Laminin-5 is the extracellular matrix (ECM) protein that mediates epithelial adhesion to the underlying basement membrane (BM). Laminin-5 mediates this cell-ECM attachment through its ability to simultaneously bind to multiple cell-surface and ECM ligands. The strong adhesive properties of laminin-5 are responsible for providing the skin with its integrity and ability to withstand traumatic forces. The importance of laminin-5's function is best exemplified through observations of patients who possess a genetic deficiency of this protein. These patients suffer from a disorder known as Junctional Epidermolysis Bullosa (JEB), characterized by extensive blister formation on all epidermal and mucosal surfaces. Identification and sequencing of the major ell- and ECM-binding domains of laminin-5 has major therapeutic potentials for developing gene therapy for JEB patients, in addition to stabilizing skin grafts for the treatment of burn patients, and improving graft survival in corneal and pancreatic islet cell transplants. The specific ligand-binding sequences, however, have not been identified to date. Multiple approaches designed at locating and sequencing these critical binding domains are proposed. First, a series of overlapping peptide fragments will be screened in sold-phase binding assays for their ability to bind to cell and ECM ligands. Secondly, peptides with sequential C-terminal truncations of the alpha3 chain of laminin-5 will be assayed for their ability to bind to integrins. Progressive elimination of C-terminal residues will perturb ligand-binding and thus identify and thus identify key sequences. Thirdly, site-directed mutagenesis of suspected ligand- binding domains will be used to confirm the location of these binding sequences.
