The MFα signal sequence in yeast-based protein secretion: challenges and innovations'.

Protein secretion in yeast is a complex, multistep process heavily reliant on signal sequences to guide recombinant proteins through the secretory pathway. Among these, the mating factor alpha (MFα) signal sequence from Saccharomyces cerevisiae has emerged as a powerful tool for enhancing the extracellular production of heterologous proteins. This review provides a comprehensive overview of the MFα signal sequence, tracing its historical development and role in advancing our understanding of protein secretion mechanisms, including co- and post-translational secretory pathways. We highlight key studies focused on optimizing the MFα signal sequence for improved secretion efficiency, leading to the development of several highly effective variants. These optimized sequences have significantly increased recombinant protein yield and quality, with notable implications for both research and industrial applications. Additionally, we explore the challenges of MFα-based secretion, including issues of missorting, incorrect processing, and aggregation in the endoplasmic reticulum (ER). We discuss emerging strategies to overcome these bottlenecks, such as fusion with alternative signal sequences and strain engineering. Finally, the review highlights current efforts to develop more robust signal peptides, and underscores the importance of continued innovation in protein secretion systems to meet the growing demand for high-quality recombinant proteins in biotechnological and therapeutic applications. KEY POINTS: • MFα remains the top choice for recombinant protein secretion in yeast • Challenges in secretion: ER aggregation, missorting, and processing errors • Mutated and hybrid signal peptides offer promising solutions.