bims-lymeca 2022-12-25 papers

bims-lymeca

Biomed News

on Lysosome metabolism in cancer

Issue of 2022–12–25
eight papers selected by
Harilaos Filippakis, University of New England

mTORC1 regulates a lysosome-dependent adaptive shift in intracellular lipid species.
The endo-lysosomal regulatory protein BLOC1S1 modulates hepatic lysosomal content and lysosomal lipolysis.
Ursolic Acid Impairs Cellular Lipid Homeostasis and Lysosomal Membrane Integrity in Breast Carcinoma Cells.
Toosendanin Induces Hepatocyte Damage by Inhibiting Autophagic Flux via TFEB-Mediated Lysosomal Dysfunction.
mTORC1 takes control of lysosomal lipid breakdown.
mTOR Signaling Network in Cell Biology and Human Disease.
Membrane protein trafficking in the anti-tumor immune response: work of endosomal-lysosomal system.
Visualizing Mitophagy with Fluorescent Dyes for Mitochondria and Lysosome.

Nat Metab. 2022 Dec;4(12): 1792-1811

mTORC1 regulates a lysosome-dependent adaptive shift in intracellular lipid species.

Aaron M Hosios, Meghan E Wilkinson, Molly C McNamara, Krystle C Kalafut, Margaret E Torrence, John M Asara, Brendan D Manning.

The mechanistic target of rapamycin complex 1 (mTORC1) senses and relays environmental signals from growth factors and nutrients to metabolic networks and adaptive cellular systems to control the synthesis and breakdown of macromolecules; however, beyond inducing de novo lipid synthesis, the role of mTORC1 in controlling cellular lipid content remains poorly understood. Here we show that inhibition of mTORC1 via small molecule inhibitors or nutrient deprivation leads to the accumulation of intracellular triglycerides in both cultured cells and a mouse tumor model. The elevated triglyceride pool following mTORC1 inhibition stems from the lysosome-dependent, but autophagy-independent, hydrolysis of phospholipid fatty acids. The liberated fatty acids are available for either triglyceride synthesis or β-oxidation. Distinct from the established role of mTORC1 activation in promoting de novo lipid synthesis, our data indicate that mTORC1 inhibition triggers membrane phospholipid trafficking to the lysosome for catabolism and an adaptive shift in the use of constituent fatty acids for storage or energy production.

DOI: https://doi.org/10.1038/s42255-022-00706-6
Biochem Biophys Res Commun. 2022 Dec 14. pii: S0006-291X(22)01703-X. [Epub ahead of print]642 1-10

The endo-lysosomal regulatory protein BLOC1S1 modulates hepatic lysosomal content and lysosomal lipolysis.

Kaiyuan Wu, Jizhong Zou, Michael N Sack.

  BLOC1S1 is a common component of BLOC and BORC multiprotein complexes which play distinct roles in endosome and lysosome biology. Recent human mutations in BLOC1S1 associate with juvenile leukodystrophy. As leukodystrophy is linked to perturbed lysosomal lipid storage we explored whether BLOC1S1 itself modulates this biology. Given the central role of the liver in lipid storage, our investigations were performed in hepatocyte specific liver bloc1s1 knockout (LKO) mice and in human hepatocyte-like lines (HLCs) derived from inducible pluripotential stem cells (iPSCs) from a juvenile leukodystrophy subject's with bloc1s1 mutations and from isogenic corrected iPSCs. Here we show that hepatocyte lipid stores are diminished in parallel with increased lysosomal content, increased lysosomal lipid uptake and lipolysis in LKO mice. The lysosomal lipolysis program was independent of macro- and chaperone-mediated lipophagy but dependent on cellular lysosome content. In parallel, genetic induction of lysosomal biogenesis in a transformed hepatocyte cell line replicated depletion of intracellular lipid stores. Interestingly bloc1s1 mutant and isogenic corrected HLCs both showed normal lysosomal enzyme activity. However, relative to the isogenic corrected HLCs, mutant bloc1s1 HLCs showed reduced lysosomal content and increased lipid storage. Together these data show distinct phenotypes in human mutant HLCs compared to murine knockout cells. At the same time, human blcs1s1 mutation and murine hepatocyte bloc1s1 depletion disrupt lysosome content and the cellular lipid storage. These data support that BLOC1S1 modulates lysosome content and lipid handling independent of autophagy and show that lysosomal lipolysis is dependent on the cellular content of functional lysosomes.

Keywords:  BLOC1S1; Hepatic lipid droplets; Lysosomal lipolysis; Lysosome

DOI:  https://doi.org/10.1016/j.bbrc.2022.12.038
Cells. 2022 Dec 16. pii: 4079. [Epub ahead of print]11(24):

Ursolic Acid Impairs Cellular Lipid Homeostasis and Lysosomal Membrane Integrity in Breast Carcinoma Cells.

Ditte L Fogde, Cristina P R Xavier, Kristina Balnytė, Lya K K Holland, Kamilla Stahl-Meyer, Christoffel Dinant, Elisabeth Corcelle-Termeau, Cristina Pereira-Wilson, Kenji Maeda, Marja Jäättelä.

  Cancer is one of the leading causes of death worldwide, thus the search for new cancer therapies is of utmost importance. Ursolic acid is a naturally occurring pentacyclic triterpene with a wide range of pharmacological activities including anti-inflammatory and anti-neoplastic effects. The latter has been assigned to its ability to promote apoptosis and inhibit cancer cell proliferation by poorly defined mechanisms. In this report, we identify lysosomes as the essential targets of the anti-cancer activity of ursolic acid. The treatment of MCF7 breast cancer cells with ursolic acid elevates lysosomal pH, alters the cellular lipid profile, and causes lysosomal membrane permeabilization and leakage of lysosomal enzymes into the cytosol. Lysosomal membrane permeabilization precedes the essential hallmarks of apoptosis placing it as an initial event in the cascade of effects induced by ursolic acid. The disruption of the lysosomal function impairs the autophagic pathway and likely partakes in the mechanism by which ursolic acid kills cancer cells. Furthermore, we find that combining treatment with ursolic acid and cationic amphiphilic drugs can significantly enhance the degree of lysosomal membrane permeabilization and cell death in breast cancer cells.

Keywords:  autophagy; cancer; cationic amphiphilic drugs; cell death; lysosomal membrane permeabilization; ursolic acid

DOI:  https://doi.org/10.3390/cells11244079
Pharmaceuticals (Basel). 2022 Dec 03. pii: 1509. [Epub ahead of print]15(12):

Toosendanin Induces Hepatocyte Damage by Inhibiting Autophagic Flux via TFEB-Mediated Lysosomal Dysfunction.

Li Luo, Yonghong Liang, Yuanyuan Fu, Zhiyuan Liang, Jinfen Zheng, Jie Lan, Feihai Shen, Zhiying Huang.

  Toosendanin (TSN) is a triterpenoid from the fruit or bark of Melia toosendan Sieb et Zucc, which has clear antitumor and insecticidal activities, but it possesses limiting hepatotoxicity in clinical application. Autophagy is a degradation and recycling mechanism to maintain cellular homeostasis, and it also plays an essential role in TSN-induced hepatotoxicity. Nevertheless, the specific mechanism of TSN on autophagy-related hepatotoxicity is still unknown. The hepatotoxicity of TSN in vivo and in vitro was explored in this study. It was found that TSN induced the upregulation of the autophagy-marker microtubule-associated proteins 1A/1B light chain 3B (LC3B) and P62, the accumulation of autolysosomes, and the inhibition of autophagic flux. The middle and late stages of autophagy were mainly studied. The data showed that TSN did not affect the fusion of autophagosomes and lysosomes but significantly inhibited the acidity, the degradation capacity of lysosomes, and the expression of hydrolase cathepsin B (CTSB). The activation of autophagy could alleviate TSN-induced hepatocyte damage. TSN inhibited the expression of transcription factor EB (TFEB), which is a key transcription factor for many genes of autophagy and lysosomes, such as CTSB, and overexpression of TFEB alleviated the autophagic flux blockade caused by TSN. In summary, TSN caused hepatotoxicity by inhibiting TFEB-lysosome-mediated autophagic flux and activating autophagy by rapamycin (Rapa), which could effectively alleviate TSN-induced hepatotoxicity, indicating that targeting autophagy is a new strategy to intervene in the hepatotoxicity of TSN.

Keywords:  TFEB; autophagic flux; autophagy; hepatotoxicity; lysosome; toosendanin (TSN)

DOI:  https://doi.org/10.3390/ph15121509
Nat Metab. 2022 Dec;4(12): 1620-1622

mTORC1 takes control of lysosomal lipid breakdown.

Laura Tribouillard, Mathieu Laplante.

DOI: https://doi.org/10.1038/s42255-022-00702-w
Int J Mol Sci. 2022 Dec 18. pii: 16142. [Epub ahead of print]23(24):

mTOR Signaling Network in Cell Biology and Human Disease.

Jane J Yu, Elena A Goncharova.

The mechanistic target of rapamycin (mTOR) is a serine/threonine protein kinase that regulates multiple processes, including gene transcription, protein synthesis, ribosome biogenesis, autophagy, cell metabolism, and cell growth [...].

DOI: https://doi.org/10.3390/ijms232416142
Cancer Cell Int. 2022 Dec 17. 22(1): 413

Membrane protein trafficking in the anti-tumor immune response: work of endosomal-lysosomal system.

Yan Jin, Zhifeng Deng, Ting Zhu.

  Immunotherapy has changed the treatment landscape for multiple cancer types. In the recent decade, great progress has been made in immunotherapy, including immune checkpoint inhibitors, adoptive T-cell therapy, and cancer vaccines. ICIs work by reversing tumor-induced immunosuppression, resulting in robust activation of the immune system and lasting immune responses. Whereas, their clinical use faces several challenges, especially the low response rate in most patients. As an increasing number of studies have focused on membrane immune checkpoint protein trafficking and degradation, which interferes with response to immunotherapy, it is necessary to summarize the mechanism regulating those transmembrane domain proteins translocated into the cytoplasm and degraded via lysosome. In addition, other immune-related transmembrane domain proteins such as T-cell receptor and major histocompatibility are associated with neoantigen presentation. The endosomal-lysosomal system can also regulate TCR and neoantigen-MHC complexes on the membrane to affect the efficacy of adoptive T-cell therapy and cancer vaccines. In conclusion, we discuss the process of surface delivery, internalization, recycling, and degradation of immune checkpoint proteins, TCR, and neoantigen-MHC complexes on the endosomal-lysosomal system in biology for optimizing cancer immunotherapy.

Keywords:  Anti-tumor immune; Endocytosis; Immune checkpoint; Recycle; Traffic

DOI:  https://doi.org/10.1186/s12935-022-02805-6
J Vis Exp. 2022 11 30.

Visualizing Mitophagy with Fluorescent Dyes for Mitochondria and Lysosome.

Bilin Liu, Anqi Li, Yuan Qin, Lei Chen, Meng Gao, Guohua Gong.

Mitochondria, being the powerhouses of the cell, play important roles in bioenergetics, free radical generation, calcium homeostasis, and apoptosis. Mitophagy is the primary mechanism of mitochondrial quality control and is generally studied using microscopic observation, however in vivo mitophagy assays are difficult to perform. Evaluating mitophagy by imaging live organelles is an alternative and necessary method for mitochondrial research. This protocol describes the procedures for using the cell-permeant green-fluorescent mitochondria dye MitoTracker Green and the red-fluorescent lysosome dye LysoTracker Red in live cells, including the loading of the dyes, visualization of the mitochondria and the lysosome, and expected outcomes. Detailed steps for the evaluation of mitophagy in live cells, as well as technical notes about microscope software settings, are also provided. This method can help researchers observe mitophagy using live-cell fluorescent microscopy. In addition, it can be used to quantify mitochondria and lysosomes and assess mitochondrial morphology.

DOI: https://doi.org/10.3791/64647