Research ArticlePulmonary Arterial Hypertension

NEDD9 targets COL3A1 to promote endothelial fibrosis and pulmonary arterial hypertension

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Science Translational Medicine  13 Jun 2018:
Vol. 10, Issue 445, eaap7294
DOI: 10.1126/scitranslmed.aap7294

In silico sleuthing for pulmonary hypertension

Cell proliferation and fibrosis (the accumulation of excess connective tissue) cause arterioles to thicken during pulmonary arterial hypertension (PAH). Aldosterone, a hormone involved in reactive oxygen species generation, wound healing, and fibrosis, is also increased in PAH. Samokhin et al. used in silico analysis to identify NEDD9 as a critical protein involved in vascular remodeling, fibrosis, and pulmonary hypertension. Oxidative modification of NEDD9 impaired its degradation and promoted collagen production. Mice lacking NEDD9 were protected from pulmonary hypertension, and collagen deposition, vascular remodeling, and cardiopulmonary metrics were normalized in a rat model of PAH treated with siRNA targeting NEDD9. This work suggests that therapeutic targeting of NEDD9 may be effective for combating vascular fibrosis in PAH.


Germline mutations involving small mothers against decapentaplegic–transforming growth factor–β (SMAD–TGF-β) signaling are an important but rare cause of pulmonary arterial hypertension (PAH), which is a disease characterized, in part, by vascular fibrosis and hyperaldosteronism (ALDO). We developed and analyzed a fibrosis protein-protein network (fibrosome) in silico, which predicted that the SMAD3 target neural precursor cell expressed developmentally down-regulated 9 (NEDD9) is a critical ALDO-regulated node underpinning pathogenic vascular fibrosis. Bioinformatics and microscale thermophoresis demonstrated that oxidation of Cys18 in the SMAD3 docking region of NEDD9 impairs SMAD3-NEDD9 protein-protein interactions in vitro. This effect was reproduced by ALDO-induced oxidant stress in cultured human pulmonary artery endothelial cells (HPAECs), resulting in impaired NEDD9 proteolytic degradation, increased NEDD9 complex formation with Nk2 homeobox 5 (NKX2-5), and increased NKX2-5 binding to COL3A1. Up-regulation of NEDD9-dependent collagen III expression corresponded to changes in cell stiffness measured by atomic force microscopy. HPAEC-derived exosomal signaling targeted NEDD9 to increase collagen I/III expression in human pulmonary artery smooth muscle cells, identifying a second endothelial mechanism regulating vascular fibrosis. ALDO-NEDD9 signaling was not affected by treatment with a TGF-β ligand trap and, thus, was not contingent on TGF-β signaling. Colocalization of NEDD9 with collagen III in HPAECs was observed in fibrotic pulmonary arterioles from PAH patients. Furthermore, NEDD9 ablation or inhibition prevented fibrotic vascular remodeling and pulmonary hypertension in animal models of PAH in vivo. These data identify a critical TGF-β–independent posttranslational modification that impairs SMAD3-NEDD9 binding in HPAECs to modulate vascular fibrosis and promote PAH.

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