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Screening for glycosylphosphatidylinositol-modified cell wall proteins in Pichia pastoris and their recombinant expression on the cell surface.

ABSTRACT: Glycosylphosphatidylinositol (GPI)-anchored glycoproteins have various intrinsic functions in yeasts and different uses in vitro. In the present study, the genome of Pichia pastoris GS115 was screened for potential GPI-modified cell wall proteins. Fifty putative GPI-anchored proteins were selected on the basis of (i) the presence of a C-terminal GPI attachment signal sequence, (ii) the presence of an N-terminal signal sequence for secretion, and (iii) the absence of transmembrane domains in mature protein. The predicted GPI-anchored proteins were fused to an alpha-factor secretion signal as a substitute for their own N-terminal signal peptides and tagged with the chimeric reporters FLAG tag and mature Candida antarctica lipase B (CALB). The expression of fusion proteins on the cell surface of P. pastoris GS115 was determined by whole-cell flow cytometry and immunoblotting analysis of the cell wall extracts obtained by ?-1,3-glucanase digestion. CALB displayed on the cell surface of P. pastoris GS115 with the predicted GPI-anchored proteins was examined on the basis of potential hydrolysis of p-nitrophenyl butyrate. Finally, 13 proteins were confirmed to be GPI-modified cell wall proteins in P. pastoris GS115, which can be used to display heterologous proteins on the yeast cell surface.

SUBMITTER: Zhang L

PROVIDER: S-EPMC3754174 | biostudies-literature | 2013 Sep

REPOSITORIES: biostudies-literature

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Screening for glycosylphosphatidylinositol-modified cell wall proteins in Pichia pastoris and their recombinant expression on the cell surface.

Zhang Li L Liang Shuli S Zhou Xinying X Jin Zi Z Jiang Fengchun F Han Shuangyan S Zheng Suiping S Lin Ying Y

Applied and environmental microbiology 20130708 18

Glycosylphosphatidylinositol (GPI)-anchored glycoproteins have various intrinsic functions in yeasts and different uses in vitro. In the present study, the genome of Pichia pastoris GS115 was screened for potential GPI-modified cell wall proteins. Fifty putative GPI-anchored proteins were selected on the basis of (i) the presence of a C-terminal GPI attachment signal sequence, (ii) the presence of an N-terminal signal sequence for secretion, and (iii) the absence of transmembrane domains in matu ...[more]

PMID: 23835174

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Project description:In order to produce therapeutic glycoproteins modified with human-like N-glycan structures, much progress has been achieved toward the humanization of N-glycosylation pathways in yeasts. In this study, a Pichia pastoris mutant Glyco4, which has a humanized N-glycosylation pathway and could successfully generate the human-like N-glycans, was carefully characterized. Glyco4 displays a significant growth delay and cell wall defects. Comparative transcriptomics reveals that manipulating the N-glycosylation pathway could notably affect the expression pattern of numerous biological pathways in Glyco4. Among the differentially expressed genes, the down-regulation of PpSPI1 was proven to be the main cause of the cell wall defects in Glyco4. Deletion of PpSPI1 in P. pastoris GS115 strain presented growth delay and weaker resistance to cell wall/membrane perturbing agents. PpSpi1 was shown to be a glycosylphosphatidylinositol-anchored cell wall glycoprotein and involved in the formation of the mannoprotein layer on the outer surface of cell wall. Overexpressing PpSPI1 in Glyco4 could partially recover the cell wall defects and also improve its resistance to cell wall perturbing agents and osmotic stress. Thus, overexpression of PpSpi1 is a useful strategy to facilitate P. pastoris industrial applications in the manufacture of human glycoproteins. IMPORTANCE Engineering of biological pathways in various microorganisms is a promising direction for biotechnology. Since the existing microbial cells have evolved over a long period of time, any artificial engineering may cause some unexpected and harmful effects on them. Systematically studying and evaluating these engineered strains are very important and necessary. In order to produce therapeutic proteins with human-like N-glycan structures, much progress has been achieved toward the humanization of N-glycosylation pathways in yeasts. The properties of a P. pastoris strain with humanized N-glycosylation machinery were carefully evaluated in this study. Our work has identified a key glycoprotein (PpSpi1) responsible for the poor growth and morphological defects of this glycoengineered strain. Overexpression of PpSpi1 could significantly rescue the growth defect of the glycoengineered P. pastoris and facilitate its future industrial applications.

Project description:BackgroundEscherichia coli phytase is an acidic histidine phytase with great specific activity. Pichia pastoris is a powerful system for the heterologous expression of active and soluble proteins which can express recombinant proteins in high cell density fermenter without loss of product yield and efficiently secrete heterologous proteins into the media. Recombinant protein expression is influenced by expression conditions such as temperature, concentration of inducer, and pH. By optimization, the yield of expressed proteins can be increase. Response surface methodology (RSM) has been widely used for the optimization and studying of different parameters in biotechnological processes.ObjectivesIn this study, the expression of synthetic appA gene in P. pastoris was greatly improved by adjusting the expression condition.Materials and methodsThe appA gene with 410 amino acids was synthesized by P. pastoris codon preference and cloned in expression vector pPinkα-HC, under the control of AOX1 promoter, and it was transformed into P. pastoris GS115 by electroporation. Recombinant phytase was expressed in buffered methanol-complex medium (BMMY) and the expression was analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and enzymatic assay. To achieve the highest level of expression, methanol concentration, pH and temperature were optimized via RSM. Finally, the optimum pH and temperature for recombinant phytase activity was determined.ResultsEscherichia coli phytase was expressed in P. pastoris under different cultivation conditions (post-induction temperature, methanol concentration, and post-induction pH). The optimized conditions by RSM using face centered central composite design were 1% (v/v) methanol, pH = 5.8, and 24.5°C. Under the optimized conditions, appA was successfully expressed in P. pastoris and the maximum phytase activity was 237.2 U/mL after 72 hours of expression.ConclusionsBy optimization of recombinant phytase expression in shake flask culture, we concluded that P. pastoris was a suitable host for high-level expression of phytase and it can possess high potential for industrial applications.

Project description:High-level expression and secretion of heterologous proteins in yeast cause an increased energy demand, which may result in altered metabolic flux distributions. Moreover, recombinant protein overproduction often results in endoplasmic reticulum (ER) stress and oxidative stress, causing deviations from the optimal NAD(P)H regeneration balance. In this context, overexpression of genes encoding enzymes catalyzing endogenous NADPH-producing reactions, such as the oxidative branch of the pentose phosphate pathway, has been previously shown to improve protein production in Pichia pastoris (syn. Komagataella spp.). In this study, we evaluate the overexpression of the Saccharomyces cerevisiaePOS5-encoded NADH kinase in a recombinant P. pastoris strain as an alternative approach to overcome such redox constraints. Specifically, POS5 was cooverexpressed in a strain secreting an antibody fragment, either by directing Pos5 to the cytosol or to the mitochondria. The physiology of the resulting strains was evaluated in continuous cultivations with glycerol or glucose as the sole carbon source, as well as under hypoxia (on glucose). Cytosolic targeting of Pos5 NADH kinase resulted in lower biomass-substrate yields but allowed for a 2-fold increase in product specific productivity. In contrast, Pos5 NADH kinase targeting to the mitochondria did not affect growth physiology and recombinant protein production significantly. Growth physiological parameters were in silico evaluated using the recent upgraded version (v3.0) of the P. pastoris consensus genome-scale metabolic model iMT1026, providing insights on the impact of POS5 overexpression on metabolic flux distributions.IMPORTANCE Recombinant protein overproduction often results in oxidative stress, causing deviations from the optimal redox cofactor regeneration balance. This becomes one of the limiting factors in obtaining high levels of heterologous protein production. Overexpression of redox-affecting enzymes has been explored in other organisms, such as Saccharomyces cerevisiae, as a means to fine tune the cofactor regeneration balance in order to obtain higher protein titers. In the present work, this strategy is explored in P. pastoris In particular, one NADH kinase enzyme from S. cerevisiae (Pos5) is used, either in the cytosol or in mitochondria of P. pastoris, and its impact on the production of a model protein (antibody fragment) is evaluated. A significant improvement in the production of the model protein is observed when the kinase is directed to the cytosol. These results are significant in the field of heterologous protein production in general and in particular in the development of improved metabolic engineering strategies for P. pastoris.

Dataset Information

Screening for glycosylphosphatidylinositol-modified cell wall proteins in Pichia pastoris and their recombinant expression on the cell surface.

Publications

Screening for glycosylphosphatidylinositol-modified cell wall proteins in Pichia pastoris and their recombinant expression on the cell surface.

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