MST1 and idiopathic pulmonary fibrosis: The concept that altered tight junction activates YAP in AECs, combined with increased matrix stiffness associated with increased collagen deposition induces YAP in fibroblasts, and MST1/2-the inhibitors of YAP nuclear localization are decreased in IPF AECs cells, indicates a system in which YAP/TAZ is aberrantly activated in both the epithelium and mesenchyme.