title: Cyclic peptides from the loop region of the laminin alpha 4 chain LG4 module show enhanced biological activity over linear peptides.
abstract: Laminins, heterotrimeric glycoproteins in the basement membrane, are involved in diverse biological activities. So far, five alpha, three beta, and three gamma chains have been identified, and at least 15 laminin isoforms exist composed of various combinations of the different three chains. The major cell-surface receptors for laminins are integrins and proteoglycans, such as dystroglycans and syndecans. Previously, we reported that synthetic peptide A4G82 (TLFLAHGRLVFM, mouse laminin alpha4 chain residues 1514-1525) showed strong cell attachment and syndecan binding activities. On the basis of the crystal structure of the LG module and sequence alignment, A4G82 is located in the connecting loop region between beta-strands E and F in the laminin alpha4 chain LG4 module. Here, we have focused on the structural importance of this E-F loop region for the biological activity of the alpha4 chain LG4 module. To determine the importance of the loop structure, we synthesized peptide A4G82X (cyclo-A4G82X, Cys-TLFLAHGRLVFX-Cys, X= norleucine), which was cyclized via disulfide bridges at both the N- and C-termini. The cyclic peptides derived from A4G82X inhibited the heparin binding activity of the alpha4 chain G domain and promoted HT-1080 cell attachment better than the corresponding linear peptides. We determined FLAHGRLVFX as a minimal sequence of cyclo-A4G82X important for cell adhesion and heparin binding using a series of truncated peptides. Moreover, HT-1080 cell attachment to the cyclic peptides was more efficiently blocked by heparin than cell attachment to the linear peptides. Furthermore, the cyclic peptides showed significantly enhanced syndecan-2-mediated cell attachment activity. These results indicate that the activity of A4G82 is highly conformation-dependent, suggesting that the E-F loop structure is crucial for its biological activity.
authors.affiliation: Graduate School of Environmental Earth Science, Hokkaido University, Sapporo 060-0810, Japan.
authors.forename: Fumiharu
authors.initials: F
authors.lastname: Yokoyama
authors.forename: Nobuharu
authors.initials: N
authors.lastname: Suzuki
authors.forename: Masahiro
authors.initials: M
authors.lastname: Haruki
authors.forename: Norio
authors.initials: N
authors.lastname: Nishi
authors.forename: Shinya
authors.initials: S
authors.lastname: Oishi
authors.forename: Nobutaka
authors.initials: N
authors.lastname: Fujii
authors.forename: Atsushi
authors.initials: A
authors.lastname: Utani
authors.forename: Hynda K
authors.initials: HK
authors.lastname: Kleinman
authors.forename: Motoyoshi
authors.initials: M
authors.lastname: Nomizu
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015815:Cell Adhesion Molecules / Q000037:antagonists & inhibitors / Q000502:physiology; D002460:Cell Line; D045744:Cell Line, Tumor; D020832:EF Hand Motifs; D005354:Fibrosarcoma / Q000378:metabolism / Q000473:pathology; D019812:Heparan Sulfate Proteoglycans / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D006493:Heparin / Q000378:metabolism / Q000494:pharmacology; D006801:Humans; D007797:Laminin / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology; D008562:Membrane Glycoproteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D051379:Mice; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism / Q000502:physiology; D010456:Peptides, Cyclic / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology; D011485:Protein Binding; D020033:Protein Isoforms / Q000737:chemistry / Q000378:metabolism / Q000502:physiology; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011509:Proteoglycans / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D053669:Syndecan-2
chemical_list: D015815:Cell Adhesion Molecules; D019812:Heparan Sulfate Proteoglycans; C501369:LAMA4 protein, human; C501370:Lama4 protein, mouse; D007797:Laminin; D008562:Membrane Glycoproteins; D010446:Peptide Fragments; D010456:Peptides, Cyclic; D020033:Protein Isoforms; D011509:Proteoglycans; D011994:Recombinant Proteins; C508245:SDC2 protein, human; C508246:Sdc2 protein, mouse; D053669:Syndecan-2; D006493:Heparin