FAK-Related Nonkinase Is a Multifunctional Negative Regulator of Pulmonary Fibrosis

Abstract

Idiopathic pulmonary fibrosis (IPF) is a progressive fibrotic lung disease whose underlying molecular mechanisms are largely unknown. Herein, we show that focal adhesion kinase-related nonkinase (FRNK) plays a key role in limiting the development of lung fibrosis. Loss of FRNK function in vivo leads to increased lung fibrosis in an experimental mouse model. The increase in lung fibrosis is confirmed at the histological, biochemical, and physiological levels. Concordantly, loss of FRNK function results in increased fibroblast migration and myofibroblast differentiation and activation of signaling proteins that drive these phenotypes. FRNK-deficient murine lung fibroblasts also have an increased capacity to produce and contract matrix proteins. Restoration of FRNK expression in vivo and in vitro reverses these profibrotic phenotypes. These data demonstrate the multiple antifibrotic actions of FRNK. More important, FRNK expression is down-regulated in human IPF, and down-regulation of FRNK in normal human lung fibroblasts recapitulates the profibrotic phenotype seen in FRNK-deficient cells. The effect of loss and gain of FRNK in the experimental model, when taken together with its down-regulation in human IPF, suggests that FRNK acts as an endogenous negative regulator of lung fibrosis by repressing multiple profibrotic responses.

3D pulmospheres serve as a personalized and predictive multicellular model for assessment of antifibrotic drugs

“…There is emerging recognition of the heterogeneity of IPF pathogenesis, including cell-autonomous behavior and chemoinvasive mediators in the local microenvironment (6). This suggests that each individual patient with IPF has numerous factors that contribute to the phenotype of invasive myofibroblasts (30). The variability in the invasiveness of pulmospheres from control patients and IPF is clearly demonstrated in Figure 3F.…”

Role of α1 and α2 chains of type IV collagen in early fibrotic lesions of idiopathic interstitial pneumonias and migration of lung fibroblasts

“…Therefore, our findings showing high levels of FAK phosphorylation in fibroblasts of OP are consistent with the idea that FAK has a key role in development of lung fibrosis. To our knowledge, three studies (two immunohistochemical 46,47 and one western blotting 48 studies) suggested that phosphorylated FAK levels were high in lung fibroblasts from IPF/UIP patients. However, in the three studies, the results were analyzed by comparison with normal human lung tissues or cultured lung fibroblasts from healthy subjects as normal controls, but not with intraluminal buds of OP as we examined in the present study.…”

TRPV4 mediates myofibroblast differentiation and pulmonary fibrosis in mice

“…Anesthetized, tracheostomized, paralyzed, and mechanically ventilated mice were used during all static P-V loop measurements (as a measure of lung compliance). Collagen deposition was quantified biochemically by measuring hydroxyproline levels or detecting collagen-1 in the lung tissue extracts by immunoblotting analysis (58). Fibrosis development was assessed by quantitation of α-SMA expression in the lung tissue extracts by immunoblotting analysis.…”

“…Fibrosis development was assessed by quantitation of α-SMA expression in the lung tissue extracts by immunoblotting analysis. Lung lavage was performed to determine total wbc counts or cell differentials as described previously (58). All animal protocols were performed according to guidelines approved by the Cleveland Clinic Institutional Review Board.…”