A signal motif retains Arabidopsis ER-α-mannosidase I in the cis-Golgi and prevents enhanced glycoprotein ERAD

Nat Commun. 2019 Aug 16;10(1):3701. doi: 10.1038/s41467-019-11686-9.


The Arabidopsis ER-α-mannosidase I (MNS3) generates an oligomannosidic N-glycan structure that is characteristically found on ER-resident glycoproteins. The enzyme itself has so far not been detected in the ER. Here, we provide evidence that in plants MNS3 exclusively resides in the Golgi apparatus at steady-state. Notably, MNS3 remains on dispersed punctate structures when subjected to different approaches that commonly result in the relocation of Golgi enzymes to the ER. Responsible for this rare behavior is an amino acid signal motif (LPYS) within the cytoplasmic tail of MNS3 that acts as a specific Golgi retention signal. This retention is a means to spatially separate MNS3 from ER-localized mannose trimming steps that generate the glycan signal required for flagging terminally misfolded glycoproteins for ERAD. The physiological importance of the very specific MNS3 localization is demonstrated here by means of a structurally impaired variant of the brassinosteroid receptor BRASSINOSTEROID INSENSITIVE 1.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Motifs
  • Arabidopsis
  • Arabidopsis Proteins / genetics
  • Endoplasmic Reticulum / metabolism*
  • Endoplasmic Reticulum-Associated Degradation*
  • Glycoproteins
  • Golgi Apparatus / metabolism*
  • Plant Proteins / metabolism
  • Protein Kinases / genetics
  • Protein Transport
  • alpha-Mannosidase / metabolism*


  • Arabidopsis Proteins
  • Glycoproteins
  • Plant Proteins
  • Protein Kinases
  • BRI1 protein, Arabidopsis
  • alpha-Mannosidase