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@ARTICLE{Meyer:866279,
      author       = {Meyer, Jan and Untiet, Verena and Fahlke, Christoph and
                      Gensch, Thomas and Rose, Christine R.},
      title        = {{Q}uantitative determination of cellular [{N}a + ] by
                      fluorescence lifetime imaging with {C}oro{N}a{G}reen},
      journal      = {The journal of general physiology},
      volume       = {151},
      number       = {11},
      issn         = {1540-7748},
      address      = {New York, NY},
      publisher    = {Rockefeller Univ. Press},
      reportid     = {FZJ-2019-05438},
      pages        = {1319 - 1331},
      year         = {2019},
      abstract     = {Fluorescence lifetime imaging microscopy (FLIM) with
                      fluorescent ion sensors enables the measurement of ion
                      concentrations based on the detection of photon emission
                      events after brief excitation with a pulsed laser source. In
                      contrast to intensity-based imaging, it is independent of
                      dye concentration, photobleaching, or focus drift and has
                      thus been successfully employed for quantitative analysis
                      of, e.g., calcium levels in different cell types and
                      cellular microdomains. Here, we tested the suitability of
                      CoroNaGreen for FLIM-based determination of sodium
                      concentration ([Na+]) inside cells. In vitro measurements
                      confirmed that fluorescence lifetimes of CoroNaGreen
                      (CoroNaFL) increased with increasing [Na+]. Moreover,
                      CoroNaFL was largely independent of changes in potassium
                      concentration or viscosity. Changes in pH slightly affected
                      FL in the acidic range (pH ≤ 5.5). For intracellular
                      determination of [Na+], HEK293T cells were loaded with the
                      membrane-permeable form of CoroNaGreen. Fluorescence decay
                      curves of CoroNaGreen, derived from time-correlated
                      single-photon counting, were approximated by a
                      bi-exponential decay. In situ calibrations revealed a
                      sigmoidal dependence of CoroNaFL on [Na+] between 0 and 150
                      mM, exhibiting an apparent Kd of ∼80 mM. Based on these
                      calibrations, a [Na+] of 17.6 mM was determined in the
                      cytosol. Cellular nuclei showed a significantly lower [Na+]
                      of 13.0 mM, whereas [Na+] in perinuclear regions was
                      significantly higher (26.5 mM). Metabolic inhibition or
                      blocking the Na+/K+-ATPase by removal of extracellular K+
                      caused significant [Na+] increases in all cellular
                      subcompartments. Using an alternative approach for data
                      analysis (“Ratio FLIM”) increased the temporal
                      resolution and revealed a sequential response to K+ removal,
                      with cytosolic [Na+] increasing first, followed by the
                      nucleus and finally the perinuclear regions. Taken together,
                      our results show that CoroNaGreen is suitable for dynamic,
                      FLIM-based determination of intracellular [Na+]. This
                      approach thus represents a valuable tool for quantitative
                      determination of [Na+] and changes thereof in different
                      subcellular compartments.},
      cin          = {ICS-4},
      ddc          = {610},
      cid          = {I:(DE-Juel1)ICS-4-20110106},
      pnm          = {552 - Engineering Cell Function (POF3-552)},
      pid          = {G:(DE-HGF)POF3-552},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {pmid:31597684},
      UT           = {WOS:000494850300007},
      doi          = {10.1085/jgp.201912404},
      url          = {https://juser.fz-juelich.de/record/866279},
}