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Open Access Research

Engineering the yeast Yarrowia lipolytica for the production of therapeutic proteins homogeneously glycosylated with Man8GlcNAc2 and Man5GlcNAc2

Karen De Pourcq13, Wouter Vervecken134, Isabelle Dewerte13, Albena Valevska134, Annelies Van Hecke13 and Nico Callewaert12*

Author Affiliations

1 Unit for Medical Biotechnology, Department for Molecular Biomedical Research, VIB, Technologiepark 927, B-9052, Ghent, Belgium

2 Department of Biochemistry and Microbiology, Ghent University, K.L.-Ledeganckstraat 35, B-9000, Ghent, Belgium

3 Department of Biomedical Molecular Biology, Ghent University, Technologiepark 927, B-9052, Ghent, Belgium

4 Oxyrane Belgium, Technologiepark 3, B-9052, Ghent, Belgium

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Microbial Cell Factories 2012, 11:53  doi:10.1186/1475-2859-11-53

Published: 1 May 2012

Abstract

Background

Protein-based therapeutics represent the fastest growing class of compounds in the pharmaceutical industry. This has created an increasing demand for powerful expression systems. Yeast systems are widely used, convenient and cost-effective. Yarrowia lipolytica is a suitable host that is generally regarded as safe (GRAS). Yeasts, however, modify their glycoproteins with heterogeneous glycans containing mainly mannoses, which complicates downstream processing and often interferes with protein function in man. Our aim was to glyco-engineer Y. lipolytica to abolish the heterogeneous, yeast-specific glycosylation and to obtain homogeneous human high-mannose type glycosylation.

Results

We engineered Y. lipolytica to produce homogeneous human-type terminal-mannose glycosylated proteins, i.e. glycosylated with Man8GlcNAc2 or Man5GlcNAc2. First, we inactivated the yeast-specific Golgi α-1,6-mannosyltransferases YlOch1p and YlMnn9p; the former inactivation yielded a strain producing homogeneous Man8GlcNAc2 glycoproteins. We tested this strain by expressing glucocerebrosidase and found that the hypermannosylation-related heterogeneity was eliminated. Furthermore, detailed analysis of N-glycans showed that YlOch1p and YlMnn9p, despite some initial uncertainty about their function, are most likely the α-1,6-mannosyltransferases responsible for the addition of the first and second mannose residue, respectively, to the glycan backbone. Second, introduction of an ER-retained α-1,2-mannosidase yielded a strain producing proteins homogeneously glycosylated with Man5GlcNAc2. The use of the endogenous LIP2pre signal sequence and codon optimization greatly improved the efficiency of this enzyme.

Conclusions

We generated a Y. lipolytica expression platform for the production of heterologous glycoproteins that are homogenously glycosylated with either Man8GlcNAc2 or Man5GlcNAc2 N-glycans. This platform expands the utility of Y. lipolytica as a heterologous expression host and makes it possible to produce glycoproteins with homogeneously glycosylated N-glycans of the human high-mannose-type, which greatly broadens the application scope of these glycoproteins.