Context-Dependent Roles of Mitochondrial LONP1 in Orchestrating the Balance between Airway Progenitor versus Progeny Cells
While all eukaryotic cells are dependent on mitochondria for function, in a complex tissue, which cell type and which cell behavior are more sensitive to mitochondrial deficiency remains unpredictable. Here we show that in the mouse airway, compromising mitochondrial function by inactivating mitochondrial protease gene Lonp1 led to reduced progenitor proliferation and differentiation during development; apoptosis of terminally differentiated ciliated cells and their replacement by basal progenitors and goblet cells during homeostasis; and failed airway progenitor migration into damaged alveoli following influenza infection. ATF4 and the integrated stress response (ISR) pathway are elevated and responsible for airway phenotypes. Such context dependent sensitivities are predicted by the selective expression of Bok, which is required for ISR activation. Reduced LONP1 expression is found in chronic obstructive pulmonary disease (COPD) airways with squamous metaplasia. These findings illustrate a cellular energy landscape whereby compromised mitochondrial function could favor the emergence of pathological cell types. Overall design: Bulk RNA-seq from embryonic lungs at E13.5, including 3 controls and 4 Shhcre;Lonp1 mutants.  Single cell RNA-seq from purified adult airway epithelial cells of control and Sox2creER;Lonp1;tdTomato. scRNA-seq from control (PBS) and influenza infected lungs at D11 and D20.