Drosophila immune effectors

MASS SPECTROMETRY, A USEFUL TOOL IN THE DISCOVERY AND CHARACTERIZATION OF DROSOPHILA IMMUNE EFFECTORS... 

Key Words Invertebrate immunity antimicrobial peptides immune effectors mass spectrometry drug discovery Drosophila arthropods peptide purification molecular mass fingerprints bioactive peptides. 

The variety of MS-based approaches [see Fig. (1) and Fig. (2) for a general view of the strategies] that have been used to discover, identify and elucidate effectors of the Drosophila immune defense reactions is presently reviewed.Regardless of the approach, MS allowed the discovery and structural characterization of an unprecedented number of systemic immune effectors, as well as the detection of such effectors within tissues expressing a local immune response. 

Fig. (1). Peptidomics strategies used to study Drosophila immunity. (A) Using antimicrobial assays (antibacterial and antifungal), the bioactive peptides were isolated from the blood of bacteria-challenged Drosophila. MS was used for molecular mass assignment, to identify post-translational modifications, and for primary structure elucidation (B) Identification of peptidic immune effectors through differential display analysis (DD) by MALDI-MS and micro/nano RP-HPLC coupled (online) or not (off-line) to ESI-MS. When the HPLC was performed off-line to the mass spectrometer, fractions were individually analyzed by MALDI-MS. The identification and the structural characterization were performed either by molecular mass assignment and/or sequencing by ESI-MS/MS.

The efficacy of MS to characterize effectors of Drosophila immunity and Phormia (also referred in the literature as Protophormia) terranovae is illustrated by several examples. This will not follow a chronological order but is in accordance with the complexity of the MS analyses. MS allowed (i) to define precise molecular masses, to identify post-translational modifications (N-terminal cyclisation, C-terminal amidation, disulfide bonds array, glycosylation), (ii) to determine primary structures of immune peptides (sequencing by MS/MS), (iii) to have mass fingerprints and to identify peptide effectors that are part of Drosophila immunity (molecular mass differential display by MALDI-MS),... 

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