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Dicks LV, Breeze TD, Ngo HT, Senapathi D, An J, Aizen MA, Basu P, Buchori D, Galetto L, Garibaldi LA, Gemmill-Herren B, Howlett BG, Imperatriz-Fonseca VL, Johnson SD, Kovács-Hostyánszki A, Kwon YJ, Lattorff HMG, Lungharwo T, Seymour CL, Vanbergen AJ, Potts SG. A global-scale expert assessment of drivers and risks associated with pollinator decline. Nat Ecol Evol 2021; 5:1453-1461. [PMID: 34400826 DOI: 10.1038/s41559-021-01534-9] [Citation(s) in RCA: 80] [Impact Index Per Article: 26.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Accepted: 07/14/2021] [Indexed: 02/06/2023]
Abstract
Pollinator decline has attracted global attention and substantial efforts are underway to respond through national pollinator strategies and action plans. These policy responses require clarity on what is driving pollinator decline and what risks it generates for society in different parts of the world. Using a formal expert elicitation process, we evaluated the relative regional and global importance of eight drivers of pollinator decline and ten consequent risks to human well-being. Our results indicate that global policy responses should focus on reducing pressure from changes in land cover and configuration, land management and pesticides, as these were considered very important drivers in most regions. We quantify how the importance of drivers and risks from pollinator decline, differ among regions. For example, losing access to managed pollinators was considered a serious risk only for people in North America, whereas yield instability in pollinator-dependent crops was classed as a serious or high risk in four regions but only a moderate risk in Europe and North America. Overall, perceived risks were substantially higher in the Global South. Despite extensive research on pollinator decline, our analysis reveals considerable scientific uncertainty about what this means for human society.
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Affiliation(s)
- Lynn V Dicks
- Department of Zoology, University of Cambridge, Cambridge, UK. .,School of Biological Sciences, University of East Anglia, Norwich, UK.
| | - Tom D Breeze
- Centre for Agri-Environmental Research, School of Agriculture, Policy and Development, Reading University, Reading, UK
| | | | - Deepa Senapathi
- Centre for Agri-Environmental Research, School of Agriculture, Policy and Development, Reading University, Reading, UK
| | - Jiandong An
- Institute of Apicultural Research, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Marcelo A Aizen
- Instituto de Investigaciones en Biodiversidad y Medioambiente (INIBIOMA), Universidad Nacional del Comahue-CONICET, Río Negro, Argentina
| | - Parthiba Basu
- Department of Zoology, University of Calcutta, Kolkata, India
| | - Damayanti Buchori
- Center for Transdisciplinary and Sustainability Sciences, IPB University, Jalan Pajajaran, Indonesia.,Department of Plant Protection, IPB University, Bogor, Indonesia
| | - Leonardo Galetto
- Facultad de Ciencias Exactas, Físicas y Naturales, Universidad de Córdoba, Córdoba, Argentina.,Instituto Multidisciplinario de Biología Vegetal, CONICET-UNC, Córdoba, Argentina
| | - Lucas A Garibaldi
- Instituto de Investigaciones en Recursos Naturales, Agroecología y Desarrollo Rural, Universidad Nacional de Río Negro, Río Negro, Argentina.,Instituto de Investigaciones en Recursos Naturales, Agroecología y Desarrollo Rural, Consejo Nacional de Investigaciones Científicas y Técnicas, Río Negro, Argentina
| | | | - Brad G Howlett
- The New Zealand Institute for Plant & Food Research Limited, Lincoln, New Zealand
| | | | - Steven D Johnson
- Centre for Functional Biodiversity, School of Life Sciences, University of KwaZulu-Natal, Pietermaritzburg, South Africa
| | | | - Yong Jung Kwon
- School of Applied Biosciences, Kyungpook National University, Daegu, Korea
| | | | | | - Colleen L Seymour
- South African National Biodiversity Institute (SANBI), Kirstenbosch Research Centre, Claremont, South Africa.,Department of Biological Sciences, FitzPatrick Institute, University of Cape Town, Rondebosch, South Africa
| | - Adam J Vanbergen
- Agroécologie, AgroSup Dijon, INRAE, University of Bourgogne Franche-Comté, Dijon, France
| | - Simon G Potts
- Centre for Agri-Environmental Research, School of Agriculture, Policy and Development, Reading University, Reading, UK
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Balkrishna S, Bröer A, Kingsland A, Bröer S. Rapid downregulation of the rat glutamine transporter SNAT3 by a caveolin-dependent trafficking mechanism in Xenopus laevis oocytes. Am J Physiol Cell Physiol 2010; 299:C1047-57. [PMID: 20739622 DOI: 10.1152/ajpcell.00209.2010] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The glutamine transporter SNAT3 is involved in the uptake and release of glutamine in the brain, liver, and kidney. Substrate transport is accompanied by Na(+) cotransport and H(+) antiport. In this study, treatment of Xenopus laevis oocytes expressing rat SNAT3 with the phorbol ester PMA resulted in a rapid downregulation of glutamine uptake in less than 20 min. PMA treatment of oocytes coexpressing SNAT3 and the monocarboxylate transporter MCT1 reduced SNAT3 activity only, demonstrating the specificity of the regulatory mechanism. Single or combined mutations of seven putative phosphorylation sites in the SNAT3 sequence did not affect the regulation of SNAT3 by PMA. Expression of an EGFP-SNAT3 fusion protein in oocytes established that the downregulation was caused by the retrieval of the transporter from the plasma membrane. Coexpression of SNAT3 with dominant-negative mutants of dynamin or caveolin revealed that SNAT3 trafficking occurs in a dynamin-independent manner and is influenced by caveolin. Although system N activity was not affected by PMA in cultured astrocytes, a downregulation was observed in HepG2 cells.
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Affiliation(s)
- Sarojini Balkrishna
- Research School of Biology, Australian National Univ., Canberra, ACT 0200, Australia.
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3
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Noh SJ, Han JK. Inhibition of the adenylyl cyclase and activation of the phosphatidylinositol pathway in oocytes through expression of serotonin receptors does not induce oocyte maturation. ACTA ACUST UNITED AC 1998. [DOI: 10.1002/(sici)1097-010x(19980101)280:1<45::aid-jez6>3.0.co;2-h] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Bement WM. Signal transduction by calcium and protein kinase C during egg activation. THE JOURNAL OF EXPERIMENTAL ZOOLOGY 1992; 263:382-97. [PMID: 1402737 DOI: 10.1002/jez.1402630406] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- W M Bement
- Department of Biology, Yale University, New Haven, Connecticut 06511-8112
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Stith BJ, Goalstone ML, Kirkwood AJ. Protein kinase C initially inhibits the induction of meiotic cell division in Xenopus oocytes. Cell Signal 1992; 4:393-403. [PMID: 1419482 DOI: 10.1016/0898-6568(92)90034-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
We have used one activator and two inhibitors of protein kinase C (PKC) to examine the role of this enzyme in the induction of meiotic cell division. At 1 U/ml, phosphatidylcholine-specific phospholipase C increases DAG, alters intracellular pH and inhibits the induction of meiosis by insulin or progesterone. However, when added about 1.6 h after progesterone, the enzyme speeds the induction of cell division. Microinjection of inhibitor peptide (19-36) of PKC has little effect on progesterone action but stimulates the induction of meiosis by insulin. When the inhibitor peptide is injected about 2h after insulin addition, the peptide inhibits. A second PKC inhibitor, staurosporine, decreases PKC-dependent intracellular pH and in vitro oocyte PKC activity. At similar concentrations, staurosporine stimulates insulin or progesterone action, but, when added after about 2 h, the drug inhibits induction by insulin. We conclude that PKC is initially inhibitory to the induction of meiotic cell division but then may become synergistic.
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Affiliation(s)
- B J Stith
- Department of Biology, University of Colorado, Denver 80217-3364
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Bourinet E, Fournier F, Lory P, Charnet P, Nargeot J. Protein kinase C regulation of cardiac calcium channels expressed in Xenopus oocytes. Pflugers Arch 1992; 421:247-55. [PMID: 1326746 DOI: 10.1007/bf00374834] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
L-Type cardiac Ca2+ channels expressed in Xenopus oocyte were studied following rat heart ribonucleic acid, messenger (mRNA) injection. We demonstrate that exogenous Ca2+ channels are sensitive to intracellular regulation by protein kinase C (PKC). This was performed by using two types of PKC activators [phorbol esters and a structural analogue of diacyl-glycerol (DAG)] and a specific peptidic inhibitor. Ca2+ channel modulation resulted in an initial increase of the inward current, without any modification of the voltage-dependent properties, and a second delayed phase, specifically observed with phorbol esters, characterized by a progressive decrease in current amplitude. Concomitantly, a reduction of membrane capacitance, reflecting a reduction of the total membrane surface area, was observed. We suggest that this phenomenon underlies the irreversible decrease of the expressed Ba2+ current via sequestration of Ca2+ channels and/or PKC. We also demonstrate that regulation of cardiac mRNA-directed Ca2+ channels by PKC activators was strictly dependent on intracellular Ca2+ concentration, and was partially additive with cyclic-adenosine-monophosphate-(cAMP) dependent regulation.
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Affiliation(s)
- E Bourinet
- Centre de Recherches de Biochimie Macromoleculaire, CNRS UPR 9008, INSERM U 249, Montpellier, France
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Stith BJ, Kirkwood AJ, Wohnlich E. Insulin-like growth factor 1, insulin, and progesterone induce early and late increases in Xenopus oocyte sn-1,2-diacylglycerol levels before meiotic cell division. J Cell Physiol 1991; 149:252-9. [PMID: 1748718 DOI: 10.1002/jcp.1041490211] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
After a 3 to 6 hour incubation, addition of progesterone (the most effective), insulin-like growth factor 1 (IGF-1; the second most effective), or insulin induces meiotic cell division in Xenopus oocytes. Measurement of an endogenous activator of protein kinase C, sn-1,2-diacylglycerol (DAG), by an enzymatic method recording mass demonstrates that all three hormones alter DAG levels. Five seconds after addition, only progesterone transiently reduces DAG levels by about 25%. At 15 minutes after addition, all three hormones produce a peak of DAG (115% to 160% of control values), with the more effective hormones producing a larger increase in DAG. Insulin produces the smallest DAG increase, but the DAG release is longer lasting. Finally, all three hormones induce a second peak in DAG levels just before white spot appearance (at 0.85 GVBD50, where 1.0 GVBD50 is when 50% of the cells have divided). With these data and since an activator of protein kinase C, a phorbol ester, has been found to induce meiosis, the kinase may play a role in early proliferative events at the plasma membrane and in late events at the nucleus.
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Affiliation(s)
- B J Stith
- Department of Biology, University of Colorado, Denver 80217-3364
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Bement WM, Capco DG. Parallel pathways of cell cycle control during Xenopus egg activation. Proc Natl Acad Sci U S A 1991; 88:5172-6. [PMID: 2052598 PMCID: PMC51834 DOI: 10.1073/pnas.88.12.5172] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Transit from M phase into interphase in many eukaryotic cells is preceded by an increase in intracellular free calcium ([Ca2+]i), which may act via calcium-dependent enzymes to trigger the M-phase/interphase transition. To test the role of the calcium- and phospholipid-dependent enzyme protein kinase C (PKC) in the M-phase/interphase transition, PKC was activated in M-phase-arrested Xenopus eggs by treatment with the phorbol ester phorbol 12-myristate 13-acetate under conditions that prevent a rise in [Ca2+]i and activation of other calcium-dependent enzymes. Under these conditions, several cellular events characteristic of transit into interphase occur: sperm chromatin decondenses, the Golgi and the nuclear envelope reassemble, and endocytosis resumes. These events are also triggered by treatment of eggs with the diacylglycerol 1,2-dioctanoyl-sn-glycerol. Surprisingly, the activity of M-phase-promoting factor (MPF), a universal regulator of M phase, remains high under these conditions. If [Ca2+]i is subsequently raised, MPF activity is rapidly destroyed. Similarly, lysates made from eggs treated with phorbol 12-myristate 13-acetate support sperm chromatin decondensation in vitro and yet retain high MPF activity, measured either as the ability to induce meiotic resumption in oocytes or as histone H1 kinase activity. These effects are not triggered by the 4 alpha-phorbol ester isomer, which does not activate PKC, and are sensitive to the PKC "pseudosubstrate" peptide. The results suggest that two, parallel signals are generated by the rise in [Ca2+]i both of which contribute to cell cycle regulation. One pathway inactivates MPF; the other pathway activates PKC.
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Affiliation(s)
- W M Bement
- Department of Zoology, Arizona State University, Tempe 85287-1501
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Khan NA, Quemener V, Moulinoux JP. Exogeneous diacylglycerols downregulate the activity of Na(+)-K+ pump in Xenopus laevis oocytes. Exp Cell Res 1991; 194:248-51. [PMID: 1851097 DOI: 10.1016/0014-4827(91)90361-w] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
In this study, cell permeable diacylglycerols, sn-1,2-dioctanoglycerol (DiC8), and sn-1-oleoyl-2-acetylglycerol (OAG) were found to downregulate the activity of Na(+)-K+ pump in Xenopus laevis oocytes. Both DiC8 and OAG decreased the binding of [3H]ouabain to intact oocytes while phorbol esters did not appreciably influence the same. These diacylglycerols inhibited the amiloride-sensitive 22Na+ influx and ouabain-sensitive 86Rb+ uptake in the oocytes. Furthermore, DiC8 prevented the 22Na+ efflux from the oocytes preloaded with 22Na+. Addition of H-7 to DiC8- and OAG-treated oocytes stimulated the pump activity curtailed by the two latters. The impairment of Na(+)-K+ pump activity by diacylglycerols suggests that protein kinase C activators may stimulate endocytosis of membrane-coupled Na(+)-K+ ATPase.
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Affiliation(s)
- N A Khan
- Unité Fonctionnelle de Biologie Cellulaire, Faculté de Médecine, Université de Rennes, France
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Kwon HB, Lee WK. Involvement of protein kinase C in the regulation of oocyte maturation in amphibians (Rana dybowskii). THE JOURNAL OF EXPERIMENTAL ZOOLOGY 1991; 257:115-23. [PMID: 1986050 DOI: 10.1002/jez.1402570115] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Ovarian oocytes of Rana dybowskii, isolated early in the hibernation period (late autumn), failed to mature, i.e., germinal vesicle breakdown (GVBD), in response to progesterone during in vitro follicle culture. Oocytes collected during the middle hibernation period matured in response to progesterone, whereas those collected late during the hibernation period (close to the breeding season) underwent spontaneous maturation without added hormone (Kwon et al., '89). The maturational response (GVBD) of oocytes, collected at the three stages of hibernation, to protein kinase C (PKC) activation was investigated and compared to that of progesterone stimulation. A phorbol ester, phorbol 12-myristate 13-acetate (TPA) was used for PKC activation. TPA addition to cultured follicles collected during the early or middle period of hibernation induced oocyte GVBD. The incidence of maturation (% GVBD) induced by TPA varied markedly between animals. TPA (10 microM) induced oocyte maturation in the presence or absence of follicle cells. The time course of the TPA-induced maturation was similar to that of progesterone-stimulated maturation (ED50, 7-9 h). TPA also accelerated the onset of maturation of the follicular oocytes exhibiting spontaneous in vitro maturation. Both TPA- and progesterone-stimulated maturation was blocked by treatment with cycloheximide (1 microgram/2 ml), forskolin (9 microM) (an adenylate cyclase stimulator), and verapamil (0.27 mM) (a calcium transport blocker). Treatment of oocytes with a calmodulin antagonist N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7) (100 microM) or a PKC inactivator 1-(5-isoquinolinylsulfonyl)-2-methyl-piperazine (H-7) (50 microM) likewise suppressed TPA- or progesterone-induced maturation.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- H B Kwon
- Chonnam National University, College of Natural Sciences, Department of Biology, Kwangju, Republic of Korea
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Bement WM, Capco DG. Analysis of inducible contractile rings suggests a role for protein kinase C in embryonic cytokinesis and wound healing. CELL MOTILITY AND THE CYTOSKELETON 1991; 20:145-57. [PMID: 1751967 DOI: 10.1002/cm.970200207] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
A semi-in vitro system derived from Xenopus oocytes which allows induction of contractile ring (CR) formation and closure is described and exploited to elucidate regulatory and structural features of cytokinesis. The inducible CRs (ICRs) are composed of actin filaments and closure is actin filament-dependent as is cytokinesis in vivo. ICR closure in this system is calcium-dependent and pH-sensitive, as is cytokinesis in permeabilized cells (Cande: Journal of Cell Biology 87:326, 1980). Closure of ICRs proceeds at a rate and with a kinetic pattern similar to embryonic cytokinesis. Collectively, these data demonstrate that this system is a faithful mimic of cytokinesis in vivo. ICR formation and closure is protein kinase C (PKC)-dependent and neomycin-sensitive, indicating that the PKC branch of the polyphosphoinositide pathway regulates formation of the actomyosin ring which is the effector of cytokinesis. Kinetic measurements show that the rate of ICR closure reaches a peak of 4-8 microns/sec. Since the maximum measured velocity of actin filament translocation by vertebrate, non-muscle myosins is 0.04 micron/sec, the later observations support a model in which the CR is segmented, containing multiple sites where filaments overlap in a "sliding filament" fashion. Because the rate decreases after reaching a peak, the results also suggest that the number of overlap sites decrease with time.
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Affiliation(s)
- W M Bement
- Department of Zoology, Arizona State University, Tempe 85287-1501
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Bement WM, Capco DG. Transformation of the amphibian oocyte into the egg: structural and biochemical events. JOURNAL OF ELECTRON MICROSCOPY TECHNIQUE 1990; 16:202-34. [PMID: 2243278 DOI: 10.1002/jemt.1060160303] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Amphibian oocytes, arrested in prophase I, are stimulated to progress to metaphase II by progesterone. This process is referred to as meiotic maturation and transforms the oocyte, which cannot support the early events of embryogenesis, into the egg, which can. Meiotic maturation entails global reorganization of cell ultrastructure: In the cell cortex, the plasma membrane flattens and the cortical granules undergo redistribution. In the cell periphery, the annulate lamellae disassemble and the mitochondria become dispersed. In the cell interior, the germinal vesicle becomes disassembled and the meiotic spindles form. Marked changes in the cytoskeleton and mRNA distribution also occur throughout the cell. All of these events are temporally correlated with intracellular signalling events: Fluctuations in cAMP levels, changes in pH, phosphorylation and dephosphorylation, and ion flux changes. Evidence suggests that specific intracellular signals are responsible for specific reorganizations of ultrastructure and mRNA distribution.
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Affiliation(s)
- W M Bement
- Department of Zoology, Arizona State University, Tempe 85287-1501
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Vasilets LA, Schmalzing G, Mädefessel K, Haase W, Schwarz W. Activation of protein kinase C by phorbol ester induces downregulation of the Na+/K(+)-ATPase in oocytes of Xenopus laevis. J Membr Biol 1990; 118:131-42. [PMID: 2176238 DOI: 10.1007/bf01868470] [Citation(s) in RCA: 103] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Full-grown prophase-arrested oocytes of Xenopus laevis were treated with 50 nM phorbol 12-myristate 13-acetate (PMA), an activator of protein kinase C, or with 50 nM 4 alpha-phorbol 12,13-didecanoate (4 alpha PDD) that does not activate protein kinase C. The effect on membrane currents and capacitance, inulin uptake and ouabain binding, and on membrane morphology were analyzed. (i) During application of PMA, current generated by the Na+/K+ pump decreases; in addition, Cl- and K+ channels become inhibited. This general decrease in membrane conductance reaches steady state after about 60 min. 4 alpha PDD was ineffective. (ii) Ouabain binding experiments demonstrate that PMA (K1/2 = 7 nM), but not 4 alpha PPD, induces a reduction of the number of pump molecules in the surface membrane. Permeabilization of oocytes by digitonin plus 0.02% SDS renders all binding sites present prior to PMA treatment again accessible for ouabain. The KD value for ouabain binding is not influenced. 4 alpha PDD was ineffective. (iii) Exposure of oocytes to PMA reduces membrane capacitance and stimulates uptake of inulin suggesting an increase in endocytosis. Electron micrographs show that PMA reduces the number and length of microvilli, leading finally to a smooth membrane surface with a reduced surface area. From these results we conclude that stimulation of protein kinase C leads to downregulation of the sodium pump. A major portion of this inhibition is brought about by reduction in area of surface membrane with a concomitant internalization of pump molecules. In addition to this mode of downregulation, a direct effect of stimulation of protein kinase C on the pump molecule cannot be excluded.
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Affiliation(s)
- L A Vasilets
- Max-Planck-Institut für Biophysik, Frankfurt/M., Federal Republic of Germany
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Cormier P, Mulner-Lorillon O, Ozon R, Bellé R. Involvement of protein kinase A and casein kinase II in the in vivo protein kinase activities in prophase arrested Xenopus oocytes. Biosci Rep 1989; 9:351-8. [PMID: 2775862 DOI: 10.1007/bf01114688] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
In vivo beta casein phosphorylation was analysed in Xenopus full-grown oocytes arrested in the prophase of the meiotic cell division. The phosphorylation was inhibited by the protein kinase inhibitor (PKI) and also by heparin (3 micrograms/ml; final concentration). beta casein phosphorylation was increased by spermine (2 mM). Therefore, protein kinase A and casein kinase II are both active in vivo in full-grown oocytes and may be involved in the prophase arrest of meiotic cell division.
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Affiliation(s)
- P Cormier
- Physiologie de la Reproduction, CNRS URA 004, Paris
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Bement WM, Capco DG. Activators of protein kinase C trigger cortical granule exocytosis, cortical contraction, and cleavage furrow formation in Xenopus laevis oocytes and eggs. J Biophys Biochem Cytol 1989; 108:885-92. [PMID: 2493460 PMCID: PMC2115396 DOI: 10.1083/jcb.108.3.885] [Citation(s) in RCA: 91] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Prophase I oocytes, free of follicle cells, and metaphase II eggs of the amphibian Xenopus laevis were subjected to transient treatments with the protein kinase C activators, phorbol 12-myristate 13-acetate (PMA), phorbol 12,13-didecanoate, and 1-olyeoyl-2-acetyl-sn-glycerol. In both oocytes and eggs, these treatments triggered early events of amphibian development: cortical granule exocytosis, cortical contraction, and cleavage furrow formation. Surprisingly, activation of oocytes occurred in the absence of meiotic resumption, resulting in cells with an oocytelike nucleus and interior cytoplasm, but with a zygotelike cortex. PMA-induced activation of oocytes and eggs did not require external calcium, a prerequisite for normal activation of eggs. PMA-induced activation of eggs was inhibited by retinoic acid, a known inhibitor of protein kinase C. In addition, pretreatment of eggs with retinoic acid prevented activation by mechanical stimulation and inhibited activation by calcium ionophore A23187. The results suggest that protein kinase C activation is an integral component of the Xenopus fertilization pathway.
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Affiliation(s)
- W M Bement
- Department of Zoology, Arizona State University, Tempe 85287-1501
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