Acetylcholinesterase in the sea urchin Lytechinus variegatus: characterization and developmental expression in larvae

Genomic signatures of exceptional longevity and negligible aging in the long-lived red sea urchin

The red sea urchin (Mesocentrotus franciscanus) is one of the Earth's longest-living animals, reported to live more than 100 years with indeterminate growth, life-long reproduction, and no increase in mortality rate with age. To understand the genetic underpinnings of longevity and negligible aging, we constructed a chromosome-level assembly of the red sea urchin genome and compared it to that of short-lived sea urchin species. Genome-wide syntenic alignments identified chromosome rearrangements that distinguish short- and long-lived species. Expanded gene families in long-lived species play a role in innate immunity, sensory nervous system, and genome stability. An integrated network of genes under positive selection in the red sea urchin was involved in genomic regulation, mRNA fidelity, protein homeostasis, and mitochondrial function. Our results implicated known longevity genes in sea urchin longevity but also revealed distinct molecular signatures that may promote long-term maintenance of tissue homeostasis, disease resistance, and negligible aging.

Early-stage anomalies in the sea urchin (Paracentrotus lividus) as bioindicators of multiple stressors in the marine environment: Overview and future perspectives

The morphological anomalies of the early development stages of the sea urchin Paracentrotus lividus, caused by exposure to environmental stressors, are used as biomarker in ecotoxicological and ecological investigations. Here, we reviewed the available literature and classified the embryo and larval anomalies identified so far, to highlight potential commonalities or differences related to the biological action of the different stressors and their ecological impact. Morphological anomalies are influenced by a) the developmental stage of exposure to stressors; b) the intensity of the stress; c) the intra- and inter-cellular mechanisms affected by the exposure to environmental agents. The classification and analysis of embryo and larvae anomalies, either observed by the authors of this review and reported in literature, indicate that sea urchin abnormalities, caused by exposure to different stressors, can be very similar among them and classified into 18 main types, which can occur individually or mixed. All anomalies can be used to calculate an Index of Contaminant Impact to assess the impact of multiple stressors and to identify relationships between morphological anomalies and compromised biological mechanisms. This approach could be useful for a first screening of the presence of potential stressors impairing the growth and development of the early life stages of marine organisms, thus providing a relevant advancement for in future monitoring activities devoted to assess the health status in coastal marine ecosystems.

Effects of monocrotophos pesticide on cholinergic and dopaminergic neurotransmitter systems during early development in the sea urchin Hemicentrotus pulcherrimus

During early development in sea urchins, classical neurotransmitters, including acetylcholine (ACh), dopamine (DA), and serotonin (5-HT), play important roles in the regulation of morphogenesis and swimming behavior. However, the underlying mechanisms of how organophosphate pesticides cause developmental neurotoxicity by interfering with different neurotransmitter systems are unclear. In this study, we investigated the effects of 0.01, 0.10, and 1.00mg/L monocrotophos (MCP) pesticide on the activity of acetyltransferase (ChAT), acetylcholinesterase (AChE), monoamine oxidase, the concentration of DA, dopamine transporter, and the transcription activity of DA receptor D₁ and tyrosine hydroxylase, during critical periods in cholinergic and dopaminergic nervous system development in sea urchin (Hemicentrotus pulcherrimus) embryos and larvae. At the blastula stages, MCP disrupted DA metabolism but not 5-HT metabolism, resulting in abnormal development. High ChAT and AChE activity were observed at the gastrulation-completed stage and the two-armed pluteus stage, respectively, MCP inhibited ChAT activity and AChE activity/distribution and resulted in developmental defects of the plutei. From the gastrula stage to the two-armed pluteus stage, we found ubiquitous disrupting effects of MCP on ACh, DA, and 5-HT metabolism, particularly at critical periods during the development of these neurotransmitter systems. Therefore, we propose that this disruption is one of the main mechanisms of MCP-related developmental neurotoxicity, which would contribute better understanding insight into the mechanism of MCP pesticide's toxic effects.

Multidisciplinary screening of toxicity induced by silica nanoparticles during sea urchin development

The aim of this study was to investigate the potential toxicity of Silica nanoparticles (SiO2 NPs) in seawater by using the sea urchin Paracentrotus lividus as biological model. SiO2 NPs exposure effects were identified on the sperm of the sea urchin through a multidisciplinary approach, combining developmental biology, ecotoxicology, biochemistry, and microscopy analyses. The following responses were measured: (i) percentage of eggs fertilized by exposed sperm; (ii) percentage of anomalies and undeveloped embryos and larvae; (iii) enzyme activity alterations (acetylcholinesterase, AChE) in the early developmental stages, namely gastrula and pluteus. Sperms were exposed to seawater containing SiO2 NPs suspensions ranging from 0.0001mg/L to 50mg/L. Fertilization ability was not affected at any concentration, whereas a significant percentage of anomalies in the offspring were observed and quantified by means of EC50 at gastrula stage, including undeveloped and anomalous embryos (EC50=0.06mg/L), and at pluteus stage, including skeletal anomalies and delayed larvae (EC50=0.27mg/L). Moreover, morphological anomalies were observed in larvae at pluteus stage, by immunolocalizing molecules involved in larval development and neurotoxicity effects - such as acetylated tubulin and choline acetyltransferase (ChAT) - and measuring AChE activity. Exposure of sea urchins to SiO2 NPs caused neurotoxic damage and a decrease of AChE expression in a non-dose-dependent manner. In conclusion, through the multidisciplinary approach used in this study SiO2 NPs toxicity in sea urchin offspring could be assessed. Therefore, the measured responses are suitable for detecting embryo- and larval- toxicity induced by these NPs.

Molecular characterization of an acetylcholinesterase from the hemichordate Saccoglossus kowalevskii

Our goal is to understand the evolution of the structure and function of cholinesterases (ChEs) in the deuterostome lineage and in particular to understand the role of paralogous enzymes such as the acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) of the vertebrates. We have, in the past, characterized ChEs in two acraniate deuterostomes: amphioxus (a cephalochordate) and Ciona intestinalis (a urochordate). Here we present results on an AChE from a basal deuterostome, a model hemichordate, the acorn worm Saccoglossus kowalevskii. Of the eight genes coding for putative ChE-like proteins possessing Trp84, a characteristic of the choline-binding catalytic subsite of ChEs, we cloned a full length cDNA with a coding sequence typical of an acraniate AChE possessing a C-terminal exon coding for a typical T-peptide. We then used in vitro expression of the cDNA in COS-7 cells to characterize the AChE kinetically, pharmacologically, and biochemically. The cDNA codes for an AChE (AChE1), which is found in monomeric (G1), dimeric (G2), and tetrameric (G4) forms; and interacts with poly-L-proline, PRiMA, and ColQ, characteristic of an AChE possessing a T-peptide. The expression of the AChE is temperature dependent, with greater expression at 30 °C. We discuss the implications of these data for the evolution of the ChEs in the deuterostomes.

Evolutionary origins of retinoid active short-chain dehydrogenases/reductases of SDR16C family

Vertebrate enzymes that belong to the 16C family of short-chain dehydrogenases/reductases (SDR16C) were shown to play an essential role in the control of retinoic acid (RA) levels during development. To trace the evolution of enzymatic function of SDR16C family, and to examine the origins of the pathway for RA biosynthesis from vitamin A, we identified putative SDR16C enzymes through the extensive search of available genome sequencing data in a subset of species representing major metazoan phyla. The phylogenetic analysis revealed that enzymes from protostome, non-chordate deuterostome and invertebrate chordate species are found in three clades of SDR16C family containing retinoid active enzymes, which are retinol dehydrogenase 10 (RDH10), retinol dehydrogenases E2 (RDHE2) and RDHE2-similar, and dehydrogenase reductase (SDR family) member 3 (DHRS3). For the initial functional analysis, we cloned RDH10- and RDHE2-related enzymes from the early developmental stages of a non-chordate deuterostome, green sea urchin Lytechinus variegatus, and an invertebrate chordate, sea squirt Ciona intestinalis. In situ hybridization revealed that these proteins are expressed in a pattern relevant to development, while assays performed on proteins expressed in mammalian cell culture showed that they possess retinol-oxidizing activity as their vertebrate homologs. The existence of invertebrate homologs of DHRS3 was inferred from the analysis of phylogeny and cofactor-binding residues characteristic of preference for NADP(H). The presence of invertebrate homologs in the DHRS3 group of SDR16C is interesting in light of the complex mutually activating interaction, which we have recently described for human RDH10 and DHRS3 enzymes. Further functional analysis of these homologs will establish whether this interaction evolved to control retinoid homeostasis only in vertebrates, or is also conserved in pre-vertebrates.

Biochemical and molecular characterisation of acetylcholinesterase in four field populations of Bactrocera dorsalis (Hendel) (Diptera: Tephritidae)

BACKGROUND

The oriental fruit fly, Bactrocera dorsalis, is a major pest that infects fruits and agricultural products worldwide. The latest resistance monitoring of B. dorsalis from mainland China has identified high levels of resistance to insecticides. In this study, the biochemical and molecular characteristics of acetylcholinesterase (AChE) in four field populations of B. dorsalis are investigated.

RESULTS

Among the four populations, the DG population and its purified AChE were found to be the least susceptible to malathion and five inhibitors, whereas the KM population and its purified AChE were the most susceptible. The highest catalytic activity of purified AChE was found for the KM population, and the catalytic activity of the DG population was the lowest. Among developmental stages, the AChE purified from larvae was found to be the most insusceptible to inhibitors, but its catalytic activity was the highest. Sequence analysis of the cDNA encoding AChE showed that some residue differences existed. However, no significant differences in expression levels of the AChE gene among populations and developmental stages were detected.

CONCLUSION

The results suggest that the decrease in susceptibility of B. dorsalis was mainly caused by decrease in AChE activity, and they provide a broad view on the relation between AChE and resistance.

Back-scattering interferometry: an ultrasensitive method for the unperturbed detection of acetylcholinesterase-inhibitor interactions

A series of inhibitors of acetylcholinesterase (AChE) have been screened by back-scattering interferometry (BSI). Enzyme levels as low as 100 pM (22,000 molecules of AChE) can be detected. This method can be used to screen for mixed AChE inhibitors, agents that have shown high efficacy against Alzheimer's disease, by detecting dual-binding interactions. E = enzyme, I = inhibitor, S = substrate.

Cholinergic and non-cholinergic functions of two acetylcholinesterase genes revealed by gene-silencing in Tribolium castaneum

We compared biological functions of two acetylcholinesterase genes (TcAce1 and TcAce2) in Tribolium castaneum, a globally distributed major pest of stored grain products and an emerging model organism, by using RNA interference. Although both genes expressed at all developmental stages and mainly in the brain, the transcript level of TcAce1 was 1.2- to 8.7-fold higher than that of TcAce2, depending on developmental stages. Silencing TcAce1 in 20-day larvae led to 100% mortality within two weeks after eclosion and increased larval susceptibilities to anticholinesterase insecticides. In contrast, silencing TcAce2 did not show insect mortality and significantly affect insecticide susceptibility, but delayed insect development and reduced female egg-laying and egg hatching. These results demonstrate for the first time that TcAce1 plays a major role in cholinergic functions and is the target of anticholinesterase insecticides, whereas TcAce2 plays an important, non-cholinergic role in female reproduction, embryo development, and growth of offspring.

Silencing of acetylcholinesterase gene of Helicoverpa armigera by siRNA affects larval growth and its life cycle

RNA interference is an effective means of regulation of gene expression both in vitro and in vivo. We studied the effect of siRNA on larval development by selective targeting of the acetylcholinesterase (AChE) gene of Helicoverpa armigera. Chemically synthesized siRNA molecules were directly fed to H. armigera larvae along with the artificial diet. The siRNA treatment resulted in specific gene silencing of AChE and consequently brought about mortality, growth inhibition of larvae, reduction in the pupal weight, malformation and drastically reduced fecundity as compared to control larvae. Our studies suggest some novel roles for AChE in growth and development of insect larvae and demonstrate that siRNA can be readily taken up by insect larvae with their diet.

Acetylcholinesterase in the sea urchin Lytechinus variegatus: characterization and developmental expression in larvae

Acetylcholinesterase (AChE) in the echinoid Lytechinus variegatus has been characterized. Kinetic parameters V(max), K(m), K(ss), and b were 2594+/-1048 nmol ATCh hydrolyzed/min/mg tissue wet weight, 185+/-11 microM, 308+/-100 mM, and 0.2, respectively for the substrate ATCh and 17.8+/-6.87 nmol BTCh hydrolyzed/min/mg tissue wet weight, 654+/-424 microM, 36+/-31 mM, and 0.6, respectively for BTCh. Pharmacologic analyses were performed with four inhibitors of cholinesterases, physostigmine, BW284c51, ethopropazine, and iso-OMPA, and yielded IC(50) values of 106+/-4 nM, 718+/-118 nM, 2.57+/-0.6 mM, and >0.0300 M, respectively. Both kinetic and pharmacologic results confirmed the existence of AChE in larval L. variegatus. Dimeric and tetrameric globular forms (determined by velocity sedimentation on sucrose gradients) were present in L. variegatus larvae. Activity of AChE increased significantly as larvae progressed in development from embryos to eight-arm larvae. Acetylcholinesterase activity of F1 larvae derived from sea urchins collected from wild populations and of F1 larvae derived from sea urchins cultured in the laboratory and fed two different diets suggest that the nutritional and/or environmental history of the adult sea urchin affect the developmental progression of AChE activity in the F1 offspring.