PKM2 promotes pulmonary fibrosis by stabilizing TGF-beta 1 receptor I and enhancing TGF-beta 1 signaling

Idiopathic pulmonary fibrosis (IPF) is a progressive interstitial lung disease, and the molecular mechanisms remain poorly understood. Our findings demonstrated that pyruvate kinase M2 (PKM2) promoted fibrosis progression by directly interacting with Smad7 and reinforcing transforming growth factor-beta 1 (TGF-beta 1) signaling. Total PKM2 expression and the portion of the tetrameric form elevated in lungs and fibroblasts were derived from mice with bleomycin (BLM)-induced pulmonary fibrosis. Pkm2 deletion markedly alleviated BLM-induced fibrosis progression, myofibroblast differentiation, and TGF-beta 1 signaling activation. Further study showed that PKM2 tetramer enhanced TGF-beta 1 signaling by directly binding with Smad7 on its MH2 domain, and thus interfered with the interaction between Smad7 and TGF-beta type I receptor (T beta R1), decreased T beta R1 ubiquitination, and stabilized T beta R1. Pharmacologically enhanced PKM2 tetramer by TEPP-46 promoted BLM-induced pulmonary fibrosis, while tetramer disruption by compound 3k alleviated fibrosis progression. Our results demonstrate how PKM2 regulates TGF-beta 1 signaling and is a key factor in fibrosis progression.