bims-unfpre 2024-05-05 papers

bims-unfpre

Biomed News

on Unfolded protein response

Issue of 2024–05–05
nine papers selected by
Susan Logue, University of Manitoba

Hepatic IRE1α-XBP1 signaling promotes GDF15-mediated anorexia and body weight loss in chemotherapy.
GRP78 blockade overcomes acquired resistance to EGFR-tyrosine kinase inhibitors in non-small cell lung cancer.
Cytotoxic sigma-2 ligands trigger cancer cell death via cholesterol-induced-ER-stress.
Sensitivity and activation of endoplasmic reticulum stress response and apoptosis in the perinatal sheep heart.
CREB3 mediates the transcriptional regulation of PGC-1α, a master regulator of energy homeostasis and mitochondrial biogenesis.
Turnover of EDEM1, an ERAD-enhancing factor, is mediated by multiple degradation routes.
Tailored UPRE2 variants for dynamic gene regulation in yeast.
Lysosomal dysfunction by inactivation of V-ATPase drives innate immune response in C. elegans.
Ovarian PERK/NRF2/CX43/StAR/progesterone pathway activation mediates female reproductive dysfunction induced by cold exposure.

J Exp Med. 2024 Jul 01. pii: e20231395. [Epub ahead of print]221(7):

Hepatic IRE1α-XBP1 signaling promotes GDF15-mediated anorexia and body weight loss in chemotherapy.

Yuexiao Tang, Tao Yao, Xin Tian, Xintong Xia, Xingxiao Huang, Zhewen Qin, Zhong Shen, Lin Zhao, Yaping Zhao, Bowen Diao, Yan Ping, Xiaoxiao Zheng, Yonghao Xu, Hui Chen, Tao Qian, Tao Ma, Ben Zhou, Suowen Xu, Qimin Zhou, Yong Liu, Mengle Shao, Wei Chen, Bo Shan, Ying Wu.

Platinum-based chemotherapy drugs can lead to the development of anorexia, a detrimental effect on the overall health of cancer patients. However, managing chemotherapy-induced anorexia and subsequent weight loss remains challenging due to limited effective therapeutic strategies. Growth differentiation factor 15 (GDF15) has recently gained significant attention in the context of chemotherapy-induced anorexia. Here, we report that hepatic GDF15 plays a crucial role in regulating body weight in response to chemo drugs cisplatin and doxorubicin. Cisplatin and doxorubicin treatments induce hepatic Gdf15 expression and elevate circulating GDF15 levels, leading to hunger suppression and subsequent weight loss. Mechanistically, selective activation by chemotherapy of hepatic IRE1α-XBP1 pathway of the unfolded protein response (UPR) upregulates Gdf15 expression. Genetic and pharmacological inactivation of IRE1α is sufficient to ameliorate chemotherapy-induced anorexia and body weight loss. These results identify hepatic IRE1α as a molecular driver of GDF15-mediated anorexia and suggest that blocking IRE1α RNase activity offers a therapeutic strategy to alleviate the adverse anorexia effects in chemotherapy.

DOI: https://doi.org/10.1084/jem.20231395
Life Sci. 2024 Apr 30. pii: S0024-3205(24)00271-6. [Epub ahead of print] 122681

GRP78 blockade overcomes acquired resistance to EGFR-tyrosine kinase inhibitors in non-small cell lung cancer.

Jaewoo Park, Baskaran Purushothaman, Sera Hong, Munkyung Choi, Kyung Hwan Jegal, Miso Park, Joon Myong Song, Keon Wook Kang.

   AIMS: While significant upregulation of GRP78 has been documented in lung cancer patients, its association with resistance to epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) remains underexamined. Our study aimed to elucidate the functional importance of GRP78 in acquired resistance to EGFR-TKIs in non-small cell lung cancer (NSCLC) and to evaluate its potential as a therapeutic target.
MAIN METHODS: Immunoblot analysis or flow cytometry was employed to assess several markers for endoplasmic reticulum (ER) stress and apoptosis. Ru(II) complex I and HA15, two known GRP78 inhibitors, were used to evaluate the functional role of GRP78. A Xenograft assay was performed to evaluate the in vivo anti-cancer effects of the GRP78 inhibitors.
KEY FINDINGS: We validated a significant increase in GRP78 protein levels in HCC827-GR, H1993-GR, and H1993-ER cells. The EGFR-TKI-resistant cells overexpressing GRP78 exhibited significantly higher cell proliferation rates than did their parental counterparts. Notably, GRP78 inhibition resulted in a more profound anti-proliferative and apoptotic response via heightened ER stress and subsequent reactive oxygen species (ROS) production in EGFR-TKI-resistant cell lines compared with their parental cells. In xenograft models implanted with HCC827-GR, both Ru(II) complex I and HA15 significantly suppressed tumor growth and reduced tumor weight. Additionally, we confirmed that GRP78 plays a critical role in the proliferation of H1975, an EGFR-TKI-resistant T790M-mutant cell line, relative to other NSCLC cell lines.
SIGNIFICANCE: Our findings strongly support targeting of GRP78 as a promising therapeutic strategy for NSCLC patients with acquired resistance to EGFR-TKIs.

Keywords:  EGFR-TKI resistance; ER stress; GRP78; NSCLC; Therapeutic target

DOI:  https://doi.org/10.1016/j.lfs.2024.122681
Cell Death Dis. 2024 May 02. 15(5): 309

Cytotoxic sigma-2 ligands trigger cancer cell death via cholesterol-induced-ER-stress.

Rony Takchi, Bethany C Prudner, Qingqing Gong, Takaomi Hagi, Kenneth F Newcomer, Linda X Jin, Suwanna Vangveravong, Brian A Van Tine, William G Hawkins, Dirk Spitzer.

Sigma-2-ligands (S2L) are characterized by high binding affinities to their cognate sigma-2 receptor, overexpressed in rapidly proliferating tumor cells. As such, S2L were developed as imaging probes (ISO1) or as cancer therapeutics, alone (SV119 [C6], SW43 [C10]) and as delivery vehicles for cytotoxic drug cargoes (C6-Erastin, C10-SMAC). However, the exact mechanism of S2L-induced cytotoxicity remains to be fully elucidated. A series of high-affinity S2L were evaluated regarding their cytotoxicity profiles across cancer cell lines. While C6 and C10 displayed distinct cytotoxicities, C0 and ISO1 were essentially non-toxic. Confocal microscopy and lipidomics analysis in cellular and mouse models revealed that C10 induced increases in intralysosomal free cholesterol and in cholesterol esters, suggestive of unaltered intracellular cholesterol trafficking. Cytotoxicity was caused by cholesterol excess, a phenomenon that contrasts the effects of NPC1 inhibition. RNA-sequencing revealed gene clusters involved in cholesterol homeostasis and ER stress response exclusively by cytotoxic S2L. ER stress markers were confirmed by qPCR and their targeted modulation inhibited or enhanced cytotoxicity of C10 in a predicted manner. Moreover, C10 increased sterol regulatory element-binding protein 2 (SREBP2) and low-density lipoprotein receptor (LDLR), both found to be pro-survival factors activated by ER stress. Furthermore, inhibition of downstream processes of the adaptive response to S2L with simvastatin resulted in synergistic treatment outcomes in combination with C10. Of note, the S2L conjugates retained the ER stress response of the parental ligands, indicative of cholesterol homeostasis being involved in the overall cytotoxicity of the drug conjugates. Based on these findings, we conclude that S2L-mediated cell death is due to free cholesterol accumulation that leads to ER stress. Consequently, the cytotoxic profiles of S2L drug conjugates are proposed to be enhanced via concurrent ER stress inducers or simvastatin, strategies that could be instrumental on the path toward tumor eradication.

DOI: https://doi.org/10.1038/s41419-024-06693-8
Am J Physiol Heart Circ Physiol. 2024 May 03.

Sensitivity and activation of endoplasmic reticulum stress response and apoptosis in the perinatal sheep heart.

Karthikeyan Bose, Herbert M Espinoza, Samantha Louey, Sonnet S Jonker.

  While the unfolded protein response (UPR) contributes to survival by removing misfolded proteins, ER stress also activates pro-apoptotic pathways. Changed sensitivity to normal developmental stimuli may underlie observed cardiomyocyte apoptosis in the healthy perinatal heart.
METHODS: We determined in vitro sensitivity to thapsigargin in sheep cardiomyocytes from four perinatal ages. In utero cardiac activation of endoplasmic reticulum (ER) stress and apoptotic pathways was determined at these same ages.
RESULTS: Thapsigargin-induced phosphorylation of EIF2A decreased 72% between 135 and 143 dGA (P=0.0096) and remained low at 1 dPN (P=0.0080). Conversely, thapsigargin-induced caspase cleavage was highest around the time of birth: cleaved caspase 3 was highest at 1 dPN (3.8-fold vs. 135 dGA, P=0.0380; 7.8-fold vs. 5 dPN, P=0.0118), cleaved caspase 7 and cleaved caspase 12 both increased between 135 and 143 dGA (25-fold and 6.9-fold respectively, both P<0.0001), and remained elevated at 1 dPN. Induced apoptosis, measured by TUNEL assay, was highest around the time of birth (P<0.0001). There were changes in myocardial ER stress pathway components in utero. GRP78 protein levels were high in the fetus and declined after birth (P<0.0001). EIF2A phosphorylation was profoundly depressed at 1 dPN (vs. 143 dGA, P=0.0113).
CONCLUSION: There is dynamic regulation of ER proteostasis, ER stress, and the apoptosis cascade in the perinatal heart. Apoptotic signaling is more readily activated in fetal cardiomyocytes near birth, leading to widespread caspase cleavage in the newborn heart. These pathways are important for regulation of normal maturation in the healthy perinatal heart.

Keywords:  Endoplasmic Reticulum Stress; Fetal Development; Myocardium; Myocytes, Cardiac; Unfolded Protein Response

DOI:  https://doi.org/10.1152/ajpheart.00043.2024
FEBS Lett. 2024 May 02.

CREB3 mediates the transcriptional regulation of PGC-1α, a master regulator of energy homeostasis and mitochondrial biogenesis.

Briana Locke, Elena Campbell, Ray Lu.

  Lipid metabolism hinges on a balance between lipogenesis and fatty acid oxidation (FAO). Disruptions in this balance can induce endoplasmic reticulum (ER) stress triggering the unfolded protein response (UPR) and contribute to metabolic diseases. The UPR protein, Luman or CREB3, has recently been implicated in metabolic regulation-CREB3 knockout mice exhibit resistance to diet-induced obesity and altered insulin sensitivity. Here, we show that CREB3 activated PPARGC1A transcription from a 1 kb promoter region. An increase in CREB3 expression correlated inversely with endogenous PPARGC1A mRNA levels and genes involved in FAO. As PGC-1α encoded by PPARGC1A is a master regulator of mitochondrial biogenesis and energy homeostasis, these findings demonstrate that CREB3 is a transcriptional regulator of PGC-1α, underlining the potential role of CREB3 in energy metabolism.

Keywords:  CREB3; PGC‐1α; endoplasmic reticulum stress; fatty acid oxidation; metabolism; transcriptional regulation

DOI:  https://doi.org/10.1002/1873-3468.14897
Genes Cells. 2024 Apr 29.

Turnover of EDEM1, an ERAD-enhancing factor, is mediated by multiple degradation routes.

Riko Katsuki, Mai Kanuka, Ren Ohta, Shusei Yoshida, Taku Tamura.

  Quality-based protein production and degradation in the endoplasmic reticulum (ER) are essential for eukaryotic cell survival. During protein maturation in the ER, misfolded or unassembled proteins are destined for disposal through a process known as ER-associated degradation (ERAD). EDEM1 is an ERAD-accelerating factor whose gene expression is upregulated by the accumulation of aberrant proteins in the ER, known as ER stress. Although the role of EDEM1 in ERAD has been studied in detail, the turnover of EDEM1 by intracellular degradation machinery, including the proteasome and autophagy, is not well understood. To clarify EDEM1 regulation in the protein level, degradation mechanism of EDEM1 was examined. Our results indicate that both ERAD and autophagy degrade EDEM1 alike misfolded degradation substrates, although each degradation machinery targets EDEM1 in different folded states of proteins. We also found that ERAD factors, including the SEL1L/Hrd1 complex, YOD1, XTP3B, ERdj3, VIMP, BAG6, and JB12, but not OS9, are involved in EDEM1 degradation in a mannose-trimming-dependent and -independent manner. Our results suggest that the ERAD accelerating factor, EDEM1, is turned over by the ERAD itself, similar to ERAD clients.

Keywords:  EDEM1; ER quality control; ER stress; ERAD; autophagy; proteasome; protein degradation; protein turnover; unfolded protein response

DOI:  https://doi.org/10.1111/gtc.13117
Proc Natl Acad Sci U S A. 2024 May 07. 121(19): e2315729121

Tailored UPRE2 variants for dynamic gene regulation in yeast.

Chufan Xiao, Xiufang Liu, Yuyang Pan, Yanling Li, Ling Qin, Zhibo Yan, Yunzi Feng, Mouming Zhao, Mingtao Huang.

  Genetic elements are foundational in synthetic biology serving as vital building blocks. They enable programming host cells for efficient production of valuable chemicals and recombinant proteins. The unfolded protein response (UPR) is a stress pathway in which the transcription factor Hac1 interacts with the upstream unfolded protein response element (UPRE) of the promoter to restore endoplasmic reticulum (ER) homeostasis. Here, we created a UPRE2 mutant (UPRE2m) library. Several rounds of screening identified many elements with enhanced responsiveness and a wider dynamic range. The most active element m84 displayed a response activity 3.72 times higher than the native UPRE2. These potent elements are versatile and compatible with various promoters. Overexpression of HAC1 enhanced stress signal transduction, expanding the signal output range of UPRE2m. Through molecular modeling and site-directed mutagenesis, we pinpointed the DNA-binding residue Lys60 in Hac1(Hac1-K60). We also confirmed that UPRE2m exhibited a higher binding affinity to Hac1. This shed light on the mechanism underlying the Hac1-UPRE2m interaction. Importantly, applying UPRE2m for target gene regulation effectively increased both recombinant protein production and natural product synthesis. These genetic elements provide valuable tools for dynamically regulating gene expression in yeast cell factories.

Keywords:  Hac1; UPRE2 variants; responsive promoter; unfolded protein response

DOI:  https://doi.org/10.1073/pnas.2315729121
Cell Rep. 2024 Apr 26. pii: S2211-1247(24)00466-2. [Epub ahead of print]43(5): 114138

Lysosomal dysfunction by inactivation of V-ATPase drives innate immune response in C. elegans.

Xuepiao Pu, Bin Qi.

  Pathogens target vacuolar ATPase (V-ATPase) to inhibit lysosomal acidification or lysosomal fusion, causing lysosomal dysfunction. However, it remains unknown whether cells can detect dysfunctional lysosomes and initiate an immune response. In this study, we discover that dysfunction of lysosomes caused by inactivation of V-ATPase enhances innate immunity against bacterial infections. We find that lysosomal V-ATPase interacts with DVE-1, whose nuclear localization serves as a proxy for the induction of mitochondrial unfolded protein response (UPRmt). The inactivation of V-ATPase promotes the nuclear localization of DVE-1, activating UPRmt and inducing downstream immune response genes. Furthermore, pathogen resistance conferred by inactivation of V-ATPase requires dve-1 and its downstream immune effectors. Interestingly, animals grow slower after vha RNAi, suggesting that the vha-RNAi-induced immune response costs the most energy through activation of DVE-1, which trades off with growth. This study reveals how dysfunctional lysosomes can trigger an immune response, emphasizing the importance of conserving energy during immune defense.

Keywords:  C. elegans; CP: Immunology; UPR(mt); V-ATPase; immunity; lysosomes; mitochondria; mitochondrial surveillance; pathogen

DOI:  https://doi.org/10.1016/j.celrep.2024.114138
Sci Rep. 2024 May 04. 14(1): 10248

Ovarian PERK/NRF2/CX43/StAR/progesterone pathway activation mediates female reproductive dysfunction induced by cold exposure.

Mengnan Ding, Yarong Lu, Qing Wen, Chen Xing, Xin Huang, Yifan Zhang, Wei Wang, Chongchong Zhang, Min Zhang, Fanfei Meng, Kun Liu, Guangchao Liu, Lun Song.

  Ambient air temperature is a key factor affecting human health. Female reproductive disorders are representative health risk events under low temperature. However, the mechanism involving in cold-induced female reproductive disorders remains largely unknown. Female mice were intermittently exposed to cold conditions (4 °C) to address the health risk of low temperature on female reproductive system. Primary granulosa cells (GCs) were prepared and cultured under low temperature (35 °C) or exposed to β3-adrenoreceptor agonist, isoproterenol, to mimic the condition of cold exposure. Western-blot, RT-PCR, co-IP, ELISA, pharmacological inhibition or siRNA-mediated knockdown of target gene were performed to investigate the possible role of hormones, gap conjunction proteins, and ER stress sensor protein in regulating female reproductive disorders under cold exposure. Cold exposure induced estrous cycle disorder and follicular dysplasia in female mice, accompanying with abnormal upregulation of progesterone and its synthetic rate-limiting enzyme, StAR, in the ovarian granulosa cells. Under the same conditions, an increase in connexin 43 (CX43) expressions in the GCs was also observed, which contributed to elevated progesterone levels in the ovary. Moreover, ER stress sensor protein, PERK, was activated in the ovarian GCs after cold exposure, leading to the upregulation of downstream NRF2-dependent CX43 transcription and aberrant increase in progesterone synthesis. Most importantly, blocking PERK expression in vivo significantly inhibited NRF2/CX43/StAR/progesterone pathway activation in the ovary and efficiently rescued the prolongation of estrous cycle and the increase in follicular atresia of the female mice induced by cold stress. We have elucidated the mechanism of ovarian PERK/NRF2/CX43/StAR/progesterone pathway activation in mediating female reproductive disorder under cold exposure. Targeting PERK might be helpful for maintaining female reproductive health under cold conditions.

Keywords:  CX43; Cold; Female reproductive disorders; NRF2; PERK; Progesterone

DOI:  https://doi.org/10.1038/s41598-024-60907-9