engleski

Modifications of the UPR and ERAD Pathways to Improve Yeast Surface Display

The yeast Saccharomyces cerevisiae is a prominent host for the production of recombinant proteins because it can perform protein modifications that are the same or similar to those found in other eukaryotes. At the same time, yeast provides quality control of the proteins produced, resulting in a high level of properly folded proteins. These proteins can be secreted and incorporated into the cell wall, providing their immobilization on a solid surface. Yeast surface display is an attractive alternative to classical immobilization methods because it is cost- effective, less time-consuming, and allows continuous production of immobilized protein. The major drawback is the low efficiency of surface display. There are several approaches to overcome this obstacle. One of them is the manipulation of the secretory pathway to increase the total amount of secreted protein. Overexpression of recombinant proteins increases cell stress because the increased protein load overwhelms protein production and folding mechanisms, increasing the number of misfolded proteins. Such events lead to activation of the unfolded protein response (UPR) and the endoplasmic reticulum-associated degradation (ERAD) pathways. Several published papers have indicated that activation of these pathways leads to decreased protein production. To test how mutations in genes involved in these pathways affect surface display efficiency, we have used two surface display systems in which β- lactamase is displayed using native cell wall proteins Pir2 or Ccw12 as anchors. Mutants used for the surface display contain mutations in IRE1 and YOP1 (involved in the UPR), HRD1, HRD3, DER1 and DOA10 (involved in ERAD). Additionally, we also checked the effect of a mutation in the gene SEC14, which is involved in protein secretion and regulation of UPR. Results showed increased β- lactamase activity in most of the tested strains. Results also showed that the effects of introduced mutations on surface display efficiency differed between two surface display systems.

yeast, surface display, ERAD, UPR

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