bims-lycede Biomed News
on Lysosome-dependent cell death
Issue of 2025–01–19
two papers selected by
Sofía Peralta, Universidad Nacional de Cuyo
  1. Transcription factor EB (TFEB) activity increases resistance of TNBC stem cells to metabolic stress.
  2. Tracking Chaperone-Mediated Autophagy Flux with a pH-Resistant Fluorescent Reporter.
  1. Life Sci Alliance. 2025 Mar;pii: e202302259. [Epub ahead of print]8(3):
    Transcription factor EB (TFEB) activity increases resistance of TNBC stem cells to metabolic stress.
    Milad Soleimani, Mark Duchow, Ria Goyal, Alexander Somma, Tamer S Kaoud, Kevin N Dalby, Jeanne Kowalski, S Gail Eckhardt, Carla Van Den Berg.
      Breast cancer stem cells (CSCs) are difficult to therapeutically target, but continued efforts are critical given their contribution to tumor heterogeneity and treatment resistance in triple-negative breast cancer. CSC properties are influenced by metabolic stress, but specific mechanisms are lacking for effective drug intervention. Our previous work on TFEB suggested a key function in CSC metabolism. Indeed, TFEB knockdown (KD) inhibited mammosphere formation in vitro and tumor initiation/growth in vivo. These phenotypic effects were accompanied by a decline in CD44high/CD24low cells. Glycolysis inhibitor 2-deoxy-D-glucose (2-DG) induced TFEB nuclear translocation, indicative of TFEB transcriptional activity. TFEB KD blunted, whereas TFEB (S142A) augmented 2-DG-driven unfolded protein response (UPR) mediators, notably BiP/HSPA5 and CHOP. Like TFEB KD, silencing BiP/HSPA5 inhibited CSC self-renewal, suggesting that TFEB augments UPR-related survival. Further studies showed that TFEB KD attenuated 2-DG-directed autophagy, suggesting a mechanism whereby TFEB protects CSCs against 2-DG-induced stress. Our data indicate that TFEB modulates CSC metabolic stress response via autophagy and UPR. These findings reveal the novel role of TFEB in regulating CSCs during metabolic stress in triple-negative breast cancer.
    DOI:  https://doi.org/10.26508/lsa.202302259
  2. Int J Mol Sci. 2024 Dec 24. pii: 17. [Epub ahead of print]26(1):
    Tracking Chaperone-Mediated Autophagy Flux with a pH-Resistant Fluorescent Reporter.
    Ruotong Qi, Xingyi Chen, Zihan Li, Zheng Wang, Zhuohui Xiao, Xinyue Li, Yuanyuan Han, Hongfei Zheng, Yanjun Wu, Yi Xu.
      Chaperone-mediated autophagy (CMA) is a selective autophagic pathway responsible for degrading cytoplasmic proteins within lysosomes. Monitoring CMA flux is essential for understanding its functions and molecular mechanisms but remains technically complex and challenging. In this study, we developed a pH-resistant probe, KFERQ-Gamillus, by screening various green fluorescent proteins. This probe is activated under conditions known to induce CMA, such as serum starvation, and relies on LAMP2A and the KFERQ motif for lysosomal localization and degradation, demonstrating its specificity for the CMA pathway. It enables the detection of CMA activity in living cells through both microscopy and image-based flow cytometry. Additionally, we created a dual-reporter system, KFERQ-Gamillus-Halo, by integrating KFERQ-Gamillus with the Halo-tag system. This probe not only distinguishes between protein synthesis and degradation but also facilitates the detection of intracellular CMA flux via immunoblotting and the rapid assessment of CMA activity using flow cytometry. Together, the KFERQ-Gamillus-Halo probe provides quantitative and time-resolved monitoring for CMA activity and flux in living cells. This tool holds promising potential for high-throughput screening and biomedical research related to CMA.
    Keywords:  Gamillus; chaperone-mediated autophagy; flux; halo
    DOI:  https://doi.org/10.3390/ijms26010017
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