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Curr Biol,
2009]
For ectotherms, lifespan is increased at low temperature and decreased at high temperature. A new study in Caenorhabditis elegans shows that thermosensory neurons can counteract the effects of high temperature on lifespan by controlling the activity of a steroid signaling pathway.
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J Biochem,
2009]
The accumulation of unfolded proteins in the endoplasmic reticulum (ER) under ER stress conditions activates a series of homoeostatic responses collectively termed the unfolded protein response (UPR). The UPR is unique in which the molecular mechanisms it uses to transmit signals from the ER lumen to the nucleus are completely different to those used for signalling from the plasma membrane. An ER stress signal is sensed and transmitted across the membrane by a transmembrane protein(s) in the ER. Interestingly, the number of such functional sensors/transducers, ubiquitously expressed, has increased with evolution, for example, one in Saccharomyces cerevisiae, two in Caenorhabditis elegans and Drosophila melanogaster, and three in mammals. Accordingly, mammalian cells are able to cope with ER stress in a more sophisticated manner. Here, I summarize the mechanisms and activation consequences of UPR signalling pathways in yeast, worm, fly and mammalian cells. I also discuss how they have evolved to counteract ER stress effectively.
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Annu Rev Genet,
1999]
Molecular genetic analysis of chemotaxis and theramotaxis in Caenorhabditis elegans has revealed the molecular bases of olfaction, taste, and thermosensation, which, in turn, has demonstrated that sensory signaling in C. elegans is very similar to that in vertebrates. A cyclic nucleotide-gated channel (TAX-2/TAX-4) that is highly homologous to the olfactory and photoreceptor channels in vertebrates is required for taste and thermosensation, in addition to olfaction. A cation channel (OSM-9) that is closely related to a capsaicin receptor channel is required for olfactory adaptation in one olfactory neuron and olfactory sensation in the other olfactory neuron. A novel G alpha protein (ODR-3) is essential for olfactory responses in all olfactory neurons and aversive responses in a polymodal sensory neuron. A G protein-coupled seven-transmembrane receptor (ODR-10) is the first olfactory receptor whose ligand was elucidated. Using chemotaxis and thermotaxis as behavioral paradigms, neural plasticity including learning and memory can be studied genetically in C. elegans.
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Bioessays,
1997]
Chemotaxis and thermotaxis in Caenorhabditis elegans are based on the chemical senses (smell and taste) and the thermal sense, respectively, which are important for the life of the animal. Laser ablation experiments have allowed identification of sensory neurons and some interneurons required for these senses. Many mutants that exhibit various abnormalities have been isolated and analyzed. These studies have predicted novel signaling pathways whose components include a putative odorant specific transmembrane receptor (ODR-10) and a cyclic nucleotide-gated channel (TAX-4/TAX-2) functioning in taste and thermosensation as well as in smell. The emerging picture of the mechanisms of sensory transduction in C. elegans seems to be basically similar to what is known of visual and olfactory sensory transduction in vertebrates. Thus, molecular and cellular analyses of chemotaxis and thermotaxis in C. elegans have proved useful and will continue to provide significant implications for the molecular basis of sensory systems in higher animals.
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Nihon Shinkei Seishin Yakurigaku Zasshi,
2004]
The molecular mechanisms of neural plasticity, learning and memory are still poorly understood. The nematode Caenorhabditis elegans is capable of responding to a variety of environmental changes through its nervous system, consisting of only 302 neurons. C. elegans is an ideal model organism to elucidate neural plasticity, learning and memory at molecular, cellular and neuronal network levels. Thermotaxis behavior is particularly amenable to dissect learning and memory at all these levels. After cultivation at a certain temperature with food, C. elegans migrates to the cultivation temperature on a temperature gradient. By contrast, cultivation in food-deprived condition induces cultivation temperature avoidance behavior on a temperature gradient. We have been conducting forward as well as reverse genetic approaches to identify molecules, neurons and neuronal networks that are responsible for aspects of learning and memory in thermotaxis behavior.
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Curr Opin Neurobiol,
2007]
Elucidation of the principal mechanism for sensory transduction, learning and memory is a fundamental question in neurobiology. The simple nervous system composed of only 302 neurons and the description of neural wiring combined with developed imaging techniques facilitate cellular and circuit level analysis of behavior in the nematode Caenorhabditis elegans. Recent comprehensive analysis of worm thermotaxis, an experience-modulated behavior, has begun to reveal molecular, cellular, and neural circuit basis of thermosensation and neural plasticity.
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Traffic,
2003]
Proteins must be correctly folded and assembled to fulfill their functions as assigned by genetic code. All living cells have developed systems to counteract protein unfolding or misfolding. A typical example of such a homeostatic response is triggered when unfolded proteins are accumulated in the endoplasmic reticulum. Eukaryotic cells cope with endoplasmic reticulum stress by attenuating translation, generally to decrease the burden on the folding machinery, as well as by inducing transcription of endoplasmic reticulum-localized molecular chaperones and folding enzymes to augment folding capacity. These translational and transcriptional controls are collectively termed the unfolded protein response. The unfolded protein response is unique in that the molecular mechanisms it uses to transmit signals from the endoplasmic reticulum lumen to the nucleus are completely different from those used for signaling from the plasma membrane. Frame switch splicing (a term newly proposed here) and regulated intramembrane proteolysis (proposed by Brown et al., Cell 2000; 100: 391-398) employed by the unfolded protein response represent novel ways to activate a signaling molecule post-transcriptionally and post-translationally, respectively. They are critically involved in various cellular regulation pathways ranging from bacterial extracytoplasmic stress response to differentiation of mature B cells into antibody-secreting plasma cells. Further, mammalian cells take advantage of differential properties between the two mechanisms to determine the fate of proteins unfolded or misfolded in the endoplasmic reticulum. This review focuses on the transcriptional control that occurs during the unfolded protein response in various species.
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Nihon Shinkei Seishin Yakurigaku Zasshi,
2010]
Recent studies have provided extensive molecular insights into neuronal polarity establishment in vitro. However, it is still poorly understood how the corresponding phenomenon occurs and leads to correct localization of synaptic components in vivo. RIA interneurons in the nematode C. elegans have a neurite clearly divided into pre- and post-synaptic regions and act as a pivotal component of the neural circuit for thermotaxis behavior, thereby providing a suitable model to elucidate these issues. We found that loss of Inositol Monophosphatase (IMPase) encoded by the
ttx-7 gene, an Inositol-producing enzyme regarded as a bipolar disorder-relevant molecule for its Lithium sensitivity, causes defects in thermotaxis behavior and localization of synaptic proteins in RIA neurons in vivo. Both behavioral and localization defects in
ttx-7 mutants were rescued by expression of IMPase at the adult stage and Inositol application, and were mimicked by Lithium application in wild type animals. These results suggest that IMPase is required in the mature nervous system for regulating correct localization of synaptic components in the central interneurons in order for animals to behave properly.
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Mech Ageing Dev,
2018]
Past investigations have shown that various plant extracts are capable of promoting longevity in lower model organisms like Caenorhabditis elegans, Drosophila melanogaster, Saccharomyces cerevisiae, Bombyx mori etc. Longevity studies on such organisms provide a foundation to explore anti-aging efficacies of such plant extracts in higher organisms. Plant extracts of acai palm, apple, asparagus, blueberry, cinnamon, cocoa, Damnacanthus, maize, mistletoe, peach, pomegranate, Rhodiola, rose, Sasa, turmeric, and Withania have extended lifespan in lower model organisms via diverse mechanisms like insulin like growth factor (IGF) signaling pathway, and antioxidant defense mechanisms. Knowledge of pathways altered by the extracts can be investigated as potential drug-targets for natural anti-aging interventions. Thus, the aim of the review is to scrutinize longevity promoting efficacies of various plant extracts in lower model organisms.
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FEMS Immunol Med Microbiol,
2005]
Recently, the use of invertebrate models of infection has given exciting insights into host-pathogen interaction for a number of bacteria. In particular, this has revealed important factors of the host response with remarkable parallels in higher organisms. Here, we review the advances attained in the elucidation of virulence determinants of a major human pathogen, Staphylococcus aureus, in relation to the invertebrate models thus far applied, the silkworm (Bombyx mori), the fruit fly (Drosophila melanogaster) and the roundworm (Caenorhabditis elegans). Also, the major pathways of host defence are covered in light of the response to S. aureus and the similarities and divergences in innate immunity of vertebrates and invertebrates. Consequently, we comparatively consider pathogen recognition receptors, signal transduction pathways (including Toll, Imd and others), and the humoral and cellular antimicrobial effectors. The technically convenient and ethically acceptable invertebrates appear as a valuable first tool to discriminate molecules participating from both sides of the host-S. aureus interaction as well as a high throughput method for antimicrobial screening.