Osmotic induction of calcium accumulation in human embryonic kidney cells detected with a high sensitivity FRET calcium sensor.
Calcium serves as a second messenger in glucose-triggered insulin secretion of pancreatic cells. Less is known about sugar signaling in non-excitable cells. Here, the high sensitivity FRET calcium sensor TN-XXL was used to characterize glucose-induced calcium responses in non-excitable human embryonic kidney HEK293T cells. HEK293T cells responded to perfusion with glucose with a sustained and concentration-dependent increase in cytosolic calcium levels. Sucrose and mannitol triggered comparable calcium responses, suggesting that the increase of the calcium concentration was caused by osmotic effects. HEK293T cells are characterized by low endogenous glucose uptake capacity as shown with a high sensitivity glucose sensor. Consistently, when glucose influx was artificially increased by co-expression of GLUT glucose transporters, the glucose-induced calcium increase was significantly reduced. Neither calcium depletion, nor gadolinium or thapsigargin were able to inhibit the calcium accumulation. Taken together, membrane impermeable osmolytes such as sucrose and mannitol lead to an increase in calcium levels, while the effect of glucose depends on the cell's glucose uptake capacity and will thus vary between cell types in the body that differ in their glucose uptake capacity.
Hou
Bi-Huei
BH
Carnegie Institution for Science, Dep. Plant Biology, 260 Panama St., Stanford, CA 94305, USA.
Takanaga
Hitomi
H
Griesbeck
Oliver
O
Frommer
Wolf B
WB
D015374:Biosensing Techniques; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D031541:Fluorescence Resonance Energy Transfer; D005456:Fluorescent Dyes / Q000378:metabolism*; D005682:Gadolinium / Q000494:pharmacology; D005947:Glucose / Q000378:metabolism*; D051272:Glucose Transporter Type 1 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D017136:Ion Transport / Q000187:drug effects / Q000235:genetics; D007668:Kidney / Q000378:metabolism* / Q000473:pathology; D008353:Mannitol / Q000378:metabolism; D009995:Osmosis / Q000187:drug effects; D013395:Sucrose / Q000378:metabolism; D019284:Thapsigargin / Q000494:pharmacology; D014162:Transfection
D005456:Fluorescent Dyes; D051272:Glucose Transporter Type 1; C495677:SLC2A1 protein, human; D008353:Mannitol; D013395:Sucrose; D019284:Thapsigargin; D005682:Gadolinium; D005947:Glucose; D002118:Calcium