Team:ESBS-Strasbourg/proteolux

You are interested in analyzing a specific protein in its natural cell environment? You want to analyze its dynamics, by installing any defined protein concentration in your cell without interfering with the cell’s metabolism? Proteolux offers the solution:

Proteolux’s aim is to offer new and more sophisticated methods for protein analysis. Proteins are the actual active factors within cells and controlling protein concentrations leads to the control over the cell itself. Protein levels are installed by a complex homeostasis of de-novo protein synthesis and protein degradation. There are already some techniques for controlling specific protein expression. However, up to now, there are only a few systems that offer specific control about protein degradation. Most old techniques use protein knock-out or RNA interference to analyze the protein absence phenotype (figure 1).

Figure 1: Overview about the synthesis pathway of proteins and the different layers of regulation. The coding information of the DNA is transcribed into mRNA, which is further translated into proteins. The repression of expression protein can take place on three different layers of regulation. Classic methods include gene knockout or RNA interference, which contain several drawbacks. Proteolux defines a new layer of regulation directly on protein level, which can further regulate DNA and mRNA levels.

Both methods exhibit several disadvantages. Gene knockout allows only the analysis of complete protein absence phenotypes, which creates problems in the case of essential proteins, whose absence is lethal to cells. Additionally, the creation of knock out strains (e.g. knock out mouse) for in-vivo analysis demands 3 generations and therefore in advance preparation of the experiment. RNA interference allows more specific regulation of protein expression than gene knockout. However, the main problems are the delivery of the RNAi, a design that is specific in order to avoid off-target effects. Moreover, the actual amount of protein in the cell cannot be controlled as the silencing percentage differs from interfering RNA to interfering RNA and it is difficult to achieve total silencing. Other disadvantages are the limited duration of the repression and toxic effects on cells.

Proteolux’s specific light-controllable protein degradation system interacts directly on protein level, which allows complete control over the protein level as well as the over DNA and RNA layers. The Proteolux system offers the solution for the drawbacks of the other methods. The extremely high controllability allows fine regulation of any protein concentration, which allows also analysis of essential proteins. Different protein concentrations can be installed over time on demand of the experimenter. In-vivo experiments can be made directly after transfection with the system. Long preparation time before conducting experiments is not needed. The protein can be analyzed in its native conformation, as there is no tagging or fusion with other markers necessary. Furthermore, the metabolism of the cell is not altered, as the system is completely controlled by light. There is no off-target degradation due to the extreme high specificity of the interaction partners of the system. Moreover, the Proteolux system does not exhibit any toxicity to the cells.

The light control of the Proteolux systems provides multiple advantages over the use of classical chemical inducers. The system responds instantly to the light signal, which can be used to specifically regulate its action. Chemical inducers do not respond immediately, due to the diffusion time to get to the place of action. Once the chemical inducer at its side of action it is not possible to turn the system off again. However, light offers this switchable control (on and off) of the system. Furthermore, light does not interact with the host metabolism which allows protein analysis in its unchanged natural environment. Another great advantage of light over chemical molecules is its inexpensiveness and its unlimited availability (summarized in the table below).