Expression of a cysteine proteinase inhibitor gene in silkworm Bombyx mori following Trypanosoma brucei brucei challenge

Abstract

A microarray-based gene expression analysis was carried out to identify Trypanosoma-inducible genes in the silkworm Bombyx mori. A Bombyx cysteine proteinase inhibitor (BCPI) gene was upregulated following Trypanosoma brucei brucei GUTat3.1 injection. The BCPI was shown to encode 105 amino acids and putative signal peptide sequences were found. The expression profiles of parasite-inducible transcripts were confirmed by real-time quantitative polymerase chain reaction. BCPI is expressed specifically in the fat body and hemocytes following T. b. brucei challenge. The expression level of BCPI increased significantly 3 h after the parasite injection. A homology search showed that BCPI contains a region homologous to the propeptide sequence of cysteine proteinase from protozoan parasite species including T. b. brucei and T. congolense. BCPI possesses the conserved motif (Gly-X-Asn-X-Phe-X-Asp) and these residues might be capable of inhibiting the corresponding enzymes. Therefore, BCPI may play an important role in defense mechanisms against invading protozoan parasites. These results suggest that BCPI would be a good candidate for use in development of peptidyl inhibitors against cysteine proteinases in trypanosomal species.