MRCKα interacts with and mediates Na+, K+-ATPase-induced tight junction assembly in the lung epithelium.

An intact lung epithelial barrier is essential for lung homeostasis The Na+, K+-ATPase (NKA), primarily serving as an ion transporter, also regulates epithelial barrier function via modulation of tight junctions However, the underlying mechanism is not well-understood Here, we showed that overexpression of the NKA beta1 subunit upregulates the expression of tight junction proteins, leading to increased alveolar epithelial barrier function by an ion transport-independent mechanism Using immunoprecipitation and mass spectrometry, we identified a number of unknown protein interactions of the beta1 subunit, including a top candidate, myotonic dystrophy kinase-related cdc42-binding kinase alpha (MRCKalpha), a protein kinase known to regulate peripheral actin formation Using a doxycycline-inducible gene expression system, we demonstrated that MRCKalpha and its downstream activation of myosin light chain is required for the regulation of alveolar barrier function by the NKA beta1 subunit Importantly, MRCKalpha is expressed in both human airways and alveoli and has reduced expression in patients with Acute Respiratory Distress Syndrome (ARDS), a lung illness that can be caused by multiple direct and indirect insults, including the infection of influenza virus and SARS-CoV-2 Our results have elucidated a novel mechanism by which NKA regulates epithelial tight junctions and identified potential drug targets for treating ARDS and other pulmonary diseases that are caused by barrier dysfunction