The function of integrin-linked kinase in normal and activated stellate cells: implications for fibrogenesis in wound healing

Abstract

Integrin-linked kinase (ILK) is a multidomain focal adhesion protein implicated in signal transduction between integrins and growth factor/extracellular receptors. We have previously shown that ILK expression is increased in liver fibrosis and that ILK appears to be a key regulator of fibrogenesis in rat hepatic stellate cells, effectors of the fibrogenic response. Here we hypothesized that the mechanism by which ILK mediates the fibrogenic phenotype is by engaging the small GTPase, Rho in a signal transduction pathway linked to fibrogenesis.MethodsILK function in quiescent (non fibrogenic) and activated (fibrogenic) stellate cells was examined in cells isolated from rat livers. ILK, Rho, and Gα12/13 signaling were manipulated using established chemical agents or specific adenoviral constructs.ResultsILK activity was minimal in quiescent stellate cells, but prominent in activated stellate cells; inhibition of ILK activity had no effect in quiescent cells, but had prominent effects in activated cells. Overexpression of ILK in activated stellate cells increased Rho activity, but had no effect in quiescent cells. Further, endothelin-1 (ET-1) stimulated Rho activity in activated stellate cells, but not in quiescent cells. Rho, RhoGEF and Gα12/13 expression were increased after stellate cell activation. Inhibition of Gα12/13 signaling, by expression of the RGS domain of the p115-Rho- specific guanine nucleotide exchange factor (p115-RGS) in activated stellate cells, significantly inhibited type I collagen and smooth muscle α actin expression, both classically upregulated after stellate cell activation. The data suggest that ILK mediates Rho dependent functional effects in activated stellate cells, and raise the possibility that ILK is important in cross talk with the GPCR system.

Integrin-linked kinase affects signaling pathways and migration in thyroid cancer cells and is a potential therapeutic target

“…24 ILK also has been shown to play an integral role in integrating cytokine cell signaling in both dermal fibroblasts 25 and hepatic stellate cells. 26 Thus, inhibition of ILK pharmacologically has the potential to alter not only the tumor, but the dysregulated stroma as well, adding additional novelty and potential therapeutic efficacy to this drug target.…”

Targeting Mechanotransduction at the Transcriptional Level: YAP and BRD4 Are Novel Therapeutic Targets for the Reversal of Liver Fibrosis

“…Indeed, several integrin-associated signaling proteins, including integrin-linked kinase (ILK, Zhang et al, 2006; Li et al, 2009; Kavvadas et al, 2010; Shafiei and Rockey, 2012; Radovanac et al, 2013), focal adhesion kinase (FAK, Wong et al, 2011; Lagares et al, 2012; Kinoshita et al, 2013; Lagares and Kapoor, 2013; Zhao et al, 2016), and regulators and effectors of Rho GTPases, such as P-Rex1 (Liang et al, 2016), PAK and Rho-activated kinase (ROCK, Knipe et al, 2015; Martin et al, 2016) have been identified as potential targets for anti-fibrotic therapy in a number of organs. Notably, activation of ILK, which links F-actin to focal adhesions and is required for integrin-mediated force generation, sustains nuclear YAP accumulation in pulmonary arterial vascular smooth muscle cells to promote cell proliferation in pulmonary arterial hypertension, a disease characterized by increased deposition of extracellular matrix and vascular stiffness (Kudryashova et al, 2016).…”

Translating an Understanding of the Pathogenesis of Hepatic Fibrosis to Novel Therapies

“…It has also been shown that integrins, which link the extracellular matrix to stellate (and other cells) play an important role in transmitting fibrogenic and contractile signals 55 . Recently, integrin linked kinase (ILK), an integrin-intracellular signaling molecule, has been shown to transmit fibrogenic signals in stellate cells 56, 57 .…”