Free oligosaccharides in the cytosol of Caenorhabditis elegans are generated through endoplasmic reticulum-Golgi trafficking

Toshihiko Kato, Kumiko Kitamura, Megumi Maeda, Yoshinobu Kimura, Takane Katayama, Hisashi Ashida, Kenji Yamamoto

研究成果査読

33 被引用数 (Scopus)

抄録

Free oligosaccharides (FOSs) in the cytosol of eukaryotic cells are mainly generated during endoplasmic reticulum (ER)-associated degradation (ERAD) of misfolded glycoproteins. We analyzed FOS of the nematode Caenorhabditis elegans to elucidate its detailed degradation pathway. The major FOSs were high mannose-type ones bearing 3-9 Manresidues. About 94% of the total FOSs had one GlcNAc at their reducing end (FOS-GN1), and the remaining 6% had two GlcNAc (FOS-GN2). A cytosolic endo-β-N-acetylglucosaminidase mutant (tm1208) accumulated FOS-GN2, indicating involvement of the enzyme in conversion of FOS-GN2 into FOS-GN1. The most abundant FOS in the wild type was Man 5GlcNAc1, the M5A′ isomer (Manα1- 3(Manα1-6)Manα1-6(Manα1-3)Manβ1-4GlcNAc), which is different from the corresponding M5B′ (Manα1-2Manα1- 2Manα1-3(Manα1-6)Manβ1-4GlcNAc) in mammals. Analyses of FOS in worms treated with Golgi α-mannosidase I inhibitors revealed decreases in Man5GlcNAc1 and increases in Man7GlcNAc 1. These results suggested that Golgi α-mannosidase I-like enzyme is involved in the production of Man5-6-GlcNAc1, which is unlike in mammals, in which cytosolic α-mannosidase is involved. Thus, we assumed that major FOSs in C. elegans were generated through Golgi trafficking. Analysis of FOSs from a Golgi α-mannosidase II mutant (tm1078) supported this idea, because GlcNAc1Man 5GlcNAc1, which is formed by the Golgi-resident GlcNAc-transferase I, was found as a FOS in the mutant. We concluded that significant amounts of misfolded glycoproteins in C. elegans are trafficked to the Golgi and are directly or indirectly retro-translocated into the cytosol to be degraded.

本文言語English
ページ(範囲)22080-22088
ページ数9
ジャーナルJournal of Biological Chemistry
282
30
DOI
出版ステータスPublished - 7月 27 2007

ASJC Scopus subject areas

  • 生化学
  • 分子生物学
  • 細胞生物学

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