ITGBL1-MYH9 interaction in hepatic stellate cells acts as a mechano-regulator controlling liver fibrosis in mice

Hepatic stellate cell (HSC) activation can lead to liver fibrosis, for which there are no effective treatments. Aberrant cytoskeletal reorganization is a central driver of HSC activation. Non-muscle myosin II (NM II) is known to regulate cytoskeleton remodeling via its actin cross-linking and contractile properties. However, the molecular players controlling actomyosin assembly and contractility in HSCs during liver fibrosis remain poorly defined. Here, we identified integrin β-like 1 (ITGBL1) as a gatekeeper of HSC quiescence by negatively regulating actomyosin contractility-driven mechanotransduction in HSCs. ITGBL1 expression was markedly elevated in activated HSCs found in patient and mouse fibrotic livers. Unexpectedly, HSC-specific Itgbl1 deficiency worsened liver fibrosis, whereas ITGBL1 overexpression in HSCs limited it, suggesting a protective role for ITGBL1 against a pathogenic HSC activation. Multi-omics and functional analyses revealed that ITGBL1 impaired F-actin filament organization in HSCs by disrupting myosin heavy chain 9 (MYH9, also named NM II heavy chain A)-dependent actomyosin assembly. In line, HSC-specific Myh9 deficiency or silencing of Myh9 in HSCs alleviated liver fibrosis. Taken together, our findings unveil the ITGBL1-MYH9 interaction acts as a critical mechano-regulatory brake that maintains cytoskeletal equilibrium and mechanical homeostasis in HSCs, providing a promising therapeutic strategy to combat liver fibrosis.