# PTPN1 Regulation via YBX1-PTBP1 Interaction Promotes Fibroblast Activation and Fibrotic Remodeling in the Lung

## TL;DR

This study shows how YBX1 promotes lung fibrosis by interacting with PTBP1 and regulating PTPN1, offering new therapeutic insights for idiopathic pulmonary fibrosis.

## Contribution

The novel contribution is identifying YBX1's role in promoting fibroblast activation via the PTBP1/PTPN1 axis in lung fibrosis.

## Key findings

- YBX1 overexpression enhances TGF-β1-induced fibroblast activation and ECM deposition.
- YBX1 interacts with PTBP1 and regulates PTPN1 transcription to drive fibroblast-to-myofibroblast transition.
- AAV-delivered Ybx1 shRNA reduces fibrosis markers in a murine model of lung fibrosis.

## Abstract

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive interstitial pneumonia of unknown etiology. Its pathogenesis involves complex multicellular interactions and signaling pathways, with fibroblast-to-myofibroblast transition (FMT) being critical for fibrogenesis. Although the transcription factor Y-box binding protein 1 (YBX1) regulates processes such as cell proliferation, transcription, translation, and DNA repair, its role in IPF remains undefined. Here, we demonstrate that YBX1 overexpression significantly promotes transforming growth factor-β1 (TGF-β1)-induced pulmonary FMT, leading to substantially increased extracellular matrix (ECM) deposition in primary human (PHLFs) and mouse (PMLFs) lung fibroblasts. Conversely, YBX1 inhibition markedly suppresses TGF-β1-driven aberrant fibroblast migration and activation. Mechanistically, YBX1 interacts with polypyrimidine tract-binding protein 1 (PTBP1) and binds to the protein tyrosine phosphatase nonreceptor type 1 (PTPN1) promoter to transcriptionally regulate PTPN1, thereby driving FMT. In vivo, intratracheal delivery of Ybx1-targeting shRNA via adeno-associated virus (AAV) robustly attenuates ECM deposition, hydroxyproline content, and fibrotic marker expression in a bleomycin (BLM)-induced murine fibrosis model. Our findings identify YBX1 as a promoter of lung FMT via the PTBP1/PTPN1 axis, offering mechanistic insights for the development of YBX1-targeted therapeutic strategies for IPF.