HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

J. Biol. Chem., Vol. 282, Issue 30, 22080-22088, July 27, 2007

This Article Full Text Full Text (PDF) Supplemental Data All Versions of this Article: 282/30/22080    most recent M700805200v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Kato, T. Articles by Yamamoto, K. Search for Related Content PubMed PubMed Citation Articles by Kato, T. Articles by Yamamoto, K. Social Bookmarking                      What's this?

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 Ashida¹, and Kenji Yamamoto

From the Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, Kitashirakawa, Sakyo-ku, Kyoto 606-8502 and the Graduate School of Natural Science Technology, Okayama University, Okayama 700-8530, Japan

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 Man residues. 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--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 Man₅GlcNAc₁, the M5A' isomer (Man1-3(Man1-6)Man1-6(Man1-3)Man1-4GlcNAc), which is different from the corresponding M5B' (Man1-2Man1-2Man1-3(Man1-6)Man1-4GlcNAc) in mammals. Analyses of FOS in worms treated with Golgi -mannosidase I inhibitors revealed decreases in Man₅GlcNAc₁ and increases in Man₇GlcNAc₁. These results suggested that Golgi -mannosidase I-like enzyme is involved in the production of Man_5-6-GlcNAc₁, which is unlike in mammals, in which cytosolic -mannosidase is involved. Thus, we assumed that major FOSs in C. elegans were generated through Golgi trafficking. Analysis of FOSs from a Golgi -mannosidase II mutant (tm1078) supported this idea, because GlcNAc₁Man₅GlcNAc₁, 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.

Received for publication, January 29, 2007 , and in revised form, May 25, 2007.

^* This work was supported by the 21st Century COE (Centers of Excellence) Program of the Ministry of Education, Culture, Sports, Science and Technology to the Graduate School of Biostudies and Institute for Virus Research, Kyoto University. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The on-line version of this article (available at http://www.jbc.org) contains supplemental Table SI.

¹ To whom correspondence should be addressed. Tel.: 81-75-753-6277; Fax: 81-75-753-9228; E-mail: ashida{at}lif.kyoto-u.ac.jp.

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

This article has been cited by other articles:

				I. Chantret and S. E H Moore Free oligosaccharide regulation during mammalian protein N-glycosylation Glycobiology, March 1, 2008; 18(3): 210 - 224. [Abstract] [Full Text] [PDF]