Spatial Control of Inducible Cre-Mediated Recombination Using Cyanine Photocages

Optical control over protein expression could provide a means to interrogate a range of biological processes. One approach has employed caged ligands of the estrogen receptor (ER) in combination with broadly used ligand-dependent Cre recombinase proteins. Existing approaches used UV or blue wavelengths, which hinders their application in tissue settings. Additionally, issues of payload diffusion can impede fine spatial control over the recombination process. Here we detail the chemical optimization a near-infrared (NIR) light-activated variant of the ER antagonist cyclofen. These studies result in modification of both the caging group and payload with lipophilic ¬n-butyl esters. The appendage of esters to the cyanine cage improves cellular uptake and retention. The installation of a 4-piperidyl ester enables high spatial resolution of the light-initiated Cre-mediated recombination event. These studies describe chemical modifications with potentially general utility for improving spatial control of intracellular caging strategies. Additionally, these efforts will enable future applications that use these molecules in complex physiological settings. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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