Basement membranes (BMs) are cell-adhesive scaffolds and agonists that are required for tissue growth, differentiation and adult functions. Elucidation of the mechanisms of BM assembly. Structure and functions is critical to understand the pathogenesis of diseases of kidney, nerve and other organs, to develop structure-correcting therapies, and to engineer biomaterials with BM properties for tissue repair. Our analysis of the role of BMs in different cell and organ culture systems has revealed that laminins adhere to cells through sulfated glycolipids, initiating BM assembly by polymerizing and binding to nidogen, type IV collagen, and proteoglycans. The assembling scaffold binds to, recruits, and activates integrins and receptor kinases through tethered growth factors, and recruits and anchors to dystroglycan, serving as a function-integrating signaling platform. The current proposal is to determine how a coordination of BM domains acts to drive complex cell and tissue functions. It seeks to determine if cell polarization depends upon laminin- initiated organization of the basal cell surfaces, if b1-integrin activity depends on a coding or summation of ligand binding, if integrins act in concert with growth factors to drive differentiation, which integrin-ligand interactions are critical, and if receptor mediated signaling is modulated by the inherent structur of the BM as well as ligand density and composition. These questions will be studied in Schwann cells and renal collecting duct epithelial models whose functions are initiated by BM-assembly mediated by a library of engineered laminins and other components. The proposal also seeks to characterize key sequences involved in laminin self-assembly, a key process of BM-assembly previously discovered by the P.I. Innovation lies in the treatment of BMs as integrated signaling platforms rather than as a simple collection of ligands, in the refinement of structure-function model that allows systematic testing of hypotheses, and in the approach of dissecting integrated functions at a molecular level by inducing BM assembly and functions with engineered proteins in both simple cell and complex tissues models.
Aim I. Mechanisms of BM induction of Schwann cell polarization and myelination: We will determine the contributions of the different laminin isoforms that depend on their unique domain activities, distinguish integrin from growth-factor contributions, and determine the differential role of ligands, and BM scaffold structure.
Aim II. Laminin induction of renal epithelial BM, polarity and functions. The role of BM in inducing cell polarity will be examined in mouse renal ureteric bud and collecting duct cells grown in collagen gel cultures.
Aim III. Functions of laminin LN and LE domains. Laminin polymerization requires formation of Lm?LN, Lm?LN and Lm?LN complexes. Lm?LN also adheres to cell surfaces. We will explore interacting sequences in LN and LE domains, dissect to role of cell adhesion, and evaluate Pierson syndrome laminin ?2LN domain mutations.
Basement membranes are cell-adhesive scaffolds and agonists that are required for tissue growth, differentiation and adult functions. Elucidation of te underlying mechanisms of assembly, structure and functions is critical to understand the pathogenesis of basement membrane-dependent diseases of kidney, nerve, muscle, brain and other organs, to develop structure-based therapies, and to engineer biomaterials with basement membrane properties for tissue regeneration and repair.
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