bims-apauto 2022-06-19 papers

Issue of 2022‒06‒19
five papers selected by
Su Hyun Lee
Seoul National University

Autophagy. 2022 Jun 14. 1-3

CCT2, a newly identified aggrephagy receptor in mammals, specifically mediates the autophagic clearance of solid protein aggregates.

Zhihai Zhang, Daniel J Klionsky.

Protein aggregates have a strong correlation with the pathogenesis of multiple human pathologies represented by neurodegenerative diseases. One type of selective autophagy, known as aggrephagy, can selectively degrade protein aggregates. A recent study from Ge lab reported the TRiC subunit CCT2 (chaperonin containing TCP1 subunit 2) as the first identified specific aggrephagy receptor in mammals. The switch of CCT2's role from a chaperonin to a specific aggrephagy receptor is achieved by CCT2 monomer formation. CCT2 functions independently of ubiquitin and the TRiC complex to facilitate the autophagic clearance of solid protein aggregates. This study provides the intriguing possibility that CCT2, as a specific aggrephagy receptor, might be an important target for the treatment of various diseases associated with protein aggregation.

Keywords: Aggrephagy; CCT2; autophagy; chaperonin TRiC subunit; protein aggregation; solid protein aggregates

DOI: https://doi.org/10.1080/15548627.2022.2083305

Autophagy. 2022 Jun 16.

Autophagy in PDGFRA+ mesenchymal cells is required for intestinal homeostasis and mammalian survival.

Yang Yang, Eileen White.

Macroautophagy/autophagy defects are a risk factor for intestinal bowel disease (IBD), but the mechanism remains unclear. We previously demonstrated that conditional whole-body deletion of the essential Atg7 (autophagy related 7) gene in adult mice (atg7Δ/Δ) causes specific tissue damage and shortens lifespan to three months primarily due to neurodegeneration with surprisingly no disturbing effects on the intestine. In contrast, we recently found that conditional whole-body deletion of other essential autophagy genes, Atg5 or Rb1cc1/Fip200 (atg5Δ/Δ or rb1cc1Δ/Δ), cause death within five days due to rapid inhibition of autophagy, elimination of intestinal stem cells, and loss of barrier function in the ileum. atg5Δ/Δ mice lose PDGFRA/PDGFRα+ mesenchymal cells (PMCs) and WNT signaling essential for stem cell renewal. Depletion of aspartate and nucleotides in atg5Δ/Δ ileum was revealed by novel mass-spectrometry imaging (MALDI-MSI), consistent with metabolic insufficiency underlying PMCs loss. The difference in the autophagy gene knockout phenotypes is likely due to distinct kinetics of autophagy loss because gradual whole-body atg5 deletion extends lifespan, phenocopying deletion of Atg7 or Atg12. Therefore, we established that autophagy is required for ileum PMC metabolism, stem cell maintenance and mammalian survival. PMC loss caused by autophagy deficiency may therefore contribute to IBD.

Keywords: Autophagy; IBD; PDGFRα+ mesenchymal cells; WNT signaling; intestinal stem cells

DOI: https://doi.org/10.1080/15548627.2022.2090694

Nat Commun. 2022 Jun 17. 13(1): 3486

FUNDC2 promotes liver tumorigenesis by inhibiting MFN1-mediated mitochondrial fusion.

Shuaifeng Li, Shixun Han, Qi Zhang, Yibing Zhu, Haitao Zhang, Junli Wang, Yang Zhao, Jianhui Zhao, Lin Su, Li Li, Dawang Zhou, Cunqi Ye, Xin-Hua Feng, Tingbo Liang, Bin Zhao.

Mitochondria generate ATP and play regulatory roles in various cellular activities. Cancer cells often exhibit fragmented mitochondria. However, the underlying mechanism remains elusive. Here we report that a mitochondrial protein FUN14 domain containing 2 (FUNDC2) is transcriptionally upregulated in primary mouse liver tumors, and in approximately 40% of human hepatocellular carcinoma (HCC). Importantly, elevated FUNDC2 expression inversely correlates with patient survival, and its knockdown inhibits liver tumorigenesis in mice. Mechanistically, the amino-terminal region of FUNDC2 interacts with the GTPase domain of mitofusin 1 (MFN1), thus inhibits its activity in promoting fusion of outer mitochondrial membrane. As a result, loss of FUNDC2 leads to mitochondrial elongation, decreased mitochondrial respiration, and reprogrammed cellular metabolism. These results identified a mechanism of mitochondrial fragmentation in cancer through MFN1 inhibition by FUNDC2, and suggested FUNDC2 as a potential therapeutic target of HCC.

DOI: https://doi.org/10.1038/s41467-022-31187-6

Front Oncol. 2022 ;12 920999

UNC13B Promote Arsenic Trioxide Resistance in Chronic Lymphoid Leukemia Through Mitochondria Quality Control.

Xiao-Bo Wang, Li-Hua Yuan, Le-Ping Yan, Yong-Bin Ye, Bo Lu, Xiaojun Xu.

In clinical practice, arsenic trioxide can be used to treat a subset of R/R CML patients, but resistance tends to reappear quickly. We designed an experiment to study arsenic trioxide resistance in K-562 cells. Previously, we identified the UNC13B gene as potentially responsible for arsenic trioxide resistance in K-562 cells via gene chip screening followed by high-content screening. We aimed to investigate the role and mechanism of the UNC13B gene in K-562 cells, an arsenic trioxide-resistant chronic myeloid leukemia cell line. In vitro lentiviral vector-mediated UNC13B siRNA transfection was performed on K-562 cells. The roles of UNC13B in cell proliferation, apoptosis and cell cycle pathways, and colony formation were analyzed by CCK-8 assay, fluorescence-activated cell sorting, and soft agar culture, respectively. Gene chip screening was used to define the possible downstream pathways of UNC13B. Western blot was performed to further validate the possible genes mediated by UNC13B for arsenic trioxide resistance in patients with chronic myeloid leukemia. UNC13B downregulation significantly inhibited growth, promoted apoptosis, decreased colony formation, reduced the duration of the G1 phase, and increased the duration of the S phase of K-562 cells. Western blot results confirmed that UNC13B may modulate the apoptosis and proliferation of arsenic trioxide-resistant chronic myeloid leukemia cells through the mediation of MAP3K7, CDK4, and PINK1. UNC13B is a potential therapeutic target for patients with arsenic trioxide-resistant chronic myeloid leukemia.

Keywords: UNC13B; arsenic trioxide; chronic myeloid leukemia; drug resistance; mitochondria

DOI: https://doi.org/10.3389/fonc.2022.920999

EMBO Mol Med. 2022 Jun 13. e16171

Targeting the Leukemic stem cell protein machinery by inhibition of mitochondrial pyrimidine synthesis.

Elisa Donato, Andreas Trumpp.

Acute Myeloid Leukemia is one of the most aggressive blood cancers with a high frequency of relapse. While standard chemotherapy is able to target rapidly proliferating immature blasts, it fails to eradicate slowly proliferating Leukemic Stem Cells. Therefore, new therapeutic strategies that efficiently target LSCs are urgently needed. Recent studies suggest that LSCs have particular metabolic vulnerabilities, which would open the possibility of a therapeutic window with limited off-target effects on the normal hematopoietic system. In this issue of EMBO Molecular Medicine, So and colleagues investigate the mechanism of action of AG636, a new potent inhibitor of de novo pyrimidine synthesis, and discovered an unexpected link to AML protein translation essential for LSC function.

DOI: https://doi.org/10.15252/emmm.202216171