The orthologue to the Cpm1/Cqm1 receptor in Aedes aegypti is expressed as a midgut GPI-anchored α-glucosidase, which does not bind to the insecticidal binary toxin.
Aedes aegypti larvae are refractory to the insecticidal binary (Bin) toxin from Bacillus sphaericus, which is not able to bind to its target tissue in the larval midgut. In contrast, Culex pipiens larvae are highly susceptible to that toxin, which targets its midgut brush border membranes (BBMF) through the binding of the BinB subunit to specific receptors, the Cpm1/Cqm1 membrane-bound α-glucosidases. The identification of an Ae. aegypti gene encoding a Cpm1/Cqm1 orthologue, here named Aam1, led to the major goal of this study which was to investigate its expression. The aam1 transcript was found in larvae and adults from Ae. aegypti and a ≈73-kDa protein was recognized by an anti-Cqm1 antibody in midgut BBMF. The Aam1 protein displayed α-glucosidase activity and localized to the midgut epithelium, bound through a GPI anchor, similarly to Cpm1/Cqm1. However, no binding of native Aam1 was observed to the recombinant BinB subunit. Treatment of both proteins with endoglycosidase led to changes in the molecular weight of Aam1, but not Cqm1, implying that the former was glycosylated. The findings from this work rule out lack of receptors in larval stages, or its expression as soluble proteins, as a reason for Ae. aegypti refractoriness to Bin toxin.
Ferreira
Lígia Maria
LM
Department of Entomology, Centro de Pesquisas Aggeu Magalhães/FIOCRUZ, Av. Moraes Rego s/n, Cidade Universitária, Recife-PE 50670-420, Brazil.
Romão
Tatiany Patrícia
TP
de-Melo-Neto
Osvaldo Pompílio
OP
Silva-Filha
Maria Helena Neves Lobo
MH
D000330:Aedes / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D000818:Animals; D001427:Bacterial Toxins / Q000378:metabolism*; D004064:Digestive System / Q000201:enzymology / Q000378:metabolism; D015870:Gene Expression; D017261:Glycosylphosphatidylinositols / Q000378:metabolism*; D019476:Insect Proteins / Q000235:genetics / Q000378:metabolism*; D007306:Insecticides / Q000378:metabolism*; D007814:Larva / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D011485:Protein Binding; D000520:alpha-Glucosidases / Q000235:genetics / Q000378:metabolism*
D001427:Bacterial Toxins; D017261:Glycosylphosphatidylinositols; D019476:Insect Proteins; D007306:Insecticides; C046134:binB protein, Bacillus sphaericus; D000520:alpha-Glucosidases