Figure 6.

Tissue-specific glycosylation controls binding of neurexin 1α to α-dystroglycan. (A) Tissue distribution. Equivalent amounts of proteins isolated by WGA affinity chromatography from mouse brain, skeletal muscle, cardiac muscle, and lung were analyzed by immunoblotting with antibodies to β- and α-dystroglycan (β-DG and α-DG) and by the neurexin overlay assay with Ig–N1α-1. (B) Effect of deglycosylation. Mouse brain and lung proteins were enzymatically deglycosylated by treatment with N-glycosidase F, sialidase and O-glycosidase (left) or chemically deglycosylated by treatment with trifluoromethanesulfonic acid (right). Proteins were separated by SDS-PAGE, and α-dystroglycan was detected by immunoblotting (α-DG antibody) or by neurexin 1α overlay assay with Ig–N1α-1. Note that enzymatic deglycosylation (which only removes part of the complex sugars) activates neurexin 1α binding to lung dystroglycan, whereas complete chemical deglycosylation inhibits neurexin 1α binding without abolishing immunoreactivity. For all panels, numbers on the left indicate positions of the molecular weight markers.