NOX4-TIM23 interaction regulates NOX4 mitochondrial import and metabolic reprogramming

Our plain-English summary of NOX4-TIM23 interaction regulates NOX4 mitochondrial import and metabolic reprogramming, by J. Pandey, J.L. Larson-Casey, M.H. Patil, et al (The Journal of Biological Chemistry, 2023).

The study

• Authors: J. Pandey, J.L. Larson-Casey, M.H. Patil, R. Joshi, C.S. Jiang, Y. Zhou, C. He, A.B. Carter
• Journal: The Journal of Biological Chemistry
• Published: 2023;299(5):104695
• Cited by: 9 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Pulmonary fibrosis is a progressive lung disease characterized by macrophage activation. Asbestos-induced expression of nicotinamide adenine dinucleotide phosphate hydrogen oxidase 4 (NOX4) in lung macrophages mediates fibrotic progression by the generation of mitochondrial reactive oxygen species (ROS), modulating mitochondrial biogenesis, and promoting apoptosis resistance; however, the mechanism(s) by which NOX4 localizes to mitochondria during fibrosis is not known. Here, we show that NOX4 localized to the mitochondrial matrix following asbestos exposure in lung macrophages via direct interaction with TIM23. TIM23 and NOX4 interaction was found in lung macrophages from human subjects with asbestosis, while it was absent in mice harboring a conditional deletion of NOX4 in lung macrophages. This interaction was localized to the proximal transmembrane region of NOX4. Mechanistically, TIM23 augmented NOX4-induced mitochondrial ROS and metabolic reprogramming to oxidative phosphorylation. Silencing TIM23 decreased mitochondrial ROS and oxidative phosphorylation. These observations highlight the important role of the mitochondrial translocase TIM23 interaction with NOX4. Moreover, this interaction is required for mitochondrial redox signaling and metabolic reprogramming in lung macrophages.

Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.

In plain English

This laboratory study examined how NOX4, an enzyme that produces reactive oxygen species, gets into the mitochondria of lung immune cells called macrophages after asbestos exposure. The authors used three sources: cultured macrophage cell lines exposed to asbestos; mice given chrysotile asbestos or a man-made vitreous fiber (MMVF) control into the airway, including mice lacking NOX4 in macrophages; and lung-wash macrophages from people with asbestosis and from healthy volunteers. In cultured cells, NOX4 was found in the innermost compartment of the mitochondria (the matrix). Switching off a mitochondrial import protein, TIM23, reduced NOX4 in mitochondria. NOX4 and TIM23 bound to each other in mitochondria from asbestos-exposed mouse macrophages but not in mice lacking NOX4. The binding appeared to need the part of NOX4 between amino acids 213 and 447. The amount of TIM23 bound to NOX4 was significantly higher in macrophages from asbestosis subjects than from normal subjects (n = 3, p less than 0.05). Silencing TIM23 reduced asbestos-induced mitochondrial oxidants and oxygen consumption. The authors concluded that this interaction is crucial for NOX4's function and may be a druggable target for asbestosis.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory study combining cell-culture experiments, a mouse experiment (including mice with macrophage-specific deletion of Nox4), and analysis of lung-wash (BAL) macrophages from human subjects
• Who was studied: Mouse alveolar macrophage and human monocyte (THP-1) cell lines; male and female mice aged 6 to 12 weeks (Nox4 fl/fl controls and Nox4−/−Lyz2-cre mice); BAL macrophages from normal and asbestosis subjects at UAB and the Birmingham VAMC (the human comparison figure reports n = 3). The total number of mice and human subjects is not stated.
• Exposure: Mice: a single airway dose of 100 μg chrysotile asbestos or man-made vitreous fiber (MMVF) as control, examined at day 21. Cultured cells: 10 μg/cm2 asbestos (fiber type not specified for the in vitro work). Human asbestosis subjects were required to have occupational or environmental asbestos exposure.
• Main results:
  • In asbestos-exposed cultured macrophages, NOX4 was not found in the mitochondrial intermembrane space or inner membrane, but was found in the matrix.
  • In cultured macrophages, silencing TIM23 significantly reduced NOX4 in the mitochondria. Silencing MIA40 or TIM22 did not have this effect.
  • In cultured macrophages, NOX4 was highly correlated (colocalized) with TIM23 with asbestos exposure (Pearson's r = 0.849) and with NOX4 overexpression (r = 0.884 and r = 0.897).
  • In macrophages from asbestos-exposed Nox4 fl/fl mice, NOX4 was highly correlated with TIM23 (Pearson's r = 0.919).
  • The NOX4–TIM23 interaction was found in mitochondria from asbestos-injured Nox4 fl/fl mice but was not present in macrophage mitochondria from Nox4−/−Lyz2-cre mice.
  • Using shortened versions of NOX4, TIM23 bound only full-length NOX4 and the 447-amino-acid version. The authors suggested that amino acids 213 to 447 are required for binding.
  • In human BAL macrophages, TIM23 bound to NOX4 was significantly increased in asbestosis subjects compared with healthy normal subjects (figure reports n = 3, t test p less than 0.05).
  • In cultured macrophages, silencing TIM23 significantly reduced asbestos-induced mitochondrial superoxide and hydrogen peroxide production.
  • Asbestos increased the oxygen consumption rate in control cultured macrophages, and this was significantly reduced when TIM23 was silenced.
  • Oxygen consumption was significantly increased in lung macrophages from asbestos-exposed Nox4 fl/fl mice. In Nox4−/−Lyz2-Cre mice exposed to MMVF or asbestos for 21 days it stayed at the MMVF control level.
• The authors' conclusion: The authors concluded that the direct interaction of TIM23 and NOX4 is crucial for the function of NOX4, and suggested that this interaction may be a druggable target for asbestosis and other fibrotic lung diseases.

Topics

Medical terms in this study, explained in our Lexicon: Pulmonary Fibrosis, Macrophage, Reactive Oxygen Species (ROS), Apoptosis, Fibrosis, Asbestos Exposure.

Related studies

• NOX4 modulates macrophage phenotype and mitochondrial biogenesis in asbestosis — C. He, J.L. Larson-Casey, et al. (2019)
• NOX4 regulates macrophage apoptosis resistance to induce fibrotic progression — J.L. Larson-Casey, L. Gu, et al. (2021)
• Mitochondrial Rac1 GTPase import and electron transfer from cytochrome c are required for pulmonary fibrosis — H.L. Osborn-Heaford, A.J. Ryan, et al. (2012)
• Peroxiredoxin 3 levels regulate a mitochondrial redox setpoint in malignant mesothelioma cells — B. Cunniff, A.N. Wozniak, et al. (2014)
• Mitochondrial catalase overexpressed transgenic mice are protected against lung fibrosis in part via preventing alveolar epithelial cell mitochondrial DNA damage — S.J. Kim, P. Cheresh, et al. (2016)
• Tumour suppressor Fus1 provides a molecular link between inflammatory response and mitochondrial homeostasis — R. Uzhachenko, N. Issaeva, et al. (2012)

Browse more research in The Journal of Biological Chemistry, or return to medical research.