Biology subjects

chevet, e.

Publications and source records attributed to chevet, e..

5 recordsLinked to original sources

bioRxiv2024

Proximity Interactome analyses unveil novel regulators of IRE1a canonical signaling

The unfolded protein response (UPR) is a key adaptive pathway that controls endoplasmic reticulum (ER) homeostasis. The UPR is transduced by three ER-resident sensors of ER homeostasis disruption in the lumen of this compartment. They trigger select downstream signaling pathways in the cytosol and nucleus. Among them, IRE1 (referred to as IRE1 hereafter), a type I transmembrane protein, senses accumulation of improperly folded proteins in the ER lumen and transduces signals through both kinase and endoribonuclease (RNase) activities in the cytosol. IRE1 catalyzes XBP1 mRNA unconventional splicing and RNA degradation (Regulated IRE1 Dependent Decay, termed RIDD). Recent studies have reported that IRE1-dependent protein-protein interactions (PPi) drive additional non-canonical IRE1 functions. Herein, we define the IRE1 signalosome as a list of IRE1 binding partners (direct or not) which alter IRE1 signaling towards XBP1 mRNA splicing and RIDD. Here we determined the IRE1 in situ interactome using BioID, putatively connecting IRE1 to previously unrecognized cellular functions. In addition, we link the binding of several IRE1 partners to the regulation of its RNase. Furthermore, we identify HNRNPL as an IRE1-interacting partner, previously unrecognized, which stabilizes IRE1 under basal conditions by counteracting ERAD-mediated degradation. Overall, the characterization of the IRE1 signalosome not only reveals the multi-faceted control of IRE1 RNase activity and stability by its interacting partners and allow us to discuss putative additional IRE1 regulators and cellular functions based on the nature of its interactome and its localization.

biochemistry↗

bioRxiv2022

IRE1 RNase controls CD95-mediated cell death

Signalling by the Unfolded Protein Response (UPR) or by the Death Receptors (DR) represents cellular stress pathways frequently activated towards pro-tumoral outputs in cancer. Experimental evidence has highlighted functional links between the UPR and the DR TRAIL-R1/2. Herein, we demonstrate that the UPR sensor IRE1 controls the expression of CD95/Fas, another DR, and its cell death-inducing ability. Whereas CD95 is not a general determinant of ER stress-induced cell death, IRE1 RNase activity inhibition increased CD95 expression and exacerbated CD95L-induced cell death in glioblastoma (GB) and Triple-Negative Breast Cancer (TNBC) cell lines. In accordance, CD95 mRNA was identified as a target of Regulated IRE1-Dependent Decay of RNA (RIDD). Moreover, CD95 expression is elevated in TNBC and GB human tumours exhibiting low RIDD activity. Surprisingly, CD95 expression is also lower in XBP1s-low human tumour samples. We show that IRE1 RNase inhibition led to CD95 expression attenuation and reduced CD95-mediated hepatic toxicity in mice. In addition, overexpression of XBP1s increased CD95 expression and sensitized GB and TNBC cells to CD95L-induced cell death. Overall, these results demonstrate the tight IRE1-mediated control of CD95-dependent cell death signals in a dual manner through both RIDD and XBP1s, and they identify a novel, pharmacologically actionable link between IRE1 and CD95 signalling.

cell biology↗

bioRxiv2020

Stress-induced tyrosine phosphorylation of RtcB modulates IRE1 activity and signaling outputs.

Endoplasmic Reticulum (ER) stress is a hallmark of various diseases, which is dealt with through the activation of an adaptive signaling pathway named the Unfolded Protein Response (UPR). This response is mediated by three ER-resident sensors and the most evolutionary conserved, IRE1 signals through its cytosolic kinase and endoribonuclease (RNase) activities. IRE1 RNase activity can either catalyze the initial step of XBP1 mRNA unconventional splicing or degrade a number of RNAs through Regulated IRE1- Dependent Decay (RIDD). The balance between these two activities plays an instrumental role in cells life and death decisions upon ER stress. Until now, the biochemical and biological outputs of IRE1 RNase activity have been well documented, however, the precise mechanisms controlling whether IRE1 signaling is adaptive or pro-death (terminal) remain unclear. This prompted us to further investigate those mechanisms and we hypothesized that XBP1 mRNA splicing and RIDD activity could be co-regulated by the IRE1 RNase regulatory network. We showed that a key nexus in this pathway is the tRNA ligase RtcB which, together with IRE1, is responsible for XBP1 mRNA splicing. We demonstrated that RtcB is tyrosine phosphorylated by c-Abl and dephosphorylated by PTP1B. Moreover, we identified RtcB Y306 as a key residue which, when phosphorylated, perturbs RtcB interaction with IRE1, thereby attenuating XBP1 mRNA splicing and favoring RIDD. Our results demonstrate that the IRE1 RNase regulatory network is dynamically fine-tuned by tyrosine kinases and phosphatases upon various stresses and that the nature of the stress determines cell adaptive or death outputs.

biochemistry↗

bioRxiv2019

Development of a novel preclinical glioblastoma mouse model and therapeutic impact of IRE1 inhibition

Glioblastoma multiforme (GBM) is the most severe primary brain cancer. Despite an aggressive treatment comprising surgical resection and radio/chemotherapy patients survival post diagnosis remains short. A limitation for success in finding novel improved therapeutic options for such dismal disease partly lies in the lack of a relevant animal model that accurately recapitulates patient disease and standard of care. In the present study, we have developed a novel immunocompetent GBM model that includes tumor surgery and a radio/chemotherapy regimen resembling the Stupp protocol and we have used this model to test the impact of the pharmacological inhibition of the endoplasmic reticulum (ER) stress sensor IRE1, on treatment efficacy.

cancer biology↗

bioRxiv2019

IRE1-UBE2D3 signaling controls the recruitment of myeloid cells to glioblastoma.

Tumor cells are exposed to intrinsic and environmental challenges that trigger endoplasmic reticulum (ER) homeostasis alteration, in turn leading to ER stress. To cope with this, tumor cells engage an adaptive signaling pathway, the unfolded protein response (UPR) thus promoting the acquisition of malignant features. As such, glioblastoma multiforme (GBM), the most aggressive primary brain tumors, exhibit constitutive UPR signals to sustain growth. Herein, we showed that signaling elicited by one of the UPR sensors, IRE1, promotes GBM tumor invasion, angiogenesis and infiltration by macrophages. Hence, high IRE1 activity in tumors predicts worse outcome. We further dissect IRE1-dependent mechanisms that shape the brain tumor immune microenvironment towards myeloid cells. We identify an IRE1-dependent signaling pathway that directly controls the expression/release of proinflammatory chemokines (CXCL2, IL6, IL8) leading to tumor cell-mediated chemoattraction of neutrophils and macrophages. This pathway requires XBP1 non-conventional mRNA splicing and XBP1s-dependent expression of the E2 ubiquitin enzyme UBE2D3. The latter contributes to the degradation of the NF{kappa}B inhibitor I{kappa}B, leading to the up-regulation of proinflammatory chemokines. Our work identifies a novel IRE1/UBE2D3 proinflammatory signaling axis instrumental to pro-tumoral immune regulation of GBM.

cancer biology↗