Integrins in the kidney - beyond the matrix.

The development and proper functioning of the kidney is dependent on the interaction of kidney cells with the surrounding extracellular matrix (ECM). These interactions are mediated by heterodimeric membrane-bound receptors called integrins, which bind to the ECM via their extracellular domain and via their cytoplasmic tail to intracellular adaptor proteins, to assemble large macromolecular adhesion complexes. These interactions enable integrins to control cellular functions such as intracellular signalling and organization of the actin cytoskeleton and are therefore crucial to organ function. The different nephron segments and the collecting duct system have unique morphologies, functions and ECM environments and are thus equipped with unique sets of integrins with distinct specificities for the ECM with which they interact. These cell-type-specific functions are facilitated by specific intracellular integrin binding proteins, which are critical in determining the integrin activation status, ligand-binding affinity and the type of ECM signals that are relayed to the intracellular structures. The spatiotemporal expression of integrins and their specific interactions with binding partners underlie the proper development, function and repair processes of the kidney. This Review summarizes our current understanding of how integrins, their binding partners and the actin cytoskeleton regulate kidney development, physiology and pathology.