★ Glycosyl–phosphatidyl–inositol (GPI)-anchored proteins are involved in binding of Bacillus thuringiensis Cry3Aa to Tenebrio molitor brush border membranes. ★ A T. molitor GPI-anchored alkaline phosphatase ALP binds Cry3Aa toxin. ★ The GPI-anchored ALP was preferentially expressed in T. molitor early instar larvae in comparison to late instar larvae. ★ GPI-anchored ALP are involved in the mode of action of B. thuringiensis Cry toxins in three different insect orders.
Bacillus thuringiensis Cry toxins recognizes their target cells in part by the binding to glycosyl–phosphatidyl–inositol (GPI) anchored proteins such as aminopeptidase-N (APN) or alkaline phosphatases (ALP). Treatment of Tenebrio molitor brush border membrane vesicles (BBMV) with phospholipase C that cleaves out GPI-anchored proteins from the membranes, showed that GPI-anchored proteins are involved in binding of Cry3Aa toxin to BBMV. A 68 kDa GPI-anchored ALP was shown to bind Cry3Aa by toxin overlay assays. The 68 kDa GPI-anchored ALP was preferentially expressed in early instar larvae in comparison to late instar larvae. Our work shows for the first time that GPI-anchored ALP is important for Cry3Aa binding to T. molitor BBMV suggesting that the mode of action of Cry toxins is conserved in different insect orders.