Tweedle cuticular protein BmCPT1 is involved in innate immunity by participating in recognition of Escherichia coli

Bombyx mon, a lepidopteran insect, is one of the earliest models for pattern recognition of Gram-negative bacteria, which may induce the IMD pathway for production of antibacterial peptides. So far, several recognition proteins have been reported in B. mori. However, the connection between pattern recognition of Gram negative bacteria and activation of BmRelishl, a transcription factor controlled by the (MD pathway remains largely unknown. In the present study, we identify BmCPT1, a cuticle protein bearing a Tweedle domain. Its gene expression is co-regulated by NF-kappaB and juvenile hormone signals. BmCPT1 is induced by Escherichia coli in fat bodies and hemocytes, but is constitutively expressed in the epidermis. In vitro binding assays indicate that BmCFT1 protein recognizes and binds to E coli peptidoglycan. Post-transcriptionally modified BmCF71 in the hemolymph binds to E. coli cells through interactions with peptidoglycan recognition protein-5 (BmPGRP5) and lipopolysaccharide binding protein (BmLBP). Transgenic overexpression of BmCFT1 causes the upregulated expression of BmRelish I and clear induction of two gloverin genes. Therefore. BmCPT1 may work along with BmPGRP-S5 and BmLBP to recognize E. coli in the hemolymph and indirectly activate BmRelishl to induce antimicrobial peptide synthesis. (C) 2014 Published by Elsevier Ltd.