Epithelial membrane protein 2 governs transepithelial migration of neutrophils into the airspace
Wan-Chi Lin, … , Joseph P. Mizgerd, Michael B. Fessler
Wan-Chi Lin, … , Joseph P. Mizgerd, Michael B. Fessler
Published September 24, 2019
Citation Information: J Clin Invest. 2020;130(1):157-170. https://doi.org/10.1172/JCI127144.
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Research Article Inflammation Pulmonology

Epithelial membrane protein 2 governs transepithelial migration of neutrophils into the airspace

Abstract

Whether respiratory epithelial cells regulate the final transit of extravasated neutrophils into the inflamed airspace or are a passive barrier is poorly understood. Alveolar epithelial type 1 (AT1) cells, best known for solute transport and gas exchange, have few established immune roles. Epithelial membrane protein 2 (EMP2), a tetraspan protein that promotes recruitment of integrins to lipid rafts, is highly expressed in AT1 cells but has no known function in lung biology. Here, we show that Emp2–/– mice exhibit reduced neutrophil influx into the airspace after a wide range of inhaled exposures. During bacterial pneumonia, Emp2–/– mice had attenuated neutrophilic lung injury and improved survival. Bone marrow chimeras, intravital neutrophil labeling, and in vitro assays suggested that defective transepithelial migration of neutrophils into the alveolar lumen occurs in Emp2–/– lungs. Emp2–/– AT1 cells had dysregulated surface display of multiple adhesion molecules, associated with reduced raft abundance. Epithelial raft abundance was dependent upon putative cholesterol-binding motifs in EMP2, whereas EMP2 supported adhesion molecule display and neutrophil transmigration through suppression of caveolins. Taken together, we propose that EMP2-dependent membrane organization ensures proper display on AT1 cells of a suite of proteins required to instruct paracellular neutrophil traffic into the alveolus.

Authors

Wan-Chi Lin, Kymberly M. Gowdy, Jennifer H. Madenspacher, Rachel L. Zemans, Kazuko Yamamoto, Miranda Lyons-Cohen, Hideki Nakano, Kyathanahalli Janardhan, Carmen J. Williams, Donald N. Cook, Joseph P. Mizgerd, Michael B. Fessler

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Figure 3

EMP2-null mice have reduced mortality and lung injury during bacterial pneumonia.

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EMP2-null mice have reduced mortality and lung injury during bacterial p...
(A) Emp2+/+ and Emp2–/– mice were infected with K. pneumoniae by oropharyngeal aspiration and then had bacterial CFUs quantified in lung homogenates 24 hours after infection (n = 11–12/genotype). (B) Survival was monitored in mice infected with K. pneumoniae as in A (n = 20/genotype). (C) BALF protein, albumin, and IgM were measured in mice 48 hours after K. pneumoniae inhalation (n = 5–6/genotype). (D) Serum TNF-α and IL-6 were quantified by ELISA 48 hours after lung infection with K. pneumoniae. (E) Representative images of lungs from mice (n = 4–5/genotype; ×1 magnification) 48 hours after infection with K. pneumoniae by oropharyngeal aspiration. Inflammatory areas are indicated by arrows; arrowhead points to inflammation on the pleural surface. Inflammation (predominantly neutrophilic infiltration) was more severe in Emp2+/+ mice. Data in A, C, and D are mean ± SEM and are representative of at least 3 independent experiments. †P = 0.06; *P < 0.05; **P < 0.01 by unpaired 2-tailed Student’s t test or log-rank test (survival).