In Vivo Assessment of Protein-Protein Interactions Using BRET Assay

Proteins play an important part in almost all life activities and across all organisms. Proteins occasionally act on their own but rather fulfill most of their biological tasks by cooperating with other proteins or ligand molecules. The bioluminescence resonance energy transfer (BRET) assay serves to measure dynamic events such as protein-protein or protein-ligand interactions in vitro or in-vivo. With several inherent attributes such as rapid and fairly sensitive ratio-metric measurements, assessment of interactions irrespective of protein location within the cellular compartment, cost-effectiveness consenting to high-throughput screening compatibility, makes BRET a popular genetic reporter-based assay system for protein-protein interaction (PPI) studies. Based on the Förster principle, BRET allows to judge if the proximity has been achieved between the interacting partners. In recent years, the BRET application has emerged as a significantly versatile assay format by using multiple detection devices such as a plate reader or in-vivo optical imaging platform, or even a bioluminescence microscope has expanded its scope for advancing PPI studies. Beyond the scope of quantitative measurement of PPIs, molecular optical imaging applications based on BRET assay have expanded the scope for screening pharmacological compounds by unifying live cell and in-vivo animal-/plant-based experiments using the same platform technology. In this chapter, we have given intricate methodological details for performing in-vitro and in-vivo BRET experiments, primarily by using donor/acceptor reporter protein combinations.