Polycistronic expression of the mitochondrial steroidogenic P450scc system in the HEK293T cell line

Analysis of Activity of Human Steroidogenic Acute Regulatory Protein (STARD1) Expressed in Escherichia coli Cells

One of the main obstacles to the successful use of Escherichia coli cells for steroid transformation in biotechnological processes is inefficient transport of steroid substrates into the cells. Here, we tested the possibility of using human cholesterol transfer protein STARD1 (steroidogenic acute regulatory protein) to increase the efficiency of steroid uptake by bacterial cells. Genetic constructs were obtained for the synthesis in E. coli BL21 (DE3) cells of a truncated version of STARD1 containing protein functional domain (residues 66-285) and STARD1 (66-285)-GFP fusion protein, both carrying bacterial periplasmic targeting sequence pelB at the N-terminus. Analysis of preparations of E. coli/pET22b/STARD1-GFP cells by fluorimetry and Western blotting confirmed that the used expression system ensured the synthesis of the heterologous protein. Using fluorescence spectroscopy, it was demonstrated that the presence of STARD1 in the cells increased the efficiency of assimilation of NBD-labeled cholesterol analogues by E. coli/pET22b/STARD1 cells 1.3-1.6 times (p < 0.05) compared to the wild-type cells, thus demonstrating that human STARD1 exhibits its functional activity in bacterial cells. This opens prospects for optimizing and using a fundamentally new approach to increase the efficiency of steroid uptake by cells - the inclusion of a specific carrier protein in the cell membrane, which can expand the arsenal of methods used to obtain strains of microorganisms for synthesis.

Co-delivery of genes can be confounded by bicistronic vector design

Maximizing the efficiency of nanocarrier-mediated co-delivery of genes for co-expression in the same cell is critical for many applications. Strategies to maximize co-delivery of nucleic acids (NA) focused largely on carrier systems, with little attention towards payload composition itself. Here, we investigated the effects of different payload designs: co-delivery of two individual "monocistronic" NAs versus a single bicistronic NA comprising two genes separated by a 2A self-cleavage site. Unexpectedly, co-delivery via the monocistronic design resulted in a higher percentage of co-expressing cells, while predictive co-expression via the bicistronic design remained elusive. Our results will aid the application-dependent selection of the optimal methodology for co-delivery of genes.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1557/s43579-021-00128-7.

Using a viral 2A peptide-based strategy to reconstruct the bovine P450scc steroidogenic system in S. cerevisiae: Bovine P450scc system expression using 2A peptides

Cytochrome P450scc system performs the first rate-limiting stage of steroidogenesis in mammals. The bovine P450scc system was reconstructed in Saccharomyces cerevisiae, using a foot-and-mouth disease virus 2A peptide (F2A)-based construct, to co-express cytochrome P450scc, adrenodoxin (Adx), and adrenodoxin reductase (AdR). During the translation of the self-processing fusion protein P450scc-F2A-Adx-F2A-AdR, the first and the second linkers are cleaved with different efficiencies (96 % and 11 %, respectively), resulting in the unbalanced expression of individual proteins. The low cleavage efficiency and the relative Adx and AdR protein levels were increased through replacing the second F2A peptide with different sequences and changing the order of Adx and AdR. The P450scc, AdR, and Adx sequences located upstream of the F2A affected F2A processing, to various degrees. Moreover, using molecular dynamics (MD) simulations, we showed that the 2A peptide fused to the C-terminus of Adx formed the steric hindrance during enzymatic complex formation, resulting in the reduction of catalytic activity. Thus, the functional activity of the reconstructed P450scc system was determined not only by the efficiency of 2A peptides but also by the overall sequence of the expressed 2A-polyprotein. Our results can be applied to the development of 2A-based co-translation strategies, to produce other multicomponent protein systems.

Production and Application of Multicistronic Constructs for Various Human Disease Therapies

The development of multicistronic vectors has opened up new opportunities to address the fundamental issues of molecular and cellular biology related to the need for the simultaneous delivery and joint expression of several genes. To date, the examples of the successful use of multicistronic vectors have been described for the development of new methods of treatment of various human diseases, including cardiovascular, oncological, metabolic, autoimmune, and neurodegenerative disorders. The safety and effectiveness of the joint delivery of therapeutic genes in multicistronic vectors based on the internal ribosome entry site (IRES) and self-cleaving 2A peptides have been shown in both in vitro and in vivo experiments as well as in clinical trials. Co-expression of several genes in one vector has also been used to create animal models of various inherited diseases which are caused by mutations in several genes. Multicistronic vectors provide expression of all mutant genes, which allows the most complete mimicking disease pathogenesis. This review comprehensively discusses multicistronic vectors based on IRES nucleotide sequence and self-cleaving 2A peptides, including its features and possible application for the treatment and modeling of various human diseases.