Regulation of TGF-β1-Driven Differentiation of Human Lung Fibroblasts: Emerging Roles of Cathepsin B and Cystatin C

Mariana Kasabova, Alix Joulin-Giet, Fabian Lecaille, Brendan F. Gilmore, Sylvian Marchan-Adam, Ahlame Saidi, Gilles Lalmanach

Research output: Contribution to journalArticlepeer-review

47 Citations (Scopus)


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 (IPF) 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 addition of Cat B generated 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. While mRNA expression of cystatin C was stable, its secretion, which was inhibited by brefeldin A, increased during TGF-β1-induced differentiation of IPF and CCD-19Lu fibroblasts. In addition cystatin C participated in the control of extracellular Cats, since 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.
Original languageEnglish
Pages (from-to)16239-16251
Number of pages13
JournalThe Journal of biological chemistry
Issue number23
Early online date30 Apr 2014
Publication statusPublished - Jun 2014


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