Claudin-18–mediated YAP activity regulates lung stem and progenitor cell homeostasis and tumorigenesis
Beiyun Zhou, … , Edward D. Crandall, Zea Borok
Beiyun Zhou, … , Edward D. Crandall, Zea Borok
Published March 1, 2018; First published February 5, 2018
Citation Information: J Clin Invest. 2018;128(3):970-984. https://doi.org/10.1172/JCI90429.
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Categories: Research Article Pulmonology Stem cells

Claudin-18–mediated YAP activity regulates lung stem and progenitor cell homeostasis and tumorigenesis

Abstract

Claudins, the integral tight junction (TJ) proteins that regulate paracellular permeability and cell polarity, are frequently dysregulated in cancer; however, their role in neoplastic progression is unclear. Here, we demonstrated that knockout of Cldn18, a claudin family member highly expressed in lung alveolar epithelium, leads to lung enlargement, parenchymal expansion, increased abundance and proliferation of known distal lung progenitors, the alveolar epithelial type II (AT2) cells, activation of Yes-associated protein (YAP), increased organ size, and tumorigenesis in mice. Inhibition of YAP decreased proliferation and colony-forming efficiency (CFE) of Cldn18–/– AT2 cells and prevented increased lung size, while CLDN18 overexpression decreased YAP nuclear localization, cell proliferation, CFE, and YAP transcriptional activity. CLDN18 and YAP interacted and colocalized at cell-cell contacts, while loss of CLDN18 decreased YAP interaction with Hippo kinases p-LATS1/2. Additionally, Cldn18–/– mice had increased propensity to develop lung adenocarcinomas (LuAd) with age, and human LuAd showed stage-dependent reduction of CLDN18.1. These results establish CLDN18 as a regulator of YAP activity that serves to restrict organ size, progenitor cell proliferation, and tumorigenesis, and suggest a mechanism whereby TJ disruption may promote progenitor proliferation to enhance repair following injury.

Authors

Beiyun Zhou, Per Flodby, Jiao Luo, Dan R. Castillo, Yixin Liu, Fa-Xing Yu, Alicia McConnell, Bino Varghese, Guanglei Li, Nyam-Osor Chimge, Mitsuhiro Sunohara, Michael N. Koss, Wafaa Elatre, Peter Conti, Janice M. Liebler, Chenchen Yang, Crystal N. Marconett, Ite A. Laird-Offringa, Parviz Minoo, Kunliang Guan, Barry R. Stripp, Edward D. Crandall, Zea Borok

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Figure 1

Increased cellularity, alveolar epithelial type II (AT2) cell abundance, and parenchymal expansion in Cldn18–/– mice.

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Increased cellularity, alveolar epithelial type II (AT2) cell abundance,...
(A) H&E staining shows increased cellularity in Cldn18–/– lungs (age 1 month) with variability among mice (middle and right panels). Scale bar: 50 μm. n ≥ 7 each genotype. (B) Lungs of Cldn18–/– mice (age 3 weeks) are enlarged. Representative of 3 mice for each genotype. (C) Lung dry weight/body weight (BW) ratios of Cldn18–/– mice are increased. n ≥ 33 mice of each genotype, age 5–9 months. Bar graphs represent means ± SEM. Unpaired 2-tailed t test. *P < 0.05. (D) Pressure-volume curves show increased lung volume in Cldn18–/– mice with unchanged compliance. Each data point represents the mean ± SEM of 3 mice of each genotype, age 7–8 months. Two-way ANOVA with Bonferroni’s correction. *P < 0.05 for Cldn18–/– versus WT lungs at zero pressure. (E) Left panel (whole lung): Texture-based volume rendering shows lung enlargement in Cldn18–/– mice. Right panel (alveoli): High-resolution CT shows increased parenchymal thickness in Cldn18–/– mice. Representative of 3 mice for each genotype. (F and G) Representative immunofluorescence and quantification show increased numbers of NKX2-1+ cells (pink) in Cldn18–/– versus WT mice. Nuclei labeled with DAPI (blue). n = 3 age-matched mice of each genotype, age 2–9 months. Unpaired 2-tailed t test. *P < 0.05. Scale bars: 50 μm. Representative immunofluorescence (H) and quantification (I) show increased numbers of SFTPC+ cells (green) in Cldn18–/– versus WT mice. Nuclei labeled with DAPI (blue). n = 3 age-matched mice of each genotype. Unpaired 2-tailed t test. *P < 0.05. Scale bars: 50 μm. (J) AT2 cell yield is increased in Cldn18–/– mice. n = 10 mice per group with 8 independent cell isolations. Unpaired 2-tailed t test. *P < 0.05. Bar graphs represent the mean ± SEM for C, G, I, and J.