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ROLE FOR ILK IN THE CONTROL OF MATRIX/ACTIN CYTOSKELETON ORGANIZATION IN HUMAN INTESTINAL EPITHELIAL CELLS
D Gagné, PH Vachon, JF Beaulieu
Équipe IRSC sur l’épithélium digestif Département d’anatomie et de biologie cellulaire, Université de Sherbrooke, Sherbrooke, Québec
INTRODUCTION: Interactions between cells and their surrounding matrix control many different functions of the cell. Integrin linked kinase (ILK) is a serine-threonine kinase which also plays a role as a scaffold protein in the focal adhesion point. ILK has been found to be involved in the process of integrin signaling in many different tissues and its de-regulation leads to different pathologies including cancer. However, the role of ILK in normal intestinal cells has not yet been established.
OBJECTIVE: The objective of this study was to characterize the involvement of ILK in the cellular functions of human intestinal epithelial cells.
RESULTS: Immunolocalization studies performed on cryosections showed that ILK is expressed at the base of the epithelial cells of the intestinal crypt-villus axis. Analysis of the expression of ILK in the HIEC and Caco-2/15 cell models revealed a strong expression of the ILK transcript and protein in proliferating cells. The forced decrease of ILK expression in the HIEC cell line using a synthetic siRNA led to a marked change in cell morphology and actin cytoskeleton organization, associated with an inhibition of fibronectin deposition as well as a decrease in the rates of cell spreading and migration. The inhibition of fibronectin deposition is caused at least in part by a decrease of fibronectin expression as observed by western blot and real-time PCR. The defect observed in HIEC cells following the inhibition of ILK can be partially rescued by an exogenous fibronectin matrix.
CONCLUSION: Our results show that ILK is implicated in fibronectin deposition by human intestinal epithelial cells, suggesting a role for ILK in the proliferation/migration process along the crypt-villus axis.