Article ; Online: Cell death induced by the ER stressor thapsigargin involves death receptor 5, a non-autophagic function of MAP1LC3B, and distinct contributions from unfolded protein response components.
Cell communication and signaling : CCS
2020 Volume 18, Issue 1, Page(s) 12
Abstract: Background: Cell death triggered by unmitigated endoplasmic reticulum (ER) stress plays an important role in physiology and disease, but the death-inducing signaling mechanisms are incompletely understood. To gain more insight into these mechanisms, the ...
| Abstract | Background: Cell death triggered by unmitigated endoplasmic reticulum (ER) stress plays an important role in physiology and disease, but the death-inducing signaling mechanisms are incompletely understood. To gain more insight into these mechanisms, the ER stressor thapsigargin (Tg) is an instrumental experimental tool. Additionally, Tg forms the basis for analog prodrugs designed for cell killing in targeted cancer therapy. Tg induces apoptosis via the unfolded protein response (UPR), but how apoptosis is initiated, and how individual effects of the various UPR components are integrated, is unclear. Furthermore, the role of autophagy and autophagy-related (ATG) proteins remains elusive. Methods: To systematically address these key questions, we analyzed the effects of Tg and therapeutically relevant Tg analogs in two human cancer cell lines of different origin (LNCaP prostate- and HCT116 colon cancer cells), using RNAi and inhibitory drugs to target death receptors, UPR components and ATG proteins, in combination with measurements of cell death by fluorescence imaging and propidium iodide staining, as well as real-time RT-PCR and western blotting to monitor caspase activity, expression of ATG proteins, UPR components, and downstream ER stress signaling. Results: In both cell lines, Tg-induced cell death depended on death receptor 5 and caspase-8. Optimal cytotoxicity involved a non-autophagic function of MAP1LC3B upstream of procaspase-8 cleavage. PERK, ATF4 and CHOP were required for Tg-induced cell death, but surprisingly acted in parallel rather than as a linear pathway; ATF4 and CHOP were independently required for Tg-mediated upregulation of death receptor 5 and MAP1LC3B proteins, whereas PERK acted via other pathways. Interestingly, IRE1 contributed to Tg-induced cell death in a cell type-specific manner. This was linked to an XBP1-dependent activation of c-Jun N-terminal kinase, which was pro-apoptotic in LNCaP but not HCT116 cells. Molecular requirements for cell death induction by therapy-relevant Tg analogs were identical to those observed with Tg. Conclusions: Together, our results provide a new, integrated understanding of UPR signaling mechanisms and downstream mediators that induce cell death upon Tg-triggered, unmitigated ER stress. Video Abstract. |
|---|---|
| MeSH term(s) | Activating Transcription Factor 4/genetics ; Activating Transcription Factor 4/metabolism ; Autophagy ; Caspase 8/genetics ; Caspase 8/metabolism ; Cell Line, Tumor ; Endoplasmic Reticulum/genetics ; Endoplasmic Reticulum/metabolism ; Endoplasmic Reticulum Stress ; Humans ; JNK Mitogen-Activated Protein Kinases/genetics ; JNK Mitogen-Activated Protein Kinases/metabolism ; Microtubule-Associated Proteins/genetics ; Microtubule-Associated Proteins/metabolism ; Receptors, TNF-Related Apoptosis-Inducing Ligand/genetics ; Receptors, TNF-Related Apoptosis-Inducing Ligand/metabolism ; Thapsigargin/metabolism ; Unfolded Protein Response ; X-Box Binding Protein 1/genetics ; X-Box Binding Protein 1/metabolism |
| Chemical Substances | ATF4 protein, human ; MAP1LC3B protein, human ; Microtubule-Associated Proteins ; Receptors, TNF-Related Apoptosis-Inducing Ligand ; X-Box Binding Protein 1 ; XBP1 protein, human ; Activating Transcription Factor 4 (145891-90-3) ; Thapsigargin (67526-95-8) ; JNK Mitogen-Activated Protein Kinases (EC 2.7.11.24) ; Caspase 8 (EC 3.4.22.-) |
| Language | English |
| Publishing date | 2020-01-27 |
| Publishing country | England |
| Document type | Journal Article |
| ZDB-ID | 2126315-2 |
| ISSN | 1478-811X ; 1478-811X |
| ISSN (online) | 1478-811X |
| ISSN | 1478-811X |
| DOI | 10.1186/s12964-019-0499-z |
| Database | MEDical Literature Analysis and Retrieval System OnLINE |
More links
Kategorien
Order via subito
This service is chargeable due to the Delivery terms set by subito. Orders including an article and supplementary material will be classified as separate orders. In these cases, fees will be demanded for each order.