Process development for functional membrane receptor production in mammalian cells

Area of Science:

• Biochemistry and Molecular Biology
• Cell Culture and Bioprocessing
• Receptor Pharmacology

Background:

• G-protein coupled receptors (GPCRs) are critical drug targets.
• CHO cells are widely used for recombinant protein expression.
• Optimizing cell culture conditions is essential for maximizing receptor yield and function.

Purpose of the Study:

• To characterize culture conditions for maximum expression and functional activity of serotonin (5HT) and metabotropic glutamate (mGlu) receptors in CHO cells.
• To identify optimal harvesting times and media additives for enhanced receptor studies.

Main Methods:

• Stable expression of 5HT and mGlu receptors in Chinese Hamster Ovary (CHO) cells.
• Ligand binding assays to measure receptor density (5HT receptor).
• Agonist-stimulated GTPγS binding assays to determine functional activity.
• Varied cell culture growth phases, sodium butyrate treatment, temperature, and agitation systems.

Main Results:

• Maximum 5HT receptor density was observed in late-exponential growth phase cells.
• Sodium butyrate and 31°C incubation for 24 hours increased 5HT receptor expression but reduced functional activity.
• mGlu receptor functional activity was significantly reduced in agitated culture systems but restored with medium exchange and 31°C incubation for 48 hours.

Conclusions:

• Cell growth phase and specific culture additives (sodium butyrate, temperature) differentially impact GPCR expression and function.
• Optimized conditions, including temperature shifts and medium exchange, can restore and enhance GPCR functional activity in membrane preparations.
• These findings provide critical insights for maximizing the utility of GPCRs in membrane-based assays and drug discovery.