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  • EAAT2 density at the astrocyte plasma membrane and Ca(2 + )-regulated exocytosis
    Stenovec, Matjaž ...
    We studied whether regulated exocytosis affects the glutamate transporter density in cultured astrocytes, in which the expression of a fluorescently labeled excitatory amino acid transporter 2 ... (EAAT2-EGFP) predominantly labeledthe plasma membrane. The addition of ionomycin that elevates cytosolic Ca(2+) strongly increased the fluorescence of FM 4-64 membrane area dye, confirming the presence of regulated exocytosis in transfected astrocytes. However, concomitant with Ca(2+)-dependent FM 4-64 fluorescence increase, ionomycin induced a significant steady-state decrease in EAAT2-EGFP fluorescence. This is likely due to a secondary inner filter effect since,(i) in the absence of FM 4-64, ionomycin stimulation was ineffective in changing the EAAT2-EGFP fluorescence, and (ii) fluorescence changes in FM 4-64 and EAAT2-EGFP were inversely correlated. To test whether subcellular EAAT2-EGFP structures are translocated from the cytoplasm to the plasma membrane during ionomycin stimulation, EAAT2-EGFP fluorescence was monitored locally at the plasma membrane and a few microns away in the adjacent cytoplasm. Measurementsrevealed sites with an increase in EAAT2-EGFP plasma membrane fluorescence correlated with a fluorescence decrease beneath the plasma membrane, and sites with plasma membrane fluorescence decrease correlated withfluorescence increase within the adjacent cytoplasm. The sites of rapid translocation/retrieval of EAAT2-EGFP structures to/from the plasma membrane appeared to be distributed in a punctuate pattern around the cell perimeter. The density of EAAT2-EGFP was regulated in a Ca(2+)-dependent manner, since in the absence of extracellular Ca(2+) local translocation/retrieval events were absent, revealing rapid surface density regulation of EAAT2 in astrocytesby regulated exo/endocytosis.
    Source: Molecular membrane biology. - ISSN 0968-7688 (Letn. 25, št. 3, 2008, str. 203-215)
    Type of material - article, component part
    Publish date - 2008
    Language - english
    COBISS.SI-ID - 24138713
    DOI

source: Molecular membrane biology. - ISSN 0968-7688 (Letn. 25, št. 3, 2008, str. 203-215)
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