Immunolocalization of the vesicular acetylcholine transporter in larval and adult Drosophila neurons

Choline acetyltransferase and vesicular acetylcholine transporter are required for metamorphosis, reproduction, and insecticide susceptibility in Tribolium castaneum

Choline acetyltransferase (ChAT) and vesicular acetylcholine transporter (VAChT) are essential enzymes for synthesizing and transporting acetylcholine (ACh). But their functions in metamorphosis, reproduction, and the insecticide susceptibility were poorly understood in the insects. To address these issues, we identified the orthologues of chat and vacht in Tribolium castaneum. Spatiotemporal expression profiling showed Chat has the highest expression at the early adult stage, while vacht shows peak expression at the early larval stage. Both of them were highly expressed at the head of late adult. RNA interference (RNAi) of chat and vacht both led to a decrease in ACh content at the late larval stage. It is observed that chat knockdown severely affected larval development and pupal eclosion, but vacht RNAi only disrupted pupal eclosion. Further, parental RNAi of chat or vacht led to 35 % or 30 % reduction in fecundity, respectively, and knockdown of them completely inhibited egg hatchability. Further analysis has confirmed that both the reduction in fecundity and hatchability caused through the maternal specificity in T. castaneum. Moreover, the transcript levels of chat and vacht were elevated after carbofuran or dichlorvos treatment. Reduction of chat or vacht decreased the resistance to carbofuran and dichlorvos. This study provides the evidence for chat and vacht not only involved in development and reproduction of insects but also could as the potential targets of insecticides.

Role of Bmal1 in mediating the cholinergic system to regulate the behavioral rhythm of nocturnal marine molluscs

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The circadian differential expression of AchE was identified using TMT quantitative proteomics;

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It was found that the Ach concentration and the expression levels of AchE and Bmal1 exhibit circadian cosine rhythm;

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The full-length sequences of AchE and nAchR were obtained by cloning technique and made available for phylogenetic analysis;

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The movement distance and duration of abalone increased after the injection of neostigmine methylsulfate as the AchE inhibitor;

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Bmal1 as the core circadian clock gene was proven to bind to AchE and nAchR, thereby regulating the movement behavior of abalone.

The circadian rhythm is one of the most general and important rhythms in biological organisms. In this study, continuous 24-h video recordings showed that the cumulative movement distance and duration of the abalone, Haliotis discus hannai, reached their maximum values between 20:00–00:00, but both were significantly lower between 08:00–12:00 than at any other time of day or night (P < 0.05). To investigate the causes of these diel differences in abalone movement behavior, their cerebral ganglia were harvested at 00:00 (group D) and 12:00 (group L) to screen for differentially expressed proteins using tandem mass tagging (TMT) quantitative proteomics. Seventy-five significantly different proteins were identified in group D vs. group L. The differences in acetylcholinesterase (AchE) expression levels between day- and nighttime and the key role in the cholinergic nervous system received particular attention during the investigation. A cosine rhythm analysis found that the concentration of acetylcholine (Ach) and the expression levels of AchE tended to be low during the day and high at night, and high during the day and low at night, respectively. However, the rhythmicity of the diel expression levels of acetylcholine receptor (nAchR) appeared to be insignificant (P > 0.05). Following the injection of three different concentrations of neostigmine methylsulfate, as an AchE inhibitor, the concentration of Ach in the hemolymph, and the expression levels of nAchR in the cerebral ganglia increased significantly (P < 0.05). Four hours after drug injection, the cumulative movement distance and duration of abalones were significantly higher than those in the uninjected control group, and the group injected with saline (P < 0.05). The expression levels of the core diurnal clock Bmal1 over a 24-h period also tended to be high during the day and low at night. First, a co-immunoprecipitation assay demonstrated the binding between Bmal1 and AchE or nAchR. A dual-luciferase gene test and electrophoretic mobility shift assay showed that Bmal1 bound to the promoter regions of AchE and nAchR. Twenty-four hours after silencing the Bmal1 gene, the expression levels of AchE and nAchR decreased significantly compared to those of the dsEGFP and PBS control groups, further showing that Bmal1 mediates the cholinergic system to regulate the behavioral rhythm of abalone. These findings shed light on the endocrine mechanism regulating the rhythmic behavior of abalone, and provide a reference for understanding the life history adaptation strategies of nocturnal organisms and the proliferation and protection of bottom dwelling economically important organisms.

Vesicular neurotransmitter transporters in Drosophila melanogaster

Drosophila melanogaster express vesicular transporters for the storage of neurotransmitters acetylcholine, biogenic amines, GABA, and glutamate. The large array of powerful molecular-genetic tools available in Drosophila enhances the use of this model organism for studying transporter function and regulation.

Evidence for the cholinergic markers ChAT and vAChT in sensory cells of the developing antennal nervous system of the desert locust Schistocerca gregaria

Sensory and motor systems in insects with hemimetabolous development must be ready to mediate adaptive behavior directly on hatching from the egg. For the desert locust S. gregaria, cholinergic transmission from antennal sensillae to olfactory or mechanosensory centers in the brain requires that choline acetyltransferase (ChAT) and the vesicular acetylcholine transporter (vAChT) already be present in sensory cells in the first instar. In this study, we used immunolabeling to demonstrate that ChAT and vAChT are both expressed in sensory cells from identifiable sensilla types in the immature antennal nervous system. We observed ChAT expression in dendrites, neurites and somata of putative basiconic-type sensillae at the first instar stage. We also detected vAChT in the sensory axons of these sensillae in a major antennal nerve tract. We then examined whether evidence for cholinergic transmission is present during embryogenesis. Immunolabeling confirms that vAChT is expressed in somata typical of campaniform sensillae, as well as in small sensory cell clusters typically associated with either a large basiconic or coeloconic sensilla, at 99% of embryogenesis. The vAChT is also expressed in the somata of these sensilla types in multiple antennal regions at 90% of embryogenesis, but not at earlier (70%) embryonic stages. Neuromodulators are known to appear late in embryogenesis in neurons of the locust central complex, and the cholinergic system of the antenna may also only reach maturity shortly before hatching.

Overexpression of the vesicular acetylcholine transporter disrupts cognitive performance and causes age-dependent locomotion decline in Drosophila

Acetylcholinergic (ACh) neurotransmission is essential for key organismal functions such as locomotion and cognition. However, the mechanism through which ACh is regulated in the central nervous system is not fully understood. The vesicular acetylcholine transporter (VAChT) mediates the packaging and transport of ACh for exocytotic release and is a critical component of the ACh release machinery. Yet its precise role in the maintenance of cholinergic tone remains a subject of active investigation. Here we use the overexpression of VAChT as a tool to investigate the role of changes in ACh exocytosis on the regulation of synaptic activity and its downstream consequences. We measured the effect of an increase in VAChT expression on locomotion and cognitive performance as well as on organismal survival across the lifespan. We report the surprising finding that increased VAChT expression results in a significantly shorter lifespan in comparison to control flies. Moreover, constructs overexpressing VAChT demonstrate an age-dependent decrease in locomotion performance. Importantly, we report clear deficits in learning and memory which we measured through a courtship conditioning assay. Together, these data provide evidence for the adverse effects of overexpression of the vesicular acetylcholine transporter in the maintenance of normal behavioral abilities in Drosophila and demonstrates for the first time a role for ACh in the regulation of organismal survival.

Data on the specificity of an antibody to Drosophila vesicular acetylcholine transporter

The role of the vesicular acetylcholine transporter (VAChT) in the regulation of cholinergic neurotransmission has not been fully elucidated. Here we sought to develop a tool for studying vesicular acetylcholine transporter function, and we present data on the validation of our new anti-VAChT antibody. We show that the immunoreactivity of the antibody is not due to an artifact of secondary antibody staining, and we present two additional validation data. First, the peptide epitope used to generate the antibody is able to block the binding of the anti-VAChT antibody in vivo. Further, RNA interference (RNAi) -mediated knockdown of VAChT function in cholinergic neurons drastically reduces anti-VAChT staining in those constructs. Additional evidence for the antibody functionality is presented in our research article on the subject (Boppana et al., 2017) [1].