Signal Transduction and Targeted Therapy | Targeting FUS Protein with Antisense Oligonucleotide Strategy for Treating Idiopathic Pulmonary Fibrosis

This study is the first to reveal the pro-fibrotic role of the FUS protein in idiopathic pulmonary fibrosis (IPF) and demonstrates that the antisense oligonucleotide ION363 effectively suppresses FUS expression and improves alveolar epithelial regeneration, offering a novel targeted therapeutic strategy for IPF.

 

Literature Overview

The article titled "Targeting fused in sarcoma (FUS): a novel antisense strategy for treating idiopathic pulmonary fibrosis," published in the journal Signal Transduction and Targeted Therapy, reviews and summarizes the pathological role of the RNA-binding protein FUS in idiopathic pulmonary fibrosis (IPF) and its potential as a therapeutic target. The study finds that FUS is upregulated and mislocalized to the cytoplasm in lung fibroblasts of IPF patients, where it promotes disease progression by binding to pro-fibrotic mRNAs. Targeting FUS with the antisense oligonucleotide ION363 significantly suppresses the expression of fibrosis-related genes and improves the morphology and function of 3D alveolar organoids. This work systematically elucidates the regulatory mechanisms of FUS in IPF and validates its feasibility as a therapeutic target, offering a promising new direction for IPF treatment.

Background Knowledge

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, and fatal interstitial lung disease primarily affecting older adults. It is characterized by alveolar epithelial injury, abnormal fibroblast activation, and excessive deposition of extracellular matrix (ECM), ultimately leading to destruction of lung architecture and respiratory failure. Currently, only nintedanib and pirfenidone are approved for treatment; although they can slow the decline in lung function, they do not reverse fibrosis or significantly extend survival, highlighting an urgent need for novel therapeutic strategies. FUS (fused in sarcoma) is a highly conserved RNA-binding protein involved in RNA splicing, transport, translational regulation, and DNA damage repair. Mutations in FUS are closely associated with amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), and cytoplasmic mislocalization and aggregation of FUS are hallmark pathological features of neurodegenerative diseases. Recent studies suggest that FUS plays a critical role in age-related proteostasis imbalance, but its function in pulmonary fibrosis remains unclear. Antisense oligonucleotides (ASOs) are single-stranded nucleic acid therapeutics that bind target mRNAs via base complementarity, inducing degradation or modulating splicing, and have been successfully applied in neurological disorders such as spinal muscular atrophy. ION363 is an ASO targeting FUS that has demonstrated the ability to reduce FUS protein levels in ALS models. This study is the first to explore the role of FUS in IPF and evaluate the therapeutic potential of ION363, filling a research gap in fibrotic diseases and providing strong evidence for expanding ASO therapies to non-neurodegenerative conditions.

 

 

Research Methods and Experiments

The research team utilized primary lung fibroblasts derived from IPF patients and healthy donors, analyzing FUS expression and localization using qPCR, immunoblotting, and immunofluorescence. Subcellular fractionation and immuno-electron microscopy were further employed to confirm cytoplasmic mislocalization of FUS in IPF fibroblasts. The impact of FUS on fibroblast proliferation was evaluated through overexpression and siRNA knockdown experiments. CLIP-Seq was used to identify the RNA interaction network of FUS in IPF fibroblasts, and RNA-seq was performed to analyze transcriptomic changes following ION363 treatment. The effects of ION363 on fibrotic markers, epithelial function, and tissue regeneration were assessed in precision-cut lung slices (PCLs) and 3D alveolosphere organoid models. Standard-of-care drugs (pirfenidone, nintedanib) were tested for their effects on FUS expression in PCLs. All experiments included appropriate control groups, such as scramble ASO and vehicle-treated controls.

Key Conclusions and Perspectives

• FUS mRNA and protein levels are significantly upregulated in lung fibroblasts from IPF patients, with abnormal cytoplasmic mislocalization, whereas FUS is predominantly nuclear in healthy control cells
• Functional experiments show that FUS overexpression promotes proliferation in healthy fibroblasts, while FUS knockdown reverses the hyperproliferative phenotype of IPF fibroblasts, indicating that FUS drives fibroblast activation
• CLIP-Seq analysis reveals that FUS specifically binds to multiple pro-fibrotic RNAs in IPF fibroblasts, including TGFβ1, COL5A1, COL4A2, and IL11, which are enriched in ECM organization and collagen synthesis pathways
• The antisense oligonucleotide ION363 effectively reduces FUS RNA and protein expression in IPF fibroblasts, decreases expression of fibrotic factors such as PAI-1 and COL1A1, and inhibits cell migration
• In PCL models derived from IPF patients, ION363 significantly downregulates FUS expression, suppresses pro-fibrotic gene programs, and enhances expression of alveolar epithelial-related genes (e.g., SFTPA1, ABCA3)
• In 3D alveolosphere models, ION363 treatment enhances lysosomal activity, promotes the formation and expansion of alveolar organoids, and upregulates the AT1 cell marker AQP5, indicating improved alveolar epithelial regeneration and differentiation
• Standard IPF therapies—pirfenidone and nintedanib—reduce FUS expression in PCLs, suggesting that FUS may be one of the targets of existing treatments

Research Significance and Prospects

This study establishes FUS as a key pro-fibrotic regulator in IPF, with its aberrant expression and mislocalization playing a significant role in disease progression. FUS drives fibroblast activation and ECM deposition by binding to pro-fibrotic mRNAs and modulating their stability or translation. This finding expands our understanding of RNA-binding proteins in fibrotic diseases and provides new insights into the molecular mechanisms of IPF.

The antisense oligonucleotide ION363 targeting FUS demonstrates significant anti-fibrotic effects in multiple preclinical IPF models, exhibiting a "dual-action" advantage by not only inhibiting fibroblast activity but also promoting alveolar epithelial regeneration. Compared to current therapies that merely slow disease progression, ION363 holds promise as a disease-modifying agent capable of promoting tissue repair. Moreover, ION363 has already demonstrated safety in clinical trials for ALS, potentially accelerating its translational application in IPF.

Future studies should further explore the role of FUS in different lung cell types (e.g., AT2 cells, macrophages) and validate the in vivo efficacy and pharmacokinetics of ION363 in animal models. Additionally, the precise molecular mechanisms by which FUS regulates pro-fibrotic RNAs—such as effects on mRNA stability, translational efficiency, or subcellular localization—need to be clarified. This study lays a solid foundation for developing ASO-based therapeutic strategies for IPF, potentially offering breakthrough treatments for patients.

 

 

Conclusion

This study systematically reveals the critical pro-fibrotic role of the RNA-binding protein FUS in idiopathic pulmonary fibrosis (IPF). FUS is upregulated and mislocalized to the cytoplasm in lung fibroblasts of IPF patients, where it promotes fibroblast proliferation and activation by binding to pro-fibrotic mRNAs such as TGFβ1, COL5A1, and IL11. The antisense oligonucleotide ION363, which targets FUS, effectively reduces FUS expression, suppresses fibrosis-related gene programs, and improves alveolar epithelial function and tissue regeneration in precision-cut lung slices and 3D alveolosphere models. This work is the first to link FUS to IPF pathogenesis and proposes FUS as a promising new therapeutic target. ION363 exhibits a dual mechanism of action—suppressing interstitial fibrosis while promoting epithelial repair—surpassing current therapies that only slow lung function decline. Given that ION363 has already demonstrated safety in clinical trials for neurological diseases, its translational potential in IPF is substantial. This research not only deepens our understanding of the molecular mechanisms of IPF but also provides crucial evidence for developing disease-modifying therapies, potentially offering more effective treatment options for IPF patients.

 

Bhavika B Katariya, Shashipavan Chillappagari, Lisa Arnold, Andreas Guenther, and Poornima Mahavadi. Targeting fused in sarcoma (FUS): a novel antisense strategy for treating idiopathic pulmonary fibrosis. Signal Transduction and Targeted Therapy.