bims-unfpre 2022-06-12 papers

Issue of 2022‒06‒12
six papers selected by
Susan Logue
University of Manitoba

ACS Chem Biol. 2022 Jun 08.

Monitoring Protein Import into the Endoplasmic Reticulum in Living Cells with Proximity Labeling.

Ziqi Lyu, Melody M Sycks, Mateo F Espinoza, Khanh K Nguyen, Maureen R Montoya, Cheska M Galapate, Liangyong Mei, Joseph C Genereux.

The proper trafficking of eukaryotic proteins is essential to cellular function. Genetic, environmental, and other stresses can induce protein mistargeting and, in turn, threaten cellular protein homeostasis. Current methods for measuring protein mistargeting are difficult to translate to living cells, and thus the role of cellular signaling networks in stress-dependent protein mistargeting processes, such as ER pre-emptive quality control (ER pQC), is difficult to parse. Herein, we use genetically encoded peroxidases to characterize protein import into the endoplasmic reticulum (ER). We show that the ERHRP/cytAPEX pair provides good selectivity and sensitivity for both multiplexed protein labeling and for identifying protein mistargeting, using the known ER pQC substrate transthyretin (TTR). Although ERHRP labeling induces formation of detergent-resistant TTR aggregates, this is minimized by using low ERHRP expression, without loss of labeling efficiency. cytAPEX labeling recovers TTR that is mistargeted as a consequence of Sec61 inhibition or ER stress-induced ER pQC. Furthermore, we discover that stress-free activation of the ER stress-associated transcription factor ATF6 recapitulates the TTR import deficiency of ER pQC. Hence, proximity labeling is an effective strategy for characterizing factors that influence ER protein import in living cells.

DOI: https://doi.org/10.1021/acschembio.2c00405

Int J Mol Sci. 2022 May 24. pii: 5894. [Epub ahead of print]23(11):

The Common Cellular Events in the Neurodegenerative Diseases and the Associated Role of Endoplasmic Reticulum Stress.

Soojeong Kim, Doo Kyung Kim, Seho Jeong, Jaemin Lee.

Neurodegenerative diseases are inseparably linked with aging and increase as life expectancy extends. There are common dysfunctions in various cellular events shared among neurogenerative diseases, such as calcium dyshomeostasis, neuroinflammation, and age-associated decline in the autophagy-lysosome system. However, most of all, the prominent pathological feature of neurodegenerative diseases is the toxic buildup of misfolded protein aggregates and inclusion bodies accompanied by an impairment in proteostasis. Recent studies have suggested a close association between endoplasmic reticulum (ER) stress and neurodegenerative pathology in cellular and animal models as well as in human patients. The contribution of mutant or misfolded protein-triggered ER stress and its associated signaling events, such as unfolded protein response (UPR), to the pathophysiology of various neurodegenerative disorders, including Alzheimer's, Parkinson's, and Huntington's disease, amyotrophic lateral sclerosis, and prion disease, is described here. Impaired UPR action is commonly attributed to exacerbated ER stress, pathogenic protein aggregate accumulation, and deteriorating neurodegenerative pathologies. Thus, activating certain UPR components has been shown to alleviate ER stress and its associated neurodegeneration. However, uncontrolled activation of some UPR factors has also been demonstrated to worsen neurodegenerative phenotypes, suggesting that detailed molecular mechanisms around ER stress and its related neurodegenerations should be understood to develop effective therapeutics against aging-associated neurological syndromes. We also discuss current therapeutic endeavors, such as the development of small molecules that selectively target individual UPR components and address ER stress in general.

Keywords: Alzheimer’s disease; ER stress; Huntington’s disease; Parkinson’s disease; amyotrophic lateral sclerosis; endoplasmic reticulum; misfolded protein; neurodegenerative disease; prion disease; unfolded protein response

DOI: https://doi.org/10.3390/ijms23115894

Apoptosis. 2022 Jun 04.

XIAP as a multifaceted molecule in Cellular Signaling.

Mina Hanifeh, Farangis Ataei.

XIAP, X-linked inhibitor of apoptosis protein, is a member of the inhibitor of apoptosis protein (IAP) family known for its important conserved inhibitory effect on caspase activity. Since the introduction of XIAP almost three decades ago, numerous experimental studies have been performed for a wide range of cellular pathways and mechanisms. In this perspective, we summarize key trends of XIAP as an important regulator of cellular signaling. Experimental research indicates that XIAP as a key molecule of cell death not only suppress caspases and apoptosis, but also regulates inflammatory signaling, mitogenic kinase signaling, cell proliferation as well as cell invasion and metastasis. In this review, we provide basic knowledge of the roles of XIAP, explain its role in necroptosis, anoikis, autophagy and neuronal differentiation. XIAP is involved in regulating intracellular ROS production and copper homeostasis which this review focuses on. A different face of XIAP in response to DNA damage and chronic ER stress is also discussed.

Keywords: Cell death; ER stress; Multifunction; ROS production; XIAP

DOI: https://doi.org/10.1007/s10495-022-01734-z

Cell Rep. 2022 Jun 07. pii: S2211-1247(22)00713-6. [Epub ahead of print]39(10): 110931

Protein disulfide isomerase PDI-6 regulates Wnt secretion to coordinate inter-tissue UPRmt activation and lifespan extension in C. elegans.

Xinyu Li, Jiasheng Li, Di Zhu, Ning Zhang, Xusheng Hao, Wenfeng Zhang, Qian Zhang, Yangli Liu, Xueying Wu, Ye Tian.

Coordination of inter-tissue stress signaling is essential for organismal fitness. Neuronal mitochondrial perturbations activate the mitochondrial unfolded-protein response (UPRmt) in the intestine via the mitokine Wnt signaling in Caenorhabditis elegans. Here, we found that the protein disulfide isomerase PDI-6 coordinates inter-tissue UPRmt signaling via regulating the Wnt ligand EGL-20. PDI-6 is expressed in the endoplasmic reticulum (ER) and interacts with EGL-20 through disulfide bonds that are essential for EGL-20 stability and secretion. pdi-6 deficiency results in misfolded EGL-20, which leads to its degradation via ER-associated protein degradation (ERAD) machinery. Expression of PDI-6 declines drastically with aging, and animals with pdi-6 deficiency have decreased lifespan. Overexpression of PDI-6 is sufficient to maintain Wnt/EGL-20 protein levels during aging, activating the UPRmt, and significantly extending lifespan in a Wnt- and UPRmt-dependent manner. Our study reveals that protein disulfide isomerase facilitates Wnt secretion to coordinate the inter-tissue UPRmt signaling and organismal aging.

Keywords: CP: Cell biology; PDI; PDI-6; UPR(mt); Wnt signaling; aging; cell-non-autonomous regulation; disulfide bond formation; mitochondrial unfolded-protein response; protein disulfide isomerase

DOI: https://doi.org/10.1016/j.celrep.2022.110931

Cancers (Basel). 2022 Jun 03. pii: 2780. [Epub ahead of print]14(11):

Interconnected Adaptive Responses: A Way Out for Cancer Cells to Avoid Cellular Demise.

Gabriella D'Orazi, Mara Cirone.

Different from normal cells, cancer cells must hyperactivate a variety of integrated responses in order to survive their basal stress or its exacerbation caused by exposure to anti-cancer agents. As cancer cells become particularly dependent on these adaptive responses, namely UPR, DDR autophagy, anti-oxidant and heat shock responses, this turns out to be an Achille's heel, which allows them to be selectively killed while sparing normal unstressed cells. Better knowledge of the cross-talk between these adaptive processes and their impact on the immune system is needed to design more effective anti-cancer therapies, as reviewed in this paper.

Keywords: DDR; ER stress; HSPs; UPR; anti-oxidant response; autophagy; cancer; death resistance

DOI: https://doi.org/10.3390/cancers14112780

BMC Cancer. 2022 Jun 07. 22(1): 622

Linking unfolded protein response to ovarian cancer cell fusion.

Lucile Yart, Daniel Bastida-Ruiz, Mathilde Allard, Pierre-Yves Dietrich, Patrick Petignat, Marie Cohen.

BACKGROUND: Polyploid giant cancer cells (PGCCs) have been observed in epithelial ovarian tumors. They can resist antimitotic drugs, thus participating in tumor maintenance and recurrence. Although their origin remains unclear, PGCC formation seems to be enhanced by conditions that trigger the unfolded protein response (UPR) such as hypoxia or chemotherapeutic drugs like paclitaxel. Hypoxia has been shown to promote the formation of ovarian PGCCs by cell fusion. We thus hypothesized that the UPR could be involved in EOC cell fusion, possibly explaining the occurrence of PGCCs and the aggressiveness of EOC.METHODS: The UPR was induced in two ovarian cancer cell lines (SKOV3 and COV318). The UPR activation was assessed by Western blot and polyploidy indexes were calculated. Then, to confirm the implication of cell fusion in PGCC formation, two populations of SKOV3 cells were transfected with plasmids encoding for two distinct nuclear fluorescent proteins (GFP and mCherry) associated with different antibiotic resistance genes, and the two cell populations were mixed in co-culture. The co-culture was submitted to a double-antibiotic selection. The resulting cell population was characterized for its morphology, cyclicity, and proliferative and tumorigenic capacities, in addition to transcriptomic characterization.
RESULTS: We demonstrated that cell fusion could be involved in the generation of ovarian PGCCs and this process was promoted by paclitaxel and the UPR activation. Double-antibiotic treatment of PGCCs led to the selection of a pure population of cells containing both GFP- and mCherry-positive nuclei. Interestingly, after 3 weeks of selection, we observed that these cells were no longer polynucleated but displayed a single nucleus positive for both fluorescent proteins, suggesting that genetic material mixing had occurred. These cells had reinitiated their normal cell cycles, acquired an increased invasive capacity, and could form ovarian tumors in ovo.
CONCLUSIONS: The UPR activation increased the in vitro formation of PGCCs by cell fusion, with the newly generated cells further acquiring new properties. The UPR modulation in ovarian cancer patients could represent an interesting therapeutic strategy to avoid the formation of PGCCs and therefore limit cancer relapse and drug resistance.

Keywords: Cell fusion; Invasion; Ovarian cancer; Polyploid giant cancer cell; Unfolded protein response

DOI: https://doi.org/10.1186/s12885-022-09648-4