eLife (Oct 2021)

Purified EDEM3 or EDEM1 alone produces determinant oligosaccharide structures from M8B in mammalian glycoprotein ERAD

  • Ginto George,
  • Satoshi Ninagawa,
  • Hirokazu Yagi,
  • Jun-ichi Furukawa,
  • Noritaka Hashii,
  • Akiko Ishii-Watabe,
  • Ying Deng,
  • Kazutoshi Matsushita,
  • Tokiro Ishikawa,
  • Yugoviandi P Mamahit,
  • Yuta Maki,
  • Yasuhiro Kajihara,
  • Koichi Kato,
  • Tetsuya Okada,
  • Kazutoshi Mori

DOI
https://doi.org/10.7554/eLife.70357
Journal volume & issue
Vol. 10

Abstract

Read online

Sequential mannose trimming of N-glycan, from M9 to M8B and then to oligosaccharides exposing the α1,6-linked mannosyl residue (M7A, M6, and M5), facilitates endoplasmic reticulum-associated degradation of misfolded glycoproteins (gpERAD). We previously showed that EDEM2 stably disulfide-bonded to the thioredoxin domain-containing protein TXNDC11 is responsible for the first step (George et al., 2020). Here, we show that EDEM3 and EDEM1 are responsible for the second step. Incubation of pyridylamine-labeled M8B with purified EDEM3 alone produced M7 (M7A and M7C), M6, and M5. EDEM1 showed a similar tendency, although much lower amounts of M6 and M5 were produced. Thus, EDEM3 is a major α1,2-mannosidase for the second step from M8B. Both EDEM3 and EDEM1 trimmed M8B from a glycoprotein efficiently. Our confirmation of the Golgi localization of MAN1B indicates that no other α1,2-mannosidase is required for gpERAD. Accordingly, we have established the entire route of oligosaccharide processing and the enzymes responsible.

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