in singly substituted ionic media also indicated that these activations were independent of external sodium, calcium, or magnesium. These results suggest that the ionophore acts by releasing intracellular Ca(++). Consistent with this interpretation is the finding that eggs preloaded with (45)Ca show a 20-fold increase in (45)Ca-efflux when activated by ionophore A23187 or fertilization. Measurements of the "free" and "bound" calcium and magnesium in homogenates of the unfertilized eggs show that most of the Mg(++) is already available in the soluble form, whereas Ca(++) is sequestered but available for release. We propose that both normal fertilization and ionophore activation affect the metabolism of the egg by releasing Ca(++) sequestered in intracellular stores.
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Conrad GW, Williams DC. Polar lobe formation and cytokinesis in fertilized eggs of Ilyanassa obsoleta. II. Large bleb formation caused by high concentrations of exogenous calcium ions. Dev Biol 1974; 37:280-94. [PMID: 4856978 DOI: 10.1016/0012-1606(74)90149-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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Petzelt C, von Ledebur-Villiger M. Ca2+-stimulated ATPase during the early development of parthenogenetically activated eggs of the sea urchin Paracentrotus lividus. Exp Cell Res 1973; 81:87-94. [PMID: 4271272 DOI: 10.1016/0014-4827(73)90114-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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