MNK-driven eIF4E phosphorylation regulates the fibrogenic transformation of mesenchymal cells and chronic lung allograft dysfunction
Natalie M. Walker, … , Amanda L. Garner, Vibha N. Lama
Natalie M. Walker, … , Amanda L. Garner, Vibha N. Lama
Published August 15, 2024
Citation Information: J Clin Invest. 2024;134(16):e168393. https://doi.org/10.1172/JCI168393.
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Research Article Pulmonology Transplantation

MNK-driven eIF4E phosphorylation regulates the fibrogenic transformation of mesenchymal cells and chronic lung allograft dysfunction

Abstract

Tissue fibrosis remains unamenable to meaningful therapeutic interventions and is the primary cause of chronic graft failure after organ transplantation. Eukaryotic translation initiation factor (eIF4E), a key translational regulator, serves as convergent target of multiple upstream profibrotic signaling pathways that contribute to mesenchymal cell (MC) activation. Here, we investigate the role of MAP kinase–interacting serine/threonine kinase–induced (MNK-induced) direct phosphorylation of eIF4E at serine 209 (Ser209) in maintaining fibrotic transformation of MCs and determine the contribution of the MNK/eIF4E pathway to the pathogenesis of chronic lung allograft dysfunction (CLAD). MCs from patients with CLAD demonstrated constitutively higher eIF4E phosphorylation at Ser209, and eIF4E phospho-Ser209 was found to be critical in regulating key fibrogenic protein autotaxin, leading to sustained β-catenin activation and profibrotic functions of CLAD MCs. MNK1 signaling was upregulated in CLAD MCs, and genetic or pharmacologic targeting of MNK1 activity inhibited eIF4E phospho-Ser209 and profibrotic functions of CLAD MCs in vitro. Treatment with an MNK1/2 inhibitor (eFT-508) abrogated allograft fibrosis in an orthotopic murine lung-transplant model. Together these studies identify what we believe is a previously unrecognized MNK/eIF4E/ATX/β-catenin signaling pathway of fibrotic transformation of MCs and present the first evidence, to our knowledge, for the utility of MNK inhibitors in fibrosis.

Authors

Natalie M. Walker, Yuta Ibuki, A. Patrick McLinden, Keizo Misumi, Dylan C. Mitchell, Gabriel G. Kleer, Alison M. Lock, Ragini Vittal, Nahum Sonenberg, Amanda L. Garner, Vibha N. Lama

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Figure 3

MNK/eIF4E (Ser209) activation drives profibrotic phenotypes in lung MCs.

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MNK/eIF4E (Ser209) activation drives profibrotic phenotypes in lung MCs....
(A) MCs isolated from fibrotic (Fib-MCs) and normal human lung allografts (non-Fib-MCs) were infected with lentiviral particles containing pLenti-LoxEV–eIF4E (S209A) and pLenti-LoxEV–eIF4E (S209D), respectively, and then cultured in Matrigel-coated Transwells. Cell migration was assessed by MTT assay. (B) Fib-MCs were transfected with EIF4E or scrambled control siRNA followed by lentiviral infection of empty vector or vector expressing S209A or S209D. Protein lysates were immunoblotted against collagen I. Representative immunoblots and corresponding densitometry are shown. (C and D) Fib-MCs were transfected with scrambled or MNK1 siRNA (C) or treated with eFT-508 (10 μM, 2 hours) (D). Protein lysates were immunoblotted against collagen I and SPARC. Representative immunoblots and corresponding densitometry are shown. (E) Proliferation was assessed in Fib-MCs treated with eFT-508 (10 μM, 72 hours) using Cyquant Proliferation Assay Kit. Protein lysates were immunoblotted for cyclin D1 as well as phosphorylated and total eIF4E. Data are represented as means ± SEM. **P < 0.01; ***P < 0.001; ****P < 0.0001, unpaired t test (A, C, D, and E); 1-way ANOVA; post hoc test: Bonferroni’s test (B).