Drosophila Dystroglycan is a target of O-mannosyltransferase activity of two protein O-mannosyltransferases, Rotated Abdomen and Twisted.

Abstract

Recent studies highlighted an emerging possibility of using Drosophila as a model system for investigating the mechanisms of human congenital muscular dystrophies, called dystroglycanopathies, resulting from the abnormal glycosylation of alpha-dystroglycan. Several of these diseases are associated with defects in O-mannosylation, one of the most prominent types of alpha-dystroglycan glycosylation mediated by two protein O-mannosyltransferases. Drosophila appears to possess homologs of all essential components of the mammalian dystroglycan-mediated pathway; however, the glycosylation of Drosophila Dystroglycan (DG) has not yet been explored. In this study, we characterized the glycosylation of Drosophila DG using a combination of glycosidase treatments, lectin blots, trypsin digestion, and mass spectrometry analyses. Our results demonstrated that DG extracellular domain is O-mannosylated in vivo. We found that the concurrent in vivo activity of the two Drosophila protein O-mannosyltransferases, Rotated Abdomen and Twisted, is required for O-mannosylation of DG. While our experiments unambiguously determined some O-mannose sites far outside of the mucin-type domain of DG, they also provided evidence that DG bears a significant amount of O-mannosylation within its central region including the mucin-type domain, and that O-mannose can compete with O-GalNAc glycosylation of DG. We found that Rotated Abdomen and Twisted could potentiate in vivo the dominant-negative effect of DG extracellular domain expression on crossvein development, which suggests that O-mannosylation can modulate the ligand-binding activity of DG. Taken together these results demonstrated that O-mannosylation of Dystroglycan is an evolutionarily ancient mechanism conserved between Drosophila and humans, suggesting that Drosophila can be a suitable model system for studying molecular and genetic mechanisms underlying human dystroglycanopathies.

• Authors: Naosuke Nakamura, Stephanie H Stalnaker, Dmitry Lyalin, Olga Lavrova, Lance Wells, Vladsilav M Panin
• Journal: Glycobiology (Glycobiology) Vol. 20 Issue 3 Pg. 381-94 (Mar 2010) ISSN: 1460-2423 [Electronic] England
• PMID: 19969597 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• Dg protein, Drosophila
• Drosophila Proteins
• Dystroglycans
• Mannosyltransferases
• rt protein, Drosophila
• tw protein, Drosophila
• protein O-mannosyltransferase

Topics

• Animals
• Drosophila (enzymology, metabolism)
• Drosophila Proteins (chemistry, metabolism)
• Dystroglycans (chemistry, metabolism)
• Mannosyltransferases (chemistry, metabolism)
• Mass Spectrometry