title: Enhanced cell adhesion and mature intracellular structure promoted by squaramide-based RGD mimics on bioinert surfaces.
abstract: Highly selective molecular binding and the subsequent dynamic protein assemblies control the adhesion of mammalian cells. Molecules that inhibit cell adhesion have the therapeutic potential for a wide range of diseases. Here, we report an efficient synthesis (2-4 steps) of a class of squaramide molecules that mimics the natural tripeptide ligand Arg-Gly-Asp (RGD) that mediates mammalian cell adhesion through binding with membrane protein integrin. In solution, this class of squaramides exhibits a higher potency at inhibiting mammalian cell adhesion than RGD tripeptides. When immobilized on a bio-inert background formed by self-assembled monolayers of alkanethiols on gold films, squaramide ligands mediate vastly different intracellular structures than RGD ligands. Immunostaining revealed that the focal adhesions are smaller, but with a larger quantity, for cells adhered on squaramides than that on RGD ligands. Furthermore, the actin filaments are also more fibrous and well distributed for cell adhesion mediated by squaramide than that by RGD ligands. Quantification reveal that squaramide ligands mediate about 1.5 times more total focal adhesion (measured by the summation of the area of all focal adhesions) than that by natural RGD ligands. This result suggests that cell adhesion inhibitors, while blocking the attachment of cells to surfaces, may induce more focal adhesion proteins. Finally, this work demonstrates that immobilizing new ligands on bioinert surfaces provide a powerful tool to study mammalian cell adhesion.
authors.affiliation: Department of Chemistry, 111 College Place, 1-014, Syracuse University, Syracuse, NY 13244-4100, USA.
authors.forename: Sri Kamesh
authors.initials: SK
authors.lastname: Narasimhan
authors.affiliation: Department of Chemistry, 111 College Place, 1-014, Syracuse University, Syracuse, NY 13244-4100, USA.
authors.forename: Preeti
authors.initials: P
authors.lastname: Sejwal
authors.affiliation: Department of Chemistry, 111 College Place, 1-014, Syracuse University, Syracuse, NY 13244-4100, USA.
authors.forename: Shifa
authors.initials: S
authors.lastname: Zhu
authors.affiliation: Department of Chemistry, 111 College Place, 1-014, Syracuse University, Syracuse, NY 13244-4100, USA. Electronic address: yluk@syr.edu.
authors.forename: Yan-Yeung
authors.initials: YY
authors.lastname: Luk
mesh_terms: D000577:Amides / Q000737:chemistry / Q000494:pharmacology*; D000818:Animals; D040761:Biomimetic Materials / Q000737:chemistry / Q000494:pharmacology*; D002448:Cell Adhesion / Q000187:drug effects* / Q000502:physiology; D003503:Cyclobutanes / Q000737:chemistry / Q000494:pharmacology; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects; D022001:Focal Adhesions / Q000378:metabolism; D051379:Mice; D015394:Molecular Structure; D009842:Oligopeptides / Q000737:chemistry / Q000494:pharmacology*; D013237:Stereoisomerism; D041701:Swiss 3T3 Cells
chemical_list: D000577:Amides; D003503:Cyclobutanes; D009842:Oligopeptides; C047981:arginyl-glycyl-aspartic acid; C030042:squaric acid