Laminin-binding protein 120 from brain is closely related to the dystrophin-associated glycoprotein, dystroglycan, and binds with high affinity to the major heparin binding domain of laminin

• Published in: The Journal of biological chemistry 1993-07, Vol.268 (20), p.14972-14980
• Main Authors: GEE, S. H, BLACHER, R. W, DOUVILLE, P. J, PROVOST, P. R, YURCHENCO, P. D, CARBONETTO, S
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Analytical, structural and metabolic biochemistry; Animals; Binding and carrier proteins; Binding, Competitive; Biological and medical sciences; Brain - metabolism; Chick Embryo; Cytoskeletal Proteins - metabolism; Dystroglycans; Dystrophin - metabolism; Fundamental and applied biological sciences. Psychology; Heparin - metabolism; Laminin - metabolism; Membrane Glycoproteins - metabolism; Molecular Sequence Data; Neurons - metabolism; Peptide Fragments - metabolism; Proteins; Receptors, Laminin - chemistry; Receptors, Laminin - metabolism; Sequence Homology, Amino Acid
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(18)82427-9

When brain proteins separated by SDS-polyacrylamide gel electrophoresis (PAGE) and transferred to nitrocellulose are probe with 125I-labeled laminin, a single broad band of approximately 120 kDa binds laminin specifically. We show here by two-dimensional electrophoresis and protein microsequencing that this band consists of two distinct laminin-binding proteins. One of these is the amyloid precursor protein. The other, laminin-binding protein (LBP) 120, is closely related to the dystrophin-associated glycoprotein, dystroglycan (156 kDa); 5 peptides from purified bovine brain LBP120, ranging in size from 7 to 19 residues, are up to 100% identical to the predicted amino acid sequence of muscle dystroglycan (ibraghimov-Beskrovanaya, O., Ervasti, J. M., Leveille, C. J., Slaughter, C. A., Sernett, S. W., and Campbell, K. P. (1992) Nature 355, 696-702). These protein microsequence data support the data of Ibraghimov-Beskrovnaya et al., which suggest that the dystroglycan precursor is processed into 120/156- and 43-kDa proteins. Moreover, the data suggest a revision in the position of the proposed cleavage site of the precursor. The glycosylation and extracellular localization of LBP120/dystroglycan are consistent with it being a cell surface laminin receptor. LBP120/dystroglycan, either as a native protein, or following SDS-PAGE and transfer to nitrocellulose, binds with high affinity (Kd = 90 nM) to a proteolytic fragment of laminin (E3) containing the major heparin binding domain. This binding is Ca(2+)-dependent and inhibited by low concentrations of heparin. Thus, LBP120/dystroglycan is a major non-integrin laminin receptor whose high affinity interaction with laminin may reflect a structural role in brain and muscle.