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National Institute of Environmental Health Sciences

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Your Environment. Your Health.

Publication Detail

Title: A Novel Interaction of Translocator Protein 18 kDa (TSPO) with NADPH Oxidase in Microglia.

Authors: Loth, Meredith K; Guariglia, Sara R; Re, Diane B; Perez, Juan; de Paiva, Vanessa Nunes; Dziedzic, Jennifer L; Chambers, Jeremy W; Azzam, Diana J; Guilarte, Tomás R

Published In Mol Neurobiol, (2020 Nov)

Abstract: In the brain neuropil, translocator protein 18 kDa (TSPO) is a stress response protein that is upregulated in microglia and astrocytes in diverse central nervous system pathologies. TSPO is widely used as a biomarker of neuroinflammation in preclinical and clinical neuroimaging studies. However, there is a paucity of knowledge on the function(s) of TSPO in glial cells. In this study, we explored a putative interaction between TSPO and NADPH oxidase 2 (NOX2) in microglia. We found that TSPO associates with gp91phox and p22phox, the principal subunits of NOX2 in primary murine microglia. The association of TSPO with gp91phox and p22phox was observed using co-immunoprecipitation, confocal immunofluorescence imaging, and proximity ligation assay. We found that besides gp91phox and p22phox, voltage-dependent anion channel (VDAC) also co-immunoprecipitated with TSPO consistent with previous reports. When we compared lipopolysaccharide (LPS) stimulated microglia to vehicle control, we found that a lower amount of gp91phox and p22phox protein co-immunoprecipitated with TSPO suggesting a disruption of the TSPO-NOX2 subunits association. TSPO immuno-gold electron microscopy confirmed that TSPO is present in the outer mitochondrial membrane but it is also found in the endoplasmic reticulum (ER), mitochondria-associated ER membrane (MAM), and in the plasma membrane. TSPO localization at the MAM may represent a subcellular site where TSPO interacts with gp91phox and p22phox since the MAM is a point of communication between outer mitochondria membrane proteins (TSPO) and ER proteins (gp91phox and p22phox) where they mature and form the cytochrome b558 (Cytb558) heterodimer. We also found that an acute burst of reactive oxygen species (ROS) increased TSPO levels on the surface of microglia and this effect was abrogated by a ROS scavenger. These results suggest that ROS production may alter the subcellular distribution of TSPO. Collectively, our findings suggest that in microglia, TSPO is associated with the major NOX2 subunits gp91phox and p22phox. We hypothesize that this interaction may regulate Cytb558 formation and modulate NOX2 levels, ROS production, and redox homeostasis in microglia.

PubMed ID: 32743737 Exiting the NIEHS site

MeSH Terms: Animals; Cytosol/metabolism; Endoplasmic Reticulum/metabolism; Female; HEK293 Cells; Heme/metabolism; Humans; Intracellular Membranes/metabolism; Mice, Inbred C57BL; Mice, Transgenic; Microglia/metabolism*; Microglia/ultrastructure; Mitochondria/metabolism; Models, Biological; NADPH Oxidases/metabolism*; Porphyrins/metabolism; Protein Binding; Reactive Oxygen Species/metabolism; Receptors, GABA/chemistry; Receptors, GABA/metabolism*; Voltage-Dependent Anion Channels/metabolism

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