Single-Cell NanoBRET Imaging with Green-Range HaloTag Acceptor

Bioluminescence resonance energy transfer (BRET) has gained impetus to monitor protein interactions in proximity. BRET involves the energy transfer from a bioluminescent donor (luciferases) to a fluorescent acceptor. Since bioluminescence is an intrinsic phenomenon, BRET excludes the need for external illumination and serves as a powerful alternative to fluorescence-based systems. However, BRET has not been widely adopted for single-cell imaging applications, mainly due to the low signal output resulting in poor signal-to-noise ratio. In this chapter, we describe a protocol to optimize spatiotemporal BRET imaging by adopting fluorescent HaloTag acceptors, adapting cell culture conditions and microscopic setup.