Calcium signaling is mediated by a rise in cytoplasmic calcium, either by calcium release from intracellular stores or calcium influx from the extracellular space. In non-excitable cells, the primary calcium entry pathway is Store Operated Calcium Entry. Calcium is a ubiquitous second messenger that is important for many cellular responses, including gene transcription, fertilization, contraction, secretion, cellular proliferation, and apoptosis. How calcium mediates these different cellular responses, often in the same cell, is not clear. Furthermore, the modulation of calcium signaling during the cell cycle is not well defined. This proposal addresses the regulation and specificity of calcium signaling during Xenopus oocyte meiosis. Xenopus oocytes provide a good model for these studies because during oocyte maturation, the two primary calcium signaling pathways, namely IP3 dependent calcium release and SOCE, undergo dramatic changes. IP3-dependent calcium release is enhanced several fold and SOCE is somehow inactivated during meiosis. Determining how these calcium signaling pathways are regulated during meiosis will improve our understanding of calcium signal regulation. An additional advantage of Xenopus oocytes is that they contain calcium-activated chloride currents that can be used as real time indicators of how different calcium signals affect downstream effectors, thus improving our understanding of calcium signal specificity.
The specific aims of the proposal are: 1) characterize the spatial and temporal features of IP3-mediated calcium release and SOCE throughout oogenesis; 2) elucidate the mechanisms regulating SOCE inactivation, and increased IP3-mediated release during meiosis; and 3) record SOCE in mouse oocytes, and test whether it is inactivated during meiosis. In the Xenopus oocyte studies, calcium-activated Cl currents will be measured as downstream effectors of calcium signals. Calcium signaling is important for cellular proliferation and has been implicated in cancer development. Furthermore, SOCE is downregulated in T-cells from patients with primary immunodeficiency, implicating it as an essential signaling pathway in the immune response. Therefore, in addition to contributing to a better basic understanding of calcium signaling, this work will offer insights into the role of calcium signaling in diseases, such as cancer and immunodeficiency.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
3R01GM061829-05S1
Application #
7090561
Study Section
Reproductive Biology Study Section (REB)
Program Officer
Shapiro, Bert I
Project Start
2000-09-30
Project End
2006-03-31
Budget Start
2004-09-01
Budget End
2006-03-31
Support Year
5
Fiscal Year
2005
Total Cost
$1,562
Indirect Cost
Name
University of Arkansas for Medical Sciences
Department
Physiology
Type
Schools of Medicine
DUNS #
122452563
City
Little Rock
State
AR
Country
United States
Zip Code
72205
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Machaca, Khaled (2011) Ca(2+) signaling, genes and the cell cycle. Cell Calcium 49:323-30
Yu, Fang; Sun, Lu; Machaca, Khaled (2010) Constitutive recycling of the store-operated Ca2+ channel Orai1 and its internalization during meiosis. J Cell Biol 191:523-35
Arredouani, Abdelilah; Yu, Fang; Sun, Lu et al. (2010) Regulation of store-operated Ca2+ entry during the cell cycle. J Cell Sci 123:2155-62
Machaca, Khaled (2010) Ca(2+) signaling, genes and the cell cycle. Cell Calcium 48:243-50
Sun, Lu; Haun, Shirley; Jones, Richard C et al. (2009) Kinase-dependent regulation of inositol 1,4,5-trisphosphate-dependent Ca2+ release during oocyte maturation. J Biol Chem 284:20184-96
Yu, Fang; Sun, Lu; Machaca, Khaled (2009) Orai1 internalization and STIM1 clustering inhibition modulate SOCE inactivation during meiosis. Proc Natl Acad Sci U S A 106:17401-6
El-Jouni, Wassim; Haun, Shirley; Machaca, Khaled (2008) Internalization of plasma membrane Ca2+-ATPase during Xenopus oocyte maturation. Dev Biol 324:99-107
Sun, Lu; Hodeify, Rawad; Haun, Shirley et al. (2008) Ca2+ homeostasis regulates Xenopus oocyte maturation. Biol Reprod 78:726-35
Ullah, Ghanim; Jung, Peter; Machaca, Khaled (2007) Modeling Ca2+ signaling differentiation during oocyte maturation. Cell Calcium 42:556-64

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