Construction of recombinant HEK293 cell lines for the expression of the neurotensin receptor NTSR1

Genome-Wide High-Throughput RNAi Screening for Identification of Genes Involved in Protein Production

With an increasing number of blockbuster drugs being recombinant mammalian proteins, protein production platforms that focus on mammalian proteins have had a profound impact in many areas of basic and applied research. Many groups, both academic and industrial, have been focusing on developing cost-effective methods to improve the production of mammalian proteins that would support potential therapeutic applications. As it stands, while a wide range of platforms have been successfully developed for laboratory use, the majority of biologicals are still produced in mammalian cell lines due to the requirement for posttranslational modification and the biosynthetic complexity of target proteins. An unbiased high-throughput RNAi screening approach can be an efficient tool to identify target genes involved in recombinant protein production. Here, we describe the process of optimizing the transfection conditions, performing the genome-wide siRNA screen, the activity and cell viability assays, and the validation transfection to identify genes involved with protein expression.

Genome-Wide High-Throughput RNAi Screening for Identification of Genes Involved in Protein Production

With an increasing number of blockbuster drugs being recombinant mammalian proteins, protein production platforms that focus on mammalian proteins have had a profound impact in many areas of basic and applied research. Many groups, both academic and industrial, have been focusing on developing cost-effective methods to improve the production of mammalian proteins that would support potential therapeutic applications. As it stands, while a wide range of platforms have been successfully developed for laboratory use, the majority of biologicals are still produced in mammalian cell lines due to the requirement for posttranslational modification and the biosynthetic complexity of target proteins. An unbiased high-throughput RNAi screening approach can be an efficient tool to identify target genes involved in recombinant protein production. Here we describe the process of optimizing the transfection conditions, performing the genome-wide siRNA screen, the activity and cell viability assays and the validation transfection to identify genes involved with protein expression.

Enhanced production of secretory glycoprotein VSTM1-v2 with mouse IgGκ signal peptide in optimized HEK293F transient transfection

VSTM1-v2 is a secretory glycoprotein identified by our laboratory. Our previous study revealed that VSTM1-v2 could promote differentiation and activation of Th17 cells. To explore the role of VSTM1-v2 in the immune system further, a source of abundant high-quality recombinant protein is warranted. However, high-level expression of bioactive VSTM1-v2 is difficult due to its weak secretion capacity. To obtain sufficient recombinant VSTM1-v2, we developed an improved expression and purification system by replacing the native signal peptide with a mouse IgGκ signal peptide that did not alter the protein cleavage site. We also optimized parameters for a transient gene expression system in HEK293F cells suspended in serum-free media with polyethyleneimine. Finally, 3.6 mg/L recombinant VSTM1-v2 protein with N-glycosylation and no less than 95% purity was obtained through one-step purification with Ni affinity chromatography. The final yield after purification was increased by more than 7-fold compared to the yield from our previously reported HEK293T system (from 0.5 mg/L to 3.6 mg/L). More importantly, VSTM1-v2 protein exhibited excellent bioactivity. In conclusion, the improved system is not only a dependable source of abundant bioactive VSTM1-v2 for functional studies but also demonstrates a highly efficient approach for enhancing the production of proteins in a short time period, especially for secretory proteins with poor yields.