Autophagy and Apoptosis Coordinate Physiological Cell Death in Larval Salivary Glands of Apis mellifera (Hymenoptera: Apidae)

Larval salivary glands of bees provide a good model for the study of hormone-induced programmed cell death in Hymenoptera because they have a well-defined secretory cycle with a peak of secretory activity phase, prior to cocoon spinning, and a degenerative phase, after the cocoon spinning. Our findings demonstrate that there is a relationship between apoptosis and autophagy during physiological cell death in these larval salivary glands, that adds evidence to the hypothesis of overlap in the regulation pathways of both types of programmed cell death. Features of authophagy include cytoplasm vacuolation, acid phosphatase activity, presence of autophagic vacuoles and multi-lamellar structures, as well as a delay in the collapse of many nuclei. Features of apoptosis include bleb formation in the cytoplasm and nuclei, with release of parts of the cytoplasm into the lumen, chromatin compaction, and DNA and nucleolar fragmentation. We propose a model for programmed cell death in larval salivary glands of Apis mellifera where autophagy and apoptosis function cooperatively for a more efficient degeneration of the gland secretory cells.

Addendum to:

Programmed Cell Death in the Larval Salivary Glands of Apis mellifera (Hymenoptera, Apidae)

E.C.M. Silva-Zacarin, G.A. Tomaino, M.R. Brochetto-Braga, S.R. Taboga, R.L.M. Silva de Moraes

J Biosci 2007; 32:309-28     

Psidium guajava L. anti-neoplastic effects: induction of apoptosis and cell differentiation

Objectives: Curative properties of medicinal plants such as Psidium guajava L. (Myrtaceae) have often been indicated by epidemiological studies on populations in which these fruits are consumed daily. However, complete characterization of the active principles responsible for this ability has never been performed. Here, we have characterized P. guajava’s anti‐cancer potential and identified the parts of the fruit involved in its anti‐neoplastic action. Materials and methods: We studied morphology of our cells, cell cycle characteristics and apoptosis and performed immunostaining, differentiation and western blot analyses. Results: We report that the P. guajava extract exerted anti‐cancer control on both haematological and solid neoplasias. P. guajava extract’s anti‐tumour properties were found to be tightly bound to induction of apoptosis and differentiation. Use of ex vivo myeloid leukaemia blasts corroborated that P. guajava was able to induce cell death but did not exhibit anti‐cancer effects on all malignant cells investigated, indicating selective activity against certain types of tumour. Analyses of P. guajava pulp, peel and seeds identified the pulp as being the most relevant component for causing cell cycle arrest and apoptosis, whereas peel was responsible for causing cell differentiation. P. guajava itself and its pulp‐derived extract were found to induce apoptosis accompanied by caspase activation and p16, p21, Fas ligand (FASL TNF super‐family, member 6), Bcl‐2‐associated agonist of cell death (BAD) and tumour necrosis factor receptor super‐family, member 10b (DR5), overexpression. Conclusions: Our findings showed that P. guajava L. extract was able to exert anti‐cancer activity on cultures in vitro and ex vivo, supporting the hypothesis of its anti malignant pro‐apoptotic modulation.     

Modulation of programmed cell death by medicinal plants.

Programmed cell death (apoptosis), a form of cell death, described by Kerr and Wyllie some 20 years ago, has generated considerable interest in recent years. The mechanisms by which this mode of cell death (seen both in animal and plant cells), takes place have been examined in detail. Extracellular signals and intracellular events have been elaborated. Of interest to the clinician, is the concentrated effort to study pharmacological modulation of programmed cell death. The attempt to influence the natural phenomenon of programmed cell death stems from the fact that it is reduced (like in cancer) or increased (like in neurodegenerative diseases) in several clinical situations. Thus, chemicals that can modify programmed cell death are likely to be potentially useful drugs. From foxglove, which gave digitalis to the Pacific Yew from which came taxol, plants have been a source of research material for useful drugs. Recently, a variety of plant extracts have been investigated for their ability to influence the apoptotic process. This article discusses some of the interesting data. The ability of plants to influence programmed cell death in cancerous cells in an attempt to arrest their proliferation has been the topic of much research. Various cell-lines like HL60, human hepatocellular carcinoma cell line (KIM-1), a cholangiocarcinoma cell-line (KMC-1), B-cell hybridomas, U937 a monocytic cell-line, HeLa cells, human lymphoid leukemia (MOLT-4B) cells and K562 cells have been studied. The agents found to induce programmed cell death (measured either morphologically or flow cytometrically) included extracts of plants like mistletoe and Semicarpus anacardium. Isolated compounds like bryonolic acid (from Trichosanthes kirilowii var. Japonica, crocin (from saffron) and allicin (from Allium sativum) have also been found to induce programmed cell death and therefore arrest proliferation. Even Chinese herbal medicine "Sho-saiko-to" induces programmed cell death in selected cancerous cell lines. Of considerable interest is the finding that Panax ginseng prevents irradiation-induced programmed cell death in hair follicles, suggesting important therapeutic implications. Nutraceuticals (dietary plants) like soya bean, garlic, ginger, green tea, etc. which have been suggested, in epidemiological studies, to reduce the incidence of cancer may do so by inducing programmed cell death. Soy bean extracts have been shown to prevent development of diseases like polycystic kidneys, while Artemisia asiatica attenuates cerulein-induced pancreatitis in rats. Interestingly enough, a number of food items as well as herbal medicines have been reported to produce toxic effects by inducing programmed cell death. For example, programmed cell death in isolated rat hepatocytes has been implicated in the hepatitis induced by a herbal medicine containing diterpinoids from germander. Other studies suggest that rapid progression of the betel- and tobacco-related oral squamous cell carcinomas may be associated with a simultaneous involvement of p53 and c-myc leading to inhibition of programmed cell death. Several mechanisms have been identified to underlie the modulation of programmed cell death by plants including endonuclease activation, induction of p53, activation of caspase 3 protease via a Bcl-2-insensitive pathway, potentiate free-radical formation and accumulation of sphinganine. Programmed cell death is a highly conserved mechanism of self-defense, also found to occur in plants. Hence, it is natural to assume that chemicals must exist in them to regulate programmed cell death in them. Thus, plants are likely to prove to be important sources of agents that will modulate programmed cell death.     

Deoxyelephantopin from Elephantopus scaber L. induces cell-cycle arrest and apoptosis in the human nasopharyngeal cancer CNE cells

Deoxyelephantopin (ESD), a naturally occurring sesquiterpene lactone present in the Chinese medicinal herb, Elephantopus scaber L. exerted anticancer effects on various cultured cancer cells. However, the cellular mechanisms by which it controls the development of the cancer cells are unavailable, particularly the human nasopharyngeal cancer CNE cells. In this study, we found that ESD inhibited the CNE cell proliferation. Cell cycle arrest in S and G2/M phases was also found. Western blotting analysis showed that modulation of cell cycle regulatory proteins was responsible for the ESD-induced cell cycle arrest. Besides, ESD also triggered apoptosis in CNE cells. Dysfunction in mitochondria was found to be associated with the ESD-induced apoptosis as evidenced by the loss of mitochondrial membrane potential (ΔΨm), the translocation of cytochrome c, and the regulation of Bcl-2 family proteins. Despite the Western blotting analysis showed that both intrinsic and extrinsic apoptotic pathways (cleavage of caspases-3, -7, -8, -9, and -10) were triggered in the ESD-induced apoptosis, additional analysis also showed that the induction of apoptosis could be achieved by the caspase-independent manner. Besides, Akt, ERK and JNK pathways were found to involve in ESD-induced cell death. Overall, our findings provided the first evidence that ESD induced cell cycle arrest, and apoptosis in CNE cells. ESD could be a potential chemotherapeutic agent in the treatment of nasopharyngeal cancer (NPC).     

Chemical-induced apoptotic cell death in tomato cells: involvement of caspase-like proteases

 A new system to study programmed cell death in plants is described. Tomato (Lycopersicon esculentum Mill.) suspension cells were induced to undergo programmed cell death by treatment with known inducers of apoptosis in mammalian cells. This chemical-induced cell death was accompanied by the characteristic features of apoptosis in animal cells, such as typical changes in nuclear morphology, the fragmentation of the nucleus and DNA fragmentation. In search of processes involved in plant apoptotic cell death, specific enzyme inhibitors were tested for cell-death-inhibiting activity. Our results showed that proteolysis plays a crucial role in apoptosis in plants. Furthermore, caspase-specific peptide inhibitors were found to be potent inhibitors of the chemical-induced cell death in tomato cells, indicating that, as in animal systems, caspase-like proteases are involved in the apoptotic cell death pathway in plants. Received: 5 August 1999 / Accepted: 14 March 2000     

10H‐3,6‐Diazaphenothiazines triggered the mitochondrial‐dependent and cell death receptor‐dependent apoptosis pathways and further increased the chemosensitivity of MCF‐7 breast cancer cells via inhibition of AKT1 pathways

Breast cancer is one of the leading causes of death in cancer categories, followed by lung, colorectal, and ovarian among the female gender across the world. 10H‐3,6‐diazaphenothiazine (PTZ) is a thiazine derivative compound that exhibits many pharmacological activities. Herein, we proceed to investigate the pharmacological activities of PTZ toward breast cancer MCF‐7 cells as a representative in vitro breast cancer cell model. The PTZ exhibited a proliferation inhibition (IC₅₀ = 0.895 µM) toward MCF‐7 cells. Further, cell cycle analysis illustrated that the S‐phase checkpoint was activated to achieve proliferation inhibition. In vitro cytotoxicity test on three normal cell lines (HEK293 normal kidney cells, MCF‐10A normal breast cells, and H9C2 normal heart cells) demonstrated that PTZ was more potent toward cancer cells. Increase in the levels of reactive oxygen species results in polarization of mitochondrial membrane potential (ΔΨm), together with suppression of mitochondrial thioredoxin reductase enzymatic activity suggested that PTZ induced oxidative damages toward mitochondria and contributed to improved drug efficacy toward treatment. The RT² PCR Profiler Array (human apoptosis pathways) proved that PTZ induced cell death via mitochondria‐dependent and cell death receptor‐dependent pathways, through a series of modulation of caspases, and the respective morphology of apoptosis was observed. Mechanistic studies of apoptosis suggested that PTZ inhibited AKT1 pathways resulting in enhanced drug efficacy despite it preventing invasion of cancer cells. These results showed the effectiveness of PTZ in initiation of apoptosis, programmed cell death, toward highly chemoresistant MCF‐7 cells, thus suggesting its potential as a chemotherapeutic drug.     

Fusicoccin induces in plant cells a programmed cell death showing apoptotic features

Summary. Programmed cell death plays a pivotal role in several developmental processes of plants and it is involved in the response to environmental stresses and in the defense mechanisms against pathogen attack. It has not yet been defined which part of the death signalling mechanism and which molecules involved in programmed cell death are common to animals and plants. In this paper we show that fusicoccin, a well-known phytotoxin, induces a strong acceleration in the appearance of Evans Blue-stainable (dead) cells in sycamore (Acer pseudoplatanus L.) cultures. This fusicoccin-induced cell death shows aspects common to the form of animal programmed cell death termed apoptosis: i.e., cell shrinkage, changes in nucleus morphology, increase in DNA fragmentation detectable by a specific immunological reaction, and presence of oligonucleosomal-size fragments (laddering) in DNA gel electrophoresis. Since fusicoccin has a well-identified molecular target, the plasma membrane H⁺-ATPase, and thoroughly investigated physiological effects, this toxin appears to be a useful tool to study the transduction of death signals leading to programmed cell death in plants.Correspondence and reprints: Dipartimento di Biotecnologie e Bioscienze, Universitä degli Studi di Milano-Bicocca, Piazza della Scienza 2, 20126 Milano, Italy.     

The role of Eag and HERG channels in cell proliferation and apoptotic cell death in SK-OV-3 ovarian cancer cell line

Background  

The voltage gated potassium (K⁺) channels Eag and HERG have been implicated in the pathogenesis of various cancers, through association with cell cycle changes and programmed cell death. The role of these channels in the onset and progression of ovarian cancer is unknown. An understanding of mechanism by which Eag and HERG channels affect cell proliferation in ovarian cancer cells is required and therefore we investigated their role in cell proliferation and their effect on the cell cycle and apoptosis of ovarian cancer cells.     

Apoptosis and Autophagy Function Cooperatively for the Efficacious Execution of Programmed Nurse Cell Death During Drosophila virilis Oogenesis

Programmed cell death consists of two major types, apoptotic and autophagic, both of which are mainly defined by morphological criteria. Our findings indicate that both types of programmed cell death occur in the ovarian nurse cells during middle and late oogenesis of Drosophila virilis. During mid-oogenesis, the spontaneously degenerated egg chambers exhibit typical characteristics of apoptotic cell death. Their nurse cells contain condensed chromatin and fragmented DNA, whereas active caspase assays and immunostaining procedures demonstrate the presence of highly activated caspases. Distinct features of autophagic cell death are also observed during D. virilis mid-oogenesis, as shown by monodansylcadaverine staining and ultrastructural examination performed by transmission electron microscopy. Additionally, atretic egg chambers exhibit an accumulation of lysosomal proteases. At the late stages of D. virilis oogenesis, apoptosis and autophagy coexist, manifesting cell death features that are similar to the ones described above, being also escorted by the involvement of an altered cytochrome c conformational display. We propose that apoptosis and autophagy operate synergistically during D. virilis oogenesis for a more efficient elimination of the degenerated nurse cells.

Addendum to:

Mechanisms of Programmed Cell Death During Oogenesis in Drosophila virilis

A.D. Velentzas, I.P. Nezis, D.J. Stravopodis, I.S. Papassideri and L.H. Margaritis

Cell Tissue Res 2006; doi: 10.1007/s00441-006-0298-x     

Autophagy provides a conceptual therapeutic framework for bone metastasis from prostate cancer

Prostate cancer is a common malignant tumor, which can spread to multiple organs in the body. Metastatic disease is the dominant reason of death for patients with prostate cancer. Prostate cancer usually transfers to bone. Bone metastases are related to pathologic fracture, pain, and reduced survival. There are many known targets for prostate cancer treatment, including androgen receptor (AR) axis, but drug resistance and metastasis eventually develop in advanced disease, suggesting the necessity to better understand the resistance mechanisms and consider multi-target medical treatment. Because of the limitations of approved treatments, further research into other potential targets is necessary. Metastasis is an important marker of cancer development, involving numerous factors, such as AKT, EMT, ECM, tumor angiogenesis, the development of inflammatory tumor microenvironment, and defect in programmed cell death. In tumor metastasis, programmed cell death (autophagy, apoptosis, and necroptosis) plays a key role. Malignant cancer cells have to overcome the different forms of cell death to transfer. The article sums up the recent studies on the mechanism of bone metastasis involving key regulatory factors such as macrophages and AKT and further discusses as to how regulating autophagy is crucial in relieving prostate cancer bone metastasis.Subject terms: Cancer models, Prostate cancer     

Neuroprotective Effect of <Emphasis Type="Italic">Rosmarinus officinalis</Emphasis> Extract on Human Dopaminergic Cell line,SH-SY5Y

Hydrogen peroxide (H₂O₂) is a major Reactive Oxygen Species (ROS), which has been implicated in many neurodegenerative conditions including Parkinson’s disease (PD). Rosmarinus officinalis (R. officinalis) has been reported to have various pharmacological properties including anti-oxidant activity. In this study, we investigated the neuroprotective effects of R. officinalis extract on H₂O₂-induced apoptosis in human dopaminergic cells, SH-SY5Y. Our results showed that H₂O₂-induced cytotoxicity in SH-SY5Y cells was suppressed by treatment with R. officinalis. Moreover, R. officinalis was very effective in attenuating the disruption of mitochondrial membrane potential and apoptotic cell death induced by H₂O₂. R. officinalis extract effectively suppressed the up-regulation of Bax, Bak, Caspase-3 and -9, and down-regulation of Bcl-2. Pretreatment with R. officinalis significantly attenuated the down-regulation of tyrosine hydroxylase (TH), and aromatic amino acid decarboxylase (AADC) gene in SH-SY5Y cells. These findings indicate that R. officinalis is able to protect the neuronal cells against H₂O₂-induced injury and suggest that R. officinalis might potentially serve as an agent for prevention of several human neurodegenerative diseases caused by oxidative stress and apoptosis.     

Apoptosis of Human Neuroblastoma Cells Induced by Liposome-Encapsulated Fenretinide

Abstract

Human neuroblastoma (NB) tumours represent a major therapeutic challenge due to the lack of drugs effective in controlling cell proliferation. We previously reported that the synthetic retinoid Fenretinide (HPR) inhibits NB cell growth through the induction of programmed cell death. More recently, various NB cell lines have been shown to be partially resistant, in vitro, to HPR used at in vivo achievable concentrations (1-3 μmol/L). To significantly increase the dose, half-life, and stability of this promising anticancer agent we studied a system of conventional or long-circulating liposomes.

In this study, we showed that HPR can be efficiently and stable encapsulated in conventional (CL-HPR) and stabilized liposomes (SL-HPR). Since the leakage of the drug from the liposomes under the experimental conditions used is negligible, it seems that HPR is entering cells via uptake of intact liposomes. Liposome-entrapped HPR completely arrested the growth of NB cells. The effect was dose- and time-dependent. Indeed, SL-HPR at 30 (imol/ L induced, in the cell lines partially resistant to free HPR, a very rapid (24-48 h) fall in thymidine uptake (> 95 %), whereas at 3 μmol/L it exhibited cytostatic effects.

Time lapse photomicroscopy showed that NB cells treated with SL-HPR underwent a death process highly reminiscent of apoptosis, with progressive condensation of the cytoplasm around the nucleus and intense cell shrinkage. The cells then rounded up and detached from the plate. Furthermore, propidium iodide staining of the DNA showed that a high proportion of cells treated with SL-HPR displayed a small and brightly staining nucleus; chromatin appeared aggregated into dense masses at the nuclear periphery, a typical feature of apoptotic cells. These findings were confirmed by electronic microscopy, DNA fragmentation assay, DNA content analysis and by a quantitative assay for evaluating programmed cell death based upon the labeling of DNA breaks with tritiated thymidine. HPLC analysis showed that HPR did not become metabolized after uptake into NB cells cultured in vitro, thus indicating that SL-HPR-induced apoptosis results from the action of HPR, itself, and not from its metabolite(s). In conclusion, our study demonstrates that Fenretinide entrapped in conventional or sterically stabilized liposomes dramatically suppresses NB cell growth by inducing programmed cell death.     

New Analogues of the Anticancer E7070: Synthesis and Pharmacology

Cell cycle control in the G1 phase has attracted considerable attention in recent cancer research, because many of the important proteins involved in G1 progression or G1/S transition have been found to play a crucial role in proliferation, differentiation, transformation, and programmed cell death (apoptosis). E7070 is a novel antitumor sulfonamide, with a unique mode of action that affects G1 progression of the cell cycle. A series of compounds containing an N-[1-(3,4,5-trimethoxybenzyl)-1H-indol-5-yl]benzene sulfonamide, analogues of E7070, was synthesized and evaluated as potential antitumor agents. Cell cycle analysis with PC3 human prostate cancer cells revealed a cellular accumulation in the G1 phase.     

Suppression of Tumor Growth by Pleurotus ferulae Ethanol Extract through Induction of Cell Apoptosis,and Inhibition of Cell Proliferation and Migration

Cancer is the second leading cause of death worldwide. Edible medicinal mushrooms have been used in traditional medicine as regimes for cancer patients. Recently anti-cancer bioactive components from some mushrooms have been isolated and their anti-cancer effects have been tested. Pleurotus ferulae, a typical edible medicinal mushroom in Xinjiang China, has also been used to treat cancer patients in folk medicine. However, little studies have been reported on the anti-cancer components of Pleurotus ferulae. This study aims to extract bioactive components from Pleurotus ferulae and to investigate the anti-cancer effects of the extracts. We used ethanol to extract anti-cancer bioactive components enriched with terpenoids from Pleurotus ferulae. We tested the anti-tumour effects of ethanol extracts on the melanoma cell line B16F10, the human gastric cancer cell line BGC 823 and the immortalized human gastric epithelial mucosa cell line GES-1 in vitro and a murine melanoma model in vivo. Cell toxicity and cell proliferation were measured by MTT assays. Cell cycle progression, apoptosis, caspase 3 activity, mitochondrial membrane potential (MMP), migration and gene expression were studied in vitro. PFEC suppressed tumor cell growth, inhibited cell proliferation, arrested cells at G0/G1 phases and was not toxic to non-cancer cells. PFEC also induced cell apoptosis and necrosis, increased caspase 3 activity, reduced the MMP, prevented cell invasion and changed the expression of genes associated with apoptosis and the cell cycle. PFEC delayed tumor formation and reduced tumor growth in vivo. In conclusion, ethanol extracted components from Pleurotus ferulae exert anti-cancer effects through direct suppression of tumor cell growth and invasion, demonstrating its therapeutic potential in cancer treatment.     

Crosstalk Between Bak/Bax and mTOR Signaling Regulates Radiation-Induced Autophagy

Bax and Bak, act as a gateway for caspase-mediated cell death. mTOR, an Akt downstream effector, plays a critical role in cell proliferation, growth and survival. The inhibition of mTOR induces autophagy, whereas apoptosis is a minor cell death mechanism in irradiated solid tumors.

We explored possible alternative pathways for cell death induced by radiation in Bax/Bak^-/- double knockout (DKO) MEF cells and wild-type cells, and we compared the cell survival: the Bax/Bak^-/- cells were more radiosensitive than the wild-type cells. The irradiated cells displayed an increase in the pro-autophagic proteins ATG5-ATG12 and Beclin-1.

These results are surprising in the fact that the inhibition of apoptosis resulted in increasing radiosensitivity; indicating that perhaps autophagy is the cornerstone in the cell radiation sensitivity regulation. Furthermore, irradiation up-regulates autophagic programmed cell death in cells that are unable to undergo Bax/Bak-mediated apoptosis. We hypothesize the presence of a phosphatase—possibly PTEN, an Akt/mTOR negative regulator that can be inhibited by Bax/Bak. This fits with our hypothesis of Bax/Bak as a down-regulator of autophagy.

We are currently conducting experiments to explore the relationship between apoptosis and autophagy. Future directions in research include strategies targeting Bax/Bak in cancer xenografts and exploring novel radiosensitizers targeting autophagy pathways.

Addendum to:

Autophagy for Cancer Therapy through Inhibition of Proapoptotic Proteins and mTOR Signaling

K.W. Kim, R.W. Mutter, C. Cao, J.M. Albert, M. Freeman, D.E. Hallahan and B. Lu

J Biol Chem 2006; Epub ahead of print     

Matrine induces programmed cell death and regulates expression of relevant genes based on PCR array analysis in C6 glioma cells

Matrine, one of the main components extracted from Sophora flavescens Ait, has a wide range of pharmacological effects including anti-tumor activities on a number of cancer cell lines. This study has investigated whether matrine could also display anti-tumor action on rat C6 glioma cells. Exposure of C6 cells to matrine resulted in inhibition of proliferation and induction of apoptosis in a dose-dependent manner, as measured by the MTT assay and Flow cytometry. The Annexin V/PI staining further detected the apoptotic cells at both early and late phases of apoptosis. We used AO/EB staining to examine the programmed cell death of matrine-treated C6 cells, and showed that the death rate detected by AO/EB staining was higher than the apoptosis rate measured by Annexin V/PI staining, suggesting that autophagy, the Type II programmed cell death, may be involved in matrine-induced cell death, which was further confirmed by electronic microscopy. To explore the molecular mechanism, an apoptosis real-time PCR array was performed, which has demonstrated that 57 genes were at least 2-fold upregulated, and 11 genes were at least 2-fold downregulated in matrine-treated C6 cells, compared with untreated cells. However, the gene expression profiles could only partly and roughly explain molecular mechanisms of apoptosis and autophagy in matrine-treated C6 cells, thus further investigations are required to confirm the specific molecular pathways and related molecules responsible for the programmed cell death.     

Some autophagic and apoptotic features of programmed cell death in the anterior silk glands of the silkworm,Bombyx mori

Programmed cell death has been subdivided into two major groups: apoptosis and autophagic cell death. The anterior silk gland of Bombyx mori degenerates during larval-pupal metamorphosis. Our findings indicate that two types of programmed cell death features are observed during this physiological process. During the prepupal period, pyknosis of the nucleus, cell detachment and membrane blebbing occur and they are the first signs of programmed cell death in the anterior silk glands. According to previous studies, all of these morphological appearences are common for both cell death types. Autophagy features are also exhibited during the prepupal period. One of the lysosomal marker enzymes, acid phosphatase, levels are high during this period then decrease gradually. Vacuole formation begins to appear first at the basal surface of the cell, then expands to the apical surface just before the larval pupal ecdysis. After larval-pupal ecdysis, DNA fragmentation, which is the obvious biochemical marker of apoptosis, is detected in agarose gel electrophoresis which also shows that caspase-like enzyme activities occur during the programmed cell death process of the anterior silk glands. Apoptosis and autophagic cell death interact with each other during the degeneration process of the anterior silk gland in Bombyx mori and this interaction occurs at a late phase of cell death. We suggest that only apoptotic cell death not enough for whole gland degeneration and that more effective degeneration occurs with this cooperation.

Addendum to: Goncu E, Parlak O. Morphological changes and patterns of ecdysone receptor B1 immunolocalization in the anterior silk gland undergoing programmed cell death in the silkworm, Bombyx mori. Acta Histochem 2008; In press.     

Gtdap-1 and the Role of Autophagy During Planarian Regeneration and Starvation

Planarians have been established as an ideal model organism for stem cell research and regeneration. Planarian regeneration and homeostasis require an exquisite balancing act between cell death and cell proliferation as new tissues are made (epimorphosis) and existing tissues remodeled (morphallaxis). Some of the genes and mechanisms that control cell proliferation and pattern formation are known. However, studies about cell death during remodeling are few and far between. We have studied the gene Gtdap-1, the planarian ortholog of human death-associated protein-1 or DAP-1. DAP-1 together with DAP-kinase has been identified as a positive mediator of programmed cell death induced by gamma-interferon in HeLa cells. We have found that the gene functions at the interface between autophagy and cell death in the remodeling of the organism that occurs during regeneration and starvation in sexual and asexual races of planarians. Our data suggest that autophagy of existing cells may be essential to fuel the continued proliferation and differentiation of stem cells by providing the necessary energy and building blocks to neoblasts.

Addendum to:

Gtdap-1 Promotes Autophagy and is Required for Planarian Remodeling During Regeneration and Starvation

C. González-Estévez, D.A. Felix, A.A. Aboobaker and E. Saló

Proc Natl Acad Sci USA 2007; 104:13373-8