UniSePT: an engineered broadly applicable Unique Secretory signal PepTide for high-yield biotherapeutic production in mammalian cell-based expression systems

BACKGROUND: The yield of therapeutic proteins in mammalian cell-based production systems is often limited by inefficient secretion and reduced bioactivity caused by incompatible secretory signal peptides (SPs). Therefore, a broadly applicable signal peptide that can be fused to different proteins of interest to enhance their secretion and overall production is needed. RESULTS: To address this challenge, we engineered a robust, broadly applicable Unique Secretory signal PepTide (UniSePT) by combining SP sequences from β-casein (CSN2) and β-lactoglobulin (BLG) proteins of Indian river buffalo. UniSePT demonstrated higher secretion efficiency than commonly used SPs, such as human serum albumin and preproinsulin SP. Importantly, this improved secretion does not compromise the bioactivity of the therapeutic proteins produced. Additionally, UniSePT showed minimal cleavage variability, supporting its compatibility with various therapeutic proteins. CONCLUSION: The newly developed UniSePT enhances the titer and bioactivity of therapeutic proteins in mammalian expression systems. Its broad applicability and improved secretion efficiency make it a promising tool for industrial-scale production, potentially reducing the cost of therapeutic protein production.