Beta1 integrin and alpha-dystroglycan binding sites are localized to different laminin-G-domain-like (LG) modules within the laminin alpha5 chain G domain.
Laminins are a group of extracellular-matrix proteins important in development and disease. They are heterotrimers, and specific domains in the different chains have specialized functions. The G domain of the alpha5 chain has now been produced in transfected mammalian cells as single modules and two tandem arrays, alpha5LG1-3 and alpha5LG4-5 (LG is laminin G domain-like). Using these fragments we produced specific polyclonal antibodies functional in immunoblotting and immunofluorescence studies and in solid-phase assays. Both alpha5LG tandem arrays had physiologically relevant affinities for sulphated ligands such as heparin and sulphatides. Cells adhered to these fragments and acquired a spread morphology when plated on alpha5LG1-3. Binding of integrins alpha3beta1 and alpha6beta1 was localized to the alpha5LG1-3 modules, and alpha-dystroglycan binding was localized to the alpha5LG4-5 modules, thus locating these activities to different LG modules within the laminin alpha5 G domain. However, both these activities were of relatively low affinity, indicating that integrin-mediated cell adhesion to the laminin 10/11 alpha5G domain depends on contributions from the other chains of the heterotrimer and that high-affinity alpha-dystroglycan binding could be dependent on specific Ca(2+)-ion-co-ordinating amino acids absent from alpha5LG4-5.
Yu
Hao
H
Department of Cell and Molecular Biology, Section of Cell and Developmental Biology, BMC, B12, Lund University, SE-221 84 Lund, Sweden.
Talts
Jan F
JF
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D003598:Cytoskeletal Proteins / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D017931:DNA Primers; D049030:Dystroglycans; D019012:Integrin beta1 / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D007700:Kinetics; D007797:Laminin / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D008024:Ligands; D008099:Liver / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D051379:Mice; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013431:Sulfates / Q000378:metabolism
D003598:Cytoskeletal Proteins; D017931:DNA Primers; D019012:Integrin beta1; D007797:Laminin; D008024:Ligands; D008562:Membrane Glycoproteins; D011994:Recombinant Proteins; D013431:Sulfates; C097043:laminin alpha5; D049030:Dystroglycans