Functional ligand of integrin alpha-8/beta-1 in kidney development. Regulates the expression of GDNF with integrin alpha-8/beta-1 which is essential for kidney development. May also play a role in the development and function of various tissues, regulating cell adhesion, spreading and survival through the binding of several integrins (By similarity). Homodimer and homotrimer. Trapped on the cell surface or in the extracellular matrix. The MAM domain is required for localization at the cell surface. Belongs to the nephronectin family.