Secreted Luciferase from Gaussia Copepod

In the ocean you may find useful molecules, for instance Gaussia Luciferase (GLuc). This is a pretty novel biomiluminescent reporter encoded by a gene isolated from the marine copepod Gaussia princeps. This luciferase does not require ATP and catalyzes the oxidation of the substrate coelenterazine in a reaction that emits light (peak at 470-480 nm) like Renilla and Nanoluc luciferase. However, GLuc is naturally secreted like SEAP, so after synthesis it does not remain in the cytoplasm.
A secreted reporter offers interesting opportunies in assay development. For instance, in comparison with intracellular reporters, a secreted reporter can provide:
  • measurability in the cell culture supernatant,
  • no requirement for complex cell lysis and sample preparation,
  • a simple model to test big-scale recombinant protein manufacturing.
Secreted-reporters can be also used in vivo: the reporter activity can be monitored in blood/urine and complement more expensive in vivo bioluminescence imaging approaches (ok, I’m a fun of in vivo imaging so I can not emotionally support very well this trend). Anyway, recently I’ve observed some nice jobs with secreted reporters. For instance:
Weber and colleagues from the Swiss Federal Institute of Technology have implemented in a mouse a synthetic time-delay gene circuit (composed of a genetic switch, diode, capacitor, resistor, transistor and lamp) in which the lamp was the secreted SEAP reporter gene.
Wurdinger and colleagues reports to be able to assay in just 5 μL of blood (a very little drop) the presence of secreted Gaussia Luciferase, demonstrating that Gluc assay is 1000 fold more sensitive than SEAP assay.
Santos and colleagues recently described on Nature Medicine a membrane anchored external GLuc (termed extGluc) genetically engineered through the addition of a CD8 transmembrane domain to the carboxy terminus of the enzyme. The strategy to put the reporter outside the cell should be advantageous: the substrate do not need to enter the cell and variability previously inferred to drug-resistant genes should be avoided. In effect, the new reporter was enough sensitive to monitor in vivo T cells by means of classical bioluminescence imaging on a IVIS workstation.
----References---- Weber, W., Stelling, J., Rimann, M., Keller, B., Daoud-El Baba, M., Weber, C.C., Aubel, D., Fussenegger, M. (2007). A synthetic time-delay circuit in mammalian cells and mice. Proceedings of the National Academy of Sciences, 104(8), 2643-2648. DOI: 10.1073/pnas.0606398104
Santos, E., Yeh, R., Lee, J., Nikhamin, Y., Punzalan, B., Punzalan, B., Perle, K., Larson, S., Sadelain, M., and Brentjens, R. (2009). Sensitive in vivo imaging of T cells using a membrane-bound Gaussia princeps luciferase Nature Medicine, 15 (3), 338-344 DOI: 10.1038/nm.1930 .
Wurdinger, T., Badr, C. and Tannous, B. (2008). Gaussia luciferase blood level as an index of cell growth and proliferation. Nature Methods, Wurdinger T, Badr C, Pike L, Badr C, de Klein R, Weissleder R, Breakefield XO, Tannous BA. (2008) A secreted luciferase for ex vivo monitoring of in vivo processes. Nature Methods 5:171-173 doi: 10.1038/nmeth.1177