bims-unfpre 2019-08-18 papers

Issue of 2019–08–18
four papers selected by
Susan Logue, University of Manitoba

Proc Natl Acad Sci U S A. 2019 Aug 14. pii: 201900055. [Epub ahead of print]

Dietary restriction improves proteostasis and increases life span through endoplasmic reticulum hormesis.

Latika Matai, Gautam Chandra Sarkar, Manish Chamoli, Yasir Malik, Shashi Shekhar Kumar, Umanshi Rautela, Nihar Ranjan Jana, Kausik Chakraborty, Arnab Mukhopadhyay.

Unfolded protein response (UPR) of the endoplasmic reticulum (UPRER) helps maintain proteostasis in the cell. The ability to mount an effective UPRER to external stress (iUPRER) decreases with age and is linked to the pathophysiology of multiple age-related disorders. Here, we show that a transient pharmacological ER stress, imposed early in development on Caenorhabditis elegans, enhances proteostasis, prevents iUPRER decline with age, and increases adult life span. Importantly, dietary restriction (DR), that has a conserved positive effect on life span, employs this mechanism of ER hormesis for longevity assurance. We found that only the IRE-1-XBP-1 branch of UPRER is required for the longevity effects, resulting in increased ER-associated degradation (ERAD) gene expression and degradation of ER resident proteins during DR. Further, both ER hormesis and DR protect against polyglutamine aggregation in an IRE-1-dependent manner. We show that the DR-specific FOXA transcription factor PHA-4 transcriptionally regulates the genes required for ER homeostasis and is required for ER preconditioning-induced life span extension. Finally, we show that ER hormesis improves proteostasis and viability in a mammalian cellular model of neurodegenerative disease. Together, our study identifies a mechanism by which DR offers its benefits and opens the possibility of using ER-targeted pharmacological interventions to mimic the prolongevity effects of DR.

Keywords: aging; dietary restriction; endoplasmic reticulum; hormesis; life span

DOI: https://doi.org/10.1073/pnas.1900055116

Cell Death Dis. 2019 Aug 16. 10(9): 622

Inhibition of IRE1α RNase activity reduces NLRP3 inflammasome assembly and processing of pro-IL1β.

Aaron Talty, Shane Deegan, Mila Ljujic, Katarzyna Mnich, Serika D Naicker, Dagmar Quandt, Qingping Zeng, John B Patterson, Adrienne M Gorman, Matthew D Griffin, Afshin Samali, Susan E Logue.

The inflammasome is a multiprotein complex assembled in response to Pathogen Associated Molecular Patterns (PAMPs) and Danger Associated Molecular Patterns (DAMPs). Inflammasome activation occurs through a two-step mechanism, with the first signal facilitating priming of inflammasome components while the second signal triggers complex assembly. Once assembled, the inflammasome recruits and activates pro-caspase-1, which in turn processes pro-interleukin (IL)-18 and pro-IL-1β into their bio-active forms. Owing to its key role in the regulation of innate immune responses, the inflammasome has emerged as a therapeutic target for the treatment of inflammatory conditions. In this study we demonstrate that IRE1α, a key component of the Unfolded Protein Response, contributes to assembly of the NLRP3 inflammasome. Blockade of IRE1α RNase signaling lowered NLRP3 inflammasome assembly, caspase-1 activation and pro-IL-1β processing. These results underscore both the importance and potential therapeutic relevance of targeting IRE1α signaling in conditions of excessive inflammasome formation.

DOI: https://doi.org/10.1038/s41419-019-1847-z

BMB Rep. 2019 Aug 12. pii: 4615. [Epub ahead of print]

Overcoming multidrug resistance by activating unfolded protein response of the endoplasmic reticulum in cisplatin-resistant A2780/CisR ovarian cancer cells.

Euitaek Jung, Dongsoo Koh, Yoongho Lim, Soon Young Shin, Young Han Lee.

Cisplatin is a widely used anti-cancer agent. However, the effectiveness of cisplatin has been limited by the commonly developed drug resistance. This study aimed to investigate the potential effects of endoplasmic reticulum (ER) stress to overcome drug resistance using the cisplatin-resistant A2780/CisR ovarian cancer cell model. The synthetic chalcone derivative (E)-3-(3,5-dimethoxyphenyl)-1-(2-methoxyphenyl)prop- 2-en-1-one (named DPP23) is an ER stress inducer. We found that DPP23 triggered apoptosis in both parental cisplatinsensitive A2780 and cisplatin-resistant A2780/CisR ovarian cancer cells due to activation of reactive oxygen species (ROS)-mediated unfolded protein response (UPR) pathway in the endoplasmic reticulum. This result suggests that ROSmediated UPR activation is potential in overcoming drug resistance. DPP23 can be used as a target pharmacophore for the development of novel chemotherapeutic agents capable of overcoming drug resistance in cancer cells, particularly ovarian cancer cells.

Cell Rep. 2019 Aug 13. pii: S2211-1247(19)30953-2. [Epub ahead of print]28(7): 1659-1669.e5

Compromised Mitochondrial Protein Import Acts as a Signal for UPRmt.

Stéphane G Rolland, Sandra Schneid, Melanie Schwarz, Elisabeth Rackles, Christian Fischer, Simon Haeussler, Saroj G Regmi, Assa Yeroslaviz, Bianca Habermann, Dejana Mokranjac, Eric Lambie, Barbara Conradt.

The induction of the mitochondrial unfolded protein response (UPRmt) results in increased transcription of the gene encoding the mitochondrial chaperone HSP70. We systematically screened the C. elegans genome and identified 171 genes that, when knocked down, induce the expression of an hsp-6 HSP70 reporter and encode mitochondrial proteins. These genes represent many, but not all, mitochondrial processes (e.g., mitochondrial calcium homeostasis and mitophagy are not represented). Knockdown of these genes leads to reduced mitochondrial membrane potential and, hence, decreased protein import into mitochondria. In addition, it induces UPRmt in a manner that is dependent on ATFS-1 but that is not antagonized by the kinase GCN-2. We propose that compromised mitochondrial protein import signals the induction of UPRmt and that the mitochondrial targeting sequence of ATFS-1 functions as a sensor for this signal.

Keywords: ATFS-1; C. elegans; GCN-2; UPR(mt); hsp-6; hsp-60; mitochondria

DOI: https://doi.org/10.1016/j.celrep.2019.07.049