Immune activation upregulates lysozyme gene expression in Aedes aegypti mosquito cell culture

After stimulation with heat-killed bacteria, cultured cells from the mosqui to Aedes aegypti (Aag-2 cells) secreted an induced protein with a mass of a pproximate to 16 kDa that cross-reacted with antibody to chicken egg lysozy me. To investigate whether lysozyme messenger RNA is induced in bacteria-tr eated cells, we used polymerase chain reaction-based approaches to obtain t he complete lysozyme cDNA from Aag-2 cells. The deduced protein contained 1 48 amino acids, including a 23 amino acid signal sequence. The calculated m ass of the precursor protein is 16 965 Da, which is processed to yield a ma ture lysozyme of 14 471 Da with a calculated pI of 10.1. The lysozyme from Ae. aegypti shared 50% amino acid identity with lysozymes from Anopheles ga mbiae and Anopheles darlingi, which in turn shared 70% identity between eac h other. Northern analysis with the lysozyme cDNA probe showed induction of a 1.3 kb messenger RNA during the first 3 h after treatment of Aag-2 cells with heat-killed bacteria, followed by maximal expression 12-36 h after tr eatment. Southern analysis suggested that the gene likely occurs as a singl e copy in the genome of Aag-2 cells.