Cooperative signaling by TGF-ß1 and WNT-11 drives sm-α-actin expression in smooth muscle via Rho kinase-actin-MRTF-A signaling.

Airway smooth muscle (ASM) remodeling is a key feature in asthma and includes changes in smooth muscle-specific gene and protein expression. Despite this being a major contributor to asthma pathobiology, our understanding of the mechanisms governing ASM remodeling remains poor. Here, we studied the functional interaction between WNT-11 and TGF-ß1 in ASM cells. We demonstrate that WNT-11 is preferentially expressed in contractile myocytes and is strongly upregulated following TGF-ß1-induced myocyte maturation. Knock-down of WNT-11 attenuated TGF-ß1-induced smooth muscle (sm)-α-actin expression in ASM cells. We demonstrate that TGF-ß1-induced sm-α-actin expression is mediated by WNT-11 via RhoA activation and subsequent actin cytoskeletal remodeling, as pharmacological inhibition of either Rho kinase by Y27632 or actin remodeling by latrunculin A attenuated sm-α-actin induction. Moreover, we show that TGF-ß1 regulates the nuclear expression of myocardin-related transcription factor-A (MRTF-A) in a Rho kinase-dependent fashion, which in turn mediates sm-α-actin expression. Finally, we demonstrate that TGF-ß1-induced MRTF-A nuclear translocation is dependent on endogenous WNT-11. The present study thus demonstrates a WNT-11-dependent Rho kinase-actin-MRTF-A signaling axis that regulates the expression of sm-α-actin in ASM cells.

Noncanonical WNT-5A signaling regulates TGF-ß-induced extracellular matrix production by airway smooth muscle cells.

Transforming growth factor ß (TGF-ß), a key mediator of fibrotic responses, is increased in asthma and drives airway remodeling by inducing expression of extracellular matrix (ECM) proteins. We investigated the molecular mechanisms underlying TGF-ß-induced ECM expression by airway smooth muscle cells and demonstrate a novel link between TGF-ß and Wingless/integrase 1 (WNT) signaling in ECM deposition. Airway smooth muscle expresses abundant WNT ligands, with the noncanonical WNT-5A being the most profoundly expressed. Interestingly, WNT-5A shows ∼2-fold higher abundance in airway smooth muscle cells isolated from individuals with asthma than individuals without asthma. WNT-5A is markedly induced in response to TGF-ß (4-16-fold; EC50 0.3 ng/ml) and is required for collagen and fibronectin expression by airway smooth muscle. WNT-5A engages noncanonical WNT signaling pathways, as inhibition of Ca(2+) and c-Jun N-terminal kinase (JNK) signaling attenuated this TGF-ß response, whereas the canonical WNT antagonist Dickkopf 1 (DKK-1) did not. Accordingly, WNT-5A induced JNK phosphorylation and nuclear translocation of nuclear factor of activated T cells c1 (NFATc1). Furthermore, silencing of the WNT-5A receptors Frizzled 8 (FZD8) and RYK attenuated TGF-ß-induced ECM expression. Collectively, these findings demonstrate that noncanonical WNT-5A signaling is activated by and necessary for TGF-ß-induced ECM production by airway smooth muscle cells, which could have significance in asthma pathogenesis.