Targeting activated fibroblasts, including myofibroblast differentiation, has emerged as a key therapeutic strategy in patients with
idiopathic pulmonary fibrosis (IPF). However, there is no available
therapy capable of selectively eradicating myofibroblasts or limiting their genesis. Through an integrative analysis of the regulator genes that are responsible for the activation of IPF fibroblasts, we noticed the
phosphatidylinositol 4,5-bisphosphate (PIP2)-binding
protein,
myristoylated alanine-rich C-kinase substrate (MARCKS), as a potential target molecule for IPF. Herein, we have employed a 25-mer novel
peptide, MARCKS phosphorylation site domain sequence (MPS), to determine if MARCKS inhibition reduces
pulmonary fibrosis through the inactivation of PI3K/
protein kinase B (AKT) signaling in fibroblast cells. We first observed that higher levels of MARCKS phosphorylation and the myofibroblast marker α-smooth muscle actin (α-SMA) were notably overexpressed in all tested IPF lung tissues and fibroblast cells. Treatment with the MPS
peptide suppressed levels of MARCKS phosphorylation in primary IPF fibroblasts. A kinetic assay confirmed that this
peptide binds to
phospholipids, particularly PIP2, with a dissociation constant of 17.64 nM. As expected, a decrease of
phosphatidylinositol (3,4,5)-trisphosphate pools and AKT activity occurred in MPS-treated IPF fibroblast cells. MPS
peptide was demonstrated to impair cell proliferation, invasion, and migration in multiple IPF fibroblast cells in vitro as well as to reduce
pulmonary fibrosis in bleomycin-treated mice in vivo. Surprisingly, we found that MPS
peptide decreases α-SMA expression and synergistically interacts with
nintedanib treatment in IPF fibroblasts. Our data suggest MARCKS as a druggable target in
pulmonary fibrosis and also provide a promising antifibrotic agent that may lead to effective IPF treatments.-Yang, D. C., Li, J.-M., Xu, J., Oldham, J., Phan, S. H., Last, J. A., Wu, R., Chen, C.-H. Tackling MARCKS-PIP3 circuit attenuates fibroblast activation and
fibrosis progression.