A streamlined implementation of the glutamine synthetase-based protein expression system.

Area of Science:

• Biotechnology
• Molecular Biology
• Cell Biology

Background:

• The glutamine synthetase (GS) system is a common method for recombinant protein production.
• Traditional GS systems require extensive cloning and cell line selection, which is time-consuming and labor-intensive.
• Chinese hamster ovary (CHO) cells are frequently used in these expression systems.

Purpose of the Study:

• To streamline the production of recombinant proteins using the GS system.
• To reduce the time and handling required for generating high-protein-expressing cell cultures.
• To improve the efficiency of selecting optimal cell clones for protein expression.

Main Methods:

• Co-expression of green fluorescent protein (GFP) with the target protein in CHO cells.
• Utilizing an internal ribosomal entry site (IRES) for GFP co-expression.
• Employing single-step fluorescence-activated cell sorting (FACS) to select high-GFP-expressing cells.

Main Results:

• A single FACS sorting step yielded stable protein expression levels exceeding 50% of average clones and 40% of the best clones.
• Reduced handling steps by one-third and handling time by 70%.
• Shortened the overall time to produce protein-expressing cultures by approximately 3 weeks.
• Facilitated the production of a difficult-to-assay protein.

Conclusions:

• A streamlined GS-based protein expression system using a single FACS selection step provides sufficient protein yields for most research needs (<10 mg/L).
• This simplified method is advantageous when numerous constructs require screening.
• The approach enhances efficiency and reduces resource investment in recombinant protein production.