A cell adhesive peptide from tropoelastin promotes sequential cell attachment and spreading via distinct receptors
Tropoelastin is the dominant monomer that assembles to form elastin, which confers elasticity to vertebrate elastic tissues including skin, arteries, and lungs. Tropoelastin interacts with cells through cell surface receptors including integrins and glycosaminoglycans (GAGs). As the region 17–18 is recognized as a key region in cell attachment and spreading, we utilized C-terminal truncated tropoelastin constructs containing dissected sections of domain 18. We mapped a cell-interactive sequence of tropoelastin to domain 17 and the first six amino acids (aa) of domain 18. Further delineation identified a 21-residue sequence (Peptide 302–322) which promoted cell attachment and spreading indistinguishable from that to N18, a construct encompassing the full domains 17–18. Alanine substitution of the lysines at positions 11 and 14 in Peptide 302–322 effectively abolished cell binding. This reliance on lysines pointed to a role for GAGs, which was assessed by heparan sulfate inhibition, leading to 85.9 ± 4.2% decreased cell binding, while inhibition of integrins using ethylenediaminetetraacetic acid did not affect attachment. In contrast, selective antibody blocking of the integrin αv family prevented cell spreading by 92.5 ± 8.9%. We propose a two-step mechanism by which cell interactions occur at this central region of tropoelastin: initially, cell adhesion is mediated by GAGs, which contact the lysine residues within the target sequence, and subsequently facilitate cell spreading modulated by integrins, specifically αvβ3 and αvβ5. We conclude that this region comprises a tropoelastin-derived, cell-interactive sequence that independently mediates potent cell binding and spreading via sequential recognition of GAG and integrin cell surface receptors.