title: Live imaging of glucose homeostasis in nuclei of COS-7 cells.
abstract: Measuring subcellular glucose levels deep in tissues can provide new insights into compartmentalization and specialization of glucose metabolism among different cells. As shown previously, a FRET-based glucose-sensor consisting of two GFP-variants and the Escherichia coli periplasmic glucose/galactose binding protein was successfully expressed in the cytosol of COS7-cells and used to determine cytosolic glucose levels. Recording cytosolic fluorescence intensities in cells located in deeper layers of tissues is often difficult due to loss of signal intensity caused by effects of other cell layers on excitation and emission light. These interfering effects may be reduced by restricting fluorophores to occupy only a fraction of the assayed tissue volume. This can be accomplished by confining fluorophores to a sub-compartment of each cell in the tissue, such as the nucleus. The glucose-sensor was targeted to nuclei of COS7-cells. To determine, whether nuclear glucose levels can be used to track cytosolic changes, nuclear glucose concentrations were quantified as the cells were challenged with external glucose over a range of 0.5 to 10 mM and compared to cytosolic levels. Internal glucose concentrations in both compartments were similar, corresponding to approximately 50% of the external concentration. Taken together, these results indicate that nuclear glucose levels can be used to determine cytosolic levels indirectly, permitting more reliable quantification of fluorescence intensities and providing a tool for measurements not only in cell cultures but also in tissues.
authors.affiliation: Carnegie Institution of Washington, Plant Biology, 260 Panama Street, Stanford, California 94305-4101, USA.
authors.forename: Marcus
authors.initials: M
authors.lastname: Fehr
authors.forename: Sylvie
authors.initials: S
authors.lastname: Lalonde
authors.forename: David W
authors.initials: DW
authors.lastname: Ehrhardt
authors.forename: Wolf B
authors.initials: WB
authors.lastname: Frommer
mesh_terms: D000465:Algorithms; D000818:Animals; D017360:Arabidopsis / Q000235:genetics; D015374:Biosensing Techniques / Q000379:methods*; D019556:COS Cells; D002467:Cell Nucleus / Q000737:chemistry / Q000378:metabolism*; D002522:Chlorocebus aethiops; D003600:Cytosol / Q000737:chemistry / Q000378:metabolism; D003952:Diagnostic Imaging / Q000379:methods*; D031541:Fluorescence Resonance Energy Transfer; D015870:Gene Expression; D005947:Glucose / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000235:genetics; D006706:Homeostasis; D018519:Meristem / Q000235:genetics; D008856:Microscopy, Fluorescence; D009004:Monosaccharide Transport Proteins / Q000235:genetics; D019913:Nuclear Localization Signals / Q000235:genetics; D010957:Plasmids / Q000235:genetics; D013050:Spectrometry, Fluorescence; D014162:Transfection
chemical_list: D009004:Monosaccharide Transport Proteins; D019913:Nuclear Localization Signals; D049452:Green Fluorescent Proteins; D005947:Glucose