Chou JH et al. (1996) West Coast Worm Meeting "MOLECULAR ANALYSIS OF A PUTATIVE OLFACTORY RECEPTOR IN C. ELEGANS"

Bargmann CI, Chou JH, Sengupta P

[West Coast Worm Meeting, 1996]

The olfactory system is remarkable in its ability to couple broad sensitivity with high specificity. A long-standing question has been the nature of the molecular receptors that mediate this response. Although olfactory receptors have been identified in vertebrates, functional data linking receptors with physiological ligands has been lacking. Using C. elegans as a model system, we have identified a potential olfactory receptor with a candidate ligand. Using a behavioral screen, Piali Sengupta identified a mutant, odr-10(ky32), whose sole defect was an inability to respond to the volatile odorant diacetyl. Cloning odr-10 revealed that it belongs to the seven transmembrane domain superfamily of G-protein coupled receptors, with distant homology to rat olfactory receptors. odr-10 was expressed exclusively in AWA, the single chemosensory neuron required for diacetyl response. These findings implied that odr-10 might be the diacetyl receptor (Sengupta et al., Cell (1996) 84: 899-909). odr-10(ky32) is due to a missense mutation. Might the missense mutation affect only the diacetyl recognition site of a receptor that senses multiple compounds? Using the Tc1 insertion / imprecise excision strategy, a null mutant was identified in which a large part of the odr-10 gene was deleted. The null phenotype was also restricted to diacetyl, with responses to all other odorants normal. Thus, odr-10 is specifically required for diacetyl chemosensation. I am using this putative olfactory receptor and its candidate ligand to analyze olfactory function in vivo and possibly in vitro. Treatment with high concentrations of one odorant can abolish response to that odorant without affecting responses to other odorants -- how might this adaptation be mediated? What specifies the dose-response sensitivity of a receptor? What are the downstream effectors of the receptor? To address these questions, I am expressing both wild-type and modified forms of the odr-10 gene in C. elegans and in vertebrate cells.

Chou JH et al. (2001) Genetics "The Caenorhabditis elegans odr-2 gene encodes a novel Ly-6-related protein required for olfaction."

Sengupta P, Chou JH, Bargmann CI

[Genetics, 2001]

Caenorhabditis elegans odr-2 mutants are defective in the ability to chemotax to odorants that are recognized by the two AWC olfactory neurons. Like many other olfactory mutants, they retain responses to high concentrations of AWC-sensed odors; we show here that these residual responses are caused by the ability of other olfactory neurons (the AWA neurons) to be recruited at high odor concentrations. odr-2 encodes a membrane-associated protein related to the Ly-6 superfamily of GPI-linked signaling proteins and is the founding member of a C. elegans gene family with at least seven other members. Alternative splicing of odr-2 yields three predicted proteins that differ only at the extreme amino terminus. The three isoforms have different promoters, and one isoform may have a unique role in olfaction. An epitope-tagged ODR-2 protein is expressed at high levels in sensory neurons, motor neurons, and interneurons and is enriched in axons. The AWC neurons are superficially normal in their development and structure in odr-2 mutants, but their function is impaired. Our results suggest that ODR-2 may regulate AWC signaling within the neuronal network required for chemotaxis.

Chou JH et al. (1996) Cold Spring Harb Symp Quant Biol "Olfactory recognition and discrimination in Caenorhabditis elegans."

Troemel ER, Chou JH, Colbert HA, Tong L, Crump GC, Bargmann CI, Roayaie K, Tobin DM, Dwyer ND, Sengupta P

[Cold Spring Harb Symp Quant Biol, 1996]

An animal generates appropriate behavioral responses to a stimulus based on the intrinsic qualities of the stimulus, the context in which it appears, and the animal's previous experience. Olfactory stimuli elicit responses that are often reproducible across different individuals in a species: Many animals display characteristic behaviors in response to the smell of members of their species, food sources, or dangerous conditions. Other sensory modalities can also evoke innate responses, but in the olfactory system, odorants that elicit distinct behaviors are differentiated at the first step of sensory detection by the olfactory receptor neurons. Therefore, the neuronal circuitry responsible for different behaviors can be traced starting from the initial sensory events. Our studies have focused on olfaction and chemosensation in the nematode Caenorhabditis elegans. Chemosensation is the richest mechanism C. elegans has for interacting with its environment, both in the number of different stimuli that are recognized and in the variety of different responses that can be elicited. Virtually all behaviors in C. elegans are modulated by chemical cues. Individual molecules can be attractants or repellents, or they can regulate egg-laying, feeding, or movement. In addition, pheromone cues control development of the animal and mating behavior between males and hermaphrodites. How are these chemical cues recognized and discriminated from one another? The answer to this question lies partly in the biochemical mechanisms that recognize individual odorants, and partly in the neuronal circuitry that drives particular

Chou JH et al. (1995) International C. elegans Meeting "odr-2, a gene required for chemotaxis, may be structurally similar to the Ly-6 superfamily CD59, and snake neurotoxins"

Chou JH, Sengupta P, Bargmann CI

[International C. elegans Meeting, 1995]

C. elegans responds to volatile compounds in a process analogous to olfaction. Mutations in odr-2 result in defective chemotaxis towards a subset of odorants sensed by the AWC olfactory neurons. odr-2 mutants are also defective in octanol avoidance, which requires the AWB and ADL neurons. However, chemotaxis to other volatile and water-soluble attractants and avoidance of high osmotic strength are normal, as are coordinated movement, dauer formation, mating, mechanosensation, egg-laying, and feeding.

Hansen EL et al. (1971) Experientia "Effect of insect hormones on nematodes in axenic culture."

Hansen EL, Buecher EJ

[Experientia, 1971]

Insect juvenile hormones (JH) or JH mimetics have been shown to affect development of nematodes: Trichinella spiralis larvae and fourth stage Phocanema decipiens were inhibited, and abnormal morphology was seen in Heterodera schactii. The effects of insect hormones and analogues on development of several free-living and parasitic nematodes cultured axenically are described in the present paper.

Sengupta P et al. (1996) Cell "odr-10 encodes a seven transmembrane domain olfactory receptor required for responses to the odorant diacetyl."

Chou JH, Sengupta P, Bargmann CI

[Cell, 1996]

Olfactory signaling is initiated by interactions between odorants and olfactory receptors. We show that the C. elegans odr-10 gene is likely to encode a receptor for the odorant diacetyl. odr-10 mutants have a specific defect in chemotaxis to diacetyl, one of several odorants detected by the AWA olfactory neurons. odr-10 encodes a predicted seven transmembrane domain receptor; a green fluorescent protein-tagged Odr-10 protein is localized to the AWA sensory cilia. odr-10 expression is regulated by odr-7, a transcription factor implicated in AWA sensory specification. Expression of odr-10 from a heterologous promoter directs behavioral responses to diacetyl, but not to another odorant detected by the AWA neurons. These results provide functional evidence for a specific interaction between an olfactory receptor protein and its odorant ligand.

Sim C et al. (2013) Front Physiol "Insulin signaling and the regulation of insect diapause."

Denlinger DL, Sim C

[Front Physiol, 2013]

A rich chapter in the history of insect endocrinology has focused on hormonal control of diapause, especially the major roles played by juvenile hormones (JHs), ecdysteroids, and the neuropeptides that govern JH and ecdysteroid synthesis. More recently, experiments with adult diapause in Drosophila melanogaster and the mosquito Culex pipiens, and pupal diapause in the flesh fly Sarcophaga crassipalpis provide strong evidence that insulin signaling is also an important component of the regulatory pathway leading to the diapause phenotype. Insects produce many different insulin-like peptides (ILPs), and not all are involved in the diapause response; ILP-1 appears to be the one most closely linked to diapause in C. pipiens. Many steps in the pathway leading from perception of daylength (the primary environmental cue used to program diapause) to generation of the diapause phenotype remain unknown, but the role for insulin signaling in mosquito diapause appears to be upstream of JH, as evidenced by the fact that application of exogenous JH can rescue the effects of knocking down expression of ILP-1 or the Insulin Receptor. Fat accumulation, enhancement of stress tolerance, and other features of the diapause phenotype are likely linked to the insulin pathway through the action of a key transcription factor, FOXO. This review highlights many parallels for the role of insulin signaling as a regulator in insect diapause and dauer formation in the nematode Caenorhabditis elegans.

Fodor A et al. (1989) General & Comparative Endocrinology "Effects of precocene analogs on the nematode Caenorhabditis remanei (var. Bangaloreiensis). 2. Competitions with a juvenile hormone analog (methoprene)."

Timar T, Fodor A

[General & Comparative Endocrinology, 1989]

Fourteen 7-alkoxy-2,2-dimethylchromenes were synthetized and studied in JH competition experiments: prococenes (Ps) PI and PII, and synthetic analogs (PAs) including (i) three with both antiallatal and P-like activities: 7-ethoxy-PII (7-EPII); 7-(prop-2-ynyloxy)-2,2-dimethylchromene (PPI); and 6-methoxy-7-(prop-2-yynyloxy)-2,2-dimethylchromene (PPIII); (ii) six without antiallatal activity, exerting P-like activity in nematodes; and (iii) three without either antiallatal or P-like activity, but with a strong nematocidal effect. Within the dose range 8-1000 ug/ml, different concentrations of each PA were applied to nematode growth medium which did or did not contain 1000 ug methoprene (a juvenile hormone analog JHA)/ml. Plates inoculated with Caenorhabditis embryos were incubated and scored for developmentally affected survivors. The JHA did not compete with any PA mentioned as (iii). It competed moderately with some nonantiallatal PAs (8-Me-PPI, 8-MeO-PPI, and 3,4-diCl-PPI) with strong P-like and nematocidal activities. The JHA competed most efficiently with all Ps, antiallatal PAs, and two nonantiallatal PAs (PPII and thio-PI) which exerted severe P-like activities in nematodes. Parameters assumed to be indicators of the P-like (rather than nematocidal) activity of the PAs proved more sensitive to the JHA than those of nematocidal activity. Whether the JH-compensable P-like activity of some PAs can be regarded as a real anti-JH action needs further clarification.

Landis GN et al. (2020) J Gerontol A Biol Sci Med Sci "Metabolic Signatures of Life Span Regulated by Mating, Sex Peptide and Mifepristone/RU486 in Female Drosophila melanogaster."

Abdelmesieh M, Patel P, Wang T, Tower J, Wang L, Fan Y, Promislow DEL, Doherty DV, Lee S, Vroegop J, Wu J, Shen J, Landis GN, Yen CA, Wang I, Curran SP

[J Gerontol A Biol Sci Med Sci, 2020]

Mating and transfer of male Sex Peptide (SP), or transgenic expression of SP, causes inflammation and decreased life span in female Drosophila. Mifepristone rescues these effects, yielding dramatic increases in life span. Here targeted metabolomics data were integrated with further analysis of extant transcriptomic data. Each of seven genes positively correlated with life span were expressed in the brain or eye, and involved regulation of gene expression and signaling. Genes negatively correlated with life span were preferentially expressed in midgut and involved protein degradation, amino acid metabolism, and immune response. Across all conditions, life span was positively correlated with muscle breakdown product 1/3-methylhistadine and purine breakdown product urate, and negatively correlated with tryptophan breakdown product kynurenic acid, suggesting a SP-induced shift from somatic maintenance/turnover pathways to the costly production of energy and lipids from dietary amino acids. Some limited overlap was observed between genes regulated by mifepristone and genes known to be regulated by ecdysone, however, mifepristone was unable to compete with ecdysone for activation of an ecdysone-responsive transgenic reporter. In contrast, genes regulated by mifepristone were highly enriched for genes regulated by Juvenile Hormone (JH), and mifepristone rescued the negative effect of JH analog methoprene on life span in adult virgin females. The data indicate that mifepristone increases life span and decreases inflammation in mated females by antagonizing JH signaling downstream of male SP. Finally, mifepristone increased life span of mated, but not unmated, C. elegans, in two of three trials, suggesting possible evolutionary conservation of mifepristone mechanisms.

Fodor A et al. (1987) Worm Breeder's Gazette "competition of exogenous methoprene and precocenes in nematodes: the end of the story."

Timar T, Hosztafi S, Dinya Z, Fodor A, Kiss I

[Worm Breeder's Gazette, 1987]

We have accomplished a ten year long project aimed to learn whether competition between the juvenile hormone (JH) analogue methoprene (JHA) and precocenes (P's) (chromene derivatives capable to destruct the JH producing organ (CA) in sensitive insect species tissue specifically) in C. elegans (Fodor, et. al., Gen. Comp. Endcr. 46: p. 99 (1982)) can or cannot be explained by a comparable 'anti-JH' action of P's in nematodes. Neither JH or CA like organ has been discovered in nematodes so far. There are only a few indirect data showing that insect juvenile hormones may influence certain nematodes pathogenizing insects. We adopted a 'structure/activity' approach including design, synthesis and test P analogues on nematodes in the presence and absence of JHA. If (at least part of) those analogues which capable to destruct the CA of a sensitive insect (Locusta migratoria) were also effective in nematodes and their effect could be compensated by JHA exogenously, then this hormone (analogue) should play a physiological role in the P-poisoned nematodes. If those P's could be competed by JHA, which proved effective (as 'anti-JH' compounds) in insects, but those which exerted only aspecific toxicity could not be, then it would be logical to suggest, that P's are the same kind of 'suicide compounds' for nematodes as for insects. More than 200 P derivatives were synthesized (Tim r, Hosztafi) and tested on C. elegans (Fodor) and L. migratoria (Kiss). After a detailed quantitative structure/activity relation (QSAR) analysis ( Dinya, et. al., QSAR Strat. Des. Bioact. Compd. Proc. Eur. Symp. Struct.-Act. Relat. 5th (1984) Publ. 1985) several new P analogue were designed, synthesized and tested on L. migratoria and on C. remanei var. Bangaloriensis. (We choose this nematode strain because half of its population consists of males, therefore it is easy to distinguish male adultoids from other type of retarded worms.) Altogether, 121 molecules were retested C. remanei and 17 of them was found to exert some significant biological effect. These compounds were retested again several times both in the absence and in the presence of 1 mg/ml NGM dose of JHA: altogether, more that 144,000 C. remanei embryos were counted, treated and scored afterwards. The tests on nematodes were carried out as described in our attached paper. The most characteristic data concerning precocene activity in nematodes were the following: (1) LC50: the half lethal dose (in g/ml) at which half of the embryos develops to worms (calculated by probit analysis); (2) AD50: the dose ( g/ml) at which half of the embryos develops to normal adults; (3) EC50: the dose ( g/ml) at which half of the nematodes on the plates found as 'normal' fertile adults; (4) The maximum frequency of 'adultoid mini worms' during the experiments. [See Figures 1- 2] The main conclusions are the following: About structure/activity relations: (1) All the three (P1-P3) precocene is effective in nematodes and their effects can be compensated by exogenous JHA. (2) The longer the chain of the R7 substituent the less the effect of the compounds in nematodes. (3) The 7-proparglyoxy analogues are much more effective in nematodes than any other C7 substituted compound. (compare P1 to TT51; P2 to K460; P3 to TT80; TT56 to TT58 or 3,4-diCl-P1 (inactive) to FI121.) (4) The asymmetrically disubstituted analogues are much more effective than the symmetrically disubstituted ones (compare TT80 to K460). It is true, if R7 is longer than R6. (5) Me substitution at C5 position inactivates the originally potent P's (compare TT58 to TT51) but restore the activity of originally inactive (for instance, 7-sBuO-P1) analogues (compare it to TT56). 8-MeO substitution eliminate specific P activity (compare TT51 to K464). (6) Both 8-Me and 8-MeO substitution increase toxic rather than JH compatible biological activity of P's. 8-MeO analogues are more toxic than 8-Me ones, but the consequences of the action of 8-MeO compounds in nematodes can be cured more efficiently by JHA than those concerning 8-Me compounds (compare TT100 to K475). About JHA competition experiments: JHA competed the effects of all precocenes which effected both insects and nematodes. However, the data concerning K354 and FI121 show, that there are analogues which effective only in nematodes and their effects can also be cured by exogenous JHA. Although there are aspecifically toxic analogues (like K454 or 2,3,5-triMe-7 propargO-P1) which cannot be compensated by methoprene, we cannot conclude, that our data unambiguously support the idea of existence JH-like hormones in nematodes. It seems very probable, however, that JH-like compounds can interfere with the lethal metabolism of P's.