DIFFERENTIAL DISPLAY OF PEPTIDES INDUCED DURING THE IMMUNE-RESPONSE OF DROSOPHILA - A MATRIX-ASSISTED LASER-DESORPTION IONIZATION TIME-OF-FLIGHT MASS-SPECTROMETRY STUDY

We have developed an approach based on a differential mass spectrometr ic analysis to detect molecules induced during the immune response of Drosophila, regardless of their biological activities. For this, ne ha ve applied directly matrix-assisted laser desorption/ionization MS to hemolymph samples from individual flies before and after an immune cha llenge. This method provided precise information on the molecular mass es of immune-induced molecules and allowed the detection, in the molec ular range of 1.5-11 kDa, of 24 Drosophila immune-induced molecules (D IMs). These molecules are all peptides, and four correspond to already characterized antimicrobial peptides, We have further analyzed the in duction of the various peptides by immune challenge in wild-type flies and in mutants with a compromised antimicrobial response. We also des cribe a methodology combining matrix-assisted laser desorption ionizat ion time-of-flight RIS, HPLC, and Edman degradation, which yielded the peptide sequence of three of the DIMs. Finally, molecular cloning and Northern blot analyses revealed that one of the DIMs is produced as a prepropeptide and is inducible on a bacterial challenge.