title: Expression of antibody fragments with a controlled N-glycosylation pattern and induction of endoplasmic reticulum-derived vesicles in seeds of Arabidopsis.
abstract: Intracellular trafficking and subcellular deposition are critical factors influencing the accumulation and posttranslational modifications of proteins. In seeds, these processes are not yet fully understood. In this study, we set out to investigate the intracellular transport, final destination, N-glycosylation status, and stability of the fusion of recombinant single-chain variable fragments to the crystallizing fragment of an antibody (scFv-Fc) of two antiviral monoclonal antibodies (2G12 and HA78). The scFv-Fcs were expressed in Arabidopsis (Arabidopsis thaliana) seeds and leaves both as secretory molecules and tagged with an endoplasmic reticulum (ER) retention signal. We demonstrate differential proteolytic degradation of scFv-Fcs in leaves versus seeds, with higher degradation in the latter organ. In seeds, we show that secretory versions of HA78 scFv-Fcs are targeted to the extracellular space but are deposited in newly formed ER-derived vesicles upon KDEL tagging. These results are in accordance with the obtained N-glycosylation profiles: complex-type and ER-typical oligomannosidic N-glycans, respectively. HA78 scFv-Fcs, expressed in seeds of an Arabidopsis glycosylation mutant lacking plant-specific N-glycans, exhibit custom-made human-type N-glycosylation. In contrast, 2G12 scFv-Fcs carry exclusively ER-typical oligomannosidic N-glycans and were deposited in newly formed ER-derived vesicles irrespective of the targeting signals. HA78 scFv-Fcs exhibited efficient virus neutralization activity, while 2G12 scFv-Fcs were inactive. We demonstrate the efficient generation of scFv-Fcs with a controlled N-glycosylation pattern. However, our results also reveal aberrant subcellular deposition and, as a consequence, unexpected N-glycosylation profiles. Our attempts to elucidate intracellular protein transport in seeds contributes to a better understanding of this basic cell biological mechanism and is a step toward the versatile use of Arabidopsis seeds as an alternative expression platform for pharmaceutically relevant proteins.
authors.affiliation: Department of Applied Genetics and Cell Biology, University of Natural Resources and Applied Life Sciences, A-1190 Vienna, Austria.
authors.forename: Andreas
authors.initials: A
authors.lastname: Loos
authors.forename: Bart
authors.initials: B
authors.lastname: Van Droogenbroeck
authors.forename: Stefan
authors.initials: S
authors.lastname: Hillmer
authors.forename: Josephine
authors.initials: J
authors.lastname: Grass
authors.forename: Martin
authors.initials: M
authors.lastname: Pabst
authors.forename: Alexandra
authors.initials: A
authors.lastname: Castilho
authors.forename: Renate
authors.initials: R
authors.lastname: Kunert
authors.forename: Mifang
authors.initials: M
authors.lastname: Liang
authors.forename: Elsa
authors.initials: E
authors.lastname: Arcalis
authors.forename: David G
authors.initials: DG
authors.lastname: Robinson
authors.forename: Ann
authors.initials: A
authors.lastname: Depicker
authors.forename: Herta
authors.initials: H
authors.lastname: Steinkellner
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D006031:Glycosylation; D009500:Neutralization Tests; D018515:Plant Leaves / Q000737:chemistry; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D011134:Polysaccharides / Q000737:chemistry; D011401:Promoter Regions, Genetic; D012639:Seeds / Q000737:chemistry*; D057127:Single-Chain Antibodies / Q000096:biosynthesis* / Q000235:genetics / Q000302:isolation & purification
chemical_list: D011134:Polysaccharides; D057127:Single-Chain Antibodies