Journal
GLYCOBIOLOGY
Volume 30, Issue 10, Pages 817-829Publisher
OXFORD UNIV PRESS INC
DOI: 10.1093/glycob/cwaa024
Keywords
alpha-dystroglycan; congenital muscular dystrophy; glycosylation; O-mannosylation; sulfotransferase
Categories
Funding
- NIH/NIGMS [R01GM111939, P41GM103390, P01GM107012, R01GM130915]
- Paul D. Wellstone Muscular Dystrophy Cooperative Research Center grant [1U54NS053672]
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Mutations in multiple genes required for proper O-mannosylation of alpha-dystroglycan are causal for congenital/limb-girdle muscular dystrophies and abnormal brain development in mammals. Previously, we and others further elucidated the functional O-mannose glycan structure that is terminated by matriglycan, [<-GlcA-beta 3-Xyl-alpha 3->(n)]. This repeating disaccharide serves as a receptor for proteins in the extracellular matrix. Here, we demonstrate in vitro that HNK-1 sulfotransferase (HNK-1ST/carbohydrate sulfotransferase) sulfates terminal glucuronyl residues of matriglycan at the 3-hydroxyl and prevents further matriglycan polymerization by the LARGE1 glycosyltransferase. While alpha-dystroglycan isolated from mouse heart and kidney is susceptible to exoglycosidase digestion of matriglycan, the functional, lower molecular weight alpha-dystroglycan detected in brain, where HNK-1ST expression is elevated, is resistant. Removal of the sulfate cap by a sulfatase facilitated dual-glycosidase digestion. Our data strongly support a tissue specific mechanism in which HNK-1ST regulates polymer length by competing with LARGE for the 3-position on the nonreducing GIcA of matriglycan.
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