Immunohistochemical evidence for the association between attenuated mTOR signaling and diffuse alveolar damage, a fatal lung complication

Identification of a protein expression signature distinguishing early from organising diffuse alveolar damage in COVID-19 patients

Diffuse alveolar damage (DAD) is the histological expression of acute respiratory distress syndrome and characterises lung pathology due to infection with SARS-CoV-2, and other respiratory pathogens of clinical significance. DAD reflects a time-dependent immunopathological process, progressing from an early/exudative stage through to an organising/fibrotic stage, yet within an individual these different stages of DAD may coexist. Understanding the progression of DAD is central to the development of new therapeutics to limit progressive lung damage. Here, we applied highly multiplexed spatial protein profiling to autopsy lung tissues derived from 27 patients who died from COVID-19 and identified a protein signature (ARG1, CD127, GZMB, IDO1, Ki67, phospho-PRAS40 (T246) and VISTA) that distinguishes early DAD from late DAD with good predictive accuracy. These proteins warrant further investigation as potential regulators of DAD progression.

Lysosomal Protein Lamtor1 Controls Innate Immune Responses via Nuclear Translocation of Transcription Factor EB

Amino acid metabolism plays important roles in innate immune cells, including macrophages. Recently, we reported that a lysosomal adaptor protein, Lamtor1, which serves as the scaffold for amino acid-activated mechanistic target of rapamycin complex 1 (mTORC1), is critical for the polarization of M2 macrophages. However, little is known about how Lamtor1 affects the inflammatory responses that are triggered by the stimuli for TLRs. In this article, we show that Lamtor1 controls innate immune responses by regulating the phosphorylation and nuclear translocation of transcription factor EB (TFEB), which has been known as the master regulator for lysosome and autophagosome biogenesis. Furthermore, we show that nuclear translocation of TFEB occurs in alveolar macrophages of myeloid-specific Lamtor1 conditional knockout mice and that these mice are hypersensitive to intratracheal administration of LPS and bleomycin. Our observation clarified that the amino acid-sensing pathway consisting of Lamtor1, mTORC1, and TFEB is involved in the regulation of innate immune responses.

Mammalian Target of Rapamycin: A Target for (Lung) Diseases and Aging

The mammalian target of rapamycin (mTOR) signaling pathway has been studied in the context of an impressive number of biological processes and disease states, including major diseases of the lung such as idiopathic pulmonary fibrosis and chronic obstructive pulmonary disease, as well as the rare condition lymphangioleiomyomatosis. The involvement of mTOR in so many disease states (in and out of the lung) raises the question how one signaling pathway can have overlapping but diverse roles seemingly everywhere. Findings in the last decade have placed the mTOR pathway in a new context as an important, conserved mediator of the aging process. This offers one explanation for the pleiotropic effects of mTOR: -that many chronic diseases are also diseases of aging and that pathways modulating aging will have widespread effects on associated disease. However, this may not be the entire story, because mTOR is also implicated in a large number of diseases not linked to aging. In this article, we discuss the current state of knowledge regarding mTOR, especially in the context of lung pathologies, and offer a potential explanation for its widespread involvement in human disease.