bims-lymeca 2023-06-04 papers

Issue of 2023‒06‒04
three papers selected by
Harilaos Filippakis
University of New England

Front Nutr. 2023 ;10 1124678

A metabolic shift toward glycolysis enables cancer cells to maintain survival upon concomitant glutamine deprivation and V-ATPase inhibition.

Florian Lengauer, Franz Geisslinger, Antje Gabriel, Karin von Schwarzenberg, Angelika M Vollmar, Karin Bartel.

It is widely known that most cancer cells display an increased reliance on glutaminolysis to sustain proliferation and survival. Combining glutamine deprivation with additional anti-cancer therapies is an intensively investigated approach to increase therapeutic effectiveness. In this study, we examined a combination of glutamine deprivation by starvation or pharmacological tools, with the anti-cancer agent archazolid, an inhibitor of the lysosomal V-ATPase. We show that glutamine deprivation leads to lysosomal acidification and induction of pro-survival autophagy, which could be prevented by archazolid. Surprisingly, a combination of glutamine deprivation with archazolid did not lead to synergistic induction of cell death or reduction in proliferation. Investigating the underlying mechanisms revealed elevated expression and activity of amino acid transporters SLC1A5, SLC38A1 upon starvation, whereas archazolid had no additional effect. Furthermore, we found that the export of lysosomal glutamine derived from exogenous sources plays no role in the phenotype as knock-down of SLC38A7, the lysosomal glutamine exporter, could not increase V-ATPase inhibition-induced cell death or reduce proliferation. Analysis of the cellular metabolic phenotype revealed that glutamine deprivation led to a significant increase in glycolytic activity, indicated by an elevated glycolytic capacity and reserve, when V-ATPase function was inhibited concomitantly. This was confirmed by increased glutamine uptake, augmented lactate production, and an increase in hexokinase activity. Our study, therefore, provides evidence, that glutamine deprivation induces autophagy, which can be prevented by simultaneous inhibition of V-ATPase function. However, this does not lead to a therapeutic benefit, as cells are able to circumvent cell death and growth inhibition by a metabolic shift toward glycolysis.

Keywords: V-ATPase; cancer; cancer metabolism; glutamine; glycolysis

DOI: https://doi.org/10.3389/fnut.2023.1124678

Mol Biol Rep. 2023 May 29.

Intermittent inhibition of FYVE finger-containing phosphoinositide kinase induces melanosome degradation in B16F10 melanoma cells.

Kyoka Kawaguchi, Miyu Watanabe, Saho Furukawa, Kenichi Koga, Hiromitsu Kanamori, Mitsushi J Ikemoto, Shigeo Takashima, Miwa Maeda, Kentaro Oh-Hashi, Yoko Hirata, Kyoji Furuta, Hiroshi Takemori.

BACKGROUND: Melanosomes are lysosome-related organelles that contain melanogenic factors and synthesize melanin as they mature. FYVE finger-containing phosphoinositide kinase (PIKfyve) regulates late endosome and lysosome morphology, vesicle trafficking, and autophagy. In melanocytes, PIKfyve inhibition has been reported to induce hypopigmentation due to impairments in the metabolism of early-stage melanosomes.METHODS AND RESULTS: Here, we report a new type of melanosome metabolism: post-PIKfyve inhibition, which was found during the characterization of the endosome/lysosome fluoroprobe GIF-2250. In B16F10 mouse melanoma cells, GIF-2250 highlighted vesicles positive for lysosomal-associated membrane protein 1 (lysosome marker) and other endosome/lysosome markers (CD63 and Rab7/9). When cells were continuously treated with PIKfyve inhibitors, intracellular vacuoles formed, while GIF-2250 fluorescence signals diminished and were diffusely distributed in the vacuoles. After removal of the PIKfyve inhibitors, the GIF-2250 signal intensity was restored, and some GIF-2250-positive vesicles wrapped the melanosomes, which spun at high speed. In addition, intermittent PIKfyve inhibition caused melanin diffusion in the vacuoles and possible leakage into the cytoplasmic compartments, and melanosome degradation was detected by a transmission electron microscope. Melanosome degradation was accompanied by decreased levels of melanin synthesis enzymes and increased levels of the autophagosome maker LC3BII, which is also associated with early melanosomes. However, the protein levels of p62, which is degraded during autophagy, were increased, suggesting an impairment in autophagy flux during intermittent PIKfyve inhibition. Moreover, the autophagy inhibitor 3-methyladenine does not affect these protein levels, suggesting that the melanosome degradation by the intermittent inhibition of PIKfyve is not mediated by canonical autophagy.
CONCLUSIONS: In conclusion, disturbance of PIKfyve activity induces melanosome degradation in a canonical autophagy-independent manner.

Keywords: Autophagy; Endosome; Lysosome; Melanosome; PIKfyve

DOI: https://doi.org/10.1007/s11033-023-08536-9

Nat Commun. 2023 May 29. 14(1): 3086

Multi-omic approach characterises the neuroprotective role of retromer in regulating lysosomal health.

James L Daly, Chris M Danson, Philip A Lewis, Lu Zhao, Sara Riccardo, Lucio Di Filippo, Davide Cacchiarelli, Daehoon Lee, Stephen J Cross, Kate J Heesom, Wen-Cheng Xiong, Andrea Ballabio, James R Edgar, Peter J Cullen.

Retromer controls cellular homeostasis through regulating integral membrane protein sorting and transport and by controlling maturation of the endo-lysosomal network. Retromer dysfunction, which is linked to neurodegenerative disorders including Parkinson's and Alzheimer's diseases, manifests in complex cellular phenotypes, though the precise nature of this dysfunction, and its relation to neurodegeneration, remain unclear. Here, we perform an integrated multi-omics approach to provide precise insight into the impact of Retromer dysfunction on endo-lysosomal health and homeostasis within a human neuroglioma cell model. We quantify widespread changes to the lysosomal proteome, indicative of broad lysosomal dysfunction and inefficient autophagic lysosome reformation, coupled with a reconfigured cell surface proteome and secretome reflective of increased lysosomal exocytosis. Through this global proteomic approach and parallel transcriptomic analysis, we provide a holistic view of Retromer function in regulating lysosomal homeostasis and emphasise its role in neuroprotection.

DOI: https://doi.org/10.1038/s41467-023-38719-8