Cross talk between the Crumbs complex and Hippo signaling in renal epithelial cells

Cell polarity has a crucial role in organizing cells into tissues and in mediating transport processes and cell-cell communication. Especially the cells of the nephron require apicobasal polarity to establish and maintain their barrier function. The Crumbs complex including the integral membrane protein Crumbs, as well as Pals1 and Patj, is essential for the establishment of apicobasal polarity. The interactions of the core proteins and the interplay with other processes have been characterized in various epithelial cell lines in detail. Notably, Crb2 and Crb3 are expressed within the kidney and play an important role in the proper function of podocytes and tubules, respectively. The interaction of polarity proteins and components of the Hippo pathway-an evolutionarily highly conserved kinase cascade regulating cell proliferation, organ size, and tissue regeneration-has been discovered recently. Here, we discuss potential molecular and physiological links between the Crumbs complex and the Hippo pathway in renal cells.