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Open Access Highly Accessed Methodology article

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

Carlotta Giorgi123, Anna Romagnoli2, Chiara Agnoletto1, Leda Bergamelli2, Giovanni Sorrentino2, Marisa Brini4, Tullio Pozzan56, Jacopo Meldolesi3, Paolo Pinton1* and Rosario Rizzuto5*

Author Affiliations

1 Department of Experimental and Diagnostic Medicine, Section of General Pathology, Interdisciplinary Center for the Study of Inflammation (ICSI) and LTTA center, University of Ferrara, Ferrara; Italy

2 Aequotech s.r.l., Ferrara, Italy

3 San Raffaele Scientific Institute and IIT Network, Milan, Italy

4 Dept. Biochemistry and Dept. Experimental Veterinary Sciences, University of Padua, Padua, Italy

5 Dept. Biomedical Sciences, University of Padua, and CNR Institute of Neuroscience, Padua Unit, Italy

6 Venetian Institute of Molecular Medicine, Padua, Italy

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BMC Cell Biology 2011, 12:27  doi:10.1186/1471-2121-12-27

Published: 9 June 2011

Abstract

Background

Activation by extracellular ligands of G protein-coupled (GPCRs) and tyrosine kinase receptors (RTKs), results in the generation of second messengers that in turn control specific cell functions. Further, modulation/amplification or inhibition of the initial signalling events, depend on the recruitment onto the plasma membrane of soluble protein effectors.

High throughput methodologies to monitor quantitatively second messenger production, have been developed over the last years and are largely used to screen chemical libraries for drug development. On the contrary, no such high throughput methods are yet available for the other aspect of GPCRs regulation, i.e. protein translocation to the plasma membrane, despite the enormous interest of this phenomenon for the modulation of receptor downstream functions. Indeed, to date, the experimental procedures available are either inadequate or complex and expensive.

Results

Here we describe the development of a novel conceptual approach to the study of cytosolic proteins translocation to the inner surface of the plasma membrane. The basis of the technique consists in: i) generating chimeras between the protein of interests and the calcium (Ca2+)-sensitive, luminescent photo-protein, aequorin and ii) taking advantage of the large Ca2+ concentration [Ca2+] difference between bulk cytosolic and the sub-plasma membrane rim.

Conclusion

This approach, that keeps unaffected the translocation properties of the signalling protein, can in principle be applied to any protein that, upon activation, moves from the cytosol to the plasma membrane.

Thus, not only the modulation of GPCRs and RTKs can be investigated in this way, but that of all other proteins that can be recruited to the plasma membrane also independently of receptor activation.

Moreover, its automated version, which can provide information about the kinetics and concentration-dependence of the process, is also applicable to high throughput screening of drugs affecting the translocation process.