Ezrin drives adaptation of monocytes to the inflamed lung microenvironment

Ezrin, an actin-binding protein, plays a crucial role in organizing the cellular cortical cytoskeleton and plasma membrane during cell migration, adhesion, and proliferation. While there is a good understanding of ezrin's function in cell types such as epithelial cells and lymphocytes, its role in monocytes/macrophages (MΦs) is less understood. Here, we used a monocyte/MΦ-specific ezrin knock-out mouse model to investigate the contribution of ezrin to monocyte recruitment and adaptation to the lung extracellular matrix (ECM) in response to lipopolysaccharide (LPS). Our study revealed that LPS induces ezrin expression in monocytes/MΦs, and that ezrin is essential for monocytes to adhere to lung ECM, proliferate, and differentiate into tissue-resident interstitial MΦs. Notably, ezrin is not required for monocyte extravasation into the lung parenchyma. Mechanistically, the loss of ezrin in monocytes disrupts activation of FAK and AKT signaling, which are necessary for lung-recruited monocytes and monocyte-derived MΦs to adhere to the ECM, proliferate, and survive. In summary, our data suggest that ezrin plays a role beyond structural cellular support, influencing diverse monocytes/MΦ processes and signaling pathways in response to infections, driving their adaptation to the lung microenvironment. In this study, we performed high-throughput sequencing of RNA isolated from lung monocyte and macrophage populations (monocyte derived macrophages -moMs, transitional interstitial macrophages (tr/tnsIMs), mature interstitial macrophages (matIMs) of (WT) and B6.Ezrinfl/fl.Cx3cr1tm1.1(cre)Jung/J (Ez-KO) mice that were exposed to LPS for 24h. Sequencing was performed performed in 3 biological replicates per genotype, celltype and timepoint.