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Cldn18 −/− mice reveal novel role for YAP signaling in regulation of distal lung epithelial stem/progenitor cell homeostasis
Author(s) -
Borok Zea,
Zhou Beiyun,
Flodby Per,
Castillo Dan R,
Luo Jiao,
Yu FaXing,
McConnell Alicia,
Varghese Bino A,
Li Guanglei,
Conti Peter S,
Liu Yixin,
Sunohara Mitsuhiro,
Liebler Janice M,
Yang Chenchen,
Marconett Crystal N,
LairdOffringa Ite A,
Minoo Parviz,
Guan KunLiang,
Stripp Barry R,
Crandall Edward D
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.60.1
Subject(s) - progenitor cell , claudin , tight junction , microbiology and biotechnology , stem cell , homeostasis , lung , chemistry , biology , medicine
Claudins are integral tight junction (TJ) proteins that contribute to cell polarity and regulate paracellular permeability to ions and solutes. Claudin 18 (CLDN18) is one of the most highly expressed claudin family members in lung alveolar epithelium. To investigate the role of CLDN18 in alveolar homeostasis, we recently generated Cldn18 −/− mice that demonstrate increased lung solute permeability and alveolar fluid clearance (AFC) compared to wild type (WT) controls. Lungs of Cldn18 −/− mice are markedly enlarged due to increased abundance and proliferation of alveolar epithelial type II (AT2) cells, known progenitors of distal lung epithelium, with resultant parenchymal expansion. Cldn18 −/− AT2 cells grown with MLg fibroblasts in 3‐dimensional (3D) culture show increased colony forming efficiency (CFE), suggesting increased progenitor capacity. Given its known role in regulating stem/progenitor cell proliferation and organ size, we investigated a potential role for Yes‐associated protein (YAP) signaling in mediating the proliferative phenotype of Cldn18 −/− lung progenitors. Progenitor cell activation was accompanied by activation of YAP, as evidenced by increased nuclear YAP, increased expression of YAP target genes in lungs of Cldn18 −/− mice, and increased YAP and decreased phospho‐YAP (p‐YAP) by western analysis in isolated Cldn18 −/− AT2 cells and by immunofluorescence in Cldn18 −/− AT2 cells in 3D culture. Treatment with the YAP inhibitor verteporfin (VP, 100 mg/kg) reduced AT2 cell proliferation in vivo (EdU + NKX2.1 + /total cells: 1.36 ± 0.10% vehicle vs 0.93 ± 0.06% VP, p<0.05) and decreased lung size (lung dry weight/body weight ratios (mg/g): 3.56 ± 0.08 vehicle vs 2.93 ± 0.13 VP, p<0.05) in Cldn18 −/− mice. Inhibition of YAP with VP (0.75 μM) or shRNA decreased colony size (~50% vs control) and number (30–50% vs control) and reduced proliferation (Ki67 + cells at 10.7 ± 0.4% VP vs 29.2 ± 3.7% vehicle) of Cldn18 −/− AT2 cells in 3D culture, while overexpression of CLDN18 decreased YAP nuclear localization, cell proliferation, CFE and YAP activity. These results reveal a novel role for YAP signaling in regulation of distal lung epithelial progenitor cell homeostasis and identify a role for TJ proteins, in particular CLDN18, in regulating YAP activity and organ size. Overall, they suggest a mechanism whereby growth‐promoting signals are transduced from TJ to the nucleus that has important implications for modulating stem/progenitor cell function and regeneration following injury. Support or Funding Information National Institutes of Health, Hastings and Whittier Foundations