A 104 kDa Aedes aegypti aminopeptidase N is a putative receptor for the Cry11Aa toxin from Bacillus thuringiensis subsp. israelensis

Abstract

The Cry11Aa protein produced in Bacillus thuringiensis subsp. israelensis, a bacterial strain used worldwide for the control of Aedes aegypti larvae, binds midgut brush border membrane vesicles (BBMV) with an apparent Kd of 29.8 nM. Previously an aminopeptidase N (APN), named AaeAPN2, was identified as a putative Cry11Aa toxin binding protein by pull-down assays using biotinylated Cry11Aa toxin (Chen et al., (2009) Insect Biochem Mol Biol., 39: 688–696). Here we show this protein localizes to the apical membrane of epithelial cells in proximal and distal regions of larval caeca. The AaeAPN2 protein binds Cry11Aa with high affinity, 8.6 nM. The full-length and fragments of AaeAPN2 were cloned and expressed in Escherichia coli. The toxin-binding region was identified and further competitive assays demonstrated that Cry11Aa binding to BBMV was efficiently competed by the full-length AaeAPN2 and the fragments of AaeAPN2b and AaeAPN2e. In bioassays against Ae. aegypti larvae, the presence of full-length and a partial fragment (AaeAPN2b) of AaeAPN2 enhanced Cry11Aa larval mortality. Taken together, we conclude that AaeAPN2 is a binding protein and plays a role in Cry11Aa toxicity.

A Spodoptera exigua Cadherin Serves as a Putative Receptor for Bacillus thuringiensis Cry1Ca Toxin and Shows Differential Enhancement of Cry1Ca and Cry1Ac Toxicity

“…Similarly, cadherins in seven lepidopteran, two dipteran, and two coleopteran species have been confirmed or suggested to be receptors for other Cry toxins (2,(12)(13)(14)(15)(16).…”

“…Until now, insect cadherins have been proven or suggested to interact with Cry toxins in at least six lepidopteran (2), two dipteran (12)(13)(14), and two coleopteran (15,16) species. A toxin-binding cadherin receptor is composed of five domains: signal peptide (SP), 8 to 12 cadherin repeats (CRs), membrane-proximal extracellular domain (MPED), transmembrane region (TM), and internal cytoplasmic domain (IC) (17).…”

Sodium Solute Symporter and Cadherin Proteins Act as Bacillus thuringiensis Cry3Ba Toxin Functional Receptors in Tribolium castaneum

“…Functional studies have turned midgut CAD-like proteins into one of the most likely Cry toxin receptor molecules in lepidopteran, dipteran, and coleopteran larvae (7,12,38). It has been proposed that they play the role of the first receptor of Cry toxins, binding toxin monomer and facilitating further processing required for the prepore oligomer formation (17).…”

Cry4aa and Cry4ba From Bacillus Thuringiensis Subsp. Israelensis Expressed in Insect Cells by Recombinant Baculoviruses Are Toxic to Aedes Aegypti Larvae

“…Although Cry toxins share a similar mechanism of action, different Cry-binding molecules (receptors), such as cadherin Chen et al, 2009), aminopeptidase (Abdullah et al, 2006;Zhang et al, 2008), alkaline phosphatase (Fernandez et al, 2006) and α-amylase (Fernandez-Luna et al, 2010) have been identified in mosquito species. A previous work (Beltrão & Silva-Filha, 2006) has shown that Cry toxins may share a class of binding sites when competition assays were carried out.…”