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

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 6

Pharmacologic MNK inhibition utilizing eFT-508 decreases lung allograft fibrosis and ATX expression in a murine orthotopic left lung–transplant model of RAS.

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Pharmacologic MNK inhibition utilizing eFT-508 decreases lung allograft ...
(A) Experimental schematic. B6D2F1/J donor lungs were transplanted into C57BL/6J recipient mice, followed by treatment with eFT-508 (5 mg/kg/d; oral gavage) between days 7 and 28. (B) Histopathology examination of formalin-fixed, paraffin-embedded tissues — isografts (Iso), RAS allografts (Allo), and eFT-508-treated RAS allografts (Allo+eFT-508) at day 28 using H&E staining (top panels) and Masson’s trichrome staining (bottom panels). Scale bars: 100 μm. V, vessel; AW, airway. (C) Acid-digested lung homogenates were assessed for collagen content by hydroxyproline assay. n = 6–8. Data are represented as means ± SEM. ***P < 0.001; ****P < 0.0001, 1-way ANOVA; post hoc test: Bonferroni’s test. (D) Gli1CreERT2/WT;Rosa26mTmG/WT murine allograft controls or treated with eFT-508 were harvested at day 14 after transplant. Top panels: dual-labeling against GFP (green) and α-smooth muscle actin (α-SMA) (red). Nuclear counterstaining was by DAPI. Original magnification, ×400. Scale bars: 50 μm. Bottom panels: Masson’s trichrome staining in contiguous sections indicating collagen deposition (blue). (E) eFT-508 therapeutic treatment regimen from days 28 to 40 after transplant resulted in reduced collagen content as measured by hydroxyproline assay. *P < 0.05, unpaired t test. (F and G) Supernatants from day 28–transplanted lung homogenates were analyzed for ATX levels by sandwich ELISA (F) and ATX activity utilizing FS-3 fluorogenic substrate (G). n = 7–9. Data are represented as means ± SEM. **P < 0.01; ****P < 0.0001, simple linear regression.