REEMAC Platform

Over the past two decades, rapid production of recombinant proteins has become increasingly useful for biomedical applications such as therapeutic proteins in clinical trials, and life science research, including protein expression and interaction studies, functional activity assays, immunization, protein crystallography, and development of affinity reagents for structure/function analyses. Most of these applications/studies require that purified recombinant proteins possess post-translational modifications necessary for retaining full bioactivity and native conformation. In this regard, compared with bacteria, yeast and insect cells, cultured mammalian cells represent superior host systems because they possess machineries for proper protein folding and post-translational modifications. To fully utilize these super properties for pharmaceutical applications and biomedical research, mammalian cell protein production has yet to overcome important limitations on expression level, stability, large-scale production, time, effort and cost.

To eliminate these bottlenecks associated with mammalian cells, scientists from ATGCell have conducted intensive research for several years to develop a unique and innovative platform technology called Robust Exogenous Expression in MAmmalian Cells (REEMAC). This platform can be used for efficient recombinant protein production and stable cell line setup in mammalian cells with much reduced effort and cost. Currently, there are over 130 target genes successfully expressed under this platform. The targets cover numerous gene families including cytokine, growth factor, cell surface antigen, cytokine receptor, protein kinase, protease, transcription factor, ion channel, transporter, G-protein coupled receptor and nuclear receptor. In principle, REEMAC addressed several key factors that affect the timeline, yield and cost for protein expression and purification/stable cell line setup using cultured mammalian cells, including expression vector structure, choice of host cell lines, gene transfection efficiency, selection, cell culture condition and downstream purification processes, with a core innovation of mammalian expression vector structure.

There are two major advantages of this platform. One is high and long-lasting mammalian cell expression of recombinant proteins that possess proper post-translational modifications, such as glycosylation, phosphorylation, pegylation and acetylation, which are critical for proper folding, stability, functional activity and antigenicity of expressed proteins. It is thus much superior to E. coli, yeast and insect cell expression systems. The other is its rapid and efficient protein/cell line production with low cost.

In order to make REEMAC platform superiority over commercially available counterparts: 1) We have constructed more than 100 immediate vectors by integrating/modifying different expression elements and/or optimizing expression cassette structure; 2) We have examined and compared numerous host cell lines and various cell culture conditions; 3) We have explored novel ways to improve the transfection efficiency, optimize the selection, and minimize the expression silencing during long-term culture; 4) We have optimized the downstream purification processes.

The REEMAC platform is the result of these combined efforts and optimizations. Continued R&D on this platform is still ongoing.

Main characteristics/features of the REEMAC platform:

  • Short cell line generation time, usually requiring only 5-7 weeks
  • Very high expression and efficient secretion, reaching as high as 120 pg/cell/day
  • Stable expression, without significant silencing after continued culture for three months
  • Simple collection of secreted proteins from culture media for downstream processing
  • Easy purification, by single affinity chromatography at >95% purity
  • Fully functional and purified, tag-free proteins.
  • Allow a high-throughput generation of cell lines. One well-trained technician can simultaneously establish and maintain 100-200 cell lines
  • Low cost and time-saving