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Extracellular matrix (ECM) is fundamental for the survival of cells within a tissue. Loss of contact with the surrounding ECM often causes altered cell differentiation or cell death. Hepatocytes cultured without matrix lose patterns of hepatocyte-specific gene expression and characteristic cellular micro-architecture. However, differentiation is restored after the addition of hydrated matrix preparations to dedifferentiated hepatocytes. Integrin-linked kinase (ILK) is an important component of cell–ECM adhesions transmitting integrin signaling to the interior of the cell. ILK has been implicated in many fundamental cellular processes such as differentiation, proliferation, and survival. In this study, we investigated the role of ILK in mouse hepatocytes in vitro as well as in vivo. Depletion of ILK from primary mouse hepatocytes resulted in enhanced apoptosis. This was accompanied by increased caspase 3 activity and a significant decrease in expression of PINCH and α-parvin, which, along with ILK, form a stable well-characterized ternary complex at cell–ECM adhesions. The induction of apoptosis caused by ILK depletion could be substantially reversed by simultaneous overexpression of ILK, indicating that apoptosis is indeed a consequence of ILK removal. These results were further corroborated via in vivo data showing that adenoviral delivery of Cre-recombinase in ILK-floxed animals by tail vein injection resulted in acute hepatitis, with a variety of pathological findings including inflammation, fatty change, and apoptosis, abnormal mitoses, hydropic degeneration, and necrosis. Conclusion: Our results demonstrate the importance of ILK and integrin signaling for the survival of hepatocytes and the maintenance of normal liver function. (HEPATOLOGY 2007.)

Alterations in the cellular architecture, adhesion, and/or loss of glomerular podocytes are causal factors in the development of proteinuria and the progression to end-stage renal failure. With the use of an inducible podocyte differentiation system, it was found that the cellular levels of PINCH-1, integrin linked kinase (ILK), and alpha-parvin, cytoplasmic components of cell-extracellular matrix adhesions, were significantly increased during podocyte differentiation. Concomitantly, an increased amount of the PINCH-1-ILK-alpha-parvin complex was detected in the differentiated, foot process-containing podocytes. Overexpression of the PINCH-1-binding ankyrin repeat domain of ILK but not that of a PINCH-1-binding defective mutant form of the ankyrin domain effectively inhibited the formation of the PINCH-1-ILK-alpha-parvin complex. Disruption of the PINCH-1-ILK-alpha-parvin complex significantly reduced the podocyte-matrix adhesion and foot process formation. Furthermore, a marked increase of apoptosis in the podocytes in which the assembly of the PINCH-1-ILK-alpha-parvin complex was compromised was detected. Inhibition of ILK with a small compound inhibitor also altered podocyte cytoskeleton and increased apoptosis. Finally, it is shown that alpha-parvin is phosphorylated in podocytes. Mutations at the alpha-parvin N-terminal proline-directed serine phosphorylation sites reduced its complex formation with ILK and resulted in defects in podocyte adhesion, architecture, and survival. These results provide important evidence for a crucial role of the PINCH-1-ILK-alpha-parvin complex in the control of podocyte adhesion, morphology, and survival.