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NMR structure and function of Helicoverpa armigera sterol carrier protein-2, an important insecticidal target from the cotton bollworm.

ABSTRACT: The cotton bollworm, Helicoverpa armigera, has developed strong resistance to many insecticides. Sterol Carrier Protein-2 (SCP-2) is an important non-specific lipid transfer protein in insects and appears to be a potential new target. In order to elucidate the structure and function of Helicoverpa armigera SCP-2 (HaSCP-2), NMR spectroscopy, docking simulations, mutagenesis and bioassays were performed. HaSCP-2 composed of five ?-helices and four stranded ?-sheets. The folds of ?-helices and ?-sheets interacted together to form a hydrophobic cavity with putative entrance and exit openings, which served as a tunnel for accommodating and transporting of lipids. Several sterols and fatty acids could interact with HaSCP-2 via important hydrophobic sites, which could be potential targets for insecticides. Mutagenesis experiments indicated Y51, F53, F89, F110, I117 and Q131 may be the key functional sites. HaSCP-2 showed high cholesterol binding activity and SCP-2 inhibitors (SCPIs) could inhibit the biological activity of HaSCP-2. SCPI-treated larvae at young stage showed a significant decrease of cholesterol uptake in vivo. Our study describes for the first time a NMR structure of SCP-2 in lepidopteran H. armigera and reveals its important function in cholesterol uptake, which facilitates the screening of effective insecticides targeting the insect cholesterol metabolism.

SUBMITTER: Ma H

PROVIDER: S-EPMC4674756 | biostudies-literature | 2015 Dec

REPOSITORIES: biostudies-literature

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NMR structure and function of Helicoverpa armigera sterol carrier protein-2, an important insecticidal target from the cotton bollworm.

Ma Haihao H Ma Yuemin Y Liu Xuehui X Dyer David H DH Xu Pingyong P Liu Kaiyu K Lan Que Q Hong Huazhu H Peng Jianxin J Peng Rong R

Scientific reports 20151210

The cotton bollworm, Helicoverpa armigera, has developed strong resistance to many insecticides. Sterol Carrier Protein-2 (SCP-2) is an important non-specific lipid transfer protein in insects and appears to be a potential new target. In order to elucidate the structure and function of Helicoverpa armigera SCP-2 (HaSCP-2), NMR spectroscopy, docking simulations, mutagenesis and bioassays were performed. HaSCP-2 composed of five α-helices and four stranded β-sheets. The folds of α-helices and β-sh ...[more]

PMID: 26655641

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Project description:BACKGROUND: Chemosensory receptors including olfactory receptors (ORs), gustatory receptors (GRs) and ionotropic receptors (IRs) play a central role in sensing chemical signals and guiding insect behaviours, and are potential target genes in insect pest control. The cotton bollworm Helicoverpa armigera is one of the most destructive pest species that can feed on over 200 different plant species. This diversity of host plants is likely linked to a complex chemosensory system. Here we built on previous work to characterize crucial chemosensory tissues linked to environmental interactions including larval antennae, larval mouthparts and larval fat bodies, as well as male and female adult heads, male and female adult tarsi, and female abdomens. RESULTS: Using transcriptome sequencing, Trinity RNA-seq assemblies and extensive manual curation, we identified a total of 91 candidate chemosensory receptors (60 candidate ORs, 10 GRs and 21 IRs). Thirty-five of these candidates present full-length transcripts. First, we performed in silico differential expression analysis on different sequenced tissues. Further, we created extensive expression profiles using reverse transcription (RT)-PCR on a variety of adult and larval stages. We found that the expression profile of HarmOR51 was limited to adult male antenna suggesting a role in mating that was further supported by a phylogenetic analysis clustering it into the pheromone receptor clade. HarmOR51 in calcium imaging analysis did not show responses to either of the two H. armigera sex pheromone components (Z9-16:Ald or Z11-16:Ald) inviting a future detailed study. In addition, we found four novel HarmORs (OR1, 53, 54 and 58) that appeared to be larvae-antennal specific. Finally, our expression profiling showed that four "divergent" HarmIRs (IR2, 7d.1, 7d.2 and 7d.3) were expressed in both adult and larval antennae, suggesting a functional divergence from their Drosophila homologues. CONCLUSIONS: This study explored three chemoreceptor superfamily genes using a curated transcriptomic approach coupled with extensive expression profiling and a more limited functional characterization. Our results have now provided an extensive resource for investigating the chemoreceptor complement of this insect pest, and meanwhile allow for targeted experiments to identify potential molecular targets for pest control and to investigate insect-plant interactions.

Dataset Information

NMR structure and function of Helicoverpa armigera sterol carrier protein-2, an important insecticidal target from the cotton bollworm.

Publications

NMR structure and function of Helicoverpa armigera sterol carrier protein-2, an important insecticidal target from the cotton bollworm.

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