A proximity-exponential hybridization chain reaction (PEHCR) and its application for nondestructive analysis of membrane protein-protein interactions on living cells

Abstract Though a variety of methods have been developed for the analysis of membrane protein-protein interactions (PPIs), amplified, dynamic and nondestructive analysis in situ is always a challenge. To address this issue, here we develop a method called proximity-exponential hybridization chain reaction (PEHCR). In our strategy, when two membrane proteins approach due to interaction, they will draw their respective oligonucleotide-labeled antibodies together. The proximity of the oligonucleotides thereafter triggers a well-designed enzyme-free exponential hybridization chain reaction, which can output amplified fluorescence imaging signals. As a model, analysis of EGFR-HER2 interactions under the regulation of different activators and inhibitors is achieved. Owing to the superior signal amplification performance, we are able to clearly observe the membrane PPIs by using a common fluorescence microscope. Furthermore, unlike the existing proximity techniques that require enzymes, our enzyme-free strategy avoids the need to use a specific buffer suitable for enzyme catalysis and can be run directly in cell liquid media to maximize the physiological activity of the cells. So, dynamic analysis of membrane PPIs on living cells is achieved, and the cells, after the analysis, are still alive and are available for other usage. The successful implementation of this work enriches the toolbox for the study of membrane PPIs especially on those heterogeneous cell populations with small amount.