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Implication of the small GTPase Rac1 in the generation of reactive oxygen species in response to beta-amyloid in C6 astroglioma cells.

Authors
Lee, M; You, HJ; Cho, SH; Woo, CH; Yoo, MH; Joe, EH; Kim, JH
Citation
The Biochemical journal, 366(Pt3):937-943, 2002
Journal Title
The Biochemical journal
ISSN
0264-60211470-8728
Abstract
Exogenous application of beta-amyloid (Abeta(25-35), a fragment of Abeta(1-42)) significantly elevated levels of reactive oxygen species (ROS) in C6 astroglioma cells, as measured by confocal microscopic analysis of H(2)O(2)-sensitive 2',7'-dichlorofluorescin fluorescence. Subsequent characterization of the signalling pathway revealed that expression of RacN17, a dominant-negative Rac1 mutant, completely blocked Abeta(25-35)-induced generation of ROS, which is indicative of the crucial role played by Rac GTPase in this process. To better understand the downstream mediators affected by Rac, we assessed the degree to which inhibition of cytosolic phospholipase A(2) (cPLA(2)) and 5-lipoxygenase (5-LO) contributed to the response and found that inhibition of either enzyme completely blocked Abeta(25-35)-induced ROS generation, indicating its dependence on arachidonic acid synthesis and metabolism to leukotrienes (e.g. leukotriene B(4)). Consistent with those findings, Abeta(25-35) Rac-dependently stimulated translocation of 5-LO to the nuclear envelope and increased intracellular levels of leukotriene B(4), while exogenous application of leukotriene B(4) increased intracellular H(2)O(2) via BLT, its cell-surface receptor. In addition to the aforementioned downstream mediators, inhibition of phosphoinositide 3-kinase (PI 3-kinase), an enzyme situated upstream of Rac, also completely blocked Abeta(25-35)-induced H(2)O(2) generation. Our findings thus demonstrate that PI 3-kinase, Rac, cPLA(2) and 5-LO are all essential components of the beta-amyloid signaling cascade leading to generation of ROS.
MeSH terms
Amyloid beta-Peptides/*metabolismArachidonate 5-Lipoxygenase/metabolismAstrocytoma/metabolismBlotting, WesternBrain Neoplasms/metabolismCytosol/enzymologyHumansHydrogen Peroxide/pharmacologyLeukotriene B4/pharmacologyNADPH Oxidase/metabolismPhosphatidylinositol 3-Kinases/metabolismPhospholipases A/metabolismPlasmids/metabolismReactive Oxygen SpeciesReverse Transcriptase Polymerase Chain ReactionSignal TransductionSubcellular Fractions/metabolismTime FactorsTransfectionTumor Cells, Culturedrac1 GTP-Binding Protein/*chemistry/*metabolism
DOI
10.1042/BJ20020453
PMID
12038964
Appears in Collections:
Journal Papers > School of Medicine / Graduate School of Medicine > Pharmacology
AJOU Authors
조, 은혜
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