ER Oxidative Stress Promotes Glutathione-Dependent Oxidation of Collagen-1A1 and Promotes Lung Fibroblast Activation.

Changes in the oxidative (redox) environment accompany idiopathic pulmonary fibrosis (IPF). S-glutathionylation of reactive protein cysteines is a post-translational event that transduces oxidant signals into biological responses. We recently demonstrated that increases in S-glutathionylation promote pulmonary fibrosis, which was mitigated by the deglutathionylating enzyme glutaredoxin (GLRX). However, the protein targets of S-glutathionylation that promote fibrogenesis remain unknown. In the present study we addressed whether the extracellular matrix is a target for S-glutathionylation. We discovered increases in collagen 1A1 S-glutathionylation (COL1A1-SSG) in lung tissues from IPF subjects compared to control subjects in association with increases in ER oxidoreductin 1 (ERO1A) and enhanced oxidation of ER-localized peroxiredoxin 4 (PRDX4) reflecting an increased oxidative environment of the endoplasmic reticulum (ER). Human lung fibroblasts exposed to transforming growth factor beta 1 (TGFB1) show increased secretion of COL1A1-SSG. Pharmacologic inhibition of ERO1A diminished oxidation of PRDX4, attenuated COL1A1-SSG and total COL1A1 levels and dampened fibroblast activation. Absence of Glrx enhanced COL1A1-SSG and overall COL1A1 secretion and promoted activation of mechanosensing pathways. Remarkably, COL1A1-SSG resulted in marked resistance to collagenase degradation. Compared to COL1, lung fibroblasts plated on COL1-SSG proliferated more rapidly, and increased expression of genes encoding extracellular matrix crosslinking enzymes and genes linked to mechanosensing pathways. Overall, these findings suggest that glutathione-dependent oxidation of COL1A1 occurs in settings of IPF in association with enhanced ER oxidative stress and may promote fibrotic remodeling due to increased resistance to collagenase-mediated degradation and fibroblast activation.

The glutathione S-transferase Gstt1 drives survival and dissemination in metastases.

Identifying the adaptive mechanisms of metastatic cancer cells remains an elusive question in the treatment of metastatic disease, particularly in pancreatic cancer (pancreatic adenocarcinoma, PDA). A loss-of-function shRNA targeted screen in metastatic-derived cells identified Gstt1, a member of the glutathione S-transferase superfamily, as uniquely required for dissemination and metastasis, but dispensable for primary tumour growth. Gstt1 is expressed in latent disseminated tumour cells (DTCs), is retained within a subpopulation of slow-cycling cells within existing metastases, and its inhibition leads to complete regression of macrometastatic tumours. This distinct Gstt1high population is highly metastatic and retains slow-cycling phenotypes, epithelial-mesenchymal transition features and DTC characteristics compared to the Gstt1low population. Mechanistic studies indicate that in this subset of cancer cells, Gstt1 maintains metastases by binding and glutathione-modifying intracellular fibronectin, in turn promoting its secretion and deposition into the metastatic microenvironment. We identified Gstt1 as a mediator of metastasis, highlighting the importance of heterogeneity and its influence on the metastatic tumour microenvironment.