Enhanced laminin binding by alpha-dystroglycan after enzymatic deglycosylation.
Carbohydrate modifications are clearly important to the function of alpha-dystroglycan but their composition and structure remain poorly understood. In the present study, we describe experiments aimed at identifying the alpha-dystroglycan oligosaccharides important for its binding to laminin-1 and carbohydrate-dependent mAbs (monoclonal antibodies) IIH6 and VIA4(1). We digested highly purified skeletal muscle alpha-dystroglycan with an array of linkage-specific endo- and exoglycosidases, which were verified for action on alpha-dystroglycan by loss/gain of reactivity for lectins with defined glyco-epitopes. Notably, digestion with a combination of Arthrobacter ureafaciens sialidase, beta(1-4)galactosidase and beta-N-acetylglucosaminidase substantially degraded SiaAalpha2-3Galbeta1-4GlcNAcbeta1-2Man glycans on highly purified alpha-dystroglycan that nonetheless exhibited enhanced IIH6, VIA4(1) and laminin-1 binding activity. Additional results indicate that alpha-dystroglycan is probably modified with other anionic sugars besides sialic acid and suggest that rare alpha-linked GlcNAc moieties may block its complete deglycosylation with currently available enzymes.
Combs
Ariana C
AC
Department of Physiology, Madison Medical School, University of Wisconsin, 127 Service Memorial Institute, 1300 University Avenue, Madison, WI 53706, USA.
Ervasti
James M
JM
D000911:Antibodies, Monoclonal / Q000737:chemistry; D049030:Dystroglycans / Q000737:chemistry* / Q000378:metabolism*; D006026:Glycoside Hydrolases / Q000378:metabolism*; D006031:Glycosylation; D007797:Laminin / Q000737:chemistry*; D009439:Neuraminidase / Q000378:metabolism; D009844:Oligosaccharides / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding
D000911:Antibodies, Monoclonal; D007797:Laminin; D009844:Oligosaccharides; D049030:Dystroglycans; D006026:Glycoside Hydrolases; D009439:Neuraminidase