This Research Topic is part of the series on "Heterologous Protein Expression and Production Platforms: The How, Now and Wow of It". See second Volume
here.
Protein expression is a process involving the synthesis, modification and regulation of proteins in cells of living organisms. When this cellular machinery is harnessed as a powerful laboratory tool for the manufacture of a protein of choice using recombinant DNA technology, it is aptly referred to as recombinant protein production.
Since the emergence of genetic engineering tools, concerted efforts were invested by basic scientists and application specialists to optimize procedures for recombinant protein production in the 1980s. With its many advantages,
Escherichia coli has been the preferred expression host. The fast-growing genetically engineered strains serve as easy-to-handle hosts that grow on cheap media, their genetic toolkit is well-defined, and several vectors with regulatable promoters and antibiotic selection are available, resulting in high yields of recombinant proteins. However, some shortcomings include formation of inclusion bodies producing insoluble proteins, problems of codon bias, improper protein folding, absence of a post-translational modification system, and the accumulation of endotoxins that pose a serious problem when the recombinant protein is to be used for therapeutics. This has resulted in alternative bacterial and nonbacterial host systems, such as
Mycobacterium, some
Bacillus strains,
Caulobacter crescentus, viruses, yeasts, filamentous fungi, algae, plants, or insect and mammalian cell cultures, as well as cell-free expression platforms.
Yeasts, such as
Hansenula, Kluyveromyces, Pichia, Saccharomyces and
Yarrowia, are used as preferred alternatives to prokaryotes and higher eukaryotes, mainly due to their rapid growth in inexpensive and chemically defined media, ease of handling, amenability to large-scale manufacturing, easily manipulatable genetic toolkit (giving rise to an enormous number of genetically engineered yeast strains), expression of both intracellular as well as secretory proteins, and their ability to carry out post-translational modifications.
However, mammalian systems are favoured over bacterial and yeast because of the high quality of proteins they produce, their improved protein solubility, their incorporation of post-translational modifications, their secretion of proteins with high yields, and their efficiency in producing large protein complexes. For this very reason, almost all biopharmaceutical companies globally make rampant use of mammalian-based stable cell lines for manufacturing biologics. Of recent, higher plants and microalgae, such as
Chlamydomonas reinhardtii, Schizochytrium sp., Synechococcus and the diatom
Phaeodactylum tricornutum, are being developed for the production of valuable proteins. They are easily scalable (with implications for inexpensive greenhouses), are at lesser risk of pathogen attack, and are pursued for being the cheapest of all protein expression platforms. Is there an overexpression platform that harbours the advantages of all these systems (in particular, a green platform)?
This Research Topic is of interest to a broad category of Scientists, such as Molecular and Structural Biologists, Geneticists, Biochemists, Clinicians, Biophysicists, Spectroscopists and Process Engineers working toward characterising, designing and producing proteins. It thus invites original research and review articles comprising the use of:
- cell-free, prokaryotic and eukaryotic host expression platforms
- advanced technological developments for improved expression and design of both stable and transient proteins
- recent advances in vector designs and optimization (choice of promoters, hybrid-systems, codon optimization, improving protein solubility etc.)
- easily scalable techniques, as well as computational and statistical approaches, for biopharmaceutical applications.
