Chemically induced dimerization tools are used for actively perturbing signal transduction in live cells, but most existing methods are not able to be repeatedly reversed. In a study published in Nature Methods, Bottone et al. introduce a system called CATCHFIRE (chemically assisted tethering of chimera by fluorogenic-induced recognition), which allows the monitoring of reversibly induced protein proximity. This method relies on the chemical induction of dimerization using a fluorogen, which results in the assembled complex fluorescing, enabling real-time visualization of interactions with precise temporal control.
The CATCHFIRE system comprises two components: the small peptide FIREtag and the small protein domain FIREmate, which are based on a split fluorescence system previously reported by the authors. These components are each fused to a protein of interest. When the tag and mate interact as a result of proximity of the proteins of interest, in presence of a fluorogen, the trimerization causes the system to fluoresce. Removal of the fluorogen quickly reverses this process, allowing the real-time imaging of protein dimerization with high spatiotemporal resolution. The authors demonstrate the versatility and feasibility of their approach by controlling, sensing and tracking several cellular pathways in vitro, including protein trafficking, the secretory pathway, organelle positioning and autophagy. Furthermore, they use CATCHFIRE to design biosensors for studying signal transduction pathways. The fluorogen can also be coupled with various fluorescent molecules, accommodating different imaging requirements.
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