Although Caenorhabditis and Drosophila proved invaluable in unraveling the molecular mechanisms of apoptosis, it is now clear that these animals are of limited value for understanding the evolution of apoptotic systems. Whereas data from these invertebrates led to the assumption that the extrinsic apoptotic pathway is restricted to vertebrates, recent data from cnidarians and sponges indicate that this pathway predates bilaterian origins. Here we review the phylogenetic distribution of caspase‐8, the initiator caspase of the extrinsic apoptotic pathway, its (...) paralogs and other components of the network. The ancestral caspase‐8 gave rise to four paralogs early in vertebrate evolution, and these have been maintained in many tetrapods. However, eutherians have lost caspase‐18 and myomorph rodents have lost caspase‐10, these losses suggesting functional redundancy amongst caspase‐8 paralogs. The apoptotic network of the eumetazoan ancestor appears to have been complex and vertebrate like, and is only now being revealed by studying simple animals. (shrink)

Previous studies have shown that zinc deficiency leads to apoptosis of neuronal precursor cells in vivo and in vitro. In addition to the role of p53 as a nuclear transcription factor in zinc deficient cultured human neuronal precursors (NT-2), we have now identified the translocation of phosphorylated p53 to the mitochondria and p53-dependent increases in the pro-apoptotic mitochondrial protein BAX leading to a loss of mitochondrial membrane potential as demonstrated by a 25% decrease in JC-1 red:green fluorescence ratio. Disruption of (...) mitochondrial membrane integrity was accompanied by efflux of the apoptosis inducing factor (AIF) from the mitochondria and translocation to the nucleus with a significant increase in reactive oxygen species (ROS) after 24 h of zinc deficiency. Measurement of caspase cleavage, mRNA, and treatment with caspase inhibitors revealed the involvement of caspases 2, 3, 6, and 7 in zinc deficiency-mediated apoptosis. Down-stream targets of caspase activation, including the nuclear structure protein lamin and polyADP ribose polymerase (PARP), which participates in DNA repair, were also cleaved. Transfection with a dominant-negative p53 construct and use of the p53 inhibitor, pifithrin- ␮, established that these alterations were largely dependent on p53. Together these data identify a cascade of events involving mitochondrial p53 as well as p53-dependent caspase-mediated mechanisms leading to apoptosis during zinc deficiency. (shrink)

The acidic (leucine‐rich) nuclear phosphoprotein 32 kDa (ANP32) family is composed of small, evolutionarily conserved proteins characterized by an N‐terminal leucine‐rich repeat domain and a C‐terminal low‐complexity acidic region. The mammalian family members (ANP32A, ANP32B, and ANP32E) are ascribed physiologically diverse functions including chromatin modification and remodelling, apoptotic caspase modulation, protein phosphatase inhibition, as well as regulation of intracellular transport. In addition to reviewing the widespread literature on the topic, we present a concept of the ANP32s as having a (...) whip‐like structure. We also present hypotheses that ANP32C and other intronless sequences should not currently be considered bona fide family members, that their disparate necessity in development may be due to compensatory mechanisms, that their contrasting roles in cancer are likely context‐dependent, along with an underlying hypothesis that ANP32s represent an important node of physiological regulation by virtue of their diverse biochemical activities. (shrink)

Programmed cell death (PCD) or apoptosis is a broadly conserved phenomenon in metazoans, whereby activation of canonical signal pathways induces an ordered dismantling and death of a cell. Paradoxically, the constituent proteins and pathways of PCD (most notably the metacaspase/caspase protease mediated signal pathways) have been demonstrated to retain non‐death functions across all phyla including yeast, nematodes, drosophila, and mammals. The ancient conservation of both death and non‐death functions of PCD proteins raises an interesting evolutionary conundrum: was the primordial (...) intent of these factors to induce cell death or to regulate other cellular adaptations? Here, we propose the hypothesis that apoptotic behavior of PCD proteins evolved or were co‐opted from core non‐death functions. (shrink)

Recent reports suggest that the yeast Saccharomyces cerevisiae caspase‐related metacaspase, Mca1, is required for cell‐autonomous cytoprotective functions that slow cellular aging. Because the Mca1 protease has previously been suggested to be responsible for programmed cell death (PCD) upon stress and aging, these reports raise the question of how the opposing roles of Mca1 as a protector and executioner are regulated. One reconciling perspective could be that executioner activation may be restricted to situations where the death of part of the (...) population would be beneficial, for example during colony growth or adaptation into specialized survival forms. Another possibility is that metacaspases primarily harbor beneficial functions and that the increased survival observed upon metacaspase removal is due to compensatory responses. Herein, we summarize data on the role of Mca1 in cell death and survival and approach the question of how a metacaspase involved in protein quality control may act as killer protein. -/- . (shrink)

On the basis of the evidence that tumor development is suppressed by the embryonic microenvironment, some experiments using the factors taken from Zebrafish embryo at precise stages of cell differentiation were made. These experiments demonstrated a significant growth inhibition on different tumor cell lines in vitro. The observed mechanism of tumor growth inhibition is connected with the key-role cell cycle regulation molecules, such as p53 and pRb, which are modified by transcriptional or post-translational processes. Research on apoptosis and differentiation revealed (...) that treatment with these factors induces caspase-3 with a p73 apoptotic-dependent pathway activation and a concurrent significant normalization of e-cadherin and beta-catenin ratio. Other experiments found a synergistic effect on the colon cancer proliferation curve after the concurrent treatment with these factors and 5-fluorouracil. Finally, a product prepared for human therapy demonstrated 19.8% regression and 16% stable disease in an... (shrink)

Experiments carried out on different tumor cell lines showed a significative growth reduction of all treated lines due to the administration of zebrafish embryo extracts withdrawn at different stem cells differentiation stages. Research conducted in order to establish which molecular events were involved in control and downregulation of cancer cell lines demonstrated a transcriptional regulation of the key cell cycle onco-supressor gene, like p53 and a post-translational modification of molecules, like pRb. Research on apoptosis and differentiation processes showed that stem (...) cells differentiating factors induce caspase-3 activation, mainly through E2F-1 gene regulation, thus hyper expressing c-Myc and activating a p73-dependent apoptotic pathway. Moreover, we demonstrated a concurrent and significative normalization of the e-cadherin/β-catenin expression, with an e-cadherin rise. Administration of SCDF in an open clinical randomized clinical trail conducted on 179 patients affected by interme... (shrink)

Apoptotic pathways have always been regarded as a key‐player in preserving tissue and organ homeostasis. Excessive activation or resistance to activation of cell death signaling may indeed be responsible for several mechanisms of disease, including malignancy and chronic degenerative diseases. Therefore, targeting apoptotic factors gained more and more attention in the scientific community and novel strategies emerged aimed at selectively blocking or stimulating cell death signaling. This is also the case for the TMEM219 death receptor, which is activated by a (...) circulating ligand, the Insulin‐like growth factor binding protein 3 (IGFBP3) and induces a caspase‐8‐dependent apoptosis of the target cells. Interestingly, stimulation of the IGFBP3/TMEM219 axis exerts an anti‐proliferative effect, while blockade of the TMEM219 deleterious signal protects TMEM219‐expressing cells of the endocrine pancreas, lung, and intestine from damage and death. Here, we summarize the most updated reports on the role of the IGFBP3/TMEM219 apoptotic axis in disease conditions, including intestinal disorders and diabetes, and we describe the advancements in designing and testing novel TMEM219‐based targeting approaches in emerging potential clinical applications. (shrink)

One of the near-to-invariant hallmarks of early apoptosis (programmed cell death) is mitochondrial membrane permeabilization (MMP). It appears that mitochondria fulfill a dual role during the apoptotic process. On the one hand, they integrate multiple different pro-apoptotic signal transducing cascades into a common pathway initiated by MMP. On the other hand, they coordinate the catabolic reactions accompanying late apoptosis by releasing soluble proteins that are normally sequestered within the intermembrane space. In a recent study,(1) Li et al. described a nuclear (...) transcription factor (Nur77/TR1/NGFI-B) that can translocate to mitochondrial membranes to induce MMP. Moreover, two groups(2,3) identified a novel intermembrane protein (Smac/DIABLO) that specifically neutralizes the inhibitor of apoptosis (IAP) proteins, thereby facilitating the activation of caspases, a class of proteases activated during apoptosis. These findings refine our knowledge how MMP connects to the cellular suicide machinery. BioEssays 23:111–115, 2001. © 2001 John Wiley & Sons, Inc. (shrink)

Programmed cell death (PCD) is a process aimed at the removal of redundant, misplaced, or damaged cells and it is essential to the development and maintenance of multicellular organisms. In contrast to the relatively well‐described cell death pathway in animals, often referred to as apoptosis, mechanisms and regulation of plant PCD are still ill‐defined. Several morphological and biochemical similarities between apoptosis and plant PCD have been described, including DNA laddering, caspase‐like proteolytic activity, and cytochrome c release from mitochondria. Reactive (...) oxygen species (ROS) have emerged as important signals in the activation of plant PCD. In addition, several plant hormones may exert their respective effects on plant PCD through the regulation of ROS accumulation. The possible plant PCD regulators discussed in this review are integrated in a model that combines plant‐specific regulators with mechanisms functionally conserved between animals and plants. BioEssays 25:47–57, 2003. © 2002 Wiley Periodicals, Inc. (shrink)

Interleukin 1β‐converting enzyme (ICE)‐like proteases (caspases) play an important role in programmed cell death (apoptosis), and elucidating the consequences of their proteolytic activity is central to our understanding of the molecular mechanisms of cell death. Diverse structural and regulatory proteins and enzymes, including protein kinase Cδ, the retinoblastoma protein (a protein involved in cell survival), the DNA repair enzyme DNA‐dependent protein kinase and the nuclear lamins, undergo specific and limited endoproteolytic cleavage by various caspases during apoptosis. Since individual caspases can (...) cleave multiple substrates, the consequences of cleavage of only a single substrate are still poorly understood. Nevertheless, proteolytic activation of protein kinase Cδ may be an important early step in the cell death pathway, and cleavage of the retinoblastoma protein could suppress its cell survival function, whereas proteolytic inactivation of DNA repair enzymes might compromise the ability of the cell to reverse DNA fragmentation. On the other hand, cleavages of nuclear and cytoplasmic structural proteins (e.g. the lamins and Gas2) appear to be required for or contribute to the dramatic rearrangements in cellular architecture that are necessary for the completion of the cell death process. An emerging theme is that parallel and sequential proteolytic activation and inactivation of key protein substrates occurs during the multiple steps of apoptosis. (shrink)

Although the Bcl‐2 family members and p53 are involved in the regulation of apoptosis, the status of apoptotic machinery (eg caspases) plays a major role in determining the mode and timing of cell death. If the apoptotic machinery is lost, inhibited, or intrinsically inactivated, the “death stars”, Bcl‐2 and p53, may become irrelevant to cell death. In this light, high levels of Bcl‐2 may indicate that downstream apoptotic pathways are still functional. This explains why Bcl‐2 overexpression can be a marker (...) of chemosensitivity and favorable prognosis in certain cancers and why retention of wild‐type p53 may manifest inactivation of caspases in aggressive cancers. BioEssays 23:947–953, 2001. © 2001 John Wiley & Sons, Inc. (shrink)

Activating the ERK pathway (extracellular signal‐regulated kinase pathway) has proven beneficial in several models of Huntington's disease (HD), and drugs that are protective in HD models have recently been found to activate ERK. Thus, the ERK cascade may be a potential target for therapeutic intervention in this currently untreatable disorder. HD is caused by an expanded polyglutamine repeat in the huntingtin (Htt) protein that actuates a diverse set of pathogenic mechanisms. In response to mutant Htt, ERK is activated and directs (...) a protective transcriptional response and inhibits caspase activation. Paradoxically, Htt also interferes with several signaling events of the ERK pathway. Mutant Htt compromises the ERK‐dependent transcriptional response to corticostriatal BDNF signaling. Mutant Htt also hinders glutamate uptake from the synaptic cleft by down‐regulating ERK‐dependent expression of glutamate transporters, leaving cells vulnerable to excitotoxicity. Some of this cellular complexity can be capitalized on to achieve selective activation of ERK, which can be protective. (shrink)

A distinct group of receptors including DCC, UNC5, RET and Ptc1 is known to function in ligand‐dependent neuronal growth and differentiation or axon guidance. Acting as “dependence receptors”, they may also regulate neuronal cell survival by inducing apoptosis in the absence of cognate ligand. Receptor‐initiated apoptosis requires proteolytic (caspase) cleavage and exposure of a pro‐apoptotic region in the cytoplasmic domains of the receptors. In contrast, classical apoptosis induced by growth factor or cytokine deprivation involves loss of survival signaling without (...) receptor cleavage. DCC, UNC5, RET and Ptc1 are downregulated or mutated in diverse cancers, and show properties characteristic of tumor suppressors, consistent with their ability to promote neuronal cell death. Dysfunctional dependence receptors have been linked to the loss of specific neurons in certain inherited and neurodegenerative diseases. Dependence receptor‐initiated apoptosis represents a novel paradigm for the controlled removal of specific cells during neural development and elimination of malignant cells that have strayed beyond regions of ligand availability. BioEssays 26:656–664, 2004. © 2004 Wiley Periodicals, Inc. (shrink)