Aberrant expression of the PREX2-MAGI2 axis modulates myofibroblast differentiation in pulmonary fibrosis

Myofibroblast differentiation is a pivotal event in idiopathic pulmonary fibrosis (IPF) and is driven by TGF-β1-dependent PTEN destabilization; however, the intermediate regulators remain incompletely defined. We tested three lung fibroblast cell lines (one normal and two IPF-derived) and identified the phosphatidylinositol 3,4,5-trisphosphate-dependent Rac exchanger 2 (PREX2)-membrane-associated guanylate kinase inverted 2 (MAGI2) as a critical regulator of myofibroblast differentiation. Loss-of-function analysis of MAGI2 in normal human lung fibroblasts revealed a shift toward a myofibroblast phenotype characterized by abundant α-SMA expression. In vitro experiments revealed increased PREX2 expression and decreased MAGI2 expression in IPF-derived lung fibroblasts compared with those in normal lung fibroblasts. Consistent with this finding, in vivo experiments using bleomycin-induced murine pulmonary fibrosis revealed PREX2 upregulation in contrast to MAGI2 downregulation with the progression of lesions. Notably, PREX2 depletion in IPF-derived cells enhanced MAGI2 expression, mitigating TGF-β1-induced α-SMA expression. Conversely, PREX2 overexpression promoted myofibroblast differentiation, as evidenced by MAGI2 downregulation followed by marked α-SMA expression. The PREX2-targeting suppressive miR-338-3p upregulated MAGI2 expression in vitro and ameliorated bleomycin-induced murine pulmonary fibrosis in vivo. Immunohistochemical staining of PREX2 on lung samples obtained from patients with IPF delineated that PREX2 was exclusively expressed in the fibroblastic foci of IPF-affected lungs. Fluorescence immunostaining revealed PREX2 colocalization with α-SMA in myofibroblasts within fibroblastic foci, corroborating our hypothesis. These findings suggest that MAGI2 acts as a negative regulator of myofibroblast differentiation by stabilizing PTEN, whereas PREX2 is aberrantly expressed in the fibrotic milieu, negatively modulating MAGI2, thereby accelerating pulmonary fibrosis.