Remodeling of the Glycosylation Pathway in the Methylotrophic Yeast Hansenula polymorpha to Produce Human Hybrid-Type N-Glycan

Abstract

As a step forward to achieve the generation of human complex-type N-glycans in the methylotrophic yeast Hansenula polymorpha, we here report the modification of the yeast glycosylation pathway by heterologous expression of the human gene encoding beta-1,2-N-acetylglucosaminyltransferase I (GnTI). For the optimal expression of human GnTI in the yeast Golgi compartment, the catalytic domain of the GnTI was fused to various N-terminal leader sequences derived from the yeast type H membrane proteins. The vectors containing GnTI fusion constructs were introduced into the H. polymorpha och1 Delta single and och1 Delta alg3 Delta double mutant strains expressing the ER-targeted Aspergillus saitoi alpha-1,2 mannosidase, respectively. Both of the glycoengineered Hpoch1 Delta and Hpoch1 Delta Hpalg3 Delta strains were shown to produce successfully the hybrid-type glycans with a monoantennary N-acetylglucosamine (GlcNAc(1)Man(5)GlcNAc(2) and GlcNAc(1)Man(3)GlcNAc(2), respectively) by N-glycan profile analysis of cell wall proteins. Furthermore, by comparative analysis of byproduct formation and the glycosylation site occupancy, we propose that the Hpoch1 Delta strain would be more suitable than the Hpoch1 Delta Hpalg3 Delta strain as a host for the production of recombinant proteins with humanized glycans.