Bifunctional Peptides Derived from Homologous Loop Regions in the Laminin α Chain LG4 Modules Interact with both α2β1 Integrin and Syndecan-2

Abstract

Laminin alpha chains show diverse biological functions in a chain-specific fashion. The laminin G-like modules (LG modules) of the laminin alpha chains consist of a 14-stranded beta-sheet sandwich structure with biologically active sequences found in the connecting loops. Previously, we reported that connecting loop regions between beta-strands E and F in the mouse laminin alpha chain LG4 modules exhibited chain-specific activities. In this study, we focus on the homologous loop regions in human laminin alpha chain LG4 modules using five synthetic peptides (hEF-1-hEF-5). These homologous peptides induced chain-specific cellular responses in various cell types. Next, to examine the dual-receptor recognition model, we synthesized chimeras (cEF13A-cEF13E) derived from peptides hEF-1 and hEF-3. All of the chimeric peptides promoted fibroblast attachment as well as the parental peptides. Attachment of fibroblasts to cEF13A and cEF13B was inhibited by anti-integrin alpha2 and beta1 antibodies and by heparin, while cell adhesion to cEF13C, cEF13D, and cEF13E was blocked only by heparin. Actin organization of fibroblasts on cEF13C was not different from that on hEF-3, but cEF13B induced membrane ruffling at the tips of the actin stress fibers. These results suggest that cEF13B had bifunctional effects on cellular behaviors through alpha2beta1 integrin and heparin/heparan sulfate proteoglycan. We conclude that the approach utilizing chimeric peptides is useful for examining cellular mechanisms in dual-receptor systems.

Syndecans as receptors and organizers of the extracellular matrix

“…Dystroglycan interacts with the LG4 regions of the α1, α2 and α5 chains ) and the binding sites for heparin and dystroglycan overlap in the α1LG4 module (Andac et al 1999). Further complexity has been shown by Yokoyama et al (2005). Fibroblasts spread well on the α1LG4 module but poorly on the homologous modules of α2, α3 and α4 chains.…”

The β3 chain short arm of laminin‐332 (laminin‐5) induces matrix assembly and cell adhesion activity of laminin‐511 (laminin‐10)

“…It is known that some membrane proteins are associated with integrins and regulate integrin functions. These include syndecans [Beauvais and Rapraeger, 2004;Yokoyama et al, 2005], tetraspanins [Berditchevski and Odintsova, 1999;Nishiuchi et al, 2005], and galectins [Woo et al, 1990;Hughes, 2001]. We found that b3SA has weak heparin-binding activity (data not shown).…”

Antithetic roles of proteoglycans in cancer

“…In the case of syndecans, alternative promoting or inhibiting functions may depend upon their differential ability to serve as co-receptors with ligand specificities dictated by their GAG chain diversity [203,204]. This idea has its grounds in the fact that syndecan-1 has been reported to induce intracellular signal transduction independently of integrins [205] and that binding of a variety of tumor cell types to laminins requires a syndecan-1-substrate interaction [206][207][208][209]. A similar putative interaction Fig.…”