Site-specific sub-cellular delivery of nanoFRET ion sensors in live cells – nanoFRET²

Imaging Ca microdomains linked to a specific molecule
Summary: Intracellular Ca2+ is a second messenger in a number of cellular reactions (metabolism,
gene expression, vesicular trafficking…). This signalling is made specific through Ca gradients highly
localized and of very short life time (ms). Ca sensitive dyes has disclosed the existence of Ca
transients, but their exact amplitudes and their precise localization is still unknown. Two reasons lag
behind it: the number of Ca sensing molecule in the vicinity of the molecules of interest can be low in
respect to the number of divalent cations accumulating at the intracellular mouth of a channel receptor
such as NMDAR for instance. In addition, ions and dyes gradients collapse quickly due to diffusion.
Our aim has been therefore to concentrate Ca sensitive molecules at the surface of a slowly diffusing
molecule (here a Q Dot) with the idea to ultimately fix it on an antigenic epitope of the molecule of
interest. The use of QDots as cargo molecules may make it possible to localise the nanobiosensor, in
the green, while simultaneously exciting by FRET the dye, itself emitting in the red.