The C. elegans lethal gut-obstructed gob-1 gene is trehalose-6-phosphate phosphatase

Modeling, virtual screening, and enzymatic docking of trehalose 6-phosphate phosphatase and evaluation of the insecticidal effect of phthalimide, N-(p-tolylsulfonyl) on Aedes aegypti (Diptera: Culicidae)

BACKGROUND

Aedes aegypti Linnaeus is a medically important vector because of its role in transmitting several arboviruses. Trehalose-6-phosphate phosphatase (TPP), an enzyme from the trehalose pathway, was the focus of this study, which aimed to model it, perform molecular docking and select potential ligands to evaluate their larvicidal and adulticidal activity on the mosquito.

RESULTS

Because no TPP structure for A. aegypti was described, the modeling was done by homology, using the TPP from Mycobacterium tuberculosis Zopf as a template, with 31% similarity. Following virtual screening, a search for TPP-like molecules on PubChem resulted in 227 molecules, and phthalimide, N-(p-tolylsulfonyl) (PNT) was selected and tested in vivo. Larvicidal tests were conducted in 24-well plates, and adulticidal tests used sugar baits with several concentrations (5 to 100 ppm) of PNT. In larval tests, mortality ranged from 38% to 52% at 24 h and reached 92% at 100 ppm PNT after 72 h. Larval mortality progressively increased over 96 h, with estimated lethal concentration (LC50 and LC90) values after 48 h of 18 and 198 ppm respectively. In adulticidal tests, despite high bait uptake, acute ingestion of PNT did not cause mortality in adult mosquitoes.

CONCLUSION

PNT demonstrated larvicidal activity against A. aegypti, suggesting that mosquito TPP could be a target in the search for new-generation insecticides. © 2025 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

A functional study of the trehalase genes in Tribolium castaneum and their application in the construction of RNAi engineering bacteria

Tribolium castaneum, belonging to the order Coleoptera, family Tenebrionidae, is a global grain storage pest. The enzyme trehalase can catalyze trehalose decomposition and participate in chitin synthesis, which is of great significance in insect physiology and may be a key target for T. castaneum pest prevention and control. This study focused on T. castaneum and explored the function of its trehalase (TcTre) in test insects' growth and development process. We analyzed the roles of TcTre in different growth stages and tissues of T. castaneum by measuring its spatio and temporal expression patterns. The silencing of TcTre by RNAi technology reduced the transcription level of the target gene, affected the enzyme activity of trehalase, disturbed the sugar balance, blocked the pathway of chitin synthesis, and caused abnormal molting and wing development of the tested insects. Key genes about pest control such as TcTre1-1, TcTre1-3, and TcTre2 were screened, which caused the accumulated mortality of 53.33 %, 56.67 %, and 50.00 % respectively. Subsequently, an engineered bacterium, Tre-L4440-HT115 (DE3), was developed to efficiently express dsRNA and mediate insecticidal activity. The dsRNA produced by the bacterial solution, targeting TcTre1-1, TcTre1-3, and TcTre2 fragments for silencing, could cause the death of 44.44 %, 48.89 %, and 46.67 % of the test insects cumulatively. This advancement was aimed at reducing the production costs of dsRNA and laying a scientific foundation for the industrial development of nucleic acid pesticides for T. castaneum.

Enzymes involved in trehalose-chitin synthesis in Haemonchus contortus could be vaccine candidates for goats

BACKGROUND

Trehalose-6-phosphate synthase (HcTPS) and trehalose-6-phosphate phosphatase (HcGOB) are key enzymes for trehalose synthesis in Haemonchus contortus. In addition, previous studies have also demonstrated that HcTPS and HcGOB can regulate the function of host immune cells in vitro, and are important immunosuppressive molecules. Therefore, this study evaluated the potential of HcTPS and HcGOB as vaccine candidates through in vitro and in vivo experiments.

METHODS

To evaluate the inhibitory effects of polyclonal antibodies on egg hatching and larval development, anti-rHcTPS and anti-rHcGOB antibodies were incubated separately with eggs and first-stage larvae (L1s) under controlled in vitro conditions. For immunization studies, recombinant proteins (rHcTPS and rHcGOB) were formulated with Quil-A adjuvant, and administered to goats through subcutaneous injection. Vaccine efficacy against Haemonchus contortus infection was determined through comprehensive analysis of multiple parasitological parameters, including: (1) egg abnormality rate, (2) hatching success rate, (3) reduction egg output rates, and (4) reduction in adult worm burden.

RESULTS

The results of in vitro experiments showed that polyclonal antibodies against HcTPS and HcGOB had no effect on the hatching rate of eggs, but significantly affected the development from L1s to infectious third stage larvae (L3s). After immunization with recombinant HcTPS protein (rHcTPS) and recombinant HcGOB protein (rHcGOB), high levels of antigen-specific immunoglobulin G (IgG) were produced in goats, and remained till the end of the experiment. Compared with the Quil-A adjuvant control group, the number of deformed eggs in the rHcTPS protein- immunized group and the rHcGOB protein- immunized group were significantly increased. In the rHcTPS protein-immunized group and the rHcGOB protein-immunized group, the deformity rate of eggs was 9.59% and 17.30%, respectively, and the hatching rate of eggs was reduced by 11.27% and 13.71%, respectively. Moreover, compared with the Quil-A adjuvant control group, the number of eggs and adults in the HcTPS protein- immunized group decreased by 64.47% and 60.93%, respectively, and the number of eggs and adults in the rHcGOB protein- immunized group decreased by 63.97% and 69.54%, respectively. Furthermore, compared with the control group (Quil-A adjuvant), the trehalose content in the rHcTPS protein- immunized group and the rHcGOB protein- immunized group was also significantly reduced.

CONCLUSIONS

These findings indicate that rHcTPS and rHcGOB exhibit superior immune protective effects, rendering them promising candidates for vaccine development.

Elemental exchange: Bioisosteric replacement of phosphorus by boron in drug design

Continuous efforts are being directed toward the employment of boron in drug design due to its advantages and unique characteristics including a plethora of target engagement modes, lower metabolism, and synthetic accessibility, among others. Phosphates are components of multiple drug molecules as well as clinical candidates, since they play a vital role in various biochemical functions, being components of nucleotides, energy currency- ATP as well as several enzyme cofactors. This review discusses the unique chemistry of boron functionalities as phosphate bioisosteres - "the boron-phosphorus elemental exchange strategy" as well as the superiority of boron groups over other commonly employed phosphate bioisosteres. Boron phosphate-mimetics have been utilized for the development of enzyme inhibitors as well as novel borononucleotides. Both the boron functionalities described in this review-boronic acids and benzoxaboroles-contain a boron connected to two oxygens and one carbon atom. The boron atom of these functional groups coordinates with a water molecule in the enzyme site forming a tetrahedral molecule which mimics the phosphate structure. Although boron phosphate-mimetic molecules - FDA-approved Crisaborole and phase II/III clinical candidate Acoziborole are products of the boron-phosphorus bioisosteric elemental exchange strategy, this technique is still in its infancy. The review aims to promote the use of this strategy in future medicinal chemistry projects.

Cystidicola farionis, a Swim Bladder Parasite of European Smelt: Characterization of the Nematode Trehalose Strategy

The molecular identification of Cystidicola farionis (a swim bladder nematode of European smelt from the Vistula Lagoon in Poland) was performed. Their prevalence level was determined, and changes in the trehalose synthesis pathway in larvae and adult nematodes were demonstrated. The trehalose level was almost four times higher in adult nematodes than in larvae. In contrast, the activity of both enzymes (trehalose 6-phosphate synthase, TPS and trehalose 6-phosphate phosphatase, TPP) involved in the synthesis of trehalose was higher in larvae than in adults under optimal conditions. The optimum pH for TPS isolated from larvae and adults was pH 7.0. The optimum pH for TPP from larvae and adults was pH 7.0 and pH 8.0, respectively. The optimal temperature was 20 °C, and Mg2+ ions were an activator for trehalose-synthetizing enzymes from both sources. Enzymes isolated from adult nematodes were less susceptible to divalent ion chelator and inorganic phosphate than larval enzymes. The dynamic transformation of trehalose in the nematode developing inside the swim bladder of the smelt appears to be an important metabolic pathway in the nematode survival strategy. These studies are aimed at a better understanding of the issue of the metabolic adaptation of parasites, which, in the future, may indirectly contribute to the elimination of the parasite from aquacultures, which will impact public health.

In vitro characterization of Haemonchus contortus trehalose-6-phosphate phosphatase and its immunomodulatory effects on peripheral blood mononuclear cells (PBMCs)

Background

Trehalose-6-phosphate phosphatase (TPP6) is a key enzyme in the trehalose biosynthesis pathway. The accumulation of TPP6 inside the body is harmful to the pathogen, but almost nothing is currently known about the function of TPP6 from Haemonchus contortus (CRE-GOB-1).

Methods

The H. contortus CRE-GOB-1 (HcGOB) gene was cloned and recombinant protein of GOB (rHcGOB) was expressed; transcription of the HcGOB gene at different developmental stages of H. contortus was then studied. The spatial expression pattern of the HcGOB gene in adult female and male worms was determined by both quantitative real-time PCR (qPCR) and immunofluorescence. The binding of the rHcGOB protein to goat PBMCs was assessed by immunofluorescence assay. The immunomodulatory impacts of rHcGOB on cell proliferation, nitric oxide generation and cytokine secretion were assessed by co-culture of rHcGOB protein with goat PBMCs.

Results

The HcGOB protein was transcribed in eggs, infective third-stage larvae (iL3s) and adults of H. contortus, with the highest transcript levels found in the egg stage. The transcript levels were significantly elevated in iL3s after manual desheathing. HcGOB was widely distributed in adult worms where it was mainly localized in the gut and gonads. rHcGOB was observed to bind to PBMCs and also to be recognized by sera collected from a goat infected with H. contortus. rHcGOB significantly activated the interleukin-10/transforming growth factor β/signal transducer and activator of transcription 3 (IL-10/TGF-β/STAT3) pathway in PBMCs while suppressing the transcription and expression of IL-4 and IL-17.

Conclusions

These results suggest that the HcGOB gene plays an important role in the development, parasitism and reproduction of H. contortus. The rHcGOB protein affected the immunomodulatory function of PBMCs in the in vitro study, suggesting that this protein would be a promising vaccine target.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-05115-4.

Gene-based mapping of trehalose biosynthetic pathway genes reveals association with source- and sink-related yield traits in a spring wheat panel

Trehalose 6‐phosphate (T6P) signalling regulates carbon use and allocation and is a target to improve crop yields. However, the specific contributions of trehalose phosphate synthase (TPS) and trehalose phosphate phosphatase (TPP) genes to source‐ and sink‐related traits remain largely unknown. We used enrichment capture sequencing on TPS and TPP genes to estimate and partition the genetic variation of yield‐related traits in a spring wheat (Triticum aestivum) breeding panel specifically built to capture the diversity across the 75,000 CIMMYT wheat cultivar collection. Twelve phenotypes were correlated to variation in TPS and TPP genes including plant height and biomass (source), spikelets per spike, spike growth and grain filling traits (sink) which showed indications of both positive and negative gene selection. Individual genes explained proportions of heritability for biomass and grain‐related traits. Three TPS1 homologues were particularly significant for trait variation. Epistatic interactions were found within and between the TPS and TPP gene families for both plant height and grain‐related traits. Gene‐based prediction improved predictive ability for grain weight when gene effects were combined with the whole‐genome markers. Our study has generated a wealth of information on natural variation of TPS and TPP genes related to yield potential which confirms the role for T6P in resource allocation and in affecting traits such as grain number and size confirming other studies which now opens up the possibility of harnessing natural genetic variation more widely to better understand the contribution of native genes to yield traits for incorporation into breeding programmes.

Sugar-Phosphate Toxicities

Accumulation of phosphorylated intermediates during cellular metabolism can have wide-ranging toxic effects on many organisms, including humans and the pathogens that infect them. These toxicities can be induced by feeding an upstream metabolite (a sugar, for instance) while simultaneously blocking the appropriate metabolic pathway with either a mutation or an enzyme inhibitor. Here, we survey the toxicities that can arise in the metabolism of glucose, galactose, fructose, fructose-asparagine, glycerol, trehalose, maltose, mannose, mannitol, arabinose, and rhamnose. Select enzymes in these metabolic pathways may serve as novel therapeutic targets. Some are conserved broadly among prokaryotes and eukaryotes (e.g., glucose and galactose) and are therefore unlikely to be viable drug targets. However, others are found only in bacteria (e.g., fructose-asparagine, rhamnose, and arabinose), and one is found in fungi but not in humans (trehalose). We discuss what is known about the mechanisms of toxicity and how resistance is achieved in order to identify the prospects and challenges associated with targeted exploitation of these pervasive metabolic vulnerabilities.

Effects of High Dietary Carbohydrate and Lipid Intake on the Lifespan of C. elegans

Health and lifespan are influenced by dietary nutrients, whose balance is dependent on the supply or demand of each organism. Many studies have shown that an increased carbohydrate–lipid intake plays a critical role in metabolic dysregulation, which impacts longevity. Caenorhabditis elegans has been successfully used as an in vivo model to study the effects of several factors, such as genetic, environmental, diet, and lifestyle factors, on the molecular mechanisms that have been linked to healthspan, lifespan, and the aging process. There is evidence showing the causative effects of high glucose on lifespan in different diabetic models; however, the precise biological mechanisms affected by dietary nutrients, specifically carbohydrates and lipids, as well as their links with lifespan and longevity, remain unknown. Here, we provide an overview of the deleterious effects caused by high-carbohydrate and high-lipid diets, as well as the molecular signals that affect the lifespan of C. elegans; thus, understanding the detailed molecular mechanisms of high-glucose- and lipid-induced changes in whole organisms would allow the targeting of key regulatory factors to ameliorate metabolic disorders and age-related diseases.

Parallel evolution of trehalose production machinery in anhydrobiotic animals via recurrent gene loss and horizontal transfer

Trehalose is a versatile non-reducing sugar. In some animal groups possessing its intrinsic production machinery, it is used as a potent protectant against environmental stresses, as well as blood sugar. However, the trehalose biosynthesis genes remain unidentified in the large majority of metazoan phyla, including vertebrates. To uncover the evolutionary history of trehalose production machinery in metazoans, we scrutinized the available genome resources and identified bifunctional trehalose-6-phosphate synthase-trehalose-6-phosphate phosphatase (TPS–TPP) genes in various taxa. The scan included our newly sequenced genome assembly of a desiccation-tolerant tardigrade Paramacrobiotus sp. TYO, revealing that this species retains TPS–TPP genes activated upon desiccation. Phylogenetic analyses identified a monophyletic group of the many of the metazoan TPS–TPP genes, namely ‘pan-metazoan’ genes, that were acquired in the early ancestors of metazoans. Furthermore, coordination of our results with the previous horizontal gene transfer studies illuminated that the two tardigrade lineages, nematodes and bdelloid rotifers, all of which include desiccation-tolerant species, independently acquired the TPS–TPP homologues via horizontal transfer accompanied with loss of the ‘pan-metazoan’ genes. Our results indicate that the parallel evolution of trehalose synthesis via recurrent loss and horizontal transfer of the biosynthesis genes resulted in the acquisition and/or augmentation of anhydrobiotic lives in animals.

Trehalose in pine wood nematode participates in DJ3 formation and confers resistance to low-temperature stress

Background

Recently, pine wood nematode (PWN, Bursaphelenchus xylophilus) has been found in the extreme cold area of northeast China. The third-stage dispersal juvenile (DJ3) of PWN, which is a long-lived stress-resistant stage, plays an important role in the process of PWN spreading to low-temperature areas, as this stage can survive under unfavorable conditions.

Results

Weighted correlation network analysis (WGCNA) was used to analyze the expression patterns of 15,889 genes included in 21 RNA-Seq results of PWN at DJ3 and the other 6 different stages, and a total of 12 coexpression modules were obtained. Among them, the magenta module has the highest correlation with DJ3, which included a total of 652 genes. KEGG enrichment analysis showed that most of the genes in the magenta module were involved in metabolic processes, which were related to autophagy and longevity regulation. These pathways included starch and sucrose metabolism, which contains trehalose metabolism. To explore the function of trehalose in DJ3 formation and survival under − 20 °C, a trehalose-6-phosphate synthase encoding gene (Bx-tps), a trehalose-6-phosphate phosphatase encoding gene (Bx-tpp) and 7 trehalase encoding genes (Bx-tres) were identified and investigated. The expression of these 9 genes was related to the formation of DJ3. A treatment under − 20 °C induced the accumulation of trehalose. The survival rate of DJ3 at -20 °C reduced after silencing of any of these trehalose metabolism genes. Further analysis suggested that two trehalose synthesis genes were highly correlated with DJ3 and might be involved in autophagy by regulating with energy conversion related genes.

Conclusions

The above results indicated that trehalose metabolism promotes DJ3 formation and helps DJ3 survive at -20 °C. Although trehalose accumulation is favorable for DJ3 to cope with low-temperature stress, multiple trehalose metabolism genes need to work together. There may be a multi-path regulated physiological process involving trehalose synthesis genes under low-temperature stress resistance. This physiological process may regulate the formation and maintenance of DJ3 through autophagy and energy conversion.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-07839-0.

Regulation of shoot branching in arabidopsis by trehalose 6-phosphate

Trehalose 6-phosphate (Tre6P) is a sucrose signalling metabolite that has been implicated in regulation of shoot branching, but its precise role is not understood. We expressed tagged forms of TREHALOSE-6-PHOSPHATE SYNTHASE1 (TPS1) to determine where Tre6P is synthesized in arabidopsis (Arabidopsis thaliana), and investigated the impact of localized changes in Tre6P levels, in axillary buds or vascular tissues, on shoot branching in wild-type and branching mutant backgrounds. TPS1 is expressed in axillary buds and the subtending vasculature, as well as in the leaf and stem vasculature. Expression of a heterologous Tre6P phosphatase (TPP) to lower Tre6P in axillary buds strongly delayed bud outgrowth in long days and inhibited branching in short days. TPP expression in the vasculature also delayed lateral bud outgrowth and decreased branching. Increased Tre6P in the vasculature enhanced branching and was accompanied by higher expression of FLOWERING LOCUS T (FT) and upregulation of sucrose transporters. Increased vascular Tre6P levels enhanced branching in branched1 but not in ft mutant backgrounds. These results provide direct genetic evidence of a local role for Tre6P in regulation of axillary bud outgrowth within the buds themselves, and also connect Tre6P with systemic regulation of shoot branching via FT.

Evolution of Developmental GATA Factors in Nematodes

GATA transcription factors are found in animals, plants, and fungi. In animals, they have important developmental roles in controlling specification of cell identities and executing tissue-specific differentiation. The Phylum Nematoda is a diverse group of vermiform animals that inhabit ecological niches all over the world. Both free-living and parasitic species are known, including those that cause human infectious disease. To date, GATA factors in nematodes have been studied almost exclusively in the model system C. elegans and its close relatives. In this study, we use newly available sequences to identify GATA factors across the nematode phylum. We find that most species have fewer than six GATA factors, but some species have 10 or more. Comparisons of gene and protein structure suggest that there were at most two GATA factors at the base of the phylum, which expanded by duplication and modification to result in a core set of four factors. The high degree of structural similarity with the corresponding orthologues in C. elegans suggests that the nematode GATA factors share similar functions in development.

Mechanisms of Desiccation Tolerance: Themes and Variations in Brine Shrimp, Roundworms, and Tardigrades

Water is critical for the survival of most cells and organisms. Remarkably, a small number of multicellular animals are able to survive nearly complete drying. The phenomenon of anhydrobiosis, or life without water, has been of interest to researchers for over 300 years. In this review we discuss advances in our understanding of protectants and mechanisms of desiccation tolerance that have emerged from research in three anhydrobiotic invertebrates: brine shrimp (Artemia), roundworms (nematodes), and tardigrades (water bears). Discovery of molecular protectants that allow each of these three animals to survive drying diversifies our understanding of desiccation tolerance, and convergent themes suggest mechanisms that may offer a general model for engineering desiccation tolerance in other contexts.

Structural Analysis of Binding Determinants of Salmonella typhimurium Trehalose-6-phosphate Phosphatase Using Ground-State Complexes

Trehalose-6-phosphate phosphatase (T6PP) catalyzes the dephosphorylation of trehalose 6-phosphate (T6P) to the disaccharide trehalose. The enzyme is not present in mammals but is essential to the viability of multiple lower organisms as trehalose is a critical metabolite, and T6P accumulation is toxic. Hence, T6PP is a target for therapeutics of human pathologies caused by bacteria, fungi, and parasitic nematodes. Here, we report the X-ray crystal structures of Salmonella typhimurium T6PP (StT6PP) in its apo form and in complex with the cofactor Mg²⁺ and the substrate analogue trehalose 6-sulfate (T6S), the product trehalose, or the competitive inhibitor 4-n-octylphenyl α-d-glucopyranoside 6-sulfate (OGS). OGS replaces the substrate phosphoryl group with a sulfate group and the glucosyl ring distal to the sulfate group with an octylphenyl moiety. The structures of these substrate-analogue and product complexes with T6PP show that specificity is conferred via hydrogen bonds to the glucosyl group proximal to the phosphoryl moiety through Glu123, Lys125, and Glu167, conserved in T6PPs from multiple species. The structure of the first-generation inhibitor OGS shows that it retains the substrate-binding interactions observed for the sulfate group and the proximal glucosyl ring. The OGS octylphenyl moiety binds in a unique manner, indicating that this subsite can tolerate various chemotypes. Together, these findings show that these conserved interactions at the proximal glucosyl ring binding site could provide the basis for the development of broad-spectrum therapeutics, whereas variable interactions at the divergent distal subsite could present an opportunity for the design of potent organism-specific therapeutics.

Trehalose-6-phosphate-mediated phenotypic change in Acinetobacter baumannii

The stress protectant trehalose is synthesized in Acinetobacter baumannii from UPD-glucose and glucose-6-phosphase via the OtsA/OtsB pathway. Previous studies proved that deletion of otsB led to a decreased virulence, the inability to grow at 45°C and a slight reduction of growth at high salinities indicating that trehalose is the cause of these phenotypes. We have questioned this conclusion by producing ∆otsA and ∆otsBA mutants and studying their phenotypes. Only deletion of otsB, but not deletion of otsA or otsBA, led to growth impairments at high salt and high temperature. The intracellular concentrations of trehalose and trehalose-6-phosphate were measured by NMR or enzymatic assay. Interestingly, none of the mutants accumulated trehalose any more but the ∆otsB mutant with its defect in trehalose-6-phosphate phosphatase activity accumulated trehalose-6-phosphate. Moreover, expression of otsA in a ∆otsB background under conditions where trehalose synthesis is not induced led to growth inhibition and the accumulation of trehalose-6-phosphate. Our results demonstrate that trehalose-6-phosphate affects multiple physiological activities in A. baumannii ATCC 19606.

Long-term and low-dose exposure to nanopolystyrene induces a protective strategy to maintain functional state of intestine barrier in nematode Caenorhabditis elegans

Functional state of intestinal barrier plays an important role for environmental animals in being against various toxicants. We investigated GATA transcriptional factor ELT-2-mediated intestinal response to nanopolystyrere in Caenorhabditis elegans. Prolonged exposure to nanopolystyrene (≥1 μg/L) induced an increase in expression of ELT-2, and intestinal RNA interference (RNAi) knockdown of elt-2 caused enhancement in intestinal permeability. Meanwhile, mutation of elt-2 resulted in susceptibility to nanopolystyrene toxicity, and ELT-2 functioned in intestine to regulate the nanopolystyrene toxicity. ERM-1, CLEC-63, and CLEC-85 were identified as targets of ELT-2 in regulating the nanopolystyrene toxicity. ERM-1 was required for maintaining functional state in intestinal barrier, and functioned synergistically with CLEC-63 or CLEC-85 to regulate nanopolystyrene toxicity. Therefore, activation of intestinal ELT-2 by nanopolystyrere could mediate a protective strategy to maintain the functional state of intestinal barrier. During this process, intestinal ELT-2 activated two different molecular signals (ERM-1 signal and CLEC-63/85 signal) for nematodes against the nanopolystyrene toxicity.

Molecular docking studies of phytochemicals against trehalose–6–phosphate phosphatases of pathogenic microbes

Background

Many of the pathogenic microbes use trehalose–6–phosphate phosphatase (TPP) enzymes for biosynthesis of sugar trehalose from trehalose–6–phosphate (T6P) in their pathway of infection and proliferation. Therefore, the present work is an approach to design new generation candidate drugs to inhibit TPP through in silico methods.

Results

Blast P and Clustal Omega phylogenetic analysis of TPP sequences were done for 12 organisms that indicate and confirm the presence of three conserved active site regions of known TPPs. Docking studies of 3D model of TPP with 17 phytochemicals revealed most of them have good binding affinity to an enzyme with rutin exhibiting highest affinity (Binding energy of − 7 kcal/mole). It has been found that during docking, phytochemical leads bind to active site region 3 of TPP sequences which coordinates Mg2+ and essential for catalysis.

Conclusions

Binding poses and distance measurement of TPP-phytochemical complexes of rutin, carpaine, stigmasterol, β-caryophyllene, and α-eudesmol reveals that the lead phytochemicals were in close proximity with most of the active site amino acids of region 3 (distance range from 1.796 to 2.747 Ao). This confirms the tight binding between enzyme and leads which may pave way for the discovery of new generation drugs against TPP producing pathogenic microbes to manage diseases.

A suicide inhibitor of nematode trehalose-6-phosphate phosphatases

Protein-based drug discovery strategies have the distinct advantage of providing insights into the molecular mechanisms of chemical effectors. Currently, there are no known trehalose-6-phosphate phosphatase (TPP) inhibitors that possess reasonable inhibition constants and chemical scaffolds amenable to convenient modification. In the present study, we subjected recombinant TPPs to a two-tiered screening approach to evaluate several diverse compound groups with respect to their potential as TPP inhibitors. From a total of 5452 compounds tested, N-(phenylthio)phthalimide was identified as an inhibitor of nematode TPPs with apparent Ki values of 1.0 μM and 0.56 μM against the enzymes from the zoonotic roundworms Ancylostoma ceylanicum and Toxocara canis, respectively. Using site-directed mutagenesis, we demonstrate that this compound acts as a suicide inhibitor that conjugates a strictly conserved cysteine residue in the vicinity of the active site of nematode TPPs. The anthelmintic properties of N-(phenylthio)phthalimide were assessed in whole nematode assays using larvae of the ascaroids T. canis and T. cati, as well as the barber's pole worm Haemonchus contortus. The compound was particularly effective against each of the ascaroids with an IC50 value of 9.3 μM in the survival assay of T. cati larvae, whereas no bioactivity was observed against H. contortus.

Metabolic Changes of Fusarium graminearum Induced by TPS Gene Deletion

Fusarium head blight (FHB) mainly resulting from Fusarium graminearum (Fg) Schwabe is a notorious wheat disease causing huge losses in wheat production globally. Fg also produces mycotoxins, which are harmful to human and domestic animals. In our previous study, we obtained two Fg mutants, TPS1^- and TPS2^-, respectively, with a single deletion of trehalose 6-phosphate synthase (TPS1) and trehalose 6-phosphate phosphatase (TPS2) compared with the wild type (WT). Both mutants were unable to synthesize trehalose and produced fewer mycotoxins. To understand the other biochemical changes induced by TPS gene deletion in Fg, we comprehensively analyzed the metabolomic differences between TPS^- mutants and the WT using NMR together with gas chromatography-flame ionization detection/mass spectrometry. The expression of some relevant genes was also quantified. The results showed that TPS1^- and TPS2^- mutants shared some common metabolic feature such as decreased levels for trehalose, Val, Thr, Lys, Asp, His, Trp, malonate, citrate, uridine, guanosine, inosine, AMP, C10:0, and C16:1 compared with the WT. Both mutants also shared some common expressional patterns for most of the relevant genes. This suggests that apart from the reduced trehalose biosynthesis, both TPS1 and TPS2 have roles in inhibiting glycolysis and the tricarboxylic acid cycle but promoting the phosphopentose pathway and nucleotide synthesis; the depletion of either TPS gene reduces the acetyl-CoA-mediated mycotoxin biosynthesis. TPS2^- mutants produced more fatty acids than TPS1^- mutants, suggesting different roles for TPS1 and TPS2, with TPS2^- mutants having impaired trehalose biosynthesis and trehalose 6-phosphate accumulation. This may offer opportunities for developing new fungicides targeting trehalose biosynthesis in Fg for FHB control and mycotoxin reduction in the FHB-affected cereals.

In Vitro and In Silico Studies of Glycyrrhetinic Acid Derivatives as Anti- Filarial Agents

BACKGROUND

Lymphatic filariasis is one of the chronic diseases in many parts of the tropics and sub-tropics of the world despite the use of standard drugs diethylcarbamazine and ivermectin because they kill microfilaries and not the adult parasites. Therefore, new leads with activity on adult parasites are highly desirable.

OBJECTIVE

Anti-filarial lead optimization by semi-synthetic modification of glycyrrhetinic acid (GA).

METHODS

The GA was first converted into 3-O-acyl derivative, which was further converted into 12 amide derivatives. All these derivatives were assessed for their antifilarial potential by parasite motility assay. The binding affinity of active GA derivatives on trehalose-6-phosphate phosphatase (Bm-TPP) was assessed by molecular docking studies.

RESULTS

Among 15 GA derivatives, GAD-2, GAD-3, and GAD-4 were found more potent than the GA and standard drug DEC. These derivatives reduced the motility of Brugia malayi adult worms by up to 74% while the GA and DEC reduced only up to 49%. Further, GA and most of its derivatives exhibited two times more reduction in MTT assay when compared to the standard drug DEC. These derivatives also showed 100% reduction of microfilariae and good interactions with Bm-TPP protein.

CONCLUSION

The present study suggests that 3-O-acyl and linear chain amide derivatives of glycyrrhetinic acid may be potent leads against B. malayi microfilariae and adult worms. These results might be helpful in developing QSAR model for optimizing a new class of antifilarial lead from a very common, inexpensive, and non toxic natural product.

Cereal Root Interactions with Soilborne Pathogens—From Trait to Gene and Back

Realizing the yield potential of crop plants in the presence of shifting pathogen populations, soil quality, rainfall, and other agro-environmental variables remains a challenge for growers and breeders worldwide. In this review, we discuss current approaches for combatting the soilborne phytopathogenic nematodes, Pratylenchus and Heterodera of wheat and barley, and Meloidogyne graminicola Golden and Birchfield, 1965 of rice. The necrotrophic fungal pathogens, Rhizoctonia solani Kühn 1858 AG-8 and Fusarium spp. of wheat and barley, also are discussed. These pathogens constitute major causes of yield loss in small-grain cereals of the Pacific Northwest, USA and throughout the world. Current topics include new sources of genetic resistance, molecular leads from whole genome sequencing and genome-wide patterns of hosts, nematode or fungal gene expression during root-pathogen interactions, host-induced gene silencing, and building a molecular toolbox of genes and regulatory sequences for deployment of resistance genes. In conclusion, improvement of wheat, barley, and rice will require multiple approaches.

Infective larvae of Anisakis simplex (Nematoda) accumulate trehalose and glycogen in response to starvation and temperature stress

Anisakis simplex L3 larvae infect fish and other seafood species such as squid or octopi; therefore, humans consuming raw or undercooked fish may become accidental hosts for this parasite. These larvae are induced to enter hypometabolism by cold temperatures. It is assumed that sugars (in particular trehalose and glycogen) are instrumental for survival under environmental stress conditions. To elucidate the mechanisms of environmental stress response in A. simplex, we observed the effects of starvation and temperature on trehalose and glycogen content, the activity of enzymes metabolizing those sugars, and the relative expression of genes of trehalose and glycogen metabolic pathways. The L3 of A. simplex synthesize trehalose both in low (0°C) and high temperatures (45°C). The highest content of glycogen was observed at 45°C at 36 h of incubation. On the second day of incubation, tissue content of trehalose depended on the activity of the enzymes: TPS was more active at 45°C, and TPP was more active at 0°C. The changes in TPP activity were consistent with the transcript level changes of the TPP gene, and the trehalose level, while glycogen synthesis correlates with the expression of glycogen synthase gene at 45°C; this suggests that the synthesis of trehalose is more essential. These results show that trehalose plays a key role in providing energy during the thermotolerance and starvation processes through the molecular and biochemical regulation of trehalose and glycogen metabolism.

Invertebrate Trehalose-6-Phosphate Synthase Gene: Genetic Architecture, Biochemistry, Physiological Function, and Potential Applications

The non-reducing disaccharide trehalose is widely distributed among various organisms. It plays a crucial role as an instant source of energy, being the major blood sugar in insects. In addition, it helps countering abiotic stresses. Trehalose synthesis in insects and other invertebrates is thought to occur via the trehalose-6-phosphate synthase (TPS) and trehalose-6-phosphate phosphatase (TPP) pathways. In many insects, the TPP gene has not been identified, whereas multiple TPS genes that encode proteins harboring TPS/OtsA and TPP/OtsB conserved domains have been found and cloned in the same species. The function of the TPS gene in insects and other invertebrates has not been reviewed in depth, and the available information is quite fragmented. The present review discusses the current understanding of the trehalose synthesis pathway, TPS genetic architecture, biochemistry, physiological function, and potential sensitivity to insecticides. We note the variability in the number of TPS genes in different invertebrate species, consider whether trehalose synthesis may rely only on the TPS gene, and discuss the results of in vitro TPS overexpression experiment. Tissue expression profile and developmental characteristics of the TPS gene indicate that it is important in energy production, growth and development, metamorphosis, stress recovery, chitin synthesis, insect flight, and other biological processes. We highlight the molecular and biochemical properties of insect TPS that make it a suitable target of potential pest control inhibitors. The application of trehalose synthesis inhibitors is a promising direction in insect pest control because vertebrates do not synthesize trehalose; therefore, TPS inhibitors would be relatively safe for humans and higher animals, making them ideal insecticidal agents without off-target effects.

Trehalose-6-phosphate phosphatase as a broad-spectrum therapeutic target against eukaryotic and prokaryotic pathogens

As opposed to organism-based drug screening approaches, protein-based strategies have the distinct advantage of providing insights into the molecular mechanisms of chemical effectors and thus afford a precise targeting. Capitalising on the increasing number of genome and transcriptome datasets, novel targets in pathogens for therapeutic intervention can be identified in a more rational manner when compared with conventional organism-based methodologies. Trehalose-6-phosphate phosphatases (TPPs) are structurally and functionally conserved enzymes of the trehalose biosynthesis pathway which play a critical role for pathogen survival, in particular, in parasites. The absence of these enzymes and trehalose biosynthesis from mammalian hosts has recently given rise to increasing interest in TPPs as novel therapeutic targets for drugs and vaccines. Here, we summarise some key aspects of the current state of research towards novel therapeutics targeting, in particular, nematode TPPs.

Caenorhabditis elegans: nature and nurture gift to nematode parasitologists

The free-living nematode Caenorhabditis elegans is the simplest animal model organism to work with. Substantial knowledge and tools have accumulated over 50 years of C. elegans research. The use of C. elegans relating to parasitic nematodes from a basic biology standpoint or an applied perspective has increased in recent years. The wealth of information gained on the model organism, the use of the powerful approaches and technologies that have advanced C. elegans research to parasitic nematodes and the enormous success of the omics fields have contributed to bridge the divide between C. elegans and parasite nematode researchers. We review key fields, such as genomics, drug discovery and genetics, where C. elegans and nematode parasite research have convened. We advocate the use of C. elegans as a model to study helminth metabolism, a neglected area ready to advance. How emerging technologies being used in C. elegans can pave the way for parasitic nematode research is discussed.

Modelling studies determing the mode of action of anthelmintics inhibiting in vitro trehalose-6-phosphate phosphatase (TPP) of Anisakis simplex s.l

The trehalose-6-phosphate phosphatase (TPP) enzyme is involved in the synthesis of trehalose, the main sugar in the energy metabolism of nematodes. TPP is a member of the HAD-like hydrolase superfamily and shows a robust and specific phosphatase activity for the substrate trehalose-6-phosphate. The presence of conserved active sites of TPP in closely related nematodes and its absence in humans makes it a promising target for antiparasitic drugs. In the present study, homology modeling, molecular docking and MD simulation techniques were used to explore the structure and dynamics of TPP. In the active site, a magnesium ion is stabilized by 3 coordinate bonds formed by D₁₈₉, D₁₉₁ and D₄₀₀. The key amino acids involved in ligand binding by the enzyme are C₁₉₈, Y₂₀₁,T₃₅₇, D₁₉₁ and Y₁₉₇. This study relied on docking to select potential inhibitors of TPP which were tested in vitro for sensitivity to anthelmintic drugs such as levamisole and ivermectin targeting Anisakis simplex. The higher toxicity of LEV than IVM was demonstrated after 96 h, 30% of larvae were motile in cultures with 100 μg/ml of LEV and 1000 μg/ml of IVM. We identified drug combination of LEV-IVM against in vitro A. simplex as agonistic effect (CI = 1.1). Levamisole appeared to be a more effective drug which inhibited enzyme activity after 48 h and expression of mRNA after 96 h at a concentration of 10 μg/ml. This preliminary study predicted the structure of TPP, and the results of an in vitro experiment involving A. simplex will contribute to the development of effective inhibitors with potential antiparasitic activity in the future.

daf-16/FoxO promotes gluconeogenesis and trehalose synthesis during starvation to support survival

daf-16/FoxO is required to survive starvation in Caenorhabditis elegans, but how daf-16IFoxO promotes starvation resistance is unclear. We show that daf-16/FoxO restructures carbohydrate metabolism by driving carbon flux through the glyoxylate shunt and gluconeogenesis and into synthesis of trehalose, a disaccharide of glucose. Trehalose is a well-known stress protectant, capable of preserving membrane organization and protein structure during abiotic stress. Metabolomic, genetic, and pharmacological analyses confirm increased trehalose synthesis and further show that trehalose not only supports survival as a stress protectant but also serves as a glycolytic input. Furthermore, we provide evidence that metabolic cycling between trehalose and glucose is necessary for this dual function of trehalose. This work demonstrates that daf-16/FoxO promotes starvation resistance by shifting carbon metabolism to drive trehalose synthesis, which in turn supports survival by providing an energy source and acting as a stress protectant.

Most animals rarely have access to a constant supply of food, and so have evolved ways to cope with times of plenty and times of shortage. Insulin is a hormone that travels throughout the body to signal when an animal is well fed. Insulin signaling inhibits the activity of a protein called FoxO, which otherwise switches on and off hundreds of genes to control the starvation response.

The roundworm, Caenorhabditis elegans, has been well studied in the laboratory, and often has to cope with starvation in the wild. These worms can pause their development if no food is available, or divert to a different developmental path if they anticipate that food will be short in future. As with more complex animals, the worm responds to starvation by reducing insulin-like signaling, which in turn activates a FoxO protein called daf-16. When the worms stop feeding, daf-16 is switched on, which is crucial for survival.

It was known how daf-16 stops the roundworm’s development, but it was not known how it helps the worms to survive starvation. Now, Hibshman et al. have compared normal roundworm larvae to larvae that are missing the gene for daf-16 to determine how this protein influences the roundworm’s ability to survive starvation.

The worms were examined with and without food, to look for which genes were switched on and off by daf-16 during starvation. This revealed that daf-16 controls metabolism, activating a metabolic shortcut that makes the worms produce glucose and begin turning it into another type of sugar, called trehalose. This sugar usually promotes survival in conditions where water is limiting, like dehydration and high salt, but it can also be broken down to release energy. The levels of trehalose in the worms rose within hours of the onset of starvation.

To confirm the importance of trehalose in surviving starvation, roundworms with mutations in genes involved in glucose or trehalose production were examined, as was the effect of giving starving worms glucose or trehalose. Disrupting the production of sugars caused the worms to die sooner of starvation, while supplementing with sugar had the opposite effect meaning the worms survived for longer.

Taken together, these findings reveal that daf-16 protects against starvation by shifting metabolism towards the production of trehalose. This helps worms to survive by both protecting them from stress and providing them with a source of energy. These findings not only extend the current understanding of how animals respond to starvation, but could also lead to improved understanding of diseases where this response goes wrong, including diabetes and obesity.

Lipid and Carbohydrate Metabolism in Caenorhabditis elegans

Lipid and carbohydrate metabolism are highly conserved processes that affect nearly all aspects of organismal biology. Caenorhabditis elegans eat bacteria, which consist of lipids, carbohydrates, and proteins that are broken down during digestion into fatty acids, simple sugars, and amino acid precursors. With these nutrients, C. elegans synthesizes a wide range of metabolites that are required for development and behavior. In this review, we outline lipid and carbohydrate structures as well as biosynthesis and breakdown pathways that have been characterized in C. elegans We bring attention to functional studies using mutant strains that reveal physiological roles for specific lipids and carbohydrates during development, aging, and adaptation to changing environmental conditions.

Enzyme characteristics of pathogen-specific trehalose-6-phosphate phosphatases

Owing to the key role of trehalose in pathogenic organisms, there has recently been growing interest in trehalose metabolism for therapeutic purposes. Trehalose-6-phosphate phosphatase (TPP) is a pivotal enzyme in the most prominent biosynthesis pathway (OtsAB). Here, we compare the enzyme characteristics of recombinant TPPs from five important nematode and bacterial pathogens, including three novel members of this protein family. Analysis of the kinetics of trehalose-6-phosphate hydrolysis reveals that all five enzymes display a burst-like kinetic behaviour which is characterised by a decrease of the enzymatic rate after the pre-steady state. The observed super-stoichiometric burst amplitudes can be explained by multiple global conformational changes in members of this enzyme family during substrate processing. In the search for specific TPP inhibitors, the trapping of the complex conformational transitions in TPPs during the catalytic cycle may present a worthwhile strategy to explore.

Rational design of reversible inhibitors for trehalose 6-phosphate phosphatases

In some organisms, environmental stress triggers trehalose biosynthesis that is catalyzed collectively by trehalose 6-phosphate synthase, and trehalose 6-phosphate phosphatase (T6PP). T6PP catalyzes the hydrolysis of trehalose 6-phosphate (T6P) to trehalose and inorganic phosphate and is a promising target for the development of antibacterial, antifungal and antihelminthic therapeutics. Herein, we report the design, synthesis and evaluation of a library of aryl d-glucopyranoside 6-sulfates to serve as prototypes for small molecule T6PP inhibitors. Steady-state kinetic techniques were used to measure inhibition constants (K_i) of a panel of structurally diverse T6PP orthologs derived from the pathogens Brugia malayi, Ascaris suum, Mycobacterium tuberculosis, Shigella boydii and Salmonella typhimurium. The binding affinities of the most active inhibitor of these T6PP orthologs, 4-n-octylphenyl α-d-glucopyranoside 6-sulfate (9a), were found to be in the low micromolar range. The K_i of 9a with the B. malayi T6PP ortholog is 5.3 ± 0.6 μM, 70-fold smaller than the substrate Michaelis constant. The binding specificity of 9a was demonstrated using several representative sugar phosphate phosphatases from the HAD enzyme superfamily, the T6PP protein fold family of origin. Lastly, correlations drawn between T6PP active site structure, inhibitor structure and inhibitor binding affinity suggest that the aryl d-glucopyranoside 6-sulfate prototypes will find future applications as a platform for development of tailored second-generation T6PP inhibitors.

Gluconeogenesis: An ancient biochemical pathway with a new twist

Synthesis of sugars from simple carbon sources is critical for survival of animals under limited nutrient availability. Thus, sugar-synthesizing enzymes should be present across the entire metazoan spectrum. Here, we explore the evolution of glucose and trehalose synthesis using a phylogenetic analysis of enzymes specific for the two pathways. Our analysis reveals that the production of trehalose is the more ancestral biochemical process, found in single cell organisms and primitive metazoans, but also in insects. The gluconeogenic-specific enzyme glucose-6-phosphatase (G6Pase) first appears in Cnidaria, but is also present in Echinodermata, Mollusca and Vertebrata. Intriguingly, some species of nematodes and arthropods possess the genes for both pathways. Moreover, expression data from Drosophila suggests that G6Pase and, hence, gluconeogenesis, initially had a neuronal function. We speculate that in insects-and possibly in some vertebrates-gluconeogenesis may be used as a means of neuronal signaling.

The plant energy sensor: evolutionary conservation and divergence of SnRK1 structure, regulation, and function

The SnRK1 (SNF1-related kinase 1) kinases are the plant cellular fuel gauges, activated in response to energy-depleting stress conditions to maintain energy homeostasis while also gatekeeping important developmental transitions for optimal growth and survival. Similar to their opisthokont counterparts (animal AMP-activated kinase, AMPK, and yeast Sucrose Non-Fermenting 1, SNF), they function as heterotrimeric complexes with a catalytic (kinase) α subunit and regulatory β and γ subunits. Although the overall configuration of the kinase complexes is well conserved, plant-specific structural modifications (including a unique hybrid βγ subunit) and associated differences in regulation reflect evolutionary divergence in response to fundamentally different lifestyles. While AMP is the key metabolic signal activating AMPK in animals, the plant kinases appear to be allosterically inhibited by sugar-phosphates. Their function is further fine-tuned by differential subunit expression, localization, and diverse post-translational modifications. The SnRK1 kinases act by direct phosphorylation of key metabolic enzymes and regulatory proteins, extensive transcriptional regulation (e.g. through bZIP transcription factors), and down-regulation of TOR (target of rapamycin) kinase signaling. Significant progress has been made in recent years. New tools and more directed approaches will help answer important fundamental questions regarding their structure, regulation, and function, as well as explore their potential as targets for selection and modification for improved plant performance in a changing environment.

Molecular characterization of Tps1 and Treh genes in Drosophila and their role in body water homeostasis

In insects, trehalose serves as the main sugar component of haemolymph. Trehalose is also recognized as a mediator of desiccation survival due to its proposed ability to stabilize membranes and proteins. Although the physiological role of trehalose in insects has been documented for decades, genetic evidence to support the importance of trehalose metabolism remains incomplete. We here show on the basis of genetic and biochemical evidence that the trehalose synthesis enzyme Tps1 is solely responsible for the de novo synthesis of trehalose in Drosophila. Conversely, a lack of the gene for the trehalose hydrolyzing enzyme Treh causes an accumulation of trehalose that is lethal during the pupal period, as is observed with Tps1 mutants. Lack of either Tps1 or Treh results in a significant reduction in circulating glucose, suggesting that the maintenance of glucose levels requires a continuous turnover of trehalose. Furthermore, changes in trehalose levels are positively correlated with the haemolymph water volume. In addition, both Tps1 and Treh mutant larvae exhibit a high lethality after desiccation stress. These results demonstrate that the regulation of trehalose metabolism is essential for normal development, body water homeostasis, and desiccation tolerance in Drosophila.

A Caenorhabditis elegans Genome-Scale Metabolic Network Model

Caenorhabditis elegans is a powerful model to study metabolism and how it relates to nutrition, gene expression, and life history traits. However, while numerous experimental techniques that enable perturbation of its diet and gene function are available, a high-quality metabolic network model has been lacking. Here, we reconstruct an initial version of the C. elegans metabolic network. This network model contains 1,273 genes, 623 enzymes, and 1,985 metabolic reactions and is referred to as iCEL1273. Using flux balance analysis, we show that iCEL1273 is capable of representing the conversion of bacterial biomass into C. elegans biomass during growth and enables the predictions of gene essentiality and other phenotypes. In addition, we demonstrate that gene expression data can be integrated with the model by comparing metabolic rewiring in dauer animals versus growing larvae. iCEL1273 is available at a dedicated website (wormflux.umassmed.edu) and will enable the unraveling of the mechanisms by which different macro- and micronutrients contribute to the animal's physiology.

Expression of Genes Encoding the Enzymes for Glycogen and Trehalose Metabolism in L3 and L4 Larvae of Anisakis simplex

Trehalose and glycogen metabolism plays an important role in supporting life processes in many nematodes, including Anisakis simplex. Nematodes, cosmopolitan helminths parasitizing sea mammals and humans, cause a disease known as anisakiasis. The aim of this study was to investigate the expression of genes encoding the enzymes involved in the metabolism of trehalose and glycogen—trehalose-6-phosphate synthase (TPS), trehalose-6-phosphate phosphatase (TPP), glycogen synthase (GS), and glycogen phosphorylase (GP)—in stage L3 and stage L4 larvae of A. simplex. The expression of mRNA all four genes, tps, tpp, gs, and gp, was examined by real-time polymerase chain reaction. The A. simplex ribosomal gene (18S) was used as a reference gene. Enzymatic activity was determined. The expression of trehalose enzyme genes was higher in L3 than in L4 larvae, but an inverse relationship was noted for the expression of gs and gp genes.

Imaging Cellular Inorganic Phosphate in Caenorhabditis elegans Using a Genetically Encoded FRET-Based Biosensor

Inorganic phosphate (Pi) has central roles in metabolism, cell signaling and energy conversion. The distribution of Pi to each cell and cellular compartment of an animal must be tightly coordinated with its dietary supply and with the varied metabolic demands of individual cells. An analytical method for monitoring Pi dynamics with spatial and temporal resolution is therefore needed to gain a comprehensive understanding of mechanisms governing the transport and recycling of this essential nutrient. Here we demonstrate the utility of a genetically encoded FRET-based Pi sensor to assess cellular Pi levels in the nematode Caenorhabditis elegans. The sensor was expressed in different cells and tissues of the animal, including head neurons, tail neurons, pharyngeal muscle, and the intestine. Cytosolic Pi concentrations were monitored using ratiometric imaging. Injection of phosphate buffer into intestinal cells confirmed that the sensor was responsive to changes in Pi concentration in vivo. Live Pi imaging revealed cell-specific and developmental stage-specific differences in cytosolic Pi concentrations. In addition, cellular Pi levels were perturbed by food deprivation and by exposure to the respiratory inhibitor cyanide. These results suggest that Pi concentration is a sensitive indicator of metabolic status. Moreover, we propose that live Pi imaging in C. elegans is a powerful approach to discern mechanisms that govern Pi distribution in individual cells and throughout an animal.

Integration of carbohydrate metabolism and redox state controls dauer larva formation in Caenorhabditis elegans

Under adverse conditions, Caenorhabditis elegans enters a diapause stage called the dauer larva. External cues signal the nuclear hormone receptor DAF-12, the activity of which is regulated by its ligands: dafachronic acids (DAs). DAs are synthesized from cholesterol, with the last synthesis step requiring NADPH, and their absence stimulates dauer formation. Here we show that NADPH levels determine dauer formation in a regulatory mechanism involving key carbohydrate and redox metabolic enzymes. Elevated trehalose biosynthesis diverts glucose-6-phosphate from the pentose phosphate pathway, which is the major source of cellular NADPH. This enhances dauer formation due to the decrease in the DA level. Moreover, DAF-12, in cooperation with DAF-16/FoxO, induces negative feedback of DA synthesis via activation of the trehalose-producing enzymes TPS-1/2 and inhibition of the NADPH-producing enzyme IDH-1. Thus, the dauer developmental decision is controlled by integration of the metabolic flux of carbohydrates and cellular redox potential.

Panoramic view of a superfamily of phosphatases through substrate profiling

Large-scale activity profiling of enzyme superfamilies provides information about cellular functions as well as the intrinsic binding capabilities of conserved folds. Herein, the functional space of the ubiquitous haloalkanoate dehalogenase superfamily (HADSF) was revealed by screening a customized substrate library against >200 enzymes from representative prokaryotic species, enabling inferred annotation of ∼35% of the HADSF. An extremely high level of substrate ambiguity was revealed, with the majority of HADSF enzymes using more than five substrates. Substrate profiling allowed assignment of function to previously unannotated enzymes with known structure, uncovered potential new pathways, and identified iso-functional orthologs from evolutionarily distant taxonomic groups. Intriguingly, the HADSF subfamily having the least structural elaboration of the Rossmann fold catalytic domain was the most specific, consistent with the concept that domain insertions drive the evolution of new functions and that the broad specificity observed in HADSF may be a relic of this process.

A genetically encoded Förster resonance energy transfer sensor for monitoring in vivo trehalose-6-phosphate dynamics

Trehalose-6-phosphate is a pivotal regulator of sugar metabolism, growth, and osmotic equilibrium in bacteria, yeasts, and plants. To directly visualize the intracellular levels of intracellular trehalose-6-phosphate, we developed a series of specific Förster resonance energy transfer (FRET) sensors for in vivo microscopy. We demonstrated real-time monitoring of regulation in the trehalose pathway of Escherichia coli. In Saccharomyces cerevisiae, we could show that the concentration of free trehalose-6-phosphate during growth on glucose is in a range sufficient for inhibition of hexokinase. These findings support the hypothesis of trehalose-6-phosphate as the effector of a negative feedback system, similar to the inhibition of hexokinase by glucose-6-phosphate in mammalian cells and controlling glycolytic flux.

The in vitro effect of ivermectin on the activity of trehalose synthesis pathway enzymes and their mRNA expression in the muscle of adult female Ascaris suum (Nematoda)

The in vitro effect of ivermectin lethal dose on the activity of trehalose-6-phosphate synthase (TPS) and phosphatase (TPP) and the expression of their mRNA (tps1, tps2, and tpp genes) in the muscle of adult female Ascaris suum was investigated. The presence of ivermectin in the medium caused a decrease in TPS and TPP activities during the experiment compared with the start and control groups. The exception was the group of worms grown for 8 hours in a IVM solution, in which there was a little higher TPS activity than in the control. Real-time qPCR analysis showed reduced expression of tps1 and tps2, and unchanged tpp expression after 20 hours of incubation relative to the expression at time zero. Relative to the appropriate control groups, the expression of tps2 gene was slight increased but the other two genes were reduced after 8-hours of IVM-treatment. Then the expression of all three genes was lower at the end of cultivation. The level of gene expression was positively correlated with the activity of specific enzymes. In the case of tpp gene there was only a weak correlation. Prolonged exposure to ivermectin was effective in lowering TPS and TPP activity and their mRNA expression. However, the drug did not block the pathway.

Structure of the trehalose-6-phosphate phosphatase from Brugia malayi reveals key design principles for anthelmintic drugs

Parasitic nematodes are responsible for devastating illnesses that plague many of the world's poorest populations indigenous to the tropical areas of developing nations. Among these diseases is lymphatic filariasis, a major cause of permanent and long-term disability. Proteins essential to nematodes that do not have mammalian counterparts represent targets for therapeutic inhibitor discovery. One promising target is trehalose-6-phosphate phosphatase (T6PP) from Brugia malayi. In the model nematode Caenorhabditis elegans, T6PP is essential for survival due to the toxic effect(s) of the accumulation of trehalose 6-phosphate. T6PP has also been shown to be essential in Mycobacterium tuberculosis. We determined the X-ray crystal structure of T6PP from B. malayi. The protein structure revealed a stabilizing N-terminal MIT-like domain and a catalytic C-terminal C2B-type HAD phosphatase fold. Structure-guided mutagenesis, combined with kinetic analyses using a designed competitive inhibitor, trehalose 6-sulfate, identified five residues important for binding and catalysis. This structure-function analysis along with computational mapping provided the basis for the proposed model of the T6PP-trehalose 6-phosphate complex. The model indicates a substrate-binding mode wherein shape complementarity and van der Waals interactions drive recognition. The mode of binding is in sharp contrast to the homolog sucrose-6-phosphate phosphatase where extensive hydrogen-bond interactions are made to the substrate. Together these results suggest that high-affinity inhibitors will be bi-dentate, taking advantage of substrate-like binding to the phosphoryl-binding pocket while simultaneously utilizing non-native binding to the trehalose pocket. The conservation of the key residues that enforce the shape of the substrate pocket in T6PP enzymes suggest that development of broad-range anthelmintic and antibacterial therapeutics employing this platform may be possible.

Here, we describe the structure of trehalose-6-phosphate phosphatase (T6PP) from Brugia malayi. This enzyme is essential to the organism; deletion of the gene encoding T6PP results in toxic accumulation of trehalose 6-phosphate. Structure-guided mutagenesis coupled with kinetic analyses revealed residues important for binding and catalysis. The model for substrate binding suggests a binding mode in which shape complementarity plays a major role. Conservation of binding residues among T6PP orthologs present in pathogenic nematodes and bacteria favors T6PP as a suitable target for broad-range anthelmintic and antibacterial drug design.

Molecular strategies of the Caenorhabditis elegans dauer larva to survive extreme desiccation

Massive water loss is a serious challenge for terrestrial animals, which usually has fatal consequences. However, some organisms have developed means to survive this stress by entering an ametabolic state called anhydrobiosis. The molecular and cellular mechanisms underlying this phenomenon are poorly understood. We recently showed that Caenorhabditis elegans dauer larva, an arrested stage specialized for survival in adverse conditions, is resistant to severe desiccation. However, this requires a preconditioning step at a mild desiccative environment to prepare the organism for harsher desiccation conditions. A systems approach was used to identify factors that are activated during this preconditioning. Using microarray analysis, proteomics, and bioinformatics, genes, proteins, and biochemical pathways that are upregulated during this process were identified. These pathways were validated via reverse genetics by testing the desiccation tolerances of mutants. These data show that the desiccation response is activated by hygrosensation (sensing the desiccative environment) via head neurons. This leads to elimination of reactive oxygen species and xenobiotics, expression of heat shock and intrinsically disordered proteins, polyamine utilization, and induction of fatty acid desaturation pathway. Remarkably, this response is specific and involves a small number of functional pathways, which represent the generic toolkit for anhydrobiosis in plants and animals.

Sex differences in carbohydrate metabolism are linked to gene expression in Caenorhabditis elegans

The male and the hermaphrodite forms of the nematode Caenorhabditis elegans (C. elegans) differ markedly in anatomy, nervous system and behavior at adulthood. Using the male mutants fog-2, him-5, and him-8, we compared body proportions and composition, and aspects of carbohydrate metabolism and gene expression between the C. elegans sexes in three adult stages. In all experiments, both sexes were grown on the same plate and separated using flow cytometry. The fat to fat-free mass ratio and the body volume-adjusted fat mass is similar between the sexes, although the body size is more than 50% smaller in adult males than in age-matched hermaphrodites. The volume-adjusted total RNA content is approximately 2-fold lower in males. Biochemical and NMR-based analyses reveal higher trehalose levels and much lower glucose levels in males than in hermaphrodites. The resulting trehalose-to-glucose ratio is 5.4-fold higher in males. These sex differences are reflected in gene expression data because the genes encoding key enzymes of the glycolysis and trehalose synthesis pathways are more highly expressed in males than in hermaphrodites. Notably, expression of the phosphofructokinase gene (C50F4.2) is 29-fold higher in males. Comparative analysis of gene expression data identifies 285 male-specific and 160 hermaphrodite-specific genes. These include transcription factor and C-type lectin-encoding genes. More than 35% of all C-type lectin genes are more highly expressed in males. The expression of many C-type lectin genes differs by a factor of >100 between the sexes. In conclusion, we found sex differences in carbohydrate metabolism that are linked to gene expression and identified certain lectin genes that are differentially expressed by the C. elegans sexes.

In vitro silencing of Brugia malayi trehalose-6-phosphate phosphatase impairs embryogenesis and in vivo development of infective larvae in jirds

Background

The trehalose metabolic enzymes have been considered as potential targets for drug or vaccine in several organisms such as Mycobacterium, plant nematodes, insects and fungi due to crucial role of sugar trehalose in embryogenesis, glucose uptake and protection from stress. Trehalose-6-phosphate phosphatase (TPP) is one of the enzymes of trehalose biosynthesis that has not been reported in mammals. Silencing of tpp gene in Caenorhabditis elegans revealed an indispensable functional role of TPP in nematodes.

Methodology and Principal Findings

In the present study, functional role of B. malayi tpp gene was investigated by siRNA mediated silencing which further validated this enzyme to be a putative antifilarial drug target. The silencing of tpp gene in adult female B. malayi brought about severe phenotypic deformities in the intrauterine stages such as distortion and embryonic development arrest. The motility of the parasites was significantly reduced and the microfilarial production as well as their in vitro release from the female worms was also drastically abridged. A majority of the microfilariae released in to the culture medium were found dead. B. malayi infective larvae which underwent tpp gene silencing showed 84.9% reduced adult worm establishment after inoculation into the peritoneal cavity of naïve jirds.

Conclusions/Significance

The present findings suggest that B. malayi TPP plays an important role in the female worm embryogenesis, infectivity of the larvae and parasite viability. TPP enzyme of B. malayi therefore has the potential to be exploited as an antifilarial drug target.

Lymphatic filariasis, one of the neglected tropical diseases, is the second leading cause of permanent and long term disability. Control of the disease relies on the mass administration of drugs which mainly act on the microfilariae without substantial effect on adult worms. Drugs need to be continued for several years to block the transmission of infection which may result in to development of resistant parasites. The sugar trehalose has been shown to play several important functions in the nematodes, and trehalose biosynthetic enzymes have been considered as potential targets for drug or vaccine candidate. In the present study we silenced trehalose-6-phosphate phosphatase and studied the biological function of TPP enzyme in the filarial nematode B. malayi viability, female worm embryogenesis and establishment of infection in the host. In vitro gene silencing was done in adult parasites using 5 mM concentration of siRNA while 2 mM of siRNA was used to treat L3 which were further inoculated into the peritoneal cavity of jirds to study the effect of siRNA treatment on in vivo larval development. The present findings validate trehalose-6-phosphate phosphatase as a vital antifilarial drug target.