Part:BBa_K4586012

NadB

Part Description

NadB is the first enzyme in the NAD biosynthesis pathway that is useful in the production of ATP by increasing the metabolism rate of gene-modified cells through the FAD-dependent oxidation of L-aspartate to iminoaspartate, which has an essential role in exosome synthesis.

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 MSCs. This enzyme can therefore speed up the metabolism of gene-modified cells and, in our project, also accelerate exosome biogenesis 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.

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

Assembly Compatibility:

• 10
  COMPATIBLE WITH RFC[10]
• 12
  COMPATIBLE WITH RFC[12]
• 21
  COMPATIBLE WITH RFC[21]
• 23
  COMPATIBLE WITH RFC[23]
• 25
  INCOMPATIBLE WITH RFC[25]

  Illegal AgeI site found at 406
  Illegal AgeI site found at 1026
  
• 1000
  COMPATIBLE WITH RFC[1000]