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[
Nat Neurosci,
2000]
A recent Nature paper on mice lacking the Na+ channel BNC1 shows that this channel is essential for neuronal touch receptor function and may be part of a mechanosensory complex.
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[
Mech Ageing Dev,
2002]
Oxidative damage to cellular macromolecules has been postulated to be a major contributor to the ageing of diverse organisms. Oxidative damage can be limited by maintaining high anti-oxidant defenses and by clearing/repairing damage efficiently. Protein turnover is one of the main routes by which functional proteins are maintained and damaged proteins are removed. Protein turnover rates decline with age, which might contribute to the accumulation of damaged proteins in ageing cells. Interestingly, protein turnover rates are maintained at high levels in caloric restricted animals. Whether changes in protein turnover are a cause or a consequence of ageing is not clear, and this question has not been a focal point of modern ageing research. Here we survey work on protein turnover and ageing and suggest that powerful genetic models such as the nematode Caenorhabditis elegans are well suited for a thorough investigation of this long-standing question.
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[
Nat Rev Genet,
2003]
If invertebrate neurons are injured by hostile environments or aberrant proteins they die much like human neurons, indicating that the powerful advantages of invertebrate molecular genetics might be successfully used for testing specific hypotheses about human neurological diseases, for drug discovery and for non-biased screens for suppressors and enhancers of neurodegeneration. Recent molecular dissection of the genetic requirements for hypoxia, excitotoxicity and death in models of Alzheimer disease, polyglutamine-expansion disorders, Parkinson disease and more, is providing mechanistic insights into neurotoxicity and suggesting new therapeutic interventions. An emerging theme is that neuronal crises of distinct origins might converge to disrupt common cellular functions, such as protein folding and turnover.
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[
International Worm Meeting,
2021]
Axonal regeneration is a promising approach to overcome impaired functionality due to axonal injury. In mammals, central nervous system has poor regenerative capacity due to both extrinsic and intrinsic factors. The regenerative capacity also declines significantly with ageing. Therefore, functional axon regeneration in adulthood is challenging and needs more understanding. The pharmacological manipulations are not very successful for functional restoration whereas rehabilitation and physical activity shows improvement. As physical exercise has complex systemic effects, understanding the downstream effectors of physical exercise that is relevant for axon regeneration might be useful. Studying this using simple model organism has several advantages. Using posterior gentle touch circuit neuron (PLM) of Caenorhabditis elegans, we are studying effect of swimming exercise on functional restoration after laser assisted axotomy. We found that a single swimming exercise session of 90 minutes, which is an established paradigm of exercise in worm (Laranjeiro et al., 2017; Laranjeiro et al., 2019) improves functional recovery irrespective of age. However multiple swimming session is required for older worms (A5 stage). Anatomical correlation showed that swimming session improves regrowth initiation, regrowth length and functional connections. We found that the energy sensor kinase AMPK/AAK-2 plays an essential role mediating swimming benefits. Characterizing tissue specific requirement, we found that it has both cell autonomous (PLM neuron) and non-autonomous (muscle) requirement. Pharmacological activation of AMPK/AAK-2 showed enhanced functional restoration similar to swimming. We are studying the downstream molecules and their specific roles in various tissues for swimming mediated functional enhancement which will be helpful for better implementation of this approach. References Laranjeiro R, Harinath G, Burke D, Braeckman BP, Driscoll M (2017) Single swim sessions in C. elegans induce key features of mammalian exercise. BMC Biology 15. Laranjeiro R, Harinath G, Hewitt JE, Hartman JH, Royal MA, Meyer JN, Vanapalli SA, Driscoll M (2019) Swim exercise in Caenorhabditis elegans extends neuromuscular and gut healthspan, enhances learning ability, and protects against neurodegeneration. Proc Natl Acad Sci U S A 116:23829-23839.
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[
International C. elegans Meeting,
1997]
The
egl-46 gene is required for the correct differentiation of the HSN neurons, a pair of motor neurons necessary for egg-laying (1,2). In addition, an extra pair of touch receptor-like cells is present in
egl-46 mutant animals (3). This finding led to the hypothesis that
egl-46 represses touch cell fate in these cells. We have cloned the
egl-46 gene using transformation rescue and we have confirmed the assignment by identifying the mutations present in the four known
egl-46 alleles. A 5.5kb fragment of CO9E6 partially rescues the Egl phenotype of
egl-46 animals. The
egl-46 gene (K11G9.4) encodes a C2H2 zinc finger protein that contains three putative zinc fingers. We have confirmed the exon-intron structure of
egl-46 by sequencing a cDNA and by 5' RACE analysis.
egl-46::lacZ and
egl-46::GFP reporter constructs are expressed in a complex pattern which includes cells in the head, tail and ventral cord. We are now trying to determine the identity of the staining cells. Future work will address the mechanism by which the
egl-46 gene controls neuronal fate and/or differentiation. (1) Desai, C., Garriga, G., McIntire, S.L. and H.R.Horvitz (1988) Nature 336, 638-646. (2) Desai, C. and H.R.Horvitz (1989) Genetics 121, 703-721. (3) Mitani, S., Du, H., Hall, D.H., Driscoll, M. and M. Chalfie (1993) Development 119, 773-783.
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[
Biochemistry,
2012]
Decapping scavenger (DcpS) enzymes catalyze the cleavage of a residual cap structure following 3' 5' mRNA decay. Some previous studies suggested that both m(7)GpppG and m(7)GDP were substrates for DcpS hydrolysis. Herein, we show that mononucleoside diphosphates, m(7)GDP (7-methylguanosine diphosphate) and m(3)(2,2,7)GDP (2,2,7-trimethylguanosine diphosphate), resulting from mRNA decapping by the Dcp1/2 complex in the 5' 3' mRNA decay, are not degraded by recombinant DcpS proteins (human, nematode, and yeast). Furthermore, whereas mononucleoside diphosphates (m(7)GDP and m(3)(2,2,7)GDP) are not hydrolyzed by DcpS, mononucleoside triphosphates (m(7)GTP and m(3)(2,2,7)GTP) are, demonstrating the importance of a triphosphate chain for DcpS hydrolytic activity. m(7)GTP and m(3)(2,2,7)GTP are cleaved at a slower rate than their corresponding dinucleotides (m(7)GpppG and m(3)(2,2,7)GpppG, respectively), indicating an involvement of the second nucleoside for efficient DcpS-mediated digestion. Although DcpS enzymes cannot hydrolyze m(7)GDP, they have a high binding affinity for m(7)GDP and m(7)GDP potently inhibits DcpS hydrolysis of m(7)GpppG, suggesting that m(7)GDP may function as an efficient DcpS inhibitor. Our data have important implications for the regulatory role of m(7)GDP in mRNA metabolic pathways due to its possible interactions with different cap-binding proteins, such as DcpS or eIF4E.
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[
J Infect Dis,
2015]
BACKGROUND: Elimination of onchocerciasis and lymphatic filariasis is targeted for 2020. Given the coincident Loa loa infections in Central Africa and the potential for drug resistance development, the need for new microfilaricides and macrofilaricides has never been greater. With the genomes of L. loa, Onchocerca volvulus, Wuchereria bancrofti, and Brugia malayi available, new drug targets have been identified. METHODS: The effects of the tyrosine kinase inhibitors imatinib, nilotinib, and dasatinib on B. malayi adult males, adult females, L3 larvae, and microfilariae were assessed using a wide dose range (0-100 M) in vitro. RESULTS: For microfilariae, median inhibitory concentrations (IC50 values) on day 6 were 6.06 M for imatinib, 3.72 M for dasatinib, and 81.35 M for nilotinib; for L3 larvae, 11.27 M, 13.64 M, and 70.98 M, respectively; for adult males, 41.6 M, 3.87 M, and 68.22 M, respectively; and for adult females, 42.89 M, 9.8 M, and >100 M, respectively. Three-dimensional modeling suggests how these tyrosine kinase inhibitors bind and inhibit filarial protein activity. CONCLUSIONS: Given the safety of imatinib in humans, plans are underway for pilot clinical trials to assess its efficacy in patients with filarial infections.
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[
International Worm Meeting,
2003]
The ion channel formed by MEC-4 and MEC-10 is proposed to mediate sensory mechanotransduction in C. elegans touch cells. Initial efforts to reconstitute this channel in heterologous cells have shown that MEC-4 and MEC-10 form an amiloride-sensitive, Na+-selective ion channel complex together with MEC-2 stomatin and MEC-6 paraoxonase (1, 2). We are using double mutant cycle analysis to map the interaction surface between the pore-forming subunits, MEC-4 and MEC-10. Our general approach is to co-express wild-type and mutant forms of MEC-4 and MEC-10 and identify interacting amino acid residues using the antagonist, amiloride, as a probe. Preliminary findings have already identified one such interaction site: the d position. The importance of the d position was first highlighted by gain-of-function mutations in genes encoding ASC proteins in C. elegans (3, 4) that cause neuronal degeneration in vivo. In both MEC-4 and MEC-10, the wild-type residue is an alanine. Thus far, we have analyzed mutations that cause neuronal degeneration in vivo (T, V, and D) and mutations that we predict will be similar to wild-type (S, C). Our initial results are consistent with the idea that d position forms part the interaction surface between MEC-4 and MEC-10. We speculate that residues at this position contribute to a gate that regulates access to the amiloride binding site in the ion channel pore. 1. M. B. Goodman et al., Nature 415, 1039-42. (2002); 2. D. S. Chelur et al., Nature 420, 669-673 (2002); 3. M. Driscoll, M. Chalfie, Nature 349, 588-593 (1991); 4. M. Chalfie, E. Wolinsky, Nature 345, 410-416 (1990).
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[
Worm Breeder's Gazette,
1976]
We have studied maternal effects in 23 zyg ts mutants to estimate the times of expression of genes whose products are required in embryogenesis. We have used the following three tests, called arbitrarily A, B, and C. A test: Heterozygous (m/+) L4's are shifted to 25 C and allowed to self-fertilize. If 100% of their eggs yield larvae (25% of which express the mutant phenotype as adults), then the mutant is scored as maternal (M). If 25% of the F1 eggs fail to hatch, then the mutant is scored as non-maternal (N). An M result indicates that expression of the + allele in the parent allows m/m zygotes to hatch and grow to adulthood. A result of N indicates the opposite: that the + allele must be expressed in the zygote for hatching to occur. Out of 23 zyg mutants tested, 3 were scored N and 20 were scored M in the A test. Therefore, for most of the genes defined by these mutants, expression in the parent is sufficient for zygote survival, even if the gene is not expressed in the zygote. B test: Homozygous (m/m) hermaphrodites reared at 25 C are mated with N2 (+/+) males. If eggs fail to hatch at 25 C, but mated hermaphrodites shifted to 16 C produce cross progeny to give proof of mating, then the mutant is scored M. If cross progeny appear in the 25 C mating, then the mutant is scored N. An M result indicates that expression of the + allele in the zygote is not sufficient to allow m/+ progeny of an m/m hermaphrodite to survive. Conversely an N result indicates either that zygotic expression of the + allele is sufficient for survival, or that a sperm function or factor needed for early embryogenesis can be supplied paternally (see C test below). Out of the 23 zyg mutants tested, 11 were scored M and 12 were scored N. The combined results of A and B tests and their simplest interpretation are as follows. Ten mutants are M,M; the genes defined by these mutants must be expressed in the hermaphrodite parent for the zygote to survive. Ten mutants are M,N; these genes can be expressed either in the parent or in the zygote. Two mutants are N,N; these genes must be expressed in the zygote. One mutant is N,M; this gene must be expressed both in the maternal parent and in the zygote. C test: Homozygous (m/m) hermaphrodites reared at 25 C are mated with heterozygous (m/+) males. If rescue by a +/+ male in the B test depends on the + allele, then only half the cross progeny zygotes of a C test mating (m/+ male x m/m hermaphrodite) should survive. However, if rescue depends on a function or cytoplasmic component from the male sperm, then all the cross progeny zygotes in a C test should survive. Of the 10 M,N mutants, 6 have been C tested; one exhibited paternal rescue independent of the + allele. The A and B tests also were carried out on 16 mutants that arrest before the L3 molt (acc mutants). In the A test on 2 of these mutants, all m/m progeny of m/+ parents grew to adulthood at 25 C. Therefore, parental contributions are sufficient to overcome a progeny mutational block as late as the L2 stage. All 16 acc mutants scored N in the B test.
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[
Worm Breeder's Gazette,
1994]
cej-1 Encodes a Novel Protein with Poly-Threonine Motif M. L. A. Khanl, M. Tabish, T. Fukushigel1 S. Tsukita2, M. Itoh , Sh. Tsukita , and S. S. Siddiqui. (1): Lab. of Molecular Biology, Dept of Ecological Engg. Toyohashi Univ. Technology, Toyohashi 441, and (2). National Institute for Physiological Sciences, Okazaki 444, Japan.