2. Academic Validation
  3. EDEM2 initiates mammalian glycoprotein ERAD by catalyzing the first mannose trimming step

EDEM2 initiates mammalian glycoprotein ERAD by catalyzing the first mannose trimming step

  • J Cell Biol. 2014 Aug 4;206(3):347-56. doi: 10.1083/jcb.201404075.
Satoshi Ninagawa 1,  Tetsuya Okada 2,  Yoshiki Sumitomo 2,  Yukiko Kamiya 3,  Koichi Kato 4,  Satoshi Horimoto 2,  Tokiro Ishikawa 2,  Shunichi Takeda 2,  Tetsushi Sakuma 5,  Takashi Yamamoto 5,  Kazutoshi Mori 6
Affiliations

Affiliations

  • 1 Department of Biophysics, Graduate School of Science, and Department of Radiation Genetics, Graduate School of Medicine, Kyoto University, Kyoto 606-8502, Japan Institute for Molecular Science and Okazaki Institute for Integrative Bioscience, National Institutes of Natural Sciences, Okazaki 444-8787, Japan.
  • 2 Department of Biophysics, Graduate School of Science, and Department of Radiation Genetics, Graduate School of Medicine, Kyoto University, Kyoto 606-8502, Japan.
  • 3 Institute for Molecular Science and Okazaki Institute for Integrative Bioscience, National Institutes of Natural Sciences, Okazaki 444-8787, Japan.
  • 4 Institute for Molecular Science and Okazaki Institute for Integrative Bioscience, National Institutes of Natural Sciences, Okazaki 444-8787, Japan Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya 467-8603, Japan.
  • 5 Department of Mathematical and Life Sciences, Graduate School of Science, Hiroshima University, Hiroshima 739-8526, Japan.
  • 6 Department of Biophysics, Graduate School of Science, and Department of Radiation Genetics, Graduate School of Medicine, Kyoto University, Kyoto 606-8502, Japan mori@upr.biophys.kyoto-u.ac.jp.
PMID: 25092655 DOI: 10.1083/jcb.201404075
Abstract

Glycoproteins misfolded in the endoplasmic reticulum (ER) are subjected to ER-associated glycoprotein degradation (gpERAD) in which Htm1-mediated mannose trimming from the oligosaccharide Man8GlcNAc2 to Man7GlcNAc2 is the rate-limiting step in yeast. In contrast, the roles of the three Htm1 homologues (EDEM1/2/3) in mammalian gpERAD have remained elusive, with a key controversy being whether EDEMs function as mannosidases or as lectins. We therefore conducted transcription activator-like effector nuclease-mediated gene knockout analysis in human cell line and found that all endogenous EDEMs possess mannosidase activity. Mannose trimming from Man8GlcNAc2 to Man7GlcNAc2 is performed mainly by EDEM3 and to a lesser extent by EDEM1. Most surprisingly, the upstream mannose trimming from Man9GlcNAc2 to Man8GlcNAc2 is conducted mainly by EDEM2, which was previously considered to lack enzymatic activity. Based on the presence of two rate-limiting steps in mammalian gpERAD, we propose that mammalian cells double check gpERAD substrates before destruction by evolving EDEM2, a novel-type Htm1 homologue that catalyzes the first mannose trimming step from Man9GlcNAc2.

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