Syndecan binding sites in the laminin alpha1 chain G domain.
The laminin alpha1 chain G domain has multiple biological activities. Previously, we identified cell binding sequences in the laminin alpha1 chain G domain by screening 113 synthetic peptide-polystyrene beads for cell attachment activity. Here, we have used a recombinant protein of the laminin alpha1 G domain (rec-alpha1G) and a large set of synthetic peptides to further identify and characterize heparin, cell, and syndecan-4 binding sites in the laminin alpha1 chain G domain. The rec-alpha1G protein promoted both cell attachment and heparin binding (K(D) = 19 nM). Cell attachment to the rec-alpha1G protein was inhibited 60% by heparin and 30% by EDTA. The heparin binding sites were identified by competing heparin binding to the rec-alpha1G protein with 110 synthetic peptides in solution. Only two peptides, AG73 (IC(50) = 147 microM) and AG75 (IC(50) = 206 microM), inhibited heparin binding to rec-alpha1G. When the peptides were compared in a solid-phase heparin binding assay, AG73 showed more heparin binding than AG75. AG73 also inhibited fibroblast attachment to the rec-alpha1G protein, but AG75 did not. Cell attachment to the peptides was studied using peptide-coated plates and peptide-conjugated sepharose beads. AG73 promoted cell attachment in both assays, but AG75 only showed cell attachment activity in the bead assay. Additionally, AG73, but not AG75, inhibited branching morphogenesis of mouse submandibular glands in organ culture. Furthermore, the rec-alpha1G protein bound syndecan-4, and both AG73 and AG75 inhibited this binding. These results suggest that the AG73 and AG75 sites are important for heparin and syndecan-4 binding in the laminin alpha1 chain G domain. These sites may play a critical role in the diverse biological activities involving heparin and syndecan-4 binding.
Graduate School of Environmental Earth Science, Hokkaido University, Sapporo 060-0810, Japan.
Nobuharu
N
Suzuki
Naoki
N
Ichikawa
Shingo
S
Kasai
Masanori
M
Yamada
Norio
N
Nishi
Hiroshi
H
Morioka
Hironobu
H
Yamashita
Yasuo
Y
Kitagawa
Atsushi
A
Utani
Matthew P
MP
Hoffman
Motoyoshi
M
Nomizu
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D016466:CHO Cells; D002448:Cell Adhesion; D002478:Cells, Cultured; D006224:Cricetinae; D006493:Heparin / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D007797:Laminin / Q000737:chemistry / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D010455:Peptides / Q000494:pharmacology; D011485:Protein Binding; D011509:Proteoglycans / Q000737:chemistry / Q000378:metabolism*; D013363:Submandibular Gland / Q000187:drug effects / Q000254:growth & development; D053667:Syndecans
D007797:Laminin; D008562:Membrane Glycoproteins; D010455:Peptides; D011509:Proteoglycans; D053667:Syndecans; C084098:laminin A; D006493:Heparin