Zinc, iron, and copper contents of Xenopus laevis oocytes and embryos

Nomizu, Tsutomu; Falchuk, Kenneth H.; Vallée, Bert L.

doi:10.1002/mrd.1080360403

Cited by 49 publications

(55 citation statements)

References 22 publications

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“…In addition, an extensive body of information regarding the maeromoleeular events for the induetion and formation of its organs has emerged in the past decade. Finally, large numbers ofXenopus laevis ooeytes at eaeh stage of oogenesis and embryos at different points of development ean be obtained [56]. The first steps are to understand the metabolism of zine in this biologieal system.…”

Section: A Biological System To Study Zinc Transcription Factors In Dmentioning

confidence: 99%

“…Lipovitellin is the ooeyte protein that eontains the zine [58]. Onee the ooeytes are fully mature, they attain a zine eoneentration of about 1 mM [56].…”

Section: A Biological System To Study Zinc Transcription Factors In Dmentioning

confidence: 99%

“…During that period of time it forms proteins, DNA, RNA and aceumulates and stores nutrients and precursors to be used for embryogenesis, a proeess it aehieves within less than 48 h [55]. Zine is one ofthe essential nutrients that is aequired from matemal sources during oogenesis [56]. To insure that zine dependent steps essential for eell division and differentiation are earried out in the short time interval encompassed by embryogenesis, the frog has evolved systems that regulate zine transport, uptake and distribution both within the ooeyte and the embryo.…”

Section: A Biological System To Study Zinc Transcription Factors In Dmentioning

confidence: 99%

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The molecular basis for the role of zinc in developmental biology

Falchuk¹

1998

Molecular and Cellular Effects of Nutrition on Disease Processes

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Zine regulates the gene expression maehinery. It affects the structure of chromatin, the template function of its DNA, the activity of numerous transcription factors and ofRNA polymerases. Hence, it determines both the types of mRNA transcripts synthesized and the rate of transcription itself. Alterations in one or more of these zinc dependent processes have been proposed to account for the proliferative arrest and teratology induced by zinc deficiency. To examine this proposal, studies ofzine duringX laevis development have been initiated. The kinetics of X laevis ooeyte zinc uptake and storage and of zinc utilization during embryogenesis have been examined first. Vitellogenin carries zinc into the ooeyte. Ten % ofthe total zinc (10 ng/egg) remains within the cytosol while 90% (90 ng/egg) is stored in the yolk platelets associated with lipovitellin. The cytosolic pool is the souree of the zinc for all newly formed metalloproteins involved in embryo development. The yolk platelet zinc pool is stored for later use during early metamorphosis. It is now possible to exarnine zinc transfer to moleeules, such as e.g. transcription factors, and the role of the metal in their function in development and organogenesis. (Mol Cell Biochem 188: [41][42][43][44][45][46][47][48]1998)

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Section: A Biological System To Study Zinc Transcription Factors In Dmentioning

confidence: 99%

“…Lipovitellin is the ooeyte protein that eontains the zine [58]. Onee the ooeytes are fully mature, they attain a zine eoneentration of about 1 mM [56].…”

Section: A Biological System To Study Zinc Transcription Factors In Dmentioning

confidence: 99%

Section: A Biological System To Study Zinc Transcription Factors In Dmentioning

confidence: 99%

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The molecular basis for the role of zinc in developmental biology

Falchuk¹

1998

Molecular and Cellular Effects of Nutrition on Disease Processes

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“…sea urchin or frog are fertilized, they are deposited into a sea, river, lake or placed on the undersurface of leaves or other sites to develop into embryos. In those environments, these fertilized eggs must have all of the necessary nutrients or constituents to form a complete embryo without depending on an external and variable supply (Davidson 1990;Nomizu et al 1993). Therefore, during maturation in the maternal ovary, the egg must acquire all essential chemical substances, including metals, for use after fertilization.…”

Section: Egg Metal Contentmentioning

confidence: 99%

Zinc physiology and biochemistry in oocytes and embryos

Falchuk¹,

Montorzi²

2001

Zinc Biochemistry, Physiology, and Homeostasis

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The essential role of zinc in embryogenesis was identified through studies of its presence in eggs and embryos, the effects of its deficiency and its role in metallo proteins required for organ development and formation. The Xenopus laevis oocyte zinc content varies during oogenesis. It increases from 3 to 70 ng zinc/oocyte as it progresses from stage I to VI. The oocyte zinc is derived from the maternal liver as part of a metallo-complex with vitellogenin. The latter transports the metal in plasma and into the oocyte. Once internalized, most of the zinc is stored within yolk platelets bound to lipovitellin, one of the processed products of vitellogenin. About 90% of the total zinc is associated with the yolk platelet lipovitellin while the remaining I 0% is in a compartment associated with hitherto unknown molecule(s) or organelle(s) of the cytoplasm. The bi-compartmental distribution remains constant throughout embryogenesis since the embryo behaves as a closed system for zinc after fertilization. The yolk platelet zinc is used after the tadpole is hatched while we proposed that the I 0% of the zinc in the non-yolk platelet pool is the one used for embryogenesis. It provides zinc to newly synthesized molecules responsible for the development of zinc-dependent organ genesis. Interference with the availability of this zinc by the chelating agent I, I 0-phenanthroline results in the development of embryos that lack dorsal organs, including brain, eyes and spinal cord. The extensive teratology is proposed to be due to altered or absent zinc distribution between the cytosolic pool and zinc-transcription factors. The data identify the components of a zinc transport, storage and distribution system in a vertebrate organism.

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“…In the experiments described above, oocytes that have a total intracellular zinc concentration of ϳ1 mM (35), were bathed in a solution lacking added zinc, resulting in a significant cytosolic-to-extracellular fluid gradient. This gradient may promote ZnT-1-mediated zinc efflux from cells.…”

Section: Fig 2 Cdf Proteins Interact With Rafmentioning

confidence: 99%

Cation Diffusion Facilitator Proteins Modulate Raf-1 Activity

Jirakulaporn

Muslin

2004

Journal of Biological Chemistry

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The Ras-extracellular signal-regulated kinase (ERK) cascade is a critical intracellular signaling pathway that regulates growth, survival, and differentiation. Previous work established that Ras-GTP binds to, and facilitates the activation of, the protein kinase Raf-1. Recently, it was demonstrated that the cation diffusion facilitator (CDF) proteins are involved in Ras-ERK signaling by use of a Caenorhabditis elegans genetic screen that identified suppressors of activated Ras. In the current work, we demonstrate that CDF proteins may function downstream of Ras, but upstream of Raf-1 in Xenopus oocytes. We also show that the C. elegans protein CDF-1 and its mammalian homologue ZnT-1 bind to the amino-terminal regulatory portion of Raf-1 and promote the biological and enzymatic activity of Raf-1. Furthermore, we show that Zn 2؉ inhibits Raf-1 binding to ZnT-1. We propose a model in which CDF protein binding facilitates Raf-1 activation.The Raf-1 protein kinase plays an important role in signal transduction in eukaryotic cells (1-3). Raf-1 is a member of a multigene family that includes A-Raf and B-Raf. Raf family members regulate cell proliferation and differentiation, and are also involved in the pathogenesis of many forms of human cancer. A recent study found that mutations in B-Raf are present in 66% of human melanomas, highlighting the importance of this gene family (4).When active, Raf-1 phosphorylates and activates MEK1, 1 a protein threonine and tyrosine kinase that, in turn, phosphorylates and activates the mitogen-activated protein kinase (MAPK) family members ERK1 and -2 (hereafter called ERK) (5-7). Raf-1 activation is a highly complex and incompletely understood process. Although the three-dimensional x-ray crystallographic structure of Raf-1 has not been solved, a widely accepted model is that that amino-terminal portion of Raf-1 folds over the carboxyl-terminal half to inhibit its kinase activity (8). 14-3-3 dimers may stabilize the inactive conformation of Raf-1 by interacting simultaneously with phosphoserine 259 and phosphoserine 621 of inactive Raf-1 (9 -13). Inactive Raf-1 is also bound to several heat shock proteins that may prevent the proteasome-mediated degradation of Raf-1 and facilitate its cytoplasmic localization (14, 15).The Ras family of small GTPases plays a key role in the activation of . When bound to GTP, Ras binds to two domains on Raf-1, the Ras-binding domain comprising amino acids 51-131, and the cysteine-rich domain (CRD) comprising amino acids 139 -184 (19 -21). Recently, Morrison's group demonstrated that protein phosphatase 2A dephosphorylates phosphoserine 259 of Raf-1 to release 14-3-3 and promote Ras-GTP binding to the CRD in growth factor-stimulated cells (22). By binding to Raf-1, Ras also promotes the plasma membrane localization of Raf-1. Therefore, Ras-GTP facilitates Raf-1 translocation and activation. However, Ras-GTP is not sufficient in most cases to fully activate Raf-1. First, several phosphorylation events occur at the plasma membrane, which facilitate activ...

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Zinc, iron, and copper contents of Xenopus laevis oocytes and embryos

Cited by 49 publications

References 22 publications

The molecular basis for the role of zinc in developmental biology

The molecular basis for the role of zinc in developmental biology

Zinc physiology and biochemistry in oocytes and embryos

Cation Diffusion Facilitator Proteins Modulate Raf-1 Activity

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