Biology subjects

Backes, B. J.

Publications and source records attributed to Backes, B. J..

4 recordsLinked to original sources

bioRxiv2021

IRE1α drives lung epithelial progenitor dysfunction to establish a niche for pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a disease of progressive interstitial fibrosis, which leads to severe debilitation, respiratory failure, and death. In IPF, environmental exposures interact with genetic risk factors to engender critical patho-etiological events in lung epithelial cells, including endoplasmic reticulum (ER) stress and TGF{beta} signaling, but the interactions between these disparate pathways are not well understood. We previously showed that kinase inhibitors of the IRE1 bifunctional kinase/RNase--a central mediator of the unfolded protein response (UPR) to ER stress--protected mice from bleomycin-induced pulmonary fibrosis. Here we show that a nanomolar-potent, mono-selective kinase inhibitor of IRE1 (KIRA8) decreases ER-stress induced TGF{beta} signaling and the senescence-associated secretory phenotype (SASP) in the lung epithelium after bleomycin exposure. A recently-described subset of "damage-associated transient progenitors" (DATPs) display IRE1-regulated pathological gene signatures that are quelled by KIRA8, in vivo. After injury, these cells uniquely express integrin v{beta}6, a key activator of TGF{beta} in pulmonary fibrosis. KIRA8 inhibition of IRE1 decreases both DATP number and Itgb6 expression in remaining cells, with a decrease in local collagen accumulation. Single-cell RNA sequencing from IPF lungs revealed an analogous Itgb6+ cell population that may also be regulated by IRE1. These findings suggest that lung epithelial progenitor cells sit at the center of the fibrotic niche, and IRE1 signaling locks them into a dysfunctional state that establishes and perpetuates pathological fibrosis.

cell biology↗

bioRxiv2020

A defect in COPI-mediated transport of STING causes immune dysregulation in COPA syndrome

Pathogenic COPA variants cause a Mendelian syndrome of immune dysregulation with elevated type I interferon signaling1,2. COPA is a subunit of coat protein complex I (COPI) that mediates Golgi to ER transport3. Missense mutations that disrupt the COPA WD40 domain impair binding and sorting of proteins targeted for retrieval to the ER but how this causes disease remains unknown1,4. Given the importance of COPA in Golgi-ER transport, we speculated that type I interferon signaling in COPA syndrome involves missorting of STING. Here we show that a defect in COPI transport due to mutant COPA causes ligand-independent activation of STING. Furthermore, SURF4 is an adapter molecule that facilitates COPA-mediated retrieval of STING at the Golgi. Activated STING stimulates type I interferon driven inflammation in CopaE241K/+ mice that is rescued in STING-deficient animals. Our results demonstrate that COPA maintains immune homeostasis by regulating STING transport at the Golgi. In addtion, activated STING contributes to immune dysregulation in COPA syndrome and may be a new molecular target in treating the disease.

immunology↗

bioRxiv2019

Parallel signaling through IRE1α and PERK regulates pancreatic neuroendocrine tumor growth and survival

Master regulators of the unfolded protein response (UPR)--IRE1 and PERK-- promote adaptation or apoptosis depending on levels of endoplasmic reticulum (ER) stress. While the UPR is activated in many cancers, its effects on tumor growth remain unclear. Derived from endocrine cells, pancreatic neuroendocrine tumors (PanNETs) universally hypersecrete one or more peptide hormones, likely sensitizing these cells to high ER protein-folding stress. For the nearly 1,500 Americans diagnosed with PanNETs annually, surgery is the only potentially curative treatment; however the five-year survival is extremely low for those who develop metastatic disease. To assess whether targeting the UPR is a viable therapeutic strategy, we analyzed human PanNET samples and found evidence of elevated ER stress and UPR activation. We then used genetic and pharmacologic approaches to modulate IRE1 and PERK in cultured cells and xenograft and spontaneous genetic (RIP-Tag2) mouse models of PanNETs. We found that UPR signaling is optimized for adaptation and that inhibiting either IRE1 or PERK leads to hyperactivation and apoptotic signaling through the reciprocal arm, thereby halting tumor growth and survival. Our results provide a strong rationale for therapeutically targeting the UPR in PanNETs and other cancers experiencing elevated ER stress.\n\nSignificanceThe unfolded protein response (UPR) is upregulated in human pancreatic neuroendocrine tumors and its genetic or pharmacological inhibition significantly reduces tumor growth in preclinical models, providing strong rationale for targeting the UPR in neoplasms with elevated ER stress.

cancer biology↗

bioRxiv2018

Small molecule inhibition of IRE1α kinase/RNase has anti-fibrotic effects in the lung

Endoplasmic reticulum stress (ER stress) has been implicated in the pathogenesis of idiopathic pulmonary fibrosis (IPF), a disease of progressive fibrosis and respiratory failure. ER stress activates a signaling pathway called the unfolded protein response (UPR) that either restores homeostasis or promotes apoptosis. The bifunctional kinase/RNase IRE1 is a UPR sensor that promotes apoptosis if ER stress remains high (i.e., a \"terminal\" UPR). Using multiple small molecule inhibitors against IRE1, we show that ER stress-induced apoptosis of murine alveolar epithelial cells can be mitigated in vitro. In vivo, we show that bleomycin exposure to murine lungs causes early ER stress to activate IRE1 and the terminal UPR prior to development of pulmonary fibrosis. Small-molecule IRE1 kinase-inhibiting RNase attenuators (KIRAs) that we developed were used to evaluate the importance of IRE1 activation in bleomycin-induced pulmonary fibrosis. One such KIRA--KIRA7--provided systemically to mice at the time of bleomycin exposure decreases terminal UPR signaling and prevents lung fibrosis. Administration of KIRA7 14 days after bleomycin exposure even promoted the reversal of established fibrosis. Finally, we show that KIRA8, a nanomolar-potent, monoselective KIRA compound derived from a completely different scaffold than KIRA7, likewise promoted reversal of established fibrosis. These results demonstrate that IRE1 may be a promising target in pulmonary fibrosis and that kinase inhibitors of IRE1 may eventually be developed into efficacious anti-fibrotic drugs.

molecular biology↗