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J. Biol. Chem., Vol. 281, Issue 38, 28265-28277, September 22, 2006

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A Deletion in the Golgi -Mannosidase II Gene of Caenorhabditis elegans Results in Unexpected Non-wild-type N-Glycan Structures^*

Katharina Paschinger, Matthias Hackl, Martin Gutternigg, Dorothea Kretschmer-Lubich, Ute Stemmer, Verena Jantsch, Günter Lochnit^¶, and Iain B. H. Wilson¹

From the Department für Chemie, Universität für Bodenkultur, A-1190 Wien, Austria, Abteilung für Chromosomenbiologie, Vienna Biocenter II, A-1030 Wien, Austria, and ^¶Institut für Biochemie, Justus-Liebig Universität, D-35292 Giessen, Germany

The processing of N-linked oligosaccharides by -mannosidases in the endoplasmic reticulum and Golgi is a process conserved in plants and animals. After the transfer of a GlcNAc residue to Asn-bound Man₅GlcNAc₂ by N-acetylglucosaminyltransferase I, an -mannosidase (EC 3.2.1.114 [EC] ) removes one 1,3-linked and one 1,6-linked mannose residue. In this study, we have identified the relevant -mannosidase II gene (aman-2; F58H1.1) from Caenorhabditis elegans and have detected its activity in both native and recombinant forms. For comparative studies, the two other cDNAs encoding class II mannosidases aman-1 (F55D10.1) and aman-3 (F48C1.1) were cloned; the corresponding enzymes are, respectively, a putative lysosomal -mannosidase and a Co(II)-activated -mannosidase. The analysis of the N-glycan structures of an aman-2 mutant strain demonstrates that the absence of -mannosidase II activity results in a shift to structures not seen in wild-type worms (e.g. N-glycans with the composition Hex_5-7HexNAc_2-3Fuc₂Me) and an accumulation of hybrid oligosaccharides. Paucimannosidic glycans are almost absent from aman-2 worms, indicative also of a general lack of -mannosidase III activity. We hypothesize that there is a tremendous flexibility in the glycosylation pathway of C. elegans that does not impinge, under standard laboratory conditions, on the viability of worms with glycotypes very unlike the wild-type pattern.

Received for publication, March 27, 2006 , and in revised form, July 24, 2006.

^* This work was supported in part by the Fonds zur Förderung der Wissenschaftlichen Forschung Grants P15475 [GenBank] and P18447 [GenBank] (to I. B. H. W.). 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.

¹ To whom correspondence should be addressed. Tel.: 43-1-36006-6541; Fax: 43-1-36006-6059; E-mail: iain.wilson{at}boku.ac.at.

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