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Ultrasensitive detection of cellular protein interactions using bioluminescence resonance energy transfer quantum dot‐based nanoprobes

Sensitive detection of protein interactions is a critical step toward understanding complex cellular processes. As an alternative to fluorescence‐based detection, Renilla reniformis luciferase conjugated to quantum dots results in self‐illuminating bioluminescence resonance energy transfer quantum dot (BRET‐Qdot) nanoprobes that emit red to near‐infrared bioluminescence light. Here, we report the development of an ultrasensitive technology based on BRET‐Qdot conjugates modified with streptavidin ([BRET‐Qdot]‐SA) to detect cell‐surface protein interactions. Transfected COS7 cells expressing human cell‐surface proteins were interrogated with a human Fc tagged protein of interest. Specific protein interactions were detected using a biotinylated anti‐human Fc region specific antibody followed by incubation with [BRET‐Qdot]‐SA. The luciferase substrate coelenterazine activated bioluminescence light emission was detected with an ultra‐fast and ‐sensitive imager. Protein interactions barely detectable by the fluorescence‐based approach were readily quantified using this technology. The results demonstrate the successful application and the flexibility of the BRET‐Qdot‐based imaging technology to the ultrasensitive investigation of cell‐surface proteins and protein–protein interactions. J. Cell. Biochem. 113: 2397–2405, 2012. © 2012 Wiley Periodicals, Inc.