O-linked glycosylation in maize-expressed human IgA1

Area of Science:

• Plant biotechnology
• Glycobiology
• Biopharmaceutical development

Background:

• O-linked glycans influence glycoprotein properties like stability and immunogenicity.
• Eukaryotic cell types exhibit distinct O-linked glycan profiles.
• Understanding glycosylation in recombinant proteins is crucial for therapeutic applications.

Purpose of the Study:

• To characterize the O-linked glycan structures of recombinant human IgA1 (hIgA1) expressed in transgenic maize.
• To investigate the post-translational modifications in the hinge region of maize-expressed hIgA1.
• To assess the implications for using transgenic plants as a platform for biopharmaceutical production.

Main Methods:

• Matrix-assisted laser-desorption ionization mass spectrometry (MALDI MS)
• Chromatography
• Amino acid analysis

Main Results:

• Maize-expressed hIgA1 heavy chain (HC) showed extensive proline/hydroxyproline conversions (Pro/Hyp) and arabinosylation (Ara) in the hinge region (approx. 90% modification).
• An average of six arabinose units per hIgA1 molecule was observed.
• Sequence similarity between hIgA1 HC hinge and maize extensin-family hydroxyproline-rich glycoproteins (HRGP) suggests a shared modification pathway.

Conclusions:

• The HC hinge region of maize-expressed hIgA1 serves as a substrate for maize prolyl-hydroxylases and Hyp-glycosyltransferases, mimicking plant HRGP modification.
• This study provides the first description of extensin-like Pro/Hyp conversion and O-linked arabinosylation in a recombinant therapeutic protein from transgenic plants.
• Findings highlight the potential of transgenic plants for producing complex therapeutic proteins with plant-specific glycosylation patterns.