Regulation of TGF-β1-driven differentiation of human lung fibroblasts: emerging roles of cathepsin B and cystatin C.

Abstract

Lung matrix homeostasis partly depends on the fine regulation of proteolytic activities. We examined the expression of human cysteine cathepsins (Cats) and their relative contribution to TGF-β1-induced fibroblast differentiation into myofibroblasts. Assays were conducted using both primary fibroblasts obtained from patients with idiopathic pulmonary fibrosis and human lung CCD-19Lu fibroblasts. Pharmacological inhibition and genetic silencing of Cat B diminished α-smooth muscle actin expression, delayed fibroblast differentiation, and led to an accumulation of intracellular 50-kDa TGF-β1. Moreover, the addition of Cat B generated a 25-kDa mature form of TGF-β1 in Cat B siRNA-pretreated lysates. Inhibition of Cat B decreased Smad 2/3 phosphorylation but had no effect on p38 MAPK and JNK phosphorylation, indicating that Cat B mostly disturbs TGF-β1-driven canonical Smad signaling pathway. Although mRNA expression of cystatin C was stable, its secretion, which was inhibited by brefeldin A, increased during TGF-β1-induced differentiation of idiopathic pulmonary fibrosis and CCD-19Lu fibroblasts. In addition, cystatin C participated in the control of extracellular Cats, because its gene silencing restored their proteolytic activities. These data support the notion that Cat B participates in lung myofibrogenesis as suggested for stellate cells during liver fibrosis. Moreover, we propose that TGF-β1 promotes fibrosis by driving the effective cystatin C-dependent inhibition of extracellular matrix-degrading Cats.

• Authors: Mariana Kasabova, Alix Joulin-Giet, Fabien Lecaille, Brendan F Gilmore, Sylvain Marchand-Adam, Ahlame Saidi, Gilles Lalmanach
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 289 Issue 23 Pg. 16239-51 (Jun 06 2014) ISSN: 1083-351X [Electronic] United States
• PMID: 24790080 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.

Chemical References

• Cystatin C
• RNA, Small Interfering
• Smad Proteins
• Transforming Growth Factor beta1
• Cathepsin B

Topics

• Blotting, Western
• Cathepsin B (genetics, physiology)
• Cell Differentiation (physiology)
• Cells, Cultured
• Cystatin C (physiology)
• Fibroblasts (cytology)
• Gene Silencing
• Humans
• Lung (cytology)
• Phosphorylation
• RNA Interference
• RNA, Small Interfering
• Real-Time Polymerase Chain Reaction
• Signal Transduction
• Smad Proteins (metabolism)
• Transforming Growth Factor beta1 (physiology)