Biological activities of homologous loop regions in the laminin alpha chain G domains.
Laminin alpha chains (alpha1-alpha5 chains) have diverse chain-specific biological functions. The LG4 modules of laminin alpha chains consist of a 14-stranded beta-sheet (A-N) sandwich structure. Several biologically active sequences have been identified in the connecting loop regions. Here, we evaluated the biological activities of the loop regions of the E and F strands in the LG4 modules using five homologous peptides from each of the mouse alpha chains (EF-1: DYATLQLQEGRLHFMFDLG, alpha1 chain 2747-2765; EF-2: DFGTVQLRNGFPFFSYDLG, alpha2 chain 2808-2826; EF-3: RDSFVALYLSEGHVIFALG, alpha3 chain 2266-2284; EF-4: DFMTLFLAHGRLVFMFNVG, alpha4 chain 1511-1529; EF-5: SPSLVLFLNHGHFVAQTEGP, alpha5 chain 3304-3323). These homologous peptides showed chain-specific cell attachment and neurite outgrowth activities. Well organized actin stress fibers and focal contacts with vinculin accumulation were observed in fibroblasts attached on EF-1, whereas fibroblasts on EF-2 and EF-4 showed filopodia with ruffling. Fibroblast attachment to EF-2 and EF-4 was mediated by syndecan-2. In contrast, EF-1 promoted alpha2beta1 integrin-mediated fibroblast attachment and inhibited fibroblast attachment to a recombinant laminin alpha1 chain LG4-5. The receptors for EF-3 and EF-5 are unknown. Further, when the active core sequence of EF-1 was cyclized, utilizing two additional cysteine residues at both the N and C termini through a disulfide bridge, the cyclic peptide significantly enhanced integrin-mediated cell attachment. These results indicate that integrin-mediated cell attachment to the EF-1 sequence is conformation-dependent and that the loop structure is important for the activity. The homologous peptides, which promote either integrin- or syndecan-mediated cell attachment, may be useful for understanding the cell type- and chain-specific biological activities of the laminins.
Suzuki
Nobuharu
N
Graduate School of Environmental Earth Science, Hokkaido University, Sapporo 060-0810, Japan.
Nakatsuka
Hiroko
H
Mochizuki
Mayumi
M
Nishi
Norio
N
Kadoya
Yuichi
Y
Utani
Atsushi
A
Oishi
Shinya
S
Fujii
Nobutaka
N
Kleinman
Hynda K
HK
Nomizu
Motoyoshi
M
D000199:Actins / Q000096:biosynthesis / Q000737:chemistry; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002448:Cell Adhesion; D002460:Cell Line; D045744:Cell Line, Tumor; D003599:Cytoskeleton / Q000378:metabolism; D004220:Disulfides; D004305:Dose-Response Relationship, Drug; D004492:Edetic Acid / Q000494:pharmacology; D005347:Fibroblasts / Q000378:metabolism; D019812:Heparan Sulfate Proteoglycans / Q000096:biosynthesis; D006493:Heparin / Q000494:pharmacology; D006801:Humans; D007797:Laminin / Q000737:chemistry* / Q000502:physiology*; D008562:Membrane Glycoproteins / Q000096:biosynthesis / Q000737:chemistry; D051379:Mice; D008969:Molecular Sequence Data; D009474:Neurons / Q000378:metabolism; D016716:PC12 Cells; D010455:Peptides / Q000737:chemistry; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011509:Proteoglycans / Q000096:biosynthesis / Q000737:chemistry; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D053669:Syndecan-2; D053667:Syndecans; D016596:Vinculin / Q000096:biosynthesis
D000199:Actins; D004220:Disulfides; D019812:Heparan Sulfate Proteoglycans; C501369:LAMA4 protein, human; C501370:Lama4 protein, mouse; D007797:Laminin; D008562:Membrane Glycoproteins; D010455:Peptides; D011509:Proteoglycans; D011994:Recombinant Proteins; C508245:SDC2 protein, human; C508246:Sdc2 protein, mouse; C508247:Sdc2 protein, rat; D053667:Syndecans; C102645:laminin alpha 2; C097043:laminin alpha5; D016596:Vinculin; D053669:Syndecan-2; C084098:laminin A; C095567:laminin alpha 3; D006493:Heparin; D004492:Edetic Acid