Role of receptor interaction in the mode of action of insecticidal Cry and Cyt toxins produced by Bacillus thuringiensis

Gómez, Isabel; Pardo-López, Liliana; Muñóz-Garay, Carlos; Fernández, Luisa Elena; Pérez, Cirilo; Sánchez, Jorge; Soberón, Mário; Bravo, Alejandra

doi:10.1016/j.peptides.2006.06.013

Cited by 102 publications

(84 citation statements)

References 38 publications

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“…Current theories of the mode of action of the Cry1Ac suggest that the toxin binds to GPIanchored proteins prior to insertion into the membrane but it is unclear whether the anchor has any role in that binding Gómez et al, 2007;Pigott and Ellar, 2007). In at least one case the GPI-anchor is not required for binding since an APN from M. sexta was still able to bind Cry1Ac after cleavage of its anchor (Lu and Adang, 1996), however, that particular APN (from class I) has the C-terminal, mucin-like sequence with demonstrated GalNAc content (Knight et al, 2004).…”

Section: Discussionmentioning

confidence: 99%

“…Further binding investigations for both the cadherin-like and GPI-anchored proteins have led to proposals that both protein groups interact with Cry toxins to form pores. Models were suggested where binding commences with the cadherin, and after some toxin modification, binding to GPI-anchored receptors follows, with Nacetylgalactosamine (GalNAc) moieties regarded as essential for the binding of Cry1Ac to GPI-anchored proteins and in the formation of pores Gómez et al, 2007;Jurat-Fuentes and Adang, 2006). GalNAc inhibited 68% of binding to posterior midgut brush border membrane vesicles (BBMVs) from H. armigera but had only slight effect on the binding of Cry1Ac to anterior midgut BBMVs (Rodrigo-Simón et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

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Diversity of aminopeptidases, derived from four lepidopteran gene duplications, and polycalins expressed in the midgut of Helicoverpa armigera: Identification of proteins binding the δ-endotoxin, Cry1Ac of Bacillus thuringiensis

Angelucci

Barrett-Wilt²,

Hunt

et al. 2008

Insect Biochemistry and Molecular Biology

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Helicoverpa armigera midgut proteins that bind the Bacillus thuringiensis (Bt) δ-endotoxin Cry1Ac were purified by affinity chromatography. SDS-PAGE showed that several proteins were eluted with N-acetylgalactosamine and no further proteins were detected after elution with urea. Tandem mass spectral data for tryptic peptides initially indicated that the proteins resembled aminopeptidases (APNs) from other lepidopterans and cDNA sequences for seven APNs were isolated from H. armigera through a combination of cloning with primers derived from predicted peptide sequences and established EST libraries. Phylogenetic analysis showed lepidopteran APN genes in nine clades of which five were part of a lepidopteran-specific radiation. The Cry1Ac-binding proteins were then identified with four of the seven HaAPN genes. Three of those four APNs are likely orthologs of APNs characterised as Cry1Ac-binding proteins in other lepidopterans. The fourth Cry1Ac-binding APN has orthologs not previously identified as Cry1Ac-binding partners. The HaAPN genes were expressed predominantly in the midgut through larval development. Each showed consistent expression along the length of the midgut but five of the genes were expressed at levels about two orders of magnitude greater than the remaining two. The remaining mass spectral data identified sequences encoding polycalin proteins with multiple lipocalin-like domains. A polycalin has only been previously reported in another lepidopteran, Bombyx mori, but polycalins in both species are now linked with binding of Bt Cry toxins. This is the first report of hybrid, lipocalin-like domains in shorter polycalin sequences that are not present in the longest sequence. We propose that these hybrid domains are generated by alternative splicing of the mRNA.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Diversity of aminopeptidases, derived from four lepidopteran gene duplications, and polycalins expressed in the midgut of Helicoverpa armigera: Identification of proteins binding the δ-endotoxin, Cry1Ac of Bacillus thuringiensis

Angelucci

Barrett-Wilt²,

Hunt

et al. 2008

Insect Biochemistry and Molecular Biology

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“…For several Cry toxins, it has been shown that the activated toxins bind to specific receptors lining the apical brush-border membranes of midgut epithelial cells and possibly undergo conformational changes and oligomerisation (Pigott MMBR 2007) [9] (Gómez Peptides 2007) [10]. One widely accepted hypothesis is that this is followed by membrane insertion and pore formation, causing a net influx of ions and water that leads to osmotic cell lysis, resulting in severe damage of the midgut and eventual death of the insect larvae (Knowles AIP 1994) [11] (Whalon AIBP 2003) [12].…”

Section: Introduction: Protein-based Bioinsec-ticidesmentioning

confidence: 99%

Mosquito Resistance to Bacterial Larvicidal Toxins

Wirth¹

2013

TOTNJ

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Abstract:The insecticidal character of the three-domain Cry -endotoxins produced by Bacillus thuringiensis during sporulation is believed to be caused by their capability to generate lytic pores in the target larval midgut cell membranes. This review describes toxic mechanisms with emphasis on the structural basis of pore formation by two closely related dipteran-specific toxins, Cry4Aa and Cry4Ba, which are highly toxic to mosquito larvae. One proposed toxic mechanism via an "umbrella-like" structure involves membrane penetration and pore formation by the 4-5 transmembrane hairpin. The lipid-induced -conformation of 7 could possibly serve as a lipid anchor required for an efficient insertion of the pore-forming hairpin into the bilayer membrane. Though current electron crystallographic data are still inadequate to provide such critical insights into the structural details of the Cry toxin-induced pore architecture, this pivotal evidence clearly reveals that the 65-kDa active toxin in association with the lipid membrane could exist in at least two different trimeric conformations, implying the closed and open states of a functional pore.

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“…Cry1A monomers then bind to the primary receptor that has been identified in several species as a cadherin protein that is located in the microvilli of columnar midgut cells. This interaction provokes a conformational change of the toxin that facilitates further proteolytic cleavage of the domain I N-terminal helix ␣-1, resulting in toxin oligomerization (14,15). In favor of this model, engineered modified Cry1Ab and Cry1Ac toxins lacking helix ␣-1 have been shown to retain toxicity to resistant insects that have mutations affecting the cadherin gene (16).…”

mentioning

confidence: 99%

Role of Alkaline Phosphatase from Manduca sexta in the Mechanism of Action of Bacillus thuringiensis Cry1Ab Toxin

Arenas

Bravo

Soberón

et al. 2010

Journal of Biological Chemistry

153

157

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Cry toxins produced by Bacillus thuringiensis have been recognized as pore-forming toxins whose primary action is to lyse midgut epithelial cells in their target insect. In the case of the Cry1A toxins, a prepore oligomeric intermediate is formed after interaction with cadherin receptor. The Cry1A oligomer then interacts with glycosylphosphatidylinositol-anchored receptors. Two Manduca sexta glycosylphosphatidylinositol-anchored proteins, aminopeptidase (APN) and alkaline phosphatase (ALP), have been shown to bind Cry1Ab, although their role in toxicity remains to be determined. Detection of Cry1Ab binding proteins by ligand blot assay revealed that ALP is preferentially expressed earlier during insect development, because it was found in the first larval instars, whereas APN is induced later after the third larval instar. The binding of Cry1Ab oligomer to pure preparations of APN and ALP showed that this toxin structure interacts with both receptors with high affinity (apparent K d ‫؍‬ 0.6 nM), whereas the monomer showed weaker binding (apparent K d ‫؍‬ 101.6 and 267.3 nM for APN and ALP, respectively). Several Cry1Ab nontoxic mutants located in the exposed loop 2 of domain II or in ␤-16 of domain III were affected in binding to APN and ALP, depending on their oligomeric state. In particular monomers of the nontoxic domain III, the L511A mutant did not bind ALP but retained APN binding, suggesting that initial interaction with ALP is critical for toxicity. Our data suggest that APN and ALP fulfill two roles. First APN and ALP are initial receptors promoting the localization of toxin monomers in the midgut microvilli before interaction with cadherin. Then APN and ALP function as secondary receptors mediating oligomer insertion into the membrane. However, the expression pattern of these receptors and the phenotype of L511A mutant suggest that ALP may have a predominant role in toxin action because Cry toxins are highly effective against the neonate larvae that is the target for pest control programs.The Cry toxins produced by Bacillus thuringiensis are used worldwide as effective biological control agents for many species of insects including agricultural and forest pests and several vectors of human and animal diseases. Its insecticidal property results from crystalline inclusions produced during sporulation that are formed by ␦-endotoxins known as Cry toxins (1).The Cry protein family is composed of more than 54 groups, among which the three-domain Cry family forms the major group, having members that show toxicity to different insect orders and to nematodes. The crystal structure has been solved for six three-domain Cry toxins and one protoxin that display different insect specificities (2). The activated Cry toxins are globular molecules consisting of a bundle of seven ␣-helices (domain I), a three-␤-sheet prism (domain II), and a ␤-sandwich (domain III) (3, 4). The N-terminal domain I is involved in oligomer formation, membrane insertion, and pore formation (5-8). Domain II and III are involved in the recogn...

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Role of receptor interaction in the mode of action of insecticidal Cry and Cyt toxins produced by Bacillus thuringiensis

Cited by 102 publications

References 38 publications

Diversity of aminopeptidases, derived from four lepidopteran gene duplications, and polycalins expressed in the midgut of Helicoverpa armigera: Identification of proteins binding the δ-endotoxin, Cry1Ac of Bacillus thuringiensis

Diversity of aminopeptidases, derived from four lepidopteran gene duplications, and polycalins expressed in the midgut of Helicoverpa armigera: Identification of proteins binding the δ-endotoxin, Cry1Ac of Bacillus thuringiensis

Mosquito Resistance to Bacterial Larvicidal Toxins

Role of Alkaline Phosphatase from Manduca sexta in the Mechanism of Action of Bacillus thuringiensis Cry1Ab Toxin

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