A Bioluminescent Detection of Calcium-Induced Protein Translocation

An experimental technique for detecting protein translocation to the plasma membrane has been developed by the authors of the publication below:

Translocation of signalling proteins to the plasma membrane revealed by a new bioluminescent procedure.

C Giorgi, A Romagnoli, C Agnoletto, L Bergamelli, G Sorrentino, M Brini, T Pozzan, J Meldolesi, P Pinton, & R Rizzuto. 2011. BMC Cell Biology. 12:27.

Department of Experimental and Diagnostic Medicine, Section of General Pathology, Interdisciplinary Center for the Study of Inflammation (ICSI) and LTTA center, University of Ferrara, Italy. Aequotech s.r.l., Ferrara, Italy. Vita-Salute San Raffaele Scientific Institute and IIT Network, Milan, Italy. Dept. Biochemistry and Dept. Experimental Veterinary Sciences, University of Padua, Italy. Dept. Biomedical Sciences, University of Padua, and CNR Institute of Neuroscience, Padua Unit, Italy. Venetian Institute of Molecular Medicine, Padua, Italy.

They have developed this method making a use of calcium-sensitive photoprotein, aequorin from jellyfish (aequorea victoria).

Aequorin:
- Bioluminescent protein with an emission peak at 470 nm (blue);
- About 200 amino acids in length;
- A calcium sensor with a property of a logarithmic correlation between [calcium] and light emission; the strength of the light emission upon calcium binding is said to be proportional to ≈ the 3rd power of the calcium concentration (Pinton et al. 2007).

Not only the reported advantages of this method over those previously utilised for a similar purpose (e.g. GFP probes, β-galactosidase complementation, or more traditional immunocytochemistry followed by analysing sub-cellular fractions), the established property of bioluminescence by aequorin on calcium binding as above, means that the light signal could be numerically evaluated to estimate [calcium] at which the subject molecule is recruited to the plasma membrane upon receptor activation as well as the time it takes.

With no doubt such detailed information would provide useful parameters in relevant model simulations.

Please find about the method in detail in their original publication.


Reference
Pinton P, Rimessi A, Romagnoli A, Prandini A, Rizzuto R. 2007. Biosensors for the detection of calcium and pH. Methods Cell Biol. 80: 297-325.