For this Friday blog, here’s a sampling of two recent papers highlighting use of the small, bright, NanoLuc luciferase in interesting ways.
Bioluminescence-based hormone:receptor binding studies
A review by Ya-Li Liu and Zhan-Yun Guo, published this week in Amino Acids summarizes recent work of the authors and others using NanoLuc luciferase labeled protein/peptide hormones in receptor binding assays. Typically, studies assessing binding of hormones to receptors have used radioactive tracers. The brightness of NanoLuc luciferase makes bioluminescence an attractive alternative as a sensitive and safer option. Because cell membrane receptors are difficult to purify in quantity, the amounts available for experiments are usually limited. Therefore, tracers used in binding assays need to have a high affinity for the receptor, must not interfere with binding, and must be highly sensitive.
The authors summarize their own work using several different protein/peptide hormones attached to NanoLuc luciferase by either chemical or genetic fusion methods. They discuss how to prepare NanoLuc fusions and chemical conjugates and illustrate with example studies using both methods. Studies using relaxin and ghrelin are highlighted as examples of chemically conjugated NanoLuc tracers, and results using the leukemia inhibitory factor cytokine and erythropoietin are presented as examples of genetic fusions.
Compared to conventional radioligands, these bioluminescent molecules had higher sensitivity and better handling, shelf-life and safety considerations. Although NanoLuc is a very small luciferase molecule, it is much larger than radioactive tracers, therefore, the authors also discuss the additional considerations and optimization required to ensure that the NanoLuc molecule does not interfere with protein folding or receptor binding of the protein/peptide in these types of study.
Here’s the paper:
Liu, Y-L., and Guo, Y. (2016) Novel bioluminescent binding assays for interaction studies of protein/peptide hormones with their receptors. Amino Acids (2016) 48, 1151–1160.
Detecting antibody binding by smartphone
A recent Analytical Chemistry paper highlighted an interesting new method for detecting antibodies in solution using a BRET-based assay. The authors used NanoLuc luciferase and a green fluorescent protein kept in close proximity by a linker molecule containing antibody binding epitopes. In the absence of antibody, the NanoLuc and GFP are close together, generating a green-blue BRET signal. Upon antibody binding, the reporter molecules are driven apart, eliminating or reducing the BRET signal and causing a color change from green-blue to blue that could be detected using a smartphone camera. Subsequent analysis of the images required use of a smartphone App.
The authors showed that the assay could detect down to 10pmol antibody in buffer and 100pmol in plasma. They point out the advantages of bioluminescence over fluorescence-based assays due to reduced background, and over ELISA-based assays by removing the need for washes. The paper includes imagery showing the luminescence readout on a smartphone screen.
Read more about antibody binding in this paper:
Arts, R. et al (2016) Sensor Proteins and a Smartphone. Anal. Chem. 88, 4525−4532.
Learn more about NanoLuc luciferase here.