The lysosome-associated apoptosis-inducing protein containing the pleckstrin homology (PH) and FYVE domains (LAPF), representative of a novel family of PH and FYVE domain-containing proteins, induces caspase-independent apoptosis via the lysosomal-mitochondrial pathway

The role of Phafin proteins in cell signaling pathways and diseases

Membrane-associated proteins are important membrane readers that mediate and facilitate the signaling and trafficking pathways in eukaryotic membrane-bound compartments. The protein members in the Phafin family are membrane readers containing two phosphoinositide recognition domains: the Pleckstrin Homology domain and the FYVE (Fab1, YOTB, Vac1, and early endosome antigen 1) domain. Phafin proteins, categorized into two subfamilies, Phafin1 and Phafin2, associate with cellular membranes through interactions involving membrane-embedded phosphoinositides and phosphoinositide-binding domains. These membrane-associated Phafin proteins play pivotal roles by recruiting binding partners and forming complexes, which contribute significantly to apoptotic, autophagic, and macropinocytotic pathways. Elevated expression levels of Phafin1 and Phafin2 are observed in various cancers. A recent study highlights a significant increase in Phafin1 protein levels in the lungs of idiopathic pulmonary fibrosis patients compared to normal subjects, suggesting a crucial role for Phafin1 in the pathogenesis of pulmonary fibrosis. Additionally, phosphatidylinositol-3-phosphate-binding 2 (Pib2), a close relative of the Phafin1 protein, functions as an amino acid sensor activating the TOCR1 pathway in yeasts. This review focuses on delineating the involvement of Phafin proteins in cellular signaling and their implications in diseases and briefly discusses the latest research findings concerning Pib2.

Underlying Mechanism of Lysosomal Membrane Permeabilization in CNS Injury: A Literature Review

Lysosomes play a crucial role in various intracellular pathways as their final destination. Various stressors, whether mild or severe, can induce lysosomal membrane permeabilization (LMP), resulting in the release of lysosomal enzymes into the cytoplasm. LMP not only plays a pivotal role in various cellular events but also significantly contributes to programmed cell death (PCD). Previous research has demonstrated the participation of LMP in central nervous system (CNS) injuries, including traumatic brain injury (TBI), spinal cord injury (SCI), subarachnoid hemorrhage (SAH), and hypoxic-ischemic encephalopathy (HIE). However, the mechanisms underlying LMP in CNS injuries are poorly understood. The occurrence of LMP leads to the activation of inflammatory pathways, increased levels of oxidative stress, and PCD. Herein, we present a comprehensive overview of the latest findings regarding LMP and highlight its functions in cellular events and PCDs (lysosome-dependent cell death, apoptosis, pyroptosis, ferroptosis, and autophagy). In addition, we consolidate the most recent insights into LMP in CNS injury by summarizing and exploring the latest advances. We also review potential therapeutic strategies that aim to preserve LMP or inhibit the release of enzymes from lysosomes to alleviate the consequences of LMP in CNS injury. A better understanding of the role that LMP plays in CNS injury may facilitate the development of strategic treatment options for CNS injury.

Research progress in green synthesis of manganese and manganese oxide nanoparticles in biomedical and environmental applications - A review

Nanomaterials and nanotechnology have this unassailable position for environmental remediation and medicine. Currently, global environmental pollution and public health problems are increasing and need to be urgently addressed. Manganese (Mn) is one of the essential metal elements for plants and animals, it is necessary to integrate with nanotechnology. Mn and Mn oxide (MnO) nanoparticles (NPs) have applications in dye degradation, biomedicine, electrochemical sensors, plant and animal growth, and catalysis. However, the current research is limited, especially in terms of optimal synthesis of Mn and MnO NPs, separation, purification conditions, and the development of potential application areas is too basic and do not support by in-depth studies. Hence, this review comprehensively discusses the classification, green synthesis methods, and applications of Mn and MnO NPs in biomedical, environmental, and other fields and gives a perspective for the future.

Quadruped Gait and Regulation of Apoptotic Factors in Tibiofemoral Joints following Intra-Articular rhPRG4 Injection in Prg4 Null Mice

Camptodactyly-arthropathy-coxa vara-pericarditis (CACP) syndrome leads to diarthrodial joint arthropathy and is caused by the absence of lubricin (proteoglycan 4—PRG4), a surface-active mucinous glycoprotein responsible for lubricating articular cartilage. In this study, mice lacking the orthologous gene Prg4 served as a model that recapitulates the destructive arthrosis that involves biofouling of cartilage by serum proteins in lieu of Prg4. This study hypothesized that Prg4-deficient mice would demonstrate a quadruped gait change and decreased markers of mitochondrial dyscrasia, following intra-articular injection of both hindlimbs with recombinant human PRG4 (rhPRG4). Prg4^−/− (N = 44) mice of both sexes were injected with rhPRG4 and gait alterations were studied at post-injection day 3 and 6, before joints were harvested for immunohistochemistry for caspase-3 activation. Increased stance and propulsion was shown at 3 days post-injection in male mice. There were significantly fewer caspase-3-positive chondrocytes in tibiofemoral cartilage from rhPRG4-injected mice. The mitochondrial gene Mt-tn, and myosin heavy (Myh7) and light chains (Myl2 and Myl3), known to play a cytoskeletal stabilizing role, were significantly upregulated in both sexes (RNA-Seq) following IA rhPRG4. Chondrocyte mitochondrial dyscrasias attributable to the arthrosis in CACP may be mitigated by IA rhPRG4. In a supporting in vitro crystal microbalance experiment, molecular fouling by albumin did not block the surface activity of rhPRG4.

Backbone 1H, 15N, and 13C resonance assignments of the Phafin2 pleckstrin homology domain

Phafin2 is a peripheral protein that triggers cellular signaling from endosomal and lysosomal compartments. The specific subcellular localization of Phafin2 is mediated by the presence of a tandem of phosphatidylinositol 3-phosphate (PtdIns3P)-binding domains, the pleckstrin homology (PH) and the Fab-1, YOTB, Vac1, and EEA1 (FYVE) domains. The requirement for both domains for binding to PtdIns3P still remains unclear. To understand the molecular interactions of the Phafin2 PH domain in detail, we report its nearly complete 1H, 15N, and 13C backbone resonance assignments.

Genome-wide methylation and expression analyses reveal the epigenetic landscape of immune-related diseases for tobacco smoking

BACKGROUND

Smoking is a major causal risk factor for lung cancer, chronic obstructive pulmonary disease (COPD), cardiovascular disease (CVD), and is the main preventable cause of deaths in the world. The components of cigarette smoke are involved in immune and inflammatory processes, which may increase the prevalence of cigarette smoke-related diseases. However, the underlying molecular mechanisms linking smoking and diseases have not been well explored. This study was aimed to depict a global map of DNA methylation and gene expression changes induced by tobacco smoking and to explore the molecular mechanisms between smoking and human diseases through whole-genome bisulfite sequencing (WGBS) and RNA-sequencing (RNA-seq).

RESULTS

We performed WGBS on 72 samples (36 smokers and 36 nonsmokers) and RNA-seq on 75 samples (38 smokers and 37 nonsmokers), and cytokine immunoassay on plasma from 22 males (9 smokers and 13 nonsmokers) who were recruited from the city of Jincheng in China. By comparing the data of the two groups, we discovered a genome-wide methylation landscape of differentially methylated regions (DMRs) associated with smoking. Functional enrichment analyses revealed that both smoking-related hyper-DMR genes (DMGs) and hypo-DMGs were related to synapse-related pathways, whereas the hypo-DMGs were specifically related to cancer and addiction. The differentially expressed genes (DEGs) revealed by RNA-seq analysis were significantly enriched in the "immunosuppression" pathway. Correlation analysis of DMRs with their corresponding gene expression showed that genes affected by tobacco smoking were mostly related to immune system diseases. Finally, by comparing cytokine concentrations between smokers and nonsmokers, we found that vascular endothelial growth factor (VEGF) was significantly upregulated in smokers.

CONCLUSIONS

In sum, we found that smoking-induced DMRs have different distribution patterns in hypermethylated and hypomethylated areas between smokers and nonsmokers. We further identified and verified smoking-related DMGs and DEGs through multi-omics integration analysis of DNA methylome and transcriptome data. These findings provide us a comprehensive genomic map of the molecular changes induced by smoking which would enhance our understanding of the harms of smoking and its relationship with diseases.

Pib2 as an Emerging Master Regulator of Yeast TORC1

Cell growth is dynamically regulated in response to external cues such as nutrient availability, growth factor signals, and stresses. Central to this adaptation process is the Target of Rapamycin Complex 1 (TORC1), an evolutionarily conserved kinase complex that fine-tunes an enormous number of cellular events. How upstream signals are sensed and transmitted to TORC1 has been intensively studied in major model organisms including the budding yeast Saccharomyces cerevisiae. This field recently saw a breakthrough: the identification of yeast phosphatidylInositol(3)-phosphate binding protein 2 (Pib2) protein as a critical regulator of TORC1. Although the study of Pib2 is still in its early days, multiple groups have provided important mechanistic insights on how Pib2 relays nutrient signals to TORC1. There remain, on the other hand, significant gaps in our knowledge and mysteries that warrant further investigations. This is the first dedicated review on Pib2 that summarizes major findings and outstanding questions around this emerging key player in cell growth regulation.

Lysosome Depletion-Triggered Autophagy Impairment in Progressive Kidney Injury

Background

Macroautophagy (autophagy) is a cellular recycling process involving the destruction of damaged organelles and proteins in intracellular lysosomes for efficient nutrient reuse.

Summary

Impairment of the autophagy-lysosome pathway is tightly associated with multiple kidney diseases, such as diabetic nephropathy, proteinuric kidney disease, acute kidney injury, crystalline nephropathy, and drug- and heavy metal-induced renal injury. The impairment in the process of autophagic clearance may induce injury in renal intrinsic cells by activating the inflammasome, inducing cell cycle arrest, and cell death. The lysosome depletion may be a key mechanism triggering this process. In this review, we discuss this pathway and summarize the protective mechanisms for restoration of lysosome function and autophagic flux via the endosomal sorting complex required for transport (ESCRT) machinery, lysophagy, and transcription factor EB-mediated lysosome biogenesis.

Key Message

Further exploring mechanisms of ESCRT, lysophagy, and lysosome biogenesis may provide novel therapy strategies for the management of kidney diseases.

Comparative transcriptome analysis of lethality in response to RNA interference of the oriental river prawn (Macrobrachium nipponense)

A previous study identified slow-tonic S2 tropomyosin and slow tropomyosin isoform as sex-related genes in Macrobrachium nipponense. Their functions were analyzed using RNA interference. However, more than half of the specimens died approximately 8-12 h after injection of the respective double-stranded RNAs (dsRNAs), and HE staining indicated that the heart and gills were the most likely tissues responsible for the resultant deaths. In the current study, we conducted a comparative transcriptomic study of the gills and hearts of M. nipponense to identify potential target genes associated with acute death after dsRNA injection. A total of 68,772 annotated unigenes were generated. In the heart, differentially expressed genes (DEGs) were mainly enriched in glycolysis/gluconeogenesis and oxidative phosphorylation, while the most relevant pathways in the gills were lysosome, phagosome, and peroxisome. Ten DEGs were screened out and analyzed under lethal hypoxic stress. Among these, fructose 1, 6-biphosphate-aldolase (FBA), glyceraldehyde 3-phosphate dehydrogenase (GDPDH), alcohol dehydrogenase class-3 (ADC3), ATP-synthase subunit 9 (ATPS9), and acid ceramidase-like (ACL) were all differentially expressed under hypoxic conditions. This study shed light on the lethal mechanism caused by interference with tropomyosin genes in M. nipponense, and identifies the related pathways and key genes that could help to improve stress resistance and tolerance in M. nipponense.

Mini-Review on Lipofuscin and Aging: Focusing on The Molecular Interface, The Biological Recycling Mechanism, Oxidative Stress, and The Gut-Brain Axis Functionality

Intra-lysosomal accumulation of the autofluorescent "residue" known as lipofuscin, which is found within postmitotic cells, remains controversial. Although it was considered a harmless hallmark of aging, its presence is detrimental as it continually accumulates. The latest evidence highlighted that lipofuscin strongly correlates with the excessive production of reactive oxygen species; however, despite this, lipofuscin cannot be removed by the biological recycling mechanisms. The antagonistic effects exerted at the DNA level culminate in a dysregulation of the cell cycle, by inducing a loss of the entire internal environment and abnormal gene(s) expression. Additionally, it appears that a crucial role in the production of reactive oxygen species can be attributed to gut microbiota, due to their ability to shape our behavior and neurodevelopment through their maintenance of the central nervous system.

Oxidative damage of lysosomes in regulated cell death systems: Pathophysiology and pharmacologic interventions

Lysosomes are small specialized organelles containing a variety of different hydrolase enzymes that are responsible for degradation of all macromolecules, entering the cells through the endosomal system or originated from the internal sources. This allows for transport and recycling of nutrients and internalization of surface proteins for antigen presentation as well as maintaining cellular homeostasis. Lysosomes are also important storage compartments for metal ions and nutrients. The integrity of lysosomal membrane is central to maintaining their normal function, but like other cellular membranes, lysosomal membrane is subject to damage mediated by reactive oxygen species. This results in spillage of lysosomal enzymes into the cytoplasm, leading to proteolytic damage to cellular systems and organelles. Several forms of lysosomal dependent cell death have been identified in diseases. Examination of these events are important for finding treatment strategies relevant to cancer or neurodegenerative diseases as well as autoimmune deficiencies. In this review, we have examined the current literature on involvement of lysosomes in induction of programed cell death and have provided an extensive list of therapeutic approaches that can modulate cell death. Exploitation of these mechanisms can lead to novel therapies for cancer and neurodegenerative diseases.

Autophagy as a modulator of cell death machinery

The balance between cell death and survival is a critical parameter in the regulation of cells and the maintenance of homeostasis in vivo. Three major mechanisms for cell death have been identified in mammalian cells: apoptosis (type I), autophagic cell death (type II), and necrosis (type III). These three mechanisms have been suggested to engage in cross talk with each other. Among them, autophagy was originally characterized as a cell survival mechanism for amino acid recycling during starvation. Whether autophagy functions primarily in cell survival or cell death is a critical question yet to be answered. Here, we present a comprehensive review of the cell death-related events that take place during autophagy and their underlying mechanisms in cancer and autoimmune disease development.

ADAM12 silencing promotes cellular apoptosis by activating autophagy in choriocarcinoma cells

ADAM metallopeptidase domain 12 (ADAM12) has been demonstrated to mediate cell proliferation and apoptosis resistance in several types of cancer cells. However, the effect of ADAM12 silencing on the proliferation and apoptosis of choriocarcinoma cells remains unknown. The present study revealed that ADAM12 silencing significantly inhibited cellular activity and proliferation in the human choriocarcinoma JEG3 cell line and increased the rate of apoptosis. In addition, ADAM12 silencing significantly increased the expression levels of the autophagy proteins microtubule-associated protein-light-chain 3 (LC3B) and autophagy related 5 (ATG5) and the fluorescence density of LC3B in JEG-3 cells. However, the suppression of autophagy by 3-methyladenine could block ADAM12 silencing-induced cellular apoptosis. ADAM12 silencing reduced the levels of the inflammatory factors interleukin-1β, interferon-γ and TNF-α, and inactivated nuclear p65-NF-κB and p-mTOR in JEG-3 cells. The downregulation of p-mTOR expression by ADAM12 silencing was rescued in 3-methyladenine-treated JEG-3 cells, indicating that mTOR might participate in the autophagy-mediated pro-apoptotic effect of ADAM12 silencing. In conclusion, ADAM12 silencing promoted cellular apoptosis in human choriocarcinoma JEG3 cells, which might be associated with autophagy and the mTOR response. These findings indicate that ADAM12 silencing might be a potential novel therapeutic target for choriocarcinoma.

An endosomal LAPF is required for macrophage endocytosis and elimination of bacteria

Macrophages can internalize the invading pathogens by raft/caveolae and/or clathrin-dependent endocytosis and elicit an immune response against infection. However, the molecular mechanism for macrophage endocytosis remains elusive. Here we report that LAPF (lysosome-associated and apoptosis-inducing protein containing PH and FYVE domains) is required for caveolae-mediated endocytosis. Lapf -deficient macrophages have impaired capacity to endocytose and eliminate bacteria. Macrophage-specific Lapf-deficient mice are more susceptible to Escherichia coli (E. coli) infection with higher bacterial loads. Moreover, Lapf deficiency impairs TLR4 endocytosis, resulting in attenuated production of TLR-triggered proinflammatory cytokines. LAPF is localized to early endosomes and interacts with caveolin-1. Phosphorylation of LAPF by the tyrosine kinase Src is required for LAPF-Src-Caveolin complex formation and endocytosis and elimination of bacteria. Collectively, our work demonstrates that LAPF is critical for endocytosis of bacteria and induction of inflammatory responses, suggesting that LAPF and Src could be potential targets for the control of infectious diseases.

Functional characterization of lysosomal interaction of Akt with VRK2

Serine-threonine kinase Akt (also known as PKB, protein kinase B), a core intracellular mediator of cell survival, is involved in various human cancers and has been suggested to play an important role in the regulation of autophagy in mammalian cells. Nonetheless, the physiological function of Akt in the lysosomes is currently unknown. We have reported previously that PtdIns(3)P-dependent lysosomal accumulation of the Akt-Phafin2 complex is a critical step for autophagy induction. Here, to characterize the molecular function of activated Akt in the lysosomes in the process of autophagy, we searched for the molecules that interact with the Akt complex at the lysosomes after induction of autophagy. By time-of-flight-mass spectrometry (TOF/MS) analysis, kinases of the VRK family, a unique serine-threonine family of kinases in the human kinome, were identified. VRK2 interacts with Akt1 and Akt2, but not with Akt3; the C terminus of Akt and the N terminus of VRK2 facilitate the interaction of Akt and VRK2 in mammalian cells. The kinase-dead form of VRK2A (KD VRK2A) failed to interact with Akt in coimmunoprecipitation assays. Bimolecular fluorescence complementation (BiFC) experiments showed that, in the lysosomes, Akt interacted with VRK2A but not with VRK2B or KD VRK2A. Immunofluorescent assays revealed that VRK2 and phosphorylated Akt accumulated in the lysosomes after autophagy induction. WT VRK2A, but not KD VRK2A or VRK2B, facilitated accumulation of phosphorylated Akt in the lysosomes. Downregulation of VRK2 abrogated the lysosomal accumulation of phosphorylated Akt and impaired nuclear localization of TFEB; these events coincided to inhibition of autophagy induction. The VRK2-Akt complex is required for control of lysosomal size, acidification, bacterial degradation, and for viral replication. Moreover, lysosomal VRK2-Akt controls cellular proliferation and mitochondrial outer-membrane stabilization. Given the roles of autophagy in the pathogenesis of human cancer, the current study provides a novel insight into the oncogenic activity of VRK2-Akt complexes in the lysosomes via modulation of autophagy.

Gut microbiota regulates mouse behaviors through glucocorticoid receptor pathway genes in the hippocampus

Gut microbiota has an important role in the immune system, metabolism, and digestion, and has a significant effect on the nervous system. Recent studies have revealed that abnormal gut microbiota induces abnormal behaviors, which may be associated with the hypothalamic-pituitary-adrenal (HPA) axis. Therefore, we investigated the behavioral changes in germ-free (GF) mice by behavioral tests, quantified the basal serum cortisol levels, and examined glucocorticoid receptor pathway genes in hippocampus using microarray analysis followed by real-time PCR validation, to explore the molecular mechanisms by which the gut microbiota influences the host's behaviors and brain function. Moreover, we quantified the basal serum cortisol levels and validated the differential genes in an Escherichia coli-derived lipopolysaccharide (LPS) treatment mouse model and fecal "depression microbiota" transplantation mouse model by real-time PCR. We found that GF mice showed antianxiety- and antidepressant-like behaviors, whereas E. coli LPS-treated mice showed antidepressant-like behavior, but did not show antianxiety-like behavior. However, "depression microbiota" recipient mice exhibited anxiety- and depressive-like behaviors. In addition, six glucocorticoid receptor pathway genes (Slc22a5, Aqp1, Stat5a, Ampd3, Plekhf1, and Cyb561) were upregulated in GF mice, and of these only two (Stat5a and Ampd3) were upregulated in LPS-treated mice, whereas the shared gene, Stat5a, was downregulated in "depression microbiota" recipient mice. Furthermore, basal serum cortisol levels were decreased in E. coli LPS-treated mice but not in GF mice and "depression microbiota" recipient mice. These results indicated that the gut microbiota may lead to behavioral abnormalities in mice through the downstream pathway of the glucocorticoid receptor. Herein, we proposed a new insight into the molecular mechanisms by which gut microbiota influence depressive-like behavior.

The Transcriptome of the Zebrafish Embryo After Chemical Exposure: A Meta-Analysis

Numerous studies have been published in the past years investigating the transcriptome of the zebrafish embryo (ZFE) upon being subjected to chemical stress. Aiming at a more mechanistic understanding of the results of such studies, knowledge about commonalities of transcript regulation in response to chemical stress is needed. Thus, our goal in this study was to identify and interpret genes and gene sets constituting a general response to chemical exposure. Therefore, we aggregated and reanalyzed published toxicogenomics data obtained with the ZFE. We found that overlap of differentially transcribed genes in response to chemical stress across independent studies is generally low and the most commonly differentially transcribed genes appear in less than 50% of all treatments across studies. However, effect size analysis revealed several genes showing a common trend of differential expression, among which genes related to calcium homeostasis emerged as key, especially in exposure settings up to 24 h post-fertilization. Additionally, we found that these and other downregulated genes are often linked to anatomical regions developing during the respective exposure period. Genes showing a trend of increased expression were, among others, linked to signaling pathways (e.g., Wnt, Fgf) as well as lysosomal structures and apoptosis. The findings of this study help to increase the understanding of chemical stress responses in the developing zebrafish embryo and provide a starting point to improve experimental designs for this model system. In future, improved time- and concentration-resolved experiments should offer better understanding of stress response patterns and access to mechanistic information.

Zerumbone reduces proliferation of HCT116 colon cancer cells by inhibition of TNF-alpha

Zerumbone is a known anti-cancer herbal compound. However, the actual protein target is not fully understood or known. This investigation focus on the association of zerumbone in HCT116 colon cancer cell proliferation and its link with TNF-alpha. The study shows that with the increasing concentration of zerumbone, there was a reduction of HCT116 cells proliferation based on the cell line study and hence higher TNF-alpha inhibition based on the TNF-alpha assay. The study also emphasizes on the computational aspect by investigating the molecular docking analysis of zerumbone against TNF-alpha. The docked complex was further validated using molecular dynamics simulation studies. The docking analysis observed that alpha-beta unsaturated carbonyl scaffold is an important moiety for the anti-cancer activity of zerumbone. Furthermore, the DFT analysis also confirms the reactivity nature of zerumbone based on the frontier molecular orbital analysis.

Integration of cellular and molecular endpoints to assess the toxicity of polycyclic aromatic hydrocarbons in HepG2 cell line

Polycyclic aromatic hydrocarbons (PAHs) are persistent pollutants present in the environment with known mutagenic and carcinogenic properties. In the present study the effects of exposure to single or multiple doses of benzo[a]anthracene (BaA), pyrene (Pyr), and 3 halogenated derivatives of these compounds (1-chloropyrene, 1-bromopyrene [1-BrPyr], and 7-chlorobenzo[a]anthracene [7-ClBaA]) were evaluated in a liver-derived human cell line (HepG2). Cytotoxicity as assessed by the classic 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and neutral red assays showed a mild toxic effect in response to single or multiple dose exposure for up to 72 h, except for multiple dose exposure to BaA and 7-ClBaA (1 μM/d for 4 d) and single exposure to 10 μM BaA. Furthermore, selective mitochondrial and lysosomal toxicity was observed for Pyr and BaA series, respectively. To understand the underlying molecular mechanisms responsible for this effect, reactive oxygen species production, mitochondrial membrane depolarization, lysosomal pH, DNA fragmentation, and early and late apoptosis mediators were evaluated after exposure to single doses of the compounds. All compounds were able to trigger oxidative stress after 24 h as measured by catalase activity, and a good correlation was found between mitochondrial membrane depolarization, lysosomal pH increase, and MTT and neutral red assays. Evaluation of cell death mediators showed that caspase-3/7, but not annexin-V, pathways were involved in toxicity triggered by the studied compounds. The integration of all results showed that 1-BrPyr and BaA have a higher toxicity potential. Environ Toxicol Chem 2017;36:3404-3414. © 2017 SETAC.

Structural, thermodynamic, and phosphatidylinositol 3-phosphate binding properties of Phafin2

Phafin2 is a phosphatidylinositol 3-phosphate (PtdIns(3)P) binding protein involved in the regulation of endosomal cargo trafficking and lysosomal induction of autophagy. Binding of Phafin2 to PtdIns(3)P is mediated by both its PH and FYVE domains. However, there are no studies on the structural basis, conformational stability, and lipid interactions of Phafin2 to better understand how this protein participates in signaling at the surface of endomembrane compartments. Here, we show that human Phafin2 is a moderately elongated monomer of ∼28 kDa with an intensity-average hydrodynamic diameter of ∼7 nm. Circular dichroism (CD) analysis indicates that Phafin2 exhibits an α/β structure and predicts ∼40% random coil content in the protein. Heteronuclear NMR data indicates that a unique conformation of Phafin2 is present in solution and dispersion of resonances suggests that the protein exhibits random coiled regions, in agreement with the CD data. Phafin2 is stable, displaying a melting temperature of 48.4°C. The folding-unfolding curves, obtained using urea- and guanidine hydrochloride-mediated denaturation, indicate that Phafin2 undergoes a two-state native-to-denatured transition. Analysis of these transitions shows that the free energy change for urea- and guanidine hydrochloride-induced Phafin2 denaturation in water is ∼4 kcal mol-1 . PtdIns(3)P binding to Phafin2 occurs with high affinity, triggering minor conformational changes in the protein. Taken together, these studies represent a platform for establishing the structural basis of Phafin2 molecular interactions and the role of the two potentially redundant PtdIns(3)P-binding domains of the protein in endomembrane compartments.

A combined biomarker and clinical panel for chronic graft versus host disease diagnosis

Whilst many chronic graft versus host disease (cGVHD) biomarkers have been previously reported, few have been verified in an independent cGVHD cohort. We aimed to verify the diagnostic accuracy of previously reported markers of cGVHD in a multi-centre Chronic GVHD Consortium. A total of 42 RNA and 18 protein candidate biomarkers were assessed amongst 59 cGVHD cases and 33 matched non-GVHD controls. Total RNA was isolated from PBMC, and RNA markers were quantified using PCR. Serum protein markers were quantified using ELISA. A combined 3 RNA biomarker (IRS2, PLEKHF1 and IL1R2) and 2 clinical variables (recipient CMV serostatus and conditioning regimen intensity) panel accurately (AUC 0.81) segregated cGVHD cases from controls. Other studied RNA and protein markers were not confirmed as accurate cGVHD diagnostic biomarkers. The studied markers failed to segregate higher risk cGVHD (per overall NIH 0-3 score, and overlap versus classic cGVHD status). These data support the need for multiple independent verification studies for the ultimate clinical application of cGVHD diagnostic biomarkers.

Knockdown of Long Noncoding RNA NR_026689 Inhibits Proliferation and Invasion and Increases Apoptosis in Ovarian Carcinoma HO-8910PM Cells

Ovarian cancer is one of the leading causes of gynecological cancer-related deaths worldwide. We investigated the role of a newly discovered long noncoding RNA, NR_026689, in cell proliferation, metastasis, and apoptosis in ovarian cancer cells. Our results showed that NR_026689 was overexpressed in both clinical ovarian cancer patients and cultured ovarian cancer cells. Knockdown of NR_026689 in HO-8910PM cells significantly decreased the cell proliferative rate and the ability to form colonies. Transwell assays revealed that depletion of NR_026689 suppressed cell migration ability by 68% and cell invasive capacity by 71% in HO-8910PM cells. Moreover, specific shRNAs against NR_026689 notably promoted cell apoptosis in HO-8910PM cells by upregulating the expression of proapoptotic proteins, including caspase 3, caspase 9, cytochrome C, and PARP. Our study suggests an oncogenic potential of NR_026689 in ovarian cancer and might provide novel clues for the diagnosis and treatment of ovarian cancer in the clinic.

A LAPF/phafin1-like protein regulates TORC1 and lysosomal membrane permeabilization in response to endoplasmic reticulum membrane stress

The controlled permeabilization of lysosomes and vacuoles may represent an ancient manner of programmed cell death. It is shown that TORC1 is required for lysosomal membrane permeabilization and death of yeast cells that have been exposed to antifungals, and that a novel FYVE-domain protein regulates TORC1 signaling in these conditions.

Lysosomal membrane permeabilization (LMP) is a poorly understood regulator of programmed cell death that involves leakage of luminal lysosomal or vacuolar hydrolases into the cytoplasm. In Saccharomyces cerevisiae, LMP can be induced by antifungals and endoplasmic reticulum stressors when calcineurin also has been inactivated. A genome-wide screen revealed Pib2, a relative of LAPF/phafin1 that regulates LMP in mammals, as a pro-LMP protein in yeast. Pib2 associated with vacuolar and endosomal limiting membranes in unstressed cells in a manner that depended on its FYVE domain and on phosphatidylinositol 3-phosphate (PI(3)P) biosynthesis. Genetic experiments suggest that Pib2 stimulates the activity of TORC1, a vacuole-associated protein kinase that is sensitive to rapamycin, in a pathway parallel to the Ragulator/EGO complex containing the GTPases Gtr1 and Gtr2. A hyperactivating mutation in the catalytic subunit of TORC1 restored LMP to the gtr1∆ and pib2∆ mutants and also prevented the synthetic lethality of the double mutants. These findings show novel roles of PI(3)P and Pib2 in the regulation of TORC1, which in turn promoted LMP and nonapoptotic death of stressed cells. Rapamycin prevented the death of the pathogenic yeast Candida albicans during exposure to fluconazole plus a calcineurin inhibitor, suggesting that TORC1 broadly promotes sensitivity to fungistats in yeasts.

Bayesian Network Inference Enables Unbiased Phenotypic Anchoring of Transcriptomic Responses to Cigarette Smoke in Humans

Microarray-based transcriptomic analysis has been demonstrated to hold the opportunity to study the effects of human exposure to, e.g., chemical carcinogens at the whole genome level, thus yielding broad-ranging molecular information on possible carcinogenic effects. Since genes do not operate individually but rather through concerted interactions, analyzing and visualizing networks of genes should provide important mechanistic information, especially upon connecting them to functional parameters, such as those derived from measurements of biomarkers for exposure and carcinogenic risk. Conventional methods such as hierarchical clustering and correlation analyses are frequently used to address these complex interactions but are limited as they do not provide directional causal dependence relationships. Therefore, our aim was to apply Bayesian network inference with the purpose of phenotypic anchoring of modified gene expressions. We investigated a use case on transcriptomic responses to cigarette smoking in humans, in association with plasma cotinine levels as biomarkers of exposure and aromatic DNA-adducts in blood cells as biomarkers of carcinogenic risk. Many of the genes that appear in the Bayesian networks surrounding plasma cotinine, and to a lesser extent around aromatic DNA-adducts, hold biologically relevant functions in inducing severe adverse effects of smoking. In conclusion, this study shows that Bayesian network inference enables unbiased phenotypic anchoring of transcriptomics responses. Furthermore, in all inferred Bayesian networks several dependencies are found which point to known but also to new relationships between the expression of specific genes, cigarette smoke exposure, DNA damaging-effects, and smoking-related diseases, in particular associated with apoptosis, DNA repair, and tumor suppression, as well as with autoimmunity.

Cryptococcus neoformans-induced macrophage lysosome damage crucially contributes to fungal virulence

Upon ingestion by macrophages, Cryptococcus neoformans can survive and replicate intracellularly unless the macrophages become classically activated. The mechanism enabling intracellular replication is not fully understood; neither are the mechanisms that allow classical activation to counteract replication. C. neoformans-induced lysosome damage was observed in infected murine bone marrow-derived macrophages, increased with time, and required yeast viability. To demonstrate lysosome damage in the infected host, we developed a novel flow cytometric method for measuring lysosome damage. Increased lysosome damage was found in C. neoformans-containing lung cells compared with C. neoformans-free cells. Among C. neoformans-containing myeloid cells, recently recruited cells displayed lower damage than resident cells, consistent with the protective role of recruited macrophages. The magnitude of lysosome damage correlated with increased C. neoformans replication. Experimental induction of lysosome damage increased C. neoformans replication. Activation of macrophages with IFN-γ abolished macrophage lysosome damage and enabled increased killing of C. neoformans. We conclude that induction of lysosome damage is an important C. neoformans survival strategy and that classical activation of host macrophages counters replication by preventing damage. Thus, therapeutic strategies that decrease lysosomal damage, or increase resistance to such damage, could be valuable in treating cryptococcal infections.

A time to kill: targeting apoptosis in cancer

The process of apoptosis is essential for maintaining the physiologic balance between cell death and cell growth. This complex process is executed by two major pathways that participate in activating an executioner mechanism leading to chromatin disintegration and nuclear fragmentation. Dysregulation of these pathways often contributes to cancer development and resistance to cancer therapy. Here, we review the most recent discoveries in apoptosis regulation and possible mechanisms for resensitizing tumor cells to therapy.

Molecular mechanism of cell death induced by king cobra (Ophiophagus hannah) venom l-amino acid oxidase

Snake venom LAAOs have been reported to exhibit a wide range of pharmacological activities, including cytotoxic, edema-inducing, platelet aggregation-inducing/platelet aggregation-inhibiting, bactericidal and antiviral activities. A heat-stable form of l-amino acid oxidase isolated from king cobra (Ophiophagus hannah) venom (OH-LAAO) has been shown to exhibit very potent cytotoxicity against human tumorigenic cells but not in their non-tumorigenic counterparts, and the cytotoxicity was due to the apoptosis-inducing effect of the enzyme. In this work, the molecular mechanism of cell death induced by OH-LAAO was investigated. The enzyme exerts its apoptosis-inducing effect presumably via both intrinsic and extrinsic pathways as suggested by the increase in caspase-8 and -9 activities. Oligonucleotide microarray analysis showed that the expression of a total of 178 genes was significantly altered as a result of oxidative stress induced by the hydrogen peroxide generated by the enzyme. Of the 178 genes, at least 27 genes are involved in apoptosis and cell death. These alterations of gene expression was presumably caused by the direct cytotoxic effect of H2O2 generated during the enzymatic reaction, as well as the non-specific oxidative modifications of signaling molecules that eventually lead to apoptosis and cell death. The very substantial up-regulation of cytochrome P450 genes may also contribute to the potent cytotoxic action of OH-LAAO by producing excessive reactive oxygen species (ROS). In conclusion, the potent apoptosis inducing activity of OH-LAAO was likely due to the direct cytotoxic effect of H2O2 generated during the enzymatic reaction, as well as the non-specific oxidation of signalling molecules.

Mitochondrial-mediated apoptosis pathway in alveolar epithelial cells exposed to the metals in combustion-generated particulate matter

Previously a significant mitochondrial impairment was identified in alveolar epithelial cells exposed to metals adsorbed to combustion-generated particulate matter (PM). Due to the critical role of mitochondria in apoptosis, the aim of this study was to investigate the pro-apoptotic potential of metals present in oil fly ash (OFA). A549 cells were exposed to water-soluble components of an OFA sample, containing vanadium [V(IV)], iron [Fe(III)], and nickel [Ni(II)] (68.8, 110.4, and 18 μM, respectively). Experiments were also performed using individual metal solutions. Apoptosis was detected and the mitochondrial role was assessed by a caspase-9 inhibitor (Z-LEHD-FMK). To determine whether the presence of impaired mitochondria in unexposed daughter cells increased apoptosis, an in vitro model was developed that allowed determination of effects until the third cell generation. To specifically examine the toxicity of vanadium (V), that characterize the airborne pollutant examined in this study, p53involvement and metabolic impairment through changes in HIF-1α and Glut-1 expression were determined. OFA and individual metal solutions produced significant apoptosis in the progeny of exposed cells, triggering the intrinsic apoptosis pathway. In apoptosis induced by poorly genotoxic metal V, p53 did not play a significant role. However, V exposure increased nuclear translocation of HIF-1α and expression of the Glut-1 receptor, indicating metabolic impairment due to metal-induced mitochondrial dysfunction. Overall, these results improve our knowledge of the pathogenic role that airborne metals and in particular V exerted in respiratory epithelium.

The links between AKT and two intracellular proteolytic cascades: ubiquitination and autophagy

The serine threonine kinase AKT plays a central role in the regulation of cell survival in a variety of human neoplastic diseases. A series of studies have revealed a connection between AKT signaling and two important protein degradation pathways in mammalian cells: the ubiquitin-proteasome system and autophagy. Two distinct ubiquitination systems have been reported to regulate AKT signaling: K63-linked ubiquitination, which promotes the oncogenic activation of AKT, and K48-linked ubiquitination, which triggers the proteasomal degradation of phosphorylated AKT. Autophagy is an evolutionarily conserved mechanism for the gross disposal and recycling of intracellular proteins in mammalian cells. AKT signaling may play a regulatory role in autophagy; however, the underlying mechanisms have not been fully clarified. Recently, AKT was shown to phosphorylate key molecules involved in the regulation of autophagy. Furthermore, lysosomal co-localization of the AKT-Phafin2 complex is reportedly critical for the induction of autophagy. In this review, we will discuss the connection between AKT, a core intracellular survival regulator, and two major intracellular proteolytic signaling pathways in mammalian cells.

Lysosomal interaction of Akt with Phafin2: a critical step in the induction of autophagy

Autophagy is an evolutionarily conserved mechanism for the gross disposal of intracellular proteins in mammalian cells and dysfunction in this pathway has been associated with human disease. Although the serine threonine kinase Akt is suggested to play a role in this process, little is known about the molecular mechanisms by which Akt induces autophagy. Using a yeast two-hybrid screen, Phafin2 (EAPF or PLEKHF2), a lysosomal protein with a unique structure of N-terminal PH (pleckstrin homology) domain and C-terminal FYVE (Fab 1, YOTB, Vac 1, and EEA1) domain was found to interact with Akt. A sucrose gradient fractionation experiment revealed that both Akt and Phafin2 co-existed in the same lysosome enriched fraction after autophagy induction. Confocal microscopic analysis and BiFC analysis demonstrated that both Akt and Phafin2 accumulate in the lysosome after induction of autophagy. BiFC analysis using PtdIns (3)P interaction defective mutant of Phafin2 demonstrated that lysosomal accumulation of the Akt-Phafin2 complex and subsequent induction of autophagy were lysosomal PtdIns (3)P dependent events. Furthermore, in murine macrophages, both Akt and Phafin2 were required for digestion of fluorescent bacteria and/or LPS-induced autophagy. Taken together, these findings establish that lysosomal accumulation of Akt and Phafin2 is a critical step in the induction of autophagy via an interaction with PtdIns (3)P.

Maturation of autophagosomes and endosomes: a key role for Rab7

Macroautophagy is an important route in cellular maintenance, in the breakdown and reuse of intracellular materials. It is closely related to endocytosis, the means by which the cell can absorb extracellular material, as both macroautophagy and endocytosis have converging steps and common participating molecules. The point where autophagosomes and endosomes fuse with lysosomes to permit for the final degradation of their contents is important. One of the most substantial molecules in the maturation of autophagosomes/endosomes is Rab7, a member of small GTPases. Rab7 designates the maturation of endosomes and also autophagosomes, directing the trafficking of cargos along microtubules, and finally, participating in the fusion step with lysosomes. Rab7 is an effective multifunctional regulator of autophagy and endocytosis. Since many aggregation-based diseases, e.g. age-related macular degeneration of the eye (AMD) and Alzheimer's disease are due of malfunctioning in the autophagic process, the management of Rab7 activity might hold potential as a therapeutic target against these diseases.

The PtdIns3P-binding protein Phafin 2 mediates epidermal growth factor receptor degradation by promoting endosome fusion

Phosphatidylinositol 3-phosphate (PtdIns3P) orchestrates endosomal cargo transport, fusion and motility by recruiting FYVE or PX domain-containing effector proteins to endosomal membranes. In an attempt to discover novel PtdIns3P effectors involved in the termination of growth factor receptor signalling, we performed an siRNA screen for epidermal growth factor (EGF) degradation, targeting FYVE and PX domain proteins in the human proteome. This screen identified several potential regulators of EGF degradation, including HRS (used as positive control), PX kinase, MTMR4 and Phafin2/PLEKHF2. As Phafin2 has not previously been shown to be required for EGF receptor (EGFR) degradation, we performed further functional studies on this protein. Loss of Phafin2 was found to decrease early endosome size, whereas overexpression of Phafin2 resulted in enlarged endosomes. Moreover, both the EGFR and the fluid-phase marker dextran were retained in abnormally small endosomes in Phafin2-depleted cells. In yeast two-hybrid analysis we identified Phafin2 as a novel interactor of the endosomal-tethering protein EEA1, and Phafin2 colocalized strongly with EEA1 in microdomains of the endosome membrane. Our results suggest that Phafin2 controls receptor trafficking and fluid-phase transport through early endosomes by facilitating endosome fusion in concert with EEA1.

Effects on human transcriptome of mutated BRCA1 BRCT domain: a microarray study

BACKGROUND

BRCA1 (breast cancer 1, early onset) missense mutations have been detected in familial breast and ovarian cancers, but the role of these variants in cancer predisposition is often difficult to ascertain. In this work, the molecular mechanisms affected in human cells by two BRCA1 missense variants, M1775R and A1789T, both located in the second BRCT (BRCA1 C Terminus) domain, have been investigated. Both these variants were isolated from familial breast cancer patients and the study of their effect on yeast cell transcriptome has previously provided interesting clues to their possible role in the pathogenesis of breast cancer.

METHODS

We compared by Human Whole Genome Microarrays the expression profiles of HeLa cells transfected with one or the other variant and HeLa cells transfected with BRCA1 wild-type. Microarray data analysis was performed by three comparisons: M1775R versus wild-type (M1775RvsWT-contrast), A1789T versus wild-type (A1789TvsWT-contrast) and the mutated BRCT domain versus wild-type (MutvsWT-contrast), considering the two variants as a single mutation of BRCT domain.

RESULTS

201 differentially expressed genes were found in M1775RvsWT-contrast, 313 in A1789TvsWT-contrast and 173 in MutvsWT-contrast. Most of these genes mapped in pathways deregulated in cancer, such as cell cycle progression and DNA damage response and repair.

CONCLUSIONS

Our results represent the first molecular evidence of the pathogenetic role of M1775R, already proposed by functional studies, and give support to a similar role for A1789T that we first hypothesized based on the yeast cell experiments. This is in line with the very recently suggested role of BRCT domain as the main effector of BRCA1 tumor suppressor activity.

Immune complex-mediated co-ligation of the BCR with FcγRIIB results in homeostatic apoptosis of B cells involving Fas signalling that is defective in the MRL/Lpr model of systemic lupus erythematosus

Negative regulation of B cell activation by cognate immune complexes plays an important homeostatic role in suppressing B cell hyperactivity and preventing consequent autoimmunity. Immune complexes co-ligate the BCR and FcγRIIB resulting in both growth arrest and apoptosis. We now show that such apoptotic signalling involves induction and activation of p53 and its target genes, the pro-apoptotic Bcl-2 family members, Bad and Bid, as well as nuclear export of p53. Collectively, these events result in destabilisation of the mitochondrial and lysosomal compartments with consequent activation and interplay of executioner caspases and endosomal-derived proteases. In addition, the upregulation of Fas and FasL with consequent activation of caspase 8-dependent death receptor signalling is required to facilitate efficient apoptosis of B cells. Consistent with this role for Fas death receptor signalling, apoptosis resulting from co-ligation of the BCR and FcγRIIB is defective in B cells from Fas-deficient MRL/MpJ-Fas(lpr) mice. As these mice develop spontaneous, immune complex-driven lupus-like glomerulonephritis, targeting this FcγRIIB-mediated apoptotic pathway may therefore have novel therapeutic implications for systemic autoimmune disease.

Functional characterization of the 19q12 amplicon in grade III breast cancers

INTRODUCTION

The 19q12 locus is amplified in a subgroup of oestrogen receptor (ER)-negative grade III breast cancers. This amplicon comprises nine genes, including cyclin E1 (CCNE1), which has been proposed as its 'driver'. The aim of this study was to identify the genes within the 19q12 amplicon whose expression is required for the survival of cancer cells harbouring their amplification.

METHODS

We investigated the presence of 19q12 amplification in a series of 313 frozen primary breast cancers and 56 breast cancer cell lines using microarray comparative genomic hybridisation (aCGH). The nine genes mapping to the smallest region of amplification on 19q12 were silenced using RNA interference in phenotypically matched breast cancer cell lines with (MDA-MB-157 and HCC1569) and without (Hs578T, MCF7, MDA-MB-231, ZR75.1, JIMT1 and BT474) amplification of this locus. Genes whose silencing was selectively lethal in amplified cells were taken forward for further validation. The effects of cyclin-dependent kinase 2 (CDK2) silencing and chemical inhibition were tested in cancer cells with and without CCNE1 amplification.

RESULTS

19q12 amplification was identified in 7.8% of ER-negative grade III breast cancer. Of the nine genes mapping to this amplicon, UQCRFS1, POP4, PLEKHF1, C19ORF12, CCNE1 and C19ORF2 were significantly over-expressed when amplified in primary breast cancers and/or breast cancer cell lines. Silencing of POP4, PLEKHF1, CCNE1 and TSZH3 selectively reduced cell viability in cancer cells harbouring their amplification. Cancer cells with CCNE1 amplification were shown to be dependent on CDK2 expression and kinase activity for their survival.

CONCLUSIONS

The 19q12 amplicon may harbour more than a single 'driver', given that expression of POP4, PLEKHF1, CCNE1 and TSZH3 is required for the survival of cancer cells displaying their amplification. The observation that cancer cells harbouring CCNE1 gene amplification are sensitive to CDK2 inhibitors provides a rationale for the testing of these chemical inhibitors in a subgroup of patients with ER-negative grade III breast cancers.

Autophagy, mitochondria and oxidative stress: cross-talk and redox signalling

Reactive oxygen and nitrogen species change cellular responses through diverse mechanisms that are now being defined. At low levels, they are signalling molecules, and at high levels, they damage organelles, particularly the mitochondria. Oxidative damage and the associated mitochondrial dysfunction may result in energy depletion, accumulation of cytotoxic mediators and cell death. Understanding the interface between stress adaptation and cell death then is important for understanding redox biology and disease pathogenesis. Recent studies have found that one major sensor of redox signalling at this switch in cellular responses is autophagy. Autophagic activities are mediated by a complex molecular machinery including more than 30 Atg (AuTophaGy-related) proteins and 50 lysosomal hydrolases. Autophagosomes form membrane structures, sequester damaged, oxidized or dysfunctional intracellular components and organelles, and direct them to the lysosomes for degradation. This autophagic process is the sole known mechanism for mitochondrial turnover. It has been speculated that dysfunction of autophagy may result in abnormal mitochondrial function and oxidative or nitrative stress. Emerging investigations have provided new understanding of how autophagy of mitochondria (also known as mitophagy) is controlled, and the impact of autophagic dysfunction on cellular oxidative stress. The present review highlights recent studies on redox signalling in the regulation of autophagy, in the context of the basic mechanisms of mitophagy. Furthermore, we discuss the impact of autophagy on mitochondrial function and accumulation of reactive species. This is particularly relevant to degenerative diseases in which oxidative stress occurs over time, and dysfunction in both the mitochondrial and autophagic pathways play a role.

The phosphoinositide-associated protein Rush hour regulates endosomal trafficking in Drosophila

Endocytosis regulates multiple cellular processes, including the protein composition of the plasma membrane, intercellular signaling, and cell polarity. We have identified the highly conserved protein Rush hour (Rush) and show that it participates in the regulation of endocytosis. Rush localizes to endosomes via direct binding of its FYVE (Fab1p, YOTB, Vac1p, EEA1) domain to phosphatidylinositol 3-phosphate. Rush also directly binds to Rab GDP dissociation inhibitor (Gdi), which is involved in the activation of Rab proteins. Homozygous rush mutant flies are viable but show genetic interactions with mutations in Gdi, Rab5, hrs, and carnation, the fly homologue of Vps33. Overexpression of Rush disrupts progression of endocytosed cargo and increases late endosome size. Lysosomal marker staining is decreased in Rush-overexpressing cells, pointing to a defect in the transition between late endosomes and lysosomes. Rush also causes formation of endosome clusters, possibly by affecting fusion of endosomes via an interaction with the class C Vps/homotypic fusion and vacuole protein-sorting (HOPS) complex. These results indicate that Rush controls trafficking from early to late endosomes and from late endosomes to lysosomes by modulating the activity of Rab proteins.

Cell sensitivity to oxidative stress is influenced by ferritin autophagy

To test the consequences of lysosomal degradation of differently iron-loaded ferritin molecules and to mimic ferritin autophagy under iron-overload and normal conditions, J774 cells were allowed to endocytose heavily iron loaded ferritin, probably with some adventitious iron (Fe-Ft), or iron-free apo-ferritin (apo-Ft). When cells subsequently were exposed to a bolus dose of hydrogen peroxide, apo-Ft prevented lysosomal membrane permeabilization (LMP), whereas Fe-Ft enhanced LMP. A 4-h pulse of Fe-Ft initially increased oxidative stress-mediated LMP that was reversed after another 3h under standard culture conditions, suggesting that lysosomal iron is rapidly exported from lysosomes, with resulting upregulation of apo-ferritin that supposedly is autophagocytosed, thereby preventing LMP by binding intralysosomal redox-active iron. The obtained data suggest that upregulation of the stress protein ferritin is a rapid adaptive mechanism that counteracts LMP and ensuing apoptosis during oxidative stress. In addition, prolonged iron starvation was found to induce apoptotic cell death that, interestingly, was preceded by LMP, suggesting that LMP is a more general phenomenon in apoptosis than so far recognized. The findings provide new insights into aging and neurodegenerative diseases that are associated with enhanced amounts of cellular iron and show that lysosomal iron loading sensitizes to oxidative stress.

Persistence of effector memory Th1 cells is regulated by Hopx

Th1 cells are prominent in inflamed tissue, survive conventional immunosuppression, and are believed to play a pivotal role in driving chronic inflammation. Here, we identify homeobox only protein (Hopx) as a critical and selective regulator of the survival of Th1 effector/memory cells, both in vitro and in vivo. Expression of Hopx is induced by T-bet and increases upon repeated antigenic restimulation of Th1 cells. Accordingly, the expression of Hopx is low in peripheral, naïve Th cells, but highly up-regulated in terminally differentiated effector/memory Th1 cells of healthy human donors. In murine Th1 cells, Hopx regulates the expression of genes involved in regulation of apoptosis and survival and makes them refractory to Fas-induced apoptosis. In vivo, adoptively transferred Hopx-deficient murine Th1 cells do not persist. Consequently, they cannot induce chronic inflammation in murine models of transfer-induced colitis and arthritis, demonstrating a key role of Hopx for Th1-mediated immunopathology.

Signaling different pathways of cell death: Abrin induced programmed necrosis in U266B1 cells

Abrin is a type II ribosome-inactivating protein comprising of two subunits, A and B. Of the two, the A-subunit harbours the RNA-N-glycosidase activity and the B subunit is a galactose specific lectin that enables the entry of the protein inside the cell. Abrin inhibits protein synthesis and has been reported to induce apoptosis in several cell types. Based on these observations abrin is considered to have potential for the construction of immunotoxin in cell targeted therapy. Preliminary data from our laboratory however showed that although abrin inhibited the protein synthesis in all cell types, the mode of cell death varied. The aim of the present study was therefore to understand different death pathways induced by abrin in different cells. We used the human B cell line, U266B1 and compared it with the earlier studied T cell line Jurkat, for abrin-mediated inhibition of protein translation as well as cell death. While abrin triggered programmed apoptosis in Jurkat cells in a caspase-dependent manner, it induced programmed necrosis in U266B1 cells in a caspase-independent manner, even when there was reactive oxygen species production and loss of mitochondrial membrane potential. The data revealed that abrin-mediated necrosis involves lysosomal membrane permeabilization and release of cathepsins from the lysosomes. Importantly, the choice of abrin-mediated death pathway in the cells appears to depend on which of the two events occurs first: lysosomal membrane permeabilization or loss of mitochondrial membrane potential that decides cell death by necrosis or apoptosis.

Redox activity within the lysosomal compartment: implications for aging and apoptosis

The lysosome is a redox-active compartment containing low-mass iron and copper liberated by autophagic degradation of metalloproteins. The acidic milieu and high concentration of thiols within lysosomes will keep iron in a reduced (ferrous) state, which can react with endogenous or exogenous hydrogen peroxide. Consequent intralysosomal Fenton reactions may give rise to the formation of lipofuscin or "age pigment" that accumulates in long-lived postmitotic cells that cannot dilute it by division. Extensive accumulation of lipofuscin seems to hinder normal autophagy and may be an important factor behind aging and age-related pathologies. Enhanced oxidative stress causes lysosomal membrane permeabilization, with ensuing relocation to the cytosol of iron and lysosomal hydrolytic enzymes, with resulting apoptosis or necrosis. Lysosomal copper is normally not redox active because it will form non-redox-active complexes with various thiols. However, if cells are exposed to lysosomotropic chelators that do not bind all the copper coordinates, highly redox-active complexes may form, with ensuing extensive lysosomal Fenton-type reactions and loss of lysosomal stability. Because many malignancies seem to have increased amounts of copper-containing macromolecules that are turned over by autophagy, it is conceivable that lysosomotropic copper chelators may be used in the future in ROS-based anticancer therapies.

Combating apoptosis and multidrug resistant cancers by targeting lysosomes

Acquired therapy resistance is one of the prime obstacles for successful cancer treatment. Partial resistance is often acquired already during an early face of tumor development when genetic changes causing defects in classical caspase-dependent apoptosis pathway provide transformed cells with a growth advantage by protecting them against various apoptosis inducing stimuli including transforming oncogenes themselves and host immune system. Apoptosis defective cells are further selected during tumor progression and finally by apoptosis inducing treatments. Another form of resistance, multidrug resistance, arises during cancer treatment when cancer cells with effective efflux of cytotoxic agents escape the therapy. Remarkably, induction of lysosomal membrane permeabilization has recently emerged as an effective way to kill apoptosis resistant cancer cells and some lysosome targeting drugs can also re-sensitize multidrug resistant cells to classical chemotherapy. In this review, we highlight recent data on lysosomal cell death pathways and their implications for the future treatment of apoptosis defective and multidrug resistant aggressive tumors.

Regulation of apoptosis-associated lysosomal membrane permeabilization

Lysosomal membrane permeabilization (LMP) occurs in response to a large variety of cell death stimuli causing release of cathepsins from the lysosomal lumen into the cytosol where they participate in apoptosis signaling. In some settings, apoptosis induction is dependent on an early release of cathepsins, while under other circumstances LMP occurs late in the cell death process and contributes to amplification of the death signal. The mechanism underlying LMP is still incompletely understood; however, a growing body of evidence suggests that LMP may be governed by several distinct mechanisms that are likely engaged in a death stimulus- and cell-type-dependent fashion. In this review, factors contributing to permeabilization of the lysosomal membrane including reactive oxygen species, lysosomal membrane lipid composition, proteases, p53, and Bcl-2 family proteins, are described. Potential mechanisms to safeguard lysosomal integrity and confer resistance to lysosome-dependent cell death are also discussed.

Prednisolone causes anxiety- and depression-like behaviors and altered expression of apoptotic genes in mice hippocampus

Glucocorticoids are known to cause psychiatric disorders including depression. Prednisolone (PSL) is one of the most widely used synthetic glucocorticoids to treat various medical diseases; however, little is known about PSL-induced behavioral changes and its molecular basis in the brain. Growing evidence has implicated that hippocampal remodeling or damage play a role in the pathogenic effect of glucocorticoids. In this study, mice were administered PSL (50 or 100mg/kg) or vehicle for 6 or 7 days and subjected to a series of behavioral tests, i.e., open field, elevated plus maze, prepulse inhibition, forced swim, and tail suspension tests. Hippocampal tissues were subject to microarray analysis using the GeneChip Mouse Genome 430 2.0 Array (Affymetrix) containing 45,101 probes of transcripts. Increased anxiety- and depression-like behaviors assessed with open field, elevated plus maze, and tail suspension tests were observed. Microarray analysis detected 108 transcripts with a fold change of >2.0 or <0.5 in which many cell-death-related genes were found. The microarray data was validated by quantitative reverse transcriptase-polymerase chain reaction analysis. Our results demonstrated that PSL causes anxiety- and depression-like behaviors, and suggest that altered gene expressions related to hippocampal remodeling or damage are involved in the effect of PSL on such behaviors.

Lipotoxicity-mediated cell dysfunction and death involve lysosomal membrane permeabilization and cathepsin L activity

Lipotoxicity, which is triggered when cells are exposed to elevated levels of free fatty acids, involves cell dysfunction and apoptosis and is emerging as an underlying factor contributing to various pathological conditions including disorders of the central nervous system and diabetes. We have shown that palmitic acid (PA)-induced lipotoxicity (PA-LTx) in nerve growth factor-differentiated PC12 (NGFDPC12) cells is linked to an augmented state of cellular oxidative stress (ASCOS) and apoptosis and that these events are inhibited by docosahexanoic acid (DHA). The mechanisms of PA-LTx in nerve cells are not well understood, but our previous findings indicate that it involves ROS generation, mitochondrial membrane permeabilization (MMP), and caspase activation. The present study used nerve growth factor differentiated PC12 cells (NGFDPC12 cells) and found that lysosomal membrane permeabilization (LMP) is an early event during PA-induced lipotoxicity that precedes MMP and apoptosis. Cathepsin L, but not cathepsin B, is an important contributor in this process since its pharmacological inhibition significantly attenuated LMP, MMP, and apoptosis. In addition, co-treatment of NGFDPC12 cells undergoing lipotoxicity with DHA significantly reduced LMP, suggesting that DHA acts by antagonizing upstream signals leading to lysosomal dysfunction. These results suggest that LMP is a key early mediator of lipotoxicity and underscore the value of interventions targeting upstream signals leading to LMP for the treatment of pathological conditions associated with lipotoxicity.

Cationic poly(amidoamine) dendrimer induces lysosomal apoptotic pathway at therapeutically relevant concentrations

Poly(amidoamine) (PAMAM) dendrimers carrying different amounts of surface amino groups were synthesized and tested for their effects on cellular cytotoxicity, lysosomal pH, and mitochondria-dependent apoptosis. In KB cells, the PAMAM dendrimers were taken up into the lysosomal compartment, and they increased the lysosomal pH and cytotoxicity as a function of the number of surface amino groups on the dendrimer. PAMAM dendrimers that were surface-neutralized by acetylation of >80% of the surface amino groups failed to show any cytotoxicity. The positively charged, amine-terminated PAMAM dendrimer induced cellular apoptosis, as demonstrated by mitochondrial membrane potential changes and caspase activity measurements. These results suggest that PAMAM dendrimers are endocytosed into the KB cells through a lysosomal pathway, leading to lysosomal alkalinization and induction of mitochondria-mediated apoptosis.