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Barbosa RC, Godoy RSM, Ferreira PG, Mendes TAO, Ramalho-Ortigão M, Ribeiro JMC, Martins GF. Exploring the midgut physiology of the non-haematophagous mosquito Toxorhynchites theobaldi. Open Biol 2024; 14:230437. [PMID: 38955221 DOI: 10.1098/rsob.230437] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Accepted: 06/11/2024] [Indexed: 07/04/2024] Open
Abstract
Toxorhynchites mosquitoes have an exclusively phytophagous feeding habit as adults, which leads to significant differences in their morphophysiology compared with haematophagous mosquitoes. However, the molecular mechanisms of digestion in this mosquito are not well understood. In this study, RNA sequencing of the posterior midgut (PMG) of the mosquito Toxorhynchites theobaldi was undertaken, highlighting its significance in mosquito digestion. Subsequently, a comparison was made between the differential gene expression of the PMG and that of the anterior midgut. It was found that the most abundant proteases in the PMG were trypsin and chymotrypsin, and the level of gene expression for enzymes essential for digestion (such as serine protease, α-amylase and pancreatic triacylglycerol lipase) and innate immune response (including catalase, cecropin-A2 and superoxide dismutase) was like that of haematophagous mosquitoes. Peritrophin-1 was detected in the entire midgut, with an elevated expression level in the PMG. Based on our findings, it is hypothesized that a non-haematophagic habit might have been exhibited by the ancestor of Tx. theobaldi, and this trait may have been retained. This study represents a pioneering investigation at the molecular level of midgut contents in a non-haematophagous mosquito. The findings offer valuable insights into the evolutionary aspects of feeding habits in culicids.
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Affiliation(s)
- Renata C Barbosa
- Departamento de Biologia Geral, Universidade Federal de Viçosa, Viçosa, Minas Gerais 36570-900, Brazil
| | - Raquel S M Godoy
- Fundação Oswaldo Cruz, Instituto René Rachou, Fiocruz, Belo Horizonte, Minas Gerais 30190-002, Brazil
| | - Priscila G Ferreira
- Departamento de Bioquímica e Biologia Molecular, Universidade Federal de Viçosa, Viçosa, Minas Gerais 50670-900, Brazil
| | - Tiago A O Mendes
- Departamento de Bioquímica e Biologia Molecular, Universidade Federal de Viçosa, Viçosa, Minas Gerais 50670-900, Brazil
| | | | - José M C Ribeiro
- Section of Vector Biology, Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, Rockville, MD 20852, USA
| | - Gustavo F Martins
- Departamento de Biologia Geral, Universidade Federal de Viçosa, Viçosa, Minas Gerais 36570-900, Brazil
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Best HL, Williamson LJ, Lipka-Lloyd M, Waller-Evans H, Lloyd-Evans E, Rizkallah PJ, Berry C. The Crystal Structure of Bacillus thuringiensis Tpp80Aa1 and Its Interaction with Galactose-Containing Glycolipids. Toxins (Basel) 2022; 14:863. [PMID: 36548760 PMCID: PMC9784298 DOI: 10.3390/toxins14120863] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2022] [Revised: 11/21/2022] [Accepted: 11/24/2022] [Indexed: 12/13/2022] Open
Abstract
Tpp80Aa1 from Bacillus thuringiensis is a Toxin_10 family protein (Tpp) with reported action against Culex mosquitoes. Here, we demonstrate an expanded target range, showing Tpp80Aa1 is also active against the larvae of Anopheles gambiae and Aedes aegypti mosquitoes. We report the first crystal structure of Tpp80Aa1 at a resolution of 1.8 Å, which shows Tpp80Aa1 consists of two domains: an N-terminal β-trefoil domain resembling a ricin B lectin and a C-terminal putative pore-forming domain sharing structural similarity with the aerolysin family. Similar to other Tpp family members, we observe Tpp80Aa1 binds to the mosquito midgut, specifically the posterior midgut and the gastric caecum. We also identify that Tpp80Aa1 can interact with galactose-containing glycolipids and galactose, and this interaction is critical for exerting full insecticidal action against mosquito target cell lines.
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Affiliation(s)
- Hannah L. Best
- School of Biosciences, Cardiff University, Park Place, Cardiff CF10 3AX, UK
| | | | | | - Helen Waller-Evans
- School of Pharmacy, Cardiff University, Park Place, Cardiff CF10 3AX, UK
| | - Emyr Lloyd-Evans
- School of Biosciences, Cardiff University, Park Place, Cardiff CF10 3AX, UK
| | | | - Colin Berry
- School of Biosciences, Cardiff University, Park Place, Cardiff CF10 3AX, UK
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Sharma M, Kumar V. Mosquito-larvicidal Binary (BinA/B) proteins for mosquito control programs —advancements, challenges, and possibilities. CURRENT RESEARCH IN INSECT SCIENCE 2022; 2:100028. [PMID: 36003274 PMCID: PMC9387486 DOI: 10.1016/j.cris.2021.100028] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Revised: 12/11/2021] [Accepted: 12/14/2021] [Indexed: 11/18/2022]
Abstract
Binary (BinAB) toxin is primarily responsible for the larvicidal action of the WHO recognized mosquito-larvicidal bacterium Lysinibacillus sphaericus. BinAB is a single receptor-specific toxin, active against larvae of Culex and Anopheles, but not Aedes aegypti. The target receptor in Culex is Cqm1 protein, a GPI-anchored amylomaltase located apically in the lipid-rafts of the larval-midgut epithelium. Interaction of the toxin components with the receptor is critical for the larvicidal activity of the toxin. Evidences support the pore formation model for BinAB toxin internalization and the role of toxin-glycan interactions in the endoplasmic reticulum in mediating larval death. Targeted R&D efforts are required to maintain the sustainability and improve efficacy of the eco-friendly BinAB proteins for efficient mosquito control interventions.
The increasing global burden of mosquito-borne diseases require targeted, environmentally friendly, and sustainable approaches for effective vector control without endangering the non-target beneficial insect population. Biological interventions such as biopesticides, Wolbachia-mediated biological controls, or sterile insect techniques are used worldwide. Here we review Binary or BinAB toxin—the mosquito-larvicidal component of WHO-recognized Lysinibacillus sphaericus bacterium employed in mosquito control programs. Binary (BinAB) toxin is primarily responsible for the larvicidal effect of the bacterium. BinAB is a single-receptor-specific toxin and is effective against larvae of Culex and Anopheles, but not against Aedes aegypti. The receptor in Culex, the Cqm1 protein, has been extensively studied. It is a GPI-anchored amylomaltase and is located apically in the lipid rafts of the larval-midgut epithelium. The interaction of the toxin components with the receptor is crucial for the mosquito larvicidal activity of the BinAB toxin. Here we extend support for the pore formation model of BinAB toxin internalization and the role of toxin-glycan interactions in the endoplasmic reticulum in mediating larval death. BinAB is phylogenetically safe for humans, as Cqm1-like protein is not expected in the human proteome. This review aims to initiate targeted R&D efforts, such as applying fusion technologies (chimera of BinA, chemical modification of BinA), for efficient mosquito control interventions. In addition, the review also examines other areas such as bioremediation and cancer therapeutics, in which L. sphaericus is proving useful and showing potential for further development.
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Affiliation(s)
- Mahima Sharma
- Radiation Biology & Health Sciences Division, Bhabha Atomic Research Centre, Mumbai, Maharashtra 400085, India
| | - Vinay Kumar
- Radiation Biology & Health Sciences Division, Bhabha Atomic Research Centre, Mumbai, Maharashtra 400085, India
- Correspondence Author: Professor (Retired) Vinay Kumar, Radiation Biology & Health Sciences Division, Bhabha Atomic Research Centre, Mumbai, Maharashtra 400085, India
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Bacterial Toxins Active against Mosquitoes: Mode of Action and Resistance. Toxins (Basel) 2021; 13:toxins13080523. [PMID: 34437394 PMCID: PMC8402332 DOI: 10.3390/toxins13080523] [Citation(s) in RCA: 45] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Revised: 06/18/2021] [Accepted: 06/19/2021] [Indexed: 12/25/2022] Open
Abstract
Larvicides based on the bacteria Bacillus thuringiensis svar. israelensis (Bti) and Lysinibacillus sphaericus are effective and environmentally safe compounds for the control of dipteran insects of medical importance. They produce crystals that display specific and potent insecticidal activity against larvae. Bti crystals are composed of multiple protoxins: three from the three-domain Cry type family, which bind to different cell receptors in the midgut, and one cytolytic (Cyt1Aa) protoxin that can insert itself into the cell membrane and act as surrogate receptor of the Cry toxins. Together, those toxins display a complex mode of action that shows a low risk of resistance selection. L. sphaericus crystals contain one major binary toxin that display an outstanding persistence in field conditions, which is superior to Bti. However, the action of the Bin toxin based on its interaction with a single receptor is vulnerable for resistance selection in insects. In this review we present the most recent data on the mode of action and synergism of these toxins, resistance issues, and examples of their use worldwide. Data reported in recent years improved our understanding of the mechanism of action of these toxins, showed that their combined use can enhance their activity and counteract resistance, and reinforced their relevance for mosquito control programs in the future years.
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Sharma M, Kumar A, Kumar V. Liposome-Based Study Provides Insight into Cellular Internalization Mechanism of Mosquito-Larvicidal BinAB Toxin. J Membr Biol 2020; 253:331-342. [PMID: 32725430 DOI: 10.1007/s00232-020-00131-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Accepted: 07/14/2020] [Indexed: 12/11/2022]
Abstract
Glycosylphosphatidylinositols (GPIs) anchored proteins are commonly localized onto lipid rafts. These extracellular proteins participate in a variety of cellular functions, including as receptors for viruses and toxins. Intracellular trafficking of World Health Organization recognized mosquito-larvicidal BinAB toxin is mediated via GPI-anchored Cqm1 receptor protein in Culex mosquitoes. We confirmed conformational change in Cqm1 dimer on interaction with BinA/BinB proteins by dynamic light scattering, modelling of hydrodynamic parameters using the atomic structures, and synchrotron Small Angle solution X-ray scattering (SAXS). A reliable model of the receptor-BinB complex was also constructed from joint SAXS/SANS refinement. We confirmed electrostatic interactions of the Cqm1 ectodomain with lipid rafts reconstituted in model membranes and report receptor-dependent impairment of model liposomes by BinA/B proteins. Liposomal disruption was toxin concentration-dependent as monitored by the release of encapsulated carboxyfluorescein dye. Interestingly, BinA alone, without BinB, showed efficient efflux of the fluorescent dye in agreement with the reported high larvicidal activity of BinA variants. The study provides insight into BinA/B toxin internalization mechanism in the membrane model that is toxin internalization is mediated via receptor-dependent pore formation mechanism. It also suggests a tangible and environmentally safe strategy for control of mosquito population.
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Affiliation(s)
- Mahima Sharma
- Radiation Biology & Health Sciences Division, Bhabha Atomic Research Centre, Mumbai, Maharashtra, 400085, India.,, 13th Floor, 247 Park, Vikhroli West, Mumbai, 400079, India
| | - Amit Kumar
- Radiation Biology & Health Sciences Division, Bhabha Atomic Research Centre, Mumbai, Maharashtra, 400085, India
| | - Vinay Kumar
- Radiation Biology & Health Sciences Division, Bhabha Atomic Research Centre, Mumbai, Maharashtra, 400085, India. .,Homi Bhabha National Institute, Training School Complex, Anushaktinagar, Mumbai, Maharashtra, 400094, India.
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Sharma M, Aswal VK, Kumar V, Chidambaram R. Small-angle neutron scattering studies suggest the mechanism of BinAB protein internalization. IUCRJ 2020; 7:166-172. [PMID: 32148845 PMCID: PMC7055391 DOI: 10.1107/s2052252519017159] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/13/2019] [Accepted: 12/23/2019] [Indexed: 06/10/2023]
Abstract
Small-angle neutron scattering (SANS) is one of the most widely used neutron-based approaches to study the solution structure of biological macromolecular systems. The selective deuterium labelling of different protein components of a complex provides a means to probe conformational changes in multiprotein complexes. The Lysinibacillus sphaericus mosquito-larvicidal BinAB proteins exert toxicity through interaction with the receptor Cqm1 protein; however, the nature of the complex is not known. Rationally engineered deuterated BinB (dBinB) protein from the L. sphaericus ISPC-8 species was synthesized using an Escherichia coli-based protein-expression system in M9 medium in D2O for 'contrast-matched' SANS experiments. SANS data were independently analysed by ab initio indirect Fourier transform-based modelling and using crystal structures. These studies confirm the dimeric status of Cqm1 in 100% D2O with a longest intramolecular vector (D max) of ∼94 Å and a radius of gyration (R g) of ∼31 Å. Notably, BinB binds to Cqm1, forming a heterodimeric complex (D max of ∼129 Å and R g of ∼40 Å) and alters its oligomeric status from a dimer to a monomer, as confirmed by matched-out Cqm1-dBinB (D max of ∼70 Å and R g of ∼22 Å). The present study thus provides the first insight into the events involved in the internalization of larvicidal proteins, likely by raft-dependent endocytosis.
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Affiliation(s)
- Mahima Sharma
- Protein Crystallography Section, Radiation Biology & Health Sciences Division, Bhabha Atomic Research Centre, Mumbai 400 085, India
| | - Vinod K. Aswal
- Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085, India
| | - Vinay Kumar
- Protein Crystallography Section, Radiation Biology & Health Sciences Division, Bhabha Atomic Research Centre, Mumbai 400 085, India
| | - R. Chidambaram
- Homi Bhabha Professor, Bhabha Atomic Research Centre, Mumbai 400 085, India
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