Jonathan M. Weiss

The Chloride Intracellular Channel-4 (CLIC4) is one of six highly conserved proteins in the CLIC family that share high structural homology with glutathione-S-transferase (GST)-omega in the GST superfamily. While CLIC4 is a multifunctional protein that resides in multiple cellular compartments, the discovery of its enzymatic glutaredoxin-like activity in vitro suggested that it could be one of the essential oxidoreductases in cells. Here we show that macrophages lacking Clic4 display a variety of phenotypes including a failure to sustain cytokine production and reduced phagocytosis suggesting a role for Clic4 in metabolic fitness. Null cells have elevated levels of ROS as well as defective cellular energetics and reduced ATP levels. Mechanistically we find that stimulated Clic4 null cells have exacerbated expression of the negative regulator of mitochondrial ROS, UCP2. Accordingly, inhibition of UCP2 restores macrophage energetics and phagocytic activity in vitro and in vivo. We propose a model where Clic4 restrains UCP2 expression by dampening cellular ROS levels thereby preserving the mitochondrial function necessary for highly energetic activities including sustained cytokine production and phagocytosis. Our findings raise the possibility of targeting CLIC4 to induce macrophage hypophagia as a mechanism of innate immune exhaustion to improve some essential therapeutic outcomes for inflammatory diseases and related cancers.

Emboli formation by different breast cancer cell lines

Proteomic and metabolic analysis

Treatment of cells in 3D with metabolic pathway inhibitors

Morphometric data of electron microscopy images

Ultrastructural analysis of SUM149 mitochondria, nuclei and lipid droplets

Supplementary File 4 from 3D “Emboli” Culture Models Epithelial Breast Cancer Cell Oxidative Mitochondrial Metabolism with Relevance for Lung Metastasis

Single cell mRNA sequencing data of cells from 2D, SphC, and EmC