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N-linked oligosaccharide processing is not necessary for glycoprotein secretion in plants
P Lerouge1, A C Fichette-Lainé, A Chekkafi
1Centre Régional Universitaire de Spectroscopie, CNRS-URA 464, Mont Saint Aignan, France.
The Plant Journal : for Cell and Molecular Biology
|October 1, 1996
Summary
Secretion of glycoproteins from sycamore cells does not require fully processed N-glycans. An immature N-glycan structure (Glc3Man7GlcNAc2) is sufficient for efficient glycoprotein transport to the extracellular compartment.
Area of Science:
- Plant cell biology
- Glycobiology
- Molecular biology
Background:
- N-glycans play crucial roles in protein folding, stability, and secretion.
- Previous studies suggested N-glycosylation is essential for glycoprotein secretion.
Purpose of the Study:
- To investigate the role of N-glycan processing in glycoprotein secretion from suspension-cultured sycamore cells.
- To determine if incompletely processed N-glycans can support glycoprotein secretion.
Main Methods:
- Utilized castanospermine, a glycan-processing inhibitor, to induce accumulation of immature N-glycans.
- Identified the structure of the immature N-glycan as Glc3Man7GlcNAc2 using labeling, affinity chromatography, and NMR.
- Assessed glycoprotein transport to the extracellular compartment in the presence of castanospermine.
Main Results:
- Castanospermine treatment led to the accumulation of a single immature N-glycan (Glc3Man7GlcNAc2).
- Glycoprotein secretion was not inhibited by castanospermine, despite the presence of unprocessed N-glycans.
- The immature Glc3Man7GlcNAc2 glycan was found to be sufficient for efficient glycoprotein secretion.
Conclusions:
- N-glycosylation is not a strict prerequisite for glycoprotein secretion in suspension-cultured sycamore cells.
- An unprocessed N-glycan structure is sufficient to mediate the efficient secretion of glycoproteins.
- These findings challenge previous assumptions about the necessity of complete N-glycan maturation for secretion.