Identification of α-dystroglycan binding sequences in the laminin α2 chain LG4-5 module

The biological activities of the laminin alpha 2 chain LG4-5 module result from interactions with cell surface receptors, such as heparan sulfate proteoglycans and alpha-dystroglycan. In this study, heparin and alpha-dystroglycan binding sequences were identified using 42 overlapping synthetic peptides from the LG4-5 module and using recombinant LG4-5 protein (rec-alpha 2LG4-5). Physiological activities of the active peptides were also examined in explants of submandibular glands. Heparin binding screens showed that the A2G78 peptide (GLLFYMARINHA) bound to heparin and prevented its binding to rec-alpha 2LG4-5. Furthermore, alanine substitution of the arginine residue in the A2G78 site on rec-alpha 2LG4-5 decreased heparin binding activity. When alpha-dystroglycan binding of the peptides was screened, two peptides, A2G78 and A2G80 (VQLRNGFPYFSY), bound alpha-dystroglycan. A2G78 and A2G80 also inhibited alpha-dystroglycan binding of Fec-alpha 2LG4-5. A2G78 and A2G80 specifically inhibited end bud formation of submandibular glands in culture. These results suggest that the A2G78 and A2G80 sites play functional roles as heparan sulfate- and alpha-dystroglycan-binding sites in the module. These peptides are useful for elucidating molecular mechanisms of heparan sulfate- and/or alpha-dystroglycan-mediated biological functions of the laminin alpha 2 chain. (C) 2009 Elsevier B.V. All rights reserved.