bims-unfpre 2021-12-26 papers

Issue of 2021–12–26
five papers selected by
Susan Logue, University of Manitoba

Mol Cell Proteomics. 2021 Dec 17. pii: S1535-9476(21)00160-2. [Epub ahead of print] 100188

Characterization of the AGR2 interactome uncovers new players of Protein Disulfide Isomerase network in cancer cells.

Pavla Bouchalova, Lucia Sommerova, David Potesil, Andrea Martisova, Petr Lapcik, Veronika Koci, Alex Scherl, Petr Vonka, Joan Planas-Iglesias, Eric Chevet, Pavel Bouchal, Roman Hrstka.

AGR2 is an endoplasmic reticulum (ER)-resident protein disulfide isomerase (PDI) known to be overexpressed in many human epithelial cancers, and is involved in cell migration, cellular transformation, angiogenesis, and metastasis. This protein inhibits the activity of the tumor suppressor p53 and its expression levels can be used to predict cancer patient outcome. However, the precise network of AGR2-interacting partners and clients remains to be fully characterized. Herein, we used label-free quantification and also SILAC-based LC-MS/MS analyses to identify proteins interacting with AGR2. Functional annotation confirmed that AGR2 and its interaction partners are associated with processes in the ER that maintain intracellular metabolic homeostasis and participate in the unfolded protein response, including those associated with changes in cellular metabolism, energy, and redox states in response to ER stress. As a proof of concept, the interaction between AGR2 and PDIA3, another ER resident PDI, was studied in more detail. Pathway analysis revealed that AGR2 and PDIA3 play roles in protein folding in ER, including posttranslational modification and in cellular response to stress. We confirmed the AGR2-PDIA3 complex formation in cancer cells, which was enhanced in response to ER stress. Accordingly, molecular docking characterized potential quaternary structure of this complex, however, it remains to be elucidated whether (i) AGR2 rather contributes to PDIA3 maturation in ER, (ii) the complex directly acts in cellular signaling, or (iii) mediates AGR2 secretion. Our study provides a comprehensive insight into the protein-protein interaction network of AGR2 by identifying functionally relevant proteins and related cellular and biochemical pathways associated with the role of AGR2 in cancer cells.

Keywords: anterior gradient protein 2; mass spectrometry; protein disulfide isomerase; protein-protein interactions; secretory pathway

DOI: https://doi.org/10.1016/j.mcpro.2021.100188

Antioxidants (Basel). 2021 Nov 26. pii: 1897. [Epub ahead of print]10(12):

Endoplasmic Reticulum Stress Promotes iNOS/NO and Influences Inflammation in the Development of Doxorubicin-Induced Cardiomyopathy.

Ashim K Bagchi, Akshi Malik, Gauri Akolkar, Davinder S Jassal, Pawan K Singal.

Doxorubicin (Dox) is known to cause heart failure in some cancer patients. Despite extensive studies over the past half century, the subcellular basis of Dox-induced cardiomyopathy (DIC) is still elusive. Earlier, we suggested that Dox causes a delayed activation of unfolded protein response (UPR) which may promote mitochondrial Bax activity leading to cardiomyocyte death. As a follow up, using NO donor, S-Nitroso-N-acetyl-d,l-penicillamine (SNAP), and/or NOS inhibitor, N(ω)-nitro-L-arginine methyl ester (L-NAME), we now show that endoplasmic reticulum (ER) stress promotes inflammation through iNOS/NO-induced TLR2 activation. In vivo Dox treatment increased mitochondrial iNOS to promote ER stress as there was an increase in Bip (Grp78) response, proapoptotic CHOP (DDIT3) and ER-mediated Caspase 12 activation. Increased iNOS activity is associated with an increase in TLR2 and TNF-α receptor associated factor 2 (TRAF2). These two together with NF-κB p105/50 expression and a synergistic support through ER stress, promote inflammatory response in the myocardium leading to cell death and ultimately fostering DIC conditions. In the presence of NOS inhibitor, such detrimental effects of Dox were inhibited, suggesting iNOS/NO as key mediators of Dox-induced inflammatory as well as apoptotic responses.

Keywords: Dox-induced cardiomyopathy; ER stress; Toll-like receptor 2; apoptosis; inducible nitric oxide synthase

DOI: https://doi.org/10.3390/antiox10121897

Neurosci Lett. 2021 Dec 16. pii: S0304-3940(21)00779-5. [Epub ahead of print]770 136400

Nrf2 loss of function exacerbates endoplasmic reticulum stress-induced apoptosis in TBI mice.

Guozhu Sun, Zongmao Zhao, Jiadong Lang, Boyu Sun, Qitao Zhao.

Nuclear factor erythroid 2-related factor 2 (Nrf2) plays an important role in neuroprotection and recover. Our studies have showed that endoplasmic reticulum (ER) stress-induced apoptosis aggravates secondary damage following traumatic brain injury (TBI). Whether Nrf2 involved in ER stress and ER stress-mediated apoptosis is not clearly investigated. This present study explored the effect of Nrf2 knockout on ER stress and ER stress-induced apoptosis in TBI mice. A lateral fluid percussion injury (FPI)model of TBI was built based on Nrf2 knockout (Nrf2(-/-)) mice and wild-type (Nrf2(+/+)) mice, and the expressions of marker proteins of ER stress and ER stress-induced apoptosis were checked at 24 h following TBI. We found that Nrf2(-/-) mice presented more severe neurological deficit, brain edema and neuronal cell apoptosis compared with Nrf2(+/+) mice. And, the TBI Nrf2(-/-) mice were significantly increased expression of marker proteins of ER stress and ER stress-induced apoptotic pathway including glucose regulated protein (GRP78), protein kinase RNA-like ER kinase (PERK), inositol requiring enzyme (IRE1), activating transcription factor 6 (ATF6), C/EBP homologous protein (CHOP), caspase-12 and caspase-3, compared with that in WT mice. These results suggest that Nrf2 could ameliorate TBI-induced second brain injury partly through ER stress signal pathway.

Keywords: Apoptosis; Endoplasmic reticulum stress; Neuroprotection; Nrf2; Traumatic brain injury

DOI: https://doi.org/10.1016/j.neulet.2021.136400

Cells. 2021 Dec 19. pii: 3585. [Epub ahead of print]10(12):

Single-Cell Transcriptomics Links Loss of Human Pancreatic β-Cell Identity to ER Stress.

Nathalie Groen, Floris Leenders, Ahmed Mahfouz, Amadeo Munoz-Garcia, Mauro J Muraro, Natascha de Graaf, Ton J Rabelink, Rob Hoeben, Alexander van Oudenaarden, Arnaud Zaldumbide, Marcel J T Reinders, Eelco J P de Koning, Françoise Carlotti.

The maintenance of pancreatic islet architecture is crucial for proper β-cell function. We previously reported that disruption of human islet integrity could result in altered β-cell identity. Here we combine β-cell lineage tracing and single-cell transcriptomics to investigate the mechanisms underlying this process in primary human islet cells. Using drug-induced ER stress and cytoskeleton modification models, we demonstrate that altering the islet structure triggers an unfolding protein response that causes the downregulation of β-cell maturity genes. Collectively, our findings illustrate the close relationship between endoplasmic reticulum homeostasis and β-cell phenotype, and strengthen the concept of altered β-cell identity as a mechanism underlying the loss of functional β-cell mass.

Keywords: ER stress; human pancreatic islets; islet integrity; single-cell RNAseq; type 2 diabetes; β-cells

DOI: https://doi.org/10.3390/cells10123585

Cells. 2021 Nov 28. pii: 3337. [Epub ahead of print]10(12):

Protein Aggregation in the ER: Calm behind the Storm.

Haisen Li, Shengyi Sun.

As one of the largest organelles in eukaryotic cells, the endoplasmic reticulum (ER) plays a vital role in the synthesis, folding, and assembly of secretory and membrane proteins. To maintain its homeostasis, the ER is equipped with an elaborate network of protein folding chaperones and multiple quality control pathways whose cooperative actions safeguard the fidelity of protein biogenesis. However, due to genetic abnormalities, the error-prone nature of protein folding and assembly, and/or defects or limited capacities of the protein quality control systems, nascent proteins may become misfolded and fail to exit the ER. If not cleared efficiently, the progressive accumulation of misfolded proteins within the ER may result in the formation of toxic protein aggregates, leading to the so-called "ER storage diseases". In this review, we first summarize our current understanding of the protein folding and quality control networks in the ER, including chaperones, unfolded protein response (UPR), ER-associated protein degradation (ERAD), and ER-selective autophagy (ER-phagy). We then survey recent research progress on a few ER storage diseases, with a focus on the role of ER quality control in the disease etiology, followed by a discussion on outstanding questions and emerging concepts in the field.

Keywords: ER; ER storage disease; ER-associated protein degradation; ER-phagy; chaperone; protein aggregate; unfolded protein response

DOI: https://doi.org/10.3390/cells10123337