HSpin1, a transmembrane protein interacting with Bcl-2/Bcl-xL, induces a caspase-independent autophagic cell death

Deficiency of spns1 exacerbates per- and polyfluoroalkyl substances mediated hepatic toxicity and steatosis in zebrafish (Danio rerio)

Per- and polyfluoroalkyl substances (PFAS) are man-made long-lasting chemical compounds that are found in everyday household items. Today they occur in the environment as a major group of pollutants. These compounds are broadly used in commercial product preparation such as, for food packaging, nonstick coatings, and firefighting foam. In humans, PFAS can cause immune disorders, impaired fetal development, abnormal skeletal tissue development, osteoarthritis, thyroid dysfunctions, cholesterol changes, affect insulin regulation and lipid metabolism, and are also involved in the development of fatty liver disease. In the current study, we investigated the effect of low, but physiologically relevant, concentrations of perfluorooctanoic acid (PFOA), heptafluorobutyric acid (HFBA), and perfluorotetradecanoic acid (PFTA) on gene expression markers of an inflammatory response (tnfa, il-1b, il-6, rplp0, edem1, and dnajc3a), unfolded protein response (UPR) (bip, atf4a, atf6, xbp1, and ddit3), senescence (p21, pai1, smp30, mdm2, and baxa), lipogenesis (scd1, acc, srebp1, pparγ, and fasn) and autophagy (p62, atg3, atg7, rab7, lc3b, and becn1) in AB wild-type (+/+), spns1-wt sibling (+/+), (+/-) and spns1 homozygous mutant (-/-) zebrafish embryos. Exposure to PFOA and HFBA (50 and 100 nM) specifically modulated inflammatory, UPR, senescence, lipogenic, and autophagy signaling in spns1-wt (+/+), (+/-), and spns1-mutant (-/-) zebrafish embryos. Furthermore, PFOA, but not HFBA, upregulated lipogenic-related gene expression and enhanced hepatic steatosis in spns1-wt (+/+), (+/-) zebrafish embryos. Combined exposure to PFOA, HFBA, and PFTA differentially expressed inflammatory, senescence, lipogenic, and autophagy-associated gene expression in spns1-mutant (-/-) zebrafish embryos compared with spns1-wt (+/+), (+/-) and AB-wt (+/+) zebrafish embryos. In addition, chronic exposure (∼2 months) to PFOA (120-600 nM) upregulated the expression of hepatic lipogenic and steatosis biomarkers in AB-wt (+/+) zebrafish. Collectively, our data suggest that acute/chronic physiologically relevant concentrations of PFOA upregulate inflammatory, UPR, senescence, and lipogenic signaling in spns1-wt (+/+), (+/-) and spns1-mutant (-/-) zebrafish embryos as well as in two-month-old AB-wt zebrafish, by targeting autophagy and hence induces toxicity that could promote nonalcoholic fatty liver disease.

A Study on the Mechanism of Action of Galangal in the Treatment of Gastric Cancer Using Network Pharmacology Technology

To study the mechanism of galangal in the treatment of gastric cancer by network pharmacology. The TCMSP database was used to collect the effective compounds and potential targets of galangal, and the genes associated with gastric cancer were obtained through the GeneCards database, and Venn obtained the interaction genes of the effective compound targets of galangal and gastric cancer targets, plotted the interaction genes into PPI networks, and screened out key targets. The interacting genes were imported into Metascape database for GO enrichment analysis and KEGG signal enrichment. A total of 13 active compounds and 207 potential downstream target genes were screened by TCMSP database. Have 5222 gastric cancer target genes through GeneCards database, there were a total of 150 interactive genes and 6 key genes: TP53, AKT1, JUN, HSP90AA1, IL6, and CASP3. These interacting genes involved 30 typical GO entries and 20 KEGG signals. Galangal may play a role in the treatment of gastric cancer by means of multi-component, multi-target and multi-signal pathway.

Emerging Significance of Ginsenosides as Potentially Reversal Agents of Chemoresistance in Cancer Therapy

Chemoresistance has become a prevalent phenomenon in cancer therapy, which alleviates the effect of chemotherapy and makes it difficult to break the bottleneck of the survival rate of tumor patients. Current approaches for reversing chemoresistance are poorly effective and may cause numerous new problems. Therefore, it is urgent to develop novel and efficient drugs derived from natural non-toxic compounds for the reversal of chemoresistance. Researches in vivo and in vitro suggest that ginsenosides are undoubtedly low-toxic and effective options for the reversal of chemoresistance. The underlying mechanism of reversal of chemoresistance is correlated with inhibition of drug transporters, induction of apoptosis, and modulation of the tumor microenvironment(TME), as well as the modulation of signaling pathways, such as nuclear factor erythroid-2 related factor 2 (NRF2)/AKT, lncRNA cancer susceptibility candidate 2(CASC2)/ protein tyrosine phosphatase gene (PTEN), AKT/ sirtuin1(SIRT1), epidermal growth factor receptor (EGFR)/ phosphatidylinositol 3-kinase (PI3K)/AKT, PI3K/AKT/ mammalian target of rapamycin(mTOR) and nuclear factor-κB (NF-κB). Since the effects and the mechanisms of ginsenosides on chemoresistance reversal have not yet been reviewed, this review summarized comprehensively experimental data in vivo and in vitro to elucidate the functional roles of ginsenosides in chemoresistance reversal and shed light on the future research of ginsenosides.

Perfluorooctane sulfonate induces autophagy-dependent lysosomal membrane permeabilization by weakened interaction between tyrosinated alpha-tubulin and spinster 1

Perfluorooctane sulfonate (PFOS) is one kind of persistent organic pollutants. In previous study, we found that PFOS induced autophagy-dependent lysosomal membrane permeabilization (LMP) in hepatocytes, and siRNA against lysosomal permease spinster 1 (SPNS1) relieved PFOS-induced LMP. However, whether and how SPNS1 functioned as the link between autophagy and LMP was still not defined. In this study, we constructed a stable cell line expressing high levels of SPNS1. We found that SPNS1 interacted specifically with α-tubulin of tyrosinated isotype by pull-down assay. After treatment with PFOS, the level of tyrosinated α-tubulin was autophagy-dependently decreased. SPNS1-tyrosinated α-tubulin interaction was disrupted subsequently, which led to LMP eventually. We also found that stable high-expression of SPNS1 in hepatocytes accelerated lysosomal acidification, and deteriorated PFOS-induced LMP. This study pointed out that SPNS1-tyrosinated α-tubulin interaction mediated the cross-talk between autophagy and LMP induced by PFOS, shedding new light on the mechanism of PFOS hepatotoxicity.

CD142 plays a key role in the carcinogenesis of gastric adenocarcinoma by inhibiting BCL2-dependent autophagy

CD142 is expressed on the surface of multiple malignant tumors and contributes to various carcinogenesis. However, the role of CD142 in the pathogenesis of GAC remains unclear. This study aimed to investigate the role of CD142 in GAC carcinogenesis. Our results showed that CD142 expression was significantly increased in GAC cancer tissues, especially in those with significant invasion or metastasis. The invasion and migration of CD142-positive SNU16 cells were significantly increased compared with those of CD142-negative cells. Moreover, CD142 overexpression promoted the invasion and migration of SGC083 cells, but CD142 silencing was contrary. In addition, there was a positive correlation between CD142 expression of cancer tissues and serum IL-8 levels. CD142 overexpression promotes IL-8 production in SGC083 cells. In vivo analysis showed that the implantation of CD142-positive SNU16 cells promoted the growth of xenograft tumor and the production of IL-8. Mechanistically, CD142 silencing not only inhibited the expression of BCL2 and the interaction between BCL2 and Beclin1, but also promoted the autophagic response in SGC083. Furthermore, CD142 silencing-induced IL-8 degradation was recovered by treatment of autophagy inhibitor 3-MA. CD142 can inhibit autophagic cell death and the autophagic degradation of IL-8 in GAC, which exerts an effective effect on GAC carcinogenesis.

The role of cell signaling in the crosstalk between autophagy and apoptosis in the regulation of tumor cell survival in response to sorafenib and neratinib

The molecular mechanisms by which tumor cells survive or die following therapeutic interventions are complex. There are three broadly defined categories of cell death processes: apoptosis (Type I), autophagic cell death (Type II), and necrosis (Type III). In hematopoietic tumor cells, the majority of toxic stimuli cause these cells to undergo a death process called apoptosis; apoptosis specifically involves the cleavage of DNA into large defined pieces and their subsequent localization in vesicles. Thus, 'pure' apoptosis largely lacks inflammatory potential. In carcinomas, however, the mechanisms by which tumor cells ultimately die are considerably more complex. Although the machinery of apoptosis is engaged by toxic stimuli, other processes such as autophagy ("self-eating") and replicative cell death can lead to observations that do not simplistically correspond to any of the individual Type I-III formalized death categories. The 'hybrid' forms of cell death observed in carcinoma cells result in cellular materials being released into the extracellular space without packaging, which promotes inflammation, potentially leading to the accelerated re-growth of surviving tumor cells by macrophages. Drugs as single agents or in combinations can simultaneously initiate signaling via both apoptotic and autophagic pathways. Based on the tumor type and its oncogene drivers, as well as the drug(s) being used and the duration and intensity of the autophagosome signal, apoptosis and autophagy have the potential to act in concert to kill or alternatively that the actions of either pathway can act to suppress signaling by the other pathway. And, there also is evidence that autophagic flux, by causing lysosomal protease activation, with their subsequent release into the cytosol, can directly mediate killing. This review will discuss the interactive biology between apoptosis and autophagy in carcinoma cells. Finally, the molecular actions of the FDA-approved drugs neratinib and sorafenib, and how they enhance both apoptotic and toxic autophagic processes, alone or in combination with other agents, is discussed in a bench-to-bedside manner.

Glucose Transport and Transporters in the Endomembranes

Glucose is a basic nutrient in most of the creatures; its transport through biological membranes is an absolute requirement of life. This role is fulfilled by glucose transporters, mediating the transport of glucose by facilitated diffusion or by secondary active transport. GLUT (glucose transporter) or SLC2A (Solute carrier 2A) families represent the main glucose transporters in mammalian cells, originally described as plasma membrane transporters. Glucose transport through intracellular membranes has not been elucidated yet; however, glucose is formed in the lumen of various organelles. The glucose-6-phosphatase system catalyzing the last common step of gluconeogenesis and glycogenolysis generates glucose within the lumen of the endoplasmic reticulum. Posttranslational processing of the oligosaccharide moiety of glycoproteins also results in intraluminal glucose formation in the endoplasmic reticulum (ER) and Golgi. Autophagic degradation of polysaccharides, glycoproteins, and glycolipids leads to glucose accumulation in lysosomes. Despite the obvious necessity, the mechanism of glucose transport and the molecular nature of mediating proteins in the endomembranes have been hardly elucidated for the last few years. However, recent studies revealed the intracellular localization and functional features of some glucose transporters; the aim of the present paper was to summarize the collected knowledge.

Stories of spinster with various faces: from courtship rejection to tumor metastasis rejection

The Drosophila spinster (spin) mutant was isolated as a mutant that showed abnormal morphology and function in the nervous system. The spin defect induces neural degeneration similar to human lysosomal storage diseases. Various studies have shown that Spin proteins are localized in lysosomes and participate in the late stages of the autophagic process. Vertebrates have three spinster orthologs, Spns1, Spns2, and Spns3. A defect in Spns1 caused a short lifespan with aberrant lysosomal function in zebrafish. Spns2 was originally isolated as the gene responsible for abnormal heart development and was identified as a sphingosine 1-phosphate transporter in zebrafish. An endothelial cell-specific defect in Spns2 resulted in impaired egress of lymphocytes and the prevention of tumor metastasis in mice. Herein, I reviewed the history of spin/Spns research and discussed the conserved and newly diverged spin/Spns function and possible implications for human diseases.

Autophagy: Dual Response in the Development of Hepatocellular Carcinoma

Autophagy is an evolutionary conserved intracellular mechanism which helps eukaryotic cells in maintaining their metabolic state to afford high-efficiency energy requirements. In the physiology of a normal liver and the pathogenesis of liver diseases, autophagy plays a crucial role. Autophagy has been found to be both upregulated and downregulated in different cancers providing the evidence that autophagy plays a dual role in suppressing and promoting cell survival. Hepatocellular carcinoma (HCC) is the most common primary liver cancer and the major leading cause of cancer mortality worldwide. In light of its high complexity and poor prognosis, it is essential to improve our understanding of autophagy’s role in HCC. In this review, we summarize the dual mechanism of autophagy in the development of HCC and elucidate the currently used therapeutic strategies for anti-HCC therapy.

Characteristics of 29 novel atypical solute carriers of major facilitator superfamily type: evolutionary conservation, predicted structure and neuronal co-expression

Solute carriers (SLCs) are vital as they are responsible for a major part of the molecular transport over lipid bilayers. At present, there are 430 identified SLCs, of which 28 are called atypical SLCs of major facilitator superfamily (MFS) type. These are MFSD1, 2A, 2B, 3, 4A, 4B, 5, 6, 6 L, 7, 8, 9, 10, 11, 12, 13A, 14A and 14B; SV2A, SV2B and SV2C; SVOP and SVOPL; SPNS1, SPNS2 and SPNS3; and UNC93A and UNC93B1. We studied their fundamental properties, and we also included CLN3, an atypical SLC not yet belonging to any protein family (Pfam) clan, because its involvement in the same neuronal degenerative disorders as MFSD8. With phylogenetic analyses and bioinformatic sequence comparisons, the proteins were divided into 15 families, denoted atypical MFS transporter families (AMTF1-15). Hidden Markov models were used to identify orthologues from human to Drosophila melanogaster and Caenorhabditis elegans Topology predictions revealed 12 transmembrane segments (for all except CLN3), corresponding to the common MFS structure. With single-cell RNA sequencing and in situ proximity ligation assay on brain cells, co-expressions of several atypical SLCs were identified. Finally, the transcription levels of all genes were analysed in the hypothalamic N25/2 cell line after complete amino acid starvation, showing altered expression levels for several atypical SLCs.

The Complex Link between Apoptosis and Autophagy: a Promising New Role for RB

Physiological processes, as autophagy, proliferation and apoptosis are affected during carcinogenesis. Restoring cellular sensitivity to apoptotic stimuli, such as the antineoplastic cocktails, has been explored as a strategy to eliminate cancer cells. Autophagy, a physiological process of recycling organelles and macromolecules can be deviated from homeostasis to support cancer cells survival, proliferation, escape from apoptosis, and therapy resistance. The relationship between autophagy and apoptosis is complex and many stimuli can induce both processes. Most chemotherapeutic agents induce autophagy and it is not clear whether and how this chemotherapy-induced autophagy might contribute to resistance to apoptosis. Here, we review current strategies to sensitize cancer cells by interfering with autophagy. Moreover, we discuss a new link between autophagy and apoptosis: the tumor suppressor retinoblastoma protein (RB). Inactivation of RB is one of the earliest and more frequent hallmarks of cancer transformation, known to control cell cycle progression and apoptosis. Therefore, understanding RB functions in controlling cell fate is essential for an effective translation of RB status in cancer samples to the clinical outcome.

L-leucine and SPNS1 coordinately ameliorate dysfunction of autophagy in mouse and human Niemann-Pick type C disease

Lysosomal storage disorders are characterized by progressive accumulation of undigested macromolecules within the cell due to lysosomal dysfunction. 573C10 is a Schwann cell line derived from a mouse model of Niemann-Pick type C disease-1, NPC (−/−). Under serum-starved conditions, NPC (−/−) cells manifested impaired autophagy accompanied by an increase in the amount of p62 and lysosome enlargement. Addition of L-leucine to serum-starved NPC (−/−) cells ameliorated the enlargement of lysosomes and the p62 accumulation. Similar autophagy defects were observed in NPC (−/−) cells even without serum starvation upon the knockdown of Spinster-like 1 (SPNS1), a putative transporter protein thought to function in lysosomal recycling. Conversely, SPNS1 overexpression impeded the enlargement of lysosomes, p62 accumulation and mislocalization of the phosphorylated form of the mechanistic Target of rapamycin in NPC (−/−) cells. In addition, we found a reduction in endogenous SPNS1 expression in fibroblasts derived from NPC-1 patients compared with normal fibroblasts. We propose that SPNS1-dependent L-leucine export across the lysosomal membrane is a key step for triggering autophagy, and that this mechanism is impaired in NPC-1.

An integrative genomics approach identifies novel pathways that influence candidaemia susceptibility

Candidaemia is a bloodstream infection caused by Candida species that primarily affects specific groups of at-risk patients. Because only small candidaemia patient cohorts are available, classical genome wide association cannot be used to identify Candida susceptibility genes. Therefore, we have applied an integrative genomics approach to identify novel susceptibility genes and pathways for candidaemia. Candida-induced transcriptome changes in human primary leukocytes were assessed by RNA sequencing. Genetic susceptibility to candidaemia was assessed using the Illumina immunochip platform for genotyping of a cohort of 217 patients. We then integrated genetics data with gene-expression profiles, Candida-induced cytokine production capacity, and circulating concentrations of cytokines. Based on the intersection of transcriptome pathways and genomic data, we prioritized 31 candidate genes for candidaemia susceptibility. This group of genes was enriched with genes involved in inflammation, innate immunity, complement, and hemostasis. We then validated the role of MAP3K8 in cytokine regulation in response to Candida stimulation. Here, we present a new framework for the identification of susceptibility genes for infectious diseases that uses an unbiased, hypothesis-free, systems genetics approach. By applying this approach to candidaemia, we identified novel susceptibility genes and pathways for candidaemia, and future studies should assess their potential as therapeutic targets.

The Stearoyl-CoA Desaturase-1 (Desat1) in Drosophila cooperated with Myc to Induce Autophagy and Growth, a Potential New Link to Tumor Survival

Lipids are an important energy supply in our cells and can be stored or used to produce macromolecules during lipogenesis when cells experience nutrient starvation. Our proteomic analysis reveals that the Drosophila homologue of human Stearoyl-CoA desaturase-1 (Desat1) is an indirect target of Myc in fat cells. Stearoyl-CoA desaturases are key enzymes in the synthesis of monounsaturated fatty acids critical for the formation of complex lipids such as triglycerides and phospholipids. Their function is fundamental for cellular physiology, however in tumors, overexpression of SCD-1 and SCD-5 has been found frequently associated with a poor prognosis. Another gene that is often upregulated in tumors is the proto-oncogene c-myc, where its overexpression or increased protein stability, favor cellular growth. Here, we report a potential link between Myc and Desat1 to control autophagy and growth. Using Drosophila, we found that expression of Desat1, in metabolic tissues like the fat body, in the gut and in epithelial cells, is necessary for Myc function to induce autophagy a cell eating mechanism important for energy production. In addition, we observed that reduction of Desat1 affects Myc ability to induce growth in epithelial cells. Our data also identify, in prostatic tumor cells, a significant correlation between the expression of Myc and SCD-1 proteins, suggesting the existence of a potential functional relationship between the activities of these proteins in sustaining tumor progression.

Anti-tumor effect of emodin on gynecological cancer cells

PURPOSE

Although an anti-tumor effect of emodin has been reported before, its effect on human gynecological cancer cells has so far not been studied. Here, we assessed the effect of emodin on cervical cancer-derived (Hela), choriocarcinoma-derived (JAR) and ovarian cancer-derived (HO-8910) cells, and investigated the possible underlying molecular and cellular mechanisms.

METHODS AND RESULTS

The respective cells were treated with 0, 5, 10 or 15 μM emodin for 72 h. Subsequently, MTT and Transwell in vitro migration assays revealed that emodin significantly decreased the viability and invasive capacity of the gynecological cancer-derived cells tested. We found that emodin induced apoptosis and significantly decreased mitochondrial membrane potential and ATP release in these cells. We also found that emodin may exert its apoptotic effects via regulating the activity of caspase-9 and the expression of cleaved-caspase-3. Moreover, we found that emodin induced a cell cycle arrest at the G0/G1 phase, possibly through down-regulating the key cell cycle regulators Cyclin D and Cyclin E. Interestingly, emodin also led to autophagic cell death, as revealed by increased MAP LC3 expression, a marker of the autophagosome, and decreased expression of the autophagy regulators Beclin-1 and Atg12-Atg5. Finally, we found that the protein levels of both VEGF and VEGFR-2 were significantly decreased in emodin-treated cells, suggesting an anti-angiogenic effect of emodin on gynecological cancer-derived cells.

CONCLUSIONS

Our results suggest that emodin exhibits an anti-tumor effect on gynecological cancer-derived cells, possibly through multiple mechanisms including the induction of apoptosis and autophagy, the arrest of the cell cycle, and the inhibition of angiogenesis. Our findings may provide a basis for the design of potential emodin-based strategies for the treatment of gynecological tumors.

Cyclosporine A induces apoptotic and autophagic cell death in rat pituitary GH3 cells

Cyclosporine A (CsA) is a powerful immunosuppressive drug with side effects including the development of chronic nephrotoxicity. In this study, we investigated CsA treatment induced apoptotic and autophagic cell death in pituitary GH3 cells. CsA treatment (0.1 to 10 µM) decreased survival of GH3 cells in a dose-dependent manner. Cell viability decreased significantly with increasing CsA concentrations largely due to an increase in apoptosis, while cell death rates due to autophagy altered only slightly. Several molecular and morphological features correlated with cell death through these distinct pathways. At concentrations ranging from 1.0 to 10 µM, CsA induced a dose-dependent increase in expression of the autophagy markers LC3-I and LC3-II. Immunofluorescence staining revealed markedly increased levels of both LC3 and lysosomal-associated membrane protein 2 (Lamp2), indicating increases in autophagosomes. At the same CsA doses, apoptotic cell death was apparent as indicated by nuclear and DNA fragmentation and increased p53 expression. In apoptotic or autophagic cells, p-ERK levels were highest at 1.0 µM CsA compared to control or other doses. In contrast, Bax levels in both types of cell death were increased in a dose-dependent manner, while Bcl-2 levels showed dose-dependent augmentation in autophagy and were decreased in apoptosis. Manganese superoxide dismutase (Mn-SOD) showed a similar dose-dependent reduction in cells undergoing apoptosis, while levels of the intracellular calcium ion exchange maker calbindin-D9k were decreased in apoptosis (1.0 to 5 µM CsA), but unchanged in autophagy. In conclusion, these results suggest that CsA induction of apoptotic or autophagic cell death in rat pituitary GH3 cells depends on the relative expression of factors and correlates with Bcl-2 and Mn-SOD levels.

The importance of autophagy regulation in breast cancer development and treatment

Breast cancer (BC) is a potentially life-threatening malignant tumor that still causes high mortality among women. One of the mechanisms through which cancer development could be controlled is autophagy. This process exerts different effects during the stages of cancer initiation and progression due to the occurring superimposition of signaling pathways of autophagy and carcinogenesis. Chronic inhibition of autophagy or autophagy deficiency promotes cancer, due to instability of the genome and defective cell growth and as a result of cell stress. However, increased induction of autophagy can become a mechanism which allows tumor cells to survive the conditions of hypoxia, acidosis, or chemotherapy. Therefore, in the development of cancer, autophagy is regarded as a double-edged sword. Determination of the molecular mechanisms underlying autophagy regulation and its role in tumorigenesis is an essential component of modern anticancer strategies. Results of scientific studies show that inhibition of autophagy may enhance the effectiveness of currently used anticancer drugs and other therapies (like radiotherapy). However, in some cases, the promotion of autophagy can induce death and, hence, elimination of the cancer cells and reduction of tumor size. This review summarizes the current knowledge on autophagy regulation in BC and up-to-date anticancer strategies correlated with autophagy.

Aberrant autolysosomal regulation is linked to the induction of embryonic senescence: differential roles of Beclin 1 and p53 in vertebrate Spns1 deficiency

Spinster (Spin) in Drosophila or Spinster homolog 1 (Spns1) in vertebrates is a putative lysosomal H⁺-carbohydrate transporter, which functions at a late stage of autophagy. The Spin/Spns1 defect induces aberrant autolysosome formation that leads to embryonic senescence and accelerated aging symptoms, but little is known about the mechanisms leading to the pathogenesis in vivo. Beclin 1 and p53 are two pivotal tumor suppressors that are critically involved in the autophagic process and its regulation. Using zebrafish as a genetic model, we show that Beclin 1 suppression ameliorates Spns1 loss-mediated senescence as well as autophagic impairment, whereas unexpectedly p53 deficit exacerbates both of these characteristics. We demonstrate that ‘basal p53’ activity plays a certain protective role(s) against the Spns1 defect-induced senescence via suppressing autophagy, lysosomal biogenesis, and subsequent autolysosomal formation and maturation, and that p53 loss can counteract the effect of Beclin 1 suppression to rescue the Spns1 defect. By contrast, in response to DNA damage, ‘activated p53’ showed an apparent enhancement of the Spns1-deficient phenotype, by inducing both autophagy and apoptosis. Moreover, we found that a chemical and genetic blockage of lysosomal acidification and biogenesis mediated by the vacuolar-type H⁺-ATPase, as well as of subsequent autophagosome-lysosome fusion, prevents the appearance of the hallmarks caused by the Spns1 deficiency, irrespective of the basal p53 state. Thus, these results provide evidence that Spns1 operates during autophagy and senescence differentially with Beclin 1 and p53.

Spinster homolog 1 (Spns1) in vertebrates, as well as Spinster (Spin) in Drosophila, is a hypothetical lysosomal H⁺-carbohydrate transporter, which functions at a late stage of autophagy. The Spin/Spns1 defect induces aberrant autolysosome formation that leads to embryonic senescence and accelerated aging symptoms, while the molecular mechanisms of the pathogenesis are unknown in vivo. Using zebrafish, we show that Beclin 1 suppression ameliorates Spns1 loss-mediated senescence as well as autolysosomal impairment, whereas p53 deficit unexpectedly exacerbates these characteristics. We demonstrate that basal p53 activity has a certain protective role(s) against the Spns1 defect via suppressing autophagosome-lysosome fusion, while p53 activated by ultraviolet radiation amplifies the Spns1 deficit. In addition, we found that excessive lysosomal biogenesis and prolonged suboptimal acidification, modulated by v-ATPase, could be the primary reason for the appearance on the hallmarks of Spns1 deficiency. Our findings thus suggest that Spns1 is critically involved in lysosomal acidification and trafficking during autophagy, and differentially acts in a pathway with Beclin 1 and p53 in the regulation of senescence.

Genome-wide prediction and validation of peptides that bind human prosurvival Bcl-2 proteins

Programmed cell death is regulated by interactions between pro-apoptotic and prosurvival members of the Bcl-2 family. Pro-apoptotic family members contain a weakly conserved BH3 motif that can adopt an alpha-helical structure and bind to a groove on prosurvival partners Bcl-x_L, Bcl-w, Bcl-2, Mcl-1 and Bfl-1. Peptides corresponding to roughly 13 reported BH3 motifs have been verified to bind in this manner. Due to their short lengths and low sequence conservation, BH3 motifs are not detected using standard sequence-based bioinformatics approaches. Thus, it is possible that many additional proteins harbor BH3-like sequences that can mediate interactions with the Bcl-2 family. In this work, we used structure-based and data-based Bcl-2 interaction models to find new BH3-like peptides in the human proteome. We used peptide SPOT arrays to test candidate peptides for interaction with one or more of the prosurvival proteins Bcl-x_L, Bcl-w, Bcl-2, Mcl-1 and Bfl-1. For the 36 most promising array candidates, we quantified binding to all five human receptors using direct and competition binding assays in solution. All 36 peptides showed evidence of interaction with at least one prosurvival protein, and 22 peptides bound at least one prosurvival protein with a dissociation constant between 1 and 500 nM; many peptides had specificity profiles not previously observed. We also screened the full-length parent proteins of a subset of array-tested peptides for binding to Bcl-x_L and Mcl-1. Finally, we used the peptide binding data, in conjunction with previously reported interactions, to assess the affinity and specificity prediction performance of different models.

Bcl-2 family proteins regulate key cell death vs. survival decisions and are implicated in the development of many cancers. To understand the roles of Bcl-2 family proteins in both normal and diseased cells, it is important to map the interaction network of the family. Low sequence conservation in known Bcl-2 interaction motifs precludes easy identification of possible binding partners, but we developed computational models based on structure and experimental mutation data that show good predictive performance. We used our models to search the human proteome for new Bcl-2 interaction partners. We predicted and experimentally validated more than twice as many tight-binding peptides as were previously known.

Role of autophagy and its significance in cellular homeostasis

Autophagy is a catabolic pathway that regulates homeostasis in cells. It is an exceptional pathway of membrane trafficking. Autophagy is characterized by the formation of double-membrane vesicles; autophagosomes that are responsible for delivering damaged organelle and extra proteins to lysosome for recycling. A series of actions including environmental and genetic factors are responsible for induction of autophagy. In the past few decades, the research on autophagy has been immensely expanded because it is a vital process in maintaining cellular balance as well as deeply connected with pathogenesis of a number of diseases. The aim of this review is to present an overview of modern work on autophagy and highlight some essential genetic role in the induction of autophagy. There is an emerging need to identify, quantify, and manipulate the pathway of autophagy, due to its close relationship with a variety of developmental pathways and functions especially in cancer, diabetes, neurodegenerative disorders, and infectious diseases.

The role of cell signalling in the crosstalk between autophagy and apoptosis

Not surprisingly, the death of a cell is a complex and well controlled process. For several decades, apoptosis, the first genetically programmed death process to be identified has taken centre stage as the principal mechanism of programmed cell death (type I cell death) in mammalian tissues. Apoptosis has been extensively studied and its contribution to the pathogenesis of disease well documented. However, apoptosis does not function alone in determining the fate of a cell. More recently, autophagy, a process in which de novo formed membrane enclosed vesicles engulf and consume cellular components, has been shown to engage in complex interplay with apoptosis. As a result, cell death has been subdivided into the categories apoptosis (Type I), autophagic cell death (Type II), and necrosis (Type III). The boundary between Type I and II cell death is not completely clear and as we will discuss in this review and perhaps a discrete difference does not exist, due to intrinsic factors among different cell types and crosstalk among organelles within each cell type. Apoptosis may begin with autophagy and autophagy can often end with apoptosis, inhibition or a blockade of caspase activity may lead a cell to default into Type II cell death from Type I.

Exome sequencing revealed novel germline mutations in Chinese Peutz-Jeghers syndrome patients

BACKGROUND AND AIMS

Peutz-Jeghers Syndrome (PJS) is an autosomal dominant disorder which predisposes to the development of various cancers. Germline mutation in the serine/threonine kinase 11 gene (STK11) is known as one of the major causes of PJS. However, a notable proportion of PJS samples do not carry any mutation in STK11, suggesting possible genetic heterogeneity in the disease and the existence of other causative variants.

METHODS AND RESULTS

In order to identify other germline variants in the coding regions of the genome that are associated with PJS, we performed exome sequencing in three Chinese individuals with PJS and identified 16 common germline variants (12 protein-coding including STK11, 4 in pre-microRNAs). We further validated protein-coding variants in six PJS individuals (three with wild-type STK11) and predicted the functional impact. As result, we found that 7 coding variants are likely to have functional impacts. Especially, we identified 2 new germline variants which are represented in all six PJS samples and are independent of STK11 mutation.

CONCLUSIONS

Our study provided an exomic view of PJS. The germline variants identified in our analysis may help to resolve the complex genetic background of the disease and thus lead to the discovery of novel causative variants of PJS.

Comparative genomics of transport proteins in developmental bacteria: Myxococcus xanthus and Streptomyces coelicolor

Background

Two of the largest fully sequenced prokaryotic genomes are those of the actinobacterium, Streptomyces coelicolor (Sco), and the δ-proteobacterium, Myxococcus xanthus (Mxa), both differentiating, sporulating, antibiotic producing, soil microbes. Although the genomes of Sco and Mxa are the same size (~9 Mbp), Sco has 10% more genes that are on average 10% smaller than those in Mxa.

Results

Surprisingly, Sco has 93% more identifiable transport proteins than Mxa. This is because Sco has amplified several specific types of its transport protein genes, while Mxa has done so to a much lesser extent. Amplification is substrate- and family-specific. For example, Sco but not Mxa has amplified its voltage-gated ion channels but not its aquaporins and mechano-sensitive channels. Sco but not Mxa has also amplified drug efflux pumps of the DHA2 Family of the Major Facilitator Superfamily (MFS) (49 versus 6), amino acid transporters of the APC Family (17 versus 2), ABC-type sugar transport proteins (85 versus 6), and organic anion transporters of several families. Sco has not amplified most other types of transporters. Mxa has selectively amplified one family of macrolid exporters relative to Sco (16 versus 1), consistent with the observation that Mxa makes more macrolids than does Sco.

Conclusions

Except for electron transport carriers, there is a poor correlation between the types of transporters found in these two organisms, suggesting that their solutions to differentiative and metabolic needs evolved independently. A number of unexpected and surprising observations are presented, and predictions are made regarding the physiological functions of recognizable transporters as well as the existence of yet to be discovered transport systems in these two important model organisms and their relatives. The results provide insight into the evolutionary processes by which two dissimilar prokaryotes evolved complexity, particularly through selective chromosomal gene amplification.

Integrated genetic and epigenetic analysis of childhood acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) is the commonest childhood malignancy and is characterized by recurring structural genetic alterations. Previous studies of DNA methylation suggest epigenetic alterations may also be important, but an integrated genome-wide analysis of genetic and epigenetic alterations in ALL has not been performed. We analyzed 137 B-lineage and 30 T-lineage childhood ALL cases using microarray analysis of DNA copy number alterations and gene expression, and genome-wide cytosine methylation profiling using the HpaII tiny fragment enrichment by ligation-mediated PCR (HELP) assay. We found that the different genetic subtypes of ALL are characterized by distinct DNA methylation signatures that exhibit significant correlation with gene expression profiles. We also identified an epigenetic signature common to all cases, with correlation to gene expression in 65% of these genes, suggesting that a core set of epigenetically deregulated genes is central to the initiation or maintenance of lymphoid transformation. Finally, we identified aberrant methylation in multiple genes also targeted by recurring DNA copy number alterations in ALL, suggesting that these genes are inactivated far more frequently than suggested by structural genomic analyses alone. Together, these results demonstrate subtype- and disease-specific alterations in cytosine methylation in ALL that influence transcriptional activity, and are likely to exert a key role in leukemogenesis.

Cortical Auditory Deafferentation Induces Long-Term Plasticity in the Inferior Colliculus of Adult Rats: Microarray and qPCR Analysis

The cortico-collicular pathway is a bilateral excitatory projection from the cortex to the inferior colliculus (IC). It is asymmetric and predominantly ipsilateral. Using microarrays and RT-qPCR we analyzed changes in gene expression in the IC after unilateral lesions of the auditory cortex, comparing the ICs ipsi- and contralateral to the lesioned side. At 15 days after surgery there were mainly changes in gene expression in the IC ipsilateral to the lesion. Regulation primarily involved inflammatory cascade genes, suggesting a direct effect of degeneration rather than a neuronal plastic reorganization. Ninety days after the cortical lesion the ipsilateral IC showed a significant up-regulation of genes involved in apoptosis and axonal regeneration combined with a down-regulation of genes involved in neurotransmission, synaptic growth, and gap junction assembly. In contrast, the contralateral IC at 90 days post-lesion showed an up-regulation in genes primarily related to neurotransmission, cell proliferation, and synaptic growth. There was also a down-regulation in autophagy and neuroprotection genes. These findings suggest that the reorganization in the IC after descending pathway deafferentation is a long-term process involving extensive changes in gene expression regulation. Regulated genes are involved in many different neuronal functions, and the number and gene rearrangement profile seems to depend on the density of loss of the auditory cortical inputs.

Regulation of anti-apoptotic BCL2-proteins by non-canonical interactions: the next step forward or two steps back?

All aspects of cellular biology affect the process of regulated cell death, or apoptosis, and disruption of this process is a causative event in many diseases. Therefore, a comprehensive understanding of all pathways that regulate apoptosis would increase our knowledge of basic cellular functions, as well as the etiologies of many diseases. In turn, we may be able to use this knowledge to better treat patients with diseases, including cancer. Although the basic signaling pathway that regulates apoptosis has been known for over 10 years, we still have much to learn about the upstream signaling components that can directly regulate the core apoptosis machinery. The focus of this review will be to direct attention to non-canonical regulators of the BCL2-family of proteins, especially our void of understanding of such interactions, and the controversy that surrounds some such interactions.

Mapping a dynamic innate immunity protein interaction network regulating type I interferon production

To systematically investigate innate immune signaling networks regulating production of type I interferon, we analyzed protein complexes formed after microbial recognition. Fifty-eight baits were associated with 260 interacting proteins forming a human innate immunity interactome for type I interferon (HI5) of 401 unique interactions; 21% of interactions were modulated by RNA, DNA, or LPS. Overexpression and depletion analyses identified 22 unique genes that regulated NF-κB and ISRE reporter activity, viral replication, or virus-induced interferon production. Detailed mechanistic analysis defined a role for mind bomb (MIB) E3 ligases in K63-linked ubiquitination of TBK1, a kinase that phosphorylates IRF transcription factors controlling interferon production. Mib genes selectively controlled responses to cytosolic RNA. MIB deficiency reduced antiviral activity, establishing the role of MIB proteins as positive regulators of antiviral responses. The HI5 provides a dynamic physical and regulatory network that serves as a resource for mechanistic analysis of innate immune signaling.

Spinster is required for autophagic lysosome reformation and mTOR reactivation following starvation

Autophagy is a conserved cellular process to degrade and recycle cytoplasmic components. During autophagy, lysosomes fuse with an autophagosome to form an autolysosome. Sequestered components are degraded by lysosomal hydrolases and presumably released into the cytosol by lysosomal efflux permeases. Following starvation-induced autophagy, lysosome homeostasis is restored by autophagic lysosome reformation (ALR) requiring activation of the "target of rapamycin" (TOR) kinase. Spinster (Spin) encodes a putative lysosomal efflux permease with the hallmarks of a sugar transporter. Drosophila spin mutants accumulate lysosomal carbohydrates and enlarged lysosomes. Here we show that defects in spin lead to the accumulation of enlarged autolysosomes. We find that spin is essential for mTOR reactivation and lysosome reformation following prolonged starvation. Further, we demonstrate that the sugar transporter activity of Spin is essential for ALR.

Involvement of caspase-9 in autophagy-mediated cell survival pathway

Nonsteroidal anti-inflammatory drugs (NSAIDs) have been considered for use in the prevention and treatment of cancer malignancy. FR122047 (FR) is known to have an anti-inflammatory effect, but the anticancer activity of the chemical has not yet been identified. In the present study, we could find that treatment of breast cancer MCF-7 cells with FR led to apoptosis accompanying with apparent activation of caspases. Treatment of caspase-specific inhibitors revealed that FR-induced apoptosis was caspase-8-dependent and inhibition of caspase-9 activity resulted in unexpected, marked enhancement of cell death. Knockdown of caspase-9 expression by specific siRNA caused increased susceptibility to FR-induced cell death, consistent with the results obtained with treatment of caspase-9 inhibitor. Inhibition of caspase-9 blocked the autophagic process by modulating lysosomal pH and acid-dependent cathepsin activities and augmented cell death due to blockage of cytoprotective autophagy. MCF-7 cells treated with sulforaphane, an autophagy-inducing drug, also showed marked accumulation of LC3-II, and co-treatment with caspase-9 inhibitor brought about increased susceptibility to sulforaphane-induced cell death. Different from the cases with FR or sulforaphane, etoposide- or doxorubicin-induced cell death was suppressed with co-treatment of caspase-9 inhibitor, and the drugs failed to induce significant autophagy in MCF-7 cells. Taken together, our data originally suggest that inhibition of caspase-9 may block the autophagic flux and enhance cell death due to blockage of cytoprotective autophagy.

Phenotypic interactions of spinster with the genes encoding proteins for cell death control in Drosophila melanogaster

The spin gene was first identified by its mutant phenotype, which is characterized by extremely strong mate refusal by females in response to male courtship in Drosophila. Spin mutants are also known to be accompanied by a remarkable reduction in programmed cell death in the reproductive and nervous systems. To better understand the molecular functions of spin, we searched for its genetic modifiers. Forced expression of spin(+) in somatic cells as driven by ptc-Gal4 in the testis resulted in the invasion of mature sperm into the anterior testes tip, which is otherwise occupied only by immature germ cells. To obtain genes that modulate spin's effect, the gain-of-function spin phenotype was observed in the presence of a chromosome harboring an EP or GS P-element insertion, which initiates transcription of the genomic sequence neighboring the insertion site. We isolated th and emc as suppressors of spin and atg8a as a gene that reproduces the spin phenotype on its own. th encodes Inhibitor of apoptosis-1, and mammalian Id genes homologous to emc are known to inhibit apoptosis. atg8a encodes a protein essential for autophagy. These results suggest that spin promotes cell death mechanisms that are regulated negatively by th and emc and positively by atg8a.

Brk protects breast cancer cells from autophagic cell death induced by loss of anchorage

Brk, a tyrosine kinase expressed in a majority of breast tumors, but not normal mammary tissue, promotes breast carcinoma cell proliferation. Normal epithelial cells are dependent on cell-cell or cell-matrix interactions for survival and undergo apoptosis after disruption of these interactions. Tumor cells are less sensitive to the induction of apoptosis and are predicted to have the potential to disseminate. We investigated whether Brk has further roles in breast tumor progression by relating its expression to tumor grade and demonstrating its role in the regulation of carcinoma cell survival under non-adherent conditions. Brk expression was determined by reverse transcription PCR on RNA extracted from surgical samples of human breast cancers. Breast carcinoma cell survival in suspension culture was examined when Brk protein levels were suppressed by RNA interference. Additionally, the effect of experimentally overexpressing Brk in otherwise Brk-negative breast carcinoma cells was assessed. Brk mRNA expression was notably higher in grade 3 breast tumors, as compared with lower tumor grades. In suspension culture, Brk suppression increased the rate of cell death, as compared with controls, and this cell death program exhibited characteristics of autophagy but not of apoptosis. Conversely, experimental expression of Brk in Brk-negative cells increased cell survival whereas kinase-inactive Brk did not. Therefore, Brk enhances breast carcinoma cell survival in suspension, suggesting a role for Brk in supporting breast cancer cell dissemination.

MUC1 oncoprotein promotes autophagy in a survival response to glucose deprivation

Tumor cells survive under conditions of nutrient deprivation by mechanisms that are not fully understood. The MUC1 oncoprotein is aberrantly overexpressed by most human carcinomas and blocks oxidative stress-induced death. The present studies show that MUC1 inhibits the induction of necrosis in response to the deprivation of glucose. MUC1 suppressed glucose deprivation-induced increases in reactive oxygen species (ROS) and thereby depletion of ATP and cell death. Cells respond to oxidative stress and energy depletion with the induction of autophagy. Our results demonstrate that MUC1 blocks depletion of ATP and sustains growth of glucose-deprived cells by a mechanism sensitive to the autophagy inhibitor, 3-methyladenine. Silencing expression of ATG7, a protein essential for the formation of autophagic vacuoles, also attenuated the MUC1-sustained increases in ATP and growth in response to glucose deprivation. Moreover, we found that MUC1 stimulates AMPK activation and thereby promotes lysosomal turnover of LC3-II, a marker of starvation-induced autophagic activity. These results indicate that MUC1 suppresses glucose deprivation-induced increases in ROS and thereby promotes ATP production and survival. The findings also indicate that the overexpression of MUC1 as found in human cancers could provide a survival advantage in microenvironments with low glucose levels.

Ischemic conditioning by short periods of reperfusion attenuates renal ischemia/reperfusion induced apoptosis and autophagy in the rat

Prolonged ischemia amplified iscehemia/reperfusion (IR) induced renal apoptosis and autophagy. We hypothesize that ischemic conditioning (IC) by a briefly intermittent reperfusion during a prolonged ischemic phase may ameliorate IR induced renal dysfunction. We evaluated the antioxidant/oxidant mechanism, autophagy and apoptosis in the uninephrectomized Wistar rats subjected to sham control, 4 stages of 15-min IC (I15 x 4), 2 stages of 30-min IC (I30 x 2), and total 60-min ischema (I60) in the kidney followed by 4 or 24 hours of reperfusion. By use of ATP assay, monitoring O2-. amounts, autophagy and apoptosis analysis of rat kidneys, I60 followed by 4 hours of reperfusion decreased renal ATP and enhanced reactive oxygen species (ROS) level and proapoptotic and autophagic mechanisms, including enhanced Bax/Bcl-2 ratio, cytochrome C release, active caspase 3, poly-(ADP-ribose)-polymerase (PARP) degradation fragments, microtubule-associated protein light chain 3 (LC3) and Beclin-1 expression and subsequently tubular apoptosis and autophagy associated with elevated blood urea nitrogen and creatinine level. I30 x 2, not I15 x 4 decreased ROS production and cytochrome C release, increased Manganese superoxide dismutase (MnSOD), Copper-Zn superoxide dismutase (CuZnSOD) and catalase expression and provided a more efficient protection than I60 against IR induced tubular apoptosis and autophagy and blood urea nitrogen and creatinine level. We conclude that 60-min renal ischemia enhanced renal tubular oxidative stress, proapoptosis and autophagy in the rat kidneys. Two stages of 30-min ischemia with 3-min reperfusion significantly preserved renal ATP content, increased antioxidant defense mechanisms and decreased ischemia/reperfusion enhanced renal tubular oxidative stress, cytosolic cytochrome C release, proapoptosis and autophagy in rat kidneys.

The Drosophila BEACH family protein, blue cheese, links lysosomal axon transport with motor neuron degeneration

Impaired axon transport is one of the earliest pathological manifestations of several neurodegenerative diseases, and mutations in motor proteins can exacerbate or cause degeneration (Williamson and Cleveland, 1999; Gunawardena and Goldstein, 2004; Stokin and Goldstein, 2006). Compromised function in lysosomes and other degradative organelles that intersect with the lysosomal pathway are also strongly implicated in neurodegenerative disease pathology (Nixon and Cataldo, 2006; Rubinsztein, 2006). However, any functional link between these two phenomena has not as yet been recognized. Drosophila mutants in blue cheese (bchs) undergo progressive brain degeneration as adults and have shortened life span (Finley et al., 2003), but the cellular function of Bchs and the cause of degeneration have not been identified. A role in lysosomal trafficking is suggested by the homology of Bchs with the vesicle trafficking-associated BEACH (Beige and Chediak-Higashi) domain protein family (Wang et al., 2002; De Lozanne, 2003) and by its genetic interaction with a lysosomal transport pathway (Simonsen et al., 2007). Here, we describe the degeneration of a population of identified larval motor neurons in bchs mutants. We present evidence that Bchs is primarily lysosomal in those motor neurons in wild type and, using live fluorescence imaging of individual motor neurons in intact larvae, show that lysosomal vesicles fail to be transported toward motor neuron termini in bchs mutant and Bchs-overexpressing larvae. We suggest therefore that anterograde transport of lysosomes toward synaptic termini is a key factor in preventing motor neuron degeneration and that Bchs reveals a functional link between the lysosomal degradative pathway and transport.

BNIP3 subfamily BH3-only proteins: mitochondrial stress sensors in normal and pathological functions

The BNIP3 subfamily of BH3-only proteins consists of BNIP3 and BNIP3-like (BNIP3L) proteins. These proteins form stable homodimerization complexes that localize to the outer membrane of the mitochondria after cellular stress. This promotes either apoptotic or non-apoptotic cell death such as autophagic cell death. Although the mammalian cells contain both members of this subfamily, the genome of Caenorhabditis elegans codes for a single BNIP3 ortholog, ceBNIP3, which shares homology in the transmembrane (TM) domain and in a conserved region close to the BH3 domain of mammalian BNIP3 protein. The cell death activities of BNIP3 and BNIP3L are determined by either the BH3 domain or the C-terminal TM domain. The TM domain of BNIP3 is unique, as it is capable of autonomous stable dimerization and contributes to mitochondrial localization of BNIP3. In knockout mouse models, BNIP3L was shown to be essential for normal erythrocyte differentiation and hematopoietic homeostasis, whereas BNIP3 plays a role in cellular responses to ischemia/reperfusion injury in the heart. Both BNIP3 and BNIP3L play a role in cellular responses to stress. Under hypoxia, both BNIP3 and BNIP3L expression levels are elevated and contribute to hypoxia-induced cell death. In addition, these proteins play critical roles in disease states. In heart disease, both BNIP3 and BNIP3L play a critical role in cardiomyocyte cell death following ischemic and non-ischemic injuries. In cancer, expression of BNIP3 and BNIP3L is downregulated by promoter hypermethylation or by homozygous deletion of the gene locus in certain cancers, whereas their expression was increased in other cancers. In addition, BNIP3 expression has been correlated with poor prognosis in some cancers. The results reviewed here suggest that BNIP3 and BNIP3L may be novel therapeutic targets for intervention because of their pathological roles in regulating cell death in disease states.

Crosstalk between autophagy and apoptosis in heart disease

Autophagy is a cell survival mechanism that involves degradation and recycling of cytoplasmic components, such as long-lived proteins and organelles. In addition, autophagy mediates cell death under specific circumstances. Apoptosis, a form of programmed cell death, has been well characterized, and the molecular events involved in apoptotic death are well understood. Damaged cardiomyocytes that show characteristics of autophagy have been observed during heart failure. However, it remains unclear whether autophagy is a sign of failed cardiomyocyte repair or is a suicide pathway for the failing cardiomyocytes. Although autophagy and apoptosis are markedly different processes, several pathways regulate both autophagic and apoptotic machinery and autophagy can cooperate with apoptosis. This review summarizes the evidence for crosstalk between autophagy and apoptosis.

Cell death in heart failure

Heart failure (HF) has become the dominant cardiovascular disorder in the Western world and Japan, so there is an urgent need to clarify the mechanisms governing pathological remodeling mediated through cell death, and to identify ways of preventing and treating HF. Historically, there are 3 types of cell death: apoptosis, autophagy and necrosis. Apoptosis, a form of programmed cell death, has been well characterized and the molecular events involved in apoptotic death are well understood. Necrosis is often defined in a negative manner: death lacking the characteristics of programmed cell death and thus accidental and uncontrolled. However, recent studies indicate that necrosis is tightly regulated. Autophagy is a cell survival mechanism that involves degradation and recycling of cytoplasmic components. In contrast to the other 2 mechanisms, autophagy may mediate cell death under specific circumstances. In fact, damaged cardiomyocytes that show characteristics of autophagy have been observed during HF. However, a recent study indicated that upregulation of autophagy in the failing heart is an adaptive response. This review summarizes recent findings regarding the molecular mechanisms of cardiomyocyte cell death in HF.

ER-stress caused by accumulated intracistanal granules activates autophagy through a different signal pathway from unfolded protein response in exocrine pancreas cells of rats exposed to fluoride

In rat exocrine pancreas cells, fluoride treatment causes autophagy resulting from intracisternal granule accumulation. Excessive autophagy might promote a type of programmed cell death different from apoptosis. To clarify how fluoride-induced autophagy and subsequent cell death occurs, we investigated morphological and biochemical changes in exocrine pancreas cells of rats subcutaneously injected with NaF saline solution at 20 mg/kg dose twice daily for 4 days. Intracisternal granule, excessive autophagy and ribosomal degranulation were observed in fluoride-exposed cells, occasionally with necrotic changes. Fluoride-induced rER-stress increased eIF-2alpha phosphorylation and CHOP expression, but did not affect GRP78. Spliced XBP-1 expression was decreased in damaged cells. These findings indicate that rER-stress by intracisternal granule accumulation lead to autophagy in exocrine pancreas cells without UPR, suggesting that signal process of autophagy differs from that of UPR-apoptosis. It is likely that intense degranulation is a turning point that damaged cells change over from autophagy, cell-protective process, to cell-death process.

BH3-only protein BIK induces caspase-independent cell death with autophagic features in Bcl-2 null cells

The BH3-only protein BIK normally induces apoptotic cell death. Here, we have investigated the role of BCL-2 in BIK-induced cell death using Bcl-2+/+ and Bcl-2-/- mouse embryo fibroblasts. Ectopic expression of BIK in Bcl-2-/- cells resulted in enhanced cell death compared to Bcl-2+/+ cells. In these cells, while caspase-8 was activated, there was no significant activation of caspase-9 and 3. There was no detectable mitochondrial to cytosolic release of cytochrome-c. However, there was significant redistribution of AIF from mitochondria to the nucleus. The extent of BIK-induced cell death was augmented by treatment with the pancaspase inhibitor, zVAD-fmk. The Bcl-2 null cells expressing BIK exhibited autophagic features such as cytosolic vacuoles, punctate distribution of LC3 and enhanced expression of Beclin-1. The survival of BIK-expressing Bcl-2-/- cells was enhanced in the presence of PI3 kinase inhibitors 3-methyladenine and Wortmannin and also by depletion of Atg5 and Beclin-1. Death of BIK-expressing Bcl-2-/- cells treated with zVAD-fmk was increased under caspase-8 depletion. Our results suggest enhanced expression of BIK in the Bcl-2 deficient cells leads to cell death with autophagic features and the extent of such cell death could be increased by inhibition of caspases.

Bcl-xL augmentation potentially reduces ischemia/reperfusion induced proximal and distal tubular apoptosis and autophagy

BACKGROUND

Apoptosis and autophagy may contribute to cell homeostasis in the kidney subjected to ischemia/reperfusion injury via mitochondrial injury. Ischemia/reperfusion induces differential sensitivity between proximal and distal tubules via a dissociated Bcl-xL expression. We hypothesized Bcl-xL augmentation in the proximal and distal tubules may potentially reduce ischemia/reperfusion induced renal dysfunction.

METHODS

We augmented Bcl-xL protein expression in the kidney with intrarenal adenoviral bcl-xL gene transfer and evaluated the potential effect of Bcl-xL augmentation on ischemia/reperfusion induced renal oxidative stress, apoptosis, and autophagy in the rat.

RESULTS

Intrarenal arterial Adv-bcl-xL administration augmented maximal Bcl-xL protein expression of rat kidney after 7 days of transfection. The primary location of Bcl-xL augmentation was found in proximal and distal tubules, but not in glomeruli. Ischemia/reperfusion increased mitochondrial cytochrome C release, renal O2(-*) level and renal 3-nitrosine and 4-hydroxyneonal accumulation, potentiated tubular apoptosis and autophagy, including increase in microtubule-associated protein 1 light chain 3 (LC-3) and Beclin-1 expression, Bax/Bcl-xL ratio, caspase 3 expression and poly-(ADP-ribose)-polymerase fragments, and subsequent proximal and distal tubular apoptosis/autophagy. However, Adv-bcl-xL administration significantly reduced ischemia/reperfusion enhanced mitochondrial cytochrome C release, O2(-*) production, 3-nitrotyrosine and 4-hydroxynonenal accumulation, Beclin-1 expression, Bax/Bcl-xL ratio, and proximal and distal tubular apoptosis/autophagy, consequently improving renal dysfunction. Further study showed that Bcl-xL augmentation was more efficiently than Bcl-2 augmentation in amelioration of ischemia/reperfusion induced proximal and distal tubular apoptosis and renal dysfunction.

CONCLUSIONS

Our results suggest that Adv-bcl-xL gene transfer significantly improves ischemia/reperfusion-induced renal dysfunction via the downregulation of renal tubular apoptosis and autophagy.

Self-eating and self-killing: crosstalk between autophagy and apoptosis

The functional relationship between apoptosis ('self-killing') and autophagy ('self-eating') is complex in the sense that, under certain circumstances, autophagy constitutes a stress adaptation that avoids cell death (and suppresses apoptosis), whereas in other cellular settings, it constitutes an alternative cell-death pathway. Autophagy and apoptosis may be triggered by common upstream signals, and sometimes this results in combined autophagy and apoptosis; in other instances, the cell switches between the two responses in a mutually exclusive manner. On a molecular level, this means that the apoptotic and autophagic response machineries share common pathways that either link or polarize the cellular responses.

The Drosophila caspases Strica and Dronc function redundantly in programmed cell death during oogenesis

Programmed cell death (PCD) in the Drosophila ovary occurs either during mid-oogenesis, resulting in degeneration of the entire egg chamber or during late oogenesis, to facilitate the development of the oocyte. PCD during oogenesis is regulated by mechanisms different from those that control cell death in other Drosophila tissues. We have analyzed the role of caspases in PCD of the female germline by examining caspase mutants and overexpressing caspase inhibitors. Imprecise P-element excision was used to generate mutants of the initiator caspase strica. While null mutants of strica or another initiator caspase, dronc, display no ovary phenotype, we find that strica exhibits redundancy with dronc, during both mid- and late oogenesis. Ovaries of double mutants contain defective mid-stage egg chambers similar to those reported previously in dcp-1 mutants, and mature egg chambers with persisting nurse cell nuclei. In addition, the effector caspases drice and dcp-1 also display redundant functions during late oogenesis, resulting in persisting nurse cell nuclei. These findings indicate that caspases are required for nurse cell death during mid-oogenesis, and participate in developmental nurse cell death during late oogenesis. This reveals a novel pathway of cell death in the ovary that utilizes strica, dronc, dcp-1 and drice, and importantly illustrates strong redundancy among the caspases.

Autophagic and apoptotic response to stress signals in mammalian cells

Autophagy is a highly conserved catabolic programme for degrading proteins and organelles. This process has been shown to act as a pro-survival or pro-death mechanism in different physiological and pathological conditions. Several stress stimuli can induce autophagy, such as nutrient deprivation or critical steps in development of lower and higher eukaryotes. Apoptosis is an orchestrated form of cell death in which cells are actively involved in their own demise. Again, stress is a positive regulator of apoptosis and, in particular, of its apoptosome-mediated mitochondrial pathway. Besides discussing the individual roles played by the key molecules involved in autophagy in mammals in response to stress signals, we discuss here the interrelations between autophagy and apoptosis under these conditions.

Autophagy and NF-kappaB: fight for fate

Autophagy/macroautophagy is known for its role in cellular homeostasis, development, cell survival, aging, immunity, cancer and neurodegeneration. However, until recently, the mechanisms by which autophagy contributes to these important processes were largely unknown. The demonstration of a direct cross-talk between autophagy and NF-kappaB opens up new frontiers for deciphering the role of autophagy in diverse biological processes. Here, we review our current understanding of autophagy, with a focus on its role in tumor suppression, NF-kappaB inactivation and selective protein degradation in mammals. We also list some most intriguing and outstanding questions that are likely to engage researchers in the near future.

Genetic modifiers of the Drosophila blue cheese gene link defects in lysosomal transport with decreased life span and altered ubiquitinated-protein profiles

Defects in lysosomal trafficking pathways lead to decreased cell viability and are associated with progressive disorders in humans. Previously we have found that loss-of-function (LOF) mutations in the Drosophila gene blue cheese (bchs) lead to reduced adult life span, increased neuronal death, and widespread CNS degeneration that is associated with the formation of ubiquitinated-protein aggregates. To identify potential genes that participate in the bchs functional pathway, we conducted a genetic modifier screen based on alterations of an eye phenotype that arises from high-level overexpression of Bchs. We found that mutations in select autophagic and endocytic trafficking genes, defects in cytoskeletal and motor proteins, as well as mutations in the SUMO and ubiquitin signaling pathways behave as modifiers of the Bchs gain-of-function (GOF) eye phenotype. Individual mutant alleles that produced viable adults were further examined for bchs-like phenotypes. Mutations in several lysosomal trafficking genes resulted in significantly decreased adult life spans and several mutants showed changes in ubiquitinated protein profiles as young adults. This work represents a novel approach to examine the role that lysosomal transport and function have on adult viability. The genes characterized in this study have direct human homologs, suggesting that similar defects in lysosomal transport may play a role in human health and age-related processes.