bims-ershed 2022-12-25 papers

Issue of 2022‒12‒25
four papers selected by
Matías Eduardo González Quiroz
Worker’s Hospital

Am J Pathol. 2022 Dec 16. pii: S0002-9440(22)00397-2. [Epub ahead of print]

Mitochondria and Endoplasmic Reticulum Stress in Retinal Organoids from Vision Loss Patients.

Eun-Jin Lee, Monica Sophia Diaz-Aguilar, Hyejung Min, Jihee Choi, Diego Adrian Valdez Duran, Julia M Grandjean, R Luke Wiseman, Heike Kroeger, Jonathan H Lin.

Activating transcription factor 6 (ATF6), a key regulator of the unfolded protein response (UPR), is required for endoplasmic reticulum (ER) function and protein homeostasis. Variants of ATF6 that abrogate transcriptional activity cause morphologic and molecular defects in cones manifesting clinically as the human vision loss disease achromatopsia (ACHM). ATF6 is expressed in all retinal cells. However, the effect of disease-associated ATF6 variants on other retinal cell types remains unclear. To investigate this question, we analyzed bulk-RNA-seq transcriptomes from retinal-organoids generated from ACHM patients carrying homozygous loss-of-function ATF6 variants. We identified marked dysregulation in mitochondrial respiratory complex gene expression and disrupted mitochondrial morphology in ACHM retinal organoids, indicating that loss of ATF6 leads to previously unappreciated mitochondrial defects in the retina. Next, we compared gene expression from control and ACHM retinal organoids with transcriptome profiles of 7 major retinal cell types generated from recent single-cell transcriptomic maps of non-diseased human retina. Our analysis revealed pronounced down-regulation of cone genes and up-regulation in Müller glia genes, with no significant effects on other retinal cells. Overall, our analysis of ACHM patient retinal organoids identifies new cellular and molecular phenotypes in addition to cone dysfunction: activation of Müller cells, increased ER stress, and disrupted mitochondrial structure and elevated respiratory chain activity gene expression.

DOI: https://doi.org/10.1016/j.ajpath.2022.12.002

Int J Mol Sci. 2022 Dec 18. pii: 16162. [Epub ahead of print]23(24):

Allosteric Inhibition of c-Abl to Induce Unfolded Protein Response and Cell Death in Multiple Myeloma.

Hideki Kosako, Yusuke Yamashita, Shuhei Morita, Sadahiro Iwabuchi, Shinichi Hashimoto, Taka-Aki Matsuoka, Takashi Sonoki, Shinobu Tamura.

Endoplasmic reticulum stress activates inositol-requiring enzyme 1α (IRE1α) and protein kinase, R-like endoplasmic reticulum kinase (PERK), the two principal regulators of the unfolded protein response (UPR). In multiple myeloma, adaptive IRE1α signaling is predominantly activated and regulates cell fate along with PERK. Recently, we demonstrated that GNF-2, an allosteric c-Abl inhibitor, rheostatically enhanced IRE1α activity and induced apoptosis through c-Abl conformational changes in pancreatic β cells. Herein, we analyzed whether the pharmacological modulation of c-Abl conformation resulted in anti-myeloma effects. First, we investigated the effects of GNF-2 on IRE1α activity and cell fate, followed by an investigation of the anti-myeloma effects of asciminib, a new allosteric c-Abl inhibitor. Finally, we performed RNA sequencing to characterize the signaling profiles of asciminib. We observed that both GNF-2 and asciminib decreased cell viability and induced XBP1 mRNA splicing in primary human myeloma cells and myeloma cell lines. RNA sequencing identified the induction of UPR- and apoptosis-related genes by asciminib. Asciminib re-localized c-Abl to the endoplasmic reticulum, and its combination with a specific IRE1α inhibitor, KIRA8, enhanced cell death with the reciprocal induction of CHOP mRNA expression. Together, the allosteric inhibition of c-Abl-activated UPR with anti-myeloma effects; this could be a novel therapeutic target for multiple myeloma.

Keywords: GNF-2; IRE1α; asciminib; c-Abl; multiple myeloma; unfolded protein response

DOI: https://doi.org/10.3390/ijms232416162

Apoptosis. 2022 Dec 19.

The unfolded protein response (UPR) pathway: the unsung hero in breast cancer management.

Arunita Patra, Arghya Adhikary, Swatilekha Ghosh.

Tumor cells always have the need to produce an increased amount of proteins in the cells. This elevated amount of proteins increases the pressure on the organelles of the cell such as the endoplasmic reticulum and compels it to increase its protein folding efficiency. However, it is by a matter of fact, that the amount of proteins synthesized outweighs the protein folding capacity of the ER which in turn switches on the UPR pathway by activating the three major molecular sensors and other signaling cascades, which helps in cell survival instead of instant death. However, if this pathway is active for a prolonged period of time the tumor cells heads toward apoptosis. Again, interestingly this is not the same as in case of non- tumorogenic cells. This exhibit a straight natural pathway for tumor cells-specific destruction which has a great implication in today's world where hormone therapies and chemo-therapies are non-effective for various types of breast cancer, a major type being Triple Negative Breast Cancer. Thus a detailed elucidation of the molecular involvement of the UPR pathway in breast cancer may open new avenues for management and attract novel chemotherapeutic targets providing better hopes to patients worldwide.

Keywords: Apoptosis; Breast cancer; ER Stress; GRP78; UPR sensors

DOI: https://doi.org/10.1007/s10495-022-01803-3