Gene

Secretory pathway

Cell biology

Secretory protein

Biology

Protein biosynthesis

Signal peptide

Protein engineering

Biochemistry

Protein folding

Endoplasmic reticulum

Secretion

Pichia

Computational biology

Glycosylation

Unfolded protein response

Pichia pastoris

Endoplasmic-reticulum-associated protein degradation

Enzyme

Golgi apparatus

Peptide sequence

Heterologous

Recombinant DNA

Applied Microbiology and Biotechnology

Pichia pastoris has been recognized as an important platform for the production of various heterologous proteins in recent years. The strong promoter AOX1, induced by methanol, with the help of the α-pre-pro signal sequence, can lead to a high expression level of extracellular protein. However, this combination was not always efficient, as protein secretion in P. pastoris involves numerous procedures mediated by several cellular proteins, including folding assisted by endoplasmic reticulum (ER) molecular chaperones, degradation through ubiquitination, and an efficient vesicular transport system. Efficient protein expression requires the cooperation of various intracellular pathways. This article summarizes the process of protein secretion, modification, and transportation in P. pastoris. In addition, the roles played by the key proteins in these processes and the corresponding co-expression effects are also listed. It is expected to lay the foundation for the industrial protein production of P. pastoris. Key points • Mechanisms of chaperones in protein folding and their co-expression effects are summarized. • Protein glycosylation modifications are comprehensively reviewed. • Current dilemmas in the overall protein secretion pathway of Pichia pastoris and corresponding solutions are demonstrated.

Pathway engineering facilitates efficient protein expression in Pichia pastoris