bims-lymeca Biomed News
on Lysosome metabolism in cancer
Issue of 2022‒01‒16
twenty-six papers selected by
Charilaos Filippakis
Harvard University

  1. Mol Biomed. 2021 Feb 20. 2(1): 5
      Metabolic reprogramming with heterogeneity is a hallmark of cancer and is at the basis of malignant behaviors. It supports the proliferation and metastasis of tumor cells according to the low nutrition and hypoxic microenvironment. Tumor cells frantically grab energy sources (such as glucose, fatty acids, and glutamine) from different pathways to produce a variety of biomass to meet their material needs via enhanced synthetic pathways, including aerobic glycolysis, glutaminolysis, fatty acid synthesis (FAS), and pentose phosphate pathway (PPP). To survive from stress conditions (e.g., metastasis, irradiation, or chemotherapy), tumor cells have to reprogram their metabolism from biomass production towards the generation of abundant adenosine triphosphate (ATP) and antioxidants. In addition, cancer cells remodel the microenvironment through metabolites, promoting an immunosuppressive microenvironment. Herein, we discuss how the metabolism is reprogrammed in cancer cells and how the tumor microenvironment is educated via the metabolic products. We also highlight potential metabolic targets for cancer therapies.
    Keywords:  Cancer; Heterogeneity; Metabolic reprogramming; Targeted therapy; Tumor microenvironment
  2. Mol Biol Cell. 2022 Jan 12. mbcE21060309
      Transcriptional factor EB (TFEB) is a master regulator of genes required for autophagy and lysosomal function. The nuclear localization of TFEB is blocked by the mechanistic target of rapamycin complex 1 (mTORC1)-dependent phosphorylation of TFEB at multiple sites including Ser-211. Here we show that inhibition of PIKfyve, which produces phosphatidylinositol 3,5-bisphosphate on endosomes and lysosomes, causes a loss of Ser-211 phosphorylation and concomitant nuclear localization of TFEB. We found that while mTORC1 activity toward S6K1, as well as other major mTORC1 substrates, is not impaired, PIKfyve inhibition specifically impedes the interaction of TFEB with mTORC1. This suggests that mTORC1 activity on TFEB is selectively inhibited due to loss of mTORC1 access to TFEB. In addition, we found that TFEB activation during inhibition of PIKfyve relies on the ability of protein phosphatase 2A (PP2A) but not calcineurin/PPP3, to dephosphorylate TFEB Ser-211. Thus, when PIKfyve is inhibited, PP2A is dominant over mTORC1 for control of TFEB phosphorylation at Ser-S211. Together these findings suggest that mTORC1 and PP2A have opposing roles on TFEB via phosphorylation and dephosphorylation of Ser-211, respectively, and further, that PIKfyve inhibits TFEB activity by facilitating mTORC1-dependent phosphorylation of TFEB.
  3. J Exp Clin Cancer Res. 2022 Jan 08. 41(1): 16
      BACKGROUND: KRAS is the predominant oncogene mutated in pancreatic ductal adenocarcinoma (PDAC), the fourth cause of cancer-related deaths worldwide. Mutant KRAS-driven tumors are metabolically programmed to support their growth and survival, which can be used to identify metabolic vulnerabilities. In the present study, we aimed to understand the role of extracellularly derived fatty acids in KRAS-driven pancreatic cancer.METHODS: To assess the dependence of PDAC cells on extracellular fatty acids we employed delipidated serum or RNAi-mediated suppression of ACSL3 (to inhibit the activation and cellular retention of extracellular fatty acids) followed by cell proliferation assays, qPCR, apoptosis assays, immunoblots and fluorescence microscopy experiments. To assess autophagy in vivo, we employed the KrasG12D/+;p53flox/flox;Pdx1-CreERT2 (KPC) mice crossed with Acsl3 knockout mice, and to assess the efficacy of the combination therapy of ACSL3 and autophagy inhibition we used xenografted human cancer cell-derived tumors in immunocompromised mice.
    RESULTS: Here we show that depletion of extracellularly derived lipids either by serum lipid restriction or suppression of ACSL3, triggers autophagy, a process that protects PDAC cells from the reduction of bioenergetic intermediates. Combined extracellular lipid deprivation and autophagy inhibition exhibits anti-proliferative and pro-apoptotic effects against PDAC cell lines in vitro and promotes suppression of xenografted human pancreatic cancer cell-derived tumors in mice. Therefore, we propose lipid deprivation and autophagy blockade as a potential co-targeting strategy for PDAC treatment.
    CONCLUSIONS: Our work unravels a central role of extracellular lipid supply in ensuring fatty acid provision in cancer cells, unmasking a previously unappreciated metabolic vulnerability of PDAC cells.
    Keywords:  Combination therapy; Extracellular lipids; Lipid metabolism; Pancreatic cancer; Tumor metabolic vulnerabilities
  4. Cancer Discov. 2022 Jan 14.
      Metabolic diversity and plasticity in HER2+ brain-tropic breast cancer cells shape metastatic fitness.
  5. J Exp Bot. 2022 Jan 10. pii: erac003. [Epub ahead of print]
      Autophagy is a catabolic process in which cytoplasmic components are delivered to vacuoles or lysosomes for degradation and nutrient recycling. Autophagy-mediated degradation of membrane lipids provides a source of fatty acids for the synthesis of energy-rich, storage lipid esters such as triacylglycerol (TAG). In eukaryotes, storage lipids are packaged into dynamic subcellular organelles, lipid droplets (LDs). In times of energy scarcity, LDs can be degraded via autophagy in a process termed lipophagy to release fatty acids for energy production via fatty acid β-oxidation. On the other hand, emerging evidence suggests that LDs are required for the efficient execution of autophagic processes. Here, we review recent advances in our understanding of metabolic interactions between autophagy and TAG storage and discuss mechanisms of lipophagy. Free fatty acids are cytotoxic due to their detergent-like properties and their incorporation into lipid intermediates that are toxic at high levels, therefore, the third part of this review deals with how cells manage lipotoxic stresses during autophagy-mediated mobilization of fatty acids from LDs and organellar membranes for energy generation.
    Keywords:  autophagy; fatty acid; lipid droplet; lipid homeostasis; lipophagy; lipotoxicity
  6. Cancer Treat Res Commun. 2022 Jan 07. pii: S2468-2942(22)00004-1. [Epub ahead of print]30 100512
      The autophagy pathway is the process whereby cells keep cellular homeostasis and respond to stress via recycling their damaged cellular proteins, organelles, and other cellular components. In the context of cancer, autophagy is a dual-edge sword pro- and anti-tumorigenic role depending on the oncogenic context and stage of tumorigenesis. Cancer cells have a higher dependency on autophagy compared with normal cells because of cellular damages and high demands for energy. The carbon, nitrogen, and molecular oxygen are building blocks for highly proliferative cancer cells which extremely depend on glutaminolysis and aerobic glycolysis; when a cancer cell is restricted to glucose and glutamine, it initiates to activate a stress response pathway using autophagy. Oncogenic tyrosine kinases (OncTKs) and receptor tyrosine kinases (RTKs) activation result in autophagy modulation through activation of the PI3K/AKT/mTORC1 and RAS/MAPK signaling pathways. Targeted inhibition of tyrosine kinases (TKs) and RTKs have recently been considered as cancer therapy but drug resistance and cancer relapse continue to be a major limitation of tyrosine kinase inhibitors (TKIs). Manipulation of autophagy pathway along with TKIs may be a promising strategy to circumvent unknown existing drug-resistance mechanisms that may emerge in a treated patient. In this way, clinical trials are ongoing to modulate autophagy to treat cancer. This review aims to summarize the combination therapy of autophagy affecting compounds with anticancer drugs which target cell signaling pathways, metabolism mechanisms, and epigenetics modification to improve therapeutic efficacy against cancers.
    Keywords:  Autophagy modulation; Cancer therapy; Combination therapy
  7. Cancers (Basel). 2021 Dec 21. pii: 6. [Epub ahead of print]14(1):
      Microtubules are key components of the cytoskeleton of eukaryotic cells. Microtubule dynamic instability together with the "tubulin code" generated by the choice of different α- and β- tubulin isoforms and tubulin post-translational modifications have essential roles in the control of a variety of cellular processes, such as cell shape, cell motility, and intracellular trafficking, that are deregulated in cancer. In this review, we will discuss available evidence that highlights the crucial role of the tubulin code in determining different cancer phenotypes, including metastatic cell migration, drug resistance, and tumor vascularization, and the influence of modulating tubulin-modifying enzymes on cancer cell survival and aggressiveness. We will also discuss the role of post-translationally modified microtubules in autophagy-the lysosomal-mediated cellular degradation pathway-that exerts a dual role in many cancer types, either promoting or suppressing cancer growth. We will give particular emphasis to the role of tubulin post-translational modifications and their regulating enzymes in controlling the different stages of the autophagic process in cancer cells, and consider how the experimental modulation of tubulin-modifying enzymes influences the autophagic process in cancer cells and impacts on cancer cell survival and thereby represents a new and fruitful avenue in cancer therapy.
    Keywords:  acetylation; autophagy; cancer; microtubules; tubulin post-translational modifications; tubulin-modifying enzymes; tyrosination
  8. Cell Calcium. 2022 Jan 06. pii: S0143-4160(22)00011-2. [Epub ahead of print]102 102536
      The lysosome is an important membrane-bound acidic organelle that is regarded as the degradative center as well as multifunctional signaling hub. It digests unwanted macromolecules, damaged organelles, microbes, and other materials derived from endocytosis, autophagy, and phagocytosis. To function properly, the ionic homeostasis and membrane potential of the lysosome are strictly regulated by transporters and ion channels. As the most abundant cation inside the cell, potassium ions (K+) are vital for lysosomal membrane potential and lysosomal calcium (Ca2+) signaling. However, our understanding about how lysosomal K+homeostasis is regulated and what are the functions of K+in the lysosome is very limited. Currently, two lysosomal K+channels have been identified: large-conductance Ca2+-activated K+channel (BK) and transmembrane Protein 175 (TMEM175). In this review, we summarize recent development in our understanding of K+ homeostasis and K+channels in the lysosome. We hope to guide the readers into a more in-depth discussion of lysosomal K+ channels in lysosomal physiology and human diseases.
    Keywords:  BK channel; Lysosome; TMEM175; TRPML1
  9. Cancer Discov. 2022 Jan;12(1): 20-22
      PIK3CA, which encodes the p110α catalytic subunit of PI3Kα, is one of the most frequently genetically activated kinases in solid tumors. In this issue of Cancer Discovery, Song and colleagues report that the related PI3Kα inhibitors taselisib and inavolisib trigger receptor tyrosine kinase (RTK)-dependent degradation of the mutant p110α protein in breast cancer cells that are positive for HER2 RTK, limiting feedback-mediated drug resistance and potentially widening the therapeutic index of PI3Kα inhibition.See related article by Song et al., p. 204.
  10. ACS Appl Bio Mater. 2020 Feb 17. 3(2): 977-985
      Autophagy is well-known as a common cellular response to nanomaterials. As one of the most comprehensively studied carbon-based nanomaterials, fullerene and its derivatives have been reported to bring about autophagic features in various cell lines, but little is known about the role of fullerenol (C60(OH)44) on the modulation of autophagy in human gastric tumor cell line SGC-7901. Fullerenol treatment led to the accumulation of autophagosomes, as evidenced by the increased fluorescent intensity of monodansylcadaverine (MDC) staining cells, an elevated level of LC3 protein, and the observation of auotphagosomes in cytoplasm. Subsequent results of the p62 level demonstrated that the accumulation of autophagosomes resulted from the blockade of autophagic flux rather than the activation of autophagy. Fullerenol disrupted autophagic flux by impairing lysosomal function, including lysosome membrane permeabilization (LMP), alkaline of lysosomes, and reduced activity of capthesin B. Interestingly, fullerenol treatment was noncytotoxic under a nutrient-rich condition. When serum was deprived, cytotoxicity occurred in a concentration- and time-dependent manner, along with massive vacuoles in cytoplasm, a large amount of ROS generation, and finally cell death, which can be ascribed to the disruption of essential autophagy in cells. Taken together, understanding this autophagy-lysosome pathway will shed light on the potential anticancer application of fullerenol.
    Keywords:  autophagy; cytotoxicity; fullerenol; lysosomal dysfunction; starvation
  11. Am J Cancer Res. 2021 ;11(12): 5933-5950
      Glioblastoma multiforme (GBM) is the most common and aggressive form of brain tumors and the hardest type of cancer to treat. Therapies targeting developmental pathways, such as Notch, eliminate neoplastic glioma cells, but their efficacy can be limited by various mechanisms. Combination regimens may represent a good opportunity for effective therapies with durable effects. We used low doses of the γ-secretase inhibitor RO4929097 (GSI), to block the Notch pathway activity, in combination with Resveratrol (RSV) and we evidenced the mechanisms of autophagy/apoptosis transition in GBM cells. Resveratrol and GSI combination results in the synergistic induction of cell death together with the block of the autophagic flux evidenced by a sustained increase of LC3-II and p62 protein content, due to the dramatic reduction of CDK4, an important regulator of lysosomal function. The ectopic overexpression of the constitutive active CDK4 mutant, greatly counteracted the RSV+GSI induced block of the autophagy. Triggering autophagy in RSV+GSI-treated cells, which have impaired lysosomal function, caused the collapse of the system and a following apoptosis. For instance, by combining the CDK4 mutant as well as the early stage autophagy inhibitor, 3-methyladenina, abolished the RSV+GSI induced caspases activation. The initiator caspases (caspases-8 and -9), effector caspase (caspase-3) and its downstream substrate PARP were induced after RSV+GSI exposure as well as the percentage of the TUNEL positive cells. Moreover, the pro-apoptotic signaling MAPK p38 was activated while the pro-survival MAPK p42/p44 signaling was inhibited. In short, we establish the role of CDK4 in the regulation of autophagy/apoptosis transition induced by RSV and GSI in GBM cells. This new synergistic therapeutic combination, increasing the accumulation of autophagosomes, may have therapeutic value for GBM patients.
    Keywords:  Atg12; brain; cancer; cdk4; cell death; gamma secretase inhibitor
  12. Autophagy. 2022 Jan 09. 1-2
      Selective autophagy of damaged organelles assures maintenance of cellular homeostasis in eukaryotes. While the mechanisms by which cells selectively remove dysfunctional mitochondria, lysosomes, endoplasmic reticulum and other organelles has been well characterized, little is known about specific autophagy of damaged early endosomes. In our recent study, we uncovered a new role for RABEP1/Rabaptin5, a long-established regulator of early endosome function, in targeting the autophagy machinery to early endosomes damaged by chloroquine or by internalized Salmonella via interaction with RB1CC1/FIP200 and ATG16L1.
    Keywords:  ATG16L1; FIP200; Rabaptin5; Salmonella; autophagy; early endosome
  13. J Biol Chem. 2022 Jan 07. pii: S0021-9258(22)00013-8. [Epub ahead of print] 101573
      Autophagy is a lysosomal degradation pathway for the removal of damaged and superfluous cytoplasmic material. This is achieved by the sequestration of this cargo material within double membrane vesicles termed autophagosomes. Autophagosome formation is mediated by the conserved autophagy machinery. In selective autophagy this machinery including the transmembrane protein Atg9 is recruited to specific cargo material via cargo receptors and the Atg11/FIP200 scaffold protein. The molecular details of the interaction between Atg11 and Atg9 are unclear and it is still unknown how the recruitment of Atg9 is regulated. Here we employ NMR spectroscopy of the N-terminal disordered domain of Atg9 (Atg9-NTD) to map its interaction with Atg11 revealing that it involves two short peptides both containing a PLF motif. We show that the Atg9-NTD binds to Atg11 with an affinity of about 1 micromolar and that both PLF motifs contribute to the interaction. Mutation of the PLF motifs abolishes the interaction of Atg9-NTD with Atg11, reduces the recruitment of Atg9 to the precursor aminopeptidase 1 (prApe1) cargo and blocks prApe1 transport into the vacuole by the selective autophagy-like cytoplasm-to-vacuole (Cvt) targeting pathway while not affecting bulk autophagy. Our results provide mechanistic insights into the interaction of the Atg11 scaffold with the Atg9 transmembrane protein in selective autophagy and suggest a model where only clustered Atg11 when bound to the prApe1 cargo is able to efficiently recruit Atg9 vesicles.
    Keywords:  Autophagy; Intrinsically disordered proteins; Isothermal titration calorimetry; Nuclear magnetic resonance; yeast metabolism
  14. ACS Appl Bio Mater. 2020 Sep 21. 3(9): 5974-5983
      Autophagy is a cellular self-clearance process for maintaining regular cytoplasmic function, and modulation of autophagy can influence cytotoxicity, apoptosis, and clearance of toxic amyloid fibril. In a recent work, functional nanoparticles are used to modulate autophagy. However, the role of nanoparticle uptake mechanisms and their intracellular processing on autophagy is vaguely understood. Here, we show that autophagy is influenced by nanoparticle surface chemistry-directed intracellular trafficking and localization. In particular, we have designed iron oxide nanoparticles functionalized with arginine/arginine methyl ester/octyl/oleyl/cholesterol with a high cell uptake property. We found that autophagy is induced by octyl/oleyl functionalization without appreciable cell death. Further study shows that enhanced cytosolic delivery over membrane localization and increased intracellular aggregation over homogeneous cytosolic distribution lead to autophagy induction via intracellular reactive oxygen species generation. The observed result can be used to design functional nanoparticles/nanodrugs for modulating cellular autophagy that can be used in various biomedical applications.
    Keywords:  autophagy; iron oxide; nanoparticle; reactive oxygen species; surface chemistry
  15. ACS Appl Bio Mater. 2020 Apr 20. 3(4): 2048-2057
      Bioactive peptides, which act as biologically active regulators, often require intracellular delivery systems to access their therapeutic targets in the cytosolic space maintaining their bioactivity. Here, we report on the delivery of a polar cell impermeable bioactive peptide, phalloidin, into living HeLa cells with cationic liposomes prepared from lysine-based lipids. Liposome/Alexa Fluor 594 phalloidin complexes were characterized regarding their size and zeta potential, which were 85 ± 38 nm and +24.5 ± 4.21 mV, respectively. The delivery of Alexa Fluor 594 phalloidin into live HeLa cells with K3C14 liposomes was evaluated using a fluorescence activated cell sorter and confocal laser scanning microscopy. The highest Alexa Fluor 594 phalloidin delivery efficiency was 92% when using 200 μg of the cationic lipid/1 × 105 cells seeded at 37 °C. The cellular uptake mechanism for the cationic liposome/Alexa Fluor 594 phalloidin complexes was investigated using various endocytosis inhibitors. We confirmed the complexes were mainly taken up through caveolae-mediated endocytosis. Incubation with bafilomycin A1, which inhibits the acidification of lysosomes, revealed that Alexa Fluor 594 phalloidin did not pass through the lysosomal pathway. Rather, Alexa Fluor 594 phalloidin was released from early endosomes or caveosomes to the cytosol to exhibit its bioactive effects including the multinucleation of HeLa cells.
    Keywords:  amino lipid; bioactive peptide; cationic liposomes; endosomal/lysosomal escape; intracellular delivery; liposomal complex; multinucleation; phalloidin
  16. Ann N Y Acad Sci. 2022 Jan 08.
      Targeted protein degradation is critical for proper cellular function and development. Protein degradation pathways, such as the ubiquitin proteasomes system, autophagy, and endosome-lysosome pathway, must be tightly regulated to ensure proper elimination of misfolded and aggregated proteins and regulate changing protein levels during cellular differentiation, while ensuring that normal proteins remain unscathed. Protein degradation pathways have also garnered interest as a means to selectively eliminate target proteins that may be difficult to inhibit via other mechanisms. On June 7 and 8, 2021, several experts in protein degradation pathways met virtually for the Keystone eSymposium "Targeting protein degradation: from small molecules to complex organelles." The event brought together researchers working in different protein degradation pathways in an effort to begin to develop a holistic, integrated vision of protein degradation that incorporates all the major pathways to understand how changes in them can lead to disease pathology and, alternatively, how they can be leveraged for novel therapeutics.
    Keywords:  aggregation; autophagy; lysophagy; proteasome; protein degradation; ubiquitin
  17. Cancers (Basel). 2021 Dec 26. pii: 102. [Epub ahead of print]14(1):
      Germline inactivating variants of CDH1 are causative of hereditary diffuse gastric cancer (HDGC), a cancer syndrome characterized by an increased risk of both diffuse gastric cancer and lobular breast cancer. Because loss of function mutations are difficult to target therapeutically, we have taken a synthetic lethal approach to identify targetable vulnerabilities in CDH1-null cells. We have previously observed that CDH1-null MCF10A cells exhibit a reduced rate of endocytosis relative to wildtype MCF10A cells. To determine whether this deficiency is associated with wider vulnerabilities in vesicle trafficking, we screened isogenic MCF10A cell lines with known inhibitors of autophagy, endocytosis, and sphingolipid metabolism. Relative to wildtype MCF10A cells, CDH1-/- MCF10A cells showed significantly greater sensitivity to several drugs targeting these processes, including the autophagy inhibitor chloroquine, the endocytosis inhibitors chlorpromazine and PP1, and the sphingosine kinase 1 inhibitor PF-543. Synthetic lethality was confirmed in both gastric and mammary organoid models of CDH1 loss, derived from CD44-Cre/Cdh1fl/fl/tdTomato mice. Collectively, these results suggest that both sphingolipid metabolism and vesicle trafficking represent previously unrecognised druggable vulnerabilities in CDH1-null cells and may lead to the development of new therapies for HDGC.
    Keywords:  E-cadherin; autophagy; chemoprevention; endocytosis; hereditary diffuse gastric cancer; sphingolipid metabolism; synthetic lethality
  18. Int J Mol Sci. 2021 Dec 21. pii: 8. [Epub ahead of print]23(1):
      Early detection, characterization and monitoring of cancer are possible by using extracellular vesicles (EVs) isolated from non-invasively obtained liquid biopsy samples. They play a role in intercellular communication contributing to cell growth, differentiation and survival, thereby affecting the formation of tumor microenvironments and causing metastases. EVs were discovered more than seventy years ago. They have been tested recently as tools of drug delivery to treat cancer. Here we give a brief review on extracellular vesicles, exosomes, microvesicles and apoptotic bodies. Exosomes play an important role by carrying extracellular nucleic acids (DNA, RNA) in cell-to-cell communication causing tumor and metastasis development. We discuss the role of extracellular vesicles in the pathogenesis of cancer and their practical application in the early diagnosis, follow up, and next-generation treatment of cancer patients.
    Keywords:  biomarkers; cancer; cell-free nucleic acids; exosomes; liquid biopsy
  19. FEBS J. 2022 Jan 13.
      Adult T-cell leukemia/lymphoma (ATL) develops after a long period of human T-cell leukemia virus (HTLV)-1 infection and is associated with host aging in addition to genetic abnormalities in HTLV-1-infected cells. SIRT1 is a histone deacetylase involved in the cell cycle and apoptosis. We previously showed the high expression of SIRT1 protein in peripheral blood mononuclear cells from patients with ATL. There have been many reports that SIRT1 inhibitors show tumor suppressive effects. On the other hand, SIRT1 activator SRT1720 induces the cell death of multiple myeloma and breast cancer cells. However, the effect of SRT1720 on ATL is unknown. This study aimed to evaluate the effect of SRT1720 on cell death in leukemic cell lines in vitro and freshly isolated ATL cells ex vivo, and in an ATL in vivo mouse model. SRT1720 reduced cell viability in vitro and ex vivo. Additionally, SRT1720 increased the number of apoptotic cells, as shown by annexin V-positive cells, cleaved poly (ADP-ribose) polymerase 1, cleaved caspase-3, and fragmented DNA. SRT1720 also induced mitochondrial outer membrane permeabilization with the generation of mitochondrial reactive oxygen species and autophagy. However, SIRT1 knockdown did not attenuate SRT1720-induced cell death in leukemic cell lines. Finally, SRT1720 treatment decreased the growth of human ATL tumor xenografts in immunodeficient mice. Our study shows that while SRT1720 does not target SIRT1, it induces cell death in ATL cells via apoptosis and autophagy, and has anti-tumor activity.
    Keywords:  SIRT1; adult T-cell leukemia/lymphoma; apoptosis; caspase-independent cell death; human T-cell leukemia virus-1
  20. Commun Biol. 2022 Jan 12. 5(1): 47
      Lysosomal membrane permeabilization (LMP) and cathepsin release typifies lysosome-dependent cell death (LDCD). However, LMP occurs in most regulated cell death programs suggesting LDCD is not an independent cell death pathway, but is conscripted to facilitate the final cellular demise by other cell death routines. Previously, we demonstrated that Caenorhabditis elegans (C. elegans) null for a cysteine protease inhibitor, srp-6, undergo a specific LDCD pathway characterized by LMP and cathepsin-dependent cytoplasmic proteolysis. We designated this cell death routine, lysoptosis, to distinguish it from other pathways employing LMP. In this study, mouse and human epithelial cells lacking srp-6 homologues, mSerpinb3a and SERPINB3, respectively, demonstrated a lysoptosis phenotype distinct from other cell death pathways. Like in C. elegans, this pathway depended on LMP and released cathepsins, predominantly cathepsin L. These studies suggested that lysoptosis is an evolutionarily-conserved eukaryotic LDCD that predominates in the absence of neutralizing endogenous inhibitors.
  21. Biochem J. 2022 Jan 14. 479(1): 75-90
      Autophagy is a universal cellular homeostatic process, required for the clearance of dysfunctional macromolecules or organelles. This self-digestion mechanism modulates cell survival, either directly by targeting cell death players, or indirectly by maintaining cellular balance and bioenergetics. Nevertheless, under acute or accumulated stress, autophagy can also contribute to promote different modes of cell death, either through highly regulated signalling events, or in a more uncontrolled inflammatory manner. Conversely, apoptotic or necroptotic factors have also been implicated in the regulation of autophagy, while specific factors regulate both processes. Here, we survey both earlier and recent findings, highlighting the intricate interaction of autophagic and cell death pathways. We, Furthermore, discuss paradigms, where this cross-talk is disrupted, in the context of disease.
    Keywords:  apoptosis; autophagic cell death; autophagy; cancer; necroptosis; neurodegeneration
  22. Bioessays. 2022 Jan 14. e2100224
      Autophagy and YAP1-WWTR1/TAZ signalling are tightly linked in a complex control system of forward and feedback pathways which determine different cellular outcomes in differing cell types at different time-points after perturbations. Here we extend our previous experimental and modelling approaches to consider two possibilities. First, we have performed additional mathematical modelling to explore how the autophagy-YAP1 crosstalk may be controlled by posttranslational modifications of components of the pathways. Second, since analogous contrasting results have also been reported for autophagy as a regulator of other transduction pathways engaged in tumorigenesis (Wnt/β-catenin, TGF-β/Smads, NF-kB or XIAP/cIAPs), we have considered if such discrepancies may be explicable through situations involving competing pathways and feedback loops in different cell types, analogous to the autophagy-YAP/TAZ situation. Since distinct posttranslational modifications dominate those pathways in distinct cells, these need to be understood to enable appropriate cell type-specific therapeutic strategies for cancers and other diseases.
    Keywords:  YAP1 signalling; autophagy; cell heterogeneity; mathematical model; precision medicine; transduction pathways
  23. Molecules. 2021 Dec 28. pii: 177. [Epub ahead of print]27(1):
      Melanogenesis and melanosome secretion are regulated by several mechanisms. In this study, we found that the oxindole derivative GIF-2209 accelerated melanogenesis associated with the discrimination in the expression and intracellular distributions of two melanogenic enzymes, tyrosinase (TYR) and tyrosinase-related protein-1 (TYRP-1). GIF-2209 upregulated the expression of TYR via a microphthalmia transcription factor (MITF)-independent mechanism, leading to high expression of protein. In contrast, GIF-2209 did not alter the mRNA levels of TYRP-1 and suppressed its protein levels. GIF-2209 induced the dissociation of TYR from TYRP-1 but did not alter the association between TYR and CD63, a melanosome and lysosome marker. The protein levels of CD63 were also upregulated by GIF-2209. GIF-2209 induced lysosome expansion and redistribution in all areas of the cytosol, accompanied by autophagy acceleration (upregulation of LC3BII protein levels and downregulation of p62 protein levels). In addition, GIF-2209 stimulated the secretion of melanosomes containing high levels of TYR, TYRP-1, and CD63 proteins. The GIF-2209 mediated melanosome secretion was sensitive to the lysosome inhibitor chloroquine. These results suggest that GIF-2209 may activate lysosomal functions with TYR gene expression, while it accelerates melanosome secretion, which finally leads to the depletion of intracellular melanogenic enzyme, especially TYRP-1 protein.
    Keywords:  B16F10; SU5205; TYRP-1; lysosome; melanogenesis; melanosome; oxindole; tyrosinase
  24. Cell Death Dis. 2022 01 10. 13(1): 45
      PHY34 is a synthetic small molecule, inspired by a compound naturally occurring in tropical plants of the Phyllanthus genus. PHY34 was developed to have potent in vitro and in vivo anticancer activity against high grade serous ovarian cancer (HGSOC) cells. Mechanistically, PHY34 induced apoptosis in ovarian cancer cells by late-stage autophagy inhibition. Furthermore, PHY34 significantly reduced tumor burden in a xenograft model of ovarian cancer. In order to identify its molecular target/s, we undertook an unbiased approach utilizing mass spectrometry-based chemoproteomics. Protein targets from the nucleocytoplasmic transport pathway were identified from the pulldown assay with the cellular apoptosis susceptibility (CAS) protein, also known as CSE1L, representing a likely candidate protein. A tumor microarray confirmed data from mRNA expression data in public databases that CAS expression was elevated in HGSOC and correlated with worse clinical outcomes. Overexpression of CAS reduced PHY34 induced apoptosis in ovarian cancer cells based on PARP cleavage and Annexin V staining. Compounds with a diphyllin structure similar to PHY34 have been shown to inhibit the ATP6V0A2 subunit of V(vacuolar)-ATPase. Therefore, ATP6V0A2 wild-type and ATP6V0A2 V823 mutant cell lines were tested with PHY34, and it was able to induce cell death in the wild-type at 246 pM while the mutant cells were resistant up to 55.46 nM. Overall, our data demonstrate that PHY34 is a promising small molecule for cancer therapy that targets the ATP6V0A2 subunit to induce autophagy inhibition while interacting with CAS and altering nuclear localization of proteins.
  25. Int J Mol Sci. 2021 Dec 29. pii: 333. [Epub ahead of print]23(1):
      Cervical cancer is a significant gynecological cancer and causes cancer-related deaths worldwide. Human papillomavirus (HPV) is implicated in the etiology of cervical malignancy. However, much evidence indicates that HPV infection is a necessary but not sufficient cause in cervical carcinogenesis. Therefore, the cellular pathophysiology of cervical cancer is worthy of study. This review summarizes the recent findings concerning the ion transport processes involved in cell volume regulation and intracellular Ca2+ homeostasis of epithelial cells and how these transport systems are themselves regulated by the tumor microenvironment. For cell volume regulation, we focused on the volume-sensitive Cl- channels and K+-Cl- cotransporter (KCC) family, important regulators for ionic and osmotic homeostasis of epithelial cells. Regarding intracellular Ca2+ homeostasis, the Ca2+ store sensor STIM molecules and plasma membrane Ca2+ channel Orai proteins, the predominant Ca2+ entry mechanism in epithelial cells, are discussed. Furthermore, we evaluate the potential of these membrane ion transport systems as diagnostic biomarkers and pharmacological interventions and highlight the challenges.
    Keywords:  K+-Cl− cotransport; Orai; cell cycle progression; cell volume regulation; cervical cancer; migration; store-operated Ca2+ entry; stromal interaction molecule (STIM); volume-sensitive Cl− channels