Simultaneous readout of multiple FRET pairs using photochromism.

Nature communications (2021-04-02)
Thijs Roebroek, Wim Vandenberg, François Sipieter, Siewert Hugelier, Christophe Stove, Jin Zhang, Peter Dedecker

Förster resonant energy transfer (FRET) is a powerful mechanism to probe associations in situ. Simultaneously performing more than one FRET measurement can be challenging due to the spectral bandwidth required for the donor and acceptor fluorophores. We present an approach to distinguish overlapping FRET pairs based on the photochromism of the donor fluorophores, even if the involved fluorophores display essentially identical absorption and emission spectra. We develop the theory underlying this method and validate our approach using numerical simulations. To apply our system, we develop rsAKARev, a photochromic biosensor for cAMP-dependent protein kinase (PKA), and combine it with the spectrally-identical biosensor EKARev, a reporter for extracellular signal-regulated kinase (ERK) activity, to deliver simultaneous readout of both activities in the same cell. We further perform multiplexed PKA, ERK, and calcium measurements by including a third, spectrally-shifted biosensor. Our work demonstrates that exploiting donor photochromism in FRET can be a powerful approach to simultaneously read out multiple associations within living cells.

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H-89 dihydrochloride hydrate, ≥98% (HPLC), powder
U0126 - CAS 109511-58-2 - Calbiochem, U0126, CAS 109511-58-2, is a potent and specific inhibitor of MEK1 (IC₅₀ = 72 nM) and MEK2 (IC₅₀ = 58 nM). The inhibition is noncompetitive with respect to both ATP and ERK.
Ionomycin, Free Acid, Streptomyces conglobatus - CAS 56092-81-0 - Calbiochem, Ionomycin, Free Acid, Streptomyces conglobatus, CAS 56092-81-0, is a highly specific for divalent cations and more effective than A23187 (Cat. No. 100105) as a mobile ion carrier for Ca2+.
3-Isobutyl-1-methylxanthine - CAS 28822-58-4 - Calbiochem, A cell-permeable, non-specific inhibitor of cAMP and cGMP phosphodiesterases (IC₅₀ = 2-50 µM).
PMA, for use in molecular biology applications, ≥99% (HPLC)