Fluid shear stress-induced TGF-β/ALK5 signaling in renal epithelial cells is modulated by MEK1/2

Fluid shear stress-induced TGF-β/ALK5 signaling in renal epithelial cells is modulated by MEK1/2

Kunnen, S.J. (Leiden University Medical Center)
Leonhard, W.N. (Leiden University Medical Center)
Semeins, C. (Universiteit van Amsterdam; Vrije Universiteit Amsterdam)
Hawinkels, L.J.A.C. (Leiden University Medical Center)
Poelma, C. (TU Delft Multi Phase Systems)
ten Dijke, P. (Leiden University Medical Center)
Bakker, A. (Universiteit van Amsterdam; Vrije Universiteit Amsterdam)
Hierck, B.P. (Leiden University Medical Center)
Peters, D.J.M. (Leiden University Medical Center)

2017

Renal tubular epithelial cells are exposed to mechanical forces due to fluid flow shear stress within the lumen of the nephron. These cells respond by activation of mechano-sensors located at the plasma membrane or the primary cilium, having crucial roles in maintenance of cellular homeostasis and signaling. In this paper, we applied fluid shear stress to study TGF-β signaling in renal epithelial cells with and without expression of the Pkd1-gene, encoding a mechano-sensor mutated in polycystic kidney disease. TGF-β signaling modulates cell proliferation, differentiation, apoptosis, and fibrotic deposition, cellular programs that are altered in renal cystic epithelia. SMAD2/3-mediated signaling was activated by fluid flow, both in wild-type and Pkd1−/− cells. This was characterized by phosphorylation and nuclear accumulation of p-SMAD2/3, as well as altered expression of downstream target genes and epithelial-to-mesenchymal transition markers. This response was still present after cilia ablation. An inhibitor of upstream type-I-receptors, ALK4/ALK5/ALK7, as well as TGF-β-neutralizing antibodies effectively blocked SMAD2/3 activity. In contrast, an activin-ligand trap was ineffective, indicating that increased autocrine TGF-β signaling is involved. To study potential involvement of MAPK/ERK signaling, cells were treated with a MEK1/2 inhibitor. Surprisingly, fluid flow-induced expression of most SMAD2/3 targets was further enhanced upon MEK inhibition. We conclude that fluid shear stress induces autocrine TGF-β/ALK5-induced target gene expression in renal epithelial cells, which is partially restrained by MEK1/2-mediated signaling.

Fluid flow
Mechanotransduction
Cilia
SMAD2/3 signaling
ERK1/2
Pkd1−/−

http://resolver.tudelft.nl/uuid:468c805e-3183-4740-b353-5e687d792497

https://doi.org/10.1007/s00018-017-2460-x

1420-682X

Cellular and Molecular Life Sciences, 74 (12), 2283 -2298

Institutional Repository

journal article

© 2017 S.J. Kunnen, W.N. Leonhard, C. Semeins, L.J.A.C. Hawinkels, C. Poelma, P. ten Dijke, A. Bakker, B.P. Hierck, D.J.M. Peters