Dysregulation of a potassium channel, THIK-1, targeted by caspase-8 accelerates cell shrinkage.

Activation of caspases is crucial for the execution of apoptosis. Although the caspase cascade associated with activation of the initiator caspase-8 (CASP8) has been investigated in molecular and biochemical detail, the physiological role of CASP8 is not fully understood. Here, we identified a two-pore domain potassium channel, tandem-pore domain halothane-inhibited K channel 1 (THIK-1), as a novel CASP8 substrate.

Functional conservation of the apoptotic machinery from coral to man: the diverse and complex Bcl-2 and caspase repertoires of Acropora millepora.

Background: Apoptotic cell death is a defining and ubiquitous characteristic of metazoans, but its evolutionary origins are unclear. Although Caenorhabditis and Drosophila played key roles in establishing the molecular bases of apoptosis, it is now clear that cell death pathways of these animals do not reflect ancestral characteristics. Conversely, recent work suggests that the apoptotic networks of cnidarians may be complex and vertebrate-like, hence characterization of the apoptotic complement of representatives of the basal cnidarian class Anthozoa will help us to understand the evolution of the vertebrate apoptotic network.

Conservation of structure and function in vertebrate c-FLIP proteins despite rapid evolutionary change.

Cellular FLICE-like inhibitory protein (c-FLIP, gene symbol ) was first identified as a negative regulator of death receptor-mediated apoptosis in mammals. To understand the ubiquity and diversity of the c-FLIP protein subfamily during evolution, c-FLIP orthologs were identified from a comprehensive range of vertebrates, including birds, amphibians, and fish, and were characterized by combining experimental and computational analysis. Predictions of three-dimensional protein structures and molecular phylogenetic analysis indicated that the conserved structural features of c-FLIP proteins are all derived from an ancestral caspase-8, although they rapidly diverged from the subfamily consisting of caspases-8, -10, and -18.

Evolutionary analyses of caspase-8 and its paralogs: Deep origins of the apoptotic signaling pathways.

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 apoptotic initiator caspase-8: its functional ubiquity and genetic diversity during animal evolution.

The caspases, a family of cysteine proteases, play multiple roles in apoptosis, inflammation, and cellular differentiation. Caspase-8 (Casp8), which was first identified in humans, functions as an initiator caspase in the apoptotic signaling mediated by cell-surface death receptors. To understand the evolution of function in the Casp8 protein family, casp8 orthologs were identified from a comprehensive range of vertebrates and invertebrates, including sponges and cnidarians, and characterized at both the gene and protein levels.

Transgenic Xenopus laevis for live imaging in cell and developmental biology.

The stable transgenesis of genes encoding functional or spatially localized proteins, fused to fluorescent proteins such as green fluorescent protein (GFP) or red fluorescent protein (RFP), is an extremely important research tool in cell and developmental biology. Transgenic organisms constructed with fluorescent labels for cell membranes, subcellular organelles, and functional proteins have been used to investigate cell cycles, lineages, shapes, and polarity, in live animals and in cells or tissues derived from these animals. Genes of interest have been integrated and maintained in generations of transgenic animals, which have become a valuable resource for the cell and developmental biology communities.

In vivo imaging of hierarchical spatiotemporal activation of caspase-8 during apoptosis.

Background: Activation of caspases is crucial for the execution of apoptosis. Although the caspase cascade associated with activation of the initiator caspase-8 (CASP8) has been investigated in molecular and biochemical detail, the dynamics of CASP8 activation are not fully understood.

Methodology/principal Findings: We have established a biosensor based on fluorescence resonance energy transfer (FRET) for visualizing apoptotic signals associated with CASP8 activation at the single-cell level.

Multiple functions of FADD in apoptosis, NF-κB-related signaling, and heart development in Xenopus embryos.

FADD is an adaptor protein that transmits apoptotic signals from death receptors. Additionally, FADD has been shown to play a role in various functions including cell proliferation. However, the physiological role of FADD during embryonic development remains to be delineated.

The molecular mechanism of apoptosis upon caspase-8 activation: quantitative experimental validation of a mathematical model.

Caspase-8 (CASP8) is a cysteine protease that plays a pivotal role in the extrinsic apoptotic signaling pathway via death receptors. The kinetics, dynamics, and selectivity with which the pathway transmits apoptotic signals to downstream molecules upon CASP8 activation are not fully understood. We have developed a system for using high-sensitivity FRET-based biosensors to monitor the protease activity of CASP8 and its downstream effector, caspase-3, in living single cells.

Caspase-8 cleavage of the interleukin-21 (IL-21) receptor is a negative feedback regulator of IL-21 signaling.

We screened a library of human single-transmembrane proteins (sTMPs), produced by a cell-free system, using a luminescent assay to identify those that can be cleaved by caspase-8 (CASP8). Of the 407 sTMPs screened, only the interleukin-21 receptor (IL21R), vezatin (VEZT), and carbonic anhydrase XIV were cleaved at Asp344, Asp655 and Asp53, respectively. We confirmed that IL21R and VEZT were also cleaved in apoptotic HeLa cells with the cleavage sites.

Expression and function of apoptosis initiator FOXO3 in granulosa cells during follicular atresia in pig ovaries.

In mammalian ovaries, most follicles are lost by atresia before ovulation. It has become apparent that the apoptosis of granulosa cells induces follicular atresia. Forkhead box O3 (FOXO3), also called FKHRL1 (forkhead in rhabdomyosarcoma-like 1), is a proapoptotic molecule that belongs to the FOXO subfamily of forkhead transcription factors.

Changes in expression and localization of X-linked inhibitor of apoptosis protein (XIAP) in follicular granulosa cells during atresia in porcine ovaries.

Follicular selection predominantly depends on granulosa cell apoptosis in porcine ovaries, but the molecular mechanisms regulating the induction of apoptosis in granulosa cells during follicular selection remain incompletely understood. To determine the role of X-linked inhibitor of apoptosis protein (XIAP), which suppresses caspase-3, -7 and -9 activities and acts as an endogenous inhibitor of apoptotic cell death, in the regulation of granulosa cell apoptosis during follicular atresia, we examined the changes in the expression level and localization of XIAP mRNA and protein in granulosa cells during follicular atresia using reverse transcription-polymerase chain reaction (RT-PCR), in situ hybridization, Western blotting and immunohistochemistry, respectively. High levels of XIAP mRNA and protein were noted in the granulosa cells of healthy follicles, and decreased levels were noted during follicular atresia.

cFLIP regulates death receptor-mediated apoptosis in an ovarian granulosa cell line by inhibiting procaspase-8 cleavage.

More than 99% of follicles in mammalian ovaries undergo atresia, but the mechanisms regulating the strict selection process are still unclear. Granulosa cell apoptosis is considered the trigger of follicular atresia, which occurs in advance of the death of an oocyte. Cellular FLICE-like inhibitory protein (cFLIP), a homologue of procaspase-8 (also called FLICE), is an intracellular anti-apoptotic protein.

Anti-apoptotic activity of porcine cFLIP in ovarian granulosa cell lines.

In mammalian ovaries, more than 99% of follicles undergo atresia during growth and development. Recently, we found that the expression of cellular FLICE-like inhibitory protein long form (cFLIP(L)) decreased during follicular atresia in granulosa cells of porcine ovaries. In humans and other species, both the short (cFLIP(S)) and long (cFLIP(L)) forms of cFLIP are considered to function as cell survival factors that inhibit death ligand receptor-mediated apoptosis.

The evolutionary conservation of the core components necessary for the extrinsic apoptotic signaling pathway, in Medaka fish.

Background: Death receptors on the cell surface and the interacting cytosolic molecules, adaptors and initiator caspases, are essential as core components of the extrinsic apoptotic signaling pathway. While the apoptotic machinery governing the extrinsic signaling pathway is well characterized in mammals, it is not fully understood in fish.

Results: We identified and characterized orthologs of mammalian Fas, FADD and caspase-8 that correspond to the death receptor, adaptor and initiator caspase, from the Medaka fish (Oryzias latipes).

Conserved function of caspase-8 in apoptosis during bony fish evolution.

Caspase-8, a member of the caspase family, plays an important role in apoptotic signal transduction in mammals. Here we report the identification and characterization of the caspase-8 (casp8) gene in the zebrafish Danio rerio. The zebrafish casp8 gene has a genomic organization similar to mammalian casp8 genes, consisting of 10 exons.

Oocyte growth and follicular development in KIT-deficient Fas-knockout mice.

In mammals, oocyte growth and follicular development are known to be regulated by KIT, a tyrosine kinase receptor. Fas is a member of the death receptor family inducing apoptosis. Here, we investigated germ cell survival, oocyte growth and follicular development in KIT-deficient (Wv/Wv:Fas+/+), Fas-deficient (+/+:Fas-/-), and both KIT- and Fas-deficient (Wv/Wv:Fas-/-) mice during fetal and postnatal periods.

Molecular characteristics of porcine Fas-associated death domain (FADD) and procaspase-8.

To reveal the intracellular signal transduction molecules involved in granulosa cell apoptosis in porcine ovarian follicles, we cloned the porcine Fas-associated death domain (FADD), an adaptor protein for the cell death receptor, and procaspase-8, an initiator caspase. Porcine FADD (pFADD) was 636 bp (211 amino acids: aa) long and showed 74.0 and 65.

Functional demonstration of the ability of a primary spermatogonium as a stem cell by tracing a single cell destiny in Xenopus laevis.

In Xenopus, although primary spermatogonium (PG), the largest cell in the testis, is believed to be spermatogonial stem cell by histological observations, functional evidence has never been obtained. In the present study, we first indicated that culture of juvenile testis in a medium supplemented with follicle stimulating hormone resulted in no proliferation of PG. In this culture system, early secondary spermatogonia could undergo mitotic divisions with a concomitant decrease in their size, so that they became distinguishable in size from PG.

The initiator caspase, caspase-10beta, and the BH-3-only molecule, Bid, demonstrate evolutionary conservation in Xenopus of their pro-apoptotic activities in the extrinsic and intrinsic pathways.

Two major apoptotic signaling pathways have been defined in mammals, the extrinsic pathway, initiated by ligation of death receptors, and the intrinsic pathway, triggered by cytochrome c release from mitochondria. Here, we identified and characterized the Xenopus homologs of caspase-10 (xCaspase-10beta), a novel initiator caspase, and Bid (xBid), a BH3-only molecule of the Bcl-2 family involved in both the extrinsic and intrinsic pathways. Exogenous expression of these molecules induced apoptosis of mammalian cells.

Transgenic Xenopus laevis strain expressing cre recombinase in muscle cells.

For reproducible analyses of gene function in Xenopus, the use of transgenic strains is a promising approach but has limitations when investigating factors interfering with development. Therefore, inducible systems are attractive alternatives, and a binary system based on recombinases is a most versatile approach. We have shown previously that Cre and FLP recombinases are active in Xenopus laevis and can induce a silent reporter gene in a corresponding reporter strain.

Characteristics of initiation and early events for muscle development in the Xenopus limb bud.

In Xenopus laevis, limb buds start to develop at a later point of the larval stage, prior to metamorphosis. This onset of limb development in Xenopus is totally different from that in amniotes such as birds and mammals, in which limb buds emerge at an early stage of embryogenesis, in parallel with other organogenesis. We investigated limb myogenesis in Xenopus, focusing on myogenic gene expression, myogenic ability of limb bud cells in the early stage, and the origin of myogenic precursor cells in the limb bud.

Partial correction of abnormal cardiac development in caspase-8-deficient mice by cardiomyocyte expression of p 35.

Baculovirus p 35 protein protects cells from apoptotic cell death by inhibiting caspase activation. We have established transgenic mouse lines specifically expressing p 35 in cardiomyocytes, and primary cardiomyocytes isolated from these mice exhibit resistance to staurosporine-induced apoptosis. In a previous study, we observed defects in heart formation associated with abdominal hemorrhage and cardiomyocyte cell death in caspase-8-deficient animals.

Regulation of endothelial cell death and its role in angiogenesis and vascular regression.

In multicellular organisms, apoptosis, also known as programmed cell death, is an important physiological response to eliminate unnecessary, excess, or harmful cells. Apoptosis occurs during embryonic development and is important in maintaining homeostasis during adulthood. Apoptosis also plays critical roles in angiogenesis and vessel regression.

Low temperature protects mammalian cells from apoptosis initiated by various stimuli in vitro.

Mild hypothermia shows protective effects on patients with brain damage and cardiac arrest. To elucidate the molecular mechanisms underlying these effects, we examined the effects of low temperature (32 degrees C) on cells exposed to a variety of stress in vitro. We found that 32 degrees C suppressed induction of apoptosis by cytotoxic stimuli such as adriamycin, etoposide, thapsigargin, NaCl, H(2)O(2), and anti-Fas antibody.