Part:BBa_K4586011
STEAP3
Part Description
STEAP3 is a metallic reductase enzyme that is also known as TSAP6, which is involved in promoting apoptosis and exosome biogenesis and can reduce iron and copper. It has the ability to convert iron from an insoluble ferric to a soluble ferrous form.
Usage
This part is implemented in our system to improve the efficacy of our therapeutic agent by increasing the default level of exosome synthesis within our engineered MSC. The only mechanism discovered is that TSAP6 modulates its downstream transferrin receptor genes, which is a pathway related to exosomal secretion. However, its specific mechanism for promoting exosome secretion is still unknown as shown in figure 1.
Figure 1: This figure illustrates the design of our biological circuit coding for booster genes(SDC4,STEAP3 and NadB) and their role in increasing the synthetic capacity of MSCs to secrete exosomes that carry our therapeutic agent represented in Cas12k/gBAFF-R
Literature Characterization
The study created a reporter construct by joining the C-terminus of CD63, one of the most used exosome markers, to nanoluc (nluc), a tiny and potent bioluminescence reporter10. After progressive centrifugation to eliminate masking signals12, luminescence in the cell-culture supernatant was measured. This reporter gene was co-transfected with plasmids expressing potential candidates for exosome production augmentation.
The study found STEAP3 syndecan-4 (SDC4), and (NadB) as potential synthetic exosome production boosters. Combined expression of these genes significantly increased exosome production, and a tricistronic plasmid vector ( known as exosome production booster), which guarantees that transfected cells receive all boosted genes at a fixed ratio ,produced a 15-fold to 40-fold increase (depending on cell conditions) in the luminescence signal in the supernatant.
Characterization By Mutational Landscape
In order to optimize the function of our parts, we've used the concept of Directed Evolution through applying different mutations and measuring the effects of these mutations on their evolutionary epistatic fitness. As displayed in the chart below, the mutation (W209R) shows the highest epistatic fitness, while the lowest score was associated with the mutation (T85V,Q247N,L193F).
Figure . An illustration of the effects of different mutations on the Epistatic Fitness of STEAP3.
charactrizaion by mathematical modeling
Presence of STEAP3 part will increase the level of engineered exosomes so it plays an effective role to increase the efficacy of the therapeutic agent.
We compared both condition of exosomes production when using booster genes and without it
(1)No booster genes with conditioned release
This Represents the relation between the activation of the internal domain of the syn-noth (represented as red line) and production of exosomes with specific cargo (represented as blue line) as the production of the engineered exosomes is initiated once the internal domain is activated.
(2)Booster gene with conditioned release
This Represents the relation between the activation of the internal domain of the syn-noth (represented as red line) and production of exosomes with specific cargo (represented as blue line) as the production of the engineered exosomes is initiated once the internal domain is activated.
References
Kojima, R., Bojar, D., Rizzi, G., Hamri, G. C. E., El-Baba, M. D., Saxena, P., ... & Fussenegger, M. (2018). Designer exosomes produced by implanted cells intracerebrally deliver therapeutic cargo for Parkinson’s disease treatment. Nature communications, 9(1), 1305. Sequence and Features
- 10COMPATIBLE WITH RFC[10]
- 12COMPATIBLE WITH RFC[12]
- 21INCOMPATIBLE WITH RFC[21]Illegal BglII site found at 1103
- 23COMPATIBLE WITH RFC[23]
- 25COMPATIBLE WITH RFC[25]
- 1000INCOMPATIBLE WITH RFC[1000]Illegal SapI site found at 693
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