Kindlin-2 Mediates Mechanical Activation of Cardiac Myofibroblasts.

Elena Godbout,Stellar Boo,Andras Kapus,Boris Hinz,Stephanie Hume,Dong Ok Son,Bernhard Wehrle-Haller,Leena Bruckner-Tuderman,Cristina Has,Sophie Clément,Vincent Sarrazy

doi:10.3390/cells9122702

Abstract

We identify the focal adhesion protein kindlin-2 as player in a novel mechanotransduction pathway that controls profibrotic cardiac fibroblast to myofibroblast activation. Kindlin-2 is co-upregulated with the myofibroblast marker α-smooth muscle actin (α-SMA) in fibrotic rat hearts and in human cardiac fibroblasts exposed to fibrosis-stiff culture substrates and pro-fibrotic TGF-β1. Stressing fibroblasts using ferromagnetic microbeads, stretchable silicone membranes, and cell contraction agonists all result in kindlin-2 translocation to the nucleus. Overexpression of full-length kindlin-2 but not of kindlin-2 missing a putative nuclear localization sequence (∆NLS kindlin-2) results in increased α-SMA promoter activity. Downregulating kindlin-2 with siRNA leads to decreased myofibroblast contraction and reduced α-SMA expression, which is dependent on CC(A/T)-rich GG(CArG) box elements in the α-SMA promoter. Lost myofibroblast features under kindlin-2 knockdown are rescued with wild-type but not ∆NLS kindlin-2, indicating that myofibroblast control by kindlin-2 requires its nuclear translocation. Because kindlin-2 can act as a mechanotransducer regulating the transcription of α-SMA, it is a potential target to interfere with myofibroblast activation in tissue fibrosis.

Highlights

The ability of cardiac fibroblasts to sense and control the mechanical properties of the extracellular matrix (ECM) is essential to adapt heart tissue to mechanical load and to repair injuries [1,2]
Because kindlin-2 controls the affinity of fibroblast integrins and mediates intracellular binding of the integrin cytoplasmic tail to contractile stress fibers, we investigated its role in human cardiac fibroblasts (hCF) mechanosensing and myofibroblast activation in conditions of cardiac fibrosis
From our observation that kindlin-2 expression is upregulated in myofibroblasts upon mechanical overload and fibrosis of the heart, we hypothesized that kindlin-2 regulates the activation of cardiac myofibroblasts

Summary

Introduction

The ability of cardiac fibroblasts to sense and control the mechanical properties of the extracellular matrix (ECM) is essential to adapt heart tissue to mechanical load (e.g., hypertension) and to repair injuries (e.g., after myocardial infarct) [1,2]. Aberrant mechanosensing results in activation of cardiac fibroblasts into α-smooth muscle actin (α-SMA)-expressing myofibroblasts that are characterized by excessive collagen secretion and contraction [3,4,5,6]. The outcome of myofibroblast dysfunction is fibrosis—accumulation of stiff collagen scar tissue. Within FAs, kindlins directly bind the cytoplasmic tails of β1 and β3 integrins and, together with talin, co-activate integrins to regulate cell–ECM adhesion and actin dynamics [15,16,17,18,19,20,21,22,23,24,25]

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Results

Conclusion