Secretory expression, purification and functional characterization of 17β-hydroxysteroid dehydrogenase type 1 from mammalian HEK293T cells

Improvement strategies for transient gene expression in mammalian cells

Mammalian cells are suitable hosts for producing recombinant therapeutic proteins, with Chinese hamster ovary (CHO) and human embryonic kidney 293 (HEK293) cells being the most commonly used cell lines. Mammalian cell expression system includes stable and transient gene expression (TGE) system, with the TGE system having the advantages of short cycles and simple operation. By optimizing the TGE system, the expression of recombinant proteins has been significantly improved. Here, the TGE system and the detailed and up-to-date improvement strategies of mammalian cells, including cell line, expression vector, culture media, culture processes, transfection conditions, and co-expression of helper genes, are reviewed. KEY POINTS: • Detailed improvement strategies of transient gene expression system of mammalian cells are reviewed • The composition of transient expression system of mammalian cell are summarized • Proposed optimization prospects for transient gene expression systems.

A novel dehydrogenase 17β-HSDx from Rhodococcus sp. P14 with potential application in bioremediation of steroids contaminated environment

Steroids are endocrine disrupting compounds in human and are distributed in various environments. Our previous study showed that a marine bacterium Rhodococcus sp. P14 was able to efficiently degrade one typical steroid estradiol. In this study, we showed that P14 could also use other steroids, including estriol and testosterone, as sole carbon source for growth. Two dehydrogenation products, 16-hydroxestrone and androst-4-ene-3, 17-dione, were detected during estriol and testosterone degradation, respectively. By screening the genome, a short chain dehydrogenase gene was identified and named as 17β-HSDx. Expression of 17β-HSDx was induced in P14 when estriol, estradiol or testosterone was used as single carbon source. In addition, 17β-HSDx was shown to have dehydrogenation ability of transforming estriol to 16-hydroxestrone, estradiol to estrone and testosterone to androst-4-ene-3, 17-dione. This is the first short chain dehydrogenase identified in bacteria with dehydrogenation ability on various steroids substrates. Overall, this study reveals that 17β-HSDx has potential application in the bioremediation of steroids contaminated environment.