Regulation of cell–matrix contacts and β-catenin signaling in VSMC by integrin-linked kinase: implications for intimal thickening

Abstract

Vascular smooth muscle cell (VSMC) proliferation and migration is responsible for intimal thickening that occurs in restenosis and atherosclerosis. Integrin-linked kinase (ILK) is a serine/ threonine protein kinase implicated in signaling pathways involved in cell proliferation and migration. We studied the involvement of ILK in intimal thickening. ILK expression was significantly increased in two models of intimal thickening: balloon-injured rat carotid arteries and human saphenous vein organ cultures. Over-expression of a dominant negative ILK (DN-ILK) significantly reduced intimal thickening by approximately 50% in human saphenous vein organ cultures, demonstrating an important role in intimal thickening. ILK protein and activity was reduced on laminin and up-regulated on fibronectin, indicating ILK protein expression is modulated by extracellular matrix composition. Inhibition of ILK by siRNA knockdown and DN-ILK significantly decreased VSMC proliferation and migration while wild type ILK significantly increased proliferation and migration on laminin, confirming an essential role of ILK in both processes. Localization of paxillin and vinculin and protein levels of FAK and phospho-FAK indicated that inhibition of ILK reduced focal adhesion formation. Additionally, inhibition of ILK significantly attenuated the presence of the cell-cell complex proteins N-cadherin and β-catenin, and β-catenin signaling. We therefore suggest ILK modulates VSMC proliferation and migration at least in part by acting as a molecular scaffold in focal adhesions as well as modulating the stability of cell-cell contact proteins and β-catenin signaling. In summary, ILK plays an important role in intimal thickening by modulating VSMC proliferation and migration via regulation of cellmatrix and cell-cell contacts and β-catenin signaling.

Inherent differences in morphology, proliferation, and migration in saphenous vein smooth muscle cells cultured from nondiabetic and Type 2 diabetic patients

“…Vinculin expression is often inversely correlated with migratory capacity (37); however, in our study, cells derived from T2DM patients exhibited both an increase in vinculin-positive focal adhesions and an increase in migration relative to those from nondiabetic patients. Although surprising, this is not without precedent because a recent study also associated a decrease in vinculin-positive focal adhesions with a corresponding decrease in cellular migration (10). Importantly, those data were also derived using human SV-SMC (10).…”

“…Although surprising, this is not without precedent because a recent study also associated a decrease in vinculin-positive focal adhesions with a corresponding decrease in cellular migration (10). Importantly, those data were also derived using human SV-SMC (10). Exposure to insulin has previously been reported to cause an increase in the number of vinculin-positive focal adhesions in human aortic SMC (30), and here we demonstrated that insulin treatment increased focal adhesions in SV-SMC from both T2DM and nondiabetic patients.…”

CTGF disrupts alveolarization and induces pulmonary hypertension in neonatal mice: implication in the pathogenesis of severe bronchopulmonary dysplasia

“…Less is known about ILK/GSK-3␤ signaling in lung development and remodeling. Previous studies have demonstrated an important role of ILK in regulating survival of lung fibroblasts and stimulating proliferation and migration of vascular SMC (13,16,39). Recent studies have shown that inhibition of GSK-3␤ protects bleomycin-induced lung fibrosis (20).…”

Tripterine Treatment Improves Endothelial Progenitor Cell Function via Integrin-Linked Kinase

“…ILK, through the phosphorylation of its downstream effectors Akt and GSK-3β, is an important modulator of several signaling pathways including the canonical Wnt/β-catenin pathway, which regulates the expression of cell cycle genes including cyclin D1 [37,38]. ILK was previously shown to be involved in intimal thickening associated with atherosclerosis by modulating vascular smooth muscle cell proliferation and migration through the regulation of cell-matrix contacts and β-catenin signaling [39]. We showed that silencing of ILK inhibited Akt and GSK-3β phosphorylation and down regulated β-catenin and cyclin D1, and tripterine treatment restored ILK levels, suggesting a possible mechanism by which tripterine improves EPC function.…”