Integrin-linked kinase (ILK) has been implicated in the pathogenesis of
proteinuria and congenital
nephrotic syndrome. However, the function of ILK in glomerular podocyte in a physiologic setting remains unknown. In this study, a mouse model was generated in which ILK gene was selectively disrupted in podocytes by using the Cre-LoxP system. Podocyte-specific ablation of ILK resulted in heavy
albuminuria, glomerulosclerosis, and
kidney failure, which led to animal death beginning
at 10 wk of age. Podocyte detachment and apoptosis were not observed at 4 wk of age, when
albuminuria became prominent, indicating that they are not the initial cause of
proteinuria. Electron microscopy revealed an early foot process effacement, as well as morphologic abnormality, in ILK-deficient podocytes. ILK deficiency caused an aberrant distribution of
nephrin and alpha-actinin-4 in podocytes, whereas the localization of
podocin and synaptopodin remained relatively intact. Co-immunoprecipitation demonstrated that ILK physically interacted with
nephrin to form a ternary complex, and alpha-actinin-4 participated in ILK/
nephrin complex formation. Therefore, ILK plays an essential role in specifying
nephrin and alpha-actinin-4 distribution and in maintaining the slit diaphragm integrity and podocyte architecture. These results also illustrate that the
integrin and slit diaphragm signals in podocytes are intrinsically coupled through an ILK-dependent mechanism.